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SCI. MAR., 68 (Suppl. 2): 5-438 SCIENTIA MARINA 2004

Fauna of the Mediterranean Hydrozoa*

JEAN BOUILLON1, MARIA DOLORES MEDEL2, FRANCESC PAGÈS3, JOSEP-MARIA GILI3, FERDINANDO BOERO4 and CINZIA GRAVILI4 1 Laboratoire de Biologie Marine, Université Libre de Bruxelles, 50 Ave F. D. Roosevelt, 1050 Bruxelles, Belgium. 2 Departamento de Fisiología y Zoología, Facultad de Biologia, Universidad de Sevilla, Reina Mercedes 6, 410121 Sevilla, Spain. 3 Institut de Ciències del Mar (CSIC) Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia, Spain. 4 Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Stazione di Biologia Marina, Università di Lecce, 73100, Lecce, Italy.

SUMMARY: This study provides a systematic account of the hydrozoan species collected up to now in the Mediterranean Sea. All species are described, illustrated and information on morphology and distribution is given for all of them. This work is the most complete fauna of hydrozoans made in the Mediterranean. The fauna includes planktonic hydromedusae, benth- ic polyps stages and the siphonophores. The Hydrozoa are taken as an example of inconspicuous taxa whose knowledge has greatly progressed in the last decades due to the scientific research of some specialists in the Mediterranean area. The num- ber of species recorded in the Mediterranean almost doubled in the last thirty years and the number of new records is still increasing. The 457 species recorded in this study represents the 12% of the world known species. The fauna is completed with classification keys and a glossary of terms with the main purpose of facilitating the identification of all Meditrranean hydrozoan species. Key words: Hydrozoa, hydromedusae, hydropolyps, siphonophores, taxonomy, systematics, fauna, Mediterranean.

RESUMEN: FAUNA DE HIDROZOOS DEL MEDITERRÁNEO. – Este estudio proporciona una relación sistemática de las especies de hidrozoos conocidas hasta la actualidad en el mar Mediterráneo. Se describen e ilustran todas las especies de las cuales se ofrece información sobre su morfología y distribución. Este trabajo es la fauna mas completa de hidrozoos hecha en el Mediterráneo. Esta fauna incluye las hidromedusas planctónicas, los estadios bentónicos de pólipos y los sifonóforos. Los Hydrozoa se han tomado como un ejemplo de taxones inconspicuos cuyo conocimiento ha progresado enormemente durante las últimas décadas gracias a la investigación de algunos especialistas en el area mediterránea. El número de especies citadas en el Mediterráneo se ha casi doblado en los últimos treinta años y el número de nuevos registros sigue incrementándose. Las 457 especies referenciadas en este estudio representan el 12% del total mundial de especies. La fauna se complementa con claves de clasificación y un glosario de términos con el propósito de facilitar la identificación de todas las especies de hidrozoos del Mediterráneo. Palabras clave: Hydrozoa, hidromedusas, hidropólipos, sifonóforos, taxonomía, sistemática, fauna, Mediterráneo.

INTRODUCTION it covers 2.542.000 Km2, with an average depth close to 1.500 m and a maximal depth of 5.121 m in The Mediterranean framework the Ionian Sea. The Mediterranean Sea is an almost closed basin, connected with the Atlantic Ocean via The Mediterranean Sea is located between the Strait of Gibraltar, with the Red Sea via the Suez Europe, Asia, and Africa. Excluding the Black Sea, Canal, and with the Black Sea via the Bosphorous and the Dardanelles Straits. Surface temperatures *Received June 24, 2004. Accepted July 15, 2004. range between 11-13°C (with extremes of 4-5°C in

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the Gulf of Trieste) in winter and 25-30°C in sum- some relicts of the Tethys Sea (the Indopacific- mer, determining cold temperate to warm-temperate Atlantic connection of ancient times), most Mediter- conditions in the cold season, and tropical condi- ranean species are of Atlantic origin, having entered tions in the warm one. Deep-water temperature is through Gibraltar from either the African or the about 13°C and, normally, this is also the surface European portion of the Atlantic. This made the temperature in winter, when the basin becomes Mediterranean biota an Atlantic province from a homoeothermic. Summer thermoclines divide the biogeographic point of view (Briggs, 1974). The variable surface waters from the more stable, deep alteration of the ice ages and warm interglacial peri- waters. In the Mediterranean, evaporation exceeds ods during the Quaternary resulted in different both direct rainfall and the water input by rivers that, immigration waves of Atlantic fauna of boreal or in general, drain rather arid countries. This balance subtropical origin respectively (Bianchi and Morri, explains the main properties of the sea. Water of rel- 2000). Considering the long and complex Mediter- atively high salinity, an average of 37 psu, is formed ranean history, the present high species richness is by evaporative concentration and, being more probably due to both its evolutionary period through dense, sinks to the bottom and falls across the the Tertiary and the post-Pliocene diversity pump Gibraltar sill into the Atlantic, at a level where from the Atlantic Ocean. Atlantic water has a lower density. The Mediter- Historical reasons are, however, just one side of ranean water pouring into the Atlantic sinks until it the explanation of the rich Mediterranean biodiver- finds equal density, travelling northwards, along the sity, the other side being strictly ecological: season- Portuguese coast. The loss of deep Mediterranean ality is the key for the coexistence of a high number water is over-compensated by a surface Atlantic cur- of species (Coma et al. 2000). The same physical rent entering through Gibraltar Strait. These water space, in fact, can widen its potential for life in exchange sums about 1,900 Km3 per year, whereas another dimension, with the alternation of species in the losses by evaporation could be of 1,300 Km3 per time. year. This Mediterranean-Atlantic balance avoids The availability of proper conditions for both excessive eutrophication (Margalef, 1985): the tropical and temperate species makes the Mediter- Mediterranean loses deep water, relatively rich with ranean a perfect sea for biological invasions (Boero, mineralised or recycled nutrients, and receives low- 2002). Species of cold affinity are thus pre-adapted nutrient surface Atlantic water. to deep-waters and/or winter temperature condi- The present-day situation is the result of a com- tions, whereas species of temperate affinity are pre- plex history. The Mediterranean Sea is a remnant of adapted to surface and/or summer conditions. Most the once extensive Tethys Sea, a wedge-shaped, Mediterranean life, in fact, is characterised by a eastward-open equatorial water-body that was sharp seasonality in its rhythms of activity, either in indenting Pangaea during the Triassic (Maldonado, terms of actual presence (many species spend the 1985). In the Cretaceous, the Atlantic Ocean was adverse season as dormant or encysted stages) or in formed and the Tethys connected it to the Indopacif- terms of sexual reproduction (Boero, 1994; Boero et ic Ocean, harbouring a highly diverse warm-water al., 1996; Marcus and Boero, 1998). Biodiversity is biota. In the Oligocene, a reduction in the surface of not equally distributed throughout the basin (Arvan- the Tethys Sea and a decrease of its warming influ- itridis et al., 2002). The Western Mediterranean is ence on the world oceans caused cold water condi- richer in species than the Eastern basin. Many expla- tions elsewhere. Simultaneously, at the beginning of nations have been proposed for this pattern, includ- the Miocene (10 Ma), a biota extinction occurred ing a low effort in biodiversity research. An histori- outside the Tethys (Bianchi and Morri, 2000). Dur- cal-ecological reason might be that the Eastern basin ing the Messinian crisis, about 5.5 Ma, the Mediter- is of greater tropical affinity that the Western basin ranean Sea became closed and evaporated almost and that the tropical species entering from Gibraltar completely, with just a few “pools” of water that found a temperate barrier that prevented them from allowed the survival of some paleoendemics, where- reaching the portion of the basin with proper condi- as the rest of the local biota went through a mass tions for their establishment. The opening of the extinction. After the crisis, the present-day biota Suez Canal, in fact, allowed the entrance of Red Sea originated from a contingent that entered in the basal species that thrive now in the easternmost part Pliocene (5.3 Ma) from the Atlantic Ocean through (warmer in the winter than the rest of the basin) and the newly opened Strait of Gibraltar. In spite of can also widen their geographic range under partic-

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ularly favourable conditions. Very few Mediter- populations, like the Caulerpa spp., medusae like ranean species entered the Red Sea, since the more Rhopilema nomadica (Kideys and Gücü, 1995; stable physical conditions have selected there a spe- Lotan et al., 1992; Avsar, 1999) and many fish cialised biota that easily out compete the less species. Species of cold water affinity, furthermore, focused Mediterranean species. The establishment are affected by the deepening of surface thermocline of so many Lessepsian species in the Eastern and warm waters in the summer (Francour et al., Mediterranean led Por (1989) to propose a new bio- 1994). Mass mortalities of gorgonians in the Liguri- geographical province: the Lessepsian Province. an Sea are most probably due to such impacts (Cer- This establishment of many new species of tropical rano et al., 2000). affinity suggests that the Eastern Mediterranean, From all the above, it is evident that the Mediter- after the opening of the Suez Canal, is fulfilling its ranean biota are at the opposite extreme of Indo- potential of being inhabited by tropical species. Malayan ones, characterised by an extremely long In addition to the entrance of new species from stability that yielded a very rich biodiversity that, in both Suez and Gibraltar (the Atlantic flow never its turn, was exported to both nearby and distant stopped), the Mediterranean is experiencing also the zones. If seen in the framework of source and sink transport of exotic species (Zaitsev and Öztürk, ecology (Pulliam, 1988), the Indo-Malayan region is 2001) by ships, both in hulls’ fouling and in the bal- a source and the Mediterranean is a sink. last waters of big cargoes. These release their ballast As stressed by Maurer (1999), the extremely rich in the harbour of destination, and sail away with a biodiversity of a given place might be an epi-phe- load of goods. This pattern is particularly evident in nomenon due to the immigration of species coming the Black Sea, with the traffic of oil tankers that from different source populations. Applied to the brought in ctenophores that impaired the yield of Mediterranean, the problem is: are the newly formed fisheries by feeding on fish larvae and on their food populations liable of undergoing a separate evolu- (CIESM, 2001, 2002). Another source of biological tion in respect to the source ones? Following the invasions is aquaculture. In addition, the growing allopatric model of speciation, genetic bottlenecks number of allochtonous species recorded from the and founder effects should affect the propagules basin (e.g. the algal Caulerpa spp pool) can be sure- originating new populations, leading to evolutionary ly due to unwanted (but very effective) human- novelties (or to dramatic failures) (Boero, 2002). mediated spreading. The recent natural history of Actually, the number of Mediterranean endemisms the Mediterranean Sea is full of biological inva- is very high (the most outstanding example is Posi- sions, many poorly documented but inferable from donia oceanica, the trademark of the Mediterranean the present observed distribution ranges of many Sea) and accounts for the originality of the Mediter- species. After the waters of the Atlantic, however, ranean biota. that colonization process has always been regarded The natural experiment (enhanced by human as a natural mechanism within the species’ colo- activities) of species immigration is leading to an nization strategies (Gili, 2000). For the past 200 extraordinary blend of species that makes of the years, the introduction of new species can no longer Mediterranean the ecological crossroad of the world be regarded as natural, with mankind playing a ocean, with the fastest evolving biota in terms of major role. This historical process of migrations, both ecological and evolutionary time. colonisations, and invasions has been changing the It is evident, from all this, that the Mediterranean marine ecosystem in the Mediterranean and has has always been changing (both physically and bio- given rise to an underwater landscape that can be logically) and that the change of today is not the first likened to a puzzle due to its high degree of hetero- revolution that the basin passed through. It is impor- geneity. tant, however, to distinguish human-generated A further impulse to the presence of alien species changes from changes due to natural (or more glob- of tropical affinity is the undeniable temperature al) forces. increase that characterises the Mediterranean sur- The example of Caulerpa is paradigmatic. It face waters since several years and that is probably might be possible, in fact, that C. taxifolia had been due to a tendency towards global warming. The bio- introduced in the basin by the careless management logical response to this trend is dramatic. Southern of some human enterprise (Meinesz, 1999), but the species are widening their geographical range; trop- invasion by other species of the same genus, and ical species that enter the basin establish successful their extraordinary success, calls for reconsideration

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of the causes of this phenomenon. Exotic Caulerpa almost every marine group will rapidly lead to the species coul reach the Mediterranean many times in impossibility of pursuing this kind of studies, with the past, but did not find proper conditions for the paradox that, in the era of biodiversity, biodiver- development, whereas the present situation is con- sity experts are disappearing, at least from Europe ducive to their establishment. (Boero, 2001).

The Hydrozoa as an example of inconspicuous The Hydrozoa of the Mediterranean Sea group The study of Mediterranean Hydrozoa dates back The bulk of biodiversity, in terms of species to the dawn of modern zoology. Several Linnaean numbers, is made of poorly known and inconspicu- species thrive also in the Mediterranean and, in ous species that, usually, can be noticed only by spe- 1785, Cavolini reported on Eudendrium racemo- cialised taxonomists. Taxonomy, however, is disap- sum, probably the first species described as new to pearing from most scientific communities, and our science from this Sea. Since the 19th Century, appreciation of biodiversity is biased towards con- oceanographic vessels explored seas and oceans far spicuous groups. The Hydrozoa are an inconspicu- away from Europe and few expeditions surveyed the ous group whose knowledge greatly progressed in Mediterranean. The establishment of the Zoological the last decades due to the presence of some spe- Station of Naples in the same century, however, cialists in the Mediterranean area. The number of signed also the dawn of modern marine biology: species recorded from the Mediterranean almost people from all over the world came to the Mediter- doubled in thirty years and the number of new ranean to study marine biology on a residential records is still increasing (Boero et al., 1997). The basis. Biological oceanography and marine biology 457 species recorded in this fauna represent 12% of stemmed from completely different approaches to the world species described (Bouillon et al., in marine science (oceanographic vessels Vs marine press). The ecological role of these animals, espe- stations) but had the same original aim: the explo- cially those represented also by a medusa stage, can ration of marine biodiversity. Oceanographers be great due to their general ability to feed upon fish focused on distant parts of the world and/or to deep eggs and larvae and/or on the plankton that fish lar- waters, whereas marine biologists focused on vae feed upon, so acting as potential predators coastal areas that were particularly rich in biodiver- and/or competitors of commercial species. They sity. Along with Naples, another possible location might even be keystone predators, depressing poten- for a marine station was Messina, due to the strong tially monopolising fish species, so leaving space currents of its Strait, which brought to the coast the for less competitive species (Piraino et al., 2002). unusual animals of deep waters. Metchnikoff Neglecting this apparently minor component of bio- (1886a, b) and Kölliker (1853a, b) worked exten- diversity might lead to ecological misunderstand- sively at Messina and gave important contributions ings that, in their turn, might lead to misleading to the knowledge of the Hydrozoa. The founders of interpretations of the causes affecting the yield of Hydrozoan Zoology, with very few exceptions, were fisheries. A worth-asking question is: are conspicu- from Northern European Countries characterised by ous groups sufficient to appreciate marine biodiver- hostile climates and relatively poor faunas. They sity and understand its functioning?. soon started to move towards the warmer and richer The knowledge of the biogeography of Mediter- Mediterranean to perform their studies on living ranean Hydrozoa is far from being complete, not organisms. The pattern of activity of these non-resi- only due to the continuous recording of new species dential researchers was dictated by climate and by in the basin, but also due to insufficient or geo- their academic obligations. They usually worked in graphically too concentrated research efforts, so their home countries during the winter and moved leading to inefficient coverage of distribution areas. towards the Mediterranean (mainly Naples) during The case of the Hydrozoa shows that we are still the summer. This tendency marked sharply the type very far from a proper evaluation of the structure of of Hydrozoan fauna that was going to be described biodiversity, in terms of species presence and distri- because, as we have seen, the Mediterranean is a bution, and that the understanding of biodiversity sharply seasonal sea. Other places where research function, via the identification of species roles, is on marine life became prominent were located in the even less developed. The lack of specialists in Austro-Hungarian Empire at Trieste, Rovinj, Split,

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and in France at Villefranche-sur-Mer, Endoume Origins of Mediterranean Hydromedusae: the and Banyuls. case of the fauna of marine canyons A very particular student of marine biology was Rupert Riedl. He went to Naples, and then to many The present Mediterranean hydrozoan fauna is other parts of the Mediterranean Sea, at the begin- composed of species referable to several biogeo- ning of the Fifties and started the exploration of graphic categories (Boero and Bouillon, 1993): marine caves with SCUBA diving techniques. A - Circumtropical species form the most abundant new era of marine biology began, with the entrance group with a temperate Atlantic-Mediterranean of the scientist in the environment that was the background. object of his studies. Riedl (1959) studied the - Cosmopolitan species, including panoceanic hydroids of marine caves and of rocky coasts in species occurring from the Polar seas to the Equator; general, producing one of the first ecological - Boreal Atlantic species, remnants of the ice- papers on the group. ages, especially of the Würm glacial. The new frontier of Hydrozoan studies originat- - Tropical-Atlantic species which include inter- ed in the first half of the 20th Century, when the glacial remnants especially from the Tyrrhenian British school of Hydrozoan zoology, led by F.S. stage. Russell and W.J. Rees, started to work at the build- - Mediterranean-Atlantic species with eastern ing of a single classification for both hydroids and Atlantic migrants, specially into the Alborán Sea. medusae. They opened a research project that is still - Indo-Pacific species. far from being accomplished: reconstruct the life - Endemic species comprising both paleoen- cycle of all species so to treat them as a single bio- demics, of Tethyan origin, and neoendemics, main- logical and taxonomical unit. In the Mediterranean, ly of Pliocene origin. at the Naples Zoological Station, this project was the The origins, and the originality, of the fauna basis for a great enterprise that was expected to lead inhabiting the depths of the Mediterranean Sea are to the Hydrozoan Fauna of the Mediterranean. debated. The temperature there is constantly 13°C, Bouillon, Brinckmann-Voss, Haeckel, Petersen, Ste- thus higher than that of the Atlantic, from where most chow, Tardent, Vannucci, Uchida, Yamada and oth- of the Mediterranean fauna originated. The Gibraltar ers amongst the most prominent researchers of sill, moreover, is too shallow to permit the entrance of Hydrozoa gathered at Naples and worked there for bathypelagic species in the Mediterranean after the more than a decade. Unfortunately, the project was Messinian crisis. Recent studies on Mediterranean accomplished only in part and Brinckmann-Voss submarine canyons provide important clues about (1970) published just the first of a series of mono- some aspects of the origin of deep-sea biodiversity in graphs that should have covered the Hydrozoa of the the basin. Marine canyons are channels for the trans- Mediterranean Sea. Another great contribution to port of large quantities of organic matter from the the knowledge of Mediterranean Hydrozoa came coastal region to the deep-sea via downwelling cur- from the work of Picard and a group of his pupils rents (Vetter and Dayton, 1998). They are systems who, at the Endoume Marine Station, bridged tax- with high production rates and hence locations capa- onomy, phylogenetics and ecology. At the Zoologi- ble of attaining high faunal richness. Submarine cal Station of Villefranche, a long series of papers canyons, moreover, may strongly contribute to the mainly by Claude Carré and Danièle Carré gave a biological production processes in many coastal great contribution to the knowledge of the regions via their upwelling currents (Della Tommasa Siphonophora and of the Hydromedusae. et al., 2000). Furthermore, they may also play an In 1985, at the Laboratory of Benthic Ecology of important role in speciation processes affecting the the Zoological Station of Naples, at Ischia, the deep-water fauna, as observed in the Foix, Lacaze- Hydrozoan Society was founded, gathering most of Duthiers, and Planier canyons, located in the western the active students of the Hydrozoa from all over the Mediterranean, where medusa species richness is world (Bouillon et. al. 1987). This gave new impulse high, with seven new species being found recently to the study of the Hydrozoa and set the basis for a (38.8% of the total) (Gili et al., 1998; Gili et al., host of collaborations that has been increased with 1999). This discovery raised the level of endemism in joint work and publications in following meetings of the deep-sea Mediterranean medusan fauna to 24%. the Hydrozoan Society (Bouillon et al., 1992; The species were collected by sediment traps located Piraino et al., 1996; Mills et al., 2000). above the seabed at the 1000 m isobath in the

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canyons, a region inaccessible to conventional sam- species, to set the basis for a never to be made Faune pling methods. de France volume on the group. Boero and Bouillon The most important aspect of the discovery is the (1993) updated the work of Picard, treating all the relationship between the number of individuals of Hydrozoa besides the Siphonophores, bringing the endemic species and the ecological features of the list to 346 records. Boero et al. (1997) further updat- submarine canyons. In the canyons, the number of ed the list to 379 species. To these, the Siphonopho- individuals increased progressively as the total flux of ra have to be added. Boero and Bouillon (1993) organic matter reaching the interior of the canyons treated the life cycle patterns of the Hydrozoa and increased. In addition, canyons with close-together their bearing on the distribution of these organisms. walls might increase isolation while attenuating They also defined zoogeographical regions having hydrodynamic processes and are thus home to larger the Mediterranean as their centre, and made an numbers of individuals. Furthermore, almost all the analysis of the affinities of the fauna. These topics new species were endemic to one of the canyons, sug- will not be treated further here. gesting a high level of isolation inside. These canyons A complete bibliographic database on the Hydro- had ancestor paleocourses in the Messinian period (5 zoa is on line, and can be found at the following Ma ago), when the Mediterranean dried up nearly address: http://siba2.unile.it/ctle/hydro/index.php3. completely. Still, some areas, such as the deepest part of these canyons, were not completely dried up since The records Messinian evaporated deposits accumulated there (Hsü et al., 1978). This indicates that the deepest part All species reported at least once from the of these canyons remained submerged during the Mediterranean are part of the list. Some records are Messinian times. The two new species of the genus old and need reconfirmation, but they were kept to Foersteria described in the Mediterranean (F. antoni- help future workers that might find them again. As ae in the Lacaze-Duthiers Canyon and F. araiae in the it happens for all groups, also in the Hydrozoa there Foix Canyon) (Gili et al., 2000) have two congeneric are common and rare species. The history of species in the Pacific (F. purpurea) and Indian Oceans records, however, indicates that the species contin- (F. bruuni). Probably, the common ancestor of both gent of the Mediterranean is going through great the Mediterranean species and the oceanic ones changes and that species that were not recorded in inhabited the Tethys Sea. That ancestral species the past, presumably due to their rarity, are now underwent a process of allopatric speciation both common, whereas species that have been found in worldwide, when the drying up of the Tethys Sea sep- the past are not being reported anymore. Species arated the Atlantic and the Pacific basins, and at a records can be divided into the following categories: local scale, when the parallel canyons became sepa- a) “Evident” common species. These species are rated as well. Indeed, the ecological differences known since a long time and can be found in almost between the canyons are probably responsible for every sample from a proper environmental setting. generating the allopatric speciation found there. Their list comprises popular species such as Euden- The discovery of this singular medusan fauna is drium racemosum, E. glomeratum, Aglaophenia a key to investigate the origin of the Mediterranean spp., Clytia hemisphaerica, Obelia dichotoma, O. deep-sea fauna. It also calls for the protection of geniculata, Dynamena disticha, Sertularella gau- marine biodiversity. Mediterranean submarine dichaudi and S. crassicaulis. The set of species canyons incise the continental shelf and approach inhabiting Posidonia leaves are part of this group, very close inshore. Mediterranean coastal regions even though one of them, a Sertularella, is still to are overpopulated and cause heavy environmental be described formally. Some common species, even impacts that may be channelled through the subma- of large size, can have been misidentified in the rine canyons and, consequently, that fauna is threat- past, so that their names might be rather obscure. ened and could disappear entirely even before it The most striking case is possibly Eudendrium becomes fully known. armatum, a large species that can be invariably found on the roofs at the entrance of caves and Lists of Mediterranean Hydrozoa crevices. Its general aspect resembles that of Eudendrium rameum and is possibly often reported Picard (1958b) made a complete list of Mediter- with this name. Riedl (1959), in his monograph on ranean Antho- and Leptomedusae, summing up 191 the hydroids of Mediterranean caves, did not men-

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tion it, but recorded repeatedly E. rameum, even are so different from those of any other species that figuring it in his popular guides of the Adriatic and Picard (1957), describing it as a new species, the Mediterranean flora and fauna. Confirmed ascribed it to a new genus and a new family! It is records of Eudendrium rameum are very rare, almost impossible that such a species passed unno- whereas E. armatum is extremely common. Species ticed to all the people who worked earlier on very common in plankton communities along Mediterranean hydroids, if not for its extreme rarity. coastal waters mainly in spring-summer are the In the Seventies and Eighties Paracoryne huvei medusae Aglaura hemistoma and Rhopalonema became common along the northern coasts of the velatum, and the siphonophore Muggiaea atlantica Mediterranean and was repeatedly reported. Then it (e.g. Gili et al., 1988). Species more common in disappeared again and went back to rarity. The pres- open waters, throughout the water column includ- ence of resting stages in its cycle can be the reason ing deep layers are Solmissus albescens, Sol- why the species is able to disappear and reappear. mundella bitentaculata and the siphonophores Che- Extra long diapause might be rather widespread in lophyes appendiculata, Lensia conoidea and Aby- most species since all hydroids can become dormant lopsis tetragona (Mills et al., 1996). while regressing to resting hydrorhizae. This pattern b) Cryptic species now collected more frequent- of presence makes it possible to be active during the ly due to increased sampling efficiency. Halocoryne favourable season, but might be also the way these epizoica, a species described by Hadzi in 1917 from animals can disappear for decades and be suddenly the Adriatic Sea, was not found again until Picard back again. This pattern is even more evident for reported it from the Ligurian Sea, fifty years later their medusae! The second example refers to a (see Piraino et al., 1992). The species was anyway species that was formerly very abundant and is now so “rare” that Brinckmann-Voss (1970) could not apparently rarer: Ectopleura crocea (=Tubularia find it while working at her monograph on capitate crocea). Pierre Tardent worked extensively on pop- hydroids and medusae. Halocoryne epizoica is ulations of this species living in the Gulf of Naples. strictly symbiotic with the bryozoan Schizoporella He chose it as experimental animal due to the ease sanguinea, a very abundant species in sea urchin of finding specimens in the harbour on every season. barrens, at low depth. This type of environment is He went back to Naples after thirty years, consider- easily reachable by SCUBA diving techniques, but ing the opportunity of performing more work but is not easy to sample from the surface with grabs had to give up his project because he could not find and dredges. The yield of samplings, thus, can be a single specimen (personal communication to F.B.). biased by the employed techniques. This means that It is possible that the period of commonness is rather H. epizoica might have been common even in the long, as that of rarity. It is part of the ecology of all past but that it passed unnoticed due to sampling dif- gelatinous plankton (and of its benthic counterpart) ficulties. The same is true for Cytaeis schneideri to be present with massive blooms or even outbreaks (formerly referred to as Perarella schneideri), and to be absent even for decades thereafter. This is another specialist for symbiosis with bryozoans. possible mainly due to the presence of benthic Another example is the medusa Ptychogastria aster- stages that can become encysted, so escaping most oides, previously found in two places in the sampling efforts. Some holoplanktonic species fol- Mediterranean but nowadays caught frequently by lows high inter-annual bloom variation mainly in sediment traps located near the bottom of submarine coastal waters. Over recent decades, man’s expand- canyons (Gili et al., 1999). The first casual records ing influence on the oceans has begun to cause real probably could indicate intrusion of waters from the change and there is reason to think that, in some deep sea to the continental shelf. regions, new blooms of jellyfish are occurring in c) Species that are alternately rare and common. response to some of the cumulative effects of these Paracoryne huvei became frequent and abundant for impacts. Beyond that basic life cycle-driven season- a relatively narrow time window. It cannot be al change in numbers, several other kinds of events missed or mistaken with anything else, since it lives appear to be increasing the numbers of jellies pre- in the infralittoral zone and is the only known sent in some ecosystems (Mills, 2001). In the Mediterranean hydroid that settles higher above the Mediterranean, the frequency of jellyfish blooms mean sea level. It forms large pink patches on black increased during the last decades causing important mussels and on bare rocks that can be seen while problems in the people that visit beaches during walking along the shore. Its polymorphic colonies summer time. There are several hydrozoan species

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generating dense blooms that can be observed near siphonophores Forskalia spp., which became more the coast (e.g. Lizzia blondina, Velella velella). common in the entire occidental basin during the d) Species that newly entered the basin. The last years (Dallot et al., 1988). Another interesting study of Lessepsian migration from the Red Sea to species is the Antarctic anthomedusan Russellia the Mediterranean through the Suez Canal originat- mirabilis recently found in the Alboràn Sea (Pagès ed a wealth of information about Indo-Pacific et al., 1999) and that arrived to the Mediterranean species entering the basin (Por, 1978; Spanier and probably through a complex life cycle together with Galil, 1991). No such records regarding the Hydro- the transport role of Antarctic Intermediate and Bot- zoa were noticed until recent times. Clytia gravieri, tom waters. a nominal campanulariid species, however, was e) Species that are rare since their discovery. described from specimens coming from the Suez Rarity can be either soffusive, when a species is rare Canal by Billard (1938). Subsequently, it was con- at many places but common at least at one, or diffu- sidered as conspecific with Clytia linearis, a species sive, when a species is rare everywhere it occurs first described from the Indo-Pacific. This species (Schoener, 1987). The number of records is not so was first recorded from the Mediterranean in the great for most of rare species, and it is difficult to Fifties and might be one of the first (and undetected distinguish between the two types of rarity for any as such) Lessepsian migrants. Now it is one of the of them. Rarity, furthermore, can be geographical or commoner hydroids of shallow rocky Mediter- ecological. Geographically rare species live in ranean coasts. Due to its branched habit, it is distinct restricted areas, and are absent in other areas that, from most other Clytia and it is highly improbable nevertheless, have the same features as the areas that in the past it was as abundant and frequent as it where they thrive. Ecologically rare species have is now and that it simply passed unnoticed. Hydro- very strict ecological requirements that are met just zoan researchers found much more inconspicuous at few places; if their particular requirements are and relatively rare species than this one, so that they met, however, they are often present. For the Hydro- should have reported it frequently. Being a tropical zoa, furthermore, rarity can be also linked to sea- species, it is probable that the recent tropicalisation sonality, since some species can be present over a of the Mediterranean favoured its success in the very short time window and become encysted (usu- basin. Another way to enter the Mediterranean, of ally as hydrorhizae) for the rest of the year. The best course, is through the Strait of Gibraltar. The study example of this is Rhysia autumnalis, a species pre- of the Hydrozoa of the Alborán Sea (Ramil and Ver- sent only in autumn and that, furthermore, is strict- voort, 1992; Medel and Vervoort, 1995; Medel et ly linked to serpulid tubes (Brinckmann, 1965b). al., 1998) is leading to many new records and this is Hydractinia inermis, on the contrary, is present for evidently a hot spot of new entries from the Atlantic a short period in the spring, and disappears for the Ocean. A recent introduction is Clytia hummelincki. rest of the year. Information about rare species, It was recorded in the Mediterranean for the first though, is often insufficient to assign them to any time in 1996, along the coasts of Calabria (Boero et particular category. The only Mediterranean hydro- al., 1997), almost in the centre of the basin. Being zoan that is mentioned in red lists is Errina aspera, present both in the Atlantic and in the Pacific (with probably due to its calcified skeleton, its resem- rare records) it is difficult to establish if it entered blance to a coral and its restriction to the Strait of from Suez or from Gibraltar. At present, this species Messina (Zibrowius and Cairns, 1992) where, how- is very successful, forming a belt at 0.5-1 m depth in ever, is very abundant, so being an example of sof- sea urchin barrens along the Apulian coast, where it fusive rarity. A good example of rare species is is extremely common and abundant in the summer. Codonorchis octaedrus, described by Haeckel in Its distribution in the rest of the basin is unknown, 1879 from the Atlantic coast of France and never probably because it can be mistaken with species of found again since Boero et al. (1997) reported its the genus Campanularia and only hydrozoan spe- hydroid from a cave of the Ionian Sea, reconstruct- cialists can identify it properly. In the same period, ing its life cycle. In this case, however, rarity might Bitar and Bitar-Kouli (1995) recorded Macro- be an artefact due to inconspicuousness of the rhynchia philippina from the coasts of Lebanon, hydroid and to the resemblance of the medusa to undoubtedly a Lessepsian migrant. The area of those of the genus Amphinema, so that the species Gibraltar still is a place where is easily to detect the might have been passed unnoticed as hydroid and presence of newly recorded species, such as the misidentified as medusa. Some siphonophores

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(Rosacea villafrancae Carré, 1969) have not been place according to the season. Boero and Fresi recorded since their description probably because (1986) studied the seasonality of nearly one hundred difficulties for taxonomic identification. species of Antho- and Leptomedusan polyps at a f) Declining species. This category is very elu- single study site of the Ligurian Sea, showing the sive and might be included in that one comprising existence of two distinct hydroid faunas, character- species that are alternately rare and common. The ising the warm and the cold season respectively. concern about species threatening and extinction Boero et al. (1986) studied the seasonality of Euden- invariably regards popular and conspicuous species, drium glomeratum, illustrating the sudden growth of as the above-mentioned Errina aspera. This attitude its colonies and their equally sudden decline. The is partly linked to the perception of species by the pattern of growth of most hydroids involves sudden lay people, but has its foundation also in the attitude colony appearance, production of gonophores of researchers. If it is easy to recognise that a species (either fixed or as free medusae) and subsequent has become abundant, in fact, it is more difficult to decline. The life of most medusae ranges between a demonstrate that it has become rare, since absence is few hours to one month, and the production of plan- less evident than presence. In other words, ulae, thus, takes place with such a delay from researchers tend to stress what they find instead of medusa liberation, whereas the colonies with fixed what they do not find. To recognise decline we gonophores usually produce planulae directly. A should be able to check the presence of species from reasonable expectation is that, after fertilisation and the published records of all the researchers that planula development, the population of hydroids worked on the group, comparing their results. A will increase in number and density; instead, it usu- declining species might be one that is not found ally suddenly declines. The obvious explanation is since fifty years, after having been found repeatedly that either planulae or newly formed colonies are during the previous fifty years, taking care of both able to encyst and to wait for the following the types of sampled environments and seasonality. favourable season (or even successive ones) to pro- If Eudendrium rameum is really a Mediterranean duce noticeable and reproductive colonies. species and its records are not simply misidentifica- Colonies, furthermore, can remain asexual for tions of E. armatum, then this species is probably a long times, without producing reproductive bodies declining one. One example of these declining (either medusae or fixed gonophores). This was species is also the siphohonophore Apolemia uvaria stressed by Edwards (1973c) who observed that (Carré and Carré, 1994). It is important, thus, to medusae of some species could be absent for years, reconstruct the history of the study of all species, so being continuously present as hydroids only. to have maps of their records and keep their “health” The gelatinous zooplankton species without ben- under control. At present, however, no hydrozoan thic stages, however, can be sharply seasonal too, so species are sufficiently well known to deserve the generating doubts about their holoplanktonic way of status of either threatened or endangered. In this last life. Many plankters, in fact, have inconspicuous case, it is important to mention the species that are resting stages (see Boero et al., 1996; Marcus and continuously threatened and eliminated by trawlers. Boero, 1998 for reviews) and easily escape detec- Lytocarpia myriophyllum, for instance, was very tion. Many calanoid copepods, traditionally consid- common on sandy and mud benthic shelf communi- ered as holoplanktonic, spend the adverse season as ties in the Mediterranean and is now much rarer than benthic cysts, wrapped in a chitinous sheath. The before (Gili et al., 1987). perisarc of the Hydrozoa is made of chitin and the polyps easily form cysts with their hydrorhizae Seasonality and life cycles (Bouillon, 1995a). The list of hydrozoan species from a given area, As stressed above, the Mediterranean is a thus, cannot be the result of a single sample. Boero markedly seasonal sea and its summer and winter and Fresi (1986) reported two main seasons, having faunas have different zoogeographical affinities and their centre in February and July, so that these two ecological requirements. The Hydrozoa, in particu- months might be sufficient to have an almost com- lar, are mostly seasonal in occurrence and the possi- plete species list for a given locality. This, however, bility for the polyps to become encysted as resting is not enough to find reproductive colonies, since hydrorhizae contributes to the presence of great dif- gonophores can be produced for very short periods ferences in the species that can be found at a given or, as we have seen, can be absent for several years,

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just as the whole colonies can, remaining present as tonic populations are continuously changing and dormant hydrorhizae. Carefully taken samples often that seasonal peaks of abundance show an increment give some novelties, even from the most explored of the total population but do not indicate a clear coast, in terms of new records for the area, or of pattern of seasonal growth. Cnidarians perform reproductive colonies of species with unknown life daily migrations in the water column, with wider cycle, if not of species new to science. Boero et al. ranges in oceanic waters that near the coast. For (1997), keeping a small substrate fragment in an almost all species, these vertical movements are aquarium, observed, in sequence, the appearance of closely related with the search of food (Mackie et Zanclea sp., Trichydra sp., Thecocodium brieni, al., 1987). In general, even though hydrodynamic Turritopsis nutricula and Codonorchis octaedrus. conditions are important in determining spatial and Evidently, these species coexisted as hydrorhizae on temporal heterogeneity of cnidarians in the plank- that small space and alternated in becoming active, ton, trophic relationships play a key role as well a quite common behaviour for most hydroids. (Arai, 1988). Zooplankton studies in the northwestern Mediterranean showed seasonal changes in abun- The “role” of the Hydrozoa dance for many medusae and siphonophores, such as the more common species, Aglaura hemistoma Ecological roles have been taken as a very and Muggiaea atlantica, in consecutive years (Goy, important issue to emit judgement about the rele- 1985). This seasonal variation has been related to vance of species, so to produce convincing evi- fluctuating local hydrographic conditions and pri- dence about the need for their protection (Piraino mary production peaks (Gili et al., 1987). The max- et al., 2002). This attitude, of course, implies that imum abundance of cnidarians in the plankton is if a species has no recognised role, it is implicitly observed when the water column is homogeneous, regarded as less important than a renowned or when stratification begins, at the end of spring. species. This causes a great bias in the way we per- Two main peaks have been described, the first one in ceive biodiversity. We are attracted by conspicuous April-May, dominated mainly by siphonophores in species. Our knowledge on the roles of species is coastal waters. This siphonophore peak precedes the so scant that we cannot consider any species as maximum abundance of medusae, which coincides unimportant a priori. Only recently, for instance, it with the yearly maximum of all zooplankton in the is generally perceived how phytoplankton is more Mediterranean (Ribera d’Alcalá et al., 2004). The important than (or at least as important as) tropical maximum siphonophore density is observed before rain forests in maintaining the climate of the whole that of the medusae and it could be explained planet the way it is (Falkowski, 2002). Diatoms because of the formation of polymorphic colonies and flagellates are not as impressive as oaks and with high growth rates (Purcell, 1982). The second redwoods, just as copepods and small jellies are period of siphonophore abundance, partly coming not as impressive as whales and sharks. Marine from the eudoxids produced during the first period, systems are based on microscopic life and, thus, shows more marked peaks than that of medusae are generally undervalued. Most conservation pur- (Gili et al., 1987). The stability of the water column poses are first biased in favour of terrestrial sys- promotes the increase of zooplankton populations tems and, when the sea is considered, in favour of and, thus, of the gelatinous carnivore zooplankton, big, charismatic species, usually vertebrates and favoured by the availability of potential prey. Even higher plants (with the sole exception of corals and the peaks of abundance of cnidarians are dominated some molluscs). The Hydrozoa are no exception by few species, their distribution and abundance will and, thus, tend to be considered as “negligible” if have a large influence on the whole community, compared to groups that are more “visible”. This allowing the presence of less competitive species at attitude is based on a naive way of conceiving ecol- the end of the prevalence of the more abundant ones, ogy and is simply wrong. The case of Mnemiopsis such as M. atlantica and A. hemistoma. Seasonality lleydi, for instance, shows that a gelatinous preda- and abundance are not independent. In general, sig- tor can impair larval survival and subsequent nificant differences in size among individuals of recruitment of commercial fish, greatly impacting medusae and siphonophores have been observed in on human activities (see Boero and Briand, 2001). the same sample, but not in different periods of the This ecological role might be played also by year. This leads to explain that the cnidarian plank- hydromedusae, since many species are of the right

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size to predate on fish eggs and larvae and, fur- species, particulate organic matter (POM) also con- thermore on their prey, so acting as both predators tributed a significant portion of the diet (e.g. Cam- and competitors. The arrival of the already cited panularia everta). Benthic organisms (e.g. nema- Clytia hummelincki in the Mediterranean, and its todes or small bivalves) were found only occasion- large hydroid populations, producing great num- ally. The diet of Silicularia rosea is almost exclu- bers of relatively large medusae might play an sively benthic diatoms, captured when the bottom important role in the success of fish recruitment, by sediment is disturbed and resuspended. The results removing eggs and larvae from the environment. confirm that benthic hydroids can feed on a great The impact on biodiversity, however, might even variety of prey. Apart from zooplankton, they can be positive, since predation on the larvae of partic- feed on bacteria, protozoa, phytoplankton, detritus, ularly successful fish species might decrease their and even on metabolites of algal origin or dissolved abundance so to leave space for the development of organic matter (Gili and Hughes,1995). Hydrozoans previously outcompeted fish species, so enhancing account for a small fraction of total community bio- fish diversity. mass, and the amount of total energy they ingest is The difficulties of studying hydroids as part of the less than that recorded for dense populations of communities of hard substrates have limited apprecia- active suspension feeders such as bivalves. Never- tion of their importance in those communities. Most of theless, the high capture rates recorded in all the the available knowledge comes from studies of artifi- species studied, and their often high densities, indi- cial substrata placed in the sea for variable lengths of cate that hydroids may play a significant role in time (Boero, 1984; Gili and Hughes, 1995). Hydroids energy transfer from the plankton to the benthos in are often abundant in initial stages of colonization and shallow marine ecosystems as they capture up to 105 in the later stages of community development by col- prey items m-2 d-1 (Coma et al., 1995). The highest onizing other organisms (Riedl, 1959). Once estab- capture rates recorded were very similar to the rates lished, hydroids may prevent settlement by other col- observed in laboratory experiments in which feed- onizing species (Young and Chia, 1987). Obelia ing rates were maximal as food was not limiting dichotoma inhibited settlement of other invertebrates, (Gili and Hughes, 1995). Under natural conditions, partly by eating their larvae (Standing, 1976), and the colony growth rates may be very high, with duplica- dense colonies of Hydractinia echinata prevented set- tion of colony biomass in less than a week (Hughes, tlement and even overgrowth by other species by suc- 1983; Llobet et al., 1991), in which nearly 40 % of cessfully defending the space (Sutherland and Karl- energy consumption may be invested in growth dur- son, 1977). The accumulation of sediment among and ing non-reproductive periods. In fact, hydroids are beneath the hydrocauli of Tubularia larynx may pre- like plants they have indeterminate growth, the rate vent settlement by the larvae of other species (Östman, of which is determined by energy input, and will not 1977). Conversely, T. larynx may facilitate colonisa- grow at all, but will survive indefinitely, if energy is tion by other species, such as ascidians (Schmidt, limiting (Gili and Hughes, 1995). Miglietta et al. 1983). While studies on artificial substrata may pro- (2000) reviewed on the ethology of both hydroids vide some idea of seasonal variations in species abun- and medusae, revealing a great range of behavioural dance within an area, it may be that only a small num- patterns. ber of species colonise artificial substrata (Millard, 1959). In addition to their economic nuisance as mem- bers of the fouling community (Morri and Boero, GENERAL CLASSIFICATION 1986), hydroids may pose specific problems, for example in self-contained aquaculture systems, where Superclass HYDROZOA they endure by developing resting stages capable of tolerating substantial changes in temperature and dry- Definition: Cnidaria with either tetramerous, ing conditions (Sandifer and Smith 1979). polymerous or, exceptionally, biradial symmetry; The hydroid polyps, furthermore, are also very gastrovascular system simple, deprived of sto- important in the passage of energy from pelagic to modeum (pharynx, actynopharynx), septa or gas- benthic systems (Gili et al., 1998). The diet of most tric tentacles; mesoglea acellular; sexes generally species studied, consisting largely of algal cells (e.g. separated; gametes, with few exceptions, ectoder- Nemalecium lighti) and zooplankton (e.g. Eudendri- mal in origin (endodermal in the Polypodiozoa, um racemosum or Tubularia larynx). In some Actinulidae, Nannocoryne mammylia, Pegantha

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clara and Solmaris flavescens), ripening usually in Class AUTOMEDUSA Lameere, 1920 emend. the ectoderm and shed directly to the outside, never (see Bouillon and Boero 2000). into the gastrovascular cavity (except Polypodi- (Actinulidae, Narcomedusae, Trachymedusae) um?); medusae with velum (except Obelia), a mus- (Figs. 1, 16A). cular membrane projecting inwards from the umbrellar margin and partially occluding the Hydrozoa with usually direct development and umbrellar opening; polyps, when present, solitary entirely pelagic life cycle, planulae never settle and or, most often, colonial, modular, with intercon- acquire a benthic habit, each usually transforming nected coelenterons, often polymorphic, with chiti- into a single young medusa, except in parasitic nous exoskeleton (perisarc), some secreting exten- forms; sexes separate; sex cells generally ripening in sive calcium carbonate exoskeletons (coenos- the ectoderm, each fertilised egg giving rise to a sin- teum); cnidocysts of about 24 major categories, gle medusa, except in some Narcomedusae where generally restricted to the ectoderm; atrichous parasitic stages issue from the egg may give rise to isorhizas are the only cnidocyst type found several medusae by asexual budding; medusa for- throughout the Hydrozoa, never very common, but mation without medusary nodule, subumbrellar cav- present at least in some species of all classes, they ity and velum formed by folding and deepening of occur also in Anthozoa, Cubozoa and Scyphozoa; the oral embryonic ectoderm, so being analogous to life cycles involving: 1) planulae developing the subumbrellar cavity and velum of the directly of into medusae, or into intermediate “act- Hydroidomedusa; primary marginal tentacles inula”-like stages (Automedusa); 2) planulae always formed before subumbrellar cavity and gas- developing indirectly into either solitary or modu- trovascular system; marginal tentacles deprived of lar, asexual polyps, generating planktonic, individ- tentacular bulbs (see peronia); sensory organs as ual, sexual medusae usually by budding via a ecto-endodermal statocysts, with an endodermal medusary nodule; 3) many paedomorphic species axis, growing out from circular canal, with sensory with various degrees of medusa reduction, reduced cells characterised by numerous kinocilium-lacking medusoids generally producing gametes without rootlets, surrounded by stereocilia, innervated by the breaking away from polyp colony, sometimes func- upper nerve ring; lythocytes and statoliths of endo- tioning for the propulsion of planktonic colonies dermal origin; asexual reproduction present only in (Hydroidomedusa); 4) endocellular parasitic (poly- “actinula”-like larvae and adults of Narcomedusae; poid?) stages producing free-living (medusoid?) frustules and cysts unknown. tentacled stages (Polypodiozoa). Remarks: Intermediate tentaculated post-embry- The Hydrozoa are a wide and heterogeneous onic stages of Narcomedusae have been inappropri- group, comprising taxa that share few derived fea- ately called «actinulae», and considered identical tures, namely the velum, absent only in Obelia (see with the Anthomedusae actinula. With the exception Boero et al., 1996 for a detailed treatment of the of the interstitial Actinulidae, the Automedusa are peculiarities of this medusa and on its possible ori- all oceanic, mainly represented by deep sea or open gin), and the ectodermal “gonads”. The superclass sea species. Their typically diploblastic “bauplan” Hydrozoa comprises three classes: the Automedusa, limited their evolution so that, although having a the Hydroidomedusa and the Polypodiozoa (see very wide geographical distribution, the Autome- Bouillon and Boero, 2000). dusa show a limited generic and specific diversity. The Hydrozoa are important carnivores; they are They may be considered as the most primitive of the among the strong planktonic and benthic predators, recent Hydrozoa, similar to hypothetical ancestral when abundant they are actually major consumers of Hydrozoa. crustaceans, fish larvae and other planktonic and epibenthic organisms. Some species may feed on Class HYDROIDOMEDUSA Claus, 1877 bacteria, protozoans, phytoplankton and even dis- emend. (Bouillon and Boero, 2000). solved organic matter, other species harbour symbi- (Anthomedusae; Laingiomedusae; Leptomedusae; otic intracellular algae from which they may fix Limnomedusae; Siphonophorae) some nutrients. Hydromedusae have been used as (Figs. 2, 16B). biological indicators to predict movements of oceanic waters. Several species are known as indi- Hydrozoa usually undergoing indirect develop- cators of upwelling systems. ment through a succession of distinct stages. The

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“planula”, a ciliated motile gastrula, typically devel- statocysts are innervated by the upper nerve ring and oping into a benthic, modular, larval stage, the polyp also lithocytes and statoliths are of endodermal ori- (except in the Porpitidae, Margelopsis and Pelago- gin. The sensory cells of Limnomedusae statocysts hydra where the hydroid is floating). Polyps giving are devoid of stereocilia. They present, thus, inter- rise, by asexual budding, to planktonic, free-swim- mediate features between Leptomedusan and ming and solitary hydromedusae, representing the Automedusan statocysts. The presence of both a sexual adult. Medusa often reduced to sporosacs medusary nodule and of colonial modular hydroids (fixed gonophores), so that hydroids, by paedomor- suggests the inclusion of the Limnomedusae within phosis, secondarily become the sexual stages. The the Hydroidomedusa. Hydroidomedusa may also form pelagic swimming The Hydroidomedusa have, with a few excep- or floating, highly polymorphic modular colonies tions, separated sexes; the sex cells generally mature composed of several modified types of polyps and in the ectoderm. The fertilised oocytes give rise by reduced medusae attached to a stolon supported by gastrulation to typical planulae, which are very spe- floating structures (pneumatophores and nec- cialised contrary to Automedusa ones, containing tophores) (Siphonophorae). (except in the Siphonophorae) cnidoblasts, different Besides extreme cases of medusa reduction (e.g. neural and glandular cell types and, often, interstitial Hydra and Rhysia), medusa budding occurs via a cells. During the transformation of planulae into pri- medusary nodule or entocodon, forming a coelom- mary polyps, the embryonic neural and cementing like cavity, the subumbrellar cavity, lined by striated glandular cells are destroyed. Hydroidomedusa are muscle cells; primary marginal tentacles always mostly marine, but some live in brackish or in fresh- develop after subumbrellar cavity and gastro-vascu- water, they are present at all latitudes and at all lar system. Both embryonic and larval stages, the depths. Hydroidomedusae are frequently seasonal, planula and the polyp, typically diploblastic; adult the hydroid stage may develop several types of rest- sexual stages, the hydromedusae, acquiring a ing stages (frustules, propagules, cysts, dormant tis- “triploblastic” kind of organisation during embryon- sues in the stolon system) allowing them to over- ic development (medusary nodule formation) come unfavourable ecological conditions. (Boero et al., 1998). Remarks: Hydroids can be solitary, but generally Class POLYPODIOZOA Raikova, 1988 form modular colonies by simple budding. The (Fig. 156) colonies often produce polyps specialised for differ- ent functions, all having an interconnected coelen- Life cycle as a succession of a free-living stage teron (defensive: dactylozooids, reproductive: gono- and of a stage parasitizing the eggs of some zooids, nutritive: gastrozooids, etc.). The sense Acipenseridae and Polyodontidae Pisces. organs of pelagic hydroidomedusae, when present, The earliest known stage is a binucleate cell, par- are ocelli (Anthomedusae, some Leptomedusae), or asitizing previtellogenetic fish oocytes. Further devel- statocysts (Leptomedusae, Limnomedusae); some- opment may last several years, leading to a convolut- times cordyli of unknown function are also present ed didermic stolonal structure, with inverted germ (Leptomedusae); siphonophores have no visible layers, forming numerous inverted buds. Before fish sense organs. Statocysts have different origins and spawning, eversion takes place and the germ layers structures: closed or open velar ectodermal stato- take their normal position (ectoderm outside, endo- cysts are formed by the subumbrellar epithelium or derm inside). The stolon exits the egg and becomes velum epithelium (all Leptomedusae); ecto-endo- fragmented into individual buds, each giving rise to a dermal closed statocysts are located in the mesoglea, free creeping globular stage that multiplies by longi- near the ring canal or in the velum (Limnomedusae). tudinal fission. Globular stages can move and feed, The sensory cells of velar ectodermal statocysts are having an oral mouth-cone and 24, 12 or 6 tentacles, innervated by the lower nerve ring (= inner or sub- according to season. Germ cells are endodermal. So- umbrellar) and, lacking stereocilia, are morphologi- called females with two kinds of “gonads”, each with cally distinct from those of the sensory clubs of the a gonoduct opening in the gastral cavity. So-called Automedusa; lithocytes and statoliths are ectoder- males deprived of gonoducts, their “gonads” forming mal in origin. Only the Limnomedusae, among the gametophores carrying cnidocysts. Hydroidomedusa, have ecto-endodermal statocysts, Remarks: It is not known how the parasites get similar to those of the Automedusa. In both groups, into young previtellogenic fish oocytes. The free-

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living stages are presumably homologous to sexual which fix the colonies to the substrate and from medusae, the parasitic stages being considered as which arise, from place to place, either sessile polypoid. By their stolonal parasitic budding stage polyps, or polyps supported by a short pedicel, or and their cnidome, the Polypodiozoa seem to pre- large erect, often branched stems bearing numerous sent some affinities with the Narcomedusae, to polyps, either sessile or pedicellate. Main stems and which they were previously assigned. This class pedicels form the hydrocaulus; lateral branches comprises only Polypodium hydriforme Ussow, bearing hydranths are the hydrocladia. Stolons, 1885, which was till recently the only known meta- hydrocauli and hydrocladia are formed by ecto- zoan adapted to an intracellular parasitic life. endodermal tubes surrounding a prolongation of For Siddall et al. (1995) the Myxozoa are related hydranths’ gastric cavities, enveloped by a protec- to Polypodium, and he proposed their demise as a tive chitinous layer, or perisarc. The living ecto- phylum of protists and suggesting their inclusion in endodermal part of the tubes is the coenosarc. It is the Cnidaria, Hydrozoa, but for Okamura, Curry, by this common tubular system of coenosarc that all Wood, and Canning (2002) the myxozoans are not the hydranths making up a colony communicate Cnidaria but Bilateralia this based on significant dif- with each other allowing, for instance, food circula- ferences between myxozoan Hox genes and cnidar- tion. The coenosarc represents the bulk of the living ian Cnox genes. On the other hand for Zrzavy and material of the colony. Hypsa (2003) Polypodium should not belong to the New hydranths are always formed by asexual Cnidaria but together with the Myxozoa form a budding, this commonly leading to colony forma- clade the Endocnidizoa that belongs to the Bilater- tion and growth. Hydranth budding rarely occurs on alia clade. Pending more studies we tentatively the hydranths, except in solitary forms, where later- retain the Polypodiozoa in the Cnidarians. The al budding is a way of asexual reproduction leading cnidocytes with their cnidocysts are one of the most to separate individuals. In colonial forms, budding complicated cellular structures of the animal king- usually occurs on stems and stolons. The medusae dom and it is doubtful that they could have evolved and their reduced equivalents bud off from twice in two very different clades one in the acoelo- hydranths, hydrorhizae, hydrocauli or hydrocladia. mates, the Cnidaria and one in the Bilateralia the Hydroidomedusae colonies have usually a Endocnidozoa! reduced size most of them do not exceed a few cen- timetres to a few decimetres (i.e. Cladocarpus lig- nosus 70 cm); the hydranths are usually very tenu- GENERAL MORPHOLOGY OF HYDROIDS, ous not exceeding a few millimetres, but there are MEDUSAE AND SIPHONOPHORES exceptions (i.e. Hydrocoryne miurensis: 6 cm; Cory- (see Thomas and Edwards 1991; Bouillon, 1995; morpha nutans: 12 cm; Monocoryne gigantea: 40 Carré and Carré, 1995). cm; Candelanbrum penola: 85 cm; Branchioceri- anthus imperator more than 2 m). Hydroids Morphology of polyps (Figs. 3, 5-9A,B) General appearance of colonies (Figs. 3 and 4) The hydranths (Figs. 5A: 1-8, 6), Hydroids are generally colonial, bearing numer- The hydranth or feeding polyp, may have various ous individual polyps; some are solitary. Typically, shapes (urn-shaped, conical, club-shaped, cylindri- they are permanently attached to their substrate but, cal, etc.), with specialized zones: exceptionally, they can be pelagic: Climacocodon, Hypostome or proboscis. The apex of hydranths, Margelopsis, Pelagohydra, and the Porpitidae. Soli- above the tentacles when these are present, is differ- tary hydroids settling on hard substrates have a basal entiated into a hypostome or proboscis. Hypostomes disc fixing them to their support, those settling on are mostly either conical or dome shaped, rarely soft substrates have a pointed base and filamentous peduncled (Eudendriidae, Campanulariidae), always rootlets; both types of basal structures support a bearing a terminal mouth. The hypostome and the pedicel or hydrocaulus bearing a body, or hydranth, surrounding tentacles play an important role in feed- with an apical mouth normally surrounded by tenta- ing and in the first stages of prey ingestion. In the cles. In colonial forms, the basal area develops a Cladonematidae the ectoderm of the hypostome is system of hollow tubes, the stolons or hydrorhizae, glandular and furrowed by a preoral cavity. A preo-

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ral cavity of very different origin is also observed in spirally arranged cnidocyst clumps (e.g. Margelop- the Bonneviellidae, certain Tubulariidae and some sis and some Leptomedusae). Bimeria. -filiform: thread-like straight tentacle, lacking Gastric column. The gastric column is the main prominent cnidocyst clusters, the cnidocysts appear- part of the hydranth. It is simple, internally not ing more or less evenly distributed (e.g. the Filifera divided by septa, as it happens in the other cnidari- and the majority of Leptomedusae polyps). an superclasses, but in certain species the endoderm -monilifiliform: with dispersed small isolated may present folds and villosities increasing the clusters of cnidocysts on the adoral side of the ten- absorption surface (i.e. Bonneviella, Candelabrum, tacle and with a continuous band of cnidocysts along Clava, and Koellikerina). It bears tentacles in some the aboral side (e.g. aboral tentacles of Tubulariidae) groups. Anthomedusae, Limnomedusae, and some -moniliform: with cnidocyts arranged in a termi- Leptomedusae often differentiate medusary buds nal capitation and in rather regularly spaced con- and gonophores at this level. The different steps of spicuous clumps or bands of tall epidermal cells extracellular digestion and, according to species, bearing cnidocysts (e.g. Asyncoryne, Euphysa). intracellular digestion, take place in this zone too. In -pseudofiliform: tentacles with cnidocysts scat- certain species, the contracted gastric column has a tered in a relatively low epidermis along the adoral lateral expansion opposite the hydrocaulus (see Sec- side and a concentration of cnidocysts in tall epidermis tion below) forming the abcauline sac or abcauline on the aboral side (e.g. oral tentacles of Tubulariidae) caecum. In the Haleciidae, Plumulariidae, and Syn- -ramified capitate: branched tentacles with a cap- theciidae, the gastric endoderm is differentiated into itation on each branch (e.g. Cladocoryne). two zones, the oral digestive one rich in glandular -semifiliform: tentacle with a capitation stretched cells and digestive vacuoles, and the aboral non- towards the aboral side (e.g. Pennaria, Paracoryne). digestive one. -semimoniliform: tentacle with a large capitation Sphincter. The sphincter is a limited aboral por- and numerous small cnidocyst clusters on the adoral tion of the hydranth. In the Anthomedusae polyps side (e.g. Odessia). and in some Leptomedusan ones (e. g. Haleciidae, A single polyp sometimes possesses different Eirenidae, etc.) the sphincter is usually represented tentacle types (Cladonema, capitate and filiform; by a zone at the base of the hydranth, deprived of Euphysa, capitate and moniliform; Cladocoryne, tentacles, rich in muscular elements, whose endo- capitate and ramified capitate; Pennaria, capitate derm, deprived of digestive inclusions, is formed by and semifiliform). chordal cells. This region of reduced metabolic Almost all hydranths have an oral tentacle circlet. activity is interposed between the gastric column Exceptions are atentacled hydranths (e.g. Craspeda- and the pedicel; its function is to isolate the column custa, Limnocnida, Protohydra, Rhaptpagis) and to the rest of the gastrovascular system so to allow those with a proboscis (e.g. Sphaerocoryne). Aboral localised digestion of prey and avoid the introduc- tentacles, when present, can be either scattered or in tion of too large food items to the lumen of the one or several whorls. In exceptional cases tentacle stolonal system. In the Tubulariidae, a cushion of arrangement is asymmetrical (e.g. Monobrachium, special endodermal cells projects into the basal part Proboscydactyla, Zanclella). The number of tentacles of the gastral cavity, functioning like a sphincter. varies greatly, mostly oscillating between 8 and 50, Tentacles. (Fig. 5A: 1-8, 7A) Tentacles are the sometimes less, exceptionally the number of tentacles most characteristic hydranth structures; they vary in is much higher, as in some solitary polyps (e.g. Mono- type and structure according to the mode of distrib- coryne 110; Branchiocerianthus imperator 480; Can- ution of cnidocysts on their surface. delabrum capensis 400 to 600; Candelabrum penola The main types are: 330.000!). In some Leptomedusan hydroids the bases -acnide: sensory tentacle deprived from cnido- of the tentacles are connected by an intertentacular cysts (e.g. certain proximal tentacles of the web (or umbrellula). Corynidae and Cladonematidae). -capitate: tentacle or nematophore with a distinct Stolonal system (Fig. 3). large capitation (a knobbed end, or acrosphere), The hydrorhiza. Colonial forms are attached to richly armed with cnidocysts (e.g. the Capitata). the substrate by coenosarcal tubes usually contained -cateniform: tentacle with cnidocysts in a distinct in a perisarc sheath: the hydrorhiza. The stolonary large terminal capitation and with numerous small, gastric cavity is usually simple but is sometimes

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divided into several canalicules limited by endoder- terminal. Below this hydranth there are a growth- mal cells (i.e. Asyncorynidae). The hydrorhizal zone and a budding zone. Buds are formed in the stolons grow on the substrate, increasing the colony budding zone and the hydrocaulus grows above surface and, in many species, the medusary buds and them, so that the youngest bud is at the base of the the gonophores develop from their surface. Finally, stem and the oldest at the top. Each bud then grows under unfavourable conditions, the hydrorhizal tis- in a similar manner and several degrees of branch- sues can become dormant, resorbing the rest of the ing may occur each branch topped by its oldest colony. Hydrorhizae survive until proper conditions hydranth, e.g. most Anthomedusan colonies: Euden- prevail again, then regenerating new colonies. drium, Bougainvillia, Pennaria. Some hydroid species are solitary and devoid of - Monopodial growth with terminal growing both sphincter and hydrorhizal system; they fix to point. There is no terminal hydranth, but the stem is substrates by an adhesive gelatinous or glandular topped by a growth-zone. Below the growth-zone is disk (Hydra, Acaulis, Acauloides, etc.) or by an the budding zone, so that the oldest hydranth is at anchoring system of rootlets (Corymorpha, Cande- the base and the youngest one just below the tip, e.g. labrum, Branchiocerianthus, etc.). Plumulariidae, most Sertulariidae. Colonies growing horizontally, with hydranths - Sympodial growth (cyme). The first hydranth is arising separately and directly from a common terminal, but it has no growth-zone and the stem hydrorhiza, with or without a pedicel, are termed does not elongate further. A budding zone below the stolonal, or hydrorhizal. Erect colonies grow verti- hydranth produces a branch which grows beyond the cally, producing upright hydrocauli bearing more first hydranth and is topped by the second hydranth. than one hydranth. Continuation of this process produces a ‘false axis’ Hydrocaulus. (Figs. 3, 9A-B) The hydrocaulus (the sympodium), which is in reality formed by suc- is the main stem of a hydroid colony, arising from cessive branches (the podia), e.g. Haleciidae, Cam- the hydrorhiza. It is simple (often called pedicel) in panulinidae, Campanulariidae. Such a stem is usual- solitary or stolonal forms and in some unbranched ly zig-zag or geniculate. colonies (e.g. Antennella); in most colonial forms, stems build up complex and varied colony forms: Perisarc: Stolons and stems arborescent, bushy, cymose, flabellate, flexuose, The perisarc completely surrounds the stolonal pinnate (alternate or opposite), plumose, racemose, system, the hydrocaulus and the hydrocladia of almost spiral, straight (biseriate or uniseriate), whorled or all hydroids, with the exception of some epizoic, par- verticillate etc. Hydranths can be either on the asitic or pelagic species, which are naked. Perisarcal hydrocaulus (cauline hydranths) and on all the structures are complex, being mainly composed of branches, or exclusively on the branches, the most chitin and proteins; they are sometimes associated terminal ones being called hydrocladia. The hydro- with calcareous elements (coenosteum). The perisarc caulus perisarc is usually divided into segments, or serves for attachment, protection and support. internodes, by partitions or nodes. In some Lep- Generally present as distinct tubes running over tomedusae polyps, each internode may give origin the substrate, the stolons forming the hydrorhiza are to nematothecae and to one or two hydrothecae or sometimes fused or anastomosed in a complex and hydrocladia with great regularity, each arising from dense network covered with the common ectoderm a projection shoulder or apophysis. The hydrocaulus of the colony. The perisarc covering the upper face may be composed of a single coenosarcal tube of the stolons may even disappear, the hydrorhiza (monosiphonic) or comprising two or more being then covered by naked coenosarc. The basal coenosarc tubes and form a composite stem struc- perisarc layer may produce spines which penetrate ture, each tube retaining its perisarc (polysiphonic or the coenosarc, reaching the surface (e.g. Hydractini- fascicled). The coenosarcal cavity of the hydro- idae). The genera Hydrocorella and Janaria are sim- caulus is usually simple but it may be divided by ilar to Hydractinia, but their skeleton is impregnat- endodermal canals in many Corymorphidae and ed with calcium carbonate, as it is in the Millepori- Tubulariidae. dae and Stylasteridae. In some erect flabellate The form of erect colonies depends primarily on species of Anthomedusan polyps, such as Solande- three main types of growth. (Figs. 9A, B). ria and Pseudosolanderia, the perisarc forms a - Monopodial growth with terminal hydranth strong internal chitinous skeleton supporting the (raceme). The first hydranth on the hydrocaulus is colonies. Pelagic hydroids (e.g. Margelopsis,

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Pelagohydra, Climacodon) are usually deprived with a pseudohydrotheca, not homologous to peris- from perisarc, however the Porpitidae have a chiti- arcal hydrothecae but similar in function (Thamnos- nous float or pneumatocyte of perisarcal origin. The toma russelli, Bimeria vestita, Bougainvillia ectoderm sometimes gives rise to numerous digita- ramosa, Leuckartiara octona, Clathrozoella drygal- tions or villosities perforating the periderm and tak- skii etc.). On the other hand, many Leptomedusae ing part in respiratory exchanges. polyps have very reduced thecae or even lack them The chitinous perisarc of Anthomedusae polyps (e.g. Halecium, Melicertum octocostatum, Eutima generally does not grow over the level of the gracilis, Octorchis gegenbauri, Helgicirrha hydranth sphincter, and the peduncle of medusa schulzei, Eugymnanthea, etc.). buds (except in Halitiara, Merona, Rhysia and In certain colonial forms (Limnocnida, Trichydra), but these are covered by a mucopro- Craspedacusta), the perisarc is reduced to the basal teinic periderm. region, and is even lacking in some solitary species Hydrothecae (Figs. 4, 5A: 9-20, 5B: 1-11). In such as Hydra and Protohydra. In such cases, the Leptomedusae polyps, the chitinous perisarc forms a hydranths are surrounded only by a mucoproteinic solid theca around the hydranths (the hydrotheca), periderm. the reproductive organs (the gonotheca), and the Nematothecae. (Figs. 7C: 1-7, Fig. 8). The nema- protective polyps, or dactylozoids (the dactylotheca tothecae contain the protective nematophores, they or nematotheca). may be sessile or pedicellate, one-chambered The hydrothecae usually have a chitinous (monothalamic) or two-chambered (bithalamic), mov- diaphragm or an annular thickening at their base, able or immovable. They are either irregularly isolating the inner space between the coenosarc arranged on the colony or grouped in a very distinct and the perisarc from the outside water. The manner around the hydrothecae, as in the Aglaopheni- diaphragm is perforated, so to allow the passage of idae, the Halopterididae, the Kirchenpaueriidae and coenosarc. In the Syntheciidae, the Sertulariidae the Plumulariidae. In these families, each hydrotheca and the Plumulariidae the hydranth has a definite has typically one basal (median inferior) nematotheca, floor of perisarc with an asymmetrical or symmet- and two lateral ones, one on each side. There may also rical hole or hydropore. The hydrothecae may be be one or two nematothecae above the hydrotheca sessile or supported by a pedicel; sessile ones can (superior nematothecae) and some on the hydrocaulus be partly or wholly adnate to their support by their (cauline nematothecae) and on the hydrorhyza. adcauline side, the abcauline one remaining free. Gonothecae (Figs. 7B: 1-14, 8: A-D, H, I).The The hydrothecal opening can be either unprotected gonothecae are the chitinous structures surrounding or provided with either a single lid or an opercu- the blastostyles or the gonophores, they are typically lum, closing over the contracted hydranth. The closed on top, until the developing embryos are ready operculum may be composed of several triangular to be released, they are often operculate. In some Lep- flaps sharply or not sharply demarcated from tomedusae with fixed gonophores the gonothecae hydrotheca. The hydrothecal rim may be cusped or have modified structures protecting the planulae until even. The shape of cusps is often species-diagnos- liberation, the “marsupium”, formed by apical tic. The hydrothecae often present internal cusps gonothecal expansions enveloping the planulae and and one or more intrathecal septa. Hydrothecae forming an incubating chamber (e.g. some Diphasia may have alternate or opposite arrangement on and Thuiaria). The gonothecae may be simple or stem and branches; single or in pairs, sometimes aggregated either into compound bodies “coppiniae”, they are said subalternate or subopposite when “glomulus” or “scapus”, or protected by special out- there is an intermediate arrangement. Hydrothecae growths formed by the hydrocladia or modified often regenerate, the new hydrotheca developing hydrocladia: phylactocarps, corbulae. They often pre- within the older one, repetition of this process is sent a sexual dimorphism, the gonothecae being quite common in some families (e.g. Haleciidae, some different in male or female gonangia. Lafoeidae, some Sertulariidae). The presence of a hydrotheca is a useful feature Polymorphism (Fig. 3) to identify Antho- and Leptomedusae polyps, respectively known as athecate and thecate. Such Hydroid colonies outstand by their polymor- identification, however, is not always easy. On the phism. In addition to the nutritive polyps (hydranths one hand, some Anthomedusae polyps are provided or gastrozooids) they often include: special sexual

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polyps, the gonozooids, bearing medusae or medu- The tentacles (Fig. 9C, 10, 12, 13) soids in various stages of regression; protective polyps usually lacking mouth and largely provided The free rim of the umbrella usually bears mar- with cnidocysts, the dactylozooids or machozooids ginal tentacles, often cirri of different kinds, usually (of several types: tentaculozooids, spiralozooids, associated with sensory cells and sense organs. In nematophores or sarcostyles); protective individuals most medusae the tentacles are peripheral, in the not provided with cnidocysts, but constituting chiti- Laingiomedusae and the Narcomedusae they are nous spines, the acanthozooids. inserted on the exumbrellar surface. Tentacles show a great diversity in form and number. They are Medusae (Figs. 9C, 10-13). called solid, when their endoderm is formed by a core of single vacuolated cells (chordal cells); or The bell (Fig. 10A, B, 11A) hollow, when containing an extension of the circular canal (tentacular cavity) or when the endoderm is Hydrozoan medusae show essentially a composed of several peripheral rows of cells coming tetramerous radial symmetry. Their main body, the in juxtaposition, the cavity being lost or only very swimming bell or umbrella, generally recalls the partly retained at the tentacle base. Tentacle num- shape of a mushroom, a bell, a disk, a cone, a mitre bers may vary from zero to several hundreds (up to etc., with considerable variation in form between 640) according to species; their number does not species. The top of the umbrella is usually flattened, necessarily equal the basic number of radial canals but some species may have a mesoglean thickening (4), or a multiple of it, but is usually not fixed, it forming the apical projection or process, or may may be even or uneven and is generally increasing contain an apical canal (or umbilical canal) which is with growth. Tentacles are armed with cnidocysts, the remaining of the link between the gastric cavi- formed either at the level of tentacular bulbs, or in a ties of the mother hydroid and the medusa. The specialised marginal cnidocyst ring, when it exists. umbrella may also have exumbrellar cnidocyst In species with marginal bulbs, the development of patches, bands, or pouches (e.g. Zancleidae). Large a tentacle is always preceded by the formation of a hydromedusae can have a subumbrellar gelatinous tentacular bulb. projection (e.g. Aequorea). The umbrella of There are different tentacle types according to Hydroido- and Automedusae generally measures the mode of distribution of the cnidocysts (see between 1 mm and 50 mm, but in numerous species polyps and glossary). Cnidocysts may be disposed the size may be greater, reaching 100 to 200 mm in a terminal button (capitate tentacles), in rings (Aequorea) and even exceptionally 400 mm of (moniliform tentacles), in spirals, or even irregular- diameter (Rhacostoma atlanticum). The main part ly along the tentacles (filiform tentacles). In some of the umbrella volume is occupied by a gelatinous groups, tentacles bear specialized pedicellate and mass, the mesoglea, the jelly of the jellyfish, which contractile stinging buttons, the cnidophores (e.g. confers form and buoyancy. The convex, upper Zancleidae). Tentacles are generally simple, but they (aboral) umbrellar surface is called the exumbrella; can be bifurcated, one branch being armed with the concave, lower (oral) surface is termed the sub- cnidocysts and the other one bearing adhesive umbrella; the space enclosed by the umbrella is the organs (e.g. Cladonema, Eleutheria, and Staurocla- subumbrellar cavity. dia). When the tentacles are not in contact with the radial or circular canals they may present a tentacu- The velum (Figs. 10, 12, 13) lar endodermal root expanding in the umbrellar mesoglea (e.g. Blackfordia, many Narcomedusae). The opening of the subumbrellar cavity is nar- Medusan species usually have tentacles of one rowed by a muscular horizontal marginal diaphragm, kind; in a few species, however, two kind of mar- or velum, living only a central circular aperture, the ginal tentacles may be found (e.g. Liriope). velar opening. The velum plays an important role in medusan swimming; in certain medusae it is strongly The bulbs (Figs. 12-13) developed and even hangs downwards like a curtain (some Trachymedusae); in Obelia it is absent. Two Tentacle bases are usually swollen into an nerve rings are situated at the base of the velum, sep- enlargement, the tentacular bulbs; of various shape arated by the velar mesoglea. and size, they may be simple (bearing one tentacle)

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or compound (bearing two or more tentacles); some- Narcomedusae. The ectodermal statocysts of Lep- times they grow upwards, clasping the exumbrella tomedusae develop in the velum, where they form with exumbrellar spurs; in some groups they may be open or closed pockets or vesicles, characterized by absent (e.g. Calycopsidae, Limnomedusae, Tra- specialised cells, the lithocytes, containing a vari- chymedusae). Not all marginal bulbs bear tentacles; able number of round concretions, called statoliths. some never do, they are called non-tentacular mar- The wall of the statocyst also bears sensory cells ginal bulbs, others will develop tentacles during with long sensory bristles. According to the position growth (developing tentacular bulbs). Tentacular of the medusa, the lithocytes press on the bristles, bulbs may carry ocelli, light-sensitive sense organs. exciting the nerve cells. In some species, tentacular bulbs have adaxial The ecto-endodermal statocysts have a different excretory pores, located or not at the apex of a papil- structure. They are constituted by didermic clappers la; sometimes the same structures can be found at issued by the marginal circular canal in the fashion the level of the circular canals. During development of a tentacle, and not by the velar ectoderm. The dis- of species with more than 4 tentacles, the first tenta- tal part of the clapper contains one or two endoder- cles to be formed are perradial, then interrardial, mal cells provided with concretions (lithocytes). At adradial and finally subradial; but after the adradial the base of this club, ciliated sensory cells can be tentacles are formed the mode of tentacle appear- recognized. According to the inclination of the clap- ance is often irregular. per, they strike the wall of the pocket or vesicle. Ecto-endodermal statocysts may be closed or open. Marginal structures (Figs. 12-13) Cordyli. Ecto-endodermal sense organs in the form of clubs, devoid of statoliths, with or without In addition to tentacles, the umbrellar margin cnidocysts. They are found implanted on the exum- may present other structures: marginal warts or brellar rim of the medusae of the families Hebelli- swellings; sense organs like ocelli, different types of dae, Laodiceidae and Tiarannidae. Their function statocysts (open, closed, ectodermal, ecto-endoder- remains mysterious. mal), and cordyli; small tentacular-like structures, or cirri, usually of two types: spiral or flexile; and, The manubrium (Figs. 10A-B) finally, marginal tentaculae (see glossary). From the centre of the subumbrella hangs, like Sense organs (Figs. 12-13) the clapper of a bell, a tubular or quadrangular pro- jection of various length and form, the manubrium. Ocelli. The eyes, or ocelli, are most developed in The base of the manubrium may be attached either the Anthomedusae. They are also found in some directly to the subumbrellar roof or to a cone-shaped Leptomedusae (e.g. Laodiceidae, Mitrocomidae, thickening of the mesoglea projecting downwards in Tiaropsidae). From the outside, the ocelli appear as subumbrellar cavity, the gastric peduncle. The brown, red, or black spots on the tentacular bulbs or, manubrium may present an apical chamber, or cae- in certain Leptomedusae, under the statocysts. Ocel- cum, extending in the mesoglea, and/or perradial or li, according to the species, have a more or less com- interradial manubrial pouches increasing the gastric plex structure. The eyes of Eleutheria, here consid- surface and often bearing the gonads. The manubri- ered as typical, are composed of a cupule constitut- um contains the gastric cavity that extends proxi- ed by intermixed ectodermal pigmented cells and by mally into the radial gastrovascular canals and opens nerve cells, with a central crystalline formation. The distally, inside or outside the subumbrellar cavity, by whole is situated above the nettle ring, in the ecto- the mouth. The manubrium wall may be attached to dermal layer from which it originates. In Tiaropsis, radial canals and subumbrella by mesenteries of var- the pigment cells are endodermal. ious lengths. Statocysts (lithocysts or otocysts). These organs of orientation and equilibrium are lacking in the The mouth (Figs. 11B, 12J) Anthomedusae, but are present in the hydroids of Euphysa. They may be classified in two categories, The mouth margin may be simple and circular or those exclusively ectodermal, proper to Leptome- may have lips or lobes. The latter can be short or dusae and those of ecto-endodermal origin, found in long, simple, folded or crenulated to varying Limnomedusae, Actinulidae, Trachymedusae, and degrees, with or without a cnidocyst armature. The

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mouth margin may have simple or branched oral either cylindrical, covering all its surface, or interra- tentacles. dial, adradial, or perradial. Fertilisation is usually external, with free spawning of both males and The gastrovascular system (Fig. 10) females. In a few species internal fertilisation may occur: males spawn freely in the water, the sperms The gastric cavity, the radial canals, the circular reach the eggs while still in the female gonad and fer- canal and the tentacular canals, when they exist, tilise them there. The resulting planulae are then lib- form the gastrovascular system which serves for the erated through the velar opening (e.g. Turritopsis, digestion and distribution of food and for the circu- Eleutheria). lation of oxygen, waste, cnidoblasts or even of gametes. The radial canals connect, through the Siphonophores (Figs. 14-15) mesoglea, the gastric cavity to the circular canal which runs all along the marginal rim of the umbrel- Colonial, pelagic, swimming or floating Hydrozoa la; they are generally four, but can be more numer- (except the deep-water, epibenthic, Rhodaliidae), ous, sometimes more than one hundred (e.g. 250 in forming highly polymorphic modular colonies of Aequorea pensilis), usually even in number. The polypoid and medusoid zooids attached to a stem or radial canals may be simple or branched, sinuous, stolon supported by a floating and swimming system. jagged, denticulate, with diverticula etc. They usual- Polypoid zooids of several sorts: pneumatophore, ly develop centrifugally from the base of manubri- gastrozooids, dactylozooids, and bracts. All of them um; a few medusae have nevertheless radial canals usually associated with the gonophores in repetitive arising from circular canal (i.e. Melicertum, Orchis- groups, or cormidia, along the stolon. All polypoid toma). Most of the canals issued from the circular structures without oral tentacles. The part of the stem canal, however, never reach the manubrium, and below the floating system, bearing the cormidia, is form the so-called centripetal canals. The radii cor- the siphosome, usually representing most of animal’s responding to the radial canals are named the per- length. Floating system as pneumatophores and nec- radii, intermediate between them lie the interradii tophores or swimming bells, together forming the and midway between the perradii and the interradii nectosome. The complete and fully developed animal are the adradii. The circular canal is usually simple is referred to as the polygastric stage. and narrow; occasionally it is not hollow and con- Histologically, the polypoid and medusoid sists of a solid core of endodermal cells (Lain- zooids resemble the corresponding types of giomedusae, Proboscydactyla). In the Narcome- Hydroidomedusae. dusae, the circular canal, when present, follows the exumbrellar lobes and the peronia, forming what is Polypoid structures called the peripheral canal system and the peronial canals (see glossary). The pneumatophore. The pneumatophore, or api- Crossing the mesoglea, a monostratified mem- cal float, is present only in the Cystonectae and brane, the “cathamnal” or endodermal lamella, Physonectae. It is of larval ectodermal origin and interconnects the radial canals and, like these, con- consists of an external wall or pneumatocodon, and nects the gastric cavity with the circular canal. It an inner ectodermal wall, or pneumatosaccus, lining delimits two mesoglean layers, one thin, subumbrel- the float cavity, typically lined by a chitinous layer. lar (inner mesoglea), the other well-developed, The pneumatosaccus differentiates the gas gland or exumbrellar (outer mesoglea). pneumadenia, containing branched giant cells of unknown function. The pneumatophore may be of The gonads (Figs. 10, 11C) complex structure, its cavity may be divided in chambers by vertical septa. In most species the cav- The sex cells may develop and ripen either on the ity of the float communicates with the exterior by an manubrium, or on the radial canals, or on both. apical pore. “Gonads” position and form are of great importance The gastrozooids. The gastrozooids, or feeding in medusan classification. When on the radial canals, and digestive polyps, lack oral tentacles but have a gonads may or may not completely surround the long contractile basal trailing tentacle bearing later- canals, be oval, globular, linear, folded, sinuous, sac- al contractile branches or tentilla; they have usually like, etc. When on the manubrium, they may be a large basal thickening rich in cnidoblasts. The

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endoderm of the hypostomial region presents The nectophores. The nectophores or swimming numerous folds rich in various gland cells. The gas- bells correspond to reduced medusae, they possess trozooids are the only members of the colony capa- an umbrella, a subumbrellar cavity or nectosac, a ble of ingesting food, the extracellular digestion velum (ostium), an endodermal lamella, 4 unequal occurs in their cavity and their endodermal layer is radial canals, a circular canal, 2 nerve rings, striated the place of primary intracellular digestion. The subumbrellar and velar muscle. The nectophores are feeding behaviour of the siphonophores has not been deprived of manubrium, mouth, tentacles and elabo- studied much (see Biggs, 1977; Carré and Carré, rated visible sense organs. They are very muscular 1995). and hence have exceptionally good swimming The dactylozooids. The dactylozooids or palpons power. A simple or branched extension of the origi- (= cystozooids or cystons) may bear small basal nal larval gastrovascular system, or somatocyst, unbranched tentacles or palpacles. They have an sometimes containing oil droplets (= oleocyst), runs accessory role in the intracellular digestion and pos- along the dorsal surface of the hydroecium. The sess an apical pore involved in the elimination of point of convergence of the radial canals has often small waste particles, the big ones being eliminated an eccentric position on the nectosac and is usually by the mouth of the gastrozooid; they seem to have connected to the somatocyst by the pedicular (pal- also a sensory function. The dactylozooids are leal) canal. In most nectophores, the somatocyst absent in the calycophorans except Stephanophyes, develops at the origin of the pedicular canal. The and in the cystonects, in the physonects they are sev- nectophores of Physonectae present around the stem eral per cormidium. apico-lateral processes or apical wings which are The bracts. The bracts are usually lamellar, they sometimes bordered by cross ridges or lateral wings, are limited by an ectodermal layer, enveloping a their aboral region present a specialized area, or thick mesoglea containing an endodermal blind thrust block, separating the apical wings and abut- canal (bracteal canal), and they have a protective, ting against the nectosomal stem. floating and sensory function and may contain meta- Calycophorae usually have only one or two nec- bolic reserves. They are absent in cystonects, leaf- tophores, an anterior and a posterior one; their nec- like with a simple bracteal canal in physonects, in tophores have thin extensions, or basal lamellae, the Athorybiidae the bracts have a swimming func- below the ostium of the nectosac, one or more of tion and replace the nectophores, in the Calycopho- these lamellae comprise the mouth plate. ra they are more complexly organized and have a Gonozooid - sexual medusoids. The gonozooids branched bracteal canal, except in the Hippopodi- of siphonophores may be represented by a single idae, where bracts are absent. Their medusoid or gonophore or by clusters of gonophores attached on polypoid origin is still discussed. a branched stem or gonodendron (= blastostyle). The siphosomal stem. The siphosomal stem or There may be several groups of gonophores per stolon is issued from the nectosome out of a more or gonozooid. The gonodendron is usually associated less developed gutter-like furrow, the hydroecium, with a specialised palpon or gonopalpon. The which gives a bilateral symmetry to the nectosome, gonophores are sexual medusoids, their budding protecting the siphosomal budding area and in occurs like in other Hydoidomedusae with the for- which the stolon itself may sometimes withdraw. mation of a medusary nodule, and they have typical The stolon has the usual hydrozoan coenosarcal medusan characteristics; female ones, however, may two-layered structure, separated by a thick mesoglea be deeply modified. Siphonophores may be monoe- presenting radiating septa penetrating the ectoderm. cious or dioecious. The germ cells develop on the In some Physonects the stolon forms a large plate manubrium of the sporosacs or of the eumedusoids, bearing the cormidia. The cormidia are borne on the the latter being rarely liberated. The Physonectae surface of the stolon arbitrarily considered ventral, female gonophores develop only one egg, but their although they may sometimes appear to encircle the cormidia may form a succession of several male or stolon, an optical illusion due to stolon twisting. female new gonophores. Calycophorae gonophores contain several eggs (2 to 30), usually their cormidia Medusoid structures become free as eudoxia, able to form successively several generations of new gonophores during their They are of three sorts: nectophores or swim- free life, with the alternation of male and females ming bells and asexual or sexual medusoids. structures.

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Asexual medusoids. Sterile or asexual medusoids two cycle patterns, depending on the season, one may be associated to the sexual gonophores namely typical and the other where the planula settles and in the Cystonectae and in a few Calycophorae. They directly produces medusae without forming may have a propulsive and floating function. hydranths (i.e. Laodicea indica), or forming a single The survival of isolated zooids seems impossi- hydranth, attached to the gonotheca (i.e. Clytia ble, but the cormidia of most Calycophorae repre- viridicans) etc. The study of Hydroidomedusae life sent real colonial units, breaking loose before the cycles is one of the most promising fields in Hydro- maturation of the gonophores and leading an inde- zoa biology and may give important indications for pendent existence, being then termed eudoxia. the understanding of their evolution. A fully grown siphonophore colony may be con- In the Actinulidae and the Automedusae, devel- sidered as enlarged, larval nurse carriers (his pae- opment is direct, the embryo giving rise directly to a dophore) that itself does not become sexually medusa without the presence of a true larval hydroid mature but bud off adults, medusoid gonophores stage; in the Narcomedusae the embryonic stages (Totton, 1965). may be external parasites of other animals. Siphonophores are carnivores, feeding mostly on The Polypodiozoa are represented by a single small crustaceans and larval fish, but the largest species, Polypodium hydriforme, which is the only colonies may feed as well on bigger preys like: poly- known metazoan adapted to intra-cellular para- chaetes, pelagic molluscs or tunicates, aduldt fishes sitism. Polypodium has a unique life cycle, having a or even other siphonophores. Some fishes feed on succession of a free-living stage and of an intra-cel- siphonophores, in Mediterranean Forskalia for lular parasitic stage of some Acipenseridae and instance is the prey of fishes of the family Scombri- Polyodontidae eggs. dae especially Teytragonorus cuvieri himself toxic for man. Sexual reproduction (Figs. 16-19).

Sex determination DEVELOPMENT Hydrozoan are mostly dioecious except most of the Siphonophores and a few other monoecious Life cycles (Figs. 16-19, 156) Hydroidomedusae species. Simultaneous or succes- sive hermaphrodites occur rarely (e.g. Amphogona, Not all the Hydrozoa present the classical life Eleutheria, certain Hydra and Tubularia, Eudendri- cycle usually described in the text books, i.e.: fer- um motzkossowskae, some Aglaopheniidae, some tilised eggs, planula, larval hydroid, adult medusae, Clytia). In Plumularia setacea the colonies are eggs and sperm, fertilised eggs and so on. This cycle recorded both monoecious and dioecious. The is anyhow characteristic, as far it is known, of most mechanism of sex detemination is not well known in Hydroidomedusae with the exception of the the Hydrozoa. In general it is admitted that sex Siphonophora, where the planula gives rise to spe- determination is genetic (see Tardent, 1985; Little- cialized larvae (i.e. calyconula and siphonula) field, 1994) but in several cases (e.g. Hydra, Clytia), developing directly into the siphonophoral adult sex determination appear ruled by environmental polygastric stage. The above described conditions, mainly by temperature and appears Hydroidomedusae cycle may present several modi- unstable (see Carré and Carré, 2000). In Hydra mul- fications. The most important one is the suppression tiple genes are thought to influence sex with the of the medusa stage, a feature of almost half of the degree of manifestation of either sex being dose- species. Even when medusae are not liberated, how- dependent. ever, most gonophores still retain a medusan archi- tecture. Other life-cycle modifications include, for Gametes and fertilisation instance: the presence of an embryonic encysted The gametes of the Hydrozoa are generally of stage (e.g. Hydra, Margelopsis, Paracoryne) which ectodermal origin, but in certain species they may be is presumably a more common event than currently formed in the endoderm (e.g. Actinulida, Nannoco- believed; the transformation of the planula into a ryne, Pegantha clara, Polypodium and Solmaris single planktonic polyp that buds a single medusa flavescens). that, during its formation, completely resorbs by the In most medusal forms, ripe eggs are shed hydroid (i.e. Eirene hexanemalis); the existence of immediately in the external medium. Nevertheless,

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there are forms in which the eggs remain either phosing into a polyp. Planula encystment is proba- fixed on the gonads, or in the subumbrellar space bly a very common event in the development of (e.g. Corymorpha, Hybocodon), where they are hydroids with fixed gonophores, since many species fertilised and develop into planulae. In the species reproduce sexually at the end of the favourable sea- with reduced medusae, the eggs remain most often son and then disappear. Sexual reproduction, in inside the gonothecae, where fertilisation occurs these cases, is not followed by an increase in popu- and development proceeds to a very advanced lation size but, instead, by the disappearance of all stage, from planulas to even young hydranths (e.g. active stages. It is then reasonable to assume that Cordylophora, Halecium, Clava, etc ). Brood planula encystment occurs. chambers can be present both in the medusa stage In the Siphonophora, the planulae remain pelag- (Eleutheria) or in the hydroid stage (Fig. 8) the ic and are without the cellular differentiation typical marsupium of some sertulariids, other species pro- of the other Hydroidomedusae planulae. They have duce a mucous mass, the acrocyst, where develop- a very short lifetime, usually much less than 24 ment is completed (e.g. Calycella syringa, Dyna- hours, metamorphosing rapidly into more spe- mena pumila, Opercularella lacerata, Thuiaria cialised pelagic larvae, the siphonula (usually with a arctica etc.). Gonothyraea species have “meconi- primary or larval aboral bract and a primary oral dia”, reduced sexual stages disengaged from the gastrozooid) in the Physonectae, and the calyconula gonothecae as cryptomedusoids but remaining (with a unique latero-aboral, usually deciduous, lar- attached to the blastostyle by a slender peduncle. val nectophore and an oral primary gastrozooid) in The embryos develop inside these reduced the Calycophorae, both larval types developing into medusae till planula liberation. the adult sexual form or polygastric stage. Male spawning normally occurs in the water and The Automedusae do not present a hydroid stage no copulation is known in the Hydrozoa. The exis- (hypogenetic) and possess either direct or parasitic tence of sperm attractants, produced by the eggs, has development (certain Narcomedusae). They develop been first demonstrated in the Hydrozoa (Miller, into young medusae either directly or through inter- 1972). Fertilisation can be internal (when the sperms mediate tentaculate, post-embryonic stages inappro- reach the eggs while these are still on the female) or priately called “Actinulae” that, in fact, are not external (when sperms and eggs are shed in the polyps but larval medusae. Their planulae have a water and meet there). simple embryonic didermic cellular organisation Gastrulation lead to the formation of a diblastic lacking the specialised neural and glandular cells embryo: the planula. This embryo presents already a characterising most Hydroidomedusae. complex structure, very differentiated but also very different from one group to another. Asexual reproduction (Figs. 16-17, 20-22). Fully-developed planulae lead a free life of vari- able duration, from a few hours to several days, then The Hydrozoa have several types of asexual attach by the anterior pole, generally enlarged, and reproductive stages, asexual reproduction being one glandular, to an appropriate support, collapse, and of the main characteristics of the group. The Tra- give rise to a primary polyp. The anterior region of chymedusae and the Actinulidae, however, do not the embryo is transformed into the fixation sole. The present asexual reproduction. The main patterns of median zone, by evagination, becomes the primary asexual reproduction are: stolon, whereas the posterior region constitutes the Fission. Certain hydranths and a few hydrome- primordia of the first hydranth. Sometimes, several dusae may also reproduce by longitudinal or trans- polyps bud off from a single planula (e.g. Oceania versal fission (i.e. Protohydra, Hydra, the medusae armata, Mitrocoma annae). of Cladonema and Clytia). In certain hydroids, the planula does not immedi- Podocysts or propagules (Figs. 17-22). Under ately leave the gonophore, but continues its devel- adverse ecological conditions, some hydroid opment in it, either partially, producing an interme- colonies isolate fragments of hydrocauli, hydrocla- diate stage, the actinula (i.e. Tubularia, Myriothela), dia or stolon, enveloped by perisarc, ensuring the or completely, a normal polyp living the gonophore propagation and direct dissemination of the species (certain gonophores of Cordylophora). Some but that may also act as resting stages or cysts. hydroids have zooxanthellate planulae (e.g. Haleci- Budding of planula-like bodies, or frustules, of um) that can survive for months before metamor- different types (Figs. 17, 22). This is more common

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in hydroids, but can occur exceptionnaly also in homologous, to the subumbrellar cavity and velum some medusae (i.e. Eucheiliota paradoxica). of the Hydroidomedusa; during embryonic develop- Resting stages or cysts (Figs. 22D, 45H). Encyst- ment and medusa budding, the primary marginal ed embryos (from zygote to later stages) and planu- tentacles are always formed before the subumbrellar lae, can withstand adverse conditions by encyst- cavity and the gastrovascular system. ment. Cysts are presumably much more common In many Hydroidomedusae, the medusae develop than supposed, presently they are mainly known only incompletely and remain attached to the polyp from solitary forms like Climacodon, Corymorpha, colony as fixed gonophores (Figs. 20-21). Several Fukaurahydra, Gonionemus, Hataia, Margelopsis, stages of medusa reduction have been recognised Moerisia etc. and in freshwater species as and several types of fixed gonophores may be dis- Craspedacusta, Limnocnida, Hydra etc. They are tinguished: less common in colonial forms (present in Paraco- Eumedusoids. Medusa almost complete, with ryne) where the fragments of perisarc-covered radial canals, a subumbrellar space, sometimes with hydrocaulus or stolons play the same role. Cysts a manubrium, but generally without tentacles, sense may survive sometimes several years (e.g. organs, and velum; some have a free pelagic life. In Craspedacusta, 40 years). the eumedusoids, “gonads” are on the manubrium Polyp budding, leading either to colony forma- when Anthomedusae (i.e. Pennaria, Hydractinia- tion, or to a population increase in solitary forms. Stylactis, Tubularia), on radial canals when Lep- Exceptionally, some medusae produce polypoid tomedusae (i.e. Eugymnanthea, Orthopyxis). structures (i.e., Bougainvillia platygaster, Probosci- Cryptomedusoids. More regressed stages, not dactyla ornata, Teissiera medusifera, Zanclea presenting radial canals any more, but exclusively medusopolypata). an endodermal lamina homologous to the gastroder- Medusa budding, giving rise to the free sexual mal lamella: the umbrella endoderm; still provided phase, the medusa, or to sessile, reduced with a reduced subumbrellar space, or without any gonophores. Some medusae multiply by budding, space which is then represented only by an ectoder- which may take place at various levels: on the mal layer, the internal ectoderm (e.g. Cladocoryne manubrium (i.e., Dipurena gemmifera, Limnocnida floccosa, Clava squamata, Coryne muscoides). tanganyicae, Cunina fowleri and C. frugifera), on Heteromedusoids. Highly atrophied fixed the radial canals (i.e., Eucheilota paradoxica, Pro- gonophores, devoid of umbrellar endoderm, but still boscidactyla ornata, Kantiella enigmatica), on the possessing an internal ectoderm (e.g. Sertularia tentacular bulbs (i.e., Coryne prolifera, Hybocodon argentea, Laomedea flexuosa, Kirchenpaueria ech- prolifer, Niobia dendrotentaculata), on the exum- inulata). brellar rim (i.e., Eleutheria dichotoma) or on the Styloids type I. The most regressed gonophores subumbrellar rim (i.e., Eleutheria claparedei). In without internal ectoderm, or umbrellar endoderm, a the medusae of Clytia mccradyi and Eirene simple evagination of the two constituting layers, elliceana, the gonads produce blastostyles giving the genital elements accumulating between both lay- rice to medusary buds. ers around a central or lateral axis, the spadix (e.g. In the Hydroidomedusae, whether the medusary Dicoryne, Eudendrium, Bimeria, Cordylophora). buds derive from polyps or from medusae, they Styloids type II. The regression is sometimes develop in remarkably similar ways characterized even more complete, with no trace left of by the presence of a didermic medusary nodule. gonophores, the gonads developing either in the In certain Hydroidomedusae belonging to the ectoderm (e.g. Hydra, Gymnogonos, Hydrodendron) families Bougainvilliidae (i.e. Lizzia blondina, or in the endoderm (Actinulidae). A given species is Bougainvillia niobe), Hydractiniidae (Hydrac- not characterised by a single type of gonophores, the tinia minima), and Rathkeidae (Rathkea octop- gonophores of one sex being often different from unctata), the medusary budding takes place by those of the other. In many cases, a gonophoral sex- peculiar and remarkable processes, being exclu- ual dimorphism is thus observed. sively ectodermic. Swimming gonophores (Fig. 21D). Sometimes In the Automedusae, medusa budding occurs strongly reduced medusa stages (cryptomedu- without medusary nodule, the subumbrellar cavity soids and perhaps heteromedusoids) may become and velum are formed by folds and deepening of the secondarily free gamete carriers again. They have oral embryonic ectoderm and are analogous, but not gonads on the manubrium (spadix) both in the

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Lepto- and the Anthomedusae. Swimming either toward the base of the cell, or laterally. In the gonophores, termed swimming sporosacs, have Capitata, for example, the most basal region of the been reported for Dicoryne conybeari in form of cnidocyts, or cnidopod, contains a bundle of fibrils, flagellated gamete-carriers, deprived of any connecting the capsule to the mesoglea. The apical medusan structure. Several Leptomedusan species region of the cnidocyte bears an eccentric, birefrin- (of the genera Amphisbetia, Anthohebella, Den- gent, bristle-like expansion, the cnidocil, set in a titheca, Macrorhynchia, Monotheca, Nemale- tubular chimney; the structure of the cnidocil recalls cium, Sertularia) have pelagic stages with medu- that of a modified flagellum. The structure, function, san architecture, often without radial canals and and formation of the cnidocil complex remain to be circular canal, without tentacles and sense organs. determined. The sexual elements are always on the “manubri- Cnidocysts have different functions (Purcell and um” in these Leptomedusae, the “manubrium” Mills, 1988): being in eccentric position. They can not been - adhesion to and entanglement of prey: confused with eumedusoids, the first step of acrophores, anacrophores, and desmonemes. medusa reduction, still with most of the original - penetration into prey: stenoteles, microbasic non reproductive structures of the medusa: radial euryteles, microbasic mastigophores and isorhizae. canals, circular canal, velum, sense organs, with - adhesion of adults, larvae, and eggs to their sub- maturation of the sexual cells according the class- strate: demonemes, isorhizae, euryteles, and es (gonads on manubrium in Anthomedusae and mastigophores. on radial canals in Leptomedusae) and with a non - defense: stenoteles, euryteles, mastigophores, eccentric position of the manubrium. The swim- and isorhizae. ming gonophores are found mostly in Leptome- Cnidocysts develop in specialised regions, and dusae families with paedomorphic hydroids char- not where they are utilised: the stolons in colonial acterized by the possession of fixed and highly forms, the median hydranth regions of certain colo- reduced gonophores (Aglaopheniidae, Sertulari- nial species without or with few stolons (Craspeda- idae, and Haleciidae). custa, Limnocnida, Clava, etc.) or of solitary ones (e.g. Hydra). In medusae, they differentiate either at the level of the nettle ring (Trachymedusae and THE STINGING CELLS (Figs. 23-24, Table 1, 2) some Limnomedusae) or, if this formation is miss- ing, in the tentacular bulbs. Wrapped in the cnido- This section applies to all hydrozoan morphs. cytes, they migrate from the cnidogenous regions Stinging cells or cnidocytes are diagnostic of the toward the tentacles or other armed regions, through Cnidaria; they are usually in the ectoderm, at dif- the ectoderm, the endoderm, the mesoglea or even ferent stages of development, from very young the gastric cavity. cnidoblasts to cnidocytes containing functional Some nudibranchs, turbellarian flatworms, cnidocysts. Most of the cytoplasm of a mature ctenophores, and priapulids may accommodate cnidocyte is occupied by the capsule or cnidocyst numerous ingested cnidocysts (cleptocnidae) in with its apical differentiation, the operculum. The their own tissues or in specialized structures wall of the capsule is continuous with the inward- (cnidosacs) and apparently use them for defence. invaginated cnidocyst tube. The cnidocyst tube The cnidome is the cnidocyst complement of can be either of uniform diameter or differentiated each species. Cnidomes usually comprise from 1 to into a more or less dilated butt and a filament, each 4 cnidocyst types, all specimens of the same species of these elements being either unarmed or armed have the same cnidome. It is often the case, howev- with spines of variable size and shape. The capsule er, that polyps and medusae of the same species of the cnidocyst contains also a paralyzing and have different cnidomes (see Table 2). often-poisonous fluid, the capsular content, which Table 1, modified after Mariscal, 1974, is ejected through the filament tip when the cnido- describes the discharged stages of the most impor- cyst discharges. Cnidocysts discharge occurs by tant cnidocysts, (see also Bouillon et al., 1986; eversion. 1988; Östman, 2000). The undischarged capsules A complex network of fibrils, forming a kind of may in some cases give also useful information basketwork, generally surrounds the capsule. The and serve as a taxonomic character (see below, cnidocyst displaces the nucleus of the cnidocyte heteronemes, Bouillon et al.,1988) (Figs. 23-24).

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TABLE 1. – Morphology of the discharged stages of the most important types of cnidocysts.

ASTOMOCNIDAE: thread closed at the tip

RHOPALONEMES: thread club-shaped and much greater in volume than the capsule Anacrophores: thread without an apical projection* Acrophores: thread with an apical projection*

SPIRONEMES: thread not club-shaped, generally forming a spiral coil distally Haplonemes: thread without a well-defined shaft Desmonemes: thread forming a corkscrew-like coil* Heteronemes: thread with a well-defined shaft Rhopaloides: shaft of unequal diameter Euryteleloids: shaft dilated distally Microbasic: shaft short, less than three times capsule length Spiroteles: thread forms a spiral coil distally, 3 strong spines* Aspiroteles: no thread beyond the shaft, 3 strong spines*

STOMOCNIDAE: most thread open at the tip

HAPLONEMES: thread without a well-defined shaft Isorhizas: thread with uniform diameter Atrichous: thread without well-developed spines Basitrichous: thread with well-developed spines only at base Merotrichous: thread with well-developed spines on the intermediate portion only* Apotrichous: thread with well-developed spines on the distal portion only * Holotrichous: thread with well-developed spines along whole length Anisorhizas: thread slightly dilated toward base* Atrichous: thread without well-developed spines* Homotrichous: thread spiny throughout, spines all of equal size* Heterotrichous: thread spiny throughout, spines larger at base of thread*

HETERONEMES: thread with a well-defined shaft, visible in undischarged capsule Rhabdoides: shaft cylindrical, of the same diameter throughout Mastigophores: thread continues beyond the shaft Microbasic: shaft short, in undischarged cnidocysts almost of same length than capsule, usually straight Microbasic b-mastigophore: shaft tapers gradually into thread Microbasic p-mastigophore: shaft tapers abruptly into thread, V-shaped notch prominent at base of unfired shaft Macrobasic: shaft long, more than two and a half time capsule length, in undischarged cnidocysts shaft much longer than capsule length, horseshoe-shaped or wind up in several loops * Amastigophores: no thread beyond the shaft ** Microbasic: shaft short, less than two and a half times capsule length** Macrobasic: shaft long, more two and an half times capsule length, undischarged shaft much longer than capsule length** Rhopaloides: shaft of unequal diameter Mesoteles: shaft spindle-shaped, devoid of spines, no thread beyond the shaft Euryteles: shaft dilated distally, thread continues beyond the shaft Microbasic: shaft short, less than two and an half times capsule length, in undischarged cnidocysts almost of same length than capsule, usually straight Homotrichous: spines of shaft all of same size* Heterotrichous: spines of shaft of unequal size Semiophoric: thread bent whiplike, with large flat spine medially* Macrobasic: shaft long, more than two and a half times capsule length, in undischarged cnidocysts shaft much longer than capsule length, horseshoe-shaped or wind up in several loops* Telotrichous: spines on distal portion of shaft only* Merotrichous: spines not distal, found only on shaft area of uniform diameter proximal to terminal swelling* Holotrichous: shaft spiny along whole length* Stenoteles: shaft dilated at base, proximal part longer than distal one, 3 strong spines between the two parts, distal portion armed by rows of lamella or spines, thread continues beyond the shaft Pseudostenoteles: shaft dilated at base, proximal part shorter than distal one, 2 to 4 strong spines at constriction between the two parts, smaller spines on distal part, sometimes also with a few large ones, thread continues beyond the shaft Birhopaloides: discharged shaft with a distal and proximal dilatation either separated from each other or close together*

*Present only in Hydrozoa; **not present in Hydrozoa.

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TABLE 2. – Cnidome of Hydrozoa families. Anis.het.: heterotrichous anisorhizas; Anis. Hom.: homotrichous anisorhizas; Apo.isor.: apotri- chous isorhizas; Atr.isor.: atrichous isorhizas; Bas.isor.: basitrichous isorhizas; Bir.: birhopaloides; Des.: desmonemes; Eur.micr.: microba- sic euryteles; Eur.macr.: macrobasic euryteles; Eur.sem.: semiophoric euryteles; Het.: heteronemes; Hol.isor.: holotrichous isorhizas; Mast.micr.: microbasic mastigophores; Mast.macr.: Macrobasic mastigophores; Mero isor.: merotrichous isorhizae; Meso.: mesoteles; Pst.: pseudostenoteles; Sten.: stenoteles ; H: hydroid stage; M: medusa stage; PS: polygastric stage; Com.: comments; ? : either the one or the other; ! : Perhaps.

Types of cnidocysts: Des. Apo. Atr. Bas. Hol. Mero. Anis. Anis Mes. Mast. Mast. Eur. Eur. Eur. Sten Pst. Birh. Com- isor. isor. isor. isor. isor. heter. hom. micr. macr micr. macr. sem.

Cl. HYDROIDOMEDUSAE S.cl. ANTHOMEDUSAE Order FILIFERA Australomedusidae M M Balellidae (u) Bougainvilliidae M H H! M H Bythotiaridae M H M H M M H M Clavidae M H M H Cytaeididae M H M M H Eucodoniidae M M Eudendriidae H H H H H Hydractiniidae M H H! H M H Niobiidae M M Pandeidae M H M M! M M M H Proboscidactylidae MH M M MH MH Protiaridae M M M Ptilocodiidae H H Rathkeidae M H M H Rhysiidae H H Russelliidae (u) Stylasteridae H H Trichydridae Order CAPITATA Acaulidae H H! H H Asyncorinidae M H M H M H Boreohydridae H H? H? H Boeromedusidae M M M Candelabridae H H H! H H Cladocorynidae HH Cladonematidae M H H M H Corynidae M H M H H M H Corymorphidae M H M H M H M H M?H M?H M H Dicyclocorynidae H Eleutheriidae M M H Euphysidae M H H M H! H M H M H Halimedusidae M H? H? M M H Hydridae H H H? H? H Hydrocorynidae M M M H M H Margelopsidae M H H M H M H Milleporidae H H H H Moerisiidae M H H M H H! M MH Paracorynidae H H H H Pennariidae H H H? H? H Polyorchidae M M M? M? M Het.+ Porpitidae M H M MH Protohydridae H H Pseudosolanderiidae H? H? H Rosalindidae H H! H is! Sphaerocorynidae M H M M H Solanderiidae His! Teissieridae H? M H M H? MH Tricyclusidae H H H Tubulariidae M H M H M H MH M?H! M?H MH Zancleidae H M H M H Zancleopsidae M M S.cl. LAIGIOMEDUSAE Laingiidae M MM is! S.cl. LEPTOMEDUSAE Order CONICA Aequoridae M M M M! Aglaopheniidae H H Barcinidae (u) Blackfordiidae M! Campanulinidae H H Cirrholoveniidae (u) Clathrozoidae H

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TABLE 2 (Cont). – Cnidome of Hydrozoa families. Anis.het.: heterotrichous anisorhizas; Anis. Hom.: homotrichous anisorhizas; Apo.isor.: apotrichous isorhizas; Atr.isor.: atrichous isorhizas; Bas.isor.: basitrichous isorhizas; Bir.: birhopaloides; Des.: desmonemes; Eur.micr.: microbasic euryteles; Eur.macr.: macrobasic euryteles; Eur.sem.: semiophoric euryteles; Het.: heteronemes; Hol.isor.: holotrichous isorhizas; Mast.micr.: microbasic mastigophores; Mast.macr.: Macrobasic mastigophores; Mero isor.: merotrichous isorhizae; Meso.: mesoteles; Pst.: pseudostenoteles; Sten.: stenoteles ; H: hydroid stage; M: medusa stage; PS: polygastric stage; Com.: comments; ? : either the one or the other; ! : Perhaps.

Types of cnidocysts: Des. Apo. Atr. Bas. Hol. Mero. Anis. Anis Mes. Mast. Mast. Eur. Eur. Eur. Sten Pst. Birh. Com- isor. isor. isor. isor. isor. heter. hom. micr. macr micr. macr. sem.

Dipleurosomatidae M Eirenidae M H M H M M Haleciidae H H! HH H Halopterididae H H Hebellidae M M H Kirchenpaueridae HH H H! H Lafoeidae H H H Lineolariidae (u) Laodiceidae M M M Lovenellidae M M H M HH Malagazziidae M H M H M H Melicertidae MM M Mitrocomidae M M H H Octocannoidae M M Orchistomatidae M Phialellidae M? M? Plumulariidae H H H Sertulariidae HH H Sugiuridae (u) Syntheciidae (u) Teclaiidae (u) Thyroscyphidae HH Tiarannidae M Tiaropsidae M M Order PROBOSCOIDA Bonneviellidae (u) Campanulariidae M H M H MH Phialuciidae M S.cl. LIMNOMEDUSAE Armorhydridae M M Microhydrulidae HH Olindiidae MM M M H M M anis? S.cl. SIPHONOPHORAE Acro. = rhopalonemes acrophores; Ana.= rhopalonemes anacrophores. Order CYSTONECTAE Physaliidae PS PS Rhizophysidae (u) Order PHYSONECTAE Agalmatidae PS Acro. PS PS PS Apolemiidae PS Acro. PS PS PS PS PS Athorybiidae (u) Forskaliidae PS Acro. PS PS PS Physophoridae (u) Pyrostephidae (u) Rhodaliidae (u) Order CALYCOPHORIDAE Abylidae PS Ana. PS PS Clausophyidae (u) Diphyidae PS Ana. PS PS Hippopodiidae PS Ana. PS PS Prayidae PS Ana. PS PS Cl. AUTOMEDUSA S.cl. ACTINULIDAE Halammohydridae aspirotelesM M M M Otohydridae spiroteles M S.cl. NARCOMEDUSAE Aeginidae MM Cuninidae MM S.cl. TRACHYMEDUSAE Geryoniidae M M Halicreatidae M? M? M Petasidae M Ptychogastriidae M M M Rhopalonematidae M! M M Cl. POLYPODIOZOA Polypodiidae M

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DIAGNOSTIC CHARACTERS present in the material under description. The char- acter state “absent” is not mentioned, since it is use- Species descriptions must provide information less to state that a given character is not present. about the state of diagnostic characters (Table 3). This, however, is to be mentioned when an impor- Insufficient description is the main cause of nomen- tant character (e.g. the presence of ocelli), present in clatural confusion and it is often the case that new phylogenetically near species, can be either present species are based on slight variations of probably or absent. Stating the absence of ocelli, in this case, irrelevant characters. The following is a list of the means that they have been searched for (since they diagnostic characters of both hydroids and medusae are usually present in a given genus), but that they and of their possible states. A description should were not present in the described specimen. Charac- report on the state of all the diagnostic characters ter states are often split into further sub-states.

TABLE 3. – Diagnostic characters and characters states to describe the three main morphological types of Hydrozoa.

Medusae Oral tentacles: Simple Umbrella: Branched Shape: Position of oral tentacles: Flat Arising from mouth rim Hemispherical Arising above mouth rim Lens-shaped Saucer-shaped Mesenteries: Dome-shaped Length versus subumbrellar cavity Conical Globular Radial canals: Maximum diameter Number Maximum high Simple Colour With diverticula Mesoglea: Bifurcated Thin Branched Thick Jagged Stiff Swollen at some zones Soft With gonads (see gonads) Marginal portion thinner than apical portion Incomplete: Marginal portion as thick as apical portion Centripetal With apical process = apical projection Centrifugal With apical or umbilical canal Exumbrellar cnidocyst pouches or clusters: Ring canal: Size Tubular Shape Filled by endodermal core Number and types of cnidocysts “Gonads”: Manubrium: Number Shape: Colour Cylindrical Position: Quadratic On radial canals Cruciform Near manubrium Colour Near umbrellar margin Lenght versus subumbrellar cavity In the middle of radial canal Presence or not of gastric peduncle Along the whole radial canal Lenght of peduncle versus subumbrellar cavity On manubrium: Manubrial pouches: Proximal Position Distal Shape Median Size versus subumbrellar cavity Completely surrounding manubrium In one mass Mouth: In several masses Shape: In longitudinal bands: Circular Interradial Quadrangular Perradial Cruciform Adradial Lips: Shape: Number of lips Oval Simple Linear Crenulated Sinuous Folded Folded Oral cnidocyst clusters Pendulous Mouth arms: Pouch-like Unarmed Split by a median groove Armed whith cnidocyst clusters Egg size and number

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TABLE 3 (Cont.). – Diagnostic characters and characters states to describe the three main morphological types of Hydrozoa.

Cordyli: Velum: Position Straight With nematocysts Pendulous Wide Ocelli: Narrow Position: Abaxial Marginal cnidocyst ring: Adaxial Wide Location: Narrow On bulbs On margin Marginal tentacles: On exumbrellar pouches Number Colour Length Ectodermal Simple Ecto-endodermal (associated with statocyst) Branched With lens Capitate Shape: Filiform Round Moniliform Oblong Position: Elongate On margin, Above margin Cnidome: With cnidophores State all nematocyst types and their position on Hollow the medusan body Solid Secondary tentacles different in structure and length from primary Medusa buds: ones Position: With endodermal roots inserted in the mesoglea On marginal bulbs With marginal bulbs On manubrium On margin Marginal bulbs: On radial canals Without tentacles: On exumbrella Developing tentacular marginal bulbs On gonads Permanent rudimentary bulbs In gonothecae borne on radial canals With tentacles: Number Specific characters exclusive for the Narcomedusae: Colour Position of manubrial pouches: Shape Interradial Position on exumbrellar margin: Perradial Perradial Number of primary tentacles (above peronia) Interradial Secondary marginal tentacles (on marginal lappets = Adradial exumbrellar lobes) With exumbrellar abaxial spurs Peripheral and peronial canals (peripheral canal system) Simple Number of marginal lappets Compound: Number of peronia Number of tentacles per bulb Number of otoporpae Marginal swellings or warts: Number Specific characters exclusive for the Actinulidae: Position Body shape: Cirri: Oval Position: Worm-like Lateral (to tentacles) Oral cone Marginal (between tentacles) Adhesive aboral organ Type: Nerve ring Flexile Tentacular bulbs Spiral Statocysts: Tentaculae Aboral Marginal “Excretory pores”: Number Position: Brood pouches On bulbs Gonads: On exumbrellar margin Gonochoric On papillae Hermaphrodite Statocysts: Diagnostic characters and character states to describe polyps Number Type: Solitary: Ectodermic Type of fixation: Ecto-endodermic By anchoring filaments Open By mucus secretion Closed Position Colonial: Number of statolyths Pelagic Floating

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TABLE 3 (Cont.). – Diagnostic characters and characters states to describe the three main morphological types of Hydrozoa.

Fixed: Number Stolonal Length Erect Scattered With coenosteum (calcareous) In whorls: Number of whorls Hydrorhiza: Number of tentacles per whorl Simple Tentacle type: Reticular Hollow Rhizcaulomic Solid Encrusting Capitate Covered by perisarc Capitate ramified Covered by coenosarc Cateniform With spines (acanthozooids): Filiform Smooth Moniliform Serrate Pseudofiliform Semifiliform Hydrocaulus: Semimoniliform Monosiphonic Transformed into nematodactyls Polysiphonic Transformed into sense organs (acnide) Simple Cnidocyst pouches on column Divided in internodes Gonophores (either fixed or medusa buds): Internodes with apophysis Above aboral tentacles Annulated Among aboral tentacles Unbranched Below aboral tentacles Branched: Single Arborescent In clusters Bushy Cymose Pseudohydrotheca: Flabellate Covering hydranth base Flexuose Covering hydranth and tentacle bases Pinnate (alternate or opposite) Plumose Hydrotheca: Racemose On hydrorhiza: Spiral Reptant (i.e. creeping) Straight (biseriate or uniseriate) Sessile Whorled Pedicellate Verticillate On stem, and/or branches,: Pedicellate Hydrocladia: Adnate Annulated Sunk Unbranched Sessile Branched: Alternate On apophysis (or hydrophore) Opposite Alternate Pinnate Opposite Plumose In longitudinal rows (state number Spiralled Irregularly arranged Verticillate Form: Hydranth (gastrozooid in polymorphic species): Tubular Size range (can change much due to contraction and feeding) Campanulate Naked Cup-like Protected: Dish-like Hydrotheca (see character states below) Armed with nematothecae (see nematothecae character states) Pseudohydrotheca (see character states below) Operculate (see operculum character states) With abcauline caecum Asymmetrical With mantle = ectodermal lamella: With horizontal stripes Mantle with cnidocyst armature or ligula With longitudinal stripes With annular ectodermal fold Perisarc of irregular thickness Hypostome: Conical Operculum: Simple Pleated (folded) With a glandular preoral chamber or button Segmented (discrete opercular flaps): Peduncled with a buccal cavity (sometimes termed: With creaseline at base trumpet-shaped) Number of flaps: Oral tentacles: One: Number Abcauline Length Adcauline Amphicoronate Two Unicoronate Three Asymmetrically arranged (one, two, etc.) Four With intertentacular web (umbrellula) Many Aboral tentacles: Pyramidal

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TABLE 3 (Cont.). – Diagnostic characters and characters states to describe the three main morphological types of Hydrozoa.

In form of a gable roof Position: Everted rim On hydranth Hydrothecal cusps (often called teeth): On hydrocaulus and/hydrocladia Number On hydrorhiza Straight Sessile Obliquous Pedicellate Flat Giving rise to: Folding inwards (this leads to the formation of longitudinal Free medusae lines on the theca) Eumedusoids Shape: Fixed sporosac Triangular Swimming sporosacs Castellate Swimming gonophores: Bicuspidate With gastrovascular system Rounded Without gastrovascular system With central “manubrium” (spadix) Internal teeth below margin: With eccentric “manubrium” (spadix) Number With refringent corpuscles on umbrellar margin Intrathecal septum Without gonothecae Perisarcal diaphragm With gonothecae: Annular perisarcal thickening Simple, unprotected Democytes As corbula Spherule As coppinia Dactylozooids: As phylactocarps Spiral (spiral zooids) As scapus Roughly straigth With nematothecae Position: Without nematothecae On hydrorhiza On stem (mainly nematophores) Diagnostic characters and character states to describe On hydranth (the so-called cnidophore of Eudendrium) siphonophores Solid (Tentaculozooids) Hollow Nectosome: With tentacles Nectophores: Cnidocyst arrangement: Number Capitate Position: (anterior and posterior in calycophorans) Filiform Apical wings Semimoniliform Ascending branches Basal facet Nematophores: Basal lamella Sessile Commisural canals Pedicellate Commissures Naked Descending branches Protected by a nematothecae: Hydroecium Immovable or fixed or one-chambered (monothalamic) Lateral wings Movable or two-chambered (bithalamic) Lateral canals Position of nematothecae: Mouth-plate Hydrothecal Ostial teeth Lateral Pallial canal Mesial = inferior median Pedicular canal Superior Ridges Caulin Somatocyst Gonothecal Thrust-block With sarcostyle and cnidostyle Siphonosome: Gonozooid: Gastrozooid: Size Basigaster Position of gonophores: Tentacle Scattered Tentilla In whorls Terminal filament In clusters Palpons: Isolated Palpacles Tentacles: Gonodendron: Number Gonopalpon Arrangement Gonophores Type (see above for character states) Eumedusoid Mouth present Sporosac Eudoxid (bract + gonophore) Gonophores: Bracts: Simple Bracteal canals In clusters Neck-shield On blastostyles Phyllocyst Aggregated Gonophore

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SIMPLIFIED KEYS FOR HYDROZOA ...... Anthomedusae SUBCLASSES IDENTIFICATION 3. “Gonads” exclusively on manubrium; tentacles solid, above exumbrellar margin; with or without Hydroids tentacular bulbs; umbrella lobed, divided by peronial grooves or similar structures; with radi 1. Polyp generation planktonic, in the form of al canals, circular canal as a solid core of polymorphic colonies with a float and central endodermal cells; umbrella roughly hemispheri- gastrozooid ...... Anthomedusae Porpitidae cal; hydroid stage unknown ...... Laingiidae. – Polyp generation usually sedentary; exceptionally – “Gonads” on radial canals, exceptionally planktonnic but different from above ...... 2 contiguous with base of manubrium; marginal 2. Hydranth generally with a definite hydrotheca and tentacles usually hollow; with tentacular bulbs; gonothecae of definite shape ...... Leptomedusae umbrella entire; with radial and circular canals; – Hydranth with no definite hydrothecae, or sense organs, when present, statocysts formed gonothecae...... 3 exclusively by the velar ectoderm, open or 3. Hydranth solitary or colonial, usually rather closed, sometimes cordyli, rarely ocelli; conspicuous; sometimes with a coenosteum; umbrella usually flattened; with hydroid stage... mostly with desmonemes ...... Anthomedusae ...... Leptomedusae. – Hydranth small, sessile; generally solitary or 4. “Gonads” on radial canals; marginal tentacles forming small reptant or bipolar colonies; never solid (a mixture of solid and hollow tentacles in with desmonemes ...... Limnomedusae Geronyidae); without tentacular bulbs; exumbrella entire; with an exumbrellar marginal Pelagic Hydrozoa cnidocyst ring; with radial and circular canals; statocysts as free marginal clubs, 1. Usually with sense organs, ocelli or statocysts, usually free, rarely enclosed by exumbrellar individuals as free swimming medusae, never ectoderm; umbrella tall to hemispherical colonial ...... Hydromedusae. ; without hydroid stage...... Trachymedusae. – Without any kind of visible sense organs, forming – “Gonads” on manubrium (often on pelagic and floating modular highly polymorphic manubrial pouches); primary tentacles colonies formed by the association of medusoid solid, above exumbrellar margin, sometimes and polypoid zooids, medusoids never develop . secondary, marginal tentacles; without ing into complete medusae...... Siphonophorae tentacular bulbs; umbrella lobed, divided by peronial grooves; usually without Hydromedusae radial canals; circular canal, when present, jagged, in form of peripheral system; The term hydromedusae is used here in the sense statocysts usually as free marginal of “the medusae of the Hydrozoa” and comprises both clubs; umbrella typically flatter than an Hydroidomedusa and Automedusa, without having a hemisphere, with a central lens-shaped mass formal taxonomic rank. The key is just an identifica- of mesoglea; without true hydroid stage...... tion tool, and is not intended to reflect phylogeny...... Narcomedusae. – “gonads” on radial canals, exceptionally on 1. Without statocysts and gonads on manubrium .2 manubrium; marginal tentacles hollow; without – With gonads on radial canals and, usually tentacular bulbs; umbrella entire; with radial and ectodermal statocysts...... 3 circular canals; with statocysts enclosed into the – Statocysts ecto-endodermal, with endodermal mesoglea near ring canal or in the velum; with axis ...... 4 hydroid stage...... Limnomedusae. 2. “Gonads” on manubrium, occasionally – “Gonads” on manubrium, between ectoderm and extending for a short distance along basal region endoderm; tentacles solid, with or without ten- of radial canals; marginal tentacles solid or hol tacular bulbs; umbrella entire or very reduced; low; usually with tentacular bulbs; umbrella without radial and circular canals; statocysts generally entire; with radial and circular canals; aboral or marginal; manubrium elongated, sense organs, where present, ocelli; umbrella typ- terminating in a simple mouth-opening; without ically bell-shaped; with hydroid stage ...... hydroid stage...... Actinulidae.

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OUTLINE CLASSIFICATION Family Aequoreidae Eschscholtz, 1829 Family Aglaopheniidae Class Hydroidomedusae Claus, 1877 Marktanner-Turneretscher, 1890 Subclass Anthomedusae Haeckel, 1879 Family Barcinidae Gili, Bouillon, Pagès, Order Filifera Kühn, 1913 Palanques and Puig, 1999 Family Bougainvillidae Lütken, 1850 Family Blackfordiidae Bouillon, 1984 Family Bythotiaridae Maas, 1905. Family Campanulinidae Hincks, 1868 (= Calycopsidae) Family Cirrholoveniidae Bouillon, 1984 Family Clavidae McCrady, 1859 Family Eirenidae Haeckel, 1879 Family Cytaeididae L. Agassiz, 1862 Family Haleciidae Hincks, 1868 Family Eucodoniidae Schuchert, 1996 Family Halopterididae Millard, 1962 Family Eudendriidae Agassiz, 1862 Family Hebellidae Fraser, 1912 Family Hydractiniidae L. Agassiz, 1862 Family Kirchenpaueriidae Stechow, 1921 Family Niobiidae Petersen, 1979 Family Lafoeidae A. Agassiz, 1865 Family Pandeidae Haeckel, 1879 Family Laodiceidae Agassiz, 1862 Family Proboscidactylidae Family Lovenellidae Russell, 1953 Hand and Hendrickson, 1950 Family Malagazziidae Bouillon, 1984 Family Protiaridae, Haeckel 1879 Family Melicertidae Agassiz, 1862 Family Ptilocodiidae Coward, 1909 Family Mitrocomidae Haeckel, 1879 (part); Family Rathkeidae Russell, 1953 Torrey, 1909 Family Rhysiidae Brinckmann, 1965 Family Orchistomatidae Bouillon, 1984 Family Russelliidae Kramp, 1957 Family Phialellidae Russell, 1953 Family Stylasteridae Gray,1847 Family Plumulariidae Agassiz, 1862 Family Trichydridae Hincks, 1868 (Hincks, 1868) Order Capitata Khün, 1913 Family Sertulariidae Lamouroux, 1812 Suborder Moerisiida Poche, 1914 Family Syntheciidae Marktanner- Family Hydridae Linneaus,1758 Turneretscher, 1890 Family Moerisiidae Poche, 1914 Family Teclaiidae Bouillon, Pagès, Gili, Family Protohydridae Allman, 1888 Palanques, Puig and Heusner, 1999 Suborder Sphaerocorynida Petersen, 1990 Family Thyroscyphidae Stechow, 1920 Family Sphaerocorynidae Prévot, 1959 Family Tiarannidae Russell, 1940 Suborder Tubulariida, Fleming, 1828 Family Tiaropsidae Boero, Bouillon and Family Acaulidae Fraser,1924 Danovaro, 1987 Family Boreohydridae Westblad, 1937 Order Proboscoida Broch, 1910 Family Candelabridae de Blainville, 1830 Family Campanulariidae Jonhston, 1836 Family Cladonematidae Gegenbaur, 1857 Family Phialucidae Bouillon, 1984 Family Corymorphidae Allman, 1872 Subclass Limnomedusae Kramp, 1938 Family Corynidae Johnston, 1836 Family Armorhydridae Swedmark and Family Euphysidae Haeckel, 1879 Teissier, 1958 Family Paracorynidae Picard,1957 Family Microhydrulidae Bouillon and Family Pennariidae McCrady, 1859 Deroux, 1967 Family Tricyclusidae Kramp, 1949 Family Olindiidae Haeckel, 1879 Family Tubulariidae Fleming, 1828 Subclass Siphonophorae Eschscholtz, 1829 Suborder Zancleida Russell, 1953 Order Cystonectae Haeckel, 1887 Family Cladocorynidae Allman, 1872 Family Physaliidae Linnaeus, 1758 Family Porpitidae Goldfuss, 1818 Family Rhizophysidae Brandt, 1835 Family Rosalindidae Bouillon, 1985 Order Physonectae Haeckel, 1888 Family Zancleidae Russell, 1953 Family Agalmatidae Brandt,1835 Subclass Laingiomedusae Bouillon, 1978 Family Apolemiidae Huxley, 1859 Family Laingiidae Bouillon, 1978 Family Athorybiidae Huxley, 1859 Subclass Leptomedusae Haeckel, 1866 (1879) Family Forskaliidae Haeckel,1888 Order Conica Broch, 1910 Family Physophoridae Eschscholtz, 1829

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Order Calycophoridae Leuckart,1854 Order FILIFERA Kühn, 1913 Family Abylidae Agassiz,1862 Family Clausophyidae, Totton 1965 Hydroid: hydranths with filiform tentacles Family Diphyidae Quoy and Gaimard, 1827 (except in the dactylozooids of the Ptilocodiidae). Family Hippopodiidae Kölliker, 1853 Medusa: with “gonads” forming separated inter- Family Prayidae Kölliker, 1853 radial, adradial or perradial longitudinal masses on Family Sphaeronectidae Huxley,1859 the walls of the manubrium (exceptionally encir- Subclass Actinulidae Swedmark and Teissier, 1959 cling entire manubrium). Mouth either with four Family Halammohydridae Remane 1927 simple or complex lips, or circular, surmounted by Family Otohydridae Swedmark and Teissier, oral manubrial tentacles. Marginal tentacles solid or 1958 hollow. Cnidome including usually desmonemes Subclass Narcomedusae Haeckel, 1879 and microbasic euryteles, never stenoteles. Planulae Family Aeginidae Gegenbaur, 1857, emend. having only one type of ectodermal glandular cells: Maas, 1904 spumous cells. Family Cuninidae Bigelow, 1913 Family Solmarisidae Haeckel, 1879 Key to hydroid stages of the filiferan families Subclass Trachymedusae Haeckel, 1866 (1879) Family Geryoniidae Eschscholtz, 1829 1. Hydranth with trumpet shaped hypostome ...... Family Halicreatidae Fewkes, 1886 ...... Eudendriidae Family Petasidae Haeckel, 1879 – Hydranth with conical or rounded hypostome .2 Family Ptychogastriidae Mayer, 1910 2. Colonies with hydrorhiza forming a massive Family Rhopalonematidae Russell, 1953 calcareous coenosteum ...... Stylasteridae Class Polypodiozoae Raikova, 1988 – Colonies without massive calcareous Family Polypodiidae Poche, 1914 coenosteum ...... 3 3. Dactylozooids usually present ...... 4 – Dactylozooids absent ...... 7 SYSTEMATICS 4. Hydranth with tentacles ...... 5 – Hydranth without tentacles ...... Ptilocodiidae Class HYDROIDOMEDUSA Claus, 1877 5. Hydranth with two tentacles Proboscidactylidae Subclass ANTHOMEDUSAE Haeckel, 1879 – Hydranth with more than two tentacles ...... 6 6. Gonophores as non styloid fixed sporosacs, as Hydroid: typically athecate, without a rigid perisar- eumedusoids or free medusae, produced on cal theca covering the hydranth body, a gelatinous or gonozooids only; dactylozoids when present membranous pseudohydrotheca may sometimes cover naked ...... Hydractiniidae the hydranth base, adhering closely to the ectoderm. – Gonophores styloid, gonads inside hydranth Medusa: typically bell-shaped, with “gonads” walls; dactylozooids covered entirely or partially confined on manubrium, sometimes extending on by perisarc ...... Rhysiidae the most proximal parts of the radial canals; margin- 7. Tentacles in distal (oral) whorls only...... 9 al sense organs, if present, ocelli, never statocysts or – Tentacles in several whorls over the body or cordyli; marginal tentacles peripheral, hollow or scattered over the entire body ...... 8 solid, with tentacular bulbs (except for most of the 8. Hydranth with tentacles scattered all over the Bythotiaridae, Eugotoea petalina, and Rhabdoon body (exceptionally with nematothecae = singulare); sexual reproduction through a complex Merona), colonies erect or stolonal; gonophores planula stage with interstitial cells, neural cells, never developed on hydranth body...... Clavidae cnidoblasts and one or two types of glandular cells. – Hydranth with up to five irregular whorls of Cnidome normally including desmonemes. filiform tentacles; sessile; hydrorhiza forming a The Anthomedusae are divided into two orders: plate giving rise to unbranched colonies living in the Filifera (with cnidome including desmonemes and the prebranchial cavity of ascidians ...... euryteles) and the Capitata (with cnidome including ...... Bythotiaridae stenoteles). The name Filifera refers to the filiform 9. Colonies generally erected; polyps usually with a tentacles of the hydroid stage, whereas the name Cap- pseudohydrotheca covering partially or totally itata refers to the mostly capitate tentacles of hydroids. the body and tentacles; hypostome surrounded

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by one or more whorls of distal tentacles ...... cluster...... Bythotiaridae ...... Bougainvilliidae – Marginal tentacles usually with basal bulbs, – Colonies stolonal...... 10 without terminal cnidocyst clusters or capitations 10.Hydranth usually with base surrounded by a ...... 3 collar-like tube of perisarc or with a thin basal 3. With branched or divided radial canals...... 4 mucous-like perisarc structure...... 11 – With undivided radial canals...... 5 – Hydranth with completely free base or with the 4. With two simple and two bifurcated radial body entirely covered with a mucous canals; tentacular bulbs develop into medusae ... pseudohydrotheca ...... Pandeidae ...... Niobiidae 11.Hydrocaulus with a conspicuous cylindrical – With 4-6 branched radial canals, exumbrella with perisarc tube ...... 12 exumbrellar cnidocyst tracts; manubrium with – Hydranth with a reduced basal perisarcal cup .... radial gastric pouches; usually with no circular ...... 13 canal; without rudimentary bulbs...... 12.Hydranth almost completely retractable in his ...... Proboscidactylidae perisarcal tube, when contracted only the tips of 5. With 4 unbranched oral tentacles, without the tentacles show beyond the edge of the tube; terminal clusters of cnidocyst, situated above hydranth very slender and extensible; with one mouth opening ...... Russellidae amphicoronate whorl of 6 filiform tentacles...... – Without oral tentacles...... 6 ...... Trichydridae 6. With 4 radial canals; with only 4 marginal – Hydranth only partially retractable in his tentacles in adults and without rudimentary perisarc tube, very slender, elongated, bulbs; cnidome with merotrichous isorhizas...... cylindrical, with one whorl of about 10 long ...... Protiaridae filiform tentacles with irregular clusters of large – With two or more tentacles in adults; with 4 cnidocysts alternating with the tentacles; unbranched radial canals (rarely 8, Octotiara); cnidome containing, among other cnidocysts manubrium usually without radial gastric merotrichous isorhizas ...... Protiaridae pouches (except Annatiara) with or without 13.Hydranth with one more or less regular whorl of rudimentary bulbs; cnidome without oral tentacles or with two closely alternating oral merotrichous isorhizas ...... Pandeidae whorls; surrounding a conical hypostome; 7. With oral tentacles...... 8 perisarcal collar where present chitinous, small, – Without oral tentacles...... 9 cup-shaped or vase-like, reproduction by 8. With oral tentacles simple, situated on/or very medusa buds or fixed sporosacs...... Cytaeidae near mouth rim ...... Cytaeididae – Hydranth with a single distal whorl of threadlike - With oral tentacles simple or branched, distinctly tentacles surrounding a rounded hypostome; with inserted above mouth rim ...... Bougainvilliidae hydranth base surrounded by a gelatinous, 9. Mouth with 4 distinct lips ...... 10 mucous perisarcal structure; reproduction by – Mouth with 4 inconspicuous lips, each medusa buds arising from hydrorhiza or more containing a group of about 100 cnidocysts ...... rarely from the base of hydranth...... Rathkeidae ...... Eucodoniidae 10.Lips simple, without cnidocyst clusters ...... 11 Key to the filiferan families, medusa stage – Mouth armed with cnidocyst clusters ...... 12 11.Tentacles in groups, 4-8 simple radial canals ..... 1. Medusae with hollow tentacles; ocelli, when ...... Australomedusidae* present, abaxial; mouth simple, lips usually – Tentacles solitary; 4 radial canals with usually without specialised cnidocyst armed structures, fine, branched, anastomosing centripetal canals. without oral tentacles (except Russsellidae) .... 2 ...... Trichydridae – Medusae with solid tentacles; ocelli, when 12.Mouth rim and lips covered with a continuous present, adaxial; mouth either with simple lips, row of cnidocyst clusters along their margin...... or with oral solid tentacles armed with cnidocyst ...... Clavidae clusters or presenting oral arms armed with – Mouth lips elongated to form perradial mouth cnidocyst clusters ...... 7 arms with one or many distinct cnidocyst clusters 2. Marginal tentacles without basal bulbs or ...... 13 swellings, terminated in a terminal cnidocyst 13.With exumbrellar didermic centripetal canals or

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rows of refringent spots issuing from a marginal unbranched colonial bougainvilliid polyps with cnidocyst ring...... Ptilocodiidae pseudohydrotheca not enveloping the tentacles, – Without didermic exumbrellar centripetal canals with one whorl of tentacles and with fixed or refringents spot rows, without marginal sporosacs. Millard (1975) followed by Bouillon cnidocyst ring ...... 14 (1985) mistakenly included Parawrightia as syn- 14.Marginal tentacles solitary ...... Hydractiniidae onym of Rhizorhagium. Calder (1988) proposed a – Marginal tentacles in 8 groups ...... Rathkeidae division of the Bougainvilliidae into four sub-fami- * not represented in Mediterranean Sea. lies, the Pachycordylinae, Rhizorhagiinae, Bimeri- inae, Bougainvilliinae according to one or more of Family BOUGAINVILLIIDAE Lütken, 1850 the following hydroid characters: presence of pseudohydrotheca, form of the hypostome (nipple- Hydroid: colony stolonal or erect, branched or shaped, dome-shaped), number of tentacle whorls, unbranched, monosiphonic or polysiphonic; perisarc position of gonophores. Since the systematic value firm, terminating either at base of hydranths or of some of these characters is questionable even at forming a pseudohydrotheca; hydranths with one or the generic level, this separation in sub-families is more definite whorls of filiform distal tentacles, not adopted here. The pseudohydrotecae can cover more or less close-set beneath conical hypostome; hydranth body and a variable proportion of the ten- gonophores as free medusae or fixed sporosacs tacles as in the genera Bimeria, Koellikerina and developing mostly on hydrocauli, hydrocladia, Thamnostoma or extend only around hydranth as in occasionally on hydrorhiza and rarely from modi- the other Bougainvillidae genera. Calder’s distinc- fied hydranths. tion between subfamilies based on the shape of the Medusa: usually bell-shaped; manubrium short; hypostome, dome-shaped in a subfamily Pachy- mouth simple, circular, with simple or dichotomous- cordylinae nipple-shaped in the Rhizorhagiinae is ly branched oral tentacles, inserted distinctly above nor very convincing. The hypostome shape being mouth rim and armed with cnidocyst clusters; 4 very variable, depending upon the degree of expan- radial canals and circular canal; marginal tentacles sion, of contraction of the concerned specimen; it is solid, either solitary or in clusters, borne on 4, 8, or also linked to stade of feeding, fixation etc. and, 16 tentacular bulbs; “gonads” on manubrium, either several members of the Rhizorhagiinae does not forming a continuous ring or on adradial, interradial have a nipple-shaped hypostome and have so to be or perradial axes; adaxial ocelli absent or present. redistributed into other doubtful resurrected genera Remarks: the Bougainvilliidae comprise genera like Gravelya and Aselomaris not conform to the with well known free medusae and an assemblage Calder’s definition of the subfamily. It seems of hydroid-based genera with fixed gonophores preferable to refrain the splitting the Bougainvilli- bearing one or more whorls of filiform tentacles dae with fixed sporosacs into to many genera and beneath hypostome. As the reduction of free we follow here with some slight modifications Rees medusae to fixed gonophores may have occurred suggestion (see key below) hoping for the proposal several times independently during the evolution of of a more natural classification. This seems not very the Bougainvilliidae, it is impossible to refer pae- realistic, if not impossible, without the help of mol- domorphic species to any presently known medusa ecular biology. The bougainvilliids with fixed genus. Many of the hydroids of those genera have sporosacs and one single whorl of tentacles could an almost similar morphology and few reliable even been grouped into two genera only Bimeria diagnostic characters; they have been lumped and with pseudohydrotheca covering part or all of the separated several times according to the different tentacles and Garveia with pseudohydrotheca criteria. Furthermore, most bougainvilliid hydroids extending only on hydranth body; the main differ- are not distinguishable from the presently known ences between Rhizorhagium and Garveia are tenu- Pandeidae hydroids and, paradoxically, no hydroid ous: unbranched colonies in Rhizorhagium or species with fixed sporosacs has been described in branched in Garveia. this family (see Pandeidae). It is thus not to exclude References: Wedler and Larson (1986); Calder that some of the Bougainvilliidae genera with fixed (1988); Pagès, Gili and Bouillon (1992); Bouillon sporosacs could in fact belong to Pandeidae, or (1995, 1999); Migotto (1996); Schuchert (1996); even to the Clavidae. Rees (1938) re-erected the Bavestrello et al. (2000); Bouillon and Barnett genus Rhizorhagium Sars, 1874 for all the (1999); Bouillon and Boero (2000).

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Key to hydroids Bimeria vestita Wright, 1859 (Fig. 25A-C) 1. Pseudohydrotheca absent ...... 7 – Pseudohydrotheca present ...... 2 Colonies yellowish composed of hydrocauli erect, 2. Pseudohydrotheca covering tentacle bases ...... 3 up to 30 mm high, monosiphonic and usually scarce- – Pseudohydrotheca not covering tentacle bases ... ly branched, with monopodial growth. Perisarc of the ...... 4 stem with several groups of 4-5 annuli along its 3. Colonies producing fixed sporosacs...... Bimeria length; hydrocladia roughly alternate, not in the same – Colonies producing free medusae .. Koellikerina plane, annulated basally. Hydranth at the extreme of 4. Gonophores developing into free medusae...... branches, partially covered by perisarc, these forming ...... Bougainvillia sheaths over basal parts of tentacles; 10-20 tentacles. – Gonophores not developing into free medusae... Gonophores borne on stem and branches, on annulat- ...... 5 ed pedicels, covered of gelatinous perisarc; male 5. Gonophores borne on blastostyles and producing ovoid, with branching spadix; female ovoid to spher- swimming sporosacs...... Dicoryne ical, containing one ovum, which lack the perisarc – Gonophores borne on pedicels and producing when mature; colonies dioecious. fixed sporosacs ...... 6 Records from Mediterranean: Adriatic, eastern 6. Hydrocauli branched, hypostome dome-shaped and western Mediterranean...... Garveia Known seasonality: 7, 10-5. – Hydrocauli rarely branched, hypostome Distribution: cosmopolitan species. nipple-shaped...... Rhizorhagium References: Picard (1958b); Millard (1975); 7. Hydranth with one whorl of tentacles; fresh Ramil and Vervoort (1992a); Boero and Bouillon water animals...... Velkovrhia (1993); Altuna (1994); Medel (1996); Avian et al. – Hydranth with 2-4 alternating close whorls of (1995); Medel and López-González (1996). tentacles; marine animals ...... Pachycordyle Genus Bougainvillia Lesson, 1830 Key to medusae Hydroid: colony usually erect, branched or 1. Oral tentacles simple unbranched ...... 2 unbranched, more rarely stolonal; perisarc terminat- – Oral tentacles dichotomously branched ...... 3 ing at base of hydranth or extending upwards as a 2. With 4 radial canals...... Nubiella pseudohydrotheca; hydranth fusiform to clavate, – With 8 radial canals ...... Lizzia hypostome dome-shaped, with one distal whorl of 3. With solitary marginal tentacles .. Thamnostoma tentacles, never enveloped by the pseudohydrothe- – With marginal tentacles in 4 or 8 groups...... 4 ca. Gonophores as free medusae, arising singly or in 4. With marginal tentacles in 4 perradial groups .... clusters from hydrocaulus, hydrocladia or ...... Bougainvillia hydrorhiza. – With marginal tentacles in 8 groups, 4 perradial, Medusa: 4 perradial clusters of identical solid 4 interradial ...... Koellikerina marginal tentacles; 4 perradial oral tentacles dichotomously branching in normally developed Genus Bimeria Wright, 1859 medusae; “gonads” on manubrium, adradial, interra- dial or, rarely, perradial; with or without ocelli. Hydroid: colonies stolonal or with erect References: Calder (1988, 1993); Bouillon branching hydrocauli; stem with firm perisarc (1995); Schuchert (1996). enveloping hydranth, extending as a pseudohy- One doubtful medusa species with simple drothecal sheath over proximal portion of tenta- unbranched oral tentacles has been described from cles; hydranths ovoid to vasiform, hypostome Mediterranean: Bougainvillia multicilia (Haeckel, dome-shaped, sometimes with a preoral cavity 1879). (See Diagnosis below). (i.e., Bimeria rigida), with one or two close oral whorls of tentacles; gonophores as fixed Key to hydroids sporosacs, completely invested in perisarc on hydrorhiza and branches. 1. Hydrocauli monosiphonic; perisarc slightly Reference: Calder (1988). wrinkled throughout...... B. britannica.

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– Hydrocauli monosiphonic or polysiphonic often Bougainvillia britannica (Forbes, 1841) infested by detritus; wrinkled at base of (Figs. 25E-H) hydrocladia...... B. muscus Hydroid: colonies with erected stems, not much Key to medusae branched and not densely distributed arising from a large meshed network of tubular stolons; hydrocauli 1. Marginal tentacles with adaxial ocelli ...... 2 and hydrocladia branches monosiphonic, their slight- – Marginal tentacles without ocelli; two to four ly transversally wrinkled perisarc, investing adult tentacles per marginal bulb, basal trunk of oral hydranths till tentacular level, forming cup-like tentacles very long ...... B. aurantiaca pseudohydrothecae, expended hydranths extending 2. Basal trunk of the oral tentacles very short, well beyond pseudhydrothecae; hydranth terminal on almost divided 5 or 6 times immediately from hydrocauli and hydrocladia, club-shaped, with short base; manubrium remarkably flat, quadrangular conical hypostome, with up to 14 amphicoronate fili- ...... B. platygaster form tentacles. Medusa buds borne singly or in clus- – Basal trunk of oral tentacles long...... 3 ters on branched stalks arising from hydrocauli and 3. Manubrium short and broad...... 4 hydrocladia; globular at maturity. – Manubrium elongated narrow ...... 5 Medusa: umbrella 12 mm high, 10 mm wide, 4. Oral rentacles divided 1-2 times (rarely 3); mesoglea thick, umbrellar cavity spacious, umbrella marginal bulbs with 3-4 (rarely more) tentacles; margin square; without gastric peduncle; manubri- ocelli round; male «gonads» extending um short and broad, cross-shaped in transversal sec- cross-wise on subumbrella...... B. muscus tion; 4 oral tentacles with long basal trunk, in distal – Oral tentacles divided 4-6 times; marginal bulbs part divided 4-6 times with small terminal knobs; with about 30 tentacles; ocelli as narrow «gonads» adradial; marginal bulbs triangular, about transversal lines...... B. britannica half as broad than intervals, each provided with 5. Manubrium with a long, narrow throat which about 30 thin tentacles; with linear ocelli, adaxial on project beyond velar opening; marginal bulbs base of each tentacle. with 4 very short tentacles; walls of umbrella thin Records from Mediterranean: Black Sea, hydroid ...... B. maniculata form only? – Manubrium flask-shaped, about half as long as Seasonality: ? bell cavity; walls of umbrella thick; marginal Distribution: Atlantic; Indo-Pacific; Mediter- bulbs with 8 long tentacles; frequently with ranean, Black Sea. medusa buds on manubrium ...... B. niobe References: Thiel (1935); Russell (1953, 1970); Kramp (1961); Vannucci and Rees (1961); Edwards Bougainvillia aurantiaca Bouillon, 1980 (1964, 1966b); Cornelius and Ryland (1990); Boero (Fig. 25D) and Bouillon (1993).

Medusa: umbrella up to 1.9 mm, bell-shaped, Bougainvillia maniculata Haeckel 1864 mesoglea slightly thicker at the apex; manubrium (Fig. 25I) conical, half to two thirds of subumbrellar cavity; with a very slight peduncle; oral tentacles with very Medusa: umbrella 1.5 mm high and wide, almost long basal trunk and branching 2 to 3 times; spherical, with thin walls; manubrium flask-shaped «gonads» as interradial pads; tentacular bulbs broad, with narrow base and long narrow throat tube pro- hemispherical with 2 to 3 marginal tentacles; no jecting beyond velar opening; oral tentacles with ocelli; marginal bulbs and «gonads» coloured in long trunks, divided twice; «gonads» interradial; orange in living animals. marginal bulbs small, globular, each with short fin- Hydroid: unknown. ger-shaped tentacles; ocelli large. Only seen by Records from Mediterranean: eastern Mediter- Haeckel, considered by Mayer (1910) as a degener- ranean. ated form and doubtful species. Known seasonality: 4-5. Hydroid: unknown. Distribution: Indo-Pacific, Mediterranean. Records from Mediterranean: western Mediterranean. References: Bouillon (1980); Goy et al. (1988, 1990, Known seasonality: 3-4. Endemic of the Mediter- 1991); Boero and Bouillon (1993); Schuchert (1996). ranean Sea.

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References: Haeckel (1864); Kramp (1959a, References: Russell (1953, 1970a); Picard 1961); Mayer (1910); Boero and Bouillon (1993). (1958b); Kramp (1961), Vannucci and Rees (1961); Edwards (1964; 1966b); Berhaut (1970); Goy Bougainvillia multicilia (Haeckel, 1879) (1973b); Schmidt and Benovic (1977, 1979); Dowidar (1983); Gili (1986); Benovic and Bender Medusa: umbrella 6 mm high, 5 mm wide, with (1987); Brinckmann-Voss (1987); Calder (1988); thin walls; manubrium globular to flask-shaped, Goy et al. (1988, 1990, 1991); Boero and Bouillon with constricted base; without gastric peduncle; oral (1993); Watson (1994); Avian et al. (1995); Ballard tentacles simple, unbranched! adradial «gonads»; and Myers (1996); Benovic and Lucic (1996); marginal bulbs kidney shaped, with 10-12 tentacles, Medel and López-González (1996); Schuchert each with a red ocelli. Only seen by Haeckel, con- (2001a); Peña Cantero and García Carrascosa sidered by Kramp (1955, 1959a, 1961) as a doubtful (2002). species. Hydroid: unknown. Bougainvillia niobe Mayer, 1894 Records from Mediterranean: Strait of Gibraltar. (Fig. 26C) Seasonality: 3. Distribution: endemic of the Mediterranean Sea. Medusa: umbrella 7 mm high, 5mm wide, with References: Kramp (1955, 1959a, 1961); Boero vertical sides and flat rounded apex, umbrella walls and Bouillon (1993). thick; without gastric peduncle; manubrium flask- shaped; cross-shaped in transversal section, about Bougainvillia muscus (Allman, 1863) half as long as umbrellar cavity; oral tentacles with (Figs. 25J-K, 26A-B) long basal trunks, divided 4 times distally; medusa buds from eight radial side of manubrium; 8 adradi- Hydroid: colonies arising from a irregular net- al «gonads»; marginal bulbs oval, each with 8 tenta- work of tubular stolons; hydroids variable in growth cles, ocelli dark. and form, from dwarf non-fascicled little-branched Hydroid: unknown. colonies to tall, tree-like colonies with profusely, Records from Mediterranean: eastern Mediter- irregularly, branched fascicled hydocauli; perisarc ranean (as B. platygaster). corrugated at base of hydrocladia thinning out over Known seasonality: ? hydranths forming a thin pseudohydrothecae much Distribution: Atlantic; Mediterranean. variable in development; perisarc of hydrocauli and References: Kramp (1959a, 1961); Goy et al. hydrocladia often infested by various detritus; (1988, 1990, 1991); Boero and Bouillon (1993). hydranths cylindrical to fusiform, terminal on hydrocauli and hydrocladia; hypostome short, coni- Bougainvillia platygaster (Haeckel, 1879) cal; with up to 20 amphicoronate filiform tentacles; (Fig. 26D) medusa buds on moderately long stalks, arising singly or in groups on hydrocladia just below the Medusa: umbrella up to 12 mm wide and high, hydranths. globe-shaped to cubical, with thick walls and flat Medusa: umbrella 2-3.5 mm wide and high, semi- top; exumbrella with perradial notches; manubrium globular, mesoglea fairly thick; manubrium bulbous, quadrangular, very flat and broad, 4 times as wide half of subumbrellar height; oral tentacles fairly long, than high; oral tentacles divided 5-6 times almost divided 1-2 (rarely 3-4) times; 4 interradial «gonads» from base; «gonads» flat, as interradial pads; mar- reaching perradii, globular in females and prolonged ginal bulbs small but broad, triangular, with 10-13 along perradial side of peduncle in males; marginal short tentacles; ocelli crescent-shaped; medusa buds bulbs small, with 3-5 (rarely 6-9) long marginal ten- produced directly from manubrium or from poly- tacles; ocelli round; mature eggs covered with a layer poid structures developed on manubrium. of cnidocysts (microbasic euryteles). Hydroid: unknown. Records from Mediterranean: eastern and west- Records from Mediterranean: western Mediter- ern Mediterranean; Adriatic. ranean (Bouillon, pers. obs.) Known seasonality: present all the year. Known seasonality: 5. Distribution: Atlantic, Indo-Pacific, Mediter- Distribution: Atlantic, Indo-Pacific, Mediter- ranean, Arctic. ranean.

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References: Kramp (1961); Winkler (1982); Dicoryne conybeari (Allman, 1864) Pagès et al. (1992), Boero and Bouillon (1993); (Fig. 27A) Bouillon (1995b). Colonies encrusting, living on gastropod shells, Genus Dicoryne Allman, 1859 hydrorhiza anastomosing, giving rise single stalked hydranths or monosiphonic and branched stems up Hydrocaulus erect, branched or unbranched; to 10 mm; branching irregularly acute; perisarc perisarc conspicuous, terminating on or below pale brown, transversely wrinkled, distending hydranth body, never continued over tentacles base; slightly distally. Hydranths pale brown, slightly hydranths with one distal whorl of filiform tentacles; dilated above, tentacles straight, up to 12 in one gonophores on gonozooids (blastostyles) and amphicoronate circlet, upper ones the longer, con- released as free-swimming styloid sporosacs, flagel- tracting partly within perisarc tube. Gonophores lated and provided with one or two tentacles arising ovoid, on blastostyles borne on stolon and bearing from their proximal, originally attached end. cnidocysts distally, releasing sporosacs with one Reference: Schuchert (1996, 2001a). ciliated process. Records from Mediterranean: Adriatic, eastern 1. Hydranth with about 12 tentacles; released and western Mediterranean. sporosacs with single ciliated process...... Distribution: northeastern Atlantic; Mediter- ...... D. conybeari ranean. – Hydranth with up to 16 tentacles; released References: Motz-Kossowska (1905); Cornelius sporosacs with two ciliated processes...... and Ryland (1990); Boero and Bouillon (1993); ...... D. conferta. Avian et al. (1995); Avian et al. (1995); Medel and López-González (1996). Dicoryne conferta (Alder, 1856) (Fig. 26E-G) Genus Garveia Wright, 1859

Colonies up to 25 mm growing on gastropod Hydrocaulus erect and branched, monosiphonic shells; hydrorhiza reticulate, without spines, or polysiphonic; hydranth fusiform, hypostome clothed with perisarc, giving rise hydrocauli dome-shaped, conical, surrounded by one distal monosiphonic, unbranched or irregularly whorl of tentacles; pseudohydrothecae covering branched; axis increasing in diameter from base polyp base but not extending over tentacles; to distal end, clothed with thick perisarc which gonophores as fixed sporosacs, borne on pedicels on terminates below hydranth. Branches living stem hydrocauli or on hydrorhiza. at acute angle. Perisarc wrinkled, especially Reference: Calder (1988). basally. Hydranth with one whorl of 10-13 fili- form tentacles. Blastostyles borne on stem or on 1. Branches adnate to the main axis basally ...... hydrorhiza, they are modified polyps without ...... G. grisea mouth or tentacles, but with a long and extensile – Branches separated of the main axis for all their hypostome with cnidocysts; gonophores in a length...... 2 dense cluster below hypostome; colonies dioe- 2. Hydrocauli monosiphonic, up to 12cm. high, cious. Gonophores as free-swimming, ciliated regularly branched, hydrocladia on short sporosacs with two tentacles basally; the female intervals and densely branched .. G. franciscana containing two eggs. – Hydrocauli polysiphonic basally, up to 4 cm. Records from Mediterranean: Adriatic, eastern high, not with a regular branching appearance, and western Mediterranean. hydrocladia at irregular intervals and not densely Distribution: north Atlantic from Arctic to the branched...... G. nutans Mediterranean; but also recorded in South-Africa. References: Broch (1916) as Bouigainvillia Garveia franciscana (Torrey, 1902) conferta; Millard (1975); Boero and Bouillon (Figs. 27B-D) (1993); Altuna (1994); Avian et al. (1995); Medel and López-González (1996); Schuchert Colonies erect and branched, up to 12 cm high; (2001a). hydrocauli monosiphonic, thick, wrinkled and with

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several annuli at the beginning of branches; perisarc ovoid with apical truncated point, grouped on mid- pale brown. Hydrocladia lateral and alternate, at region of stem and main major branches, borne on acute angle with the axis, alternately branched; short pedicels. polyps borne on pedicels at secondary branches. Records from Mediterranean: Adriatic, western Hydranth fusiform surrounded basally by a pseudo- Mediterranean. hydrotheca, hypostome conical, 14-16 filiform ten- Distribution: boreal and temperate waters around tacles in one whorl. Colonies dioecious, gonophores the world. fixed sporosacs borne on short pedicels below the References: Leloup (1952) as Bimeria; Cornelius polyps, males ovoid and elongated, females spheri- and Ryland (1990); Ramil and Vervoort (1992a); cal and smaller than males and containing 1-2 eggs. Boero and Bouillon (1993); Avian et al. (1995); Records from Mediterranean: eastern and west- Medel and López-González (1996). ern Mediterranean, Adriatic Sea. Known seasonality: 9. Genus Koellikerina Kramp, 1939 Distribution: cosmopolitan in temperate and tropical waters. Hydroid: known only for K. fasciculata: colonies References: Morri (1982, 1986); Gili (1986); arising from a creeping hydrorhiza formed by tubular Boero and Bouillon (1993); Medel and López- stolons; hydrocauli and hydrocladia erected, González (1996). branched and recovered by perisarc incrusted with mud and various detritus; perisarc forming a wrinkled Garveia grisea (Motz-Kossowska, 1905) pseudohydrothecae recovering hydranth and base of (Figs. 27E) the tentacles, living only hypostome free; hydranth fusiform to pear-shaped, with conical hypostome, Colonies erect and branched, up to 3 cm high; with an irregular whorl of up to 14 filiform tentacles, hydrocauli monosiphonic or polysiphonic basally, slightly knobbed at end; medusae bud stalked, borne thick, without annulations, perisarc grey. Hydrocla- singly on hydrocauli and hydrocladia. dia alternate, adnate to the hydrocauli at their basal Medusa: Bougainvilliidae with 8 groups of mar- portion, giving rise secondary hydrocladia with the ginal tentacles, 4 perradial and 4 interradial, all alike same disposition. Hydranth on secondary branches, in structure; with 4 oral perradial dichotomously covered basally by a pseudohydrotheca, with 7-10 branched tentacles; «gonads» on manubrium in filiform tentacles in one whorl, hypostome conical. adradial; interradial or perradial position; with or Gonophores fixed sporosacs, borne on hydranth without ocelli. The endoderm of the gastric cavity of pedicels, ovoid, isolated or paired; the female with the Koellikerina presents numerous conspicuous only one egg. endodermal expansions sustained by a mesoglean Records from Mediterranean: western Mediter- axis and containing excretory vacuoles (see Bouil- ranean. lon, Boero and Seghers, 1988a). Known seasonality: 10-6. Remark: the hydroids described as Thamnostoma Reproduction: 10-1. probably belong to the genus Koellikerina, see Distribution: endemic of the Mediterranean Sea. Petersen and Vannucci (1960). References: Rossi (1961); Morri (1982); Boero and Bouillon (1993); Medel and López-González Koellikerina fasciculata (Péron and Lesueur, 1810) (1996); Medel (1996). (Figs. 27H-L)

Garveia nutans (Wright, 1859) Hydroid: see genus characters. (Figs. 27F-G) Medusa: umbrella 12 mm wide, 12 mm high, barrel-shaped to bell-shaped, with flatly rounded Colonies about 25 mm high, composed of erect apex and thick walls; manubrium on short, broad and branched hydrocauli, polysiphonic basally, gastric peduncle with quadrangular base; oral tenta- branching mainly from alternate sides of stem. cles divided 7 times to form a dense network; 4 per- Perisarc pale brown, irregularly wrinkled, thin and radial horseshoe-shaped «gonads» with transverse becoming transparent under the hydranth, and form- furrows; 4 radial canals; 8 marginal bulbs, each with ing a pseudohydrotheca around its base. Polyp pear- 10-23 tentacles; with dark red adaxial ocelli at base shaped, with 10-12 filiform tentacles. Gonophores of each tentacle.

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Records from Mediterranean: eastern and west- Tortella (1986); Gili (1986); Gili et al. (1987, 1988); ern Mediterranean; Adriatic Sea; Black Sea. Boero and Bouillon (1993); Avian et al. (1995); Known seasonality: 3-7. Benovic and Lucic (1996); Medel and López- Distribution: Atlantic; Indo-Pacific (Red Sea, González (1996); Mills et al. (1996). Indian Ocean); Mediterranean; Antarctic. References: Thiel (1935); Ranson (1936); Babnik Lizzia fulgurans (A. Agassiz, 1865) (1948); Petersen and Vannuci (1960); Goy (1973b); (Fig. 28E) Vannucci and Navas (1973a); Gili (1986); Brinck- mann-Voss (1987); Gili et al. (1987, 1988); Pagès et Medusa: umbrella 1 mm high, somewhat pyri- al. (1992); Boero and Bouillon (1993); Benovic and form, mesoglea very soft and flexible; manubrium Lucic (1996); Avian et al. (1995); Medel and López- small; with a well developed, fairly long, pyramidal González (1996). gastric peduncle, 1/3 umbrellar cavity; 4 simple oral tentacles; medusa buds on interradial walls of Genus Lizzia Forbes, 1846 manubrium; 8, sometimes 16 marginal tentacles, stiff, carried curled upward, one on each marginal Medusa: Bougainvillidae with simple, unbran- bulbs, no ocelli. ched oral tentacles; with usually 8 marginal bulbs Records from Mediterranean: western Mediter- (exceptionally 16, Lizzia fulgurans) each with one ranean. solitary marginal tentacles or with unequal groups of Known seasonality: 6-7. marginal tentacles. Distribution: Atlantic, Mediterranean. Hydroid: unknown References: Kramp (1961); Brinckmann-Voss (1987); Boero and Bouillon (1993). 1. With more than one marginal tentacle on each marginal bulb and more tentacles on marginal Lizzia octostyla (Haeckel, 1879) perradial bulbs than on interradial ones ...... (Fig. 28F) ...... L. blondina – With solitary marginal tentacles...... 2 Medusa: umbrella 0.4 mm high, 5 mm wide, with 2. With 4 oral tentacles; 8, sometimes 16 solitary bulging sides and low conical apex; manubrium on marginal tentacles ...... L. fulgurans a well developed peduncle; 8 simple knobbed oral – With 8 oral tentacles, in four perradial pairs; 8 tentacles situated in pairs in the four perradial cor- marginal solitary tentacles...... L. octostyla ners of the mouth tube; 4 swollen interradial «gonads», medusa buds on manubrium; 8 short Lizzia blondina Forbes, 1848 equally developed marginal tentacles with small (Figs. 28A-D) basal bulbs, old specimens sometimes with addi- tional tentacles on each perradial bulb; no ocelli. Medusa: umbrella 1-2 mm high and wide, semi- Records from Mediterranean: western Mediter- globular, with fairly thick apex; manubrium, short, ranean; Adriatic Sea. cone-shaped, with quadrangular base; with a short Known seasonality: 8-10. pyramidal gastric peduncle; 4 simple small oral ten- Distribution: endemic of Mediterranean Sea. tacles, each with one terminal knob of cnidocysts; References: Kramp (1961); Boero and Bouillon gonad interradial completely surrounding manubri- (1993); Benovic and Lucic (1996). um, ring-shaped; medusa buds on manubrium, before the «gonads» are ripe; 8 marginal bulbs, 4 Genus Nubiella Bouillon, 1980 perradial bulbs with up to 3 tentacles, 4 interradial bulbs never with more than one, frequently not all Bougainvillidae with simple unbranched oral tentacles developed; no ocelli. tentacles; with 4 solitary marginal tentacles. Records from Mediterranean: western Mediter- ranean; Adriatic Sea. Nubiella mitra Bouillon, 1980 Known seasonality: 1-12. (Fig. 28G) Distribution: Atlantic, Mediterranean. References: Kramp (1961); Berhaut (1970); Goy Medusa: umbrella 2.1 mm high, 1.6 mm wide, (1973b); Schmidt and Benovic (1979); Castelló i mitre-shaped, with a thick conical apical mesoglean

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projection, lateral walls of umbrella of uniform Pachycordyle napolitana Weismann, 1883 thickness, manubrium cylindrical, 2/3 umbrellar (Fig. 28H) cavity height; with a small gastric peduncle; mouth circular, 4 oral tentacles with a rather large cnido- Colonies stolonal, with reticular hydrorhiza grow- cyst knob; radial and circular canal narrow; ing over a gastropod shell. Pedicels of varied length but «gonads» encircling completely the manubrium usually less than 1 mm long, slender basally, widening except the most distal and proximal areas; 4 thin distally, bearing a distal hydranth. Perisarc moderately solitary marginal tentacles, their distal half thicker thin, wrinkled throughout, terminating at base of and armed with cnidocysts; marginal tentacular hydranth, pseudohydrotheca absent. Hydranths club- bulbs small, spherical; no ocelli; medusary buds in shaped to spindle shaped, with about 16 to 20 filiform the aboral part of manubrium, immediately under tentacles in three or four close whorls, tentacles of one the gastric peduncle. whorl alternating with those of adjacent whorls. Proxi- Hydroid: unknown. mal tentacles often smaller than distal ones. Hypos- Records from Mediterranean: eastern Mediter- tome dome-shaped. Gonophores arising simply from ranean. hydranth pedicel on short wrinkled stalk, completely Seasonality: ? invested with perisarc. Distribution: Indo-Pacific; Mediterranean. Records from Mediterranean: western and east- References: Bouillon (1980, 1985a, 1995a); Goy ern Mediterranean. et al. (1988, 1990, 1991); Boero and Bouillon Seasonality: ? (1993). Distribution: western Atlantic, Bermuda, Mediterranean. Genus Pachycordyle Weismann, 1883 References: Morri (1981); Calder (1988); Boero =Clavopsella Stechow, 1919a in part = Thieliana and Bouillon (1993); Schuchert (2004). Stepanjants, Timoshkin, Anokhin and Napara, 2000 Pachycordyle pusilla (Motz-Kossowska, 1905) Bougainvilliidae with well developed creeping (Fig. 30H) colonies, with branched or unbranched hydrocauli; perisarc terminating at base of hydranth; hydranths Colonies minute stolonal colonies (up to 2 mm) club-shaped to spindle-shaped, with 2-4 alternating composed of unbranched pedicels ended by close whorls of filiform tentacles beneath hypos- hydrothecae; perisarc thick, annulated basally, tome, hypostome dome-shaped. Gonophores borne widening gradually towards distal extreme, taking a on stem, as fixed sporosacs or free eumedusoids funnel appearance; polyps elongated, 8-12 filiform without marginal tentacles, mouth or oral tentacles, tentacles scattered through distal half; gonophores radial canals or ring canal, seldom with velum, fixed sporosacs, ovoid-elongated, borne distally on manubrium simple surrounded by gonads, no sense hydranth pedicels. organs; they correspond to highly reduced Records from Mediterranean: eastern and west- medusae, resembling medusoid forms of ern Mediterranean, Ligurian Sea. siphonophores. Known seasonality: 3,4,8,10,12. Remark: Pachycordyle has been include in the Distribution: endemic of the Mediterranean Sea. subfamily Pachycordylinae by Calder (1988) that References: Motz-Kossowska (1905); Morri Schuchert (2004) erected to the family level the (1981); Gili (1986); Roca (1986); Boero and Bouil- Pachycordylidae but is here maintained in the lon (1993); Medel and López-González (1996) all as Bougainvilliidae with which they present most Cordylophora pusilla. Schuchert (2004) as Pachy- affinities. cordyle pusilla. References: Calder (1988); Stepanjants et al. (2000); Schuchert (2004). Genus Rhizorhagium M. Sars, 1874 = Aselomaris Berrill, 1948 1. Gonophores as eumedusoids, distal end of = Clavopsella Stechow 1919a in part perisarc not distinctly double-layered and not = Gravelya Totton, 1930 expanded ...... P. napolitanai – Gonophores as sessile sporosacs, distal end of Hydrocauli erect, unbranched, bearing a single ter- perisarc double layered and expanded P. pusilla minal hydranth and, rarely, one or two lateral ones as

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well; perisarc firm, continued over polyp as a pseudo- Genus Thamnostoma Haeckel, 1879 hydrotheca, but never investing tentacle bases, excep- tionally with pseudohydrotheca stopping just above Medusa: Bougainvilliidae with 4 dichotomously base of hydranth body (R. michaeli); hydranth with branched oral tentacles, with 4, 8 or more solitary one distal whorl of filiform tentacles, hypostome nip- marginal tentacles; with interradial «gonads»; with ple-shaped or dome-shaped; gonophores as fixed or without ocelli. sporosacs, borne on hydrorhiza and stems. Hydroid: unknown. References: Hirohito (1988); Calder (1991); Schuchert (1996, 2001a). Thamnostoma dibalia (Busch, 1851) (Fig. 29D) 1. Hydranth with pseudohydrotheca reduced to base of hydranth body...... R. michaeli Umbrella 7 mm high, 6mm wide; manubrium – Hydranth with a pseudohydrotheca extending cubical; without gastric peduncle; with 4 interradial over hydranth body ...... R. arenosum «gonads»; oral tentacles divided two or three times; 4 marginal tentacles; basal bulbs with ocelli. Rhizorhagium arenosum (Alder, 1862) Records from Mediterranean: western Mediter- (Fig. 29A) ranean; Adriatic Sea. Known seasonality: 5; 7-11. Stolonal colonies, hydrocaulus short, generally Distribution: endemic of Mediterranean Sea. covered with minute grains of sand or with mud; References: Kramp (1961); Benovic (1976); hydranth enveloped by a pseudohydrothecae that Schmidt and Benovic (1979); Gili (1986); Boero and does not envelop tentacles, with 6 - 12 long, slender Bouillon (1993); Avian et al. (1995); Benovic and distal tentacles in one whorl, amphycoronate; Lucic (1996); Medel and López-González (1996). gonophores reduced to sporosacs, usually two in number, pyriform shortly stalked borne on the lower Genus Velkovrhia Matjasic and Sket, 1971 half of the hydrocaulus. Records from Mediterranean: western Mediter- Fresh-water bougainvilliids forming erect colonies ranean. covered by perisarc; hydranths with two whorl of fili- Seasonality: ? form tentacles, no pseudohydrotecae. Gonophores as Distribution: Atlantic; Mediterranean. styloid fixed sporosacs, borne on hydrocauli. References: Hincks (1868); Berril (1948); Boero and Bouillon (1993) Avian et al. (1995). Velkovrhia enigmatica Matjasic and Sket, 1971 (Fig. 29E) Rhizorhagium michaeli (Berril, 1948) (Figs. 29B-C) Diagnosis as for the genus. Records from Mediterranean: Caves near Ljubla- Stolonal colonies densely creeping, with small jana and near Karlovac. polyps on peduncles that elongate with age. Distribution: not known. Hydranth with pseudohydrotheca stopping just Reference: Clausen and Salvini-Plawen (1986). above base of hydranth, hypostome conical, 9-12 fil- iform tentacles in one whorl; new polyps originated Family BYTHOTIARIDAE directly from the hydrorhiza. Gonophores fixed Maas, 1905 (= Calycopsidae) sporosacs (cryptomedusoids), arising at distal end of the hydrocaulus; the female gonophore produces up Hydroid: hydrorhiza plate-like, giving rise to to eight large ova each covered by single-layered unbranched colonies living in ascidian prebranchial cav- “armor” composed of functional cnidocysts. ities; hydranths sessile, with up to five irregular whorls Records from Mediterranean: western Mediter- of filiform tentacles; medusae buds arising from polyps. ranean. Medusa: 4 lips, simple or crenulated; with or Seasonality: ? without centripetal canals; “gonads” simple or fold- Distribution: Atlantic; Mediterranean. ed, adradial or interradial, on manubrial wall; 4 or 8 References: Piraino (1991, 1992); Boero and radial canals, simple or branching; 4, 8 or more hol- Bouillon (1993). low marginal tentacles (mesoglea of distal part of

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tentacles often enlarged and strongly reducing endo- Genus Calycopsis Fewkes, 1882 dermal axis), each terminating in a large cnidocyst cluster, with basal portion often adnate to exumbrel- Medusa: Bythotiaridae with unbranched radial la; marginal bulbs highly reduced or absent; with or canals; with centripetal canals; «gonads» transverse- without rudimentary or dwarf solid tentacles (Eume- ly folded, often forming 8 adradial rows; marginal dusa); rarely with abaxial ocelli. tentacles of similar structure with cnidocysts only on References: Bouillon et al., 1988a); Pagès, Gili and the terminal knob and with adnate base. Bouillon (1992); Bouillon (1995); Schuchert (1996); Hydroid: unknown. Brinckmann-Voss and Arai (1998); Bouillon (1999); Bouillon and Barnett (1999); Bouillon and Boero (2000). Calycopsis simplex Kramp and Damas, 1925 (Fig. 30C) Key to hydroids (see family character) Medusa: umbrella 8 mm high, 8.5 mm wide, Key to medusae almost globular; mesoglea thick at the umbrella apex; manubrium cruciform, with large base, about half as 1. With centripetal canals, blind or joining base of long as umbrellar cavity; mouth with four simple lips; manubrium...... Calycopsis radial canals and circular canal narrow; «gonads» – No centripetal canals; radial canals bifurcated interradial, each with a longitudinal median groove (some few additional branches may occur as and often a few transverse folds; four blind, interradi- abnormalities)...... Bythotiara al centripetal canals; eight tentacles, all alike, with a terminal cnidocyst knob, no marginal bulbs but ten- Genus Bythotiara Günther, 1903 tacular base adnate to the exumbrella. Hydroid: unknown. Hydroid: when known see family diagnosis. Records from Mediterranean: western Mediter- Medusa: Bythotiaridae with 4 simple or branch- ranean. ing radial canals; without centripetal canals; Known seasonality: 12. «gonads» interradial with transverse furrows; with Distribution: Atlantic, Mediterranean. or without rudimentary or dwarfed tentacles entirely References: Kramp (1961); Goy (1973b); Boero covered with cnidocysts. and Bouillon (1993); Gili et al. (1998).

Bythotiara murrayi Günther, 1903 Family CLAVIDAE McCrady, 1859 (Figs. 30A-B) Hydroid: colonies stolonal or erect, branched, mono- Medusa: umbrella up to about 20 mm wide and siphonic or polysiphonic, arising from tubular, ramified high, globe-shaped, with thick walls; manubrium hydrorhiza; hydranths sessile or pedicellate, naked, small, barrel-shaped; mouth with 4 simple lips; gen- occasionally covered or retractable into a thin perisarc erally 4 radial canals bifurcating near point of origin cone or tube (Clava, Merona, Rhizogeton, Tubiclava); in 8 straight canals joining circular canal (occasion- with filiform tentacles scattered over hydranth body ally branching again); in adults as many long prima- (oral and distal part of hydranth); nematophores present ry tentacles as ends of radial canals, generally 8, or absent. Gonophores as free medusae or fixed ending in terminal swellings; some secondary tenta- sporosacs developing from hydrorhiza, hydrocaulus, or cles and minute dwarf tentacles; 4 interradial from hydrorhizal blastotyles. «gonads», with transverse furrows. Medusa: Anthomedusae with a bell-shaped umbrel- Hydroid: unknown. la; with short manubrium; with a gastric gelatinous Records from Mediterranean: eastern and west- peduncle or with vacuolated endodermal cells forming ern Mediterranean; Adriatic Sea. a pseudo-peduncle; mouth armed with a continuous Known seasonality: 2; 4; 5; 7-9; 11; 12. row of sessile cnidocyst clusters along whole margin; Distribution: Atlantic; Indo-Pacific; Mediterranean. with 4 radial canals and circular canal; with solitary References: Kramp (1961); Benovic and Bender solid tentacles, numerous in adults; “gonads” on inter- (1986, 1987); Bouillon et al.(1988a); Pagès , Bouillon radial walls of manubrium; with adaxial ocelli. and Gili (1991); Pagès, Gili and Bouillon (1992); References: Wedler and Larson (1986); Calder Avian et al. (1995); Benovic and Lucic (1996). (1988); Migotto (1996); Schuchert (1996, 2001a,

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2004); Bouillon (1995, 1999); Bouillon and Barnett Genus Clava Gmelin, 1791 (1999); Bouillon and Boero (2000). Remark: The genus Clava presents undeniable Hydroid: with stolonal colonies; hydrorhiza giv- relations with the hydractiniids (see Bouillon et al. ing rise directly to sessile hydranths; hydranth naked 1997) and has been include in this family by except a low perisarcal collar round base, with con- Schuchert (2001a) who reintroduced the name Cordy- ical hypostome, undifferentiated endoderm and fili- lophoridae von Ledenfeld, 1885 for the remaining form tentacles scattered throughout the body. genera of the former family Clavidae. Schuchert Gonophores as fixed sporosacs (cryptomedusoids) (2004) becoming aware of the existence of family borne by the hydranth below the tentacles. Oceanidae Eschscholtz 1829 proposed to replace the References: Rossi et al. (2000); Schuchert (2001a). junior family Cordylophoridae by the latter family name. The author underlying himself that the macro- Clava multicornis (Forskål, 1775) taxonomy of the Oceanidae must be regarded as pro- (Fig. 30D) visional and that the taxonomical validity of the genus Oceania has to be confirmed. The nomenclature inci- Stolonal colonies, polyps nude, up to 5.5 mm dences of those changes are complicated by the fact high, reddish, usually grouped; 20-40 filiform tenta- that the name Clavidae Mc Crady 1859 predates the cles scattered over the distal half of the hydranth. Hydractiniidae Agassiz, 1862 threatening the latter Gonophores spherical shortly pedicellate, borne name if the two are considered synonyms. Presently below lower tentacles, grouped in “bunch”, in one we consider better to maintain the current usage till whorl of up to 80 gonophores; cryptomedusoids. more definitive information, like molecular phyloge- Colonies dioecious. Cnidocysts: desmonemes (2x5 netic investigations, have been well sorted out. mm) and microbasic euryteles (5x8 mm). Records from Mediterranean: Adriatic, eastern Keys to polyps and western Mediterranean. Known seasonality: 5, 6, 7, 11. 1. Colony erect and freely branched ...... 2 Reproduction: 6, 7. – Colony stolonial, hydroids at most slightly Distribution: eastern and western north-Atlantic, branched; hydranth, or at least its pedicel, Mediterranean, Arctic Seas. surrounded by perisarc ...... 4 References: Leloup (1952); Naumov (1960); Gili 2. Branches not adnate to stem; gonophores as (1986); Roca (1986); Cornelius and Ryland (1990); fixed sporosacs...... Cordylophora Boero and Bouillon (1993); Altuna (1994); Avian et al. – Branches adnate to stem for some distance; (1995); Medel and López-González (1996); Schuchert gonophores as fixed sporosacs or free medusae (2001a); Peña Cantero and García Carrascosa (2002)...... 3 3. Gonophores producing free medusae...... Genus Cordylophora Allman, 1844 ...... Turritopsis – Gonophores as fixed sporosacs... Corydendrium Hydroid: Clavidae with erect colonies, hydro- 4. Hydranth retractable into perisarcal tube; caulus unbranched or monopodially branched with gonophores on separate blastostyles; terminal hydranths; hydranths naked, fusiform, nematothecae present...... Merona hypostome conical and with scattered filiform tenta- – Hydranth not retractable into perisarcal tube; cles over much of the body. Gonophores as fixed gonophores on hydranth body no nematothecae. sporosacs on hydranth pedicels, larvae and young ...... Clava polyps may develop within gonangia. Reference: Schuchert (1996, 2004). Key to genera with free medusae Cordylophora caspia (Pallas 1771) 1. With manubrium mounted upon a short, solid, (Figs. 30E-G) pyramidal, gelatinous, peduncle without endodermal vacuolated cells...... Oceania Colonies stolonal or with erect hydrocauli – With manubrium mounted upon a pseudo- branched or unbranched, up to 4-8 cm high; perisarc peduncle formed by highly vacuolated smooth, corrugated or ringed at the base of branch- endodermal cells ...... Turritopsis ing. Hydranth with 12-24 filiform tentacles scattered

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throughout the polyp. Gonophores fixed sporosacs, tube into which they can withdraw completely, and ovoid to spherical, sessile or pedicellate, borne on with scattered, filiform tentacles over much of the stem or on hydranth pedicels. body; gonozooids without mouth and tentacles, with Records from Mediterranean: Adriatic, western short perisarc tube around its base and borne on the Mediterranean, Caspian Sea. stolon, producing fixed sporosacs, dactylozooids Distribution: cosmopolitan, mainly in temperate waters. borne on stolon, usualy enclosed in a perisarc tube References: Morri (1981); Boero and Bouillon (nematotheca). (1993) Avian et al. (1995); Schuchert (2004). Reference: Medel et al. (1993); Schuchert (2004). Genus Corydendrium Van Beneden, 1844 1.- Female gonozooids without cnidocysts; Colonies with erect, polysiphonic and irregularly gonophores with a small number of big eggs ..... branched hydrocauli; branches adnate to hydrocaulus, ...... M. cornucopiae. or to other branches over part or all of their lengths; – Female gonozooids with cnidocysts at the apex; perisarc firm, covering up to hydranth base; hydranth gonophores with great number of small eggs ..... elongate, tubular, tentacles filiform and scattered over ...... M. ibera the body. Gonophores as fixed sporosacs enclosed in perisarc, arising as blind, elongate sacs of coenosarc Merona cornucopiae (Norman, 1864) below hydranths and within perisarcal tubes of hydro- (Figs. 31D-E) cauli and hydrocladia branchlets. Reference: Calder (1988); Schuchert (2004). Hydrorhiza reticulate, growing on the bivalve mol- lusc Gouldia minima. Polyps arising directly from the Corydendrium parasiticum (Linnaeus, 1767) stolon; gastrozooids surrounded by perisarc tube into (Figs. 31A-C) which it can withdraw completely; tube gradually widening towards distal end and scarcely transparent, Hydrocauli erect and polysiphonic, up to 4.5 cm often with adhering sediment particles; up to 20 tenta- high, perisarc firm, moderately thick, smooth or with cles scattered over distal half of the hydranth. Dacty- some wrinkles; often encrusted with detritus and silt. lozooids numerous, scattered over stolon, each sur- Branching irregular in one or more planes, branches rounded by a strong perisarc tube, widening towards adnate to main axis basally, gradually curving out- distal end and there becoming wineglass-shaped. wards and becoming free distally; secondary branches Gonozooids of both sexes different and in separated may occurs in the same way. Perisarc becoming thin at colonies; male gonozooids short and thick, with 16-20 hydranth base, ending below tentacles. Polyps elon- gonophores in a dense cluster on the upper part, like a gate, constricted basally (below perisarcal tube), tenta- mulberry. The female gonozooids have a longer pedi- cles filiform (40 or more) scattered, hypostome coni- cel than the males and the distal half of the body bears cal. Gonophores wholly contained within perisarcal 15-20 shortly stalked gonophores arranged randomly, tube, arising from coenosarc and lying parallel to it, as each gonophore being ovoid and mucronate at the long, slender cylinders without spadix; the female apex. Cnidocysts are present on gastrozooids, dactylo- with about 13 eggs. Cnidocysts: desmonemes and het- zooids and stolon but not on female gonophore. erotrichous microbasic euryteles. Cnidocysts: microbasic euryteles, and desmonemes. Records from Mediterranean: western Mediter- Records from Mediterranean: western Mediter- ranean. ranean, Naples. Distribution: temperate and tropical waters Known seasonality: 5. around the world. Distribution: temperate waters around the world. References: Motz-Kossowska (1905); Millard References: Rees (1956a); Cabioch (1965); Gili (1975); Calder (1991); Boero and Bouillon (1993); (1986); Millard (1975); Ramil (1988); Medel et al. Medel and López-González (1996); Schuchert (2004). (1993); Boero and Bouillon (1993); Medel and López-González (1996); Schuchert (2004). Genus Merona Norman, 1865 Merona ibera Clavidae with stolonal polymorphic colonies; Medel, García-Gómez and Bouillon, 1993 gastrozooids unbranched, surrounded by a perisarc (Figs. 31F-H)

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Hydrorhiza reticulate giving rise directly unbranched References: Metschnikoff (1886a); Babnik (1948); gastrozooids, gonozooids and dactylozooids. Gastro- Kramp (1961); Dowidar (1983); Benovic and Bender zooids surrounded by perisarc tube into which it can (1987); Brinckmann-Voss (1987); Goy et al. (1988, withdraw completely; tube gradually widening towards 1990, 1991); Boero and Bouillon (1993); Avian et al. end and scarcely transparent, often with adhering sedi- (1995); Benovic and Lucic (1996); Schuchert (2004). ment particles. Body of gastrozooid with up to 20 fili- form tentacles scattered over distal half. Dactylozooids Genus Turritopsis McCrady, 1857 numerous, scattered over entire stolon, each surrounded by a strong perisarc tube, widening towards end there Clavidae with stolonal or erect colonies; hydrocaulus becoming wineglass-shaped. Large microbasic euryteles monosiphonic in small colonies, polysiphonic in larger occurring at the apex of each dactylozooid. Female irregularly branched and increasing in diameter from base gonozooids pinkish, each with a short wide collar of to distal end; hydrocladia adnate and parallel to hydro- perisarc covering the base. Gonophores at distal third of caulus or to other hydrocladia for some distance, before blastostyle, cylindrical, elongate, containing small eggs curving away at an acute angle and becoming free; hydro- regularly distributed in two or three rows along axial caulus and hydrocladia covered by a firm double-layered spadix. Extreme of apex of gonophore button-shaped, perisarc, mostly infested with detritus and algae, armed with ellipsoid microbasic euryteles. hydranths terminal, naked, elongated, fusiform, with fili- Records from Mediterranean: only record from the form tentacles irregularly scattered over distal three quar- Strait of Gibraltar (Mediterranean side, Algeciras Bay). ters of hydranth. Gonophores giving rise to free medusae; Known seasonality: 8. buds arising mostly one by one from short stems or Distribution: unknown. pedicels below hydranths, enclosed in perisarc. References: Medel et al. (1993); Medel and Medusa: with family characters but with a pseudo- López-González (1996); Schuchert (2004). peduncle formed by highly vacuolated endodermal cells. Hydroid: the polyp stages are indistinguishable. Genus Oceania Péron and Lesueur, 1810 References: Calder (1988); Schuchert (1996, 2004). Remarks: Schuchert (2004) consider that the Hydroid: not known from field, Metschnikoff Mediterranean species of Turritopsis is different (1886a) obtained ramified colonies with claviform from the eastern Atlantic species Turritopsis nutric- hydranths having up to 13 filiform tentacles alter- ula McCrady, 1857 and the North Sea species T. nating in three whorls; gonophores not known. polycirrha (Keferstein, 1862) and correspond to Medusa: Clavidae with a short, solid, pyramidal, Turritopsis dohrnii (Weismann, 1883). It is however gelatinous, peduncle without endodermal vacuolat- not excluded that T. dohrnii and T. nutricula coexist ed cells. in the Mediterranean or that Turritopsis dohrnii cor- Reference: Schuchert (1996); Schuchert (2004). respond to a dwarf form of T. nutricula, dwarfism being a well known phenomenon in Mediterranean Oceania armata Kölliker, 1853 species: (Fage, 1952, Goy, 1995). (Figs. 31I-L) The records of Turritopsis from this area (Kramp, 1959; Schmidt, 1973; Dowidar, 1984; Goy Hydroid: see genus characters. et al, 1991) have all to be reconsidered. Medusa: umbrella 8-10 mm wide and high, bell- shaped to pyriform, with flat top, walls uniformly thin; Key to medusae manubrium flask-shaped, cruciform in transverse sec- tion, on a shallow mesoglean peduncle; mouth rim 1. 14 to 32 marginal tentacles; 1.8 to 2.7 mm crenulated, with a continuous row of spherical sessile of bell size ...... T. dohrnii cnidocyst clusters; 100-200 marginal solid tentacles, – 40 to 100 marginal tentacles; 3 to 4, up to 6 mm densely crowded, marginal bulbs elongated alternately ...... T. nutricula slightly displaced adaxially and abaxially; «gonads» on interradial walls of manubrium; with adaxial ocelli. Turritopsis dohrnii (Weismann, 1883) Records from Mediterranean: eastern and west- (Fig. 32D) ern Mediterranean; Adriatic Sea; Black Sea? Known seasonality: 1-9; 12. Colonies of variable height, irregularly branched Distribution: Atlantic, Indo-Pacific, Mediterranean. hydrocaulus monosiphonic in small colonies, polysi-

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phonic in larger; branches adnate and parallel to the 4 compact vacuolated endodermal masses situated hydrocaulus or to other branches for some distance, above digestive part of manubrium; four lipped mouth before curving away at an acute angle and becoming with a continuous row of sessile cnidocyst clusters free; hydrocaulus and hydrocladia recovered by a along margin; 80-120 closely spaced marginal tenta- firm perisarc, consisting of two layers, mostly infest- cles; «gonads» interradial, mature females often with ed with detritus and algae, without annulations and developing embryos and planulae; with adaxial ocelli. terminating below hydranth base; hydranths terminal, Records from Mediterranean: eastern and west- naked, elongated, fusiform, with 12-20 filiform tenta- ern Mediterranean; Adriatic. cles scattered over distal three quarters of hydranth; Known seasonality: 3, 6-11. hypostome elongated conical; medusae buds arising Reproduction: 7, 8. mostly one by one from short stems below hydranths, Distribution: Atlantic, Indo-Pacific, Mediter- pear shaped, enclosed in perisarc. ranean. Medusa: umbrella up to 2.7 mm in height, 3.2 mm References: Vervoort (1968); Schmidt (1973); in diameter, bell-shaped to perform, higher than wide, Dowidar (1983); Boero and Fresi (1986); Brinck- mesoglea thicker at apex; manubrium large, cross- mann-Voss (1987); Goy et al. (1988, 1990, 1991); shaped in transverse section, red in colour; 4 radial Bavestrello et al. (1992); Ramil and Vervoort (1992a); canals which appears to overtop 4 compact vacuolated Boero and Bouillon (1993); Avian et al. (1995); Medel endodermal masses situated above digestive part of and López-González (1996); Piraino et al. (1996); manubrium; four lipped mouth with a continuous row Schuchert (1996); Peña Cantero and García Carras- of sessile cnidocyst clusters along margin; 14-32 close- cosa (2002); Schuchert (2004). ly spaced marginal tentacles sometimes with swollen tips; gonochoristic «gonads» interradial, infour distinct Family CYTAEIDIDAE L. Agassiz, 1862 blocks; with adaxial ocelli rust coloured. Records from Mediterranean: western Mediter- Hydroid: colony usually non-polymorphic, ranean; Adriatic. hydrorhiza reticulate, covered by perisarc, without Known seasonality: 7, 8. spines; gastrozooid sessile, with one whorl of fili- Distribution: Mediterranean. form tentacles below conical hypostome, naked but References: Neppi and Stiasny (1913) ; Piraino et base of hydranths often with a perisarc cup-shaped al. (1996); Schuchert (2004). collar at base, sometimes of two sizes, smallest ones acting as dactylozooids; gonophores on hydrorhiza, Turritopsis nutricula McCrady, 1859 as free medusae, medusoids with four radial canals, (Figs. 32A-C, E) or as fixed sporosacs. Medusa: umbrella bell-shaped; manubrium bul- Colonies stolonal or erected and then irregularly bous; mouth simple, circular, with 4 or more branched and increasing in diameter from base to distal unbranched oral arms, either on or very near mouth end, hydrocaulus monosiphonic in small colonies, polysi- rim; 4 radial canals and circular canal; 4 or 8 mar- phonic in larger; branches adnate and parallel to hydro- ginal solid tentacles; “gonads” interradial or encir- caulus or to other branches for some distance, before cling manubrium; no ocelli. curving away at an acute angle and becoming free; References: Calder (1988); Schuchert (1996); hydrocaulus and hydrocladia recovered by a firm peris- Bouillon (1995a; 1999); Bouillon and Barnett (1999); arc, consisting of two layers, mostly infested with detritus Bavestrello et al. (2000); Bouillon and Boero (2000). and algae, without annulations and terminating below hydranth base; hydranths terminal, naked, elongated, Key to hydroids (Known only in the genus Cytaeis, fusiform, with 12-38 filiform tentacles scattered over dis- with family characters). tal three quarters of hydranth, proximal ones shorter than distal; hypostome elongated conical; medusae buds aris- Key for medusae ing mostly one by one from short stems below hydranths, 1. 4 marginal tentacles...... Cytaeis pear shaped, enclosed in perisarc. – 8 marginal tentacles...... Paracytaeis Medusa: umbrella 4-11 mm high, bell-shaped to perform, higher than wide, mesoglea thicker at apex; Genus Cytaeis Eschscholtz, 1829 manubrium large, cross-shaped in transverse section, = Perarella Stechow, 1922; Stylactella red in colour; 4 radial canals which continue through Haeckel, 1889 in part:

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Hydroid: see family characters. iform tentacles in one whorl, and an other very exten- Medusa: with family characters, 4 radial canals. sile filiform with only 4 short tentacles both with a Remark: Rees (1956b, 1962) re-established the wide collar of perisarc surrounding the base. Genus Perarella for species with fixed sporosacs or Gonophore arising directly from the stolon, giving rise degenerated medusae. Since generic classification based to medusoids almost spherical, with 4 radial canals, exclusively on medusa reduction is presently rejected, circular canal, 4 tentacular bulbs and a non functional Perarella is considered as congeneric with Cytaeis. manubrium. Female eumedusoids free swimming for References: Calder (1988); Bouillon et al. (1991); about 5 days before spawning and afterwards degen- Bavestrello (1987); Bavestrello et al. (2000). erating, male present no swimming activity. Cnido- cysts: desmonemes (6.3 x 3.6 mm) and microbasic 1. Colonies giving rise to free medusae ...... euryteles (8.1 x 3.1 mm).The two kinds of gastro- ...... Cytaeis spp zooids of Cytaeis schneideri are related to two differ- – Colonies giving rise to gonophores...... 2 ent trophic strategies the large gastrozooids feed on 2. Gonophores with radial canals, circular canals meiobenthic organisms consisting in nematodes and and tentacular bulbs; wide collar of perisarc polychaetes or bryozoan larvae, the filiform gastro- surrounding the base of the hydranth...... zooids engulfs and feeds on the distal portion of a sin- ...... C. schneideri gle lophophoral tentacles of its bryozoan host. When – Gonophores without radial canals, circular canals the lophophore retract the gastrozooid is dragged into and marginal bulbs. hydranth naked ...... the bryozoan for a short time, the hydrozoan never ...... C. propagulata catch portion of the lophoporal tentacle like Haloco- ryne epoizoica but merely suck the tentacle feeding on Cytaeis propagulata (Bavestrello, 1987) the food caught by the bryozoan lophophore. (Figs. 32F-H) (Bavestrello et al. 2000). Distribution: Mediterranean endemic. Stolonal colonies living on Hinia incrassata References: Motz-Kossowska (1905) as Perigo- shells; hydrorhiza following the grooves of the shell, nimus schneideri; Gili (1986); Boero and Bouillon sometimes originating tubes of naked coenosarc (1993); Medel and López-González (1996) (all as (propagules) with base surrounded by a collar of Perarella schneideri). perisarc. Hydranth nude, without perisarcal collar, hypostome conical, 7-15 filiform tentacles in one Cytaeis spp. (Fig. 33A) whorl; spines and dactylozooids absent. Male and female gonophores similar, ovoid, young ones hav- Hydroid: see family characters ing spadix occupying about two-thirds of their Medusa: umbrella up to 5 mm wide, 6 mm high, lenghts, mature ones with spadix which narrows and pear-shaped to globular, apical mesoglea about twice disappears when gametes have been liberated; as thick than lateral walls; with or without a slight female gonophores with 15-25 eggs, without radial peduncle; manubrium large, pear-shaped; mouth with canals, circular canal, neither marginal bulbs. up to 32 simple, more or less capitate and adnate oral Cnidocysts: microbasic euryteles (6x3 mm) and tentacles; with 4 broad radial canals; «gonads» inter- desmonemes (4.5x3 mm). radial generally encircling the manubrium; marginal Records from Mediterranean: western Mediter- tentacles bulbs large, pyriform to triangular attached to ranean. exumbrella; medusae buds on base of manubrium. Distribution: endemic of Mediterranean Sea. Three nominal Cytaeis medusae species have been References: Bavestrello (1987); Boero and described from Mediterranean waters, Cytaeis pusilla Bouillon (1993) (all as Perarella propagulata). Gegenbaur, 1857 (considered by Kramp (1961) as a doubtful species), Cytaeis tetraststyla Eschscholtz, Cytaeis schneideri (Motz-Kossowska, 1905) 1829 and Cytaeis vulgaris Agassiz and Mayer, 1899 (Fig. 32I) (considered once as a synonym of Cytaeis tetrastyla, once as a valid species, see Kramp (1959a), 1961, Stolonal colonies strictly associated with colonies 1968). In fact, the variations existing between speci- of the bryozoan Schizoporella longirostris, hydrorhiza mens of Cytaeis medusae from a single collection are reticulated with tubes of transparent perisarc. Polyps overlapping the characters described for the different nude, of two types, one long and tubular with 8-14 fil- species, no certain characters are presently known by

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which Cytaeis species medusae can be distinguished solid marginal tentacles with a terminal swelling; morphologically and the connotation Cytaeis spp. will marginal bulbs small; without ocelli. be used here. Hydroid: unknown. Records from Mediterranean: eastern and west- ern Mediterranean; Adriatic Sea. Genus Eucodonium Hartlaub, 1907 Known seasonality: 1-7; 10. Distribution: Atlantic, Indo-Pacific, Mediter- With the characteristics of the family. ranean. References: Babnik (1948); Kramp (1961); Rees Eucodonium brownei Hartlaub, 1907 (1962); Goy (1973b); Brinckmann-Voss (1987); (Fig. 33C) Calder (1988); Bouillon, Boero and Seghers (1991); Goy et al. (1988, 1990, 1991); Boero and Bouillon Medusa: umbrella up to 1 mm high and wide; (1993); Avian et al. (1995); Benovic and Lucic (1996). mouth lips containing each a group of about 100 cnidocysts; marginal bulbs with blackish pigment Genus Paracytaeis Bouillon, 1978 granules; cnidocysts along the entire tentacle sur- face and in terminal swellings; medusae buds arising Medusa: with general characters of the family, from middle region of manubrium. with eight marginal tentacles; with 4 interradial Records from Mediterranean: western Mediter- exumbrellar opaque oval spots of special vacuolated ranean; Adriatic. cells located midway of umbrella. Known seasonality: 1; 5-11. Hydroid: not known. Distribution: Atlantic, Indo-Pacific, Mediterranean. References: Picard (1955b); Kramp (1961); Paracytaeis octona Bouillon, 1978 Berhaut (1970); Brinckmann-Voss (1970, 1987); (Fig. 33B) Goy (1970, 1972); Schmidt and Benovic (1979); Castelló i Tortella (1986); Avian et al. (1995); Ben- Umbrella up to 2.5 mm wide, 3 mm high, bell- ovic and Lucic (1996); Schuchert (1996). shaped; with 4 interradial exumbrellar opaque oval spots of special vacuolated cells located midway of Family EUDENDRIIDAE L. Agassiz, 1862 umbrella; velum narrow; manubrium conical, half as long as umbrellar height; mouth circular, with up to Paedomorphic hydrozoa reduced to hydroid stage, 20 oral adnate capitate tentacles; «gonads» interra- colonies with erect, usually branched stem arising dial, covering almost all manubrium surface; 8 mar- from a creeping hydrorhiza; hydrocaulus enclosed by ginal tentacles; with large marginal tentacular bulbs firm perisarc either up to the base of the hydranth with adaxial and abaxial knob of cnidocysts; with body, where the ectoderm makes a groove, or some- medusa buds on interradial parts of manubrium. times enveloping lower half of hydranth in a cupuli- Records from Mediterranean: eastern Mediterranean. form process (E. vaginatum); hydranths large, urn- Known seasonality: 4; 5; 8-12. shaped with pedunculate hypostome and one or more Distribution: Indo-Pacific; Mediterranean. whorls of solid filiform tentacles immediately below References: Kramp (1961); Bouillon (1978a, it, sometimes presence of special cnidocyst-bearing 1980); Bouillon et al. (1988a); Lakkis and Zeidane processes erroneously called cnidophores; some (1985); Goy et al. (1988, 1990, 1991); Boero and species with a nettle ring immediately above the Bouillon (1993). groove; endoderm of the oral part of the hypostome thin and not differentiated. Reproduction by fixed Family EUCODONIIDAE Schuchert, 1996 sporosacs borne on the hydranth body below the ten- tacles, male and female normally on separate colonies; Medusa: Anthomedusae with a bell-shaped reproductive hydranth often reduced to blastostyle, umbrella, without pointed apical projection; exum- male gonophores usually with several chambers in lin- brella without cnidocysts tracks; manubrium quad- ear series, female gonophores initially with curved rangular; with a developed, conical, gastric pedun- spadix, each spadix with a single egg. cle; mouth quadrangular; with 4 inconspicuous lips Remark: The systematic position of the family armed with cnidocysts; with 4 radial canal and cir- Eudendriidae is unclear, although it is a very uni- cular canal; «gonads» encircling manubrium; with 4 form taxon, its phylogenetic affinities are not easy to

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establish and new criteria seem necessary to eluci- warts around hydranth body...... E. glomeratum date this problem. 10.Female blastostyle hermaphroditic.... E. simplex References: Calder (1988); Bouillon (1995a); – Female blastostyle not hermaphoditic...... Schuchert (1996); Marques (1996); Marques et al...... E. fragile (2000), Schuchert (2001a). 11.Complementary cnidocysts atrichous isorhizas ...... 12 1. Tentacles usually fewer than 35, in one whorl – Complementary cnidocysts heterotrichous ...... Eudendrium anisorhizas, female immature spadix bifurcated. – Tentacles 40 or more, in two or more whorls ...... E. carneum ...... Myrionema 12.Female immature spadix bifurcated, some hydranths with cnidophores ...... E. racemosum Genus Eudendrium Ehrenberg, 1834 – Female immature spadix unbranched, no cnidophores...... E. elseaoswaldae Eudendriidae with short urn-shaped hydranths and a single whorl of tentacles of varied number but Eudendrium arbusculum Wright, 1859 usually fewer than 35. (Figs. 33D-G) Remark: cnidome features are essential for species identification: Colonies up to 4 to 5 cm high, branching irregu- References: Calder (1988); Marinopoulos (1992), larly, hydrocaulus and main branches polysiphonic Marques (1996); Marques, Peña Cantero and Vervoort thining out to monosiphonic, branches either annulat- (2000), Marques, Mergner, Höinghaus, Santos and ed throughout or with some smooth portions; perisarc Vervoort (2000); Watson (1985; 2000). thick; most hydranths of a colony usually with a large band of cindocysts just above the basal annular Key to the species: after Marques et al. 2000 groove, tentacles about 20-22 in number; male gonophores on reduced blastostyles, usually two 1. Zooxanthellae present ...... E. moulouyensis chambered, distal end with a conspicuous pad of large – Zooxanthellae absent...... 2 microbasic euryteles cnidocysts; female gonophores 2. Only microbasic euryteles present ...... 3 oval, borne on partially reduced blastostyle becoming – Two different types of cnidocyst present ...... 8 completely at atrophied at maturity, blatotstyle 3. Microbasic euryteles of one size-class...... 4 becoming linked to the eggs by small peduncle, – Microbasic euryteles of two size-class...... 5 spadix unbranched, curving over the ovum. Cnido- 4. Unfascicled colonies without cnidophores...... cysts: small and large microbasic euryteles? ...... E. capillare Records from Mediterranean: Doubtful records – Fascicled colonies with cnidophores...... from eastern and western Mediterranean (see Mar- ...... E. armatum ques et al., 2000) 5. Female spadix ax-shaped ...... E. calceolatum Seasonality: ? – Female spadix rounded, non ax-shaped ...... 6 Distribution: North Atlantic, Mediterranean? 6. Female and male gonophores unreduced ...... 7 References: Calder (1972); Marinopoulos – Female and male gonophores reduced, narrow (1992); Marques et al. (2000); Schuchert (2001a). connection between chambers of male sporosac ...... E. merulum Eudendrium armatum Tichomiroff, 1887 7. Unfascicled colonies, or at most stem with a (Fig. 33H) complementary tube...... E. ramosum – Fascicled colonies...... E. rameum Colonies up to 65 mm high, composed of polysi- 8. Complementary cnidocysts macrobasic euryteles phonic and branched hydrocauli; perisarc of the ...... 9 stem brown to yellowish (in younger parts), with – Complementary cnidocysts atrichous isorhizas or several groups of annuli elsewhere; branches more heterotrichous anisorhizas ...... 11 or less alternate, but not in the same plane. Hydro- 9. Male blastostyle unreduced, macrobasic cladia ringed basally, also with several annulations euryteles never arranged in warts...... 10 at the base of renovated portions. Polyp on pedicels, – Male and female blastostyles reduced, with 29-32 filiform tentacles and flared hypostome. macrobasic euryteles arranged in aggregations or Nematophore naked, large and thin, borne on pedi-

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cel, irregularly distributed throughout the colony. partially atrophied tentacles; spadix unbranched, curv- Female gonophore with a normal spadix, male ing over egg; the male with up to three chambers each, gonophore with 2-3 chambers. Cnidocysts: het- terminal one with an apical tubercle, borne on atrophied erotrichous microbasic euryteles (5x3 to 6x4 µm) on polyps. Cnidocysts: only heterotrichous microbasic tentacles and ectoderm, also the same type (8x4 to euryteles (6.7-7.6 x 2.5-3.2 µm). 9x4.5 µm) on the hypostome, the hydranth and on Remark: See Marques et al. (2000) concerning the hydrocaulus; butt thin. the validity of the records of this species in the Records from Mediterranean: eastern and west- Mediterranean Sea. ern Mediterranean. Records from Mediterranean: eastern and west- Known seasonality: 1,7. ern Mediterranean, Adriatic. Reproduction: 7. Known seasonality: present throughout all the year. Distribution: endemic of Mediterranean Sea. Reproduction: 1-12. References: Gili (1986); Boero and Fresi (1986); Distribution: eastern and western Atlantic, Indian Marinopoulus (1992); Boero and Bouillon (1993); Medel Ocean, eastern and western Pacific; Mediterranean. and López-González (1996); Marques et al. (2000). References: Mammen (1963); Millard (1975); Millard and Bouillon (1974); Calder (1988); Cor- Eudendrium calceolatum Motz-Kossowska, 1905 nelius and Ryland (1990); Marinopoulus (1992); (Fig. 34A) Boero and Bouillon (1993); Avian et al. (1995); Medel and López-González (1996) Marques et al. Colonies composed of monosiphonic and (2000); Schuchert (2001a); Peña Cantero and García branched hydrocauli; axis and branches ringed Carrascosa (2002). basally. Hydranth urn-shaped. Mature female gono- phore with the spadix axe-shaped; male gonophore Eudendrium carneum Clarke, 1882 with 1-2 chambers. Cnidocysts: heterotrichous (= E. cunninghami) (Figs. 34E-I) microbasic euryteles (20x8 to 30x13 µm) on hypos- tome, hydranth and stem; butt thick, with two bulks, Colonies densely branched, bushy, up to 105 mm occupying 2/3 the length of capsule; small heterotri- high, composed of erect and polysiphonic hydrocauli, chous microbasic euryteles (6x2.5 to 9x4 µm) on more or less alternately branched, major branches tentacles, ectoderm and elsewhere. polysiphonic, secondary ones polysiphonic basally; Records from Mediterranean: western Mediter- perisarc thick, brownish in older parts, thinner and ranean. paler towards distally; branches and pedicels annulat- Known seasonality: 6 ed basally, also occasional annulations elsewhere. Distribution: endemic of Mediterranean Sea. Hydranth with a large flared hypostome and a shallow References: Motz-Kossowska (1905); Marino- perisarc groove basally; filiform tentacles (27-32) in poulus (1992); Boero and Bouillon (1993); Marques one whorl. Gonophores fixed sporosacs, borne on et al. (2000). hydranth; females on reduced hydranths with partially atrophied tentacles, spadix bifid and acuminate, curv- Eudendrium capillare Alder, 1856 ing over egg; during development, spadices shed, (Fig. 34B-D) embryos borne in perisarc-covered capsules arranged irregularly along annulated pedicel, terminal polyp Colonies small and slender, up to 17 mm high, com- eventually lost; male gonophores on atrophied polyps posed of erect and monosiphonic hydrocauli irregular- each with up to five chamber. Cnidocysts: heterotric- ly to more or less alternately branched; hydrocladia in hous anisorhizas (22.2-23.4x10.1-10.8 µm), on turn alternately to irregularly branched; pedicels long hydranth, hypostome and on the stem; butt visible in and bent; perisarc thicker basally and becoming thinner undischarged cnidocysts; heterotrichous microbasic towards distally, yellowish to transparent, terminating euryteles (9x4 µm) on tentacles and ectoderm. at groove around base of hydranths; stem branches and Records from Mediterranean: Adriatic western pedicels with several annulations basally, but also with Mediterranean. irregularly placed annulations elsewhere. Hydranth Known seasonality and reproduction: 7-12. with a large and flared hypostome, 15-20 filiform ten- Distribution: western and eastern Atlantic, Indi- tacles in one whorl. Gonophores fixed sporosacs, borne an Ocean, Mediterranean, Red Sea; western Pacific. on hydranths, the female in a whorl on hydranths with References: Vervoort (1968); Millard (1975); Gili

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(1986); Calder (1988); Marinopoulus (1992); Medel and whorl. Female mature gonophore with unbranched López-González (1996); Marques et al. (2000). spadix; male gonophore provided with one or two chambers; mature balstostyle with either a normal Eudendrium elsaeoswaldae Stechow, 1921 number of tentacles or a reduced number partly-atro- (Figs. 34J-K) phied tentacles. Cnidocysts: holotrichous macrobasic euryteles (24x10 to 28x11 µm), but long (4 times Colonies large and unfascicled, with long stems length of capsule) and spirally coiled around the big branches and pedicels; hydranth elongated; cnido- axis of the cnidocyst; these cnidocysts are concentrat- cysts small microbsaic euryteles and atrichous ed in several groups characteristically conspicuous at isorhiza (13.9- 17.1 x 6.3-7-3 µm). Only immature the basal half of the polyp; also heterotrichous blastostyles of both sexes observed, male reducing microbasic euryteles (6x2.5 to 9x4 µm) on tentacles tentacles in course of development, females with and ectoderm. normal number of tentacles and unbranched spadix. Records from Mediterranean: Adriatic western Remark: This species is usually not in the and eastern Mediterranean. Mediterranean checklist because it’s short descrip- Known seasonality: 10-4; reproduction: 9-3. tion. (Marques et al. 2000). Distribution: north-eastern Atlantic, Indo-Pacific, Records from Mediterranean: western Mediter- Mediterranean (distribution probably wider; it resem- ranean (Naples). bles the species E. ramosum, and many records of the Seasonality: ?. last species could possibly refer to E. glomeratum. Distribution: endemic of Mediterranean Sea. References: Motz-Kossowska (1905) as E. ramo- References: Stechow (1923d); Riedl (1959); sum; Picard (1951c); Watson (1985); Boero and Marques et al. (2000). Fresi (1986); Roca (1986); Boero and Cornelius (1987); Bavestrello and Cerrano (1992); Boero and Eudendrium fragile Motz-Kossowska, 1905 Bouillon (1993); Altuna (1994); Medel and López- (Fig. 34L) González (1996); Marques et al. (2000); Peña Can- tero and García Carrascosa (2002). Colonies small and delicate, hydrocauli monosi- phonic unbranched or little branched; with some Eudendrium merulum Watson, 1985 annuli at base of branches and hydranths. Polyp (Figs. 35A-G) small, almost uncolored, hypostome flared, without perisarc groove basally. Female gonophores with Hydrorhiza tubular, giving rise to simple or unbranched spadix when mature; male gonophores branched erect stems up to 20mm in heigth, unfascicled, with 1-2 chambers. Cnidocysts: heterotrichous lower stems roughly annulated up to the lowest branch. microbasic euryteles and macrobasic euryteles Hydranth small, with approximately 24 tentacles, a (27.5-29.0 x 10.0-11.0 µm). club-shaped hypostome and a distinct groove round the Records from Mediterranean: eastern and west- base below a ring of a few large cnidocysts. Colonies ern Mediterranean. dioecious; male gonophores borne on lower stems in Known seasonality: 9-5. dense cluster up to 20 per blastostyle, blastostyles com- Reproduction: 10-3. pletely reduced with distinct neck connecting Distribution: endemic of Mediterranean Sea. gonophore chambers; female gonophores borne thickly References: Motz-Kossowska (1905); Boero and on lower parts of colonies, globular, fully reduced, up to Fresi (1986); Marinopoulus (1992); Boero and 6 scattered on blastostyles, spadix unbranched during Bouillon (1993); Marques et al. (2000). early ontogeny, shed when mature; eggs with thin pelli- cle, placed along axis of blastostyle. Cnidome: microba- Eudendrium glomeratum (Picard, 1951) sic euryteles of two sizes: small ones 7-9 x 3.0 µm abun- (Figs. 34M-O) dant on tentacles; large ones 16.5-25.0 x 8.0-13.3 µm, having a much ornamented shaft and present in the Colonies up to 30 cm high, composed of hydro- cnidocyst ring and on spadix of female gonophores. cauli polysiphonic and branched; perisarc brown and Records from Mediterranean: Adriatic, eastern thick in older parts, becoming thin and yellowish to and western Mediterranean. transparent in younger regions. Polyp urn-shaped, Known seasonality: present throughout the all year. hypostome flared, tentacles filiform, 24-28 in one Reproduction. 1, 6-8.

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Distribution: Circumtropical. Records from Mediterranean: Adriatic, western References: Watson, (1985); Bavestrello and and eastern Mediterranean. Piraino (1991); Boero and Bouillon (1993); Avian et Known seasonality: 5-12. al. (1995); Marques et al. (2000); Peña Cantero and Reproduction: 6-10. García Carrascosa (2002). Distribution: widely distribution in the Indo- Pacific (Boero and Bouillon (1993), also present in Eudendrium moulouyensis the temperate and subtropical eastern Atlantic; cos- Marques, Peña Cantero and Vervoort, 2000 mopolitan species (Marinopoulus, 1992). (Figs. 35H-M) References: Watson (1985); Boero and Fresi (1986); Marinopoulus (1992); Boero and Bouillon Colonies minute, stem fragile up to 15 mm high, (1993); Avian et al. (1995); Medel and López- main stem unfascicled. Hydrocaulus arising from González (1996); Marques et al. (2000); Peña Can- stolonal hydrorhiza, irregularly branched in radiate tero and García Carrascosa (2002). plane up to second order over its whole extension in a few specimens, pedicels arising directly from main Eudendrium rameum (Pallas, 1766) stem. Perisarc of main stem weakly developed brown (Figs. 36E-G) up to half its length, single tubes not annulated. Hydranth slender, without distinctive groove in the Colonies large (up to 25 cm), bushy, with a aboral region; tentacles 25-28 in one whorl. Zooxan- fibrous basal mass, composed of erect, polysiphonic thellae present in hydranth and coenosarc. Only female and branched hydrocauli; perisarc dark brown, gonophores described, styloid, mature blatostyles with- minor branched ringed basally, sinuous to straight. out tentacles and hypostome, spadix shed. Eggs circu- Hydranths on ringed pedicels, hypostome bulbous, lar encapsulate by a perisarc layer. Cnidocysts: small 20-24 filiform tentacles in one whorl. Gonophores (6.3-7.5 x 3.2-3.5 µm) and large (10.0-15.0 x 5.0-8.7 unreduced ovoid, yellow, short-stalked, borne on µm) heterotrichous microbasic euryteles. and below hydranths, male with one chamber, Records from Mediterranean: western Mediterranean. female with a spadix. Cnidocysts: heterotrichous Known seasonality: 7, 8. microbasic euryteles (23x8 to 25x8 µm) on hypos- Distribution: endemic of Mediterranean Sea. tome, hydranth and on the hydrocaulus; butt thin, References: Marques et al. (2000); Peña Cantero straight, occupying totally the capsule; small het- and García Carrascosa (2002). erotrichous microbasic euryteles (8x4 µm) on tenta- cles and ectoderm. Eudendrium racemosum (Cavolini, 1785) Records from Mediterranean: Adriatic, eastern (Figs. 36A-D) and western Mediterranean. Known seasonality: almost always present.. Colonies up to 160 mm high, composed of basally Reproduction: 6-9. polysiphonic and branched hydrocauli; perisarc brown Distribution: cosmopolitan. in older parts to yellowish in younger ones. Hydrocla- References: Naumov (1960); Gili (1986); Cor- dia roughly alternate, not in the same plane. Hydranth nelius and Ryland (1990); Boero and Bouillon (1993); on pedicel ringed basally; stem ringed on origins of Avian et al. (1995); Medel and López-González hydrocladia and at other irregular intervals. Hydranth (1996); Marques et al. (2000); Schuchert (2001a); reddish, hypostome flared, tentacles filiform, 25-30 in Peña Cantero and García Carrascosa (2002). one whorl. It is characteristic the presence of a digiti- form and naked nematophore on the body of some Eudendrium ramosum (Linneaus, 1758) hydranths. Gonophores on polyps with atrophied ten- (Figs. 36H-L) tacles to a varying degree (those bearing mature gonophores totally atrophied), female gonophore with Colonies up to 175 mm; hydrocauli polysiphonic a bifid spadix not acuminate; male gonophore with 3 basally, sometimes slender and flexuous with rough- chambers. Cnidocysts: atrichous isorhiza (10.5x4 to ly alternate hydrocladia, sometimes stiff and bushy 11x 4 µm) on hypostome, hydranth and on the hydro- with irregular branching; branches monosiphonic. cauli; but invisible in undischarged cnidocysts; small Perisarc smooth, with groups of several annuli heterotrichous microbasic euryteles (6x4 to 7x5 µm) above origins of branches, and also elsewhere. on tentacles and ectoderm. Hydranth on pedicel ringed basally, hypostome

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flared, tentacles filiform, and 14-29 in one whorl. References: Motz-Kossowska (1905); Millard Gonophores borne on hydranths with atrophied ten- and Bouillon (1974); Millard (1975); Boero and tacles to a varying degree, female with an Bouillon (1993); Medel and López-González (1996) unbranched spadix, male with 1-2 chambers. Cnido- all as E. motzkossowskae; Marques et al. (2000); cysts: large heterotrichous microbasic euryteles Peña Cantero and García Carrascosa (2002). (22.2-28.0x8.7-13.3 µm) on hypostome, the lower part of hydranth, and on the stem; butt thin, about Eudendrium tenellum Allman , 1877 2/3 to 3/4 length of capsule, increasing in diameter distally but not coiled when undischarged; small Recorded from Adriatic by Broch (1912), doubt- heterotrichous microbasic euryteles on tentacles and ful species. ectoderm (5.8x2.7 to 8.4x4.2 µm). Records from Mediterranean: Adriatic, eastern Genus Myrionema Pictet, 1893 and western Mediterranean. Known seasonality: 1-12. Eudendriidae with calyx of hydranth elongate, often Reproduction: 7-2. columnar below tentacles; tentacles in two or more close Distribution: cosmopolitan. whorls, number varied but usually 40 or more. References: Millard and Bouillon (1973, 1974); References: Calder (1988); Marques et al., 2000. Millard (1975); Boero and Fresi (1986); Gili et al. (1989); Marinopoulus (1992); Boero and Bouillon Myrionema amboinense Pictet, 1893 (1993); Avian et al. (1995); Medel and López- (Figs. 36Q-R) González (1996); Marques et al. (2000); Schuchert (2001a); Peña Cantero and García Carrascosa (2002). Colonies up to 56 mm high, growing in groups, hydrocauli monosiphonic, sparingly and irregularly Eudendrium simplex Pieper, 1884 branched; perisarc thin and flexible, straw-colored to = E. motzkossowskae Picard, 1951 (Figs. 36M-P) transparent, with annulations at bases of branches. Hydranth urn-shaped, with a long and cylindrical Colonies small, up to 12 mm high, composed of calyx, with a shallow perisarc groove basally; hypos- monosiphonic and unbranched or sparsely branched tome large, flared to knobbed; tentacles filiform, about hydrocauli. Stem annulated on origins of branches and 35-60 in two or more close whorls; hydranth and ten- at other irregular intervals. Hydranth on pedicel annu- tacles bearing large numbers of zooxanthellae. lated or corrugated throughout, tentacles filiform, 16-27 Gonophores fixed sporosarcs, borne on hydranth in one whorl. Gonophores on hydranths which con- body; female with unbranched spadix; male with 1-4 serve the tentacles, male and female on separate chambers. Cnidocysts: microbasic euryteles heterotri- colonies; female gonophore with curved and chous (8.5-9.4 µm x 3.5-3.8 µm) on tentacles, unbranched spadix, hermaphroditic, containing one egg hydranth and elsewhere, butt thin, about 2/3-3/4 and one or more masses of spermatogenic cells at sum- length of capsule; macrobasic euryteles on hydranth mit between spadix and superficial ectoderm; male base and hypostome (21.8-23.4 µm x 9.7-11.3 µm). gonophore unreduced, 1-2 chambered. Cnidocysts: Remarks: Marinopoulus (1992) includes this holotrichous macrobasic euryteles (17x7.5 to 23.5x10.5 species in the genus Eudendrium. µm) arranged in two whorls, one at the hypostome and Records from Mediterranenan: eastern Mediter- the other one at the basal half of the hydranth; butt long ranean. (8-10 times length of capsule) spirally coiled around the Distribution: eastern and western Atlantic, Indi- big axis, swollen distally to about double the width an Ocean and Pacific Ocean; Mediterranean. when discharged, armed with spirally arranged barbs; References: Millard and Bouillon (1973); Calder small heterotrichous microbasic euryteles (6.6x2.5 to (1988); Marinopoulus (1992) as Eudendrium 7.2x3 µm) on tentacles and ectoderm. amboinense; Boero and Bouillon (1993); Marques Records from Mediterranean: eastern and west- et al. (2000). ern Mediterranean. Known seasonality: 4-11. Family HYDRACTINIIDAE L. Agassiz, 1862 Reproduction: 7-9, 11 Distribution: South Africa? Probably endemic to Hydroid: colony stolonal, polymorphic, usually Mediterranean (see Marques et al., 2000). epizootic; hydrorhiza either as a reticulum formed by

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perisarc-covered stolonal tubes (sometimes with pro- Medusa: Hydractiniidae with 4 or more solid, tective tubes: Clavactinia protecta), or as an encrust- simple marginal tentacles, not in groups; usually 4 ing mat issued from the coalescence of the stolonal or 8 simple or slightly branched mouth arms (which system and either covered by a common layer of are dilatations of the perradial corners of the mouth perisarc or with naked coenosarc; in some genera the rim see Fig. L Fig. 10.) armed with clusters of cnido- hydrorhizal mat is invested by a calcareous skeleton; cysts; with or without gastric peduncle; «gonads» on frequently with chitinous or calcareous spines form- manubrium, interradial, but sometimes extending ing sometimes pillars and branches; polyps sessile, along proximal parts of radial canals; with or with- naked; gastrozooids either with one whorl or with out ocelli; sometimes asexual reproduction by several closely alternating whorls of oral filiform ten- medusa budding on manubrium. tacles or with scattered tentacles on the distal half of the body, exceptionally with one or two tentacles; Key to hydroids dactylozooids, when present, with no tentacles; ecto- dermal vesicles of unknown function present or not in Due to their great morphological uniformity, the hydrorhiza (Hydrocorella, Janaria); gonophores typ- hydroid stages of Hydractinia are not easy to distin- ically borne on gonozooids with one or more whorls guish when they are in reproduction. of oral tentacles or without tentacles and mouth ( = 1. Colonies giving rise to medusae or eumedusoids blastostyles), exceptionally on or in hydrorhiza (H...... 2 cryptogonia), gonophores giving rise to fixed – Colonies giving rise to fixed sporosacs ...... 8 sporosarcs, eumedusoids or free medusae. 2. Colonies giving rise to free medusae...... 3 Medusa: Anthomedusae more or less bell- – Colonies giving rise to eumedusoids ...... 5 shaped; with or without slight apical process; 3. Gastrozooids without basal perisarcal collar; manubrium tubular to sac-shaped not extending gonophores 1 or usually 2 per gonozooid on a beyond umbrella margin; with or without gastric short pedicel; sometimes spiral dactylozooids.... peduncle; mouth with 4 simple or branched oral lips ...... H. areolata elongated to form arms armed with terminal clusters – Gastrozooids with a basal perisarcal collar, of cnidocysts (exceptionally mouth rim simple and gonozooid with 1 to 15 or occasionally more armed with a cnidocysts ring: Kinetocodium, not gonophores in clusters...... 4 present in Mediterranean); 4, 8 or more solitary, 4. Hydranths 10- 15 mm...... H. borealis solid, marginal tentacles; with 4 radial canal and cir- – Hydranths up to 5.5 mm...... H. carnea cular canal; «gonads» on manubrium, interradial, 5. With encrusting hydrorhiza ...... H. aculeata sometimes extending along the proximal portions of – Without encrusting hydrorhiza...... 6 the radial canals; with or without ocelli. 6. Gastrozooid tentacles in one whorl ... H. pruvoti References: Bouillon (1995a); Bouillon et al. – Gastrozooid tentacles in several whorls...... 7 (1997) and Boero et al. (1998); Schuchert (2001a). 7. Gastrozooid with tentacles in more than 3 whorls; gonozooids with tentacles in two whorls, Genus Hydractinia van Beneden, 1841 no spines...... H. inermis (junior synonym = Podocoryna) 7 Gastrozooid with tentacles in 3 whorls, gonozooids with tentacles in one whorl; spines Hydroid: colonies with a stolonal reticular hydrorhiza present ...... H. calderi formed by tubes covered with perisarc, or with an 8. With a characteristic ring of large microbasic encrusting hydrorhiza covered with perisarc or with euryteles surrounding hypostome above a single naked coenosarc; frequently with simple, canaliculated whorl of 4 - 12 tentacles both in gastrozooids or branched spines. Hydranths sessile, naked, polymor- and gonozooids...... H. fucicola phic: gastrozooids, gonozooids, and occasionally dacty- – Without this characters, usually about 8 tentacles lozooids; gastrozooids with one or more close whorls of surrounding hypostome ...... H. echinata tentacles encircling the hypostome; dactylozooids with- out tentacles; gonophores as fixed sporosacs, released or Key to the species with medusae retained eumedusoids, or free medusae arising from varyingly developed gonozooids, with one or more close 1. Oral arms bifurcated once or twice; 24-32 whorls of tentacles or without tentacles and/or hypos- marginal tentacles...... H. borealis tome, being reduced to blastostyles; – Oral arms well developed, simple, undivided.. 2

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2. With medusa buds ...... 3 tion, sometimes as such a degree that the gonophores – Without medusa buds ...... 4 appears issued from the hydrorhiza. 3. With 4 marginal tentacles...... H. minima Medusa: umbrella 2-3.8 mm wide, bell shaped, – With 8 marginal tentacles...... H. minuta about as high than wide, no apical process; mesoglea 4. «Gonads» on manubrium only; rarely more than thin, thicker in apical region; velum broad; manubri- 8 tentacles...... H. carnea um cylindrical, about half as high than subumbrellar – «Gonads» on manubrium and on manubrial cavity, with a very slight gastric peduncle, with four pouches; with 8 large and numerous l small perradial manubrial pouches about one-third the marginal tentacles ...... H. areolata length of the radial canals; 4 radial canals and circular canal narrow; mouth elongated with four perradial lips Hydractinia aculeata (Wagner, 1833) each with one terminal cnidocyst cluster; «gonads» (Fig. 37A) interradial on manubrium wall and extending along manubrial pouches; up to 57 solid marginal tentacles Colonies with encrusting hydrorhiza living on dif- with swollen basal bulbs, the four perradial and four ferent gastropod shells; spines present. Gastrozooids interradial tentacles larger and approximately from the with 8-12 tentacles, hypostome conical. Gonozooids same size, remaining tentacles small and from differ- shorter than gastrozooids, with 3-4 tentacles. ent size; no ocelli; no medusa buds. Gonophores ovoid, borne in groups of 4-6, giving rise Records from Mediterranean: western Mediter- eumedusoids with 4 radial canals and circular canal. ranean; Adriatic. Records from Mediterranean: Adriatic, eastern Known seasonality: 10-5. and western Mediterranean. Distribution: Atlantic; Mediterranean. Distribution: endemic of Mediterranean Sea. References: Russell (1953); Kramp (1957b; References: Motz-Kossowska (1905); Herberts 1961); Yamada (1961); Berhaut (1970); Edwards (1964); Bavestrello (1985) Avian et al. (1995). (1972); Goy (1973b); Schmidt and Benovic (1979); Castello i Tortella (1986); Brinckmann-Voss (1987); Hydractinia areolata (Alder, 1862). Boero and Bouillon (1993) Avian et al. (1995). (= Podocoryna hartlaubi Neppi and Stiasny, 1911) (Figs. 37B-I) Hydractinia borealis (Mayer, 1900) (Fig. 37J-N) Colonies living on gastropod shells occupied by hermit crabs. Hydroid forming a closely meshed net- Hydroid: colonies found on a variety of hosts and work of perisarc-covered stolon tubes from which aris- showing some variability with site. Hydroid presenting es gastrozooids, gonozooids, spines, and sometimes a stolonal reticular hydrorhiza formed by separated spiral dactylozooids and tentaculozooids; the gastro- anastomosing perisarc-covered tubes, sometimes form- zooids are sessile, tubular to claviform, slightly taper- ing an encrusting sheet recovered by a common peris- ing towards base, with a rounded-conical hypostome, arc; generally with a few smooth, short, blunt spines, with a single whorl of 4-14 amphicoronate filiform ten- depending on host; hydranths sessile, naked, claviform tacles and without basal perisarcal collar; the gono- or cylindrical when extended, with a delicate cup-like zooids have the same shape than the gastrozooids but ring of perisarc around the base, hypostome conical to are smaller and slender and have only 7-8 filiform ten- rounded, large, with one whorl of 12-16 amphicoronate tacles, the spines are smooth, tall, slender, gently taper- filiform tentacles; a few scattered, slender tentaculo- ing and somewhat curved, they are closely grouped and zooids are often but not always presents, they have a separated by areas free of perisarcal armature; the spi- short perisarcal collar at base, their tip is rounded, not ral zooids have a swollen hollow base above which swollen; no spiral-zooids observed; gonozooids more they gradually tapers, becoming solid and terminating slender than gastrozooids, usually with less tentacles in a blunt tip armed with cnidocysts, they generally (up to 12), much variable in shape and size; medusa occurs near the rim of the colonies; the tentaculozooids buds with short peduncle, borne in clusters, up to 15 or are rare, not coiled and more slender than the spiral more, around a narrow zone of the upper part of the col- zooids; 1-2 (up to 5) medusa buds in the middle region umn, medusa buds at various stages of development, of the gonozooid, at different stages attached by a short gonozooids often reduced, at the extreme, without ten- peduncle and often in opposite position, during medusa tacles and hypostome, reduced to a short column bear- production gonozooids undergoes progressive reduc- ing one or two medusa buds at the apex (blatsostyle).

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Medusa: Umbrella up to 5 mm high and wide, Hydroid: colonies found mainly on shells of Nas- bell-shaped, mesoglea thin; manubrium long and sarius or on other gastropods occupied by various her- tubular, not extending beyond umbrellar margin, mit-crabs, more seldom on lamellibranches and crus- with no or on very short gastric peduncle; four long taceans and still more rarely on rocks. Hydroid pre- mouth-arms in latter stages bifurcated once or twice, senting a solonal, reticular hydrorhiza formed by peris- each branch with a terminal cnidocyst cluster; arc-covered tubes, in old colonies or in region of dense- «gonads» interradial, occupying greater part of the ly aggregated polyps, the hydrorhiza becomes encrust- manubrium, no medusa buds; 16-32 marginal tenta- ing and is recovered by a common perisarc or by a coa- cles; without ocelli. lescent layer of naked coenosarc; smooth, blunt, short Records from Mediterranean: the presence of spines often present arising from hydrorhiza, depend- this species in Mediterranean is uncertain. It is ing from the nature of the host; hydranths springing include in the Mediterranean fauna by (Tregouboff, directly from stolons, single, naked, claviform to cylin- 1957) and (Picard, 1958b) but with no records, Riedl drical, hypostome rounded, fairly large capable of (1959) consider that reports of this species from much change of form, with a single whorl of up to 19 Naples are uncertain; it has been also reported near amphicoronate filiform tentacles, sometimes, with a Malta (Evans, 1968) but Edwards (1972) found out short, delicate basal collar of perisarc; the fertile polyps it was Turritopsis nutricula. As stated by Edwards or gonozooids become smaller during medusa devel- (1972) further studies of Hydractinia medusa in the opment and the number of their tentacles decreases Mediterranean and Adriatic Sea are needed. eventually to on or two, gonozooids often reduced to Distribution: Atlantic; Mediterranean? blastostyles; spiral zooids or tentaculozooids rarely References: Rees (1941b); Edwards (1972); present , usually only in colonies living on shells asso- Boero and Bouillon (1993) as Podocoryne borealis; ciated with hermit-crabs and then concentrated at the Avian et al. (1995); Schuchert (2001a). rim of the shell aperture; medusa buds borne in a whorled cluster around the upper part of the hydranth Hydractinia calderi at some distance below tentacles,1-10 or more in num- Bouillon, Medel and Peña-Cantero 1997 ber, at different stages of development. (Figs. 38A-B) Medusa: umbrella up to 1- 2.11 mm high and 2.42 mm wide, bell-shaped; no apical process; mesoglea Hydrorhiza stolonal, reticular tubes covered with thin; scattered cnidocysts on exumbrella; velum broad; perisarc and adhering to gastropod shells. Gastro- manubrium cylindrical, no more than half the length of zooids cylindrical, elongated, up to 5 mm high, with subumbrellar cavity; no gastric peduncle; mouth with basal perisarcal cup. Hypostome with 20-40 filiform four single round perradial clusters of cnidocysts; 4 tentacles in 3 whorls. Gonozooids much shorter, radial canals and ring canal narrow; «gonads» interra- with basal perisarcal cup and 2-14 filiform tentacles dial; 4 perradial marginal tentacles, and one to two in one whorl. Each gonozooid generally bearing one interradial tentacles, making eight in all, often four per- or two eumedusoids, rarely three, one always well radial tentacles only (Hydractinia carnea exigua); no developed, the others juvenile. Eumedusoids with ocelli; no medusa buds on manubrium; often sexual four radial canals and an often reduced subumbrel- mature at or shortly after liberation. lar cavity with striated muscle, four large bulbs, and Records from Mediterranean: eastern and west- four smaller ones. Female eumedusoids with numer- ern Mediterranean; Adriatic; Black Sea. ous eggs. Dactylozooids and spines present. Known seasonality: 1-9. Cnidome: microbasic euryteles (8.7-11 x 3.2 µm) Reproduction :6-9. and desmonemes (6.3-7.5 x 3.2-3.6 µm). Distribution: Atlantic; Indo-Pacific; Mediter- Records from Mediterranean: western Mediter- ranean. ranean. References: Kramp (1961); Berhaut (1970); Seasonality: ? Edwards (1972); Goy (1973b); Gili (1986); Castelló Distribution: endemic of Mediterranean Sea. i Tortella (1986); Brinckmann-Voss (1987); Goy et References: Bouillon et al. (1997); Peña Cantero al. (1988, 1990; 1991); Boero and Bouillon (1993); and García Carrascosa (2002). Benovic and Lucic (1996); Avian et al. (1995); Medel and López-González (1996); Cerrano et al. Hydractinia carnea (M. Sars, 1846) (1998); Schuchert (2001a); Peña Cantero and García (Figs. 38C-F) Carrascosa (2002).

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Hydractinia echinata (Fleming, 1828) Distribution: north eastern Atlantic, Mediterranean. (Fig. 38G) References: Motz-Kossowska (1905); Castric- Fey (1970); Medel and López-González (1996); Encrusting hydrorhiza white to pale pink giving Bouillon, et al. (1997). rise different kinds of polyps, living on gastropod shells but also on other solid substrata. Gastrozooids Hydractinia hooperii (M.Sars,1846) slender, widening upwards, about 8 tentacles in on (Fig. 39B) whorl, hypostome conical. Gonozooids shorter than gastrozooids, with few tentacles and a ring of Colonies living mainly on gastropod shells or cir- gonophores. Dactylozooids long, slender. ripedes; stolonal polymorphic. With smooth, cone Hydrorhiza about 3 mm thick, with numerous blunt shaped spines.Gastrozooids long and thin, with 11-16 conical chitinous spines with jagged edges. tentacles set in one whorl around hypostome. Gono- Gonophores of both sexes generally on different zooids with only six to eight tentacles and four gonozooids; male gonophore yellow to white, gonophores, two well developed and two much small- ovoid; the female, pink and spherical. er. Cnidome microbasic euryteles (7.1-7.9 x2.4-3.2 Records from Mediterranean: western Mediter- µm) and desmonemes (5.5-6.3 x2.8-3-2 µm). ranean. Records from Mediterranean: western Mediter- Records outside the Mediterranean: north-east- ranean. ern Atlantic, Arctic Sea. Known seasonality and reproduction: 7-8 References: Vervoort (1946); Leloup (1952); Distribution: Atlantic, Mediterranen Naumov (1960); Gili (1986); Cornelius and Ryland References: Bouillon, et al. (1997); Peña Cantero (1990); Boero and Bouillon (1993); Medel and and García Carrascosa (2002). López-González (1996); Schuchert (2001a). Hydractinia inermis (Allman, 1872) Hydractinia exigua (Haeckel, 1880) (Fig. 39C) = Hydractinia carnea M. Sars, 1846 Colonies living on different substrates (algae, The exigua form with only four tentacles is com- sea-grasses, crustaceans, hydrozoans); spines on monly found in Mediterranean (Adriatic) but has hydrorhiza absent; dactylozooids sometimes pre- also a been found in Roscoff and Plymouth mixed sent. Gastrozooids (up to 4.2 mm high) with a basal with specimens with interradial tentacles. It is nev- perisarc cup and about 20 tentacles in two or sever- ertheless often regard as a well defined species al whorls, hypostome conical; gonozooids (up to 2 (Picard, 1958b, Cerrano et al.,1998) mm) with two whorls of about 12 tentacles and bear- ing fixed eumedusoids, having eight tentacular Hydractinia fucicola (M. Sars, 1857) bulbs, the females containing many eggs. Dactylo- (Fig. 39A) zooids sometimes present. Cnidocysts: desmo- nemes, haplonemes and microbasic euryteles. Encrusting hydrorhiza covered by naked Records from Mediterranean: Adriatic, eastern coenosarc, armed by numerous spines, living on dif- and western Mediterranean. ferent substrates (crustaceans, algae, hydrozoans); Known seasonality: 2,4,5 dactylozooids may be present. Gastrozooids pale Reproduction: 2,4,5. pink, length up to 3mm, hypostome cylindrical, 8-12 Distribution: endemic of the Mediterranean. tentacles. Gonozooids pink, hypostome trumpet- References: Boero (1981);Gili (1986) as Stylac- shaped, 4-8 tentacles; male and female gonophores tis; Medel and López-González (1996) as Stylac- in separated colonies; male gonophore spherical; the taria; Bouillon, et al. (1997); Peña Cantero and Gar- female slightly flattened on both extremes, with 7-8 cía Carrascosa (2002). eggs. Both gastrozooids and gonozooids with a characteristic ring of large microbasic euryteles Hydractinia minima (Trinci, 1903) cnidocysts surrounding the hypostome above the (Figs. 39D-E) single tentacle whorl (of 4-12 tentacles). Records from Mediterranean: western Mediter- Medusa: umbrella globular or dome-shaped, ranean. about as high as wide 0.3-1 mm; mesoglea thin, soft,

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a slight apical thickening; manubrium barrel- References: Babnik (1948); Kramp (1961); Goy shaped, length half of umbrella cavity, circular in (1973b); Benovic (1976); Schmidt and Benovic cross section; four perradial lips elongated to form (1979); Gili (1986); Benovic and Bender (1987); oral tentacles each terminating in a single spherical Goy et al. (1988, 1990, 1991); Boero and Bouillon cluster of cnidocysts; gastric peduncle short; velum (1993); Avian et al. (1995); Benovic and Lucic well developed; four interradial «gonads» surround- (1996); Medel and López-González (1996). ing manubrium when mature; asexual reproduction by budding from the manubrium wall, buds and Hydractinia pruvoti (Motz-Kossowska, 1905) «gonads» may be produced at the same time; four (Figs. 39H-I) distinct narrow radial canals, circular canal indis- tinct; four solid perradial tentacles each with a oval Encrusting hydrorhiza with numerous spines and marginal bulb; no ocelli. sometimes dactylozooids living on gastropod shells. Hydroid: unknown. Gastrozooids (up to 15 mm.) with 10-14 tentacles in Records from Mediterranean: eastern and west- one whorl, hypostome conical; gonozooids (up to 5 ern Mediterranean; Adriatic Sea. mm.) with only one tentacle at the top; with 8-9 Known seasonality: 1-12. gonophores of which one, much more developed; Distribution: Atlantic; Indo-Pacific; Mediter- eumedusoids with 4 marginal bulbs and several eggs. ranean. Records from Mediterranean: western Mediter- References: Vannucci (1957); Kramp (1961); ranean. Berhaut (1970); Goy (1973b); Benovic (1973); Distribution: endemic of Mediterranean Sea. Schmidt and Benovic (1979); Uchida and Sugiura References: Motz-kossowska (1905); Medel and (1977); Castello i Tortella (1986); Gili (1986); Benovic López-González (1996); Bouillon, et al. (1997); and Bender (1987); Brinckmann-Voss (1987); Goy et Bavestrello et al. ( 2000). al. (1988, 1990, 1991); Boero and Bouillon (1993); Avian et al. (1995); Benovic and Lucic (1996); Medel Family NIOBIIDAE Petersen, 1979 and López-González (1996); Goy (1997). Hydroid: unknown. Hydractinia minuta (Mayer, 1900) Medusa: 2 simple and 2 bifurcated radial canals, (Figs. 39F-G) so that six canals reach the circular canal; “gonads” on manubrium, interradial; marginal tentacular Medusa: umbrella 0.5-up to 2mm high, slightly bulbs developing into medusae; no ocelli, gastric higher than broad, oval to pear-shaped, with apical peduncle, and mesenteries. projection; mesoglea moderately thick; velum well References: Brinckmann, (1959); Bouillon developed; manubrium short, circular in cross-sec- (1995a; 1999); Bouillon and Boero (2000). tion, on a well developed gastric peduncle; mouth with four perradial lips elongated to form oral arms Genus Niobia Mayer, 1900 terminating with a knob of cnidocysts; medusa buds on interradial walls of manubrium; narrow radial With the characters of the family. canals and circular canal; 4 perradial and 4 interradi- al marginal tentacles each with a small oval bulb; no Niobia dendrotentaculata Mayer, 1900 ocelli; newly released medusa buds with 8 tentacles. (Fig. 40A) Hydroid: unknown. Remarks: this species is very similar to Hydrac- With the characters of the family. tinia minima and several authors have discussed the Records from Mediterranean: western Mediter- possible identity of the two species. Russell (1953); ranean. Vannucci (1957) and Kramp (1961) nevertheless Distribution: present in the three great oceans. maintain them distinct. References: Brinckmann (1959); Avian et al. (1995). Records from Mediterranean: eastern and west- ern Mediterranean; Adriatic Sea. Family PANDEIDAE Haeckel, 1879 Known seasonality: 2-11. Distribution: Atlantic; Indo-Pacific; Mediter- Hydroid: colonies usually stolonal, not branch- ranean. ing; hydranth tentacles filiform, normally in one

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whorl, exceptionally in two or more whorls, or scat- ...... Stomotoca tered, or absent; perisarc developed to a variable 5. Hydranth without pseudohydrothecae...... 7 degree, occasionally forming a pseudohydrotheca or – Hydranth with pseudohydrotheca ...... 6 missing completely; reproduction mainly by free 6. Pseudohydrotheca more or less gelatinous ...... medusae, except in some modified genera of ques- ...... Leuckartiara tionable affinity like Nudiclava = Hydrichthys. – Pseudohydrotheca not gelatinous...... Neoturris Medusa: umbrella bell-shaped, with or without 7. Hydrocaulus short, hydranth with a single row of apical projection; manubrium quadratic, usually large; 3-4 filiform tentacles ...... Octotiara with or without gastric peduncle; 4 oral lips, simple, or – Hydrocaulus well developed; hydranth with an crenulated, or complexly folded; 4 radial canals amphicoronate whorl of more than 8 filiform (exceptionally 8, as in Octotiara) often broadened, or tentacles...... Amphinema ribbon-like, or with jagged margin; rarely centripetal canals; with or without mesenteries; “gonads” either Key to medusae with smooth surface or complexly folded, on manubri- um walls in adradial or interradial position, sometimes Where only juvenile medusae known: see Pan- extending along radial canals, or completely perradial; deidae incertae sedis, or juveniles, or conspecific, 2 or more hollow marginal tentacles; bulbs mostly see below tapering, elongated, conical (almost carrot-shaped) and often laterally compressed; with or without rudi- 1. With only two well developed marginal tentacles mentary tentacles (tentaculae), or marginal warts; with in adults ...... 2 or without abaxial ocelli; cnidome usually containing – With more than two well developed marginal microbasic euryteles. tentacles in adults ...... 3 References: Wedler and Larson (1986); Calder 2. With horse shoe-shaped interradial gonad with (1988); Pagès, Gili and Bouillon (1992); Bouillon transversal bridge...... Codonorchis (1995a, 1999); Migotto (1996); Schuchert (1996); – With adradial or interradial «gonads» in rows or Brinckmann-Voss and Arai (1998); Bouillon and sac-like «gonads» extending from adradial side Barnett (1999); Bouillon and Boero (2000). of manubrium outwards along radial canals ...... Amphinema Key to hydroids 3. With eight simple radial canals ...... Octotiara – With 4 primary radial canals...... 4 The hydroids of many Pandeidae are unknown, 4. «Gonads» smooth or corrugated; 4 fairly simple or known only as juveniles. Where known, some lips; manubrium cruciform; «gonads», usually hydroids are so similar that it is almost impossible to adradial, smooth or exceptionally weakly try to make a key, conversaly as, like in the genus corrugated ...... Merga Merga, the colonies are so variable that they can be – «Gonads» reticulate or folded, or both; oral lips referred to any Pandeid genus. more or less folded or crenulated...... 5 5. «Gonads» reticulate, with isolated interradial 1. Hydroids parasite of fishes, or of copepods pits, with or without additional folds ...... 6 parasite of fishes, hydrorhiza forming a naked – «Gonads» reticulate, without isolated interradial encrusting Fig.; without tentacles ...... pits, horse-shoe-shaped, with diverging ...... Hydrichthys; Larsonia horizontal folds directed towards outside ...... – Hydrorhiza as creeping stolons ...... 2 ...... Leuckartiara 2. Hydranth sessile or almost sessile and naked .. 3 6. «Gonads» reticulate, in 8 vertical, adradial series – Hydranth on more or less developed hydrocaulus of transverse folds; interradial portion of covered with perisarc ...... 5 manubrium walls with isolated pits .... Neoturris 3. Hydranth with one whorl of 4-6 tentacles...... – «Gonads» reticulate, without surrounding folds ...... Codonorchis and with isolated interradial pits...... Pandea – Hydranth with more than one whorl of tentacles ...... 4 Genus Amphinema Haeckel, 1879 4. Hydranth with 2 closely set whorls of tentacles ...... Pandea Hydroid: when known, colony stolonal, with – Hydranth with 3 whorls of tentacles ...... creeping hydrorhiza; hydrocaulus well-devel-

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oped, unbranched with a terminal hydranth, cov- drothecae, the distal perisarc margin on hydranths ered by perisarc often infested by detritus and body difficult to observe; hydranths spindle-shaped extending to the base or the middle of the with a rounded-conical hypostome, with one whorl hydranths body but not developing in a real of 8-14 amphicoronate filiform tentacles; medusa pseudohydrotheca; hydranth elongate, with one buds borne singly on short peduncles arising from whorl of amphicoronate, filiform, oral tentacles; hydrorhiza. polyps bending over when stressed; medusa buds Medusa: Umbrella up to 4 mm wide and 6 mm on short peduncles arising from hydrorhiza, hry- high bell-shaped, with a large, conical, solid, apical drocaulus, or both. projection, mesoglea of uniform thickness besides Medusa: generally with a large apical projec- top; manubrium cross-like in section, flask-shaped, tion; sometimes with an apical chamber; typically almost as long as bell cavity; mouth cruciform with with 2 opposite hollow marginal tentacles; with 4 prominent, recurved lips; with 2 very long taper- marginal warts or tentaculae; without gastric ing opposed marginal tentacles with large elongated peduncle; manubrium with broad base; with or conical basal bulbs and 12-24 small marginal warts, without mesenteries; 4 simple oral lips; “gonads” without tentaculae; with 8 simple adradial smooth either adradial, interradial or perradial, occasion- «gonads»; without ocelli. ally extending along radial canals; with or without Records from Mediterranean: eastern and west- ocelli. ern Mediterranean; Adriatic Sea. References: Brinckmann-Voss and Arai (1998); Known seasonality: 2-11. Rees (2000). Distribution: Atlantic; Indo-Pacific; Mediter- ranean. Key to hydroids References: Rees and Russell (1937); Babnik (1948); Russell (1953); Kramp (1961); Goy 1. Distal perisarc margin on hydranths body (1973b); Schmidt and Benovic (1979); Gili (1986); difficult to observe ...... A. dinema Benovic and Bender (1987); Brinckmann-Voss – Distal perisarc margin on hydranths body well (1987); Goy et al. (1988, 1990, 1991); Ramil marked ...... A. rugosum (1988); Boero and Bouillon (1993); Avian et al. (1995); Benovic and Lucic (1996); Medel and Key to medusae López-González (1996); Schuchert (1996).

1. «Gonads» extending from adradial sides of Amphinema rubra (Kramp, 1957a) manubrium outwards along radial canals; with (Fig. 40D) ocelli ...... A. turrida – «Gonads» on manubrium only; no ocelli...... 2 Medusa: umbrella 4.5 mm wide, 7 mm high, with 2. Margin between tentacles with rudimentary fairly thick walls and fairly pointed apical projec- warts, without marginal tentaculae «gonads» tion; manubrium large, barrel-shaped; mesenteries simple, without folds...... A. dinema long, half length of manubrium; mouth square, with – Margin between tentacles with short solid 4 simple recurved lips; with broad apical chamber marginal tentaculae...... 3 above manubrium; «gonads» covering interradial 3. «Gonads» adradial, folded...... A. rugosa walls of manubrium, smooth; 2 opposed marginal – «Gonads» interradial, smooth...... A. rubra tentacles with elongate conical bulbs; with 5-6 inter- radial tenon-like marginal tentaculae; without mar- Amphinema dinema (Péron and Lesueur, 1810) ginal warts; manubrium, «gonads» and lips deep (Figs. 40B-C) reddish; without ocelli. Hydroid: unknown. Hydroid: colonies stolonal, with creeping Records from Mediterranean: western Mediter- hydrorhiza, giving rise to well developed ranean. unbranched hydrocauli with a terminal hydranth, Known seasonality: 1; 8; 10. hydrocauli longer than hydranths and covered by Distribution: Antarctic (Atlantic section); thin perisarc, with or without basal annulations, Mediterranean. often infested by detritus and extending to the base References: Kramp (1957a, 1961); Goy (1973b); of the hydranths but not developing in a pseudohy- Boero and Bouillon (1993); Gili et al. (1998)

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Amphinema rugosum (Mayer, 1900) ular bulbs, tentaculae or rudimentary bulbs all (Figs. 40E-F) with a red ocelli. Hydroid: unknown. Colonies stolonal, with creeping hydrorhiza, giv- Records from Mediterranean: western Mediter- ing rise to single or slightly branched hydrocauli ranean. with terminal hydranths; perisarc with two to five Known seasonality: 4; 5. annulations at hydrocauli base and extending to the Distribution: Atlantic; Indo-Pacific; Mediter- middle of the hydranth body where it adheres to ranean. polyp with a well marked end, perisarc often infest- References: Bigelow (1909); Kramp (1961); Goy ed with detritus; hydranths spindle shaped, with a (1973b); Bouillon (1980); Boero and Bouillon dome-shaped hypostome, with one whorl of 8-12 (1993). amphicoronate filiform oral tentacles; 1-3 medusa buds borne on short stems from hydrorhiza and from Genus Codonorchis Haeckel, 1879 hydrocauli. Medusa: umbrella up to 6 mm high, slightly Hydroid: colonies stolonal with simple creeping higher than wide, bell-shaped, with a large conical hydrorhiza; hydranths, small (0.25 mm) sessile, to hemispherical apical projection, mesoglea uni- naked, fusiforme; hypostome short, conical; with a formly thin besides top; with slight perradial fur- single whorl of 4-6 filiform tentacles; medusa buds rows in top umbrella; manubrium flask-shaped, on hydrorhiza with a pedicel of variable length, gen- cruciform in section, reaching almost umbrella erally longer than hydranth. margin; mouth cruciform, with 4 prominent, Medusa: pandeidae with an apical projection; slightly recurved lips; eight «gonads» in adradial never with more than 2 opposite hollow marginal pairs, with 3-4 characteristic folds directed inter- tentacles; with marginal tentaculae; without gastric radially; four broad radial canals with jagged and peduncle; manubrium with broad base; with mesen- smooth margins; two diametrically opposed mar- teries; mouth cruciform with 4 simple lips; ginal tentacles with large, hollow, conical, taper- «gonads» horse-shoe-shaped; with ocelli. ing and very long bulbs; with 14 - 24 small mar- Reference: Boero et al. (1997). ginal tentaculae; no ocelli. Records from Mediterranean: eastern and west- Codonorchis octaedrus Haeckel, 1879 ern Mediterranean. (Fig. 40H, 41A) Known seasonality: 7. Distribution: Atlantic; Indo-Pacific; Mediter- Hydroid: colonies stolonal with simple creeping ranean. hydrorhiza; hydranths, small (0.25 mm) sessile, References: Rees and Russell (1937); Russell naked, fusiforme; hypostome short, conical; with a (1953); Kramp (1961); Goy et al. (1988, 1990, single whorl of 4-6 filiform tentacles; medusa buds 1991); Brinckmann-Voss (1987); Boero and Bouil- on hydrorhiza with a pedicel of variable length, gen- lon (1993); Schuchert (1996). erally longer than hydranth. Medusa: umbrella 2.5 mm wide, 4 mm high, with Amphinema turrida (Mayer, 1900) a high conical or globular apical projection; manubri- (Fig. 40G) um urn-shaped, with wide base, with a apical cham- Medusa: umbrella 4-7 mm high, somewhat ber; mouth cruciform, with 4 simple recurved lips; 4 higher than wide, with a conical, hollow apical broad ribbon-like radial canals, with jagged edges; projection; manubrium pyriform, almost as long with mesenteries; «gonads» interradial, horse-shoe- as subumbrellar cavity; mouth with four recurved, shaped, linked by a transverse interradial bridge; 2 crinkled lips; «gonads» sac-like, folded, extend- long opposite hollow marginal tentacles; marginal ing from adradial sides of the manubrium out- tentacular bulbs conical; up to 16 rudimentary bulbs wards along the 3/4 of the length of the four radi- with small tentacles; all bulbs with ocelli. al canals; typically 2 long, opposite, marginal ten- Records from Mediterranean: between Adriatic tacles with elongated, conical basal bulbs (some- and Ionian Sea. times 4 perradial tentacles, see Bigelow, 1909; Known seasonality: 7; 8. Goy, 1973) and 12 to 26 small solid tentaculae Distribution: Atlantic, Mediterranean. often reduced to small rudimentary bulbs; tentac- References: Kramp (1961); Boero et al. (1997).

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Genus Leuckartiara Hartlaub, 1914 um, orange brown, each with a pair of main longitu- dinal folds adjacent to the interradii, making a con- Hydroid: when known, forming stolonal colonies; tinous interradial groove and with a few isolated hydrocauli not or sparingly branched, covered by folds in the adradii mostly oriented perradially; no perisarc extending onto hydranth body forming a ocelli; . more or less gelatinous pseudohydrothecae which Records from Mediterranean: western Mediter- does not envelop the tentacles; hydranths with one ranean. whorl of oral filiform tentacles; medusae develop on Known seasonality: 12, 1. hydrocauli or hydrorhiza and are covered by a thin Distribution: Antarctic (Ross Sea, Weddell Sea); perisarc. Mediterranean. Medusa: pandeidae usually with an apical projec- References: Larson and Harbison (1990); Bouil- tion of varying shape; with large manubrium connect- lon et al. (2000). ed to radial canals by mesenteries; mouth with exten- Hydroid: unknown. sively folded or crenulated margin; «gonads» interra- dial, bipartite but connected interradially, typically Leuckartiara nobilis Hartlaub, 1913 horse-shoe-shaped, with horizontal folds directed per- (Fig. 41C) radially; radial canals broad and ribbon-like, often with jagged edges; with numerous hollow tentacles Medusa: umbrella up to 27 mm high and 20 mm with elongated, laterally compressed basal bulbs; wide, bell-shaped, with a well developed pointed or often with rudimentary tentacles; usually with ocelli. rounded solid apical projection; manubrium large, Only the hydroid of Leuckartiara octona is flask-shaped, with broad base and constricted near known (see below) mouth, more than half as long as subumbrellar cav- Recent reference: Schuchert (2004) ity; mouth with complexly folded, crenulated lips; «gonads» interradial, typically horse-shoe-shaped, Key to medusae covering whole walls of manubrium, with numerous divided horizontal folds; mesenteries along half the 1. With rudimentary marginal club-shaped tentacles length of manubrium; radial canals very broad, with ...... 2 irregular and jagged outlines and sometimes short – No club-shaped rudimentary marginal tentacles; lateral diverticula; about forty or more marginal ten- abaxial spurs not well developed...... L. nobilis tacles of different size, well spaced, tentacular bulbs 2. With ocelli; with pronounced abaxial spurs...... elongated, laterally compressed which clasp the ...... L. octona exumbrella margin, forming faintly developed abax- – Without ocelli, without spurs...... L. brownei ial spurs; no club shaped marginal rudiments; ocelli dark red. Leuckartiara species are often difficult to distin- Records from Mediterranean: western Mediter- guish, especially when immature (see diagnostic ranean. table in Xu et al., 1991 and in Pagès et al., 1992). Known seasonality: 3; 4. Distribution: Atlantic, Arctic; Indo-Pacific, Leuckartiara brownei Larson and Harbison, 1990 Mediterranean. (Fig. 41B) References: Kramp (1961); Goy (1973b); Gili (1986); Boero and Bouillon (1993); Medel and Medusa: umbrella 10 mm high and 9 mm wide, López-González (1996). conical, with a pointed apical projection of variable Hydroid: unknown. height; mesoglea fairly thick; velum narrow; manubrium greater than half of subumbrellar cavity; Leuckartiara octona (Fleming, 1823) mouth with large crenulated lips; radial canals four, (Figs. 41D-F) fairly broad, mostly smooth; mesenteries well devel- oped; four perradial marginal tentacles, large, taper- Hydroid: colonies generally epizootic, up to 5 ing, not laterally compressed; up to 28 rudimentary mm high, growing on various animals (gastropod tentacle, clasping the exumbrella, the oldest more shells, crabs, fishes, other hydroids) or on rocks, developed and interradial; all tentacles without stolonal, formed by single or slightly branched spurs; «gonads» on interradial walls of the manubri- hydrocauli arising from a creeping hydrorhiza and

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bearing a terminal hydranth and occasionally 1-3 twisted; with smooth or exceptionally slightly fold- lateral ones as well or, sometimes, with sessile ed or weakly corrugated «gonads», generally adra- hydranths; hydrocauli increasing in diameter from dial; with simple or faintly crenulated oral lips; with base distally; perisarc surrounding hydrocauli, firm, 4-8 or more marginal tentacles; with or without rudi- often annulated or wrinkled, especially at base and mentary bulbs or tentaculae; with or without ocelli. expending over the hydranth body in form of a gelatinous pseudohydrothecae reaching the base of Key to hydroids the tentacles but not investing them; pseudohy- drothecae often covered by detritus; hydranths with 1. Hydranth borne on erected stem and covered a single whorl of 6-12 filiform tentacles and a coni- with a wrinkled pseudohydrotheca .... M. galleri cal hypostome; medusa buds borne on short pedun- – Hydranth on very short pedicel and without cles completely invested by perisarc, arising from pseudohydrotheca...... M. tergestina hydrorhiza and hydrocaulus. Medusa: umbrella up to 20 mm high, higher than Key to medusae wide, bell-shaped, with a generally well developed conical or spherical solid apical projection, lateral 1. Umbrella dome-like, without an apical projection walls thin; manubrium of varying length, with broad ...... 2 base, flask-shaped; «gonads» interradial, typically – Umbrella with a conspicuous apical projection horse-shoe-shaped on whole surface of manubrium, ...... 3 with folds directed towards the perradii; radial 2. With only four perradial marginal tentacles...... canals with smooth or slightly jagged edges; mesen- ...... M. tregoubovii teries along about half the length of manubrium; – With 8-12 marginal tentacles and 24-36 with 12-32, usually 16, long marginal tentacles with rudimentary bulbs...... M. violacea long conical laterally compressed marginal bulbs 3. With a narrow, pointed apical projection; 4-8 clasping umbrella and forming a pronounced abaxi- marginal tentacles and a few rudimentary bulbs; al spur and with 16 or more club shaped marginal four simple faintly crenulated lips ...... rudimentary bulbs, all bulbs with abaxial ocelli...... M. tergestina Records from Mediterranean: eastern and west- – With a wide apical projection; 8-16 marginal ern Mediterranean; Adriatic Sea. tentacles; without rudimentary bulbs; mouth with Known seasonality: 2-8; 11. strongly folded lips...... M. galleri Distribution: Atlantic; Indo-Pacific; Mediter- ranean. Merga galleri Brinckmann, 1962 References: Kramp (1961); Goy (1973b); Millard (Figs. 41G-H) (1975); Schmidt and Benovic (1979); Bouillon (1980, 1985a); Gili (1986); Benovic and Bender Hydroid: colonies branched, arising from a (1987); Brinckmann-Voss (1987); Boero and Bouil- creeping hydrorhiza; hydranths borne on erected lon (1993); Altuna (1994); Avian et al. (1995); Ben- stems, each with a conical hypostome and one whorl ovic and Lucic (1996); Medel and López-González of up to six filiform tentacles; hydrorhiza and hydro- (1996); Schuchert (2001a). cauli, surrounded by a flexible perisarc covered by mud particles; perisarc forming a wrinkled pseudo- Genus Merga Hartlaub, 1914 hydrotheca reaching the base of the tentacles; medusa buds developing on the stems and surround- Hydroid: when known colonial, arising from a ed by perisarc. ramified hydrorhiza; hydrocauli slightly branched or Medusa: umbrella up to 1.15 mm high and 0.45 not; hydranths on hydrocauli or almost sessile; with mm wide, with a very large apical projection; or without pseudohydrothecae which when present manubrium with a large base; large with strongly does not envelop the tentacles; hydranths with one folded lips; radial canals broad, with slightly jagged whorl of filiform tentacles; free medusae arising outlines, entering manubrium by long mesenteries; 8 from hydrocauli and hydrorhiza. smooth, slightly folded «gonads», adradial, attached Medusa: Pandeidae with cruciform manubrium, to mesenteries and to the sides of the manubrium; with perradial edges of manubrium connected with marginal tentacles 8-11 in females, 11-16 in males; radial canals by long mesenteries; manubrium never marginal tentacular bulbs triangular, the four perra-

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dial with band-shaped ocelli the others with dot-like form; manubrium quadrangular, large; no gastric ocelli. peduncle; mouth with four simple recurved lips, Records from Mediterranean: western Mediter- slightly folded in old specimens; 4 large radial ranean. canals, ribbon-like, circular canal and velum nor- Known seasonality: reared in laboratory from mal; mesenteries along about half the length of the hydroids collected from May-September. manubrium; «gonads» appear first as 8 voluminous, Distribution: endemic of Mediterranean Sea. large, adradial contiguous masses, with an apical References: Brinckmann-Voss (1962); Boero and interradial bridge, usually fusing together and Bouillon (1993). becoming completely interradial with age; with 4 long, perradial, marginal tentacles; marginal tentac- Merga tergestina (Neppi and Stiasni, 1912) ular bulbs elongated conical. (Figs. 41I-J) Hydroid: unknown. Records from Mediterranean: western Mediter- Hydroid: colonies issued from a branched creep- ranean. ing hydrorhiza, forming a loose stolonal mat in old Known seasonality: 9, 10. well developed colonies, pedicels very short termi- Distribution: Indo-Pacific; Mediterranean. nating in a single hydranth, recovered with a thin References: Picard (1960b); Kramp (1961); Goy perisarc till the base of the hydranths, often (1973b); Bouillon (1980); Boero and Bouillon hydranths almost sessile, some longer and singly (1993). branched pedicels may occur in crowded colonies, upright pedicels not clearly demarcated from Merga violacea (Agassiz and Mayer, 1899) hydrorhiza; hydranth naked, elongated, almost (Fig. 42B) cylindrical, slightly tapering under tentacular whorl and basally, with a conical hypostome, with a small Medusa: umbrella up to 7 mm wide, 11 mm high, number of amphicoronate filiform tentacles (6-8) dome-like, without apical projection, with thick held rather stiffly out; medusa buds borne on short walls; manubrium half as long as bell cavity, cross- pedicels on hydrorhiza, rarely on hydranth pedicel, shaped in transverse section; mesenteries very long; enveloped by perisarc sheath. «gonads» adradial; 4 slightly crenulated lips; 8-12 Medusa: umbrella 4 mm wide, 7 mm high, with a long marginal tentacles and 24-36 rudimentary ten- narrow, pointed apical projection, with thin walls; tacles, all with ocelli. manubrium 1/2-2/3 as long as bell cavity; mouth lips Hydroid: unknown. faintly crenulated; mature «gonads» interradial, smooth, Records from Mediterranean: eastern and west- slightly folded; 4-9 marginal tentacles with ocelli and ern Mediterranean; Adriatic Sea. few rudimentary bulbs without ocelli; medusa present- Known seasonality: 7; 8. ing more than one period of sexual maturity. Distribution: Atlantic; Indo-Pacific; Mediter- Records from Mediterranean: eastern and west- ranean. ern Mediterranean; Adriatic Sea. References: Kramp (1924; 1961); Goy (1973b); Known seasonality: 1-3; 5-11. Goy et al. (1988, 1990, 1991); Boero and Bouillon Distribution: Atlantic; Indo-Pacific; Mediter- (1993). ranean. References: Vannucci and Yamada (1959); Genus Neoturris Hartlaub, 1913 Kramp (1961); Benovic (1973); Schmidt and Ben- ovic (1979); Brinckmann-Voss (1987); Bouillon Hydroid: when known forming colonial hydroids (1980); Goy et al. (1988, 1990, 1991); Boero and arising from stolonal hydrorhiza with terminal Bouillon (1993); Avian et al. (1995); Benovic and hydranth; perisarc of hydrocauli continuing up to the Lucic (1996). hydranth body but does not surround the tentacles; hydranths with one whorl of filiform oral tentacles; Merga tregoubovii Picard, 1960 free medusae developing from hydrocauli some- (Fig. 42A) times from hydrorhiza, gonophores completely cov- ered with perisarc. Medusa: umbrella 2.5 mm wide and high, globu- Medusa: Pandeidae with apical projection vary- lar, without apical projection; mesoglea thin, uni- ing much in shape and size, often reduced; manubri-

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um very large and broad, with well developed hydranth, with a single row of 3-4 filiform tentacles; mesenteries; «gonads» in 8 adradial series with free medusa borne isolated on hydrorhiza. transverse folds directed towards interradii; Medusa: Pandeidae with eight simple radial depressed interradial parts of manubrium with iso- canals, with or without gastric peduncle; with trans- lated pits of «gonads»; with 8 or more hollow mar- versely folded «gonads»; without mesenteries. ginal tentacles with laterally compressed basal bulbs; without rudimentary tentacles or marginal Octotiara russelli Kramp, 1953 warts; mostly without ocelli. (Fig. 42F-H)

Neoturris pileata (Forskål, 1775) Hydroid: colonies with stolonal hydrorhiza, sym- (Figs. 42C-E) biotic with the bryozoan Steginoporella mandibula- ta; hydranth rising among zoeciae about 0,5 mm Hydroid: colonies attached to shells of the high, with a single row of 3-4 filiform tentacles; bivalve mollusc Nucula living in deep water; white rounded hypostome, reddish column; hydro- hydrorhiza forming a close network of anastomos- caulus short, covered by thin perisarc; medusa buds ing stolons; hydranths borne on erect unbranched isolated on hydrorhiza. hydrocauli which are covered by an irregularly or Medusa: umbrella 7-11 mm wide, flatter than a spirally coiled perisarc; hydranths spindle-shaped hemisphere, sometimes with a large and broad gas- with a prominent conical hypostome and with 4-9 tric peduncle; manubrium in its entire length with filiform oral tentacles in a single whorl; perisarc eight deep longitudinal furrows; mouth tube long forming a pseudohydrotheca extending till the base with 8 sharp edges terminating in 8 pointed lips; of tentacles; medusa buds on stems, or less com- «gonads» along each of the eight perradial edges of monly on stolons, completely covered by perisarc. the manubrium, deeply transversally folded, each Medusa: Umbrella up to 25 mm wide and 40 mm with 7-10 furrows; with eight radial canals; usually high, bell-shaped, with variable apical projection; 8 large marginal tentacles, but occasionally up to 32, manubrium flask-shaped, of very variable length, with about 64 small rudimentary tentacles; all with- never extending beyond exumbrellar margin, with out ocelli. broad base; mouth with very complexly folded and Records from Mediterranean: western Mediter- crenulated lips; mesenteries about half as long as ranean. manubrium; radial canals broad with short, some- Known seasonality: 4. times branched lateral diverticula; «gonads» in 8 Distribution: Indo-Pacific; Mediterranean. adradial series with transverse folds directed References: Kramp (1961); Kramp (1965, 1968); towards interradii; depressed interradial parts of Goy (1973b); Boero and Bouillon (1989; 1993). manubrium with isolated pits of «gonads»; up to 90 (usually 60-80) marginal tentacles, densely crowd- Genus Pandea Lesson, 1843 ed, marginal bulbs clasping exumbrella but not forming conspicuous abaxial spurs; without ocelli. Hydroid: hydroids when known forming stolonal Records from Mediterranean: western Mediter- colonies arising from a creeping, ramified hydrorhiza ranean; Adriatic Sea. fixed on the planktonic gastropod Clio cuspidata; Known seasonality: 1-8; 11; 12. hydranths naked, almost sessile; hydranths with fili- Distribution: Atlantic; Mediterranean. form oral tentacles in 2 closely set whorls; free References: Babnik (1948); Kramp (1961); medusae borne on short pedicels covered by perisarc Edwards (1965); Berhaut (1970); Goy (1973b); and arising directly from hydrorhiza. Schmidt and Benovic (1979); Gili (1986); Benovic Medusa: Pandeidae with or without apical pro- and Bender (1987); Boero and Bouillon (1993); jection; with or without longitudinal exumbrellar Avian et al. (1995); Benovic and Lucic (1996); cnidocysts ribs; «gonads» at first in the adradii and Medel and López-González (1996). eventually encircling manubrium, forming a com- plex network; lips wide and folded; radial canals rib- Genus Octotiara Kramp, 1953 bon-like; with long mesenteries; with more than 8 hollow marginal tentacles; without rudimentary Hydroid: colonies with stolonal hydrorhiza; marginal tentacles or marginal warts; with or with- hydrocaulus short, covered by thin perisarc; out ocelli.

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Pandea conica (Quoy and Gaimard, 1827) striction, with a large cluster of cnidocysts or “cap” (Figs. 43A-B) somewhat displaced onto one side of the hypostome, with 2 filiform tentacles arising close together, Hydroid: colonies arising from a creeping, rami- under the hypostomial constriction, opposite to the fied, stolonal hydrorhiza living on the planktonic cnidocysts cluster; gonozooids and dactylozooids, gastropod Clio cuspidata; stolons thin covered by a without tentacles, mouthless and smaller the gastro- fine perisarc, hydranths naked, on a short stem, zooids; free medusae lying very close to the tip of almost sessile; hypostome conical; 8 filiform oral the gonozooid. tentacles of variable length in 2 closely set whorls; Medusa: Anthomedusae without statocysts and medusae buds borne on short pedicels covered by ocelli; without centripetal canals; manubrium with perisarc and arising directly from hydrorhiza. 4-6 or more radial gastric lobes extending along Medusa: umbrella up to 10 mm wide and 21 proximal portions of radial canals; with «gonads» (sometimes 30 mm) high, bell-shaped, with a round- surrounding manubrium and extending onto the gas- ed, bluntly or conical projection variable in length tric lobes; radial canals branched, obliterated canals and ending in a peculiar opaque ectodermal thicken- may be present; usually without circular canal but ing, mesoglea fairly thick mainly at top; with 16-24 with a solid endodermal marginal core; with numer- (up to 44) longitudinal exumbrellar cnidocyst tracks ous exumbrellar cnidocysts clusters or bands alter- that correspond to the number of marginal tentacles nating with tentacles; marginal tentacles hollow, and originate from each tentacular bulb; manubrium with swollen hollow base connected to the lumen of large, pyramidal, almost filling upper half of sub- the radial canals. umbrellar cavity; mouth with short oral tube, with 4 Remarks: the systematical position of the Pro- perradial much folded and highly crenulated lips; boscidactylidae is not clear; they have traditionally radial canals fairly narrow, smooth, slightly jagged, been included in the Limnomedusae, mostly conve- circular canal narrow; mesenteries about 4/5 of nience and ignorance of their real affinities. Several manubrium length; gonad large, on entire interradi- authors consider that by some characters, mainly the al walls of manubrium, forming a coarse meshed- structure of their tentacular base and the presence of network of ridges with pits between; with 16-24 desmonemes, they should be referred to the (sometimes up to 44) marginal tentacles, with coni- Anthomedusae Filifera (see Werner, 1984; Petersen, cal, laterally compressed bulbs clasping the umbrel- 1990; Schuchert, 1996). We tentatively follow here la margin but devoid of well-developed abaxial this suggestion and include them in the Pandeida spurs, no secondary tentacles; with ocelli. because their hollow tentacles, but even in this sub- Records from Mediterranean: eastern and west- order their relationships with the other families are ern Mediterranean. not obvious. If the presence of desmonemes appears Known seasonality: 1-9; 12. a valid argument to include this family in the Distribution: Atlantic; Indo-Pacific; Mediter- Anthomedusae Filifera the presence of macrobasic ranean. euryteles in most of the Proboscidactyla species is References: Picard (1956a); Kramp (1961); confusing, this type of cnidocysts having only been Berhaut (1970); Goy (1973b); Schmidt (1973); found inside the Filifera in some species of the very Dowidar (1983); Gili (1986); Brinckmann-Voss particular family Eudendriidae. (1987); Dallot, Goy and Carré (1988); Boero and Bouillon (1993); Medel and López-González Genus Proboscidactyla Brandt, 1835 (1996); Mills et al. (1996). Hydroid: with the characters of the family. Family PROBOSCIDACTYLIDAE Medusa: Proboscidactylidae with manubrium Hand and Hendrickson, 1950 presenting radial gastric lobes; «gonads» on manubrium and gastric lobes; with 4-6 or more Hydroid: colonies of single hydroids arising from branched radial canals, with clusters or bands of creeping naked stolons located around the lips of cnidocysts on the exumbrella; usually without circu- sabellid polychaete tubes; hydranths almost sessile, lar canal; marginal tentacles hollow. polymorph with gastrozooids and gonozooids, sometimes dactylozooids, gastrozooids with round- Proboscidactyla ornata (McCrady, 1859) ed hypostome, separated from the body by a con- (Figs. 43C-D)

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Hydroid: colonies of single naked hydroids aris- ous hollow tentacular bulbs, four simple radial ing from a creeping naked stolon located around the canals and a circular canal, mouth with four simple lips of sabellid polychaete tubes; hydranths poly- lips; «gonads» interradial, with smooth surface; with morphic, basal part of gastrozooids with a small or without mesenteries; without rudimentary bulbs; stalk which is almost unseen when contracted; gas- margin with or without cirri-like tentacles; excep- trozooids increasing in width from base to top; with tionally with ocelli. rounded hypostome, separated from the body by a Remarks: the differences between the diagnoses of constriction, with a large cluster of cnidocysts or the Protiaridae and Pandeidae appears at first sight “cap” somewhat displaced onto one side of the rather small but the cnidome of the Protiaridae is very hypostome, with 2 filiform tentacles arising close particular, containing among others, merotrichous together, under the hypostomial constriction, oppo- isorhizas a type of cnidocysts which characterises site to the cnidocysts cluster; gonozooids, without normally only Leptomedusae families (Eirenidae, tentacles, mouthless and smaller the gastrozooids, 1- Eucheilotidae, Lovenellidae and Tiaropsidae). 2 medusa buds lying very close to the tip of the gonozooid. 1. Without marginal cirri ...... Protiara Medusa: umbrella 5 mm wide, slightly higher – With marginal cirri ...... Halitiara than hemispherical, mesoglea thick and rigid; manubrium normally with four radial lobes; mouth Genus Halitiara Fewkes, 1882 with four simple recurved lips; typically with four primary radial canals branching into 16-20 (rarely Medusa: Pandeidae with 4 straight radial canals; more) terminal branches and as many tentacles; no with 4 perradial marginal tentacles and several inter- ring canal; medusa buds arising from corners of mediate, solid cirrus-like marginal tentacles; with- manubrium or forking from radial canals; polypoid out rudimentary marginal bulbs; mouth a simple structures on manubrium? cruciform opening; with or without mesenteries; Records from Mediterranean: eastern and west- interradial «gonads»; without ocelli, cnidome with ern Mediterranean; Adriatic. merotrichous isorhiza. Known seasonality: 1-12. Hydroid: see below Halitiara inflexa. Distribution: Circumglobal in warm coastal waters. 1. With apical projection, without mesenteries...... References: Kramp (1961); Brinckman and Van- ...... H. formosa nucci (1965); Vannucci (1966), Goy (1973b); – Without apical projection, with mesenteries...... Brinckmann-Voss (1987); Goy et al. (1988, 1990, ...... H. inflexa 1991); Boero and Bouillon (1993); Avian et al. (1995); Benovic and Lucic (1996). Halitiara formosa Fewkes, 1882 (Fig. 43E) Family PROTIARIDAE Haeckel, 1879 Medusa: umbrella about 3 mm high, pear- Hydroid: known only in Halitiara inflexa (Bouil- shaped, with solid apical projection, about half as lon 1985a, b; Bouillon, Seghers and Boero, 1988) long as bell cavity; no mesenteries; manubrium pyri- and Halitiara formosa (Brinckmann-Voss, pers. form, about half as long as subumbrellar cavity; 4 comm.) and are also very different of Pandeidae long, hollow marginal tentacles and 24-35 short, polyps, showing some resemblance to certain Cam- solid, tightly coiled marginal cirrus-like tentacles; panulinidae hydroid species and mainly with Trichy- «gonads» interradial smooth; no ocelli. dra polyps (Bouillon, Seghers and Boero, 1988). Hydroid: see family. Colonies arising from creeping stolons, hydranths Records from Mediterranean: eastern and west- issued from very short hydrocauli; hydrorhiza and ern Mediterranean. hydrocauli recovered by perisarc, which forms a cup Known seasonality: 8-11. at the base of the hydranths; hydranths with one Distribution: Atlantic; Indo- Pacific; Mediter- whorl of filiform tentacles, large cnidocysts alternat- ranean. ing with the tentacles; gonophores unknown. References: Kramp (1961); Goy (1973b); Bouil- Medusa: Anthomedusae with only four fully lon (1980; 1995b); Brinckmann-Voss (1987); Goy et developed marginal tentacles arising from conspicu- al. (1988, 1990, 1991); Boero and Bouillon (1993).

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Halitiara inflexa Bouillon, 1980 al tentacles; marginal tentacular bulbs thickened (Figs. 43F-G) each with an ocelli. Records from Mediterranean: western Mediter- Hydroid: colonies arising from creeping stolons, ranean, Adriatic Sea. hydranths issued from very short hydrocauli; Distribution: Atlantic; Mediterranean. hydrorhiza and hydrocauli recovered by perisarc, Known seasonality: 10. which forms a cup at the base of the hydranths in References: Hartlaub (1913); Pell (1918); Kramp which they can almost completely retract; (1959a, 1961); Boero and Bouillon (1993); Benovic hydranths, very slender, elongated, cylindrical, with and Lucic (1996). short and conical hypostome, with one whorl of Hydroid: unknown. about 10 long filiform tentacles with irregular clus- ters of cnidocysts, large cnidocysts alternating with Family PTILOCODIIDAE Coward, 1909 the tentacles; gonophores unknown. Medusa: umbrella bell-shaped, 1.6 mm high and Hydroid: hydrorhiza stolonal, reticular, or 1.2 mm in diameter; mesoglea moderately thick, encrusting, covered by naked coenosarc; hydranths gradually thickening towards top to about twice the sessile, naked and polymorphic; gastrozooid without thickness of the lateral walls; manubrium volumi- tentacles; dactylozooid with 4 or more capitate ten- nous, quadrangular, length about two-thirds of bell tacles, sometimes filiform; gonophores on gono- cavity, joined to radial canals by mesenteries for half zooids or gastro-gonozooids; reproduction by fixed of their length; mouth with 4 simple lips; «gonads» sporosacs, eumedusoids or free medusae. large, bulging, filling interradial position complete- Medusa: umbrella more or less bell-shaped; with ly, living free only a small perradial band of or without radial exumbrellar furrows; didermic manubrium and the mouth region; four radial canals centripetal tracks or exumbrellar rows of refringent and circular canal, all narrow and with smooth mar- spots; with marginal cnidocyst ring; when present, gins; 4 long perradial marginal tentacles with broad marginal tentacles solid, with tips armed with cnido- conical tapering base, not laterally compressed; cysts; 4 radial canals and circular canal; manubrium between each pair of marginal tentacles 3-6 short tubular or bottle-shaped, with mouth arms with ter- solid coiled cirri- like tentacles without bulbs. minal cnidocyst clusters, “gonads” adradial or inter- Records from Mediterranean: eastern Mediter- radial. ranean. References: Jarms (1987); Bouillon (1995a); Seasonality:? Bouillon et al. (1997); Bouillon and Boero (2000). Distribution: Indo-Pacific; Mediterranean. Remark: two genera are only present in the References: Kramp (1961); Bouillon (1980, Mediterranean Thecocodium as hydroid with fixed 1985b, 1995b); Bouillon, Seghers and Boero sporosacs and Tregoubovia only known by its (1988); Goy et al. (1988, 1990, 1991); Boero and medusa stage. Bouillon (1993). Genus Thecocodium Bouillon, 1967 Genus Protiara Haeckel, 1879 Colonies dimorphic, stolonal, hydrorhiza cov- Protiaridae with 4 marginal tentacles, without ered with perisarc, reproduction by fixed sporosacs. marginal cirri or tentaculae; with 4 smooth «gonads» on manubrium; mouth with 4 simple lips; Thecocodium brieni Bouillon, 1967 without mesenteries. (Fig. 44B)

Protiara tetranema (Péron and Lesueur, 1810) Polyps arising from an irregular network of anas- (Fig. 44A) tomosing stolon enclosed in thin perisarc. Gastro- zooids without tentacles; dactylozooids tubular, Medusa: umbrella 4 mm high, 4 mm wide, elongated, retractile, more numerous than gastro- almost cubical; without apical projection; manubri- zooids, without internal cavity neither apical orifice um likewise cubical, half as long as umbrella cavity; and with 4-5 capitate tentacles apically. Gonozooids mouth with 4 simple, not folded nor crenulated lips; similar to gastrozooids from which they develop by 4 cylindrical «gonads», perradial (!); 4 long margin- the growth, near the base of polyp, of a single

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gonophore, males fixed sporosacs, females eumedu- lips elongated to form either simple or branched oral soids. Cnidome: microbasic euryteles around gastro- arms armed with terminal and usually also lateral zooid hypostome and on dactylozooids tentacles; clusters of cnidocysts; with 4 to 8 radial canals and desmonemes on tentacles of dactylozooids. circular canal; with «gonads» generally completely Records from Mediterranean: western Mediter- surrounding manubrium; with 8 groups of solid mar- ranean. ginal tentacles; without ocelli. Distribution: north eastern Atlantic, Meditter- anean. Genus Rathkea Brant, 1838 References: Bouillon (1967); Edwards and Har- vey (1983); Boero and Bouillon (1993). Hydroid: with the characters of the family. Medusa: Rhathkeidae with 4 radial canals and 4 Genus Tregoubovia Picard, 1958 oral arms armed with clusters of cnidocysts.

Ptilocodiidae medusae without exumbrellar fur- Rathkea octopunctata (M. Sars, 1835) rows; with didermic centripetal tracks; without mar- (Figs. 44D-H) ginal tentacles or marginal tentacular bulbs; with interradial «gonads». Hydroid: colonies stolonal arising from ramified Hydroid: unknown. creeping stolons; hydranths small, sessile, cylindri- cal, naked except at their base surrounded by a thin Tregoubovia atentaculata Picard, 1958a gelatinous envelope; hypostome rounded-conical, (Fig. 44C) one whorl of 4-6 thread-like filiform tentacles; medusa buds arising from stolons, exceptionally Medusa. umbrella 3.2 mm high, ovoid, mesoglea from hydranth. fairly thick; with up to 16 exumbrellar didermic Medusa: umbrella somewhat globular, up to 3-4 centripetal processes issuing from marginal cnido- mm high and 4 mm wide, with rounded or dome- cyst ring; velum normal; manubrium large, qua- shaped apical process, mesoglea moderately thick, dratic; mouth quadratic with 4 rather long perradi- especially in the apical region; velum broad; al oral expansions, with one terminal cluster of manubrium short, cylindrical or four-sided, with cnidocysts, with four radial canal and circular conical peduncle, 1/3 to 1/4 of length of umbrella canal narrow, with short mesenteries; «gonads» cavity, not reaching beyond umbrella margin in full interradial; without marginal tentacles or marginal extension; mouth with four lips, each divided in two bulbs; no ocelli. short stalked cnidocysts knobbed arms; in fully Records from Mediterranean: western Mediter- developed specimens one or two pairs of lateral ranean. cnidocysts clusters upon the sides of each lips; bases Known seasonality: 6. of oral arms continued on manubrium for some Distribution: endemic of Mediterranean Sea. length as perradial ridges; four radial canals and cir- References: Picard (1958a), Goy (1973b); Boero cular canal narrow; «gonads» completely surround- and Bouillon (1993); Bouillon et al. (1997). ing manubrium; eight marginal tentacular bulbs; four perradial each with up to five tentacles, four Family RATHKEIDAE Russell, 1953 interradial bulbs each with up to three tentacles, at full development; no ocelli; medusa buds on Hydroid: colonial hydroids arising from rami- manubrium, exclusively from ectodermal origin. fied, creeping stolons; hydranths monomorphic, ses- Records form Mediterranean: eastern and western sile, with one whorl of filiform tentacles surround- Mediterranean; Adriatic; Black Sea. ing a rounded hypostome; hydranth base surrounded Known seasonality: 1-5. by a thin gelatinous envelope; free medusa develop- Distribution: Atlantic; Indo-Pacific; Arctic; ing on hydrorhiza or more rarely at the base of Mediterranean. hydranths. References: Werner (1956, 1958); Bouillon Medusa: Anthomedusae with somewhat globular (1961-1962); Bouillon and Werner (1965); Berhaut umbrella, with slight apical process; manubrium, (1970); Goy (1973b); Gili (1986); Boero and Bouil- short, cylindrical, not extending beyond umbrella lon (1993); Avian et al. (1995); Benovic and Lucic margin; with gastric peduncle; with mouth with 4 (1996); Medel and López-González (1996).

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Family RHYSIIDAE Brinckmann, 1965 mouth margin, without terminal cnidocyst clusters; mouth with four perradial lips; marginal tentacles Colonies stolonal, hydrorhiza covered with peris- hollow, without basal swellings, in 8 groups, 4 per- arc. Gastrozooids naked, with one whorl of filiform radial and 4 adradial, each group with one large and tentacles around a conical hypostome; dactylo- two small tentacles; basal part of large tentacles zooids filiform and without capitate tentacles, cov- sunken into deep furrows of umbrella margin; with ered with perisarc up to the apical extreme which it 8 adradial «gonads»; with adaxial red ocellus at base armed with cnidocysts. Gonads on hydranths similar of free portion of tentacles. with the gastrozooids, no gonophores; male Hydroid unknown. hydranths with 3 or 4 filiform tentacles, female hydranths transform itself resembling a sporosac Genus Russellia Kramp, 1957a structure. With the characters of family. Genus Rhysia Brinckmann, 1965 Russellia mirabilis Kramp, 1957a Rhysiidae with polymorphic colonies. Gastro- (Fig. 45A) zooids and gonozooids naked, arising directly from a creeping stolon. Tentaculozooids covered with Medusa: umbrella up to 9 mm wide, 15 mm high; perisarc up to the terminal cnidocyst cluster. Gono- apical projection large; gastric peduncle short, zooids similar to gastrozooids; male polyps with tes- broad; mouth quadrangular, with short perradial ticle which may occupy 8/10 of the body wall; lips; oral tentacles finger-shaped, with scattered female polyps becoming completely converted into cnidocysts along entire length; free end of large ten- a sporosac with the endoderm forming a spadix tacles filiform?; «gonads» smooth occupying entire feeding one egg, developing into a planula. length of manubrium. One species in the Mediterranean. Records from Mediterranean: western Mediter- ranean. Rhysia autumnalis Brinckmann-Voss, 1965 Known seasonality:4. (Fig. 44I) Distribution: Antarctic; Atlantic (West Indies); Mediterranean. Colonies with an anastomosing stolon which References: Navas-Pereira and Vannucci (1990); forms a wide and irregular net; perisarc covering the Pagès et al. (1999). stolon up to the base of the polyps. Tentaculozooids with a stem covered by a perisarc and a terminal Family STYLASTERIDAE Gray, 1847 cluster of cnidocysts. Gastrozooids with 10 to 12 tentacles. Female gonozooids with 6 to 10 tentacles, Colonies erect and branched with a thick calcare- which become reduced during the development of ous exoskeleton (coenosteum); polyps polymorphic the embryo; male gonozooids with 3 or 4 tentacles and retractile; gastrozooids with one whorl of fili- which remain intact during the ripening of the form tentacles, exceptionally without any tentacle, gonad. Cnidocysts: stenoteles, microbasic euryteles gastric cavity containing usually a central style (gas- and desmonemes. trostyle); dactylozooids filiform, without tentacles. Records from Mediterranean: western Mediter- The two types of polyps are irregularly distributed ranean. or, more frequently, arranged in circles (cyclosys- Known seasonality: 9-1. tem) where one gastrozooid is surrounded by sever- Distribution: endemic of Mediterranean Sea. al dactylozooids. Gonophores reduced and devel- References: Brinckmann-Voss (1965b); Boero oped inside the “ampullae”, globose structures in the and Fresi (1986); Brinckmann-Voss et al. (1993) exoskeleton, in the colony surface, the female bigger than the male. Family RUSSELLIIDAE Kramp, 1957 Reference: Cairns (1991). Remarks: The Stylasteridae are very closely Anthomedusae with a apical projection; related to the Hydractiniidae but are represented by manubrium mounted upon a gastric peduncle; with only one species in Mediterranean: Errina aspersa four unbranched oral tentacles attached above see below.

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Genus Errina Gray, 1835 Records from Mediterranean: eastern and west- (Figs. 45B-C) ern Mediterranean. Known seasonality: 6; 7. Colonies usually flabellate but may be slightly Distribution: Atlantic, Mediterranean. bushy; branches robust to delicate, usually round in Reference: Zibrowius and Cairns (1992). cross section, major may not anastomose; coenos- teal texture usually reticulate with irregularly Family TRICHYDRIDAE Hincks, 1868 shaped granules, but may be linear and have low, rounded granules; the sides of dactylopore spines Hydroid: colonies stolonal, with creeping stolon are sometimes imbricate; coenosteum white, orange, recovered by thin perisarc; hydranths sessile, with or pink; gastro- and dactylopores usually randomly base surrounded by a collar-like tube of perisarc, arranged on branch; however, gastropores often with one amphicoronate whorl of filiform tentacles; more abundant on anterior side, sometimes aligned gonophores and cnidocysts unknown. along the anterior or lateral branch edges; mayor Medusa: Anthomedusae without peduncle; gastropores may not bear an abcauline lip; gas- mesoglea especially thick in upper part of umbrella; trostyles usually of medium H/W; however, they with four large, simple, pleated lips; with 4 radial range from 1.6-2.6 mm, the longer styles held in canals; with numerous fine, lateral branched, anas- place by transverse tabulae; styles lanceolate, usual- tomosing centripetal canals connecting non perradi- ly vertically ridged, the ridges bearing simple and al marginal bulbs to the radial canals; «gonads» fused spines; a ring palisade present in some interradial; with solid marginal tentacles; with trian- species; dactylopore spines shaped as grooved gular marginal bulbs; without ocelli or any other tubercles, the grooves predominantly directed away apparent sense organ. from the branch tip (adcauline); walls of the dacty- Remarks: the medusae of Trichydra were pre- lopore spines usually thick, such that the groove viously included in the Proboscydactilidae (as constitutes only one-third the width of the spine; Pochella) but the «gonads» are not radial out- spines vary greatly in size from rudimentary to over growth of the stomach and there are no exumbrel- 1 mm tall; small dactylopores also occur as slits, lar cnidocysts chambers characteristic of this lat- flush with the branch surface; spines often clustered ter family. The discovery of their alleged cycle and sometimes composite; no dactylostyles; ampul- does not resolve the problem of their taxonomical lae vary from internal to slightly submerged to fully position; Trichydra polyps have been considered superficial hemispheres. as Corynidae, as Campanulariidae, or to being Reference: Cairns (1991). next to the Lafoeidae and also tentatively as being the hydroid of Lizzia blondina (See Edwards, Errina aspera (Linnaeus, 1767) 1973a for a review). They present great morpho- (see photos Figs. 9 and 10 in Zibrowius and Cairns, logical affinities with the polyps of Halitiara 1992) inflexa Bouillon, 1980 (see Bouillon Seghers and Boero, 1988; Bouillon, 1985b). The medusae Colonies primarily uniplanar but sometimes have typical Anthomedusae characters in the bushy, up to 20 cm high and wide; branches cylin- structure and the form of the manubrium and of drical, gradually tapering to pointed tips; coenos- the «gonads» and in the structure of the tentacles teum white and porous, predominantly of reticulate- but they differ from Halitiara medusae by sever- granular texture, but sides of dactylopore spines and al important characters. inner gastropore tube surface imbricate; coenosteal Perhaps the study of the cnidome will give strips wide, granules irregular in shape; gastropores enough information’s to solve this systematical puz- circular, tubular, lacking ring palisade, without zle; the Halitiara having very particular cnidocysts proximal lips; gastrostyle occupies lower half of for Anthomedusae: merotrichous isorhiza. (See this gastropore tube, lanceolate, bearing short vertical paper Halitiara inflexa). spiny ridges; dactylopore spines mainly on distal branches, female ampullae hemispherical and often Genus Trichydra Wright, 1858 spinose as a result of short dactylopore spines, male ampullae internal, elliptical in shape, communicat- Medusa and hydroids with the characters of the ing to surface by a narrow efferent pore. family.

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Trichydra pudica Wright, 1858 duction leading to planulae or actinulae; planulae (= Pochella polynema) (Fig. 45D-E) with usually two types of ectodermal embryonic glandular cells: spumous and spheroulous ones. Hydroid: colonies stolonal, with creeping stolon References: Petersen (1990); Schuchert (1996; recovered by thin perisarc; base of hydranth sur- 2001a). rounded by a collar-like tube of perisarc into which the hydranth can partially retract, when contracted Key to hydroids only the tips of the tentacles show beyond the edge of the perisarc; hydranth cylindrical, very slender 1. Hydranths with aboral tentacles only...... 2 and extensible, with short conical hypostome; 6 – Hydranths with oral and aboral tentacles...... 3 solid, amphicoronate filiform tentacles carrying 2. Hydranth with numerous capitate tentacles numerous irregularly disposed cnidocysts; young arranged in 3-6 irregular aboral whorls around medusae were obtained from rearing by Edwards middle part of the hydranth body and with (1973a) from clinkers, he could however not creeping stolonal hydrorhiza or with tentacles in observed the gonophores. 1 or 5-6 close alternate aboral whorls Medusa: umbrella about 4 mm wide and 3.5 mm surrounding base of hypostome and with mat- high, somewhat bell-shaped to hemispherical; no like hydrorhiza, forming a basal plate...... exumbrellar cnidocysts tracks but exumbrella with ...... Sphaerocorynida scattered cnidocysts, apical mesoglea thick forming a – Hydranth claviform; with long hypostome; rounded-conical apical projection; velum fairly tentacles scattered in one or more aboral whorls broad; manubrium large, four-sided, about two-thirds under hypostome, hydrocaulus not clearly of subumbrellar cavity; mouth with four large, wavy, demarcated, short, ending in pedal disc or pleated lips; 4 straight, smooth radial canals, fairly creeping stolon...... Moerisiida broad, with funnel-shaped dilatations at their origins 3. Hydranth with solid or parenchymatical oral of the manubrium; with numerous fine, branched, tentacles in one whorl around hypostome or often anastomosing, centripetal canals, connecting spreading down over hydranth body; with solid non perradial marginal bulbs to the radial canals; cir- or parenchymatical aboral tentacles in one or cular canal visible in young specimens, embedded in three whorls or absent...... Tubulariida the base of the crowded marginal bulbs in adults; – Hydranths mono- or polymorphic, oral tentacles «gonads» four, large, interradial pads; up to 48 ( or capitate or moniliform, aboral tentacles in whorls more) long, marginal, filiform solid tentacles with or scattered, either capitate, moniliform, ramified somewhat triangular marginal bulbs; no ocelli. capitate, reduced, or without tentacles; hydroids Records from Mediterranean: eastern Mediter- as floating or fixed colonies; fixed colonies ranean; Adriatic Sea. arising either from simple creeping stolonal Known seasonality: 2; 4; 5; 8; 11. tubes, from an encrusting basal mat, from upright Distribution: Atlantic, Indo-Pacific; Mediter- branched hydrorihza consisting of a central axis ranean. of perisarc covered by coenosarc, or from a References: Rees (1941a); Edwards (1973a); calcified exoskeleton ...... Zancleida Schmidt and Benovic (1979); Arai and Brinckmann- Voss (1980); Bouillon (1985a); Goy et al. (1988, Key to medusae 1990, 1991); Boero and Bouillon (1993). 1. Marginal tentacles developed only at junction Order CAPITATA Kühn, 1913 between radial canals and circular canal...... 2 – Marginal tentacles developed at junctions Hydranths: usually with capitate tentacles either between radial canals and circular canal and in the adult polyps or during their larval life; along entire circular canal (except Tiaricodon); gonophores generally borne on hydranth body. manubium quadrate; mouth cruciform; Medusa: with “gonads” usually completely sur- interradial “gonads” on manubrium and radial rounding the manubrium; mouth simple and circu- lobes or on radial lobes only...... Moerisiida lar; marginal tentacles usually hollow (solid in 2. Manubrium with flask-shaped quadrate or Margelopsidae and Porpitidae); cnidome charac- cruciform manubrium, mouth tube ending in terised by the presence of stenoteles; sexual repro- round or cruciform mouth; with interradial

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“gonads” ...... 3 in one whorl under hypostome; eggs and sperm – Generally with cylindrical manubrium with developed directly in ectoderm of polyps in wart- circular base; mouth usually simple and circular; like protuberances, in hermaphrodite species “testis” “gonads” normally completely surrounding develop on upper part of hydranth, “ovaries” on manubrium ...... Tubulariida lower part; asexual reproduction by lateral buds, 3. Usually with exumbrellar cnidocyst pouches or leading only to temporary colonies; lower part of tracks; tentacles with cnidophores (except the hydranth with simple pedal disc and with central Porpitidae) ...... Zancleida pore, no perisarc except on encysted embryos. – Medusae without this characters ...... Remark: The Hydridae are here included in the ...... Sphaerocorynida Moerisiida (see Bouillon, 1985 and Petersen (1990) for comments) but it is not excluded that they may Suborder MOERISIIDA Poche, 1914 form an order by themselves.

Hydroid: hydranth claviform, with long hypos- Genus Hydra Linné, 1758 tome; tentacles aboral, scattered, or in one or more = Chlorohydra Schulze, 1917 whorls under hypostome base; hydrocaulus not clearly = Pelmatohydra Schulze, 1917 demarcated, short, ending in pedal disc or in a creeping (Figs. 45F-H) stolon; free medusae or reduced gonophores. Medusa: manubrium quadrate, forming radial With the characters of the family lobes; mouth cruciform; “gonads” interradial, on A list of the European species is given by manubrium and radial lobes or on radial lobes only; Grayson (1971). marginal tentacles developed at junctions between References: Campbell (1987) Avian et al. (1995). radial canals and circular canal and along entire cir- cular canal (except Tiaricodon); tentacular bulbs Family MOERISIIDAE Poche, 1914 usually with abaxial ocelli; planulae with usually two types of ectodermal embryonic glandular cells: Hydroid: hydranths with aboral tentacles monili- spumous and spheroulous ones. form or modified moniliform, scattered or in one References: Petersen (1990); Bouillon (1999); whorl around middle part of the hydranth body; Bouillon and Barnett (1999); Bouillon and Boero medusa buds on short pedicels between or just under (2000). the tentacles; polyp buds produced from lower part of hydranth; hydrocaulus short, ending in pedal disc Key to hydroids forming podocysts, or with short stolon-like tubes ending in podocysts or hydranths. 1. Hydranth with tentacles...... 2 Medusa: manubrium prismatic, with radial lobes – Hydranth without tentacles = Protohydridae on proximal parts of the 4 radial canals; no gastric 2. Hydranth with filiform or modified moniliform peduncle; with or without centripetal canals; mouth tentacles, in one whorl under hypostome; living simple, cruciform; usually without lips except in in freshwater ...... Hydridae oldest specimens; “gonads” on manubrium and sur- – Hydranth with moniliform or modified rounding manubrial lobes or only on manubrial moniliform tentacles scattered or in one whorl lobes overlying the radial canals; with either 4, or around middle part of body; living in brackish or 16-32, or several hundreds moniliform or modified sea water...... Moerisiidae moniliform hollow marginal tentacles with adnate bulbs; abaxial ocelli; no statocysts. Key to medusae References: Petersen (1990); Bouillon (1995a; 1999); Bouillon and Barnett (1999); Bouillon and Only one family present in the Mediterranean = Boero (2000). Moerisiidae Key to hydroids Family HYDRIDAE Dana, 1846 1. tentacles solid, scattered under long hypostome; Hydroid: solitary fresh-water hydroids, with hol- tentacles with cnidocysts in a terminal knob and low filiform tentacles, but often moniliform distally, several adaxial knobs ...... Odessia

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– Tentacles hollow, in one whorl or scattered; Moerisia carine Bouillon, 1978 tentacles moniliform ...... Moerisia (Fig. 46A)

Key to medusae Medusa: umbrella 2,6 mm wide and 3,3 mm high, bell-shaped with rounded apex; mesoglea 1. Radial lobes of manubrium twisted; “gonads” very thick and consistent, mainly at apex, thinning lobed ...... Halmomises towards umbrella margin; manubrium small, quad- – Radial lobes of manubrium not twisted; rangular, with 4 short perradial manubrial lobes, “gonads” smooth ...... 2 not overrunning the subumbrellar roof; mouth cru- 2. Marginal tentacles moniliform; “gonads” on ciform, with four small lips, covered with cnido- manubrium continuous with those on manubrium cysts; «gonads» covering manubrium and extend- lobes ...... Moerisia ing on manubrial lobes; up to 16 marginal monili- – Marginal tentacles with irregularly transverse form tentacles of different size; marginal bulbs cnidocyst claps or bands; “gonads” on large, globular, clasping exumbrella each with a manubrium, usually separated from those on large ocelli. manubrial lobes in adults ...... Odessia Records from Mediterranean: eastern Mediter- ranean. Genus Halmomises von Kennel, 1891 Known seasonality: 7 -12. (unrecognisable) Distribution: Indo-pacific; Mediterranean. References: Bouillon (1978b); Lakkis and Zei- Genus Moerisia Boulenger, 1908 dane (1985); Goy et al. (1988, 1990, 1991) Boero = Ostroumovia Hadzi, 1928 and Bouillon (1993). Hydroid: unknown. Hydroid: with the general characters of the fami- ly, tentacles moniliform. Moerisia inkermanica Medusa: either 4 or 16-32 moniliform marginal Paltschikowa-Ostroumova, 1925 tentacles; no centripetal canals; “gonads” on (Figs. 46B-D) manubrium, interradial, continuous with those on manubrial lobes. Hydroid: hydranth attached to substratum by one Reference: Petersen (1990). or more perisarcal pedal disks (podocysts) issued from stolon-like tubes, tubes often reduced to merely Key to hydroids filaments, the hydranths may be solitary with a single pedal disk at base or even bipolar; perisarc delicate, 1. Hydranth attached to substratum by one or more gelatinous with adhering silt, covering stolon-tube pedal disc (podocysts)...... M. inkermanica and basal part of hydranth body; hydranth spindle- – Hydranth without podocysts; colony giving up shaped, slender at base and widening to tentacular hydrocauli...... M. lyonsi region, with 4-12 hollow moniliform tentacles in one or two roughly alternating whorls; asexual reproduc- Key to medusae tion: by medusa buds arising just under or amongst tentacles, by lateral hydranth buds arising just below 1. With marginal tentacles of different lengths.... 2 tentacles (the budding hydranths may remain attached – With usually only 4 marginal tentacles of about to the stolonal system of the parent), by stolonization equal length (exceptionally up to 16 or 22); from base, by podocysts. mouth with no lips...... M. lyonsi Medusa: Umbrella up to 6.5 mm wide, 5.5 mm 2. Manubrium with very short manubrial pouches, high, dome shaped, mesoglea very thick; manubri- up to 16 marginal tentacles, marginal tentacular um small, cruciform, with long perradial manubrial bulbs globular, mouth with distinct lips...... lobes extending nearly to bell margin; mouth with ...... M. carine cnidocyst perradial thickening, no real lips; with – Manubrium with long manubrial pouches, up to «gonads» on manubrium continuous with those on 36 marginal tentacles, proximal parts of tentacles radial lobes, with distal portions often sac-like, pen- narrow, mouth with no distinct lips...... dent; up to 32 moniliform marginal tentacles of dif- ...... M. inkermanica ferent lengths, proximal part of tentacle narrow,

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largely adnate to exumbrella; with carmine ocelli at one large terminal knob of cnidocysts and several the point of issue of the free parts of tentacles. adaxial knobs; with free medusae. Records from Mediterranean: fresh water bodies Medusa: Moerisiidae with «gonads» on perradial of eastern and western Mediterranean; Azov Sea; side of manubrium usually separated from those on Black Sea. manubrium walls in adults; without centripetal Known seasonality: 6-9. canals; 16-32 marginal tentacles with cnidocysts in Distribution: Atlantic; Indo-Pacific; Mediter- irregular transverse claps or bands. ranean. References: Valkanov (1935, 1938, 1953); Odessia maeotica (Ostroumoff, 1896) Kramp (1938a, b, 1961); Paspaleff (1938); Kramp (Fig. 46H-I) (1942); Picard (1951a, 1955a); Bouillon et al, (1969); Brinckmann-Voss (1987); Boero and Bouil- Hydroid: hydranths usually solitary, conical, lon (1993). tapering basally, with a long conical hypostome; with numerous solid tentacles scattered under Moerisia lyonsi Boulenger, 1908 hypostome, each with one large terminal knob of (Figs. 46E-G) cnidocysts and several adaxial knobs; pedal disc enclosed in perisarc, with polyp buds arising under Hydroid: small colonies with short branched tentacles and which may remain attached to parent hydrorhiza of stolon-like tubes, the free ends of polyp during a certain time forming temporarily which narrowing to form the hydrocauli, stolon colonies; medusa buds arising between and under tubes recovered with annulated, delicate perisarc the tentacles. incrusted with detritus; extremity of hydrocauli and Medusa: umbrella up to 18 mm wide, usually hydranths naked; hydrocaulus gradually merging much smaller, about as wide than high or somewhat into the hydranths which are claviform, with a lower, bell-shaped, mesoglea thick; perradial lobes rounded elongated hypostome, with about 4- 8 hol- of manubrium extending along proximal half or low long moniliform tentacles in one whorl; asexu- more of radial canals; in adult medusae the al reproduction: by medusa buds developing both «gonads» on the interradial walls of manubrium are above and below the circlet of tentacles, by lateral separated from those on the radial canals; 16-32 budding below the tentacles area of frustules and marginal tentacles with cnidocysts in irregularly polyps (which become free), by multiple constric- transverse claps or bands, not in moliniform rings, tion and transverse fission of the basal part of the marginal bulbs globular to elongated adnate to hydranths, by hydranth budding from hydrocauli, by exumbrella. podocyst borne on short solon-like tubes. Records from Mediterranean: Black Sea, Azov Medusa: umbrella 4.5 mm wide and 4 mm high, Sea; eastern and western Mediterranean; Adriatic. globular, mesoglea very thick, mainly at apex; Known seasonality: 4; 7-10. manubrium cylindrical; mouth round, without lips; Distribution: Atlantic; Mediterranean. perradial lobes of manubrium about 2/3 of the length References: Picard (1951a, 1952, 1955a); Rees of the radial canals; «gonads» interradial on (1958); Kramp (1961); Sacchi (1961); Goy (1973b); manubrium walls in continuity with those on Petersen (1990); Boero and Bouillon (1993) Avian manubrial lobes; marginal tentacles moniliform, et al. (1995). usually four, but sometimes 16, rarely 22, long, with prominent rings of cnidocyst. Family PROTOHYDRIDAE Allman, 1888 Records from Mediterranean: Lake Qurum, Egypt. Known seasonality: 3-5. Hydroid: paedomorphic, usually living in brack- Distribution: Atlantic, Mediterranean. ish-waters; hydranth solitary, spindle-shaped, with- References: Boulenger (1908); Picard (1951a); out tentacles but with scattered cnidocyst warts, Kramp (1961). moving as caterpillars; ectodermal pedal disc; sexu- al products differentiated in endoderm, reproductive Genus Odessia Paspaleff, 1937 cycle unknown, asexual reproduction by transverse fission. Hydroid: with the general characters of the fami- Remark: often classified near the Hydridae, ly; tentacles scattered under hypostome, each with based on assumptions and convenience more than

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facts. Phylogenetic position uncertain; here tenta- mouth simple, round or cruciform; in non mature tively incorporated into the Moerisiida. specimens “gonads” interradial, apparently divided in adradial masses by longitudinal median grooves, Genus Protohydra Greef, 1869 “gonads” confluent in perradii in adult specimens; 4 hollow, marginal tentacles with either adaxial or spi- With the characters of the family rally-arranged cnidocyst clusters and terminating in an References: Thiel (1988); Petersen (1990). ellipsoid capitation; marginal bulbs large, clasping exumbrella, with an adaxial expansion; abaxial ocelli. Protohydra leuckarti Greeff, 1869 References: Wedler and Larson (1986); Calder (Fig. 47A-E) (1988); Petersen (1990); Bouillon and Boero (2000).

With the characters of the family. Genus Sphaerocoryne Pictet, 1893 Records from Mediterranean: western Mediter- = Linvillea Mayer, 1910 ranean (Canet Plage) Seasonality: ? Hydroid: colony stolonal; hydrocaulus long, sim- Distribution: Cosmopolitan. ple or slightly branched; hydranth vasiform, with References: Delamare-Deboutteville (1960), numerous simple solid capitate tentacles in 3-5 Clausen (1971). whorls around broadest part; gonophores on short branching blastostyles above or among tentacles. Suborder SPHAEROCORYNIDA Medusa: with the characters of the family. Petersen (1990) Sphaerocoryne bedoti Pictet, 1893 Hydroid: where known, hydrorhiza either stolon- (Fig. 47F-G) al, or mat-like, forming a basal plate hydrorhiza; numerous long capitate tentacles arranged in 3-6 Hydroid: colonies with creeping hydrorhiza usu- irregular aboral whorls around middle part of ally embedded in sponges; hydrocaulus monosi- hydranth column, or in 1 or 5-6 close alternate oral phonic, unbranched, covered by a delicate perisarc whorls surrounding hypostome; gonophores borne and giving rise to solitary hydranth; perisarc smooth on middle part of body, or on basal part of hydro- or with a few wrinkles or annulations; hydranth caulus, or on hydrorhiza. pyriform to bottle-shaped with 15-70 solid capitate Medusa: manubrium flask-shaped, quadrate or tentacles of varying length arranged in 2-6 closely cruciform in cross-section; “gonads” interrardial, alternating whorls in the broadest basal part of the adradial or circular; 2-4 perradial marginal capitate hydranth; hypostome elongated, conical; no oral tentacles. tentacles; medusa buds borne on clusters (up to 12) References: Petersen (1990); Bouillon and Boero just above tentacles, each cluster may bear more (2000). than 10 medusa buds. Cnidocysts: desmonemes, Only one family in Mediterranean: small stenoteles, large stenoteles. Medusa: umbrella bell-shaped to ovoid, up to 4,5 Family SPHAEROCORYNIDAE Prévot, 1959 mm high and 3.0 mm wide; with a conical or dome- shaped apical projection and a broad apical cham- Hydroid: colony stolonal or erect; hydrorhiza ber; manubrium simple, flask-shaped, with quadrate creeping; hydrocaulus long, unbranched or slightly base, two third of umbrella cavity in length; mouth branched, with a terminal hydranth; perisarc thin, tube rather long, with simple rounded or more or reaching hydranth base; hydranth vasiform with bul- less cruciform opening; with four simple radial bous base, and proboscis; no oral tentacles but canal; with 4 marginal tentacles bearing spirally numerous solid, single or trifid capitate tentacles in arranged clusters of cnidocysts and a hollow, ellip- 3-5 whorls around broadest part of column; soid, terminal cnidocyst knob; four marginal bulbs gonophores as free medusae or as eumedusoids. large, clasping exumbrella, with an adaxial expan- Medusa: umbrella bell-shaped, ovoid; apical sion, each bulb with a abaxial ocelli, «gonads» inter- mesoglea thick, apical projection conical or dome- radial with a longitudinal median groove which may shaped, apical chamber broad; manubrium with divide them in adradial masses, adult medusae with quadrate base, either flask-shaped, or cruciform; «gonads» confluent in perradii.

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Records from Mediterranean: eastern Mediter- 6. One whorl of reduced tentacles, capitate or not, ranean. located in the oral or median part of the hydranth Seasonality:? ...... Boreohydridae Distribution: Atlantic; Indo-pacific; Mediter- – Hydranth with several tentacle whorls...... 7 ranean. 7. Hydrocaulus thin, with conspicuous inflated References: Prévot (1959); Kramp (1961); Mam- gelatinous periderm; oral whorl of capitate men (1963); Yamada and Kommo (1973); Millard tentacles and 2 aboral whorls of moniliform (1975); Bouillon (1984c); Hirohito (1988); Petersen tentacles ...... Tricyclusidae (1990); Goy et al. (1991); Boero and Bouillon – Hydrocaulus not surrounded by an inflated (1993). gelatinous periderm...... 8 8. One or two whorls of oral capitate tentacles, and Suborder TUBULARIIDA Fleming, 1828 a distal aboral whorl of large fleshy filiform tentacles...... Acaulidae Hydroid: hydranth with solid or parenchymatical – Oral whorl of short moniliform, capitate or oral tentacles in one whorl around hypostome or filiform tentacles; moniliform or filiform aboral spreading down over hydranth body; with solid or tentacles in 1 or 3 close-set whorls, or dispersed; parenchymatical aboral tentacles in one or three often with aboral endodermal statocyst-like whorls or absent; free medusae or sporosacs. structure and adhesive mucus organ ...... Medusa: manubrium generally cylindrical, with ...... Euphysidae circular base; mouth usually simple and circular; 9. Colony polymorphic...... Paracorynidae “gonads” normally completely surrounding – Colony monomorphic...... 10 manubrium; marginal tentacles developed only at 10.Colony pinnate (feather-like) ...... Pennariidae junction between radial canals and circular canal; – Colony not pinnate ...... 11 usually with 1 to 4 marginal tentacles, rarely 8 or 11.One whorl of oral capitate tentacles and usually more in the Cladonematidae. below it more capitate tentacles in whorls or References: Hirohito (1988); Petersen (1990). scattered; there may be filiform tentacles below capitate ones; hypostome with or without distinct Key to hydroids button of mucous gland cells around mouth...... Corynidae 1. Solitary ...... 2 – Only one oral whorl of capitate tentacles, – Colonial ...... 9 sometimes one aboral whorl of filiform sensory 2. Pelagic...... Margelopsidae tentacles; with glandular mucous cells forming a – Not pelagic ...... 3 preoral cavity around the mouth ...... 3. Hydrocaulus with parenchymatic endoderm ...... Cladonematidae often with peripheral canals ...... 4 – Hydrocaulus without these characters...... 5 Key to medusae 4. Hydranth with one whorl of moniliform or capitate oral tentacles or several whorls of fili 1. Reduced medusae, with 4 rudimentary bulbs ..... form oral tentacles; with one to three whorls of ...... Pennariidae moniliform or filiform aboral tentacles; perisarc – Medusae not reduced, exceptionally without usually feebly developed, restricted to base of tentacles...... 2 hydrocaulus ...... Corymorphidae 2. Marginal tentacles simple; with 1-4 marginal – Hydranth with capitate, moniliform, filiform or tentacles...... 3 pseudofiliform oral tentacles, in one to several – Marginal tentacles branched; usually with more close-set whorls; one whorl of long pseudo- than 4 radial canals...... Cladonematidae* filiform or filiform aboral tentacles; perisac well 3. Marginal tentacular bulbs with ocelli...... developed reaching hydranth base, forming a ...... Corynidae neck region...... Tubulariidae – Marginal tentacular bulbs without ocelli ...... 4 5. Tentacles capitate or not, disposed in distinct 4. Exumbrella without cnidocyst tracks...... 5 whorls ...... 6 – Exumbrella with cnidocyst tracks.. Tubulariidae – Numerous scattered capitate tentacles ...... 5. With 1-4 marginal tentacles, unequally ...... Candelabriidae developed or of the same length but all of same

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structure; without apical projection...... mucous secretion. Tentacles capitate 10-25, without ...... Euphysidae filiform tentacles. Oral tentacles 4-6 around hypos- – With up to four marginal tentacles of different tome, the remainders scattered over the body. size and structure; umbrella dome-shaped or with Cnidocysts: stenoteles, desmonemes and holotric- pointed apex ...... Corymorphidae hous microbasic mastigophores. Record from Mediterraneum: western Mediter- Remark: *The Cladonematidae are often separat- annean. ed in two families: the Cladonematidae and the Distribution: northeastern Atlantic, Mediter- Eleutheriidae ranean. References: Bouillon (1965, 1971); Thiel (1988). Family ACAULIDAE Fraser, 1924 Acauloides ilonae (Brinckmann-Voss, 1966) Hydroid: hydranth solitary, pear-shaped, with 1 (Fig. 47I) or 2 whorls of oral capitate tentacles, and with a distal aboral whorl of large fleshy filiform tenta- Hydroid: solitary polyps with gelatinous tube, cles, which may be absent or replaced by capitate which may elongate and serve as anchoring fila- tentacles; attached to substrate by a reduced hydro- ment. Tentacles numerous, up to 69 or more. One caulus (= “root” or “peduncle”), by means of a whorl of short oral tentacles and one whorl of long gelatinous fixation tube, or by anchoring filaments, aboral tentacles. Between these two whorls are a or by a mucous secretion; gonophores as fixed large number of scattered tentacles, which increase sporosacs in the lower or middle part of the in length towards the aboral region. All tentacles hydranth, asexual reproduction by transverse fis- capitate. Fixed gonophores in the axils of the tenta- sion in some species. cles. Cnidocysts: desmonemes; stenoteles and References: Petersen (1990); Thomas et al. microbasic euryteles. (1995); Schuchert (2001a). Records from Mediterranean: western Mediter- ranean. Genus Acauloides Bouillon, 1965 Known seasonality: 1-6, 11-12. Distribution: northeastern Atlantic, Mediter- Hydrocaulus attached to substrate by a modified ranean. basal part, secreting a gelatinous sheath or forming References: Brickmann-Voss (1966, 1970); anchoring filaments or by an adhesive basal disc; Boero and Bouillon (1993). hydranth pear-shaped, one oral whorl of capitate tentacles and scattered aboral capitate tentacles of Family BOREOHYDRIDAE Westblad, 1947 irregular length, all with choral endoderm; gonophores in axils of scattered tentacles, asexual Hydroid solitary of small size, hydranths with reproduction through transverse fission. one whorl of reduced tentacles, capitate or not, References: Thiel (1988); Petersen (1990); located in the oral or median part of the hydranth; Thomas et al. (1995); Schuchert (2001a). perisarc reduced or absent. Gonophores where known as fixed sporosacs. 1. Hydrocaulus short, without gelatinous tube; hydranth with up to 25 tentacles ...... 1. Hydranth with oral capitate tentacles and ...... A. ammisatum cnidocysts warts; hypostome normal ...... – Hydrocaulus elongated, covered with a ...... Boreohydra gelatinous tube; hydranth with up to 69 tentacles – Hydranth with capitate tentacles in the middle of or more...... A. ilonae. the body; hypostome extensible; one of the smallest hydrozoa known...... Psammohydra Acauloides ammisatum (Bouillon, 1965) (Fig. 47H) Genus Boreohydra Westblad, 1937

Solitary polyps (0.6-2 mm) with a short pedun- Hydroid: hydrocaulus covered by a detritus cle, without gelatinous tube neither anchoring fila- agglutinated sheath which may bear rhizoids; ments, but attached to substrate by means of a hydranth club-shaped, with one oral whorl of 3 to 4

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short capitate tentacles and numerous cnidocyst hydranth elongated, cylindrical, with thickened warts; gonophores as fixed sporosacs, resembling mesoglea and endodermal villi; numerous scattered, cryptomedusoids, which may be developing asexual hollow capitate tentacles, simple or compound; polyp buds seated singly on lower part of hydranth; gonophores fixed, developing directly on hydranth eggs occurring singly in ectoderm at border between or on coryniform blatostyles from aboral part of hydranth and hydrocaulus, asexual reproduction hydranth, under body tentacles. through transverse fission. References: Petersen (1990); Stepanjants et al., (1990); Segonzac and Vervoort (1995); Schuchert Boreohydra simplex Westblad, 1937 (1996, 2001a). (Fig. 47J) Genus Candelabrum de Blainville, 1830 See definition of the genus. = Myriothela Sars, 1851 Records from Mediterranean: Adriatic? Seasonality: ? Hydranth solitary, long, cylindrical with numer- Distribution: Bipolar Atlantic, Mediterranean? ous densely packed, simple capitate tentacles; References: Thiel (1988); Petersen (1990) ; hydrocaulus plate- or tuber-like, with adhesive Schuchert (2001a) processes that end in discs covered by firm, lamellar perisarc; gonophores as fixed sporosacs borne on Genus Psammohydra Schulz, 1950 coryniform blastostyles developed from aboral part of hydranth; fertilized eggs borne on special tenta- Solitary mesopsammic hydroids with 3 to 5 non cle-like claspers situated among blastostyles arising capitate tentacles in one circlet in the middle of the below the area of body tentacles; reproduction by body; with adherent elements around its extensile actinula larvae. mouth used during caterpillar-like movements. Sex- References: Petersen (1990); Segonzac and Ver- ual reproduction unknown, asexual reproduction by voort (1995); Schuchert (1996), Watson (1997). fission. Remarks: Psammohydra has been seldom Candelabrum cocksii (Vigurs, 1850) observed, it is one of the smallest known hydroid, (Fig. 48A) measuring 250 to 400 µm; sometimes considered as incertae sedis it is here included in the Boreome- Hydranth 1-2 cm long, composed of foot, blas- dusae because its cnidome (desmonemes, atrichous tostyle region and trunk (distal part of the body). isorhizas and stenoteles) and its unique row of ten- Foot large, only slightly shorter than blastostyle tacles (Bouillon, 1985). region, with a number of slender prolongations that attach body to substrate, basis of each prolon- Psammohydra nanna Schulz, 1950 gation with chitinous perisarcal disk; chitinous (Fig. 47K) perisarc gradually extending upwards and cover- ing whole foot, externally more or less spinous. See definition of the genus. Monoecious, blastostyles slender, with male and Records from Mediterranean: western Mediter- female gonophores and with some developing ranean and Adriatic. eggs attached by claspers (feeding tentacles); dis- Seasonality: ? persed capitate tentacles also occur on blas- Distribution: western Baltic, northeastern tostyles. There is no terminal circle of tentacles. Atlantic, Mediterranean. Cnidocysts: large and small desmonemes and References: Schulz (1950); Clausen and Salvini- stenoteles. Plawen (1986); Thiel (1988); Petersen (1990); Records from Mediterranean: no records but in Avian et al. (1995). the area of the Bay of Cádiz (south Spain). Seasonality: ? Family CANDELABRIDAE de Blainville, 1830 Distribution: north-eastern Atlantic, Mediter- ranean?. Hydroid: solitary or forming pseudo-colonies; References: Bedot (1911); Rees (1957); Manton hydrocaulus short, stout, with tubular or root-like (1940); Segonzac and Vervoort (1995); Medel adhesive processes, with or without perisarc; (1996); Medel and López-González (1996).

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Family CLADONEMATIDAE Gegenbaur, 1857 Genus Cladonema Dujardin, 1843

Hydroid: colonial, stolonal or erect, with creep- Hydroid: with the characters of the family; with ing stolons; stem unbranched or sparingly branched; mostly stolonal colony; hydrocaulus occasionally hydranth spindle-shaped, one whorl of 4-5 solid oral branching, medusa buds borne singly on hydranth capitate tentacles, with or without aboral whorl of body. sensory filiform tentacles; mouth with oral ectoder- Medusa: creeping and swimming; manubrium mal mucous gland cells forming a preoral chamber; cylindrical, with perradial pouches; mouth with medusa buds not enclosed in perisarcal film, carried short lips armed with 4 to 6 cnidocyst clusters; no singly or in clusters at base of hydranth, distal to apical chamber above manubrium; variable number aboral tentacles, when these are present. of radial canals, some branched, some simple, final Medusa: able to walk and/or swim; with or number of canals entering circular canal usually of without a thickened continuous or broken ring of same number as marginal tentacles; “gonads” com- cnidocysts around umbrellar margin, with or with- pletely surrounding manubrium; variable number of out apical chamber above manubrium; manubrium hollow branching marginal tentacles, each with 1 to cylindrical, with or without perradial pouches; 6 branches ending in an organ of adhesion and 1 to mouth either with short lips, armed or not with 10 branches with clusters of cnidocysts; with ocelli. cnidocyst clusters, or with ramified oral tentacles; References: Petersen (1990); Wedler and Larson with variable number of radial canals, some (1986); Calder (1988); Schuchert (1996); Bouillon branched, some simple, final number of canals (1995a; 1999); Bouillon and Barnett (1999); Bouil- entering circular canal usually corresponding to, lon and Boero (2000); Schierwater and Ender or exceptionally exceeding, the number of margin- (2000). al tentacles; marginal tentacles hollow, with some capitate branches and some adhesive branches; Cladonema radiatum Dujardin, 1843 “gonads” either completely surrounding manubri- (Fig. 48B-D) um, on subumbrella, or in special brooding pouch- es; with abaxial ocelli. Hydroid: slender, simple or slightly branching References: Wedler and Larson (1986); Calder colonies arising from creeping ramified stolons; (1988); Migotto (1996); Schuchert (1996); Bouillon perisarc smooth terminating shortly below hydranth; (1999); Bouillon and Barnett (1999); Bouillon and hydrocaulus with terminal hydranths; hydranths Boero (2000); Schierwater and Ender (2000). clavate, with a rounded hypostome, with an oral whorl of 4-5 capitate tentacles and a basal whorl of Key to hydroids 4-5 aboral filiform tentacles alternating with capi- tate tentacles and with a slight terminal swelling; 1. Medusa buds in clusters or on short blastostyles apical ectoderm of hypostome presenting a well at hydranth base; no aboral tentacles ...... developed glandular peri-oral cavity; medusa buds ...... Eleutheria borne naked, singly on hydranth just above filiform – Medusa buds borne singly on hydranth body, tentacles. immediately above aboral tentacles, or in same Medusa: umbrella when full grown about 4 mm position when those are absent...... high, 3 mm wide, bell-shaped, slightly higher than ...... Cladonema and Staurocladia broad, mesoglea moderately thin, sometimes with a slight apical projection; velum rather broad; Key to medusae manubrium spindle-shaped, not extending beyond umbrella margin, with usually five, sometimes four, 1. Bell high; marginal tentacles branching more perradial pouch-like outgrowths in its middle than once...... Cladonema region; mouth with usually five, sometimes four, – Bell flat; marginal tentacles branching only once short protuberances or lobes, each armed with ...... 2 cnidocyst clusters; usually five, sometimes four, thin 2. One cnidocyst knob on upper tentacular primary radial canals some of which bifurcate to branches...... Eleutheria form ten, sometimes eight, radial canals in all; cir- – More than one cnidocyst knob on upper cular canal narrow; «gonads» on the upper two- tentacular branches ...... Staurocladia thirds of manubrium and on the perradial pouches;

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usually ten, sometimes eight, marginal tentacles, flatter than hemispherical; with a thick marginal corresponding to the number of radial canals; mar- cnidocyst ring; manubrium cylindrical to conical ginal tentacles branched, with elongated thickened extending slightly beyond umbrella margin, with 4- bases from the under side of which grow one to four 6 radial canals; «gonads» in specialized umbrellar (up to10) short tentacles with adhesive organs; the brood pouches situated above manubrium; medusa branched upper portions of the marginal tentacles buds from subumbrellar side of ring canal into are beset with numerous cnidocyst clusters; with a umbrella cavity; 8-10 solid marginal tentacles not black or deep crimson abaxial ocellus at the base of corresponding to the radial canals; marginal tenta- each marginal tentacle; colour of manubrium and cles bifurcate, one branch with adhesive disk, the marginal tentacles red, bright-red or brown. other with a cnidocyst knob; one abaxial ocelli on Records from Mediterranean: eastern and west- each tentacular base. ern Mediterranean; Adriatic Sea; Black Sea. Records from Mediterranean: western Mediter- Known seasonality: 5-8. ranean. Distribution: Atlantic; Indo-Pacific; Mediter- Known seasonality: 6. ranean. Distribution: Atlantic; Mediterranean. References: Allman (1872); Kramp (1961); References: Kramp (1961); Brinckmann-Voss Bouillon (1966, 1968b); Berhaut (1970); Bodo (1970); Boero and Bouillon (1993). (1970); Bouillon and Houvenhaghel (1970); Brinck- mann-Voss (1970; 1987); Goy (1973b); Bouillon Eleutheria dichotoma Quatrefages, 1842 and Nielsen (1974); Calder (1988); Boero and (Figs. 48G-H) Bouillon (1993); Avian et al. (1995); Benovic and Lucic (1996); Medel and López-González (1996). Hydroid: colonies small, with a creeping hydrorhiza, unbranched or slightly branched; peris- Genus Eleutheria Quatrefages, 1842 arc smooth delicate, extending to base of hydranth; hydranth sessile or with rudimental hydrocaulus, Hydroid: with the characters of the family, but solitary; cylindrical, very extensile, with large with oral tentacles only and medusa buds borne in rounded-conical hypostome; with a oral whorl of up clusters or on short blastostyles at base of hydranth. to 10 capitate tentacles; apical endoderm of hypos- Medusa: umbrellar margin with a thickened tome presenting a glandular peri-oral cavity; cnidocyst ring; with brood pouch above manubrium; medusa buds naked borne in clusters or on short manubrium simple; mouth, simple circular; stalks near base of the hydranth. “gonads” reduced, hermaphroditic; tentacles bifur- Medusa: umbrella 0.3 mm high, 0.5 mm wide, cated, lower branch with adhesive disk, upper flatter than hemispherical; with a thick marginal branch with only one terminal cnidocyst cluster; cnidocyst ring; manubrium cylindrical to conical asexual reproduction by budding from circular canal extending slightly beyond umbrella margin; with either from subumbrellar side (E. claparedei)or usually six radial canals; «gonads» in specialised from exumbrellar side (E. dichotoma); with ocelli. umbrellar brood pouches situated above manubri- um; medusa buds on exumbrellar side of circular 1. 6 radial canals, 5-14 marginal tentacles; medusa- canal; up to 14 solid marginal tentacles, usually 5-6, buds exumbrellar; brood pouch present ...... not corresponding to the radial canals; tentacles ...... E. dichotoma bifurcated, lower, unarmed, branch with an adhesive – 4-6 radial canals, 8-10 marginal tentacles; disk, the upper with a single cnidocyst knob; one medusa-buds subumbrellar; brood pouch absent abaxial ocelli on each tentacular base...... E. claparedei Records from Mediterranean: eastern and west- ern Mediterranean; Adriatic Sea; Black Sea. Eleutheria claparedei Hartlaub, 1889 Known seasonality: 3-10. (Figs. 48E-F) Distribution: Atlantic; Mediterranean. References: Kramp (1961); Brinckmann-Voss Hydroid: similar to E. dichotoma polyp, see (1970, 1987); Goy (1973b); Bouillon (1966, 1968 a, below, seldom founded in field and mainly known b); Boero and Bouillon (1993); Avian et al. (1995); from polyps raised from planulae. Benovic and Lucic (1996); Medel and López- Medusa: umbrella 0.4 mm high, 0.5 mm wide; González (1996).

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Genus Staurocladia Hartlaub, 1917 them, two to four knobs on its oral side; the lower tentacular branch terminates in a adhesive sucker- Hydroid: hydranths with an oral whorl of capi- like organ; the «gonads» surrounding completely tate tentacles and with or without aboral filiform the manubrium and manubrial pouches; each ten- tentacles. tacles with an abaxial ocelli. Medusa: Cladonematidae adapted for crawling Records from Mediterranean: western Mediter- and walking; without brood pouch above ranean. manubrium; «gonads» around manubrium or Known seasonality: 5-7. developed in ectodermal manubrial pockets; with Distribution: endemic of Mediterranean Sea. 6-11 radial canals some bifurcating shortly distal References: Brinckmann (1964a); Brinckmann- to manubrium; mouth circular with or without Voss (1970); Bouillon (1966, 1978a); Boero and cnidocysts knobs; with up to 60 marginal tenta- Bouillon (1993). cles, dichotomous, upper branch with several cnidocyst clusters, lower with adhesive organ; Family CORIMORPHIDAE Allman, 1872 with ocelli; often asexual reproduction by medusa budding or by fission. Hydroid: solitary, hydrocaulus long, distally pointed or rounded, hollow or more or less filled by Staurocladia portmanni Brinckmann, 1964a parenchymatic endoderm; lower part with short (Figs. 48I-J) papillae or/and longer anchoring didermic fila- ments; either with one whorl of moniliform or capi- Hydroid: small stolonal colonies covered with tate oral tentacles or several whorls of filiform oral perisarc extending till base of the hydranths; tentacles; one to 3 whorls of moniliform or filiform hydranths borne on short non branching hydrocauli aboral tentacles; gonophores as free medusae or arising directly from hydrorhiza; hydranths spindle fixed sporosacs. shaped to cylindrical, with rounded-conical hypos- Medusa: dome shaped or with pointed apex; tome, with 3-4 oral capitate tentacles and an aboral manubrium not extending beyond umbrella margin whorl of always six filiform tentacles; apical ecto- (except in Yakovia but this is presumably an artifact derm of hypostome presenting a well developed due to fixation), sausage-shaped or exceptionally glandular peri-oral cavity; medusa buds naked, one with sac-like processes; mouth, simple circular; 1- 4 or more seldom two just above aboral tentacles. capitate or moniliform marginal tentacles, of differ- Medusa: umbrella up to 4-6 mm wide, and 2.5- ent size and structure, exceptionally branched, and 5 mm high; flat bell-shaped; with a thick cnido- rudimentary tentacles; “gonads” undivided sur- cyst ring on the margin of exumbrella; manubri- rounding all length of manubrium and exceptionally um pear-shaped almost filling subumbrellar cavi- also in sac-like processes of manubrium (Gotoea). ty, with 5 interradial manubrial pouches, manubri- References: Kramp (1949); Calder (1988); um not extending beyond subumbrellar margin; Petersen (1990); Pagès, Gili and Bouillon (1992); mouth with five lip-like protuberances armed Schuchert (1996); Bouillon (1999); Bouillon and with cnidocysts; five radial canals originating Barnett (1999); Bouillon and Boero (2000). near the upper centre of manubrium and remain- ing attached to its roof for some distance, gener- Key to hydroids ally bifurcating when becoming free so that up to 10 radial canals are joining the circular canal; 1. Hydranth bilaterally symmetrical, with two sets proximal part of radial canals giving off endoder- of filiform tentacles, gonophores as fixed mal finger-like expansions to exumbrella; with up sporosacs...... Branchiocerianthus to 25 marginal tentacles bifurcating at some dis- – Hydranth radially symmetrical...... 2 tance of origin in an upper (aboral) and a lower 2. Hydranth with filiform tentacles only...... (oral) branch; the main stem of the tentacles bear ...... Corymorpha two opposite lateral cnidocyst knobs immediately – Hydranth with all tentacles not filiform...... 3 proximally to the ramification of the tentacles, 3. Hydranth with numerous oral capitate tentacles upper branch ending in a terminal cluster of in irregular whorls...... Euphysora cnidocysts and bearing two to five cnidocyst – Hydranth with moniliform oral tentacles ...... knobs on its aboral side and alternating with ...... Vannucia

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Key to medusa Known seasonality: 3. Distribution: endemic of Mediterranean Sea. 1. With only 1 marginal tentacle ...... 2 References: Lo Bianco (1909); Brattström – With 3 short or rudimentary marginal tentacles (1957); Brinckmann-Voss (1970). and 1 long principal marginal tentacles different in structure ...... Euphysora Genus Corymorpha M. Sars, 1835 = Amalthaea 2. Exumbrella divided 4 prominent leaf-shaped Schmidt, 1852 facets separated by 4 longitudinal large and deep grooves...... Eugotea Hydroid: hydrocaulus with thin perisarc, – Exumbrella with uniform surface ...... 3 parenchymatic endoderm with longitudinal periph- 3. Umbrella margin slightly oblique to vertical axis, eral canals; lower part with short papillae or/and umbrella with no apical process; principal long anchoring didermic filaments; hydranth vasi- marginal tentacle, short and thick, ending in long form with one or several closely set whorls of oral and large, oval, ectodermal swelling containing filiform tentacles, and one whorl of aboral filiform numerous cnidocysts...... Vannuccia. tentacles; parenchymatic diaphragm; free medusae – Umbrella margin at right angles to vertical axis, or fixed gonophores. principal marginal tentacles different...... 4 Medusa: dome-shaped or with pointed apical 4. Principal marginal tentacle, slender, long, process, usually with apical canal; one long monili- moniliform; umbrella with pointed apical form tentacle and 3 non tentacular rudimentary process...... Corymorpha bulbs. – Principal marginal tentacle with one large terminal cnidocysts knob; umbrella without Corymorpha nutans M. Sars, 1835 pointed apical process ...... Paragotoea (Fig. 49A-C)

Genus Branchiocerianthus Mark, 1898 Hydroid: large solitary hydroid, hydrocaulus subcylindrical, somewhat narrowed upwards and Hydroid: paedomorphic hydrozoa reduced to downwards, basal end with short sensorial papillary hydroid stage, hydranth in some species very large projections and lower down numerous elongated over 2 m, bilaterally symmetrical and eccentrically rooting, anchoring, filaments; hydrocaulus filled seated on hydrocaulus; with several whorls of filifom with parenchymatic endoderm with numerous longi- oral tentacles and one whorl of filiform aboral tenta- tudinal anastomising peripheral canals; perisarc a cles, with a thin diaphragm dividing gastric cavity transparent membranous tube; hydranth flask- into oral and aboral chambers; oral chamber with shaped to vasiform with about 20 to 80 oral filiform unbranched radial canals between blastostyles and contractile tentacles arranged in several irregular aboral tentacles; hydrocaulus long, with parenchy- whorls, and 20 to 32 aboral much longer, uncontrac- matic endoderm with longitudinal canals, rooted by til filiform tentacles; hydranth and distal part of anchoring filaments; perisarc rudimentary. hydrocaulus bend downwards; medusa buds borne Gonophores as fixed sporosacs borne on blastostyles in dense clusters on about 15-20 branching pedun- arising immediately above the aboral tentacles. cles just above aboral tentacles; asexual reproduc- References: Brinckmann-Voss (1970); Petersen tion by constriction of the hydrocaulus aboral end. (1990). Medusa: umbrella up to 6 mm high (including apical process), about twice as high than wide, with Branchiocerianthus italicus Stechow, 1921 a high, pointed apical process and a long, narrow umbilical canal, mesoglea thick; velum fairly wide; Only one specimen found by Lo Bianco in 1909, manubrium large, cylindrical, on short gastric who did not describe it or gave a name, citing only peduncle, about 2/3 of the length of subumbrella, in it was 10 cm high and had numerous tentacles. The full extension reaching slightly beyond exumbrellar name italicus was latter on suggested by Stechow margin; mouth simple, tube-like armed with cnido- (1921a, 1923d) for this unique specimen but without cysts; 4 radial canals and circular canal fairly broad; any further description or diagnoses. «gonads» completely surrounding manubrium but Records from Mediterranean: western Mediter- living peduncle and mouth free; one single long ranean, gulf of Naples. marginal tentacle, moniliform; 3 perradial non ten-

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tacular bulbs smaller than the tentacular one; with rootlets; hydranth vasiform, with 35 oral tentacles resting eggs. set in irregular rows on hypostome, more or less dis- Records from Mediterranean: western Mediter- tinctly capitate, with scattered cnidocyst batteries; ranean, Adriatic Sea; Black Sea. 15-20 aboral elongated non contractile filiform ten- Known seasonality: 1-8. tacles; a parenchymatic diaphragm separates the Distribution: Atlantic; Mediterranean; Black hypostome from the polyp body; medusa buds in Sea. clusters on slightly branched inflated pedicels aris- References: Babnik (1948); Russell (1953); ing above aboral tentacles. Kramp (1961); Berhaut (1970); Brinckmann-Voss Medusa: usually with 3 short or rudimentary ten- (1970, 1987); Goy (1973b); Schmidt and Benovic tacles and one long principal tentacle that differs (1979); Gili (1986); Benovic and Bender (1987); from others not only in size, but also in structure. Boero and Bouillon (1993); Avian et al. (1995); References: Huang Jiaqui (1999), Xu and Huang Benovic and Lucic (1996); Medel and López- (2003). González (1996); Schuchert (2001a). Key for the medusae Genus Eugotoea Margulis, 1989 1. Principal tentacle moniliform, the three others Corymophidae with exumbrella divided in 4 cone-shaped ...... E. annulata prominent leaf-shaped facets separated by 4 longitu- – Principal tentacle with a single row of adaxial dinal large and deep grooves; with one marginal ten- cnidocysts knobs ...... E. bigelowi tacle with a terminal cnidocyst knob; without mar- ginal bulbs. Euphysora annulata Kramp, 1928 (Fig. 49G) Eugotoea petalina Margulis, 1989 (Fig. 49D-F) Medusa: umbrella 2 mm high, 1.4 mm wide, bar- rel-shaped, with thin mesoglea, with a pointed apex, Medusa:umbrella 0.7 mm high, 0.8 mm, wide, with a conspicuous umbilical canal; manubrium almost globular, mesoglea thick; exumbrella divided wide, as long as umbrellar cavity; principal margin- in 4 prominent leaf-shaped, oval, perradial facets al tentacle long, moniliform; the three other perradi- separated by 4 longitudinal large and deep grooves, al tentacles short, cone-shaped, the one opposite the a brown pigmented spot on the aboral third of each main tentacle the longest. facet; manubrium, large occupying almost whole Records from Mediterranean: eastern Mediter- subumbrellar cavity, extending till umbrella open- ranean; Adriatic Sea. ing; mouth surrounded with cnidocysts; radial Known seasonality: 11. canals simple; gonads surrounding central part of Distribution: Indo-Pacific; Mediterranean. manubrium; one perradial marginal tentacle with a References: Schmidt (1973); Schmidt and Ben- terminal cnidocyst knob; no tentacular or rudimen- ovic (1977; 1979); Xu and Huang (2003). tary marginal bulbs. Hydroid: unknown. Hydroid: unknown. Records from Mediterranean: eastern Mediter- Euphysora bigelowi Maas, 1905 ranean. (Figs. 49H-I) Known seasonality: 2. Distribution: endemic of Mediterranean Sea. Hydroid: only known from rearing. Hydranths References: Kramp (1961); Margulis (1989); Gili solitary; borne on a long, stout, hydrocaulus et al. (1998). enclosed in a thin membranous perisarc which is attached to an annular ring of thickened basal ecto- Genus Euphysora Maas, 1905 derm slightly below hydranth base; hydrocaulus cavity filled by parenchymatic endoderm with a lim- Hydroid: known for E. bigelowi; hydrocaulus ited number of simple peripheral endodermal canals, with thin perisarc, with cavity filled by parenchy- presenting papillae in its aboral third and more abo- matic endoderm with a limited number of simple rally numerous anchoring rootlets; hydranths vasi- peripheral endodermal canals, with anchoring form, with 35 oral more or less distinctly capitate

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tentacles set in irregular rows on hypostome; with terminal knob of cnidocysts; gonads first interradial, 15-20 aboral elongated non contractile filiform ten- in the distal half of the manubrium, encircling slow- tacles; a parenchymatic diaphragm separates the ly manubrium with age. hypostome from the polyp body; medusa buds borne Hydroid: unknown. in clusters on slightly branched inflated pedicels Records from Mediterranean: western Mediter- arising above aboral tentacles; asexual reproduction ranean. by basal constriction of hydrocaulus. Known seasonality: 5; 7; 9; 10. Medusa: umbrella up to 13 mm high, with a large Distribution: Atlantic; Antarctic; Arctic; conical apex at the end of which is a collection of Mediterranean. small papillae; with or without an apical canal which References: Kramp (1942, 1961); Ralph (1959); is mainly developed in non completely mature spec- Brinckmann-Voss (1970, 1987); Goy (1973b, 1983, imens; manubrium cylindrical, 2/3 to as long as 1997); Dallot, Goy and Carré (1988); Margulis umbrellar cavity; mouth circular; principal marginal (1989); Pagès and Bouillon (1997); Stepanjants et tentacle long, with several large cnidocysts knobs in al. (1997); Brinckmann-Voss and Arai (1998). unilateral, adaxial position and a distinct terminal Remarks: After Brinckman-Voss and Arai (1998) knob, the three other perradial bulbs each with a the specimens described from the Mediterranean by short, pointed tentacle variable in length and without Brinckmann-Voss (1970, 1987); Goy (1971, 1973b); cnidocysts clusters. Dallot, Goy and Carré (1988) should not belong to Records from Mediterranean: eastern Mediter- Paragotoea bathybia. ranean. Known seasonality: 2. Genus Vannuccia Brinckmann-Voss, 1967 Distribution: Indo-Pacific; Mediterranean. = Altairina Vargas-Hernández References: Kramp (1961); Schmidt (1973), and Ochoa-Figueroa, 1991 1976; Sassaman and Rees (1978); Xu and Huang (2003). Hydroid: hydrocaulus long, cylindrical, slightly enlarged at its two extremities, aboral third with Genus Paragotoea Kramp, 1942 (after Kramp papillae and, more aborally, numerous rooting (1961), not Ralph, 1959) anchoring filaments; filled with parenchymatic endo- dermal cells presenting numerous peripheral longitu- Corymorphidae without exumbrellar cnidocyst dinal canals; surrounded by a flexible perisarc tracks; with 4 radial canals, without gastric pouches; extending slightly below hydranth; hydranth vasi- with circular mouth; with 1 well-developed solid form, 12-14 oral moniliform tentacles with 4-6 cnido- tentacle terminating in large knob of cnidocysts and cyst clusters, 16 to 20 long aboral filiform tentacles 3 very large marginal bulbs without tentacles. with a more or less developed terminal swelling; parenchymatic diaphragm; medusa buds naked, in Paragotoea bathybia Kramp, 1942 clusters on short blastostyles above aboral whorl of (Fig. 49J) tentacles; asexual reproduction by transverse con- striction of the basal part of the hydrocaulus. Medusa: umbrella up to 1.6 mm wide, 2 mm Medusa: bell margin usually slightly asymmetri- high, square or rectangular, with thin exumbrellar cal, with or without apical process; no exumbrellar walls, with conical apex containing refractive cnidocyst tracks; marginal bulbs small, simple; 1 droplets; scattered cnidocysts on exumbrella; swollen marginal tentacle, hollow for half its length manubrium broadly flask-shaped to globular, and ending in long, large, oval to cylindrical extending from half subumbrellar cavity to umbrel- swelling armed with cnidocysts. la margin, proximal part vacuolated, distal part sex- References: Vargas-Hernandez and Ochoa- ual; mouth circular, rim with cnidocysts; 4 conspic- Figueroa, 1991. uous radial canals enlarged distally, with large endo- dermal cells and narrow light; 4 very large promi- Vannuccia forbesii (Mayer, 1894) nent marginal bulbs, 1 tentacular, 3 non tentacular (Figs. 49K-L) similar, each with an ectodermal abaxial spur; 1 stiff tapering marginal tentacle, proximal part hollow, Hydroid: solitary, hydrocaulus long cylindrical, distal part solid with very thick mesoglea, with large slightly enlarged at its two extremities, aboral third

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of hydrocaulus with papillae and, more aborally manubrium completely, in one or more rings; most- numerous rooting anchoring filaments; hydrocaulus ly with abaxial ocelli. Cnidome where known: as in filled with parenchymatic endodermal cells present- hydroids but additionally with desmonemes. ing numerous peripheral longitudinal canals; hydro- References: Wedler and Larson (1986); Calder caulus surrounded by a flexible perisarc extending (1988); Brinckmann-Voss (1989); Petersen (1990); slightly below hydranth; hydranth vasiform, with Kubota and Takashima (1992); Pagès et al. (1992); 12-14 oral moniliform tentacles carrying 4-6 cnido- Migotto (1996); Schuchert (1996, 2001b); Bouillon cysts clusters, with 16 to 20 very long aboral fili- (1999); Bouillon and Barnett (1999); Bouillon and form tentacles with a more or less developed termi- Boero (2000). nal swelling; with a parenchymatic diaphragm; medusa buds borne naked in clusters on short blas- Key to hydroids tostyles just above aboral whorl of tentacles; asexu- al reproduction by transverse constriction of the 1. Distinct button of ectodermal mucous gland cells basal part of the hydrocaulus. around mouth; gonophores as free medusae; Medusa: umbrella 3 mm high, bell-shaped, ellip- polyps often associated with sponges ...... soidal, with slightly asymmetrical margin; mesoglea ...... Dipurena evenly thin, without apical process or apical canal; – No distinct button of ectodermal mucous gland without exumbrellar tracks of cnidocysts; manubri- cells around mouth ...... 2 um cylindrical, length half to two-thirds of umbrella 2. Gonophores develop either in the upper axil of height; «gonads» encircling manubrium for almost the lower capitate tentacles or amongst the lower all its length; 4 narrow radial canals and circular whorl...... Coryne canal; one voluminous marginal tentacle at the base – Gonophores develop below capitate tentacles of the longest radial canal, hollow for half its length, and over filiform tentacles ...... Sarsia ending in long, large, oval cnidocyst swelling; three marginal bulbs the one opposite the tentacle larger Key to medusae than the other ones. Records from Mediterranean: western Mediter- 1. “Gonads” divided in two or more rings (except ranean, medusae raised from hydroids. Dipurena gemmifera) ...... Dipurena Known seasonality: 9-2. – “Gonads” not interrupted, undivided ...... 2 Distribution: Atlantic; Indo-Pacific; Mediter- 2. Adult medusae with manubrium extending ranean. beyond umbrella margin, with a thin proximal References: Kramp (1961); Brinckmann-Voss part...... Sarsia (1967, 1970). – Adult medusae with manubrium not extending beyond umbrella margin, without thin proximal Family CORYNIDAE Johnston, 1836 part...... Coryne

Hydroid: branched or unbranched, monophormic Genus Coryne Gaetner, 1774 colonies rising from a creeping stolon or encrusted = Syncoryna Ehrenberg, 1834; Staurocoryne base; hydranths with an oral whorl of capitate tenta- Rotch, 1872; Actigia Stechow, 1921 cles and often more capitate tentacles below, in whorls or scattered; sometimes filiform tentacles Hydroid: colony stolonal or erect, branching; (specialised sense organs) below capitate ones; hydranth with an oral whorl of capitate tentacles and gonophores usually on polyps, either as sessile with or without capitate tentacles either scattered or sporosacs, eumedusoids or free medusae. Cnidome in at least three whorls below oral one, with or with- where known : stenoteles with or without isorhizas out filiform tentacles; hypostome without distinct or mastigophores. button of ectodermal mucous gland cells; Medusa: umbrella bell-shaped; with or without gonophores as free medusae or fixed sporosacs apical chamber; no cnidocyst tracks; manubrium developing singly or in couples, on short pedicels tubular; mouth simple, circular; 4 radial canals and either in the upper axil of the lower capitate tenta- circular canal; with four tentacular bulbs with gas- cles or amongst the lower whorl. trodermal chamber and 2-4 hollow equally devel- Medusa: adult medusae with manubrium not oped marginal tentacles; “gonads” encircling extending beyond umbrella margin and without thin

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proximal part; marginal bulbs without adaxial forming tufts, final hydrocauli with a tendency to cnidocyst pads; “gonads” undivided. unilateral arrangement; perisarc of hydrocaulus ter- References: Brinckmann-Voss (1989, 2000); minating as a very delicate layer or sometimes in a Petersen, (1990); Kubota and Takashima (1992); basal cup at the base of the hydranth, perisarc main- Pagès et al. (1992); Schuchert, (1996, 2001b); ly smooth but ringed at base of hydrocauli and Brinckmann-Voss and Arai (1998). hydrocladia; hydranth cylindrical to spindle - shaped, with conical-rounded hypostome, with a Key to hydroids oral whorl of 4-5 capitate tentacles and 20-35 capi- tate tentacles scattered or in indistinct whorl over the In the Mediterranean the hydroids of the genus body of hydranth; medusa buds borne on single Coryne are difficult to differentiate from each other, pedicels in upper axils of tentacles of lower tentacles the characters often being variable and overlapping. Medusa: umbrella 3-4 mm in height, a little high- er than wide, bell-shaped to cylindrical, mesoglea 1. Gonophores non-axillary...... C. producta thicker at the apex; manubrium cylindrical, in full – Gonophores axillary ...... 2 extension about as long as subumbrellar cavity, 2. With filiform tentacles, colonies 1 to 2cm in without apical chamber; mouth simple circular; height...... C. pintneri.* manubrium almost entirely surrounded by – Without filiform tentacles ...... 3 «gonads», eggs few and large; 4 simple moderately 3. Colonies large 5-15 cm ...... 4 broad radial canals, circular canal narrower, radial – Colony small up to 3 cm, bushy, number of canals entering marginal bulbs adaxially; 4 margin- tentacles 18- 28, annulations of branches al tentacles fairly extendible, proximal part smooth irregular and broad ...... C. pusilla ** otherwise beset with numerous clasping cnidocysts 4. Colonies broad elongate; number of tentacles 16 clusters in indistinct spiral and a terminal cluster. to 22; annulations of branches in narrow rings... Records from Mediterranean: eastern and west- ...... C. muscoides.** ern Mediterranean. The Mediterranean occurrence – Colonies often forming tufts; number of tentacles of this species seems to need re-confirmation up to 35; perisarc of branches smooth with some (Schuchert, 2001b). annulations stretches ...... C. eximia Known seasonality: 3-6. Distribution: Atlantic, Indo-Pacific, Arctic, *Filiform tentacles are not always present and then Mediterranean. the species is hardly distinguishable from smaller References: Russell (1953); Kramp (1957b, colonies of C. pusilla (see Schuchert, 2001b). 1961); Brinckmann-Voss (1970, 1989); Goy **In the Mediterranean populations resembling C. (1973b); Petersen (1990); Goy et al. (1988, 1990, muscoides or C. pusilla pose considerable difficul- 1991); Kubota and Takashima (1992); Pagès et al. ties by showing all possible forms between the (1992); Boero and Bouillon (1993); Avian et al. forms found in the Atlantic. (Schuchert, 2001b). (1995); Medel and López-González (1996); Schuchert (1996, 2001b). Key to medusae Coryne muscoides (Linnaeus, 1761) 1. Medusa usually with an apical chamber; (Fig. 50E-F) umbrella up to 10 mm...... C. producta – Medusa without apical chamber ...... 2 Colonies with elongated shoots, up to 15 cm in 2. Medusa without medusa budding ...... C. eximia height, dichotomously or irregularly branched; – Medusa presenting medusa budding on tentacle perisarc brown in old colonies to almost transparent bulbs ...... C. prolifera in young ones, always annulated throughout with narrow rings, usually extending up to the aboral ten- Coryne eximia Allman, 1859 tacles of the hydranth in a funnel-shaped; polyp (Fig. 50A-D) pink, hydranth with 16 to 22 capitate tentacles, arranged in an oral whorl of 4-6 tentacles and lower Hydroid: colonies 1-5 cm arising from creeping tentacles scattered or in three to four indistinct ramified hydrorhiza, stolonal or erected; erected whorls, the single tentacles of successive whorls colonies profusely and irregularly branched often alternate in their position. Gonophores fixed

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sporosacs, borne in the upper axil of lower tentacles. cylindrical almost as long as bell cavity, with a dis- Cnidocysts: Stenoteles and desmonemes. tinct conical apical chamber with vestiges of Records from the Mediterranean: western umbilical canal; mouth simple, tubular; «gonads» Mediterranean (Italy, France, Spain). completely surrounding manubrium; radial canals Known seasonality: 1-12. entering endodermal chamber of bulbs in middle; 4 Distribution: north-eastern Atlantic, Mediter- long perradial marginal tentacles with many cres- ranean. cent-shaped cnidocyst clusters a small cylindrical References: Mammen (1963); Brinckmann-Voss terminal cnidocyst knob; with large marginal bulbs (1970); Patriti (1970); Boero and Bouillon (1993); each with an ocellus. Altuna (1994); Medel (1996); Medel and López- Records from Mediterranean: eastern and west- González (1996); Schuchert (2001b); Peña Cantero ern Mediterranean; Adriatic. and García Carrascosa (2002). Known seasonality: 3-11. Distribution: Atlantic; Mediterranean. Coryne pintneri Schneider, 1898 References: Kramp (1961); Brinckmann-Voss (Figs. 51A-B) (1970); Benovic (1973); Altuna (1993a); Boero et al. (1993); Avian et al. (1995); Benovic and Lucic Colonies mostly stolonal occasionally sparingly (1996); Medel and López-González (1996); branched with two hydranths, rarely with up to five Schuchert (2001b). side branches; up to 2 cm in height; perisarc not thick, yellowish, feebly annulated to smooth, fre- Coryne prolifera (Forbes, 1848) quently 2 or 3 annulations separated by smooth (Figs. 51E-G) intervals. Hydranths with 15-21 capitate tentacles either scattered or in 4-5 whorls, below them a Medusa: umbrella about 3 mm high and wide, whorl of 2-6 short filiform tentacles which are often bell-shaped, walls fairly thin, umbrella margin qua- absent, but always present in regenerating dratic; manubrium small, almost cylindrical, about hydranths. Gonophores fixed sporosacs, borne in 2/3 as long as umbrella cavity; «gonads» surround- two whorls in upper axil of tentacles in middle of ing almost whole length of manubrium living only hydranth body. both ends free; marginal tentacular bulbs large and Known seasonality: 11. tapering, with clusters of cnidocysts; medusa bud- Records from Mediterranean: western Mediter- ding from the marginal tentacle bulbs. ranean (Italy), Adriatic. Records from Mediterranean: western Mediter- Distribution: endemic of Mediterranean Sea. ranean; Black Sea. References: Brinckmann-Voss (1970); Boero and Known seasonality: 5. Fresi (1986); Boero and Bouillon (1993); Avian et Distribution: Atlantic; Mediterranean. al. (1995); Schuchert (2001b). References: Kramp (1961); Goy (1973b); Boero and Bouillon (1993); Schuchert (2001b). Coryne producta (Wright, 1858) Hydroid: unknown. (Figs. 51C-D) Coryne pusilla Gaertner, 1774 Hydroid: colonies stolonal, with creeping (Figs. 51H-I) hydrorhiza formed by a network or ramified stolons; hydrocaulus short, simple or rarely slightly and irreg- Colonies erect, branching several times, up to 3 ularly branched; perisarc smooth; hydranth elongat- cm in height; colonies shape rather broad an bushy, ed, larger distally, up to 1.5 mm in height; hypostome perisarc brown, annulated throughout, annulations dome-shaped, short; hydranth with one whorl of 4-6 of branches irregular and broad; hydranth red brown oral tentacles, 1-4 alternating whorls of capitate ten- with white dots, spindle shaped, with a conical pro- tacles with 3-6 tentacles per whorl, the uppermost boscis, sometimes with a perisarcal funnel like row larger than the rest; with a single aboral whorl of dilatation; about 18-28 tentacles, all capitate, in an 3-6 filiform tentacles; medusa buds borne among or oral whorl of 4-5 tentacles and scattered lower ten- below the lowest whorl of capitate tentacles. tacles. Gonophores fixed sporosacs, borne in upper Medusa: umbrella up to 7 mm wide, 10 mm axil of the tentacles along lower 1/2 to 2/3 of high, bell-shaped, with thick walls, manubrium hydranth.

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Known seasonality: 1-12. ered Coryne fucicola synonymous with Coryne pint- Records from Mediterranean: western and east- neri Schneider, 1897; the only difference with C. ern Mediterranean (Spain, France, Italy, Croatia, pintneri is the size and numbers of tentacles and the Greece). absence of filiform tentacles. Brinckmann-Voss Distribution: north-eastern Atlantic; doubtful does not agree and considers that it is a valid species records from Indian Ocean and Pacific, Mediterranean. difficult to identify due to the absence of knowledge References: Brinckmann-Voss (1970); Millard from its natural environment. (1975); Boero (1981); Boero and Fresi (1986); Gili Diagnosis: Colonies up to 40 mm high; stem erect, (1986); Boero and Bouillon (1993); Altuna (1994); simply branched; stem and hydrorhiza enclosed in a Avian et al. (1995); Medel and López-González thin perisarc; hydranth with numerous capitate ten- (1996); Schuchert (2001b). tacles, scattered and distant from each other; hydranth body pink, tentacles white. Gonophores Coryne epizoica Stechow, 1921 fixed sporosacs developing between the tentacles. (Fig. 51J) Records from Mediterranean: western Mediter- ranean (Italy, France). Colonies with creeping hydrorhiza giving rise Distribution: endemic of Mediterranean Sea. stems up to 3 mm high; perisarc brown, annulated References: Brinckmann-Voss (1970); Schuchert throughout. Hydranth with capitate tentacles which (2001b). are usually scattered but show a tendency towards arrangement in whorls. Gonophores fixed Genus Dipurena McCrady, 1859 sporosacs, borne in groups, 1-5 on the upper part of the stem. Cnidocysts: Stenoteles and desmonemes. Hydroid: colony stolonal, creeping, rarely with Records from Mediterranean: western Mediter- branching stems; often associated with sponges; ranean (Italy, France), record doubtful in Trieste. hydranth with one whorl or several whorls of capi- Distribution: endemic of Mediterranean Sea. tate tentacles all over body, either scattered or in References: Brinckmann-Voss (1970); Boero and more or less distinct whorls, sometimes with a whorl Bouillon (1993); Avian et al. (1995); Schuchert of filiform tentacles beneath capitate ones; hypos- (2001b). tome with a conspicuous button of high ectodermal gland cells; gonophores giving rise to free medusae Incertae sedis (mature gonophore unknown) usually in clusters, on short pedicels or blastostyle. Medusa: with 4 similar perradial tentacles; mar- Coryne caespes Allman, 1871 ginal bulbs without adaxial cnidocyst pads; with or without linear swellings on radial canals; “gonads” Hydrorhiza composed by a creeping entangled divided in two or more rings around manubrium mass of tortuous tubes, giving rise hydrocauli close- (except D. gemmifera) ; endoderm of sexual parts ly set, unbranched or scarcely branched; perisarc digestive, endoderm of non sexual parts chordal; irregularly annulated. Hydranth elongated, with manubrium usually extending well beyond umbrel- about 25 tentacles. Gonophores fixed sporosacs, lar margin; with ocelli. borne on short peduncles from the axils of the tenta- References: Petersen (1990); Pagès et al. (1992); cles. Schuchert (1996, 2001b). Records from Mediterranean: Gulf of La Spezia (Italy). Key to hydroids Distribution: endemic of Mediterranean Sea. Reproduction: ? 1. One whorl of oral capitate tentacles and one References: Brinckmann-Voss (1970); Boero and whorl of aboral filiform tentacles...... D.reesi Bouillon (1993); Schuchert (2001b). – Several whorls or scattered capitate tentacles below oral tentacles; filiform tentacles present or Coryne fucicola (de Filippi, 1866) absent...... 2 (Fig. 51K) 2. Perisarc enclosing hydrocaulus halfway of its length ...... D. halterata Species not described from its natural environ- – Perisarc wide into which basal part of hydranth ment but from an aquarium. Picard (1958) consid- can retract ...... D. ophiogaster

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Key to medusae References: Picard (1960a); Kramp (1961); Berhaut (1970); Brinckmann-Voss (1970, 1987); 1. Medusa presenting medusa budding along Goy (1973b); Benovic (1973); Schmidt and Benovic manubrium, gonads only on the distal swollen (1979); Castelló i Tortella (1986); Gili (1986); Ben- part of manubrium...... D. gemmifera ovic and Bender (1987); Goy et al. (1988, 1990, – Medusa not presenting medusa buds along 1991); Petersen (1990); Boero and Bouillon (1993); manubrium, gonads in two or more cylinders Avian et al. (1995); Benovic and Lucic (1996); around manubrium ...... 2 Medel and López-González (1996); Schuchert 2. Marginal tentacles with well developed terminal (2001b). knob of cnidocysts and several cnidocyst rings.. Remarks: After Hartlaub (1907) there may possi- ...... D. halterata bly be two or more ring-like «gonads». Picard – Marginal tentacles with irregularly distributed (1960a) described the polyp stage, but obtained only cnidocyst clusters and a small terminal knob .. 3 the newly released medusae and his identification is 3. Dome shaped umbrella; maximum high 5 mm; somewhat doubtful and needs reconfirmation (see manubrium in full extension 3 times length of Schuchert 2001b). umbrella; with oval to elongate apical chamber; «gonads» in 2-9 segments...... D. ophiogaster* Dipurena halterata (Forbes, 1846) – Triangular-shaped umbrella; maximum size 4 (Figs. 52B-E) mm; manubrium in full extension 2 times length of umbrella; with globular apical chamber; Hydroid: colonies stolonal, simple unbranched, «gonads» in 2 segments...... D. reesi* with hydrorhiza embedded in sponges, only the most distal part of the hydrocaulus and the hydranth The medusa of Dipurena ophiogaster and D. emerging; perisarc smooth enclosing hydrocaulus reesi are rather similar making many of their records halfway of its length; hydranth clavate to cylindrical questionable, but their hydroids are quite different. with rounded hypostome, ectoderm of hypostome A forth species of Dipurena was described from differentiating a well developed button of mucous the Mediterranean by Haeckel, 1864, Dipurena gland cells, up to 24 identical capitate tentacles dis- doligogaster, but it is most similar to Dipurena tributed in an oral whorl of 4- 5 tentacles and irreg- ophiogaster and the two species are considered con- ularly scattered tentacles along the body, without fil- specific by most of the authors (see Russell, 1953; iform tentacles; medusa buds borne in middle of Kramp, 1961; Brinckmann-Voss, 1970, Schuchert, hydranth independent of tentacles or on blatostyles 2001b). (reproductive exhaustion). Medusa: umbrella up to 6 mm wide, 8 mm high, Dipurena gemmifera (Forbes, 1848) bell shaped, with globular apical chamber; manubri- (Fig. 52A) um 2-3 times longer than umbrella height, with a long serpentine proximal part and a swollen distal Medusa: umbrella up to 5 mm high, bell-shaped, part; mouth simple circular; ... middle part of radial more or less pyriform; mesoglea moderately thick; canals with linear swellings; marginal tentacles of with short apical chamber; manubrium very long uniform diameter, smooth for most of their length, and thin, two times as long as umbrella height, com- each with large terminal cnidocyst knob and 3 to 6 posed of a thin proximal, long serpentine non diges- distinct rings of cnidocysts just above; tentacular tive part and a swollen distal digestive part; mouth bulbs prominent each with an abaxial ocellus; simple circular; «gonads» around distal swollen end «gonads» in 2 or more rings, living upper third free. of manubrium; medusa buds at intervals along the Records from Mediterranean: eastern and west- serpentine part of manubrium above oral dilatation; ern Mediterranean; Adriatic. marginal tentacles short with small marginal bulbs, Known seasonality: 3; 5-10; 12. with irregularly, transverse, clasps of cnidocysts and Distribution: Atlantic; Indo- Pacific; Mediter- a distinct terminal cnidocyst knob. ranean. Records from Mediterranean: eastern and west- References: Rees (1939); Babnik (1948); Kramp ern Mediterranean; Adriatic. (1961); Berhaut (1970); Brinckmann-Voss Known seasonality: 1; 9-12. (1970,1987); Bouillon (1971); Goy (1973b); Distribution: Atlantic; Mediterranean. Schmidt and Benovic (1979); Lakkis and Zeidane

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(1985); Gili (1986); Goy et al. (1988, 1990, 1991); Lakkis and Zeidane (1985); Goy et al. (1988, 1990, Pagès et al. (1992); Boero and Bouillon (1993); 1991); Pagès et al. (1992); Boero and Bouillon Avian et al. (1995); Benovic and Lucic (1996); (1993); Medel and López-González (1996); Medel and López-González (1996); Schuchert Schuchert (2001b). (2001b). Dipurena reesi Vannucci, 1956 Dipurena ophiogaster Haeckel, 1879 (Figs. 52I-K) (Figs. 52F-H) Hydroid: colonies stolonal arising from a creep- Hydroid: colonies stolonal, generally unbranched ing hydrorhiza formed by a very wide network of or branched once, up to 4 mm high, arising from a stolons; perisarc covering stolons and hydrocaulus; creeping, ramified hydrorhiza; perisarc thin, smooth hydranths club-shaped to fusiform, with rounded covering stolons and hydrocaulus, the perisarc of hypostome, ectoderm of hypostome differentiating a hydrocaulus widens distally and the basal part of large button of mucous gland cells; with one whorl hydranth is able to retract into this enlargement; of 4-5 oral capitate tentacles and at lower third one hydranth clavate to cylindrical, with large rounded aboral whorl of 4-5 aboral filiform tentacles; 1-3 hypostome, ectoderm of hypostome differentiating a medusa buds developing above aboral tentacles. well developed cap of gland cells, with 10-18 capi- Medusa: .. umbrella 3.9 mm wide, 2.5 mm high, tate tentacles in one oral whorl of 4 tentacles and bell-shaped but with rounded top; manubrium with below them lower capitate tentacles scattered or in globular apical chamber, at least two times longer indistinct whorls, with one aboral whorl of 2-6 fili- than umbrella height, divided in a long serpentine form tentacles (often reduced or absent); medusa proximal part and a thicker cylindrical distal one; buds singly or in clusters of 3-4, borne below capi- marginal tentacles long with numerous irregular tate tentacles and above filiform ones. clusters of cnidocysts, terminal cnidocyst knob Medusa: umbrella bell-shaped, 4-5.5 mm high, inconspicuous or absent; «gonads» in 2-3 rings 1.5 times higher than wide; mesoglea uneven thick, encircling manubrium, one distal, others half way becoming gradually thicker from margin towards down on serpentine part of manubrium, end of top, at apex 3 times as thick as lateral wall; relaxed gonads rings taper gently. velum spanning half to two-fifths of radius; Records from Mediterranean: western Mediter- manubrium very long, up to 3 times the umbrella ranean, medusae raised from hydroids. height, with long a thin serpentine proximal part and Known seasonality: 1; 3; 12. a broader distal (oral) extremity; with distinct round- Distribution: Atlantic; Mediterranean. ed apical chamber; mouth simple, tube like; References: Vannucci (1956); Brinckmann-Voss «gonads» distributed in 2-9 broad rings, encircling and Petersen (1960); Kramp (1961); Berhaut completely manubrium living upper third free, most (1970); Brinckmann-Voss (1970, 1987); Pages et al. distal one covering the distal swollen part; with 4 (1992); Altuna (1993a); Boero and Bouillon (1993); narrow radial canals and circular canal; four mar- Medel and López-González (1996); Schuchert ginal bulbs, rather flat, with cnidocysts pads and (2001b). bearing each an abaxial dark brown ocellus, bulb cavity egg-shaped; circular canal entering bulbs Genus Sarsia Lesson, 1843 = Stauridosarsia adaxially; with 4 very long a thin tentacles, length Mayer, 1910 up to 5 times umbrella height, with numerous irreg- ularly distributed cnidocyst clusters and a small ter- Hydroid with one oral whorl of capitate tentacles minal cluster. and with or without lower capitate tentacles, with or Records from Mediterranean: eastern and west- without filiform tentacles; tentacles usually longer ern Mediterranean. and thinner than in other Corynidae; gonophores as Known seasonality: 3-6. free medusae or fixed sporosacs developing below Distribution: Atlantic; Indo-Pacific; Mediter- capitate tentacles on over filiform once; cnidome ranean. with or without isorhiza cnidocysts. References: Kramp (1961); Brinckmann-Voss Medusa with manubrium extending beyond (1970, 1987); Bouillon (1966, 1971; 1978b, 1985b, umbrella margin, divided in a thin, long, serpentine 1995a); Goy (1973, 1997); Moreno et al. (1984); proximal part and a swollen distal one; “gonad”

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forming cylinder around thin serpentine part of Family EUPHYSIDAE Haeckel, 1879 manubrium living distal part free. References: Brinckmann-Voss (1989, 2000); Hydroid: solitary, hydrocaulus without parenchy- Petersen, (1990); Kubota and Takashima (1992); matic endoderm and peripheral canals, surrounded Pagès et al. (1992); Schuchert, (1996, 2001a, b); by a reduced perisarc often of more or less gelati- Brinckmann-Voss and Arai (1998). nous consistency or naked; hydranth without parenchymatic diaphragm, with an oral whorl of Sarsia tubulosa (M. Sars, 1835) short moniliform, capitate or filiform tentacles; abo- (Figs. 53A-J) ral tentacles moniliform or filiform, in one or three close-set whorls, or dispersed; hydranth often with Hydroid: colonies stolonal, issued from an irreg- an aboral irregular whorl of 4-16 short papillae, each ular, large meshed, anastomised network of tubular with an endodermal statocyst-like structure or with stolons, up to 1,3 cm ; hydrocauli erected simple or an adhesive mucus organ; gonophores as free slightly branched; perisarc smooth or slightly wrin- medusae or fixed sporosacs developing above abo- kled, corrugated, never truly annulated; hydranths ral whorl of tantacles. very elongated, clavate, with conical-rounded Medusa: umbrella generally evenly rounded; no hypostome, with 10-25 capitate tentacles distally exumbrellar cnidocyst tracks; manubrium stoutly arranged along digestive part of the hydranth, in cylindrical, not extending beyond umbrella margin; whorls which are often rather irregular, proximal mouth simple, circular; 1-4 marginal tentacles, part of hydranth without tentacles and with chordal either unequally developed or of similar length, all endoderm (sphincter); basal part of hydranth cov- of same structure; “gonads” encircling almost all ered with a thin filmy periderm; 1-8 medusa buds length of manubrium. borne on short peduncles chiefly but not exclusive at Remarks: Petersen (1990) recognised only two base of lowest tentacles; sometimes hydranth genera with medusae within the family Corymorphi- reduced to blastostyles. dae: Corymorpha and Euphysa. Euphysa medusae Medusa: umbrella up to 18 mm high, bell- were defined by him as follow: “Medusa with even- shaped, somewhat higher than wide, with interradi- ly rounded umbrella, without apical canal; with one al exumbrellar furrows, mesoglea moderately thick; to four tentacles unequally developed, but all of with a distinct apical chamber of varying length, same structure, moniliform or modified moniliform; usually globular; manubrium, cylindrical, very long, manubrium stout, cylindrical, with small round extending 2-3 times the height of the umbrella, con- mouth, shorter than bell cavity”. Petersen’s defini- sisting in a long thin, slender tubular proximal part tion, however, appears not well founded: Euphysa and a spindle shaped capacious distal portion; mouth flammea, E. japonica, Euphysomma brevia, for circular armed with cnidocysts; marginal tentacles instance, have four tentacles that are not unequally bulbs broad, radial canals entering marginal bulbs developed. Petersen considered the following gen- abaxially and enclosed in the mesoglea for a short era as identical with Euphysa: Hypolytus; Heterac- distance, glandular thickenings along radial canals tis; Meiorhopalon and Euphysomma. Euphysomma throughout most of the growth of the medusa, is here considered as valid. becoming diminished in the adult; marginal tenta- References: Petersen (1990); Pagès et al. (1992); cles very long with numerous clusters and patches of Bouillon (1999); Bouillon and Barnett (1999); cnidocysts, terminal knob spherical inconspicuous; Bouillon and Boero (2000). «gonads» forming a uniform thickening along the tubular part of the manubrium living both end free. Key to hydroids Records from Mediterranean: eastern and west- ern Mediterranean; Black Sea. 1. Mesopsammic hydranth with one type of Known seasonality: 4-5. tentacles more or less filiform; hydrocaulus with Distribution: Atlantic; Indo-Pacific; Mediter- four short papillae with endodermal statocyst, ranean. covered by leaf-like ectodermal lappet ...... References: Kramp (1961); Brinckmann-Voss ...... Siphonohydra (1970); Edwards (1978, 1983); Gili (1986); Goy et al. – Hydranth with two types of tentacles, oral (1988, 1990, 1991); Boero and Bouillon (1993); Medel capitate tentacles and aboral monilifiliform and López-González (1996); Schuchert (2001 a, b). tentacles; hydrocaulus with an irregular whorl of

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glandular papillae, each with an endodermal cavity, in extension never reaching beyond exumbrel- statocyst-like structure below aboral whorl of lar margin; mouth simple, circular, surrounded by tentacles ...... Euphysa cnidocysts; 4 radial canal and circular canal narrow; gonad encircling almost all manubrium, living upper Genus Euphysa Forbes, 1848 end of manubrium and mouth area free; one single, = Hypolytus Murbach, 1899 perradial marginal tentacle, moniliform, 3 non-tentac- = Meiorhopalon Salvini-Plawen, 1987 ular perradial marginal bulbs smaller than tentacular bulb and with slight spurs; with winter resting eggs. Hydroid: hydrocaulus about twice as long as Records from Mediterranean: eastern and west- hydranth, embedded in a soft, sticky perisarc, cov- ern Mediterranean; Adriatic. ered by mud and detritus; with an irregular whorl of Known seasonality: 1-12. glandular papillae, each with an endodermal stato- Distribution: Atlantic; Indo-Pacific; Mediter- cyst-like structure below aboral whorl of tentacles; ranean. hydranth almost cylindrical, with rounded hypos- References: Werner (1959); Kramp (1961); tome, with 3-10 oral capitate tentacles and up to 20 Berhaut (1970); Brinckmann-Voss (1970, 1987); aboral moniliform tentacles; asexual reproduction Benovic (1973,1976); Benovic and Bender (1987); by constriction of distal end of hydrocaulus and bud- Goy (1973, 1997); Gili (1986); Goy et al. (1988, ding of new hydranths with reversed polarity on 1990, 1991); Boero and Bouillon (1993); Avian et lower part of mother hydranth; medusa buds singly al. (1995); Benovic and Lucic (1996); Medel and or in clusters just above aboral tentacles. López-González (1996); Gili et al. (1998); Medusa: umbrella evenly rounded; 1-4 marginal Schuchert (2001a). tentacles often unequally developed but all of the same structure, tentacles usually moniliform. Euphysa flammea (Linko, 1905) Reference: Brinckmann-Voss and Arai (1998). (Fig. 54E)

Key to hydroids (see below E. aurata) Medusa: umbrella 12 mm high, 7 mm wide, bell- shaped, umbrella walls fairly thin; manubrium Key to medusae cylindrical, about two-thirds as long as umbrellar cavity; radial canals and circular canal narrow; 1. With one marginal tentacle in adult.... E. aurata «gonads» encircling almost whole manubrium – With 4 similar tentacles in adult ...... E. flammea except mouth area; four perradial marginal tentacles covered with scattered groups of cnidocysts, all Euphysa aurata Forbes, 1848 alike in adult, youngest stages with only one tenta- (Figs. 54A-D) cle, the other added successively. Records from Mediterranean: eastern Mediter- Hydroid: solitary, with hydrocaulus about twice ranean. as long as hydranth, embedded in a soft, sticky Seasonally: 5-7. perisarc covered by mud and detritus; hydranth Distribution: Arctic circumpolar; Atlantic; Indo- almost cylindrical, with rounded hypostome, with 3- Pacific; Mediterranean. 10 oral capitate tentacles and up to 20 aboral monil- References: Kramp (1961); Goy et al. (1988, iform tentacles; with an irregular whorl of papillae 1990, 1991); Boero and Bouillon (1993). each with an endodermal statocyst below aboral Hydroid: unknown. whorl of tentacles; asexual reproduction by constric- tion of the distal end of hydrocaulus and of budding Genus Siphonohydra Salvini-Plawen, 1966 of new hydranths with reversed polarity on lower part of mother hydranth; medusa buds borne singly Paedomorphic Hydrozoa reduced to hydroid or in clusters just above the aboral tentacles. stage; solitary, mesopsammic; hydranth club-shaped Medusa: umbrella about 6 mm high, higher than with an oral whorl of four very short tentacles alter- wide, bell-shaped, with rounded apex, mesoglea nating with an aboral whorl of four longer tentacles thick, especially in apical region; without pointed with parenchymatic endoderm, tentacles of both apex; with horizontal umbrella margin; velum fairly whorls more or less filiform; with buds above the wide; manubrium large, cylindrical, shorter than bell aboral tentacles; upper end of hydrocaulus with four

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short papillae with endodermal statocyst, covered by bigger and more spherical than the males, young leaf-like ectodermal lappet. Gonophores unknown. gonophores with an apical prolongation (as in the References: Clausen and Salvini-Plawen (1986); males) which is absent and replaced by an orifice in Salvini-Plawen (1987); Thiel, H. (1988); Petersen the mature gonophores; cnidome: desmonemes, (1990). microbasic euryteles, stenoteles. Records from Mediterranean: western Mediter- Siphonohydra adriatica Salvini-Plawen, 1966 ranean. (Fig. 54F) Known seasonality: 1 to 6. (as cyst 7 to 12). Distribution: endemic of Mediterranean Sea. With the characters of the genus. References: Bouillon (1974b, 1975); Gili (1986); Records from Mediterranean: Adriatic. Boero and Bouillon (1993); Medel and López- Seasonally: 2. González (1996). Distribution: endemic of Mediterranean Sea. References: Clausen and Salvini-Plawen (1986); Family PENNARIIDAE McCrady, 1859 Salvini-Plawen (1987); Thiel, H. (1988) Avian et al. (1995). Hydroid: colony large, pinnate, arising from a network of creeping stolons; hydrocaulus monosi- Family PARACORYNIDAE Picard, 1957 phonic, giving rise alternately from opposite sides to two series of numerous unbranched hydrocladia Hydroid: colony flat, circular, polymorphic; basal lying in one plane; longest hydrocladia in the middle Fig. divided in upper layer of broad endodermal cav- of colony, gradually decreasing in length upwards ities and basal layer of large, parenchymatic endo- and downwards; perisarc thick, firm; hydrocaulus derm cells continuous with those in dactylozooids, and hydrocladia with terminal hydranths (monopo- transversed by mesogloeal lamellae, all enveloped in dial); numerous hydranths on short pedicels origi- layer of ectoderm, lacking perisarc; gastrozooid short, nating on upper side of the hydrocladia; hydranths stout, with 1 to 4 whorls of solid capitate tentacles; spindle- or pear-shaped, with dome-shaped hypos- gonozooids short, lacking tentacles and mouth; dacty- tome; a whorl of 4-6 oral capitate tentacles, up to 18 lozooids around edge of colony, long, finger-shaped, capitate tentacles scattered or in more or less regular filled with parenchymatic endoderm; gonophores whorls on hydranth body, aboral whorl of up to 16 cryptomedusoid; eggs developed into actinulae inside semifiliform to slightly capitate aboral tentacles; 3- gonophore, or into encysted resting stage. 5 eumedusoids arising on short stalks just above Reference: Bouillon (1974b, 1975); Petersen aboral tentacles; sexes separated per colony; eume- (1990). dusoids free or not. Medusa: reduced to short-living eumedusoids; Genus Paracoryne Picard, 1957 manubrium not extending beyond umbrella margin; mouth simple, circular or absent; 4 radial canals; With the characters of the family. “gonads” completely surrounding manubrium; 4 permanently rudimentary tentacles, usually reduced Paracoryne huvei Picard, 1957 to mere bulbs, with or without ocelli. (Fig. 54G) Remarks: many of the reduced medusa species described in this family could be eumedusoids Stolonal colonies with encrusting hydrorhizae belonging to several Tubulariida or Zancleida fami- composed of naked coenosarc, giving rise three differ- lies; only the few species with known cycle can be ent kinds of polyps (gastrozooids, dactylozooids and referred to the Pennariidae. gonozooids); gastrozooids with 12-26 tentacles irreg- References: Wedler and Larson (1986); Calder ularly distributed in four verticils at distal half; dacty- (1988); Migotto (1996); Schuchert (1996); Bouillon lozooids large without tentacles neither mouth; gono- and Barnett (1999); Bouillon and Boero (2000). zooids without tentacles neither mouth; gonophores fixed sporosacs (cryptomedusoids), male and female Genus Pennaria Goldfuss, 1820 in different colonies; male gonophores in number of 2- 10 per gonozooid, ovoid, with a characteristic apical Eumedusoid and hydroid with characters of the prolongation; female gonophores 2-4 per gonozooid, family.

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Pennaria disticha Goldfuss, 1820 Hydroid pear-shaped, with three whorls of capi- (Figs. 55A-C) tate tentacles (oral, middle and proximal whorls). Between the middle and oral whorl the body nar- Hydroid arising from a network of creeping rows to form a slender neck. Four oral tentacles, stolons and forming large, pinnate, feather- like each with a terminal knob of cnidocysts; six tenta- colonies; hydrocaulus monosiphonic giving rise alter- cles in the middle whorl; proximal whorl near the nately from opposite sides to two series of numerous posterior end of the body, with 12 tentacles in two unbranched hydrocladia lying in one plane; longest closely approximated whorls of six tentacles point- hydrocladia in the middle of the colonies, gradually ing upwards and six tentacles pointing downwards. decreasing in length upward and downwards; perisarc Middle and proximal whorls of tentacles with two thick, firm; hydocaulus and hydrocladia with terminal groups of cnidocysts on their distal half in addition hydranths (monopodial); numerous hydranths on to the terminal knob. Gonophores cryptomedusoids. short pedicels originating on upper side of the hydro- Records from the Mediterranean: western cladia; hydranths spindle or pear-shaped, with dome- Mediterranean?, Adriatic. shaped hypostome; with a whorl of 4-6 oral capitate Distribution: northeastern Atlantic, Mediter- tentacles, up to 18 capitate tentacles scattered or in ranean. more or less regular whorls on hydranth body and an References: Rees (1941a, 1957); Petersen aboral whorl of up to 16 semifiliform to slightly cap- (1990); Boero and Bouillon (1993) Avian et al. itate aboral tentacles, 3-5 eumedusoids arising on (1995). short stalks just above aboral tentacles; sexes are sep- arated per colony; eumedusoids free or not. Family TUBULARIIDAE Fleming, 1828 Records from Mediterranean: eastern and west- ern Mediterranean, Adriatic. Hydroid: solitary or colonial; hydrocaulus divid- Known seasonality: 11-4. ed into distal neck region covered by thin perisarc, Distribution: warm waters around the world. and proximal stem which may be either short and References: Vervoort (1959); Brinckmann-Voss thick with tuber-like aboral processes, or long, (1970); Rossi (1971); García Corrales et al. (1985); cylindrical or cone-shaped with basal disc or with Gili (1986); Calder (1988); Avian et al. (1995); stolons covered by thicker perisarc; neck perisarc Medel (1996); Medel and López-González (1996); secreted from a groove on the hydranth proper; Schuchert (1996). hydranth vasiform, tentacles in two sets, oral ones filiform or pseudofiliform in one to several close-set Family TRICYCLUSIDAE Kramp, 1949 whorls, exceptionally capitate, or moniliform, (oral tentacles often slightly capitate or capitate in juve- Paedomorphic Hydrozoa reduced to hydroid niles); aboral ones in one whorl, long pseudofiliform stage, solitary, with pear-shaped hydranth, one or filiform, sitting on a more or less developed whorl of six capitate oral tentacles and two widely parenchymatic cushion; gonophores as free spaced whorls each of 8-14 stout, solid aboral, medusae or fixed sporosacs; often actinula larvae. imperfect moniliform, tentacles; hydrocaulus thin, Medusa: usually with exumbrellar cnidocyst same length as hydranth, ending in small pedal disc; tracks; 4 radial canals; mouth usually circular; perisarc covering hydrocaulus inflated, of gelatinous “gonads” encircling manubrium completely; 1-4 aspect; hydroid buds produced from lower part of marginal tentacles; no ocelli. hydranth; actinuloid larvae arising from under abo- References: Wedler and Larson (1986); Calder ral tentacles. Gonophores as fixed sporosacs, only (1988); Petersen (1990); Migotto (1996); Schuchert male have been observed. (1996); Bouillon (1999); Bouillon and Barnett Reference: Petersen (1990). (1999); Bouillon and Boero (2000).

Genus Tricyclusa Stechow, 1919 Key to hydroids

With the characters of the family. 1. Hydrocaulus lumen open, without parenchyme and peripheral endodermal canals but with Tricyclusa singularis (Schulze, 1876) longitudinal endodermal ridges...... 2 (Fig. 55D) – Hydrocaulus filled with parenchyme and with

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longitudinal peripheral endodermal canals; rearing experiments are necessary to elucidate life hydrocaulus widening from base to distal end cycles before assigning new specific names...... Tubularia Recent references: Schuchert (2001a, 2003). 2. Oral tentacles in one whorl; two, rarely up to five longitudinal endodermic ridges; medusa radially Key to hydroids symmetrical with 2 or 4 groups of tentacles...... Ectopleura 1. Colonies producing free medusae ...... 2 – Oral tentacles in two whorls; up to 8 or more – Colonies producing not released medusae...... 3 longitudinal endodermic ridges; medusae 2. Hydroid solitary, with 14-25 filiform oral asymmetrical with one group of marginal tentacles ...... E. dumortierii tentacles...... Hybocodon – Hydroid colonial, with 5-10 slightly capitate tentacles...... E. wrighti Key to medusae 3. Gonophores cryptomedusoids; female gono- phores with 8 laterally flattened crests 1. With tentacular marginal bulbs ...... 2 surrounding the opening ...... E. crocea. – Without tentacular marginal bulbs..... Rhabdoon – Gonophores eumedusoids; female gonophores 2. With normal, symmetrical umbrella...... 3 with 3-4 short round apical processes which may – With asymmetrical umbrella, bell margin be flattened ...... E. larynx obliquely set to the vertical axis ...... Hybocodon 3. With longitudinal exumbrellar cnidocyst tracks Key to medusae or rows...... Ectopleura – Cnidocysts in scattered or in clumps ...... 1. With four perradial marginal tentacles...... Plotocnide ...... E. dumortieri – With two opposite marginal tentacles ...... 2 Genus Ectopleura L. Agassiz, 1862 2. «Gonads» surrounding manubrium and forming 4 sac-like interradial pouches ...... E. sacculifera Hydroid: solitary or colonial; hydrocaulus high, – «Gonads» only surrounding manubrium...... 3 simple, with open lumen, without parenchymatic 3. With short conical apical chamber and apical endoderm and longitudinal endodermal canals, but canal; marginal tentacles with six to nine abaxial weakly divided by two, rarely up to five, internal lon- cnidocysts clusters and a larger terminal one ..... gitudinal endodermic ridges; perisarc thin, covering ...... E. minerva pyriform neck region, originating from collar on neck – Without apical chamber and apical canal; region and does not cover whole neck; hydranth vasi- tentacles with a terminal knob of cnidocysts, one form with filiform (except in E. wrighti where they are or two distal spherical rings of cnidocysts and moniliform to capitate) oral tentacles in one whorl and proximally one abaxial cnidocysts cluster ...... a whorl of long, filiform, aboral tentacles; gonophores ...... E. wrighti right above aboral tentacles, producing free medusae, eumedusoid or fixed sporosacs. Ectopleura crocea (L.Agassiz, 1862) Medusa: umbrella symmetrical, rounded, or pyri- (Figs. 55E-F) form; 8 longitudinal exumbrellar cnidocyst rows, issuing in pairs from tentacular bulbs; manubrium Hydroid colonial; hydrorhiza forming a dense mat short, at most reaching bell margin; 2 opposite or 4 giving rise to cluster of numerous polyps; stem equally developed, simple perradial marginal tenta- unbranched, up to 70 mm high, perisarc firm and cles, moniliform or with abaxial cnidocyst clusters; smooth, with scattered groups of several annulations; 4 radial canals. coenosarc with 2-5 longitudinal endodermal ridges. Remarks: many hydroid-based nominal species Polyp reddish, with one oral whorl of 18-24 filiform of Ectopleura have recently been described, the tentacles with their bases adnate to hypostome, and medusae being known either as just liberated juve- one aboral whorl of 22-30 slender tentacles longer niles or as medusa buds; some medusae with than the oral ones; cnidocysts of aboral tentacles, con- unknown cycle, and described long ago, could cor- centrated in a longitudinal band of the aboral side. respond to some of those hydroids. In groups with Oral tentacles circular in cross-section, aboral ones species based on either polyps or medusae only, for-sided. Neck region more than 1/2 length of

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hydranth, finely and longitudinally striated, with a col- Records from Mediterranean: eastern and west- lar at lower edge which forms a shallow groove from ern Mediterranean; Adriatic Sea. which perisarc covering the neck region is secreted. Known seasonality: 1-12. Gonophores in small groups on pedicels borne on Distribution: Atlantic; Indo-Pacific, Mediter- blastostyles (about 8) in circles close to bases of abo- ranean. ral tentacles. Gonophores cryptomedusoid, without References: Kramp (1959a, 1961); Berhaut radial canals and ring canal, immature male (1970); Brinckmann-Voss (1970, 1987); Benovic gonophores elongate ovoid, spherical when mature, (1973); Schmidt and Benovic (1979); Dowidar with four tentacle rudiments; female gonophores (1983); Castello i Tortella (1986); Benovic and Ben- ovoid to spherical with eight, laterally flattened, thin der (1987); Goy (1973b); Gili (1986); Goy et al. transparent crests surrounding opening of bell through (1988, 1990, 1991); Hirohito (1988); Petersen which spadix often protrudes; newly released actinula (1990); Boero and Bouillon (1993); Avian et al. without oral tentacles. Cnidocysts: Stenoteles and (1995); Benovic and Lucic (1996); Medel and desmonemes (in Brickmann-Voss, 1970). López-González (1996). Records from Mediterranean: western Mediter- ranean, Adriatic. Ectopleura larynx (Ellis and Solander, 1786) Known seasonality: 1 to 12. (Figs. 56A-B) Distribution: circuntropical in shallow waters. References: Brinckmann-Voss (1970) as Tubu- Hydroid colonial, hydrorhiza forming dense mat laria; Petersen (1990); Boero and Bouillon (1993) giving rise to numerous stems in dense groups up to as Tubularia; Avian et al. (1995); Medel and López- 70 mm high; perisarc of hydrocauli firm and smooth González (1996) all as Tubularia. but with irregular annulations; coenosarc with 2 longi- tudinal ridges. Polyp with long hypostome, one oral Ectopleura dumortierii (Van Beneden, 1844) whorl of up to 20 long, slender, filiform tentacles (Figs. 55G-J) adnate to hypostome and forming longitudinal ridges over distal half of hypostome, and one aboral whorl of Colonies stolonal; hydrocaulus, erect, up to 100 20-25 longer filiform tentacles, slender, laterally flat- mm high, solitary, simple or slightly branched, end- tened at their bases, distance between to adjacent ten- ing in a terminal hydranth and increasing in width tacles equal to the tentacle base diameter. Neck region from base to distal end; perisarc horn-coloured cov- with longitudinal striations, nearly as long as ering hydrocaulus till proximal end of hydranth, hydranth, and with a collar grooved basally which pro- irregularly annulated; hydrocaulus endoderm with duces the thin perisarc covering the neck. Gonophores up to 4 longitudinal ridges; neck region with gland on blastostyles in circles around oral and aboral tenta- cells forming an indistinct collar; hydranth flask- cles. Male gonophores on, up to 12, long pedicels shaped, with a rounded hypostome; with one whorl borne on up to 12 long, pendant, and unbranched blas- of 14-25 rather short rounded oral filiform tentacles, tostyles; female gonophores on, up to 12, shorter blas- with oval bases not adnate to hypostome and one tostyles (with up to 8 gonophores) dichotomously whorl of up to 30 long, aboral, semifiliform tenta- branched. Gonophores eumedusoids, without radial cles; up to 10, once dichotomously branched, blas- canals but with ring canal; female ovoid, with 3-4 tostyles above aboral tentacles, bearing clusters of short round apical processes which may be flattened medusa buds at their terminal end. giving the “ears” appearance; male gonophores longer Medusa: umbrella 2-3 mm high, nearly spherical, and slender, with very short, closely-set apical mesoglea very thick, especially in apical region; apical processes; actinula, at liberation, with an aboral whorl canal sometimes present; velum fairly broad; exum- of 6-13 tentacles with swollen tips; oral tentacles not brella with four pairs of cnidocyst tracks; manubrium yet developed or as 3-5 rudiments. very large, spherical at base, tapering towards mouth, Records from Mediterranean: western Mediter- extensile; mouth simple, tube-like, mouth rim with ranean. cnidocysts; 4 perradial marginal tentacles with large Known seasonality: 3, ? basal bulbs and prominent round cnidocyst clusters on Distribution: mainly northern (west and east) abaxial surface; «gonads» completely surrounding Atlantic; northern Pacific; Mediterranean (records manubrium, living mouth area free; development from southern hemisphere probably due to transport through a pro-actinula and actinula stage. by ships (Petersen, 1990).

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References: Gili (1986) as Tubularia; Petersen cnidocysts tracks issuing in pairs from the four mar- (1990); Medel and López-González (1996) as Tubu- ginal bulbs, continuing almost to apex, and forming laria; Schuchert (2001a). 8 slight crests along exumbrella; manubrium half as long as umbrellar cavity; «gonads» surrounding the Ectopleura minerva Mayer, 1900b manubrium and forming four large, interradial, sac- (Fig. 56C) like pouches hanging down from middle part of manubrium almost to mouth level; two long oppo- Medusa: umbrella 2,5 mm high, pear-shaped to site marginal tentacles, their distal part with 20- 25 conical bell-shaped, narrowing at base; mesoglea abaxial clusters of cnidocysts and two rudimentary thicker apically but without clear apical projection; bulbs. exumbrella with 4 pairs of longitudinal cnidocysts Hydroid: unknown. tracks originating from the marginal bulbs and extend- Records from Mediterranean: western Mediter- ing near apex of umbrella; manubrium tubular, about ranean. two third length of umbrella cavity, with short conical Known seasonality: 2. apical chamber and apical canal, the size of both Distribution: Indo-Pacific; Mediterranean. depending on age and preservation; mouth simple, References: Kramp (1961); Brinckmann-Voss tubular; radial canals and circular canal narrow; with (1970, 1987); Bouillon (1978b); Boero and Bouillon two moderately broad opposite marginal tentacular (1993). bulbs and two slightly smaller non tentacular bulbs; the two opposite perradial marginal tentacles each Ectopleura wrighti Petersen, 1979 with six to nine abaxial cnidocysts clusters and a larg- (Fig. 56E) er terminal one; «gonads» completely surrounding manubrium living most distal part free, tentacles and Hydroid: colonial issued from a creeping manubrium typically cream in color. hydrorhiza, stolons not clearly demarcated from Remarks: the medusa Ectopleura minerva has hydrocauli; hydranth very slender, vasiform with been described from Florida, it is known from the one oral whorl of 5-10 slightly capitate or monili- Bermudas, the Mediterranean, the Seychelles, form tentacles which are not adnate to hypostome India, China, Japan and the Bismarck Sea. Ecto- and an aboral whorl of 11-20 filiform tentacles; neck pleura minerva hydroid stage is still unknown, region long and slender, with low ring-shaped collar several Ectopleura types of hydroid have been forming groove from which thin outer periderm is described producing unreleased or just released secreted; hydrocaulus slender, unbranched, of equal two tentaculated medusae, particularly E. pacifica width throughout; inner lumen divided into two lon- Thornely, 1900 from Papua New Guinea, but none gitudinal canals by two endodermal ridges formed of them have their adult stage known and rearing by highly vacuolated cells, periderm flexible, thin experiments will thus be necessarily before eluci- and smooth, covering hydrocauli and stolons; dating and clarifying their complex and confuse medusa buds born above the aboral tentacle whorl; synonymy. carried on 5-8 short, dichotomously branched blas- Records from Mediterranean: eastern and west- tostyles. ern Mediterranean. Medusa: umbrella nearly hemispherical, with Known seasonality: 1-12. four longitudinal meridian pairs of cnidocyst tracks; Distribution: Atlantic; Indo-Pacific; Mediterranean. with four perradial marginal bulbs; with two oppo- References: Kramp (1961); Goy (1973b); Sugiu- site marginal perradial tentacles with a terminal ra (1977); Bouillon (1978 a,b); Calder (1988); Hiro- knob of cnidocysts and distally one or two spherical hito (1988); Petersen (1990); Goy et al. (1988, 1990, cnidocyst knobs encircling tentacle, proximally one 1991); Schuchert (1996). abaxial cnidocyst cluster; manubrium nearly as long Hydroid: unknown. as subumbrellar cavity; completely encircled by «gonads». Ectopleura sacculifera Kramp, 1957a Records from Mediterranean: hydroid eastern (Fig. 56D) and western Mediterranean, Adriatic. Only young medusae liberated in the laboratory known (Brinck- Medusa: umbrella 3 mm high, 2.8 mm wide mann-Voss, 1970). slightly conical, mesoglea thick, exumbrella with 8 Known seasonality: 1-12.

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Distribution: Atlantic?; western Mediterranean. usually with 5 longitudinal exumbrellar cnidocyst References: Brinckmann-Voss (1970, 1987); tracks, 2 issued from tentacular bulb, 1 track from Petersen (1979, 1990); Boero and Bouillon (1993); each non tentacular bulb; velum moderately broad; Avian et al. (1995), Peña Cantero and García Car- manubrium large cylindrical mounted on a short rascosa (2002). peduncle never reaching beyond margin even in full extension; mouth with a narrow ring of cnidocysts; Genus Hybocodon L. Agassiz, 1862 1 tentacular bulb with 1 or more moniliform tenta- cles (with adaxial clasps according to Schuchert, Hydroid: solitary, with high stems, hydrorhiza 1996) and with medusae buds, 3 non tentacular irregularly branched; hydrocaulus tubular, with bulbs reduced; «gonads» completely surrounding open lumen, without parenchyme and longitudinal manubrium, living peduncle and most distal portion peripheral canals but weakly divided by eight or free; medusa buds on marginal bulbs; eggs develop- more longitudinal endodermic ridge; perisarc origi- ing in actinulae on manubrium which may later be nating just below hydranth and much inflated found free in plankton. around whole neck region; secreted from groove Records from Mediterranean: western Mediter- between hydranth and neck; oral tentacles filiform ranean. to pseudofiliform in two closely set whorls, aboral Known seasonality: 3-6. tentacles in one whorl, filiform to pseudofiliform; Distribution: Atlantic; Indo-Pacific; Antarctic, blatostyles dichotomously branched. Arctic; Mediterranean. Medusa: bilaterally symmetrical, with umbrella References: Kramp (1961); Arai and Brinck- margin at oblique angle to vertical axis; no pointed mann-Voss (1980); Gili (1986); Boero and Bouillon apical process; with or without exumbrellar cnidocyst (1993); Medel and López-González (1996); tracks; manubrium cylindrical on short peduncle not Schuchert (1996, 2001a). extending beyond umbrellar margin; 4 radial canals, 1 short, 2 medium sized and one longer; with 1 sim- Genus Plotocnide Wagner, 1885 ple or compound marginal bulb with 1-3 moniliform tentacles corresponding to the longest radial canal; 3 Tubulariidae with exumbrellar cnidocysts scat- remaining perradial bulbs rudimentary. tered singly or in clumps; with a dome-shaped api- cal chamber lined with vacuolated endodermal cells. Hybocodon prolifer L. Agassiz, 1862 (Figs. 56F-H) Plotocnide borealis Wagner, 1885 (Fig. 56I) Hydroid: colonies with hydrorhiza formed by branching stolons embedded in sponges; hydro- Medusa: umbrella up to 3.5 mm wide and high; caulus solitary or sparingly aggregated, long, gradu- spherical to bell-shaped, with rounded apex, ally enlarging to just below hydranth, with firm mesoglea very thick mainly at apex, thinning slight- perisarc; endoderm of hydrocaulus with a central ly towards umbrella opening; with exumbrellar lumen and several longitudinal ridges; neck region cnidocysts scattered singly or in clumps; with a between hydrocaulus and hydranth surrounded by a dome-shaped apical chamber lined with vacuolated loose filmy, wrinkled perisarc; hydranth pear- endodermal cells above manubrium; manubrium shaped, with a rounded hypostome, with up to 50 flask-shaped, half as long as umbrellar cavity; short oral filiform tentacles in 2 closely set whorls, mouth simple with a ring of cnidocysts; «gonads» a the most distal being the shorter and up to 31 longer thick ring around manubrium, living mouth and aboral filiform tentacles in one whorl, the base of uppermost portion of manubrium free; radial canals aboral tentacles adnate to basal part of hydranth; and circular canal simple; with 4 threadlike, solid medusa buds on branching blastostyles, bearing marginal tentacles ending in a large, oval, swelling numerous buds, just above aboral tentacles; the studded with cnidocysts; marginal tentacular bulbs older medusa buds themselves carrying buds while small globular. still fixed on hydranths. Remarks: the presence of this arctic species in the Medusa: umbrella 3 mm wide, up to 5 mm high, eastern Mediterranean is based on a single small bell-shaped, evenly rounded, umbrella margin specimen (less than 1 mm high) described by Goy et oblique to vertical axis, mesoglea moderately thick; al. (1988), lacking apparently most of the character-

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istic features of the species: no vacuolated apical (1993); Avian et al. (1995); Benovic and Lucic chamber, no apical mesoglea thickening, no exum- (1996). brellar cnidocysts, no ring-shaped «gonads». This identification is doubtful Genus Tubularia Linnaeus, 1758 Hydroid: unknown. Known seasonality: 1. Hydroid: solitary; hydrocaulus long, tubular, Distribution: Arctic and Subarctic, circumpolar; widening from base to distal end, inner lumen filled Atlantic; Indo- Pacific; Mediterranean? with parenchymatic endoderm, penetrated by 8 or References: Beyer (1955) Hand and Kan (1961); more longitudinal endodermal peripheral canals, one Kramp (1961); Hartlaub (1907); Kramp (1942, wider than the others; circular or lobed basal disc, and 1959a, 1961, 1968); Naumov (1960-1969); Arai and supporting tubes developed from lower part of stem; Brinckmann-Voss (1980); Goy et al. (1988, 1991); thin perisarc around neck secreted from groove Boero and Bouillon (1993). between hydranth base and neck; hydranth vasiform, with two or more whorls of oral filiform and one Genus Rhabdoon Keferstein and Ehlers, 1861 whorl of filiform aboral tentacles; bases of aboral ten- tacles continued as ridges over hydranth base; blas- Tubulariidae with single hollow marginal tenta- tostyle with unbranched main stem, with or without cle ending in large, complex knob of cnidocyst clus- thin side branches; gonophores reduced to eumedu- ters; without marginal tentacular bulbs; manubrium soid or to sessile cryptomedusoid, with or without occupying almost entire bell cavity; with vacuolated distal processes, in which the origin from a biradially cells containing refractive droplets along 4 radial symmetrical medusa, can be usually traced. canals, at manubrium apex and bell margin; Refrences: Petersen (1990); Schuchert (2001). «gonads» surrounding distal 2/3 of manubrium. Key Rhabdoon singulare Keferstein and Ehlers, 1861 (Fig. 56J) 1. Female gonophore eumedusoid, without any tentacle, with four radial canals and a ring canal Medusa:umbrella 1.6 mm wide, 2.1 mm high, ...... T. Indivisa. barrel-shaped, apex dome-shaped, mesoglea thin at – Female gonophore cryptomedusoid, with one the apex larger at the umbrellar sides; exumbrella tentacle-like process, without radial canal and margin thick, irregular, containing numerous cnido- ring canal ...... T. ceratogyne cysts; subumbrellar opening and velum narrow; exumbrella with 4 perradial longitudinal exumbrel- Tubularia ceratogyne Pérès, 1920 lar cnidocyst tracks, 4 additional interradial and (Figs. 57A-B) sometimes adradial ones; manubrium large flask- shaped occupying almost the entire subumbrellar Hydroid solitary but growing in clusters. cavity, upper third vacuolated; mouth simple, circu- Hydrocaulus up to ca 60 mm, with one larger and lar, covered with cnidocysts; 4 protruding radial about seven smaller peripheral canals surrounding canals; «gonads» on the two distal thirds of the parenchymatic centre, perisarc firm, annulations manubrium; with a single hollow tentacles ending in absent; stem attached to substrate by irregularly a large knob consisting of numerous stalked capita- shaped basal disc forming one or two short rhi- tions containing cnidocysts. zomes covered by thick perisarc and 2-4 support- Hydroid: unknown. ing tubes irregularly wrinkled originating from Records from Mediterranean: eastern and west- lower part of stem. Hydranth with long oral tenta- ern Mediterranean; Adriatic Sea. cles adnate basally to hypostome and connected to Known seasonality: 1-11. hypostome by thin membrane for some distance; Distribution: Atlantic; Indo-Pacific; Mediter- aboral tentacles about 30, with oval bases; neck ranean. region nearly as long as hydranth, covered by thin References: Kramp (1961); Brinckmann-Voss perisarc originating in groove between hydranth (1970, 1987); Benovic (1976); Benovic and Bender base and neck. Gonophores on short pedicels on 7- (1987), Goy (1973, 1983); Dallot, Goy and Carré 12 (usually 8) long and unbranched blastostyles; (1988); Pagès et al. (1992); Boero and Bouillon female ovoid, cryptomedusoid, without radial

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canals and ring canal, with one hollow, tentacle- Suborder ZANCLEIDA Russell 1953 like process bent over opening of gonophore; male spherical, cryptomedusoid, without distal process- Hydroid: colony floating or fixed; fixed colonies es. Female gonophores inserted irregularly over arising either from simple creeping stolonal tubes, surface of blastostyle, male gonophores arranged from an encrusting basal mat, from upright branched in four to five longitudinal rows; cnidome: hydrorihza consisting of a central axis of perisarc desmonemes, anisorhiza, microbasic euryteles, covered by coenosarc, or from a calcified exoskele- stenoteles. ton; hydranths monomorphic or polymorphic, oral Records from Mediterranean: recorded only tentacles capitate or moniliform, aboral tentacles in from the Strait of Gibraltar and nearby areas of Gulf whorls or scattered, either capitate, moniliform, of Cádiz. ramified capitate, reduced or without tentacles; free Known seasonality and reproduction: 6;10;12. medusae, eumedusoids or sporosacs. Records outside the Mediterranean: northeastern Medusa: manubrium flask-shaped, with quadrate Atlantic. or octagonal base and cylindrical mouth tube; References: Teissier (1965); Patriti (1970); “gonads” usually interradial; exumbrellar cnidocyst Hughes (1983); Petersen (1990); Medel and López- pouches or tracks; 0-2 or 4 marginal tentacles with González (1996). or without abaxial cnidophores; marginal tentacles developed only at junction between radial and circu- Tubularia indivisa Linnaeus, 1758 lar canals; with or without ocelli. (Figs. 57C-F) References: Petersen (1990); Boero, Bouillon and Gravier-Bonnet (1995); Bouillon (1999); Bouillon and Polyps solitary but in clusters; stem up to 200 Barnett (1999); Boero, Bouillon and Gravili (2000). mm high (but usually shorter), perisarc firm and smooth; coenosarc with one larger and 9-12 smaller Key to hydroids peripheral canals around central lumen; stem attached to substrate by relatively broad and thick 1. Hydroids...... Porpitidae. lobate basal disc, and several supporting tubes orig- – Holonies fixed by hydrorhizae...... 2 inating from lower half of stem, which grow over 2. Hydrorhiza incrusting forming an a crust-like substrate as short rhizomes. Hydranth with up to 6 stolonal plate...... Rosalindidae whorls of 40-60 long oral tentacles continued over – Hydrorhiza formed by creeping stolon tubes hypostome as longitudinal ridges and 25-35 aboral recovered by perisarc ...... 3 tentacles with laterally-flattened oval bases; neck 3. Cnidocysts on hydranth body wall arranged in region as long as hydranth, covered by thin perisarc conspicuous rounded patches; hydranth with originated in groove between the hydranth base and moniliform or modified moniliform aboral distal part of the neck. Gonophores on short pedicels tentacles...... Cladocorynidae. borne on up to 12 unbranched blastostyles (each – Cnidocysts not in patches on hydranth body wall; with up to 30 older gonophores); female gonophore hydranth without moniliform tentacles eumedusoid, ovoid to spherical, with four radial ...... Zancleidae. canals of unequal length and a ring canal, without tentacles; male gonophore cryptomedusoid, ovoid to Key to medusae spherical, with rounded distal end; actinula with whorl of short oral tentacles at liberation; cnidome: 1. Marginal tentacles terminating in a single large desmonemes, anisorhiza, microbasic euryteles, spherical cnidocyst knob...... Porpitidae stenoteles. – Marginal tentacles with numerous stalked Records from Mediterranean: eastern and west- capsules containing cnidocysts, stalk of the ern Mediterranean, Adriatic. capsules threadlike, very extensile (cnidophores) Distribution: temperate to colder waters of north- ...... Zancleidae ern Atlantic and Pacific, Arctic Sea, Mediterranean. References: Naumov (1960); Petersen (1990); Family CLADOCORYNIDAE Allman, 1872 Cornelius and Ryland (1990); Boero and Bouillon (1993); Avian et al. (1995); Medel and López- Hydroid: stem simple or slightly branched, rising González (1996); Schuchert (2001a). from a creeping stolon; hydranth club-shaped, oral

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tentacles moniliform or capitate, in one whorl, abo- Avian et al. (1995); Medel and López-González ral tentacles moniliform or branched capitate, scat- (1996); Peña Cantero and García Carrascosa (2002). tered or in several whorls; cnidocysts on body wall arranged in conspicuous rounded patches or scat- Family PORPITIDAE Goldfuss, 1818 tered around the base of oral and aboral tentacles; gonophores carried singly or on short, branched Hydroid: colony floating, with a chitinous inter- pedicels, on lower or middle part of hydranth; with nal skeleton, covered by mantle, and forming a free medusae or fixed cryptomedusoids sporosacs. floating chamber; with a central large gastrozooid Medusa: only two exumbrellar pouches, contain- and marginal gastro-gonozooids and dactylozooids. ing macrobasic euryteles, on non tentaculate perra- Medusa: 4 or 8 of exumbrellar stenotele cnido- dial marginal bulbs; tentaculate perradial marginal cyst tracks issued from marginal bulbs; 4 or 8 radial bulbs very large, without cnidocyst pouches; tenta- canals and a circular canal; manubrium short, coni- cles with cnidophores; “gonads” interradial on cal; with quadrate or octagonal base; mouth circular; manubrium. “gonads” perradial or irregularly arranged perradial- References: Wedler and Larson (1986); Bouillon, ly and interadially; 2 opposite, perradial, capitate Boero and Seghers (1987); Petersen (1990); Boero, marginal tentacles; with or without 2 additional Bouillon and Gravier-Bonnet (1995); Migotto smaller capitate tentacles adaxial to the first; tenta- (1996); Schuchert (1996). cles with macrobasic euryteles; zooxanthellae gen- erally present. Genus Cladocoryne Rotch, 1871 References: Bouillon (1984d); Calder (1988); Petersen (1990); Pagès et al. (1992); Schuchert Hydrocaulus long, unbranched or sparingly (1996); Bouillon (1999); Bouillon and Barnett branched, covered by perisarc, arising from a creep- (1999); Bouillon and Boero (2000). ing hydrorhiza; hydranth club-shaped, with oral whorl of 4-6 short capitate tentacles, one to four Key to hydroids whorls of branched-capitate aboral tentacles; one or two patches of macrobasic eurytele cnidocysts on 1. Disc-shaped floating colony without sail...... hydranth body; gonophores as cryptomedusoid ...... Porpita fixed sporosacs or as medusa buds, on short pedicels – Oval to elliptical-shaped floating colony; with a between or over aboral tentacles. median sail...... Velella

Cladocoryne floccosa Rotch, 1871 Key to medusae (Fig. 57G) 1. 4 radial canals; manubium with quadrate base; 4 Colonies composed of creeping hydrorhizae giv- capitate tentacles...... Velella ing rise erect and sparingly branched hydrocauli; – 8 radial canals; manubrium octagonal; 2 capitate perisarc yellowish to transparent, smooth or with tentacles...... Porpita several groups of annulations; hydranth nude with an oral whorl of 4-6 short capitate tentacles and 1-4 Genus Porpita Lamarck, 1801 whorls of branched capitate aboral tentacles; oval = Porpema Haeckel, 1888 areas of microbasic euryteles cnidocysts on the hydranth. Gonophores spherical (cryptomedusoids) Hydroid: colony floating, dark blue, diameter up on short pedicels between or over aboral tentacles. to 30 mm, mostly smaller, with disk-shaped mantle Cnidocysts: macrobasic euryteles and stenoteles. and internal float, margin soft, flexible; central region Records from Mediterranean: eastern and west- firm, slightly convex, with a central pore and numer- ern Mediterranean, Adriatic. ous stigmata; mantle with radiating endoderm canals; Known seasonality: 4-7. internal chitinous float consisting of a series of con- Reproduction: 4-7 centric chambers; a disk-shaped reservoir of cnido- Distribution: temperate and tropical waters cysts between float and central gastrozooid; under around the world. surface with one large central gastrozooid, a median References: Rossi (1961); Brinckmann-Voss circle of gastro-gonozooids, and a peripheral circle of (1970); Gili (1986); Boero and Bouillon (1993); dactylozooids; central gastrozooid short and broad

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with a terminal mouth, without tentacles or prominent cnidocysts concentrated in two lateral bands on the cnidocyst clusters; gastro-gonozooids clavate, lack- narrow sides, mouth lacking; colour: float deeply ing tentacles but with prominent cnidocyst clusters blue when alive, medusa buds yellow-olive from scattered over body, medusae develop near base in symbiotic algae. clusters; dactylozooids with a distal whorl of 4 capi- Medusa: with 4 exumbrellar cnidocyst rows, 4 tate tentacles, body with varying number of short, radial canals; 2 pairs of opposite, perradial tentacles, small capitate tentacles in 3 vertical rows. a short adaxial one and a long abaxial one, each with Medusa: with 8 radial canals; manubrium coni- a large terminal cnidocyst cluster; 2 perradial mar- cal, with octagonal base; 2 opposite marginal capi- ginal bulbs without tentacles; manubrium conical tate tentacles, 6 non tentaculate bulbs; “gonads” 8, with quadrate base; mouth tubular; “gonads” irregu- perradial; short exumbrellar cnidocyst tracks above larly arranged perradially and interradially. each bulb. Velella velella (Linnaeus, 1758) Porpita porpita (Linnaeus, 1758) (Figs. 57J-K) (Figs. 57H-I) With the characters of the genus. With the characters of the genus. Records from Mediterranean: eastern and west- Records from Mediterranean: eastern and west- ern Mediterranean, Adriatic. ern Mediterranean, Adriatic. Known seasonality: 2-5. Known seasonality: 5-7; 10. Distribution: Atlantic; Indo-Pacific; Mediter- Distribution: Atlantic; Indo-Pacific; Mediter- ranean. ranean. References: Leloup (1929); Mackie (1959, References: Brinckmann-Voss (1970, 1987); 1960); Edwards (1963b, 1966a); Brinckmann-Voss Daniel (1976); Bouillon (1984d); Castelló i Tortella (1964, 1970, 1987); Daniel (1976); Larson (1980); (1986); Calder (1988); Pagès et al. (1992); Avian et Bouillon (1984d); Castelló i Tortella (1986); Calder al. (1995); Medel and López-González (1996); (1988); Pagès et al. (1992); Avian et al. (1995); Bouillon and Boero (2000). Medel and López-González (1996); Bouillon and Boero (2000). Genus Velella Lamarck, 1801 Family ROSALINDIDAE Bouillon, 1985 Hydroid: colony floating; float flattened, oval, elliptical, with a triangular sail; up to 40 mm long Hydroid: colonial; stolonal, with a Fig.-like or and 20 mm wide, higher in the centre than at the trabecular chitinized skeleton, consisting of a thin edges; two mirror images of the animal [left and perisarcal sheet covered by coenosarc and an exter- right sailing; the prevalence of one form in one nal peridemal film; coenosarc supported by perisar- region may be due to sorting by prevailing winds cal spines and trabeculae forming a more or less (Edwards, 1966a)]; float and sail kept rigid by a thick framework of meshes isolated or sometimes chitin support covered by mantle tissue; margin of organised in rose-like alveolar stuctures surrounding float soft and flexible; chitin float oval to slightly S- the polyps; hydranth plump sausage-shaped, with shaped with concentric air chambers; mantle tissue 30-60 scattered capitate tentacles, almost sessile, with network of endoderm canals; in centre of sometimes with a basal perisarcal calice; cnidome underside a single large gastrozooid or “siphon” comprising subspherical stenoteles and macrobasic encircled by a ring of medusa producing gastro- mastigophres; fixed gonophores or free medusae?, gonozooids and a peripheral band of dactylozooids; with two tentacles apparently provided with central feeding zooid broadly oval with an elongat- cnidophores, known in one species (Rosalinda nau- ed hypostome, without tentacles or medusa buds; movi), carried singly or on short pedicels among gastro-gonozooids spindle-shaped with a swollen proximal tentacles; cnidome stenoteles macrobasic mouth region, lacking tentacles but with warts of mastigophores and isorhiza. cnidocyst clusters concentrated in distal half; on proximal half of hydranth numerous medusa buds Genus Rosalinda Totton, 1949 growing in groups from short blastostyles; dactylo- zooids long and tapering, oval in cross section, with With the characters of the family.

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Rosalinda incrustans Kramp, 1947 bulbs and four cnidocyst exumbrellar pouches; (Figs. 58A-C) «gonads» surrounding manubrium; or medusae either Zanclea-like or with very elongated tentacular Colonies 3 mm in height, with simple trabecular bulbs bearing short tentacles armed with short and skeleton, with all hydranths naked. stiff cnidophores. Records from Mediterranean: western Mediter- Hydroid: stolonal, living in association with bry- ranean (Rosas Gulf). ozoans; polymorphic; gastrozooids reduced, without Known seasonality: 12 ? tentacles; hypostome armed or not with cnidocysts; Distribution: Atlantic, (west of Gibraltar), dactylozooids columnar, slender, usually with one or Mediterranean. two terminal cnidocyst knobs, sometimes with later- References: Vervoort (1966b); Watson (1978); al rows of cnidocysts as well, without mouth; repro- Antsulevich and Stepanjants (1985), Boero et al. duction by eumedusoids or free medusae. (1995); Bouillon and Boero (2000). Reference: Piraino et al. (1992).

Family ZANCLEIDAE Russell, 1953 Halocoryne epizoica Hadzi, 1917 (Figs. 58D-E) Hydroid: colonial; hydrorhiza creeping, stolonal; perisarc enveloping hydrocaulus and hydrorhiza not Hydroid: colonies stolonal, polymorphic, symbi- lamellar, as a simple tube; hydrocaulus unbranched; otic with bryozoans; hydrorhiza reticular, hydranths polyps monomorphic or polymorphic; gastrozooid naked, sessile; gastrozooids very thin, cylindrical, either with oral and aboral capitate tentacles, or with lacking tentacles but with two prominent ectodermal reduced capitate tentacles, or without tentacles; swellings containing stenoteles on opposite sides of gonozooid and dactylozooid, when present, varied the mouth; dactylo-gonozooids stouter than gastro- in expression. zooids, without mouth and tentacles, with a terminal Medusa: umbrella bell-shaped; 4 perradial exum- spherical cnidocyst cluster and up to five additional brellar cnidocyst pouches, either oval, clavate, elon- cnidocysts clusters along one side of the body or gate or linear, usually containing stenoteles; mouth arranged in a interrupted spiral towards hydrorhiza; simple, circular, without oral tentacles (except in released eumedusoids borne single or in clusters on Oonautes, of uncertain family affinity; see Capitata short pedicels on lower part of dactylo-gonozooids; incertae sedis); 4 radial canals (exceptionally bifur- cnidome: stenoteles of two sizes. cated in Ctenaria, of uncertain family affinity; see Medusa: eumedusoids; without mouth and tenta- Capitata incertae sedis); marginal tentacles 0, 2 or 4, cles; with 4 radial canals; with four perradial mar- hollow, each with numerous abaxial cnidophores, ginal bulbs; with four cnidocyst exumbrellar pouch- with macrobasic euryteles; “gonads” usually interra- es connected with marginal bulbs; gonads surround- dial, rarely in a single mass around manubrium; ing manubrium. Cnidome: stenoteles in exumbrel- without ocelli. lar, macrobasic euryteles (?) sometimes in exum- References: Wedler and Larson (1986); Calder brellar pouches, macrobasic mastigophores on (1988); Petersen (1990); Gravili et al. (1996); exumbrella. Schuchert (1996); Bouillon (1999); Bouillon and Records from Mediterranean: eastern and west- Barnett (1999); Boero et al. (2000); Bouillon and ern Mediterranean, Adriatic. Boero (2000). Known seasonality: 4-6? Distribution: endemic of Mediterranean Sea. Key to hydroids References: Piraino et al. (1992); Avian et al. (1995); Boero et al. (2000). 1. Gastrozooid reduced, without tentacles ...... Halocoryne Genus Zanclea Gegenbaur, 1857 – Gastrozooid with numerous tentacles ... Zanclea Hydroid: colonial, stolonal hydroids, often asso- Genus Halocoryne Hadzi, 1917 ciated with bryozoans or molluscs; hydranths monomorphic or polymorphic. Polymorphic Either eumedusoids with no tentacles and no colonies may present gastrozooids, dactylozooids, mouth; with 4 radial canals; with four perradial tentaculozooids and sometimes gastro-gonozooids;

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gastrozooids on unbranched short pedicels, often – Apotrichous macrobasic euryteles ...... almost sessile, elongated, cylindrical or claviform ...... Z. giancarloi with an oral whorl of capitate tentacles and numer- ous aboral capitate tentacles scattered or in several Zanclea costata Gegenbaur, 1857 whorls over the entire body; tentacles rarely reduced (Figs. 59A-D) to mere cnidocyst patches; perisarc covering hydro- hiza and entire hydrocaulus or confined to lower Hydroid: hydrorhiza on margin of bivalve shell; part of hydrocaulus only; dactylozooids and tentac- pedicel covered by corrugated to annulated perisarc; ulozooids when present varied in expression; hydranths cylindrical, with an oral whorl of 4-6 ten- medusa buds carried singly or in clusters on short tacles and about 40-60 capitate aboral tentacles scat- pedicels, either scattered among or under the aboral tered over entire hydranth body; medusa buds tentacles or on hydrorhiza or on hydranths reduced between tentacles in the mid-upper part of hydranth. to blastostyles . Cnidome: Stenoteles of two sizes in tentacle capita- Medusa: Zancleidae with bell-shaped or almost tions; holotricous macrobasic euryteles with a shaft spherical umbrella, lateral walls evenly thin, coiled spirally along the main axis of undischarged mesoglea slightly thicker at the apex; with exum- capsules, abundant in hydrorhiza and rare in brellar perradial cnidocyst patches or tracts; mouth hydranth body; microbasic mastigophores rare in simple, circular; with 4 simple radial canals; mar- hydranth and hydrorhiza. ginal tentacles when present, 0, 2 or 4, with numer- Medusa: see diagnosis as for the genus. ous abaxial cnidophores; «gonads» interradial; Records from Mediterranean: Ionian coast of cnidome generally with stenoteles and macrobasic Apulia. euryteles, without desmonemes, no ocelli. Known seasonality: 1-7. The genus Zanclea comprises at least 3 species in Distribution: Mediterranean, all other records the Mediterranean, Zanclea costata, Zanclea sessilis have to be confirmed on basis of hydroid cnidome and Zanclea giancarloi (Gravili et al., 1996; Cerra- studies. no et al., 1997; Boero et al., 2000). References: Medel and López-González (1996); Most of the various existing Zanclea species are Cerrano et al. (1997); Boero et al. (2000). actually not identifiable without a detailed study of the structure of the macrobasic euryteles cnidocysts Zanclea giancarloi of the polyp stage and the knowledge of their com- Boero, Bouillon and Gravili, 2000 plete life cycle, the medusae are usually indis- (Figs. 59E-I) cernible and must be referred as Zanclea spp. (Figs. 58F-H). Hydroid: hydrorhiza reticular, growing under the General references: Russell and Rees (1936); skeleton of the bryozoan host; hydranths elongated, Brinckmann-Voss (1970,1987); Benovic and Bender cylindrical, with a whorl of four-eight oral capitate (1987); Goy (1973b); Millard and Bouillon (1973); tentacles and 50-60 aboral capitate tentacles scat- Bouillon (1974a); Gili (1986); Goy et al. (1988, tered over the whole hydranth body; hypostome 1990, 1991); Calder (1992); Boero and Bouillon whitish, hydranth transparent; gastric wall pink- (1993); Avian et al. (1995); Benovic and Lucic salmon; pedicel covered by slightly corrugated (1996); Gravili et al. (1996); Medel and López- brownish perisarc; medusa buds in clusters among González (1996); Cerrano et al. (1997); Boero et al. tentacles in the lower third of the hydranth. (2000). Cnidome: stenoteles of two sizes in tentacle capita- tions; apotrichous macrobasic euryteles of two sizes, Key to hydroids both with shaft coiled along the long axis of capsule, the larger ones with spines for one fifth of their 1. Apotrichous macrobasic euryteles with shaft length when extruded, the smaller ones with spines coiled in a horse-shoe shape in undischarged for one tenth of their length, both present in capsules...... Z. sessilis hydrorhiza and hydranth body. – Macrobasic euryteles with a spirally coiled shaft Medusa: see diagnosis as for the genus. along long axis of the capsules in undischarged Records from Mediterranean: Ionian Sea. capsules ...... 2 Known seasonality: 6-9. 2. Holotrichous macrobasic euryteles .... Z. costata Distribution: endemic to Mediterranean Sea.

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References: Gravili et al. (1996); Boero et al. species presently include in this subclass, Kantiella (2000). enigmatica and Laingia jaumotti present medusa budding with formation of a medusary nodule. This Zanclea sessilis (Gosse, 1853) character and the presence of marginal tentacular (Figs. 59J-M) bulbs allow their inclusion in the Hydroidomedusa. They present a mosaic of characters of Narcome- Hydroid: hydrorhiza reticular, covered by the dusae and Hydroidomedusa, more information bryozoan skeleton in the central part of the colony about their life cycle are needed to ascertain their and unrecovered at its margin; pedicel short; peris- affinities with the other subclasses. arc thin, encrusted by sediment particles, not annu- References: Pagès et al. (1992); Bouillon (1999); lated, whitish, hydranth column cylindrical; four-six Bouillon and Barnett (1999); Bouillon and Boero oral capitate tentacles, 20-40 aboral capitate tenta- (2000). cles, scattered on the distal half or three quarters of hydranth column; hypostome milk white, column Family LAINGIIDAE Bouillon, 1978c transparent, with reddish gastric wall; medusa buds in clusters, growing below the tentacled part of the Laingiomedusae with umbrella divided by pero- hydranth, fertile hydranths gradually decreasing in nial grooves or similar structures so that umbrellar size and tentacle number. Cnidome: apototrichous margin is lobed; four radial canals; no typical circu- macrobasic euryteles with shaft coiled in a horse- lar canal but a solid core of endodermal cells around shoe shape, disposed in circle in between oral tenta- umbrella margin; tentacles solid, inserted on the cles and in hydrorhiza, rare in hydranth column; exumbrellar surface above bell margin; alternating stenoteles of two sizes in tentacle capitations. with the tentacles there may be narrow exumbrellar Medusa: see diagnosis as for the genus. cnidocyst bands or triangular ciliated fields; Records from Mediterranean: coast of Apulia. manubrium simple quadrangular, tubular or conical; Known seasonality: 2-3. mouth opening quadrangular to circular; «gonads» Distribution: Mediterranean, all other records in four masses on the manubrium or as epidermal have to be confirmed on basis of hydroid cnidome lining of interradial pockets of the manubrium; mar- studies. ginal sense organs apparently missing. Cnidome References: Medel and López-González (1996); include macrobasic mastigophores or macrobasic Boero et al. (2000). euryteles. Sexual reproduction unknown.

Subclass LAINGIOMEDUSAE Bouillon, 1978 1. With exumbrellar cnidocyst bands; marginal tentacular bulbs largely separated from marginal Hydroid: unknown. circular strand ...... Kantiella Medusa: umbrella almost hemispherical, margin – Without exumbrellar cnidocysts bands but with lobed, divided by peronial grooves or similar struc- interradial ciliated fields; marginal bulbs only tures; 4 radial canals; no typical circular canal but a somewhat displaced towards exumbrella...... solid core of endodermal cells around umbrella mar- ...... Fabienna gin; tentacles solid, inserted on exumbrellar surface above margin; tentacular bulbs in contact or not with Genus Fabienna Schuchert, 1996 the endodermal circular core; alternating with the tentacles there may be narrow exumbrellar cnido- Laingiidae with slightly lobed umbrella margin; cyst bands or triangular ciliated fields; manubrium with four perradial tentacles that have their origin simple, quadrangular, tubular or conical; mouth somewhat displaced towards the exumbrella; inter- opening simple, quadrangular to circular; “gonads” radial triangular ciliated fields; larger cnidocysts in 4 masses on the manubrium or as epidermal lin- confined to tentacle tips in one terminal cluster ing of interradial pockets of the manubrium; mar- immediately followed proximally by an adaxial ginal sense organs apparently missing; cnidome: cluster; the two clusters may fuse in older individu- macrobasic mastigophores or macrobasic euryteles. als; cnidome includes macrobasic euryteles; Sexual reproduction unknown. «gonads» develop on manubrium only, in an interra- Remark: The Laingiomedusae represent the dial position. smallest group of Hydroidomedusa, two of the four Hydroid: unknown.

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Fabienna oligonema (Kramp, 1955) chitinous perisarcal structure of definite shape: (= Pochella oligonema) (Fig. 60A) hydranth with hydrotheca, nematophore with nema- totheca and gonophores with gonotheca. Rarely with Medusa: umbrella 2 mm wide and high, naked hydranths. mesoglea thick; with interradial triangular ciliated Medusa: flatter than bell-shaped, typically with fields; with very broad gastric peduncle; manubrium hemispherical or flattened umbrella; “gonads” con- cruciform; mouth with four simple inconspicuous fined to radial canals, exceptionally extending onto lips; «gonads» interradial, oval, cushion-like; 4 sim- the proximal part of manubrium; marginal sense ple radial canals; 4 perradial marginal tentacles with organs, when present, in form of ectodermal velar cnidocysts in a terminal cluster and a adjacent clus- statocysts, rarely cordyli, occasionally adaxial ocel- ter, fused in adults. li; marginal tentacles peripheral and hollow (except Records from Mediterranean: eastern Mediter- in Obelia), with tentacular bulbs; cnidome: often ranean. microbasic mastigophores and merotrichous Known seasonality: 8; 9; 12. isorhizae. Reproduction through a complex planula Distribution: Atlantic; Mediterranean. stage with cnidoblasts, interstitial cells, neural cells References: Kramp (1961); Goy et al. (1988, and usually two types of embryonic glandular cells. 1990, 1991); Dowidar (1983); Boero and Bouillon (1993); Schuchert (1996). Order CONICA Broch, 1910

Genus Kantiella Bouillon, 1978 Hydranth with a simple, generally conical or rounded-conical hypostome, without a “buccal cav- Laingiidae with exumbrellar cnidocyst bands; ity” beneath mouth opening; medusa varied in «gonads» on walls of four manubrial interradial expression. pouches; 4 short marginal tentacles with terminal cluster of cnidocysts, above peronia-like structures. Key to hydroids Hydroid: unknown. 1. Hydranth naked, without intertentacular Kantiella enigmatica Bouillon, 1978 membrane...... Melicertidae (Figs. 60B-C) – Hydranth typically with hydrotheca (when exceptionally naked, i.e. Eirenidae, with Medusa: umbrella 3-4 mm wide, 2-3 mm high, intertentacular membrane)...... 2 hemispherical, mesoglea thick at apex; exumbrella 2. Hydrothecae with operculum ...... 3 with 4-8 exumbrellar cnidocyst bands; with short – Hydrothecae without operculum ...... 8 and broad gastric peduncle; manubrium quadrangu- 3. Hydrothecae generally bilaterally symmetrical; lar; mouth margin quadrate or circular, without usually with marginal teeth ...... 4 marked lips, mouth rim covered by cnidocysts; with – Hydrothecae radially symmetrical; without true 4 simple radial canals with virtual cavity, no real cir- marginal teeth...... 5 cular canal but a solid marginal endodermic core; 4 4. Hydrothecae generally pedicellate; usually with short marginal tentacles with terminal cluster of annular perisarcal diaphragm; hydranths with a cnidocysts, inserted above peronia-like structures; basally annular ectodermal fold ...... «gonads» on interradial expansions of manubrium; ...... Thyroscyphidae with medusa buds on manubrium. – Hydrothecae generally sessile adnate; with Records from Mediterranean: eastern Mediterranean. diaphragm in few pedicellate forms, others Seasonality: ? having an eccentric hydropore; in some species Distribution: Indo-pacific; Mediterranean. with an abcauline gastric caecum and mantle References: Bouillon (1978a, c ; 1985); Goy et (ectodermal lamella); without a basally annular al. (1988, 1990, 1991). ectodermal fold ...... Sertulariidae 5. Operculum of two pleated membranes meeting Subclass LEPTOMEDUSAE Haeckel, 1866 (1879) one another like a gabled roof...... Tiarannidae Hydroid: as “Thecata” hydroids; all parts of – Operculum of 4 or more valves sharply or not colony typically surrounded and protected by a rigid sharply demarcated from hydrothecal wall...... 6

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6. Hydrothecae sessile; all medusa families with nematothecae present or absent...... 14 pleated or segmented operculum and with “Cus 14.Colonies usually stolonal; hydrothecae pidella-like” colonies...... pedicellate; either with an annular perisarcal ..... Campanulinidae in part; Cirrholovenellidae, thickening and membranous diaphragm or thick ...... Laodiceidae, Mitrocomidae, Tiaropsidae. diaphragm an no annular thickening; gonophores – Hydrothecae pedicellate = all the medusa as swimming sporosacs, eumedusoids or free families with pleated or segmented operculum medusae, gonothecae single...... Hebellidae with “Campanulina-type” of hydroids ...... 7 – Colonies usually erect; hydrothecae with or 7. Hydranth without intertentacular web without pedicel, with or without diaphragm; ...... Campanulinidae in part; without annular perisarcal thickening; ...... Lovenellidae, Phialellidae gonophores as fixed sporosacs, gonothecae – Hydranth with intertentacular web...... aggregated, exceptionally single or in pairs...... Aequoreidae; Blackfordiidae; ...... Lafoeidae ...... Campanulinidae in part Eirenidae; ...... Lovenellidae, Malagazziidae Key to medusae 8. Hydrothecae saucer shaped or basin-shaped, usually to small to contain contracted hydranth . 1. Without statocysts or cordyli...... 2 ...... Haleciidae – With statocysts or cordyli...... 3 – Hydrothecae usually deep enough to contain 2. With large, broad, gastric peduncle, with contracted hydranth ...... 9 numerous filiform, solid tentaculiform structures 9. Hydrothecae always restricted to one side of without marginal bulbs and not in connection stem or branches; nematophores present in with circular canal, with numerous ocelli ...... regular arrangement, usually 3-5 per hydrothecae ...... Orchistomatidae ...... 10 – Gastric peduncle absent or very weakly – Hydrothecae on two or more sides of stem or developed, without marginal tentaculiform branches; nematophores if present seldom structures, rarely with ocelli; with base of regularly arranged ...... 13 manubrium attached over its whole surface...... 10.`Paired lateral nematothecae present and fused ...... Melicertidae to hydrothecae...... Aglaopheniidae 3. With cordyli or cordyli like structures ...... 4 – Paired lateral nematothecae present or absent, – With statocysts...... 7 when present not fused to hydrothecae...... 11 4. Manubrium with 4 perradial lobes connected 11.Paired lateral nematothecae absent; median with subumbrella; with cordyli like structures; nematothecae usually reduced and seldom two- «gonads» on manubrium and extending on chambered...... Kirchenpaueriidae perradial lobes ...... Tiarannidae – Paired lateral nematothecae present; – Manubrium without perradial lobes...... 5 nematothecae usually two-chambered ...... 12 5. With cordyli like structures; gonads elongated 12.Hydrocladia arising from erect stem; no cauline forming linear sacs on radial canals, separated ...... hydrothecae; hydrocauli when polysiphonic from manubrium; with or without open giving rise to hydrocladia from a single axial statocysts ...... Teclaiidae tube...... Plumulariidae – With cordyli...... 6 – Hydrocladia arising from erect main stem or 6. With 4 or 8 simple radial canals..... Laodiceidae directly independently from hydrorhiza; stem or – With 4 or more branched radial canals ...... branches either with cauline hydrothecae or fas ...... Hebellidae cicled and giving rise to hydrocladia or pinnae 7. With open statocysts...... 9 from any of its component tubes...... – With closed statocysts ...... 8 ...... Halopterididae 8. With closed statocysts and adaxial ocelli...... 13.Hydrotheca with a definite floor always sessile ...... Barcinidae and bilaterally symmetrical, no nematothecae.... – With closed statocyst and without ocelli...... 10 ...... Syntheciidae 9. Open statocyts associated with ocelli...... – Hydrothecae with no definite floor; with or ...... Tiaropsidae without diaphragm hydrothecae sessile or – Open statocysts without ocelli..... Mitrocomidae pedunculate bilaterally or radially symmetrical, 10.With distinct gastric peduncle; with 8 or many

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statocysts ...... Eirenidae based nominal species of Aequorea have neverthe- – Without distinct gastric peduncle...... 11 less been described; their medusae, however, might 11.Manubrium very broad; with many (more than have been known since a long time and they could eight) radial canals; tentacle bulbs with be junior synonyms for instance: Aequorea africana excretory pores on or not on excretory papillae . Millard, 1966; Aequorea philippina Watson, 1998...... Aequoreidae References: Russell (1970b); Pagès, Gili and – Manubrium narrow; with normally 4-8 radial Bouillon (1992); Watson (1998); Bouillon (1999); canals...... 12 Bouillon and Barnett (1999); Bouillon and Boero 12.Tentacle bulbs with excretory pores, 4-8 radial (2000). canals (sometimes 12)...... Malagazziidae – Tentacle bulbs without excretory pores ...... 13 Key for the medusae 13.Tentacle bulbs with lateral cirri..... Lovenellidae – Tentacle bulbs without lateral cirri...... 14 1. Radial canals branched or bifurcated ...... 14.Exumbrella with marginal cirri ...... Zygocanna ...... Cirrholoveniidae – Radial canals simple, undivided ...... Aequorea – Exumbrella without marginal cirri...... 15 15.«Gonads» divided in two lateral parts separated Genus Aequorea Péron and Lesueur, 1810 by a median groove; 8 marginal statocysts ...... Phialellidae Hydroid: when known, with the characters of the – «Gonads» completely surrounding radial canals; family. The hydroids are inadequate for diagnosis 8 or more statocysts...... 16 (see above) (Figs. 61A-D). 16.Endodermal core of tentacles extending inwards Medusa: Aequoreidae with numerous simple from bell margin into bell mesoglea ...... radial canals; subumbrella without rows of gelati- ...... Blackfordiidae nous papillae. – No endodermal tentacular expansions ...... Campanulariidae (see under Proboscoida) Key to medusae

Family AEQUOREIDAE Eschscholtz, 1829 1. «Gonads» no more than half as long as radial canals...... A. conica Hydroid: of “campanulinid” type; colony stolon- – «Gonads» along almost whole length of radial al or erect, when erect only sparingly and sympodi- canals...... 2 ally branched; hydrotheca delicate, tubular, elongat- 2. About 4-10 or more times as many radial canals ed, radially symmetrical, operculum as a continua- as tentacles...... A. pensilis tion of hydrothecal wall, formed by several triangu- – With at least half as many tentacles as radial lar convergent folds continuing downwards nearly canals...... A. forskalea to base of hydrotheca and not delimited by crease- line; in older colonies operculum generally lost, Aequorea conica Browne, 1905 hydrotheca reduced to a perisarcal collar, acquiring (Fig. 60D) a haleciid shape; hydranth contractile, with interten- tacular web, tentacles amphicoronate, moniliform- Medusa: umbrella 9 mm wide, 10-12 mm high, like when completely extended; gonothecae pedicel- conical, with very thick mesoglea; manubrium half late, very large, cylindrical, giving rise to one rarely as wide as umbrella diameter, often broad and flat; to two medusae. mouth with long and slender lips with inward furrow Medusa: manubrium very wide, circular; usually which continues along inside of manubrium to radi- no gastric peduncle; many simple or branched radi- al canals; about 16 radial canals, twice as many ten- al canals; “gonads” on radial canals, separated from tacles (20-30), and as many small bulbs, both with- manubrium; marginal tentacles hollow; usually with out excretory papillae or pores; about twice as many excretory pores or papillae; no marginal or lateral statocysts as tentacles; «gonads» laterally com- cirri; statocysts closed; no ocelli. pressed, in proximal half of radial canals. Remark: without knowledge of life cycle, the Records from Mediterranean: eastern Mediter- hydroids of Aequorea are inadequate for species ranean. diagnosis (see Cornelius, 1995); some hydroid- Known seasonality: 6.

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Distribution: Indo-Pacific; Mediterranean. tary bulbs; tentacle bulbs with long lateral exten- References: Kramp (1961); Goy et al. (1988, sions, no abaxial keel; without excretory papillae 1990, 1991); Boero and Bouillon (1993). but excretory pores present as slits; statocysts very Hydroid: unknown. numerous. Hydroid: unknown. Aequorea forskalea Péron and Lesueur, 1810 Records from Mediterranean: ? (Figs. 60E-F, 61A-D) Seasonality: ? Distribution: Atlantic; Indo-Pacific, Mediter- Hydroid: colonies minute, stolonal with single or ranean? slightly branching erect hydrocauli which are imper- References: Russell (1953); Kramp (1961); fectly annulated or spirally grooved throughout their Boero and Bouillon (1993). length; hydrothecae cylindrical, with a long conical folded operculum tapering to a fine sharp point, the Genus Zygocanna Haeckel, 1879 folds continuing as striations of perisarc downwards nearly to base of hydrotheca, hydrothecal base at right Medusa: Aequoreidae with numerous radial angles to lateral walls; hydranths very extensile, with canals, branched or bifurcated; exumbrella some- about 20 amphicoronate filiform oral tentacles united times with radial rows of gelatinous papillae. at their base by a prominent intertentacular membra- Hydroid: unknown. nous web; gonothecae very large and cylindrical, blunt-ended, arising from hydrocaulus on short Zygocanna vagans Bigelow, 1912 imperfectly annulated stems just below hydranths and (Figs. 61G-H) containing one rarely two medusa buds. Medusa: umbrella large, up to 175 mm wide, Medusa: umbrella up to 76 mm wide, flat, thin, saucer-shaped, thick in centre, gradually thinning but of hard consistency; exumbrella with radial towards margin; manubrium half as wide as umbrel- bands of gelatinous papillae alternating with radial la; radial canals usually 60-80, sometimes fewer or canals; velum broad; manubrium occupying 1/3-1/2 up to 160; «gonads» along almost whole length of of umbrellar diameter, roof of the manubrium pre- radial canals; tentacles generally fewer than radial senting a cruciform structure bifurcating two or four canals but varying from half to twice as many; ten- times before reaching the manubrium periphery tacle bulbs elongate, conical; small bulbs few, scat- where the bifurcations give rise to about 30-45 non tered; excretory pores on short papillae; 5 -10 stato- branched radial canals; mouth with crenulated lips; cysts between successive radial canals. «gonads» extending along greatest part of radial Records from Mediterranean: eastern and west- canals without reaching the umbrella margin; 28-70 ern Mediterranean; Adriatic. tentacles and several small rudimentary bulbs, with Known seasonality: 1-12. long excretory papillae; statocysts very numerous. Distribution: Atlantic; Indo-Pacific, Mediter- Records from Mediterranean: Adriatic Sea. ranean. Known seasonality: 10. References: Rees, 1938; Babnik (1948); Russell Distribution: Atlantic; Indo-Pacific; Mediter- (1953); Kramp (1961); Berhaut (1970); Goy (1973b); ranean. Brinckmann-Voss (1987); Gili (1986); Goy et al. References: Babnik (1948) as Zygocanna. sp.; (1988, 1990, 1991); Boero and Bouillon (1993); Cor- Boero and Bouillon (1993); Avian et al. (1995). nelius (1995); Avian et al. (1995); Benovic and Lucic (1996); Medel and López-González (1996). Family AGLAOPHENIIDAE L. Agassiz, 1862

Aequorea pensilis (Eschscholtz, 1829) Hydroid: colony upright, mono- or polysiphonic, (Figs. 61E-F) branched or unbranched, arising from creeping hydrorhiza or from anchoring filaments; hydrocla- Medusa: umbrella up to 100 mm wide, more or dia alternate or opposite in one plane, or arranged less biconvex, with thin margin; manubrium 1/2-2/3 spirally; hydrothecae uniseriate, usually completely as wide as umbrella; «gonads» extending along adnate, margin usually cusped, with or without almost entire length of manubrium; 150-250 radial intrathecal septum, absent from hydrocaulus except canals; 10-16 tentacles and as many small rudimen- in basal most segment; nematophores with nema-

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tothecae, not as naked sarcostyles; nemathothecae at hydrocladia, typically more or less cone to sac- least partially fused to hydrothecae, one-chambered shaped, margin usually deeply toothed; intrathecal (monothalamic) and immovable; hydrotheca typi- septum variably developed; each hydrotheca cally flanked by three nematohtecae (five in some flanked typically by a pair of lateral nematothecae species of Aglaophenia and sometimes in Cladocar- and a partly to wholly adnate, median inferior nema- pus), usually with one pair of lateral nematothecae, totheca sometimes a pair of median superior nema- and with an unpaired median inferior nemathotheca tothecae; gonothecae aggregated, enclosed within a that may be doubled or have two terminal apertures; corbula formed by modified hydrocladia bearing sometimes also a pair of superior nematothecae; alternately inserted secondary ribs with nematothe- gonothecae lacking nematothecae, unprotected, or cae and lacking basal hydrothecae, corbula ribs surrounded by recurved branches in phylactocarp, or fused or not; as fixed sporosacs, or released swim- nearly completely enclosed within corbula both ming gonophores. richly provided with nematothecae; fixed sporosacs Remark: Von Lendenfeld (1884) created Pentan- or swimming gonophores. dra to accommodate P. balei and P. parvula, with 5 References: Svoboda (1979); Svoboda and Cor- nematothecae surrounding the hydrothecae: one nelius (1991); Cornelius (1995); Migotto (1996); median inferior, two lateral and a pair of superior Calder (1997); Calder and Vervoort (1998); Watson (see diagnoses and Fig. 16 by Von Lendenfeld, (2000); Ansín Agís et al. (2001); Schuchert (2001a, 1884), the last pair having been treated by many 2003). authors as a supplementary pair of lateral nema- tothecae! Bedot (1921) listed a series of genera and Key to hydroids species showing deviations in numbers to the typi- cally three hydrothecal nematothecae and stated that 1. Gonotheca unprotected ...... Gymnangium there was no need to create new genera for such – Gonotheca protected in corbula or in variations. We agree with his conclusions and con- phylactocarp ...... 2 sider Pentandra as congeneric with Aglaophenia. 2. Gonotheca protected in corbula replacing References: Svoboda and Cornelius (1991); hydrocladia with secondary ribs ...... 3 Ramil and Vervoort (1992a); Cornelius (1995); – No true corbula, gonotheca solitary and Calder (1997). protected by branched or unbranched phylactocarps...... 4 1. Stems without any basal prosegment ...... 3. Corbula ribs comprising nematothecae and ...... A. picardi hydrothecae...... Lytocarpia – Stems with one or more basal prosegment ...... 2 – Corbula comprising only nematothecae...... 2. Hydrotheca with a greatly developed transverse ...... Aglaophenia abcauline septum recurved at the tip...... 4. Phylactocarps formed by a modified ...... A. kirchenpaueri hydrocladium, single or aggregated into – Hydrotheca without this character ...... 3 pseudo-corbulae...... Macrorhynchia 3. Free part of mesial nematotheca long, usually – Phylactocarps arising as appendages of an much longer than the free part of abcauline wall, unmodified hydrocladium ...... 5 and directed away from hydrotheca ...... 5. Hydrocladia arranged in a spiral around stem ...... A. tubulifera ...... Streptocaulus – Mesial nematotheca without this character...... 4 – Hydrocladia arranged in two longitudinal rows.. 4. Coenosarc with zooxanthellae; perisarc of stem, ...... Cladocarpus hydrocladia and corbulae yellowish to brown . 5 – Coenosarc without zooxanthellae; perisarc of the Genus Aglaophenia Lamouroux, 1812 stem, hydrocladia and corbulae not with a same = Pentandra von Ledenfeld, 1884 colour...... 6 5. Colonies growing only on Sea grasses, stem Hydroid: colony erect, hydrocaulus branched or sometimes with intersegments; hooked apical unbranched, monosiphonic or polysiphonic, arising stolons in summer ...... A. harpago from creeping hydrorhiza or anchoring filaments; – Colonies growing in different substrates, without hydrocladia unbranched, pinnately arranged, arising intersegments neither hooked apical stolons...... from alternate apophyses; hydrothecae only on ...... A. tubiformis

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6. Hydrotheca with the adcauline intrathecal Records from Mediterranean: eastern and west- septum long; hydrotheca usually narrowed ern Mediterranean. basally, shape triangular more than tubular ..... 7 Known seasonality: 1-12. – Hydrotheca with the adcauline intrathecal Reproduction: 1, 2, 4-8, 12. septum usually short or absent; hydrotheca Distribution: northern Atlantic (east and west), tubular...... 8 Mediterranean. 7. Rim with non-uniform cusps, in side view mesial References: Fraser (1944); Svoboda (1979); Svo- cusp inclined toward lumen; second pair of cusps boda and Cornelius (1991); Boero and Bouillon bifid ...... A. parvula (1993); Avian et al. (1995); Cornelius (1995); – Rim with uniform cusps; second pair of cusps Medel and Vervoort (1995); Medel and López- single...... A. octodonta González (1996); Ansín Agís et al. (2001); Peña 8. Mature cormoid comprising one or many plumes Cantero and García Carrascosa (2002). branched or unbranched ...... 9 – Mature cormoid comprising a single and Aglaophenia elongata Meneghini, 1845 unbranched plume ...... A. lophocarpa (Figs. 62E-G) 9. Branching dichotomous ...... A. pluma – Branching trichotomous or irregularly bifid .. 10 Hydrocauli monosiphonic, up to 300 mm high, 10.Ramus arising from apical end of a segment with pinnate and branched, closely grouped. Axis brown- prosegments, comprising several roughly ish, basally with 1-4 prosegment, nodes oblique. normally arranged cormidia...... A. acacia Remainder internodes each bearing three nematothe- – Ramus always arising from a normal caulus cae and one abortive hydrothecae (pseudonematothe- segment which has one normally developed cae); nodes indistinct. Branches arising between cladium...... A. elongata mesial, proximal nematothecae and cladium or corbu- la, with 1-3 prosegment basally. Ramus and cladium Aglaophenia acacia Allman 1883 of same internode aligned parallel with each other; up (Figs. 62A-D) to 4th order of branching. Hydrocladia yellow, alter- nate, spaced on stem, cormidia with one hydrothecae Colonies pinnate (up to ca 200 mm), stems grouped and three gutter-shaped nematothecae. Hydrotheca closely, monosiphonic and branched; axis brown, athe- narrow and deep (length/breadth ratio: 1.7-2.5), rim cate basally, followed by a prosegment; remainder parts with 9 uniform cusps; adnate mesial nematotheca thecate, nodes oblique; internodes of the axis with three reaching 1/3-1/2 of the hydrotheca, free end short. Lat- nematothecae and an abortive hydrotheca (pseudone- eral nematothecae slightly above hydrothecal rim. matotheca). Major branches (rami) widely spaced on Male and female corbulae in different colonies. Cor- stem, typically paired, or one of a pair replaced by a bulae short, yellowish to white, 4-6 pairs of ribs fused corbula; at point of branching, caulus bending back ver- in female, with slits in male; free costa absent. sally resulting in a trichotomous arrangement. Sec- Hydranth very large with usually long tentacles. ondary hydrocauli with some of the basal internodes Records from Mediterranean: western and east- without hydrocladia, but with cormidia almost similar ern Mediterranean, Adriatic. to those of the hydrocladia; however, the mesial nema- Known seasonality: 1,;4,;7-11. totheca is placed on the lower part of the internode, Reproduction: 4;6-11. without contact with the abcauline hydrothecal wall. Distribution: widely reported around the world Hydrocladia white, alternate, closely set, one cormidi- but records outside Mediterranean seem erroneous um per internode, nodes transverse; hydrotheca narrow (Svoboda and Cornelius, 1991). and deep (length/breadth ratio: 1-2), rim with 9 shallow References: Svoboda (1979); Svoboda and Cor- cusp, outermost longest; intrathecal ridge short; mesial nelius (1991); Boero and Bouillon (1993) Avian et al. nematotheca short, reaching half length of hydrothecal (1995); Peña Cantero and García Carrascosa (2002). abcauline wall, 1/3 of the nematothecae free; aperture gutter shaped; lateral nematothecae surpassing Aglaophenia harpago von Schenck, 1965 hydrothecal rim, slightly swollen. Male and female cor- (Figs. 62H-K) bula white, with the costae completely fused, male without free costa; female sometimes first/last rib on Hydrorhizae growing only along sea grass blade. each side free. Well developed monosiphonic hydrocauli brown, up

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to 18 mm, bending backwards; one prosegment Records from Mediterranean: western Mediter- basally separated by very deep oblique furrows, ranean as far east as Adriatic Sea. which allow bending in response to current surge; Known seasonality: 1-12. remainder parts of the axis composed of segments Reproduction: 2; 4-11. bearing one pseudonematothecae and three nema- Distribution: northeastern Atlantic from British tothecae gutter shaped; nodes slightly oblique; in coasts to Cape Verde Islands; Mediterranean. some stems, intermediate segments with frontal References: Patriti (1970); Svoboda (1979); Svo- nematothecae occurs distally, between hydrocladia- boda and Cornelius (1991); Ramil and Vervoort bearing segments. Caulus ended by thick, narrow (1992a); Boero and Bouillon (1993); Cornelius hook may occurs specially in spring and summer. (1995); Medel and Vervoort (1995); Medel and Coenosarc of the colony with zooxanthellae. Hydro- López-González (1996); Ansín Agís et al. (2001); cladia brown, more spaced than in other Aglaophe- Peña Cantero and García Carrascosa (2002). nia species; cormidia with one hydrothecae and three nematothecae. Hydrothecae may vary from Aglaophenia lophocarpa Allman, 1877 long and narrow in some colonies to wider and (Figs. 63E-H) shorter in other ones (length/breadth ratio: 1.8, -1.4). Colonies dioecious, corbulae brown, short, 4-6 pairs Hydrocauli pinnate, up to ca 50 mm, monosi- of ribs fused in female, partly open in male. phonic and unbranched; colour brown. Axis basally Records from Mediterranean: eastern and west- with 1-3 prosegment with frontal nematothecae sep- ern Mediterranean, Adriatic. arated by transverse nodes; remainder parts with Known seasonality: 2, 3, and 5, 6, 8, 9. internodes bearing hydrocladia; each with one Reproduction: 3-7. pseudonematothecae and three nematothecae; nodes Distribution: endemic of Mediterranean Sea. indistinct. Hydrocladia widely spaced on stem; References: Svoboda (1979); Gili (1986); Roca hydrothecae narrow and deep (length/breadth at rim: (1986); Svoboda and Cornelius (1991); Boero and 1.7-2.1), rim with 9 uniform cusps; short intrathecal Bouillon (1993); Avian et al. (1995); Medel and septum in lower third of hydrothecae; adnate part of López-González (1996). mesial nematotheca reaching the middle of hydrotheca, free part short, foramen into hydrothe- Aglaophenia kirchenpaueri (Heller, 1868) cae usually open; lateral nematothecae reaching the (Figs. 63A-D) hydrothecal rim or slightly overtopping. Colonies dioecious; female corbulae brown, ribs fused; male Hydrocauli pinnate, up to 200 mm high yellow- white, ribs usually with slits between nematothecae, ish to brown, monosiphonic and unbranched; basal but fused ribs may occurs. part of the axis athecate, followed by up to three Records from Mediterranean: western and east- prosegments, each with a frontal nematotheca. ern Mediterranean, Adriatic. Remainder internodes with three nematothecae and Known seasonality and reproduction: 4-9. a pseudonematotheca; nodes oblique. Hydrocladia Distribution: tropical eastern Atlantic (Azores, yellow or brown, alternate, closely set; cormidia Guinea Bissau); Caribbean; Mediterranean. each with one hydrothecae and three nematothecae References: Svoboda (1979); Gili, Vervoort and (one median inferior and two laterals); nodes trans- Pagès (1989); Svoboda and Cornelius (1991); Ramil verse. Hydrotheca not deep (length/breadth at rim: and Vervoort (1992a); Boero and Bouillon (1993); 1-1.3), with a greatly developed transverse Ansín Agís et al. (2001). abcauline septum recurved at the tip; rim with 9 marginal cusps, first pair on both sides longest, Aglaophenia octodonta (Heller, 1868) remainder marginal cusps grading towards axis of (Figs. 63I-L) cormidium. Median nematothecae not surpassing hydrothecal rim, 2/3 adnate, aperture gutter-shaped. Hydrocauli monosiphonic, yellowish to brown Lateral nematothecae projecting slightly above and unbranched. Axis basally, with several transverse hydrothecal rim; distal portion curved outwards, nodes and with 1-3 prosegments separated by oblique aperture gutter-shaped. Corbulae yellow or brown, nodes; remainder parts composed of hydrocladia male partially open, usually without free costae; bearing internodes, with three gutter-shaped nema- female usually closed and with free costa. tothecae and a pseudonematothecae; nodes oblique.

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Hydrocladia transparent to yellowish, closely alter- Distribution: eastern Atlantic; S Australia, nate; cormidia separated by transverse nodes. Mediterranean?. Hydrothecae not deep (length/breadth at rim: 1.1- References: Millard (1975) as A. pluma parvula; 1.4), narrowing basally and thus of triangular shape; Ramil (1988); Gili et al. (1989); Svoboda and Cor- rim with 9 uniform cusps; adcauline septum in lower nelius (1991); Medel and Vervoort (1995); Medel third of hydrothecal cavity well developed; median and López-González (1996); Ansín Agís et al. nematothecae 2/3 adnate, free end short almost reach- (2001). ing the hydrothecal rim; end of nematothecae usually curved outwards and reaching almost at level of Aglaophenia picardi Svoboda, 1979 hydrothecal rim. Lateral nematothecae small, apical (Figs. 64E-H) part swollen, reaching hydrothecal rim. Male corbula white, without free costa and usually partly open; Hydrocauli monosiphonic and unbranched, up to female corbula yellow, usually closed, with one well 80 mm, axis brown, without any basal prosegment, developed free costa. but several transverse nodes may occurs. Remainder Records from Mediterranean: eastern and west- parts composed of thecate internodes bearing hydro- ern Mediterranean, Adriatic. cladia, each with three nematothecae and a Known seasonality and reproduction: throughout pseudonematothecae; nodes oblique. Hydrocladia the year. alternate, widely spaced, perisarc transparent, divid- Distribution: northeastern Atlantic and Mediter- ed into cormidia by transverse nodes. Hydrothecae ranean. deep (length/breadth at rim: 1.5), rim with nine uni- References: Rossi (1961); Svoboda (1979); Gili form cusps, adcauline septum in lower third of (1986); Roca (1986); Svoboda and Cornelius hydrotheca inconspicuous or absent; median nema- (1991); Ramil and Vervoort (1992a); Boero and tothecae gutter shaped, almost complete adnate to the Bouillon (1993); Avian et al. (1995); Medel and hydrothecae, this with almost a half of its length free. Vervoort (1995); Medel and López-González Lateral nematothecae reaching hydrothecal rim. Cor- (1996); Ansín Agís et al. (2001); Peña Cantero and bulae transparent to white, male with large openings García Carrascosa (2002). between the pairs of opposite costae; female closed, with the proximal pairs of ribs almost free. Aglaophenia parvula Bale, 1882 Records from Mediterranean: eastern and west- (Figs. 64A-D) ern Mediterranean, Adriatic. Known seasonality: 1-12. Hydrocauli monosiphonic, up to 70 mm, yellow- Reproduction: 1-12 ish to brown, unbranched or dichotomously Distribution: northeastern Atlantic (N Spain, branched. Axis basally provided or not with several Cape Verde Is.), Black Sea; Mediterranean. transverse nodes and 1-3 prosegments separated by References: Svoboda (1979); Isasi (1985); Svo- oblique nodes; remainder internodes each with three boda and Cornelius (1991); Ramil and Vervoort nematothecae and a pseudonematothecae. Hydrocla- (1992a); Avian et al. (1995); Medel and Vervoort dia alternate, closely set, divided into cormidia sep- (1995); Medel and López-González (1996); Ansín arated by transverse nodes. Hydrotheca fairly deep, Agís et al. (2001); Peña Cantero and García Carras- narrowing basally, with a triangular aspect; rim with cosa (2002). nine unequal marginal cusps, outermost cusp single, unpaired, flexed interiorly; third pair bifid apex in Aglaophenia pluma (Linnaeus, 1758) varied degree; intrathecal septum well developed, (Figs. 64I-L) almost reaching opposite hydrothecal wall; mesial nematothecae almost reaching hydrothecal rim; lat- Hydrocauli monosiphonic up to 150 mm, brown, eral nematohtecae short, not reaching hydrothecal unbranched or dichotomously branched; basal part of rim. Colonies dioecious, male corbula with small the axis athecate, followed by one or two proseg- slits between nematophores of ribs; female corbula ments; remainder internodes, each with three nema- ribs fused with exception of rachial basis. tothecae and a pseudonematotheca; nodes oblique. Records from Mediterranean: found in the near- Hydrocladia alternate, with whitish cormidia separat- by areas of the Strait of Gibraltar. ed by transverse nodes. Hydrotheca deep Seasonality: ? (length/breadth at rim: 1.3-1.5), rim with nine cusps

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of varied length; intrathecal adcauline septum usually Reproduction: 2-10. well developed, median nematothecae 2/3 adnate, not Distribution: northeastern Atlantic, Mediterraean. reaching the margin of the hydrothecae; lateral nema- References: Svoboda (1979); Ramil (1988); Svo- tothecae reaching the rim of the hydrothecae; aperture boda and Cornelius (1991); Ramil and Vervoort of nematothecae gutter-shaped. Colonies dioecious, (1992a); Boero and Bouillon (1993); Alvarez male and female corbulae white, with free costa; male (1993); Avian et al. (1995); Medel and Vervoort close, with slit like openings between the costae, (1995); Medel and López-González (1996); Peña female with fused costae and smaller slits. Hydranth Cantero and García Carrascosa (2002). small, transparent, cylindrical, hypostome held at level of hydrothecal rim, rounded and low; ten tenta- Aglaophenia tubulifera (Hincks, 1861) cles emerging of hydrothecal rim. (Figs. 65F-I) Records from Mediterranean: western Mediter- ranean. Colonies pinnate up to 60 mm, composed of Known seasonality and reproduction: almost all monosiphonic and unbranched hydrocauli with the year. alternate hydrocladia. Axis basally with a proseg- Distribution: cited as cosmopolitan species, but ment separated by oblique nodes; occasionally also this need of evaluation due to identification prob- with several transverse nodes; remainder parts com- lems. Reliably reported from Shetlands, British posed of bearing-hydrocladia internodes, each with Islands, France, Belgium, Spain and Portugal, in the one pseudonematothecae and three nematothecae; north eastern Atlantic. nodes transverse. Hydrocladia alternate, closely References: Vervoort (1946); Patriti (1970); Svo- packed, each composed of a large number of boda (1979); Svoboda and Cornelius (1991); Boero cormidia; nodes transverse. Hydrotheca not deep; and Bouillon (1993); Medel and Vervoort (1995); adcauline septum weakly developed, rim with 9 Medel and López-González (1996); Ansín Agís et al. marginal cusp, the median one longest. Nematothe- (2001); Peña Cantero and García Carrascosa (2002). cae around hydrotheca without embayment; mesial nematothecae long, free part directed away from Aglaophenia tubiformis hydrotheca. Coenosarc with zooxantellae. Colonies Marktanner-Turneretscher, 1890 (Figs. 65A-E) dioecious; male corbula with slits between ribs, female with almost completely fused ribs and a Hydrocauli monosiphonic up to 150 mm, yel- basal free costa. Hydranth short, cylindrical, when lowish to brown, unbranched or dichotomously extending not projecting beyond hydrothecal rim; branched. Axis basally athecate, with several trans- hypostome hemispherical, ten short tentacles. verse nodes, followed by one (rarely two) proseg- Records from Mediterranean: western Mediter- ment separated by oblique nodes. Remainder intern- ranean (Spain, Morocco). odes each with three nematothecae and a pseudone- Known seasonality: 5, 6, 7, 9. matothecae. Hydrocladia alternate, yellowish to Reproduction: 5, 6, 7. brown, divided into cormidia by transverse nodes; Distribution: northeastern Atlantic, Mediterranean. cormidia composed of one hydrothecae and three References: Patriti (1970); Svoboda (1979); Gili nematothecae. Hydrotheca deep (length/breadth at et al. (1989); Svoboda and Cornelius (1991); Boero rim: 1.5-2), rim with 9 more or less equal cusps, and Bouillon (1993); Medel and Vervoort (1995); intrathecal adcauline septum moderately developed; Medel and López-González (1996); Ansín Agís et mesial nematotheca arising between the middle and al. (2001). upper third of hydrotheca, free portion of variable length; lateral nematothecae reaching or overtop- Genus Cladocarpus Allman, 1874 ping the hydrothecal rim; nematothecae with a gut- = Aglaophenopsis Fewkes, 1881 ter shaped aperture. Coenosarc filled with zooxan- = Nematocarpus Broch, 1918 thellae. Colonies dioecious; corbulae brown, with = Wanglaophenia Vervoot and Watson, 2003 the first pair of ribs free; male with slits between ribs; female with almost completely fused ribs. Hydroid: colony erect, monosphonic or polysi- Records from Mediterranean: eastern and west- phonic, hydrocaulus branched or unbranched, bearing ern Mediterranean, Adriatic (but not Black Sea). alternate usually unbranched hydrocladia; hydrocladia Known seasonality: 1-12. internodes with numerous septa; hydrotheca deep,

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often S-shaped, with or without intrathecal septa, usu- “main” frontal axis bearing nematothecae. Hydro- ally with a median abcauline tooth, with or without cladia borne on apophyses, alternate; internodes lateral teeth; nemathotheca usually with more than one with one hydrotheca and three nematothecae, one aperture, median inferior nematotheca short, usually median inferior and two lateral; nodes slightly below hydrotheca, never reaching thecal margin, oblique; each internode with 9-13 transverse peris- sometimes a superior nematotheca; gonothecae not arcal septa behind hydrothecae, 2-4 below and 1-2 contiguous, usually protected by loose phylactocarps above. Hydrotheca tubular, deep, tapered basally, with either unbranched or dichotomously branched widing distally; adcauline wall entire adnate; axis made of a regular succession of segments each abcauline wall slightly curved outwards at distal with 2-3 nematothecae and bearing an alternate third; margin sinuous, with a prominent median apophysis supporting a nematophorous branch, usual- abcauline cusp. Nematothecae tubular, gradually ly without hydrothecae, phylactocarp structures narrowing towards distal end; median inferior not resembling stag antlers. reaching hydrothecal base, with two apertures, one Remarks: Ramil and Vervoort (1992 b) pointed distally, slit-shaped, the other one, circular, at the out that the genus Cladocarpus contains two groups end of a short tube basally on the nematotheca, and of species with a different morphology of phylacto- directed towards hydrocladial wall; lateral nema- carps. In the first one, the phylactocarp is homolo- tothecae reaching beyond hydrothecal rim, also with gous with the hydrocaulus of Aglaopheniidae, two apertures, one apical, with a sinuous rim, and unbranched or branched and with segments bearing another one basal, on adcauline side, at end of short nematophorous branches; in the second one, being tube with a incomplete internal septum at its base; similar to the structure of hydrocladia, with segment cauline nematothecae with unique apical aperture. bearing each pairs (or a pair) of nematothecae in Gonothecae protected by unbranched phylactocarps opposite pairs. The first group of species, in their with nematothecae. opinion, should remain in Cladocarpus Allman, Records from Mediterranean: only Alboràn Sea. 1874 and the second group should be placed in Known seasonality: 6. Streptocaulus Allman, 1883. But as remarked by Distribution: N Spain, Australia and Mediter- Schuchert (2001 a) some species of Cladocarpus ranean (Alboràn Sea). have the proximal part of the phylactocaps of one References: Ramil and Vervoort (1992a); type and the distal one of the other (Cladocarpus Alvarez (1993); Medel and López-González (1996). bonneviae) and in some species of Cladocarpus the phylactocarps are not referable to one of the Cladocarpus pectiniferus Allman, 1883 described types (C. integer). Schuchert (2001a) con- (Figs. 65L-N, 66A-C) sider therefore that the genus needs comprehensive phylogenetical analyses to recognize monophyletic Hydrocauli polysiphonic basally, up to 100 mm taxa with sufficient reliability and that the types of high, growing from matting of perisarcal tubules. phylactocarps have to been defined more precisely. Frontal tube of the axis with a row of frontal nema- tothecae and apophyses bearing hydrocladia; usual- 1. Abcauline hydrothecal wall curvate...... 2 ly 2-5 nematothecae between two apophyses but – Abcauline hydrothecal wall straight ...... 3 very variable, one nematothecae borne in the axil of 2. Abcauline hydrothecal wall with double each apophysis. Nematothecae tubular, with a single curvature; with intrathecal septum .. C. sinuosus apical aperture. Hydrocladia alternate, composed of – Abcauline wall strongly concave; without internodes separated by slightly oblique nodes; each intrathecal septum ...... C. tenuis internode with one hydrotheca and three nematothe- 3. Aperture of hydrotheca even ...... C. pectiniferus cae, one median inferior and two laterals; internodes – Aperture of hydrotheca with a prominent with 17-27 septa. Hydrothecae tubular, elongated; abcauline cusp ...... C. multiseptatus walls almost straight; adcauline wall entire adnate, abcauline wall slightly curved outwards distally; rim Cladocarpus multiseptatus (Bale, 1915) smooth, somewhat convex frontally. Nematothecae (Fig. 65K) tubular, with two openings, one terminal with slight- ly serrated border, and one basal adcauline; lateral Colonies pinnate up to ca 15 mm; hydrocauli nematothecae with the two apertures connected, polysiphonic composed of several tubes of which, a may occurs also; median inferior nematothecae

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reaching or not hydrothecal base; lateral nematothe- Records from Mediterranean: only Alboràn Sea. cae overtopping hydrothecal rim. Phylactocarps in Known seasonality: 6. pairs at first hydrocladial internode, composed of Distribution: eastern Atlantic (coasts of Africa) rachis bearing gonothecae and paired nematothecae; and Alboràn Sea. rachis with four internodes, each with basal and dis- References: Vervoort (1966); Millard (1975); tal septum; first two segments with two pairs of Gili et al. (1989); Ramil and Vervoort (1992a); nematothecae, the rest with only one pair; nema- Medel and López-González (1996). tothecae tubular, elongated, with two apertures, one distally, finely serrated, and one basal, large and Cladocarpus tenuis Clarke 1879 oval; one or two additional, smaller may occurs in (Figs. 66J-K) between. Records from Mediterranean: only Alboràn Sea. Hydrocaulus unfascicled attaining a height of Known seasonality: 5, 6 about 40 mm, very delicate, bearing alternate hydro- Distribution: northeastern Atlantic, from Iceland cladia, containing some oblique nodes in basal to Morocco, and Alboràn Sea. region only, bearing a row of nematothecae on ante- References: Vervoort (1966); Ramil and Vervoort rior surface, of which one is seated in the axil of (1992 a and b); Medel and López-González (1996); each apophysis; hydrocladium consisting of weakly Schuchert (2001a). sigmoid thecate internodes separated by slightly oblique nodes; internodes containing numerous Cladocarpus sinuosus Vervoort, 1966 septa and bearing three nematothecae, one median (Figs. 66D-I) inferior and two laterals; hydrotheca very deep and slender, not sigmoidally curved, narrowest in the Colonies pinnate with monosiphonic or polysi- center then widening to margin, abcauline wall con- phonic and unbranched hydrocauli up to 53 mm; cave in the centre; adcauline wall straight; without main frontal axis bearing a row of nematothecae and intrathecal septum; margin with one mediane alternate hydrocladial apophyses; one nematothecae abcauline tooth and crenulated lateral edges; median is borne in the axil of each apophysis; hydrocladium inferior nematotheca free from hydrotheca, short not composed of hydrothecate internodes separated by reaching thecal base; with large fan-shaped terminal oblique septa; internodes sinuous, with one aperture, lateral nematotheca tubular, overtopping hydrothecae and three nematothecae, one median thecal margin, with terminal aperture; cauline nema- inferior and two laterals overtopping hydrothecal tothecae similar to median inferior; phylactocarp rim. each internode internally with 8-12 thick septa: borne on first internode of hydrocladium, 3 basal, 6-8 behind hydrothecae and one apical; unbranched, segmented, with two long nematothe- hydrotheca deep, with transverse adcauline septum cae on each internode, nematotheca with three aper- recurved at the tip at lower third; adcauline wall tures, one terminal and two laterals; gonothecae entire adnate, concave above insertion of septum; unknown. abcauline wall with double curvature, strongly con- Records from Mediterranean: western Mediter- vex in basal half, and strongly concave at about dis- ranean. tal third; rim even, with a unique median abcauline Seasonality: ? cusp. Median inferior nematotheca almost reaching Distribution: Gulf of Mexico; West Indies; hydrothecal base, with two apertures, one distal and Mediterranean. one basal towards hydrothecal wall; lateral nema- References: Nutting (1900); Vervoort (1966); tothecae tubular, with two apertures, one terminal Millard (1975); Marinopoulos (1981). and one mesial, with intrathecal septum; cauline nematothecae also with two apertures, one terminal Genus Gymnangium Hincks, 1874 and one basal, towards axial wall; phylactocarp = Haliaria Stechow, 1921 borne on first internode of hydrocladium, curved = Halicetta Stechow, 1921 and unbranched, with short internodes with two very long, curved nematothecae with up to four apertures, Hydroid: colony erect, often stout, monosiphonic one terminal and the rest along the upper surface; or polysiphonic, arising from a creeping hydrorhiza or gonothecae below first pair of nematothecae, ovoid from anchoring filaments; hydrocladia unbranched, with truncated distal end. alternate or opposite, giving off from opposite sides of

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hydrocaulus; hydrothecae only on hydrocladia, typi- Hydroid: colony erect, branched or unbranched, cally more or less cone-shaped, intrathecal septum bearing alternate unbranched pinnate hydrocladia; present or absent, margin with or without cusps; each hydrotheca sac-shaped to deep, usually with hydrotheca with a pair of lateral nemathotecae and a intrathecal septum; generally with teeth or lobed single adnate median inferior nematotheca, conspicu- margin; mesial outer tooth of hydrothecal rim usual- ously longer than hydrotheca (2-3 times), and having ly prominent; median inferior nematotheca fairly more than one opening; gonotheca solitary, usually short, not reaching hydrothecal margin, sometimes a borne on hydrocladia, not protected by phylactocarps superior dissymmetrical nematotheca (i.e. L. pera- or corbulae; fixed sporosacs, one species with swim- mata); corbulae formed by modified hydrocladia ming gonophores (G. ferlusi). bearing secondary unfused ribs bearing a row of References: Cornelius (1995); Calder (1997); approximately 12 nemathothecae, some, in at least Schuchert (2003). one sex, bearing one hydrotheca; fixed sporosacs. References: Calder (1997); Schuchert (2001a, Gymnangium montagui (Billard, 1912) 2003). (Figs. 66L-O) 1. Hydrothecate internodes with 2-3 poorly Colonies erect and monosiphonic up to 120 mm, developed internal septa ...... L. distans with a yellowish to brown hydrocauli and a thick – Hydrothecate internodes with 6-13 well hydrorhiza. Axis segmented into short internodes; developed internal septa ...... L. myriophyllum nodes slightly oblique; each internode with two later- al apophyses bearing hydrocladia, alternate, one basal Lytocarpia distans (Allman, 1877) and the another one distal; two cups-shaped nema- (Figs. 67A-B) tothecae are located basally to each apophysis, an upper and a lower. Hydrocladia alternate, closely set, Hydrocauli polysiphonic up to 200 mm high, internodes short, nodes almost transverse; each intern- growing on a hydrorhiza composed of numerous ode with one hydrotheca and three nematothecae; tubes. Frontal tube of the axis with a longitudinal hydrotheca cup-shaped, 2/3 of adcauline wall adnate, row of nematothecae and lateral hydrocladial a distinct, slightly curved abcauline internal septum at apophyses, 2-5 nematothecae between two apophy- half length of abcauline wall, dividing it into two con- ses. Hydrocladia alternate, in the same plane, with vex portions; hydrothecal aperture inclined down- internodes separated by transverse nodes, each with ward, rim sinuous, occasionally with indication of lat- one hydrotheca and three nematothecae, one median eral cusp on each side; lateral nematothecae also cup- inferior and two laterals; internal septa poorly devel- shaped, median nematotheca much elongated, curved, oped, two under the median nematothecae and one surpassing hydrothecal border considerably, free part behind hydrotheca at same level as intrathecal sep- at least half length of adnate part or more, opening gut- tum. Hydrothecae elongated, narrowed basally; ter-shaped, along whole free length; gonothecae in adcauline wall completely adnate, intrathecal sep- two rows on frontal aspect of colony, each attached to tum poorly developed; rim with shallow cusps, but a hydrocladial apophysis, colour white, conical, trun- prominent one frontally. Median inferior nematothe- cate distally and there with concavity. ca short, reaching the hydrothecal base; lateral Records from Mediterranean: Atlantic species nematothecae small, rim at same level of hydrothe- found in Algeciras Bay (Strait of Gibraltar). cal rim; all nematothecae with a gutter-shaped aper- Known seasonality: 5, 7, 12. ture. Corbulae with 10-14 costae, each with one Reproduction: 5. basal hydrotheca, 2-3 abcauline nematothecae and Records outside the Mediterranean: eastern 6-10 adcauline ones. Atlantic. Records from Mediterranean: western Mediter- References: Millard (1975); Cornelius (1995); ranean. Medel and Vervoort (1995); Medel and López- Known seasonality: 8. Corbulae: 8. González (1996). Distribution: northeastern Atlantic and Pacific; Mediterranean. Genus Lytocarpia Kirchenpauer, 1872 References: Bedot (1921); Vervoort (1972); Gili = Acanthocladium Allman, 1883 (1986); Ramil and Vervoort (1992a); Boero and = Thecocarpus Nutting, 1900 Bouillon (1993); Medel and López-González (1996).

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Remark: species very similar to L. Myriophyllum creeping hydrorhiza or anchoring filaments; hydro- but clearly differs in the shape of hydrothecae, the cladia unbranched, pinnately arranged, arising alter- median inferior nematothecae, the adcauline wall nately from apophyses on axial tube of hydrocaulus and in the development and number of internodal and branches; hydrothecae only on hydrocladia, septa (see Ramil and Vervoort, 1992a). more or less cone to sac-shaped; hydrothecal margin dentate; abcauline or adcauline intrathecal septum Lytocarpia myriophyllum (Linnaeus, 1758) present; cauline internodes with triangular (Figs. 66P-U) nemathotheca; each hydrotheca with a pair of later- al nemathotecae and a single partly adnate median Hydrorhiza composed of numerous fibers living inferior nematotheca; gonophores usually fixed the hydrocaulus over different levels. Stem polysi- sporosacs, exceptionally one species with swim- phonic, up to about 350 mm, yellowish to brown, ming sporosacs (Macrorhynchia philippina pinnate and unbranched; up to four well marked Kirchenpauer, 1872), gonothecae on unbranched oblique nodes arranged basally; axis with a “main” phylactocarps formed by modified hydrocladia, frontal tube and many parallel secondary ones, all occurring single or aggregated in pseudocorbula. with a longitudinal row of small cup-shaped nema- References: Calder (1997); Schuchert (2003). tothecae. Hydrocladia borne on main tube; alternate, in the same plane. Hydrocladial internodes each Macrorhynchia philippina (Kirchenpauer, 1872) with one hydrothecae and three nematothecae, one (Figs. 67C-H) median inferior and two laterals; a varied number (6-13) of perisarcal septa developed transversally in Colonies about 15-20 cm high; hydrocauli poly- the internodes; nodes transverse. Hydrotheca more siphonic, strongly and irregularly branched. Branch- or less cylindrical, rounded and with transverse es arising from peripheral tubes of stem, monosi- adcauline septum basally; rim with shallow cusps, phonic or slightly polysiphonic, with a basal part but frontal one on abcauline wall very prominent. bearing median nematothecae and a distal part bear- Mesial nematothecae reaching the lower forth of ing alternate hydrocladia. Axial tube of stem and hydrothecae, free part short, aperture with a deep distal part of branches with internodes each with one adcauline embayment; lateral nematothecae slightly hydrocladial apophysis and two nematothecae; overtopping hydrothecal rim, aperture with a deep mamelon present on anterior surface of apophysis. adcauline embayment. Corbulae large, open, 5-20 Hydrocladia not very long, with 10-15 internodes costae, each with usually one, but up to three basal each with one hydrotheca, two lateral nematothecae hydrothecae and several nematothecae, usually 2 and one median hydrotheca; nodes straight or slight- abcauline and 5-9 adcauline; gonothecae ovoid, ly oblique. Hydrotheca with a thick abcauline alternate, up to 24 in a same corbula. intrathecal septum and an adcauline intrathecal one Records from Mediterranean: western Mediter- at lower level; margin with two pairs of low, round- ranean, Adriatic. ed cusps and a thickened abcauline median cusp Known seasonality: 6-8. Corbulae: 8. continuous basally with the abcauline intrathecal Distribution: Arctic, eastern Atlantic (till Guinea septum and projecting distally as a short spine. Lat- Bissau); Mediterranean; Indo-Pacific records need eral nematothecae tubular, projecting above to be evaluated. hydrothecal margin, with two openings, one distal References: Gili, Vervoort and Pagès (1989); and one mesial; free part of the median nematotheca Ramil and Vervoort (1992a); Boero and Bouillon long, overtopping hydrothecal margin, with three (1993); Cornelius (1995); Avian et al. (1995); openings, one rounded distal, one on upper surface Medel and Vervoort (1995); Medel and López- at base of free part, and one into the hydrohteca; 0- González (1996). 2 internodal septa. Phylactocarp borne on apophy- ses, with a hydrothecate internode basally, this fol- Genus Macrorhynchia Kirchenpauer, 1872 lowed by several gonothecae-bearing internodes, on = Lytocarpus Allman, 1883 which the hydrotheca has been replaced by and = Nematophorus Clarke, 1879 apophysis bearing a gonothecae; gonothecae large, disc-shaped, dioecious, giving free medusoids, these Hydroid: colony erect, hydrocauli branched or without radial canals, circular canal, tentacles and unbranched, polysiphonic, often stout, arising from tentacular bulbs.

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Records from Mediterranean: eastern Mediter- rounded and weakly developed cusps on each side or ranean. only sinuous side, and with a distinct abcauline, Seasonality: ? frontal cusp. Mesial nematothecae not reaching the Records outside the Mediterranean: tropical waters hydrotheca base, tubular, rim circular, deep adcauline of the Atlantic, Pacific and Indian Oceans. embayment; lateral nematothecae overpassing References: Vervoort (1968); Gravier (1970); hydrothecae, with two apertures, one apical and anoth- Millard (1975); Boero et al. (1997), Watson (2000). er one adcaulinar, opening into hydrothecal cavity. Phylactocarp composed of eight segments, each with Genus Streptocaulus Allman, 1883 a pair of opposite nematothecae, these with wide aper- = Aglaophenopsis Fewkes, 1881 tures; gonothecae on the basal segment; female cylin- =Nematocarpus Broch, 1918 drical, ends rounded, aperture sub-distal and oval, male shorter, ovoid, with a terminal aperture. Hydroid: colony erect; hydrocauli branched or Records from Mediterranean: western Mediter- unbranched; hydrocladia pinnate in young colonies, ranean (S. Spain). gradually becoming spirally arranged by axis tor- Known seasonality: 7. sion with age; hydrothecae adnate, hydrothecal rim Distribution: eastern Atlantic (from Morocco to with weakly developed cusps; three hydrothecal Senegal), Mediterranean?. nematothecae present; fixed sporosacs protected by References: Billard (1924, 1934); Vervoort phylactocarps with axis homologous to a hydrocla- (1959); Patriti (1970); Boero and Bouillon (1993); dium; rachis axis unbranched or irregularly Medel and Vervoort (1995); Medel and López- branched, divided in segments, each bearing one or González (1996). several pairs of more or less opposite lateral nema- tothecae; rachis axis bearing one or more gonothe- Family BARCINIDAE cae; when axis and phylactocarps are long, the struc- Gili, Bouillon, Pagès, Palanques and Puig, 1999 ture appears centipede-like. Remark: The genus Streptocaulus seems polyphylet- Hydroid: unknown. ic based on phylactocarp morphology (Calder, 1997). Medusa: marginal vesicles closed; ocelli adaxial; References: Ramil and Vervoort (1992a); Medel and manubrium narrow, no peduncle; 4 simple radial Vervoort (1995); Calder (1997); Ramil et al. (1998). canals; 4 marginal tentacles; tentacular bulbs large, globular; “gonads” linear, ribbon-like, surrounding Streptocaulus dollfusi (Billard, 1924) radial canals. (Figs. 67I-K) Genus Barcino Hydrocauli long (up to about 400 mm), polysi- Gili, Bouillon, Pagès, Palanques and Puig, 1999 phonic, yellowish, occasionally irregularly branched. Only a frontal tube of the stem thecate and bearing With the characters of the family. hydrocladia, divided into internodes by means of transverse nodes; segments with a distal bearing Barcino foixensis hydrocladia apophysis, and a row of frontal nema- Gili, Bouillon, Pagès, Palanques and Puig, 1999 tothecae (usually 3-5); one of them shorter, in the axil (Figs. 67L-M) of the apophysis, occasionally also another one besides of the apophysis; all nematothecae with two With the characters of the family. apertures, one terminal and one basal at the adcauline Records from Mediterranean: western Mediter- wall. Hydrocladia alternate, more or less in the same ranean. plane; internodes with one hydrothecae and three Known seasonality: 5. nematothecae; nodes slightly oblique; six perisarcal Distribution: endemic of Mediterranean Sea ring at the base of median nematothecae (one, but References: Gili et al. (1999). occasionally doubled) and behind the hydrothecae (five). Hydrothecae long, fully adnate, abcauline wall Family BLACKFORDIIDAE Bouillon, 1984 convex in lower half, straight and inclined in upper half; a transverse adcauline septum in lower third, this Hydroid: colonies reptant, rarely slightly ramified, typically recurved upwards. Hydrothecal rim with bearing 2-3 hydrothecae on each stem; hydrothecae,

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tubular exhibiting longitudinal striations, its lower part panulate or cylindrical, with or without pedicel, sharply broadened directly above hydrocaulus and always covered by operculum of several triangular separated from it by a diaphragm; operculum consist- flaps, sharply demarcated from hydrotheca or not; ing of numerous triangular flaps meeting centrally and with or without diaphragm; with or without showing no clear demarcation from the hydrothecal nematophore; gonophores as fixed sporosacs or as margin; hydranth with conical hypostome and a whorl free medusae. of 12-16 filiform tentacles, an intertentacular membra- Medusa: see remarks below. nous web present; gonothecae developing on stem or Remarks: The Campanulinidae represent a poly- on stalk of the hydranths, sacciform, one medusa at a phyletic taxon, traditionally comprising species hav- time in each gonophore ing hydroids of a generalised “campanulinid type». Medusa: manubrium narrow, short; mouth with 4 The distinction between two types of operculum long, fluted lips; numerous hollow tentacles; tenta- (pleated or segmented, formed by numerous flaps cle endodermal core extending inwards from bell which may or not be delimited by a prominent margin into bell mesoglea; 4 radial canals; “gonads” crease-line at the base of the cusps) has not the tax- completely surrounding radial canals; marginal ten- onomic value that it was formerly given (see tacles numerous 80- 250, no permanent rudimentary Lovenellidae). tentacles; numerous closed statocysts. Many “campanulinid” hydroids release References: Valkanov (1935); Logvinenko (1959); medusae that are referable to unrelated medusa- Naumov (1960, 1969); Denayer (1973); Zhang Jin- based families This is not the only case of incon- biao (1977, 1979); Moore (1987); Bouillon et al. sistency between hydroid and medusan morpholo- (1988b); Mills and Somner (1995); Bouillon (1999); gy: Rees (1956), for instance, already showed that Bouillon and Boero (2000); Mills and Rees (2000). the hydroids (nearly 40 species) referred to the hydroid-based genus Perigonimus M. Sars 1846, Genus Blackfordia Mayer, 1910 which are as similar morphologically to each other as are the “Campanulinid” hydroids, are referable See family characters. to five medusa-based families: four of Anthome- dusae and even one of Leptomedusae. Most of the Blackfordia virginica Mayer, 1910 described “Campanulinid” hydroids, unfortunate- (Figs. 67N; 68A-B) ly, have unknown or poorly known life cycles and, as a consequence, cannot be confidently identified Hydroid: with the characters of the family. at a generic or family level. Due to the difficulty Medusa: umbrella 14 mm wide, higher than a of assigning such operculate hydroids to family- hemisphere, with rounded apex; manubrium narrow, group taxa, taxonomists have usually lumped half as long as subumbrellar cavity, four long fluted them, for convenience, in the family Campanulin- lips; gonads linear, from corner of manubrium idae. Only the knowledge of the complete life extending along somewhat more than half the length cycles of those species will contribute to resolve of radial canals; about 80 long marginal tentacles with this situation. Calder (1991), to avoid the practice finger-shaped or broadly oval diverticula into bell of employing the Campanulinidae as a catch-all margin; one (rarely 2) statocysts between successive family, provisionally included the genera Opercu- tentacles, each with 2-3 concretions; often with black larella and Plicatotheca (see remarks under Oper- pigment granules at base of the statocysts. cularella) in the Phialellidae and included into Records from Mediterranean: eastern Mediter- “Family incertae sedis” those genera which cannot ranean. be assigned with any degree of certainty to a fam- Known seasonality: 7. ily (for instance Lafoeina and Egmundella). Distribution: Antlantic; Indo-Pacific; Mediter- Calder (1991) proposed also a new definition of ranean; Caspian Sea. the family Campanulinidae covering more or less References: see above family. the Eirenidae Haeckel, 1879. He also argued that Campanulina tenuis Van Beneden, 1847, the Family CAMPANILINIDAE Hincks, 1868 auct. misidentified type genus of Hincks Campanulin- idae family (see Campanulina), could correspond Hydroid: colony stolonal or erect; hydrocaulus to a hydroid with regressed hydrotheca, similar branched or unbranched; hydrotheca usually cam- those found in some aged eirenid hydroids and

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that, due to this similarity, the two families should – Operculum of numerous segments, opercular be considered identical, with the name Campan- valves not sharply demarcated ...... 2 ulinidae having priority. We do not follow this 2. Nematophores present ...... 3 proposal: Campanulina tenuis is a poorly – Nematophores absent ...... 4 described, non-operculate, species considered here 3. Hydrotheca sessile and tubular; nematothecae as an incertae sedis (see Campanulina). This oval to tubular; gonophores producing fixed species can in any case be attributed to an existing sporosacs or medusa buds...... Lafoeina genus of Eirenidae, a medusa-based family with a – Hydrotheca pedicellate widest at distal end, vast array of hydroid types. Finally, campanulinid tubular to top-shaped; nematotheca not tubular; regressed hydroids similar to those described for gonophores where known with medusa buds ..... some Eirenidae exist in many other Leptomedusae ...... Egmundella families. It appear thus that, at present, it is not 4. Hydrotheca pedicellate...... 5 possible to obtain a complete and satisfactory clas- – Hydrotheca sessile, rising directly from stolon, sification of campanulinid hydroids and that, as long and tubular, gonophores unknown or con stated by Cornelius (1995), the Campanulinidae taining unidentifiable medusa buds (when free paradox has still to be resolved, and little is to be adult medusae known, see medusae genera)...... gained from attempting a new family diagnosis or ...... Cuspidellla from retaining the old one. 5. Gonophores unknown or containing unidentifi- In the diagnosis given above we keep in the able medusa buds (when free adult medusae Campanulinidae only the genera from which the known, see medusae genera)...... Campanulina gonosome is known as fixed sporosacs, the – Gonophores as fixed sporosacs.... Opercularella species with identifiable medusae being trans- ferred to their medusae families in agreement Genus Calycella Allman 1864 with the law of priority. The campanulinid hydroids with fixed sporosacs can represent the Hydroid: colony stolonal; pedicel usually sharply results of multiple and independent medusa twisted and short; hydrotheca tubular, deep, margin reduction within different Leptomedusae family crenulated; operculum with a scalloped crease-line groups and it is presently impossible to refer them at base of opercular segments not quite meeting in safely to any family with free medusae and to the centre; hydranth without intertentacular web; establish their real phylogenetic relationships It nematophores absent; gonophore borne on seems more reasonable to retain them under a hydrorhiza as fixed sporosacs, acrocyst with no common denomination until further research will medusa stage has been recorded. allow more natural groupings, than to include Remark: Calycella gracilis Hartlaub, 1897 has them, without phylogenetic support, in any unknown gonophores and is here considered as medusa-based family; molecular biology tech- incertae sedis, its diagnosis is not taken in consider- niques will surely help to resolve these ambigui- ation in the above keys. ties. The campanulinid genera with unknown References: Cornelius (1995); Hirohito (1995); gonosome will be provisionally included here in Blanco et al. (2000). the Campanulinidae incertae sedis. This appears more convenient than to put them in “Family Calycella syringa (Linnaeus, 1767) incertae sedis” as proposed by Calder (1991), (Figs. 68C-E) since our proposal at least gives an idea of the general morphology of the hydroid stage. Colonies composed of a tortuous stolon giving Reference: Schuchert (2001a).0 rise to numerous hydrothecae with spiral pedicels. Hydrotheca cylindrical, elongated, slightly narrower Key to campanuliniid hydroids with fixed basally; rim with low cusps and with low typically sporosacs, unidentifiable medusa buds or 8-10 flapped operculum; this often missing. unknown gonophores Hydrothecal pedicels annulated; gonophores as fixed sporosacs, gonothecae on short and ringed 1. Opercular valves seated in distinct embayments pedicels; ovoid, aperture in male broad, in female of thecal margin and sharply demarcated from it with a short introverted tube extending inside ...... Calycella gonothecae; embryos held in acrocyst.

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Records from Mediterranean: western Mediter- and López-González (1996); Medel (1996); Watson ranean, Adriatic. (2000); Schuchert (2001a). Seasonality: ? Distribution: nearly cosmopolitan in coastal Genus Opercularella Hincks, 1868 waters. References: Hamond (1957); Ramil (1988); Cor- Colonies stolonal or erect, sympodially nelius and Ryland (1990); Boero and Bouillon branched; hydrotheca pedicellate, cigar-shaped or (1993); Cornelius (1995); Medel and López- ovoid; opercular flaps gradually merging with walls González (1996); Schuchert (2001a). of the hydrothecae without distinct boundaries, opercular segment not quite meeting in the centre; Genus Lafoeina G.O. Sars, 1874 = Keratosum pedicel with 5 or more twist not well differentiate Hargitt, 1909 from hydrothecae; degenerate diaphragm present; hydranth intertentacular web where present not well Colonies stolonal, or irregularly branched, with developed. polysiphonic stem; hydrotheca cylindrical, pedicel Gonophores as fixed sporosacs, usually the absent, operculum composed of numerous triangular female usually with acrocyst within the planulae segments without basal crease-line; hydranth with- develop. Gonothecae on pedicel arising from main out intertentacular web; nematotheca tubular, with- stem or on hydrorhiza. out operculum, aperture minute and sub-distal on Remark: Rees (1939) revised the Campanulin- one side; gonotheca similar to hydrotheca, same size idae and proposed to put together for the sake of or larger; gonophores, when known, as fixed convenience into the genus Opercularella all cam- sporosacs or giving rise to medusae buds with four panuliniid species with fixed sporosacs or with tentacles and eight lateral cirri; adult medusa unknown gonophores. Calder (1991) provisionally unknown. included the genera Opercularella and Plicatotheca References: Calder (1991); Cornelius (1995); in the Phialellidae without any convincing taxonom- Hirohito (1995); Blanco et al. (2000). ical reason if not to remove those two genera from the dubious scope of the Campanulinidae. But doing Lafoeina tenuis G.O. Sars, 1874 so he transferred the problem from one family to (Figs. 69E-G) another, making confusion in the Phialellidae. Almost all specialists agree that medusa reduction is Colonies minute, stolonal; stolon branched, usu- not a reliable phylogenetic taxonomic character to ally anastomosed, giving rise to hydrothecae and separate two genera but, in a large taxon like the nematothecae. Hydrothecae tubular, narrower basal- Campanulinidae, it is impossible, at the state of our ly, lacking pedicels, operculum with about 10 trian- present knowledge, to attribute the species with gular segments. Nematothecae tubular, length vari- fixed sporosacs (for instance Opercularella) to the able, rounded distally, aperture lateral, subdistal; corresponding genera with free medusae. The genus gonophores as free medusa described only within Opercularella is accepted here in a more restricted gonothecae; gonothecae similar to the hydrothecae. sense than Rees (1939), including only the forms Records from Mediterranean: western Mediter- with fixed gonophores, the “Opercularella-like ranean, Adriatic Sea. hydroid” species with unknown gonophores or inde- Seasonality: ? terminable medusa buds being referred to the genus Distribution: north Atlantic (eastern and west- Campanulina incertae sedis, pending further infor- ern) and Indian Ocean, Mediterranean. mation about their cycles. References: Hadzi (1917, 1959); Bouillon (1971) Recent references: Calder (1991); Cornelius (1995); as Lafoeina vilaevelebitti; Millard and Bouillon Genzano (1995); Blanco et al. (2000); Schuchert (1973) as Egmundella amirantensis; Ramil (1988); (2001a). Ramil and Vervoort (1992a); Peña Cantero and Gar- cía Carrascosa (2002) as Egmundella amirantensis; Opercularella lacerata (Johnston, 1847) Cornelius (1995); Calder (1991) as Lafoeina ami- (Figs. 69H-K) rantensis; Boero and Bouillon (1993) as E. amiran- tensis and L. tenuis; Altuna (1994) as Lafoeina Colonies erect and branched, composed of deli- tenuis; Hirohito (1995) as L. vilaevelebitti; Medel cate stems annulated and spirally grooved through-

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out, giving rise hydrothecae pedicellate arranged unknown or incompletely known cycle awaiting the irregularly. Hydrothecae somewhat tubular, narrower discovery of their type of gonophoral contents or of basally and distally, operculum with 9-12 deep and the determinable medusae allowing their final attribu- pointed valves without basal crease-line; basal tion to a completely diagnosed genus. diaphragm present; gonophores as fixed sporosacs; gonothecae usually pedicellate borne on stem or on Campanulina panicula G.O. Sars, 1874 stolon; male sub-cylindrical, female larger, narrower (Figs. 68F-I) gradually towards basally, wider and truncate distally. Records from Mediterranean: western Mediter- Stem erect, straight, monosiphonic, typically ranean. smooth and unbranched. Hydrothecae borne on sin- Seasonality: ?. gle or on branched pedicels, alternate and laterally Distribution: north Atlantic Ocean. Indo-Pacific to the main axis. Pedicels annulated basally; records doubtful (Cornelius (1995)). hydrotheca conical, narrower basally, diaphragm References: García-Carrascosa (1981); Altuna distinct, operculum conical, with about 20 segments, (1994); Cornelius (1995); Medel and López- without demarcation line basally; gonotheca borne González (1996); Schuchert (2001a). on axis or on hydrothecal pedicels; shortly pedicel- lated, cylindrical, elongated, slightly asymmetric “Campanulinidae” incertae sedis with gonophores and truncate distally, gonothecal aperture broad; unknown or gonophores with indeterminable reproduction unknown perhaps a developing medusa buds: medusa (Rees and Rowe, 1969). Records from Mediterranean: western Mediter- Genus Campanulina auct. ranean. Seasonality: ? Hydroid: colony stolonal or erect; hydrotheca Distribution: Moderately deep to deep waters of tubular, with a pointed pleated or segmented oper- the Atlantic, Pacific and Indian Oceans (Ramil and culum which may or not be delimited basally by a Vervoort, 1992a), Mediterranean. crease line; no nematophores; usually with References: Ramil and Iglesias (1988b); Ramil diaphragm; gonophores unknown or arising as inde- and Vervoort (1992a); Cornelius (1995); Medel and terminable medusa buds. López-González (1996); Schuchert (2001a). Remarks: the original diagnosis of Campanulina tenuis, type species of Campanulina, was a brief pre- Genus Cuspidella Hincks, 1866 liminary account made by Van Beneden in 1847 of a (Figs. 69A-B) non operculate, non fertile hydroid, not correspond- ing to the concept of an operculate Campanulinidae Colonies stolonal, with tubular and usually ses- as understood by all further authors, Van Beneden sile hydrothecae, lacking pedicel, in some species (1867) included (see Rees, 1939, Calder, 1991). Cam- separated from stolon by basal constriction; opercu- panulina tenuis has never been observed since its lum conical, several cups meeting centrally, with or diagnosis and should be considered as an indetermi- without basal crease-line; hydranth extensile, tenta- nate species. The Genus Campanulina has slowly cles amphicoronate, with or without basal web and been the dumping ground for species belonging to hypostome conical. Gonophores, where known, several other Campanulinidae genera; even at the pre- growing to free medusae; gonothecae, where pre- sent day the same hydroid species can be found sent, resembling hydrotheca but usually larger. described in literature under different genera names Remarks: What is named by Cornelius (1995) (Opercularella, Campanulina and Phialella) depend- “Cuspidella facies”, describes stolonal colonies with ing the authors, showing the great confusion existing tubular and usually sessile hydrothecae, lacking within the campanulinid hydroids and the definition pedicels, in some species separated from stolon by of their genera! Such confusion is partly linked to the basal constriction; operculum conical, several cups difficulty to distinguish morphologically from each meeting centrally, with or without basal crease-line; other the different hydroid species but, above all, to hydranth extensile, tentacles amphicoronate, with or the absence of knowledge about their life cycle. The without basal web and hypostome conical. Gonothe- Genus Campanulina is here conserved as collective cae, when are present, resembling hydrotheca but group for the “Campanulinid type” species with usually larger. This polypoid stage is found in sever-

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al hydroidomedusae families, and when described in hydrotheca pedicellate, deeply campanulate, ignorance of the corresponding medusa stage, they turbinate, widest at distal end, thin perisarcal shelf have been, for convenience, referred to the nominal present; operculum cone-shaped not distinctly genus Cuspidella. They must be considered as a demarcated from hydrotheca; diaphragm present or “collective group” awaiting further investigations. reduced; nematophores solitary or aggregated, bul- In this way, Mediterranean species referred to this bous through clavate or tubular, on hydrorhiza or on genus may be considered as doubtful species which both hydrorhiza and hydrocaulus; gonophores giv- need to be linked to their corresponding medusae. ing rise to medusa buds, gonotheca borne on hydrorhiza, non pedicellate or shortly pedicellate, Cuspidella costata Hincks, 1868 similar to hydrotheca. Remark: this genus is considered incertae sedis Records from Mediterranean: western Mediter- pending futher knowledge about the nature of the ranean adult medusae. Known seasonality: 7, 8. References: Calder (1991); Hirohito (1995). Distribution: see remark. References: Aguirrezabalaga et al. (1988); Egmundella grimaldii Leloup, 1940 Altuna and García-Carrascosa (1990); Medel and (Figs. 69C-D) López-González (1996). Remark: This species is in part, conspecific with Hydroid: hydrorhiza stolonal, polysiphonic; Lafoeina tenuis and with Laodicea undulata. hydrotheca elongated, diaphragm thin; pedicel short with one proximal spiral annulus; nematotheca Cuspidella humilis (Alder, 1862) fusiform, pedicellate; gonophore unknown. Records from Mediterranean: western Mediter- Hydroid: hydrothecae arising directly from a ranean. creeping hydrorhiza; without pedicel, but basal part Distribution:? of the hydrotheca distinctly constricted and some- References: Leloup (1940b); Alvarez (1993). times slightly undulated; hydrotheca more or less cylindrical, narrowed basally; operculum with sever- Egmundella valdiviae Stechow, 1923 al 12-16 triangular valves, with crease line in the diagnosis by Gili (1986), but not in Vervoort (1968). Hydroid: similar to E. grimaldii but with a longer Hydranth long, hypostome with 12 filiform tentacles. pedicel. Known seasonality: 7, 8. Reference: Marinopoulos (1981) Records from Mediterranean: western Mediter- ranean. Family CIRRHOLOVENIIDAE Bouillon, 1984 Distribution: ? References: García-Corrales, et al. (1979); Gili Hydroid: when known, colony stolonal of “Cus- (1986); Medel and López-González (1996). pidella” type; hydrotheca sessile, tubular, closed by Remarks: doubtful records and species. This a pyramidal operculum formed by numerous flaps species is considered partly as conspecific of meeting centrally and not clearly demarcated; no Lafoeina tenuis (see Cornelius (1995).For Naumov intertentacular web; gonotheca unknown. (1951, 1969) Cuspidella humilis should be the Medusa: manubrium small; 4 simple radial hydroid of Staurophora mertensii. canals; “gonads” on radial canals separated from The records of this species in the Mediterranean manubrium; marginal tentacles hollow; with mar- coasts by García-Corrales et al, (1979), are consid- ginal cirri; 4 or more closed statocysts. ered by Altuna (1994) as Calycella syringa (Lin- naeus, 1767). The Diagnosis of the species by Gili Genus Cirrholovenia Kramp, 1959b (1986) resembles to Lafoeina tenuis. Hydroid: only known in C. tetranema, see fami- Genus Egmundella Stechow, 1921b ly characters. Medusa: 4-40 marginal tentacles; 7-8 marginal Hydroid: colony usually stolonal, infrequently cirri between successive marginal tentacles. erect and branched; hydrocaulus polysiphionic;

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Cirrholovenia tetranema Kramp, 1959b References: Russell (1963c); Calder (1991), (Figs. 70A-C) Pagès et al. (1992); Bouillon (1999); Bouillon and Barnett (1999); Bouillon and Boero (2000); Kubota Hydroid: see family characters. (2000). Medusa: umbrella up to 1.5 mm wide and high, mesoglea thin; manubrium small, cruciform; mouth Key to hydroids with very short simple lips; «gonads» thick, cylin- drical along almost entire length of radial canals; 4 The hydroids of the Eirenidae are indistinguish- long perradial marginal tentacles, with broad bulbs; able from each other they can be of “campanulina”, no rudimentary bulbs; 7-8 marginal cirri in each “campanopsid” or “eugymnanthea” type. quadrant; 4 interradial or 8 adradial statocysts some- times up to nine. Key to medusae Records from Mediterranean: eastern and west- ern Mediterranean. 1. With more than 8, typically with indefinite Known seasonality: 2-11. number of statocysts...... 2 Distribution: Atlantic; Indo-Pacific; Mediterranean. – With usually 8 statocysts (rarely 12); without References: Kramp (1959b; 1961); Goy (1973b); excretory papillae ...... 3 Brinckmann (1965, 1987); Moreira (1975); Lakkis 2. Without cirri; with or without excretory papillae and Zeidane (1985); Goy et al. (1988, 1990, 1991); ...... Eirene Boero and Bouillon (1993); Kubota (1995). – With lateral cirri at base of some or all marginal tentacles; with excretory papillae.... Helgicirrha Family EIRENIDAE Haeckel, 1879 3. Degenerated medusae without marginal tentacles ...... Eugymnanthea Hydroid: colony of benthic species stolonal or – Normal medusae, with marginal tentacles ...... 4 erect ramified; bivalve-inhabiting species without 4. Without cirri ...... 5 perisarc, with pedal disc, usually solitary; planktonic – With lateral cirri on marginal warts and usually species (Eirene hexanemalis) solitary, polyp budding also on marginal tentacles; «gonads» on totally into a single medusa; hydrotheca cylindrical in subumbrella, or on gastric peduncle or on both.. young colonies of erect forms, with diaphragm and ...... Eutima folded pleated operculum formed by convergent flaps 5. Without cirri and marginal warts, «gonads» not demarcated from the hydrothecal rim (Campan- restricted to subumbrella ...... Eutonina ulina type); in older colonies of this type, operculum – Without cirri, with marginal warts, with generally lost and hydrotheca reduced to perisarcal «gonads» along entire length of radial canals..... collar, of haleciid type; hydrotheca usually reduced or ...... Neotima absent in stolonal colonies, hydranth naked, borne directly on hydrorhiza or on short pedicels (Cam- Genus Eirene Eschscholtz, 1829 panopsis type); hydranth of commensal species elon- gated, extensile, with filiform tentacles in a single Hydroid: Campanopsis or Campanulina type or amphicoronate whorl; intertentacular web present; approaching it, see family characters. gonophores on hydranths, hydrocaulus, or Medusa: distinct gastric peduncle; no marginal or hydrorhiza, naked or more usually at least initially in lateral cirri or marginal swellings; with or without a gonotheca, in form of medusae or medusoids with excretory pores; 4- 6 simple radial canals; “gonads” gonads on radial canals. on subumbrellar part of radial canals, not extending Medusa: manubrium small, usually on rather to gastric peduncle; numerous statocysts. well differentiated gastric peduncle; 4-6 simple radi- Reference: Kubota (2000). al canals running from circular canal across under- Remarks: some Eirene species have been side of bell and along peduncle to manubrium; with described only from the hydroid stage with medusa or without excretory papillae or pores; with hollow buds, the adult medusa stage being not known! tentacles; with or without cirri or marginal warts; They must, of course, be considered as indetermi- “gonads” on radial canals separated from manubri- nate species; the eireniid hydroids alone being inad- um, in each species on well defined part(s) of radial equate for generic or specific diagnosis (i.e.: Eirene canal; 8 to many statocysts; without ocelli. troglodyta Watson, 1998).

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Eirene viridula (Péron and Lesueur, 1810) statocysts, without marginal tentacles; with or with- (Figs. 70D-H) out manubrium. Reference: Kubota (2000). Hydroid: not reported from field, description only based on laboratory cultures. Colonies formed by Eugymnanthea inquilina Palombi, 1935 branching or anastomosing stolons with short erected (Figs. 71A-B) hydrocauli each bearing up to ca 5 hydranths; peris- arc smooth to sinuous throughout; hydrothecae Hydroid: epizootic of molluscs bivalves, solitary reduced or lacking, depending on age; hydranths of or forming small colonies; hydranth tubular, without Campanopsis type, with cylindrical body tapering hydrothecae, with a conical hypostome; with a sin- slightly basally and with a conical-rounded hypos- gle whorl of 20-24 filiform tentacles; with an inter- tome, with about 10-24 amphicoronate oral filiform tentacular membranous web, fixed to the host by a tentacles; intertentacular membranous basal web basal disc; often young hydranths budding from the reported; gonothecae long oblong, round-truncated middle part of the primary hydranth body; 1-2 above and below, with thin walls and possibly drop- medusa buds at the basal part of the hydranths. ping during medusa development; gonophore proba- Medusa: umbrella up to 0.55 mm high and wide, bly containing a single medusa bud. without manubrium and tentacles; four simple radial Medusa: umbrella up to 30 mm wide or even canals; four sac-like «gonads» on radial canals, not larger, hemispherical, mesoglea of middle portion of lobular, 8 adradial statocysts with 3 or 4 statoliths. umbrella fairly thick, thinner at sides; velum nar- Records from Mediterranean: eastern and west- row; gastric peduncle elongated, slender, reaching ern Mediterranean, Adriatic. beyond exumbrellar margin; manubrium fairly Known seasonality: 7-9. short, small; mouth with four very long pointed lips Distribution: endemic of Mediterranean Sea with crenulated margins; 4 radial canals an circular References: Kramp (1961); Kubota (1979, 1983, canal narrow; «gonads» linear limited to disk of sub- 1985, 1987); Gili (1986); Gili et al. (1988); Boero umbrella, extending from somewhat beyond base of and Bouillon (1993); Piraino et al. (1994) Avian et peduncle almost to exumbrellar margin, straight, al. (1995). slightly sinuous; about 70 or more marginal tenta- cles of different sizes, small and large alternating, Genus Eutima McCrady, 1859 marginal bulbs conical, with distinct excretory papillae; 50 or more or statocysts. Hydroid: colonies formed either by single Records from Mediterranean: eastern and west- hydranths or by erected colonies arising from creep- ern Mediterranean; Adriatic Sea. ing stolons or by epizoite naked polyps; in non epi- Known seasonality: 2-12. zoite forms the hydrocaulus is with smooth perisarc, Distribution: Atlantic; Indo-Pacific; Mediter- the young colonies have a cylindrical hydrothecae ranean. with diaphragm and a folded pleated operculum References: Kramp (1936, 1961); Gunzl (1959, formed by convergent flaps not demarcated from the 1964); Berhaut (1970); Goy (1973b); Bierbach and hydrothecal rim (Campanulina type); in older Hofmann (1973); Schmidt (1973); Benovic (1976); colonies of this type, the operculum is generally lost Hüdgen (1978); Schmidt and Benovic (1979); and the hydrothecae is reduced to a perisarcal collar Dowidar (1983); Lakkis and Zeidane (1985); looking like an haleciid hydrothecae, usually the Castello i Tortella (1986); Gili (1986); Benovic and hydranths tentacles are connected basally by a mem- Bender (1987); Goy et al. 1988, 1990, 1991); Kub- branous web. ota and Horita (1992); Boero and Bouillon (1993); Medusa: with distinct gastric peduncle; with lat- Cornelius (1995); Avian et al. (1995); Benovic and eral cirri (often difficult to observe and destroyed Lucic (1996); Medel and López-González (1996). after fixation); with marginal swellings or warts; without excretory pores; 4 simple radial canals; Genus Eugymnanthea Palombi, 1935 «gonads» on radial canals, beneath subumbrella or on gastric peduncle or on both; with 8 (exceptional- Hydroid: hydroids epizootic on molluscs ly 12) statocysts. bivalves. References: Brooks (1884, 1886); Bouillon Eirenidae reduced to eumedusoid; with marginal (1985a, 1995a); Cornelius (1995); Kubota (2000).

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Key to hydroids Distribution: Atlantic; Indo- Pacific; Mediter- ranean. Hydroids inadequately known for diagnostic fea- References: Claus (1881); Graeffe (1884); Rus- tures. Eutima gracilis has gonophores including sell (1953, 1970a); Kramp (1961); Berhaut (1970); about eight medusa buds, Eutima. gegenbauri usual- Goy (1973b); Benovic (1973); Schmidt and Benovic ly one (see diagnosis). (1979); Castello i Tortella (1986); Gili (1986); Boero and Bouillon (1993); Cornelius (1995); Avian Key to medusae et al. (1995); Benovic and Lucic (1996); Medel and López-González (1996). 1. With 4 «gonads», restricted to gastric peduncle ...... E. gracilis Eutima gracilis (Forbes and Goodsir, 1851) – With 8 «gonads», 4 on subumbrella, 4 on gastric (Figs. 71H-L) peduncle...... 2 2. Peduncular «gonads» along greater part of Hydroid: not known from field, reared by Wern- gastric peduncle, 4 marginal tentacles ... E. mira er and illustrated by Russell (1970a). Hydranths of – Peduncular «gonads», short, in middle part of Campanulina type, long cylindrical with a single gastric peduncle; 8-18 marginal tentacles...... whorl of about 28 tentacles united by a large mem- ...... E. gegenbauri branous basal web; hydrothecae lacking or strongly reduced; gonothecae cylindrical, long, with truncate Eutima gegenbauri (Haeckel, 1864) end and containing up to 8 developing medusae. (Figs. 71C-G) Medusa: umbrella up to 13 mm wide (exception- ally to 30 mm), almost hemispherical when fully Hydroid: mostly known from reared material, grown, mesoglea thick; with extremely long, narrow only Graeffe (1884) recorded the hydroid in the field gastric peduncle extending far beyond bell margin from the Adriatic Sea. Colonies arising from a and with small conical base; velum fairly narrow; creeping hydrorhiza; hydrocauli short with smooth manubrium short; cross-shaped in transversal section; perisarc reaching the base of the hydranth, hydrothe- mouth with 4 small, simple lips; 4 straight radial cae reduced or lacking in old specimens; hydranths canals and circular canal narrow; 4 «gonads» restrict- of Campanopsis type, club-shaped with a single ed to narrow portion of gastric peduncle, extending whorl a of about 18-20 filiform tentacles connected almost from base of peduncle to manubrium; with 2- basally by a intertentacular membranous web; 4 (sometimes more) long perradial marginal tentacles gonothecae cylindrical on a short stalk, containing without distinct marginal bulb; with 40-80 or more one exceptionally two medusa buds. marginal warts; tentacles and warts usually all with Medusa: umbrella 20 mm wide, almost hemi- one lateral cirri, on each side; 8 statocysts. spherical, apical mesoglea thick; velum narrow; Records from Mediterranean: eastern and west- manubrium short, cross-shaped in transversal sec- ern Mediterranean; Adriatic Sea. tion; gastric peduncle very long, narrow, prismatic, Known seasonality: 2, 4-12. broad based but tapering, extending far beyond Distribution: Atlantic; Indo-Pacific?; Mediter- exumbrella margin; mouth with four short lips with ranean. crenulated margin; 4 straight radial canals and cir- References: Babnik (1948) Russell (1949, cular canal narrow; eight «gonads», four short on 1970a); Kramp (1961); Benovic (1973); Schmidt middle portion of peduncle or nearer manubrium, and Benovic (1979); Benovic and Bender (1987); four on subumbrella extending from base of pedun- Goy et al. (1988, 1990, 1991); Gili et al. (1991); cle almost to umbrella margin; 8-16 marginal tenta- Boero and Bouillon (1993); Cornelius (1995); Avian cles (sometimes up to 32) without marked marginal et al. (1995); Benovic and Lucic (1996); Medel and bulbs and 60-80 marginal warts all with adaxial López-González (1996). excretory papillae armed with cnidocysts; marginal tentacles and marginal warts each with one or two Eutima mira Mc Crady, 1859 (= E. orientalis) lateral cirri; 8 statocysts. (Figs. 72A-B) Records from Mediterranean: eastern and west- ern Mediterranean, Adriatic. Hydroid: the development of this species has Known seasonality: 1-12. been followed by Brooks 1884, 1886, who described

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a “campanulinid” hydroid which can not been attrib- Known seasonality: 7, 10. uted to any specific hydroid species. Distribution: Indo-Pacific; Mediterranean. Medusa: umbrella up to 30 mm wide, usually References: Kramp (1961); Goy (1973b); Boero smaller, as broad as high, nearly hemispherical, and Bouillon (1993); Avian et al. (1995); Benovic mesoglea thick, especially in apical region; with a and Lucic (1996). long slender, tapering gastric peduncle, 2-3 as long as umbrella diameter; manubrium small, flask-shaped, Genus Helgicirrha Hartlaub, 1909 cruciform in section; mouth with 4 simple recurved lips; 4 straight radial canals and narrow circular canal; Hydroid: campanopsid; colony with a net-like 8 elongate sinuous «gonads», 4 on middle third of the hydrorhiza giving rise to unbranched upright peduncle, 4 on subumbrella; 4 long hollow marginal hydranths; hydrorhiza and base of hydranths tentacles with elongated basal marginal bulbs; about enclosed in a thin and sticky perisarc; hydranth 100 marginal warts; marginal bulbs and warts usual- naked, club-shaped, with 26 to 30 amphicoronate ly with lateral cirri; 8 statocysts. filiform tentacles with a small intertentacular web; Records from Mediterranean: eastern Mediter- medusa buds borne in the middle of hydranth or ranean. sometimes even higher, single or up to three per Known seasonality: 4, 5, 11. hydranth. Distribution: Atlantic; Indo-Pacific; Mediter- Medusa: with lateral cirri at the base of some or ranean. all marginal tentacle bulbs; with excretory papillae. References: Kramp (1961); Schmidt (1973, 1976); Dowidar (1983); Goy et al. (1988, 1990, 1. Mouth with long, pointed, crenulated lips ...... 1991); Bouillon (1978a, 1984b, 1995b); Bouillon et ...... H. cari al. (1988b); Boero and Bouillon (1993). – Mouth with rudimentary lips ...... H. shulzei

Genus Eutonina Hartlaub, 1897 Helgicirrha cari (Haeckel, 1864) (Figs. 72D-E) Hydroid: of campanulinid erect type, hydrotheca very delicate, in young specimens cylindrical, with Medusa: umbrella 25-50 mm wide, 6-15 mm diaphragm and conical operculum formed by con- high, rather flat, with thin mesoglea; gastric pedun- vergent sharp flaps not demarcated from hydrothe- cle narrow, short, half as long as umbrella radius; cal rim; in old specimens the hydrotheca disinte- manubrium small; mouth with long lanceolated lips, grates, living just a crumpled membranous collar with crumpled margins; «gonads» linear, narrow, sheath; hydranth very long, with up to 20 amph- extending from near base of peduncle to near icoronate tentacles linked by a basal web; gonothe- umbrella margin; 50-60-short marginal tentacles, ca cylindrical, tapered below, squarely-truncate with large conical marginal bulbs and without later- above, arising from stem just under a hydranth. al cirri; moreover about 100 still smaller tentacles, Medusa: with 8 statocysts; without cirri; without with small conical bulbs, each with one pair of lat- marginal warts; “gonads” restricted to subumbrella, eral cirri; all bulbs with excretory papillae; with not extending onto peduncle. about 100 statocysts. Reference: Rees J.T. (1978) Hydroid: unknown. Records from Mediterranean: western Mediter- Eutonina scintillans (Bigelow, 1909) ranean. (Fig. 72C) Known seasonality: 2, 6, 7, 10. Distribution: Atlantic; Mediterranean. Medusa: umbrella 10 mm wide, 5 mm high, References: Kramp (1936, 1961); Boero and mesoglea thick; with short peduncle; manubrium Bouillon (1993). globular; mouth with 4 simple or crenulated lips; «gonads» along 1/4-1/3 of subumbrellar parts of radi- Helgicirrha schulzei Hartlaub, 1909 al canals; about 30 marginal tentacles; 8 statocysts. (Figs. 72F-J) Hydroid: unknown. Records from Mediterranean: western Mediter- Hydroid: colonies with a net like hydrorhiza giv- ranean; Adriatic Sea. ing rise to unbranched upright hydranths;

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hydrorhiza and base of hydranths enclosed in a thin Records from Mediterranean: western Mediter- and sticky perisarc; hydranths club-shaped, with a ranean; Adriatic. conical hypostome surrounded by 26 to 30 amph- Known seasonality: 3-10. icoronate filiform tentacles linked by a small basal Distribution: endemic of Mediterranean Sea. intertentacular membranous web; medusa buds born References: Kramp (1961); Petersen (1962); Gili in the middle of the hydranths or sometimes even (1986); Brinckmann-Voss (1987); Boero and Bouil- higher, single or up to three per hydranth. lon (1993); Avian et al. (1995); Benovic and Lucic Medusa: umbrella 30-40 mm wide, somewhat (1996); Medel and López-González (1996). flatter than a hemisphere, mesoglea fairly thick; gastric peduncle narrow, elongated conical, Family HALECIIDAE Hincks, 1868 extending beyond umbrella margin; manubrium small, short, somewhat square in transverse sec- Paedomorphic hydrozoa reduced to hydroid tion; mouth with four very short, upwardly curved stage; colonies stolonal or erect arising from a and slightly folded lips; «gonads» on radial canals, creeping hydrorhiza; hydrothecae sessile or pedicel- straight, or sometimes sinuous, extending from late, shallow; hydranth much larger than hydrotheca, near base of peduncle almost to umbrella margin; often robust, with or without intertentacular web, 30-40 large marginal tentacles with elongated con- hydrothecal rim usually even, strongly to scarcely ical marginal bulbs and with or without lateral flaring, hydrothecae lacking operculum; renovation cirri; up to 100 or more small tentacles or rudi- common, regenerated hydrothecae arranged in tiers; mentary bulbs each with one pair of lateral cirri, diaphragm and a ring of large, often birefringent tentacular and rudimentary bulbs with adaxial desmocytes usually present basally; endoderm of excretory papillae; 50 or more statocysts. hydranths differentiated into proximal digestive part Records from Mediterranean: eastern and west- and distal on digestive pert, nematophores nema- ern Mediterranean, Adriatic. tothecae and nematodactyls present or absent; Known seasonality: 1, 3-12. gonophores usually as fixed sporosacs, some species Distribution: Atlantic; Indo-Pacific (Red Sea); with acrocysts, medusa stage totally suppressed Mediterranean. from life cycle except exceptionally as swimming References: Babnik (1948); Kramp (1936, 1961); sporosacs present in one genus (Nemalecium), Bouillon (1971); Goy (1973b); Benovic (1973); gonothecae solitary or grouped into a glomulus, Brinckmann-Voss (1973); Schmidt (1976); Castello infrequently with naked gonophores. i Tortella (1986); Gili (1986); Benovic and Bender Remarks: for the genera Campalecium and (1987); Brinckmann-Voss (1987); Goy et al. (1988, Hydranthea see Lovenellidae. 1990, 1991); Boero and Bouillon (1993); Cornelius References: García Corrales et al. (1978); Calder (1995); Avian et al. (1995); Benovic and Lucic (1991); Cornelius (1975b, 1995, 1998); Migotto (1996); Medel and López-González, (1996). (1996); Calder and Vervoort (1998); Medel and Ver- voort (2000); Watson (2000). Genus Neotima Petersen 1962 1. Colonies without nematothecae...... Halecium Eutimidae with 8 statocysts, without cirri; with – Colonies with nematothecae ...... Hydrodendron marginal warts; with «gonads» on entire length of radial canals. Hydroid unknown. Genus Halecium Oken, 1815 = Baleum Billard, 1929 = Plumalecium Antsulevich, 1982 Neotima lucullana (Delle Chiaje, 1822) = Sagamihydra Hirohito, 1995 (Figs. 73A-B) Hydroid: colony usually erect, monosiphonic or Medusa: umbrella up to 74 mm wide, flatter than polysiphonic, branched or unbranched, arising from a hemisphere, mesoglea thin; gastric peduncle with a creeping hydrorhiza, stem and branches divided in broad base, somewhat longer than umbrella cavity, internodes bearing apophyses near distal end; manubrium small; mouth with large crenulated lips; hydrothecae alternate, sessile or pedicellate, borne 60-70 short marginal tentacles, 7 marginal warts on apophyses when not pedicellate, shallow; rim between successive tentacles; 8 statocysts. commonly everted and regenerated; a ring of large Hydroid: unknown. desmocytes and a basal diaphragm; hydranth not

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retractable into hydrotheca, often with an annular hydrophores...... 12 bugle half way up the gastric column; intertentacu- 12.Colonies pinnate, hydrocladia straight, parallel; lar web present or not; nematophores and nemato- female gonothecae with pair of hydrothecae dactyls absent; gonophores as fixed sporosacs some- opening distally...... H. halecinum times with acrocyst, gonothecae either solitary or – Colonies bushy, not regularly pinnate, branches aggregated to form a glomulus, usually sexually flexuous; female gonothecae kidney-shaped; dimorphic, sometimes with gonophoral polyps or hydrothecae opening in centre of concavity ...... arising from within hydrothecae; typically sexually ...... H. beanii. dimorphic. References: Calder (1991); Cornelius (1975, Halecium banyulense Motz-Kossowska (1911) 1995, 1998); Hirohito (1995); Migotto (1996); (Figs. 73C-E) Pagliara et al. (2000). Colonies with polysiphonic and densely 1. Hydrotheca recurved at the rim...... 2 branched hydrocauli; only the extreme of branching – Hydrotheca not recurved at the rim ...... 7 monosiphonic. Perisarc thick, but thinner towards 2. Comma-shaped perisarc fold present at the base distal end of branches. Hydrotheca deep, margin of hydrophores ...... H. sibogae everted. Female gonophores borne on stem and – Hydrophores without this character ...... 3 hydrocladia, numerous, with longitudinal undula- 3. Internodes smooth ...... 4 tions; male gonophores shorter than females, borne – Internodes with annulations ...... 6 on upper parts of the colony, more or less smooth. 4. Nodes oblique...... 5 Records from Mediterranean: western Mediter- – Nodes transverse...... H. tenellum ranean. 5. Primary hydrotheca separated from the Seasonality: ? apophysis by a node, gonothecae with rows of Distribution: endemic of Mediterranean Sea. spines...... H. muricatum References: Motz-Kossowska (1911); Picard – Without these characters; hydrothecae with (1958b); Boero and Bouillon (1993). abcauline thickening...... H. delicatulum 6. Monosiphonic colonies with regularly annulated Halecium beanii (Johnston, 1838) internodes; gonothecae corrugated and without (Figs. 73F-J) terminal aperture...... H. pusillum – Polysiphonic colonies with irregularly Adult colonies up to ca 250 mm, composed of undulated internodes; female gonothecae not erect, polysiphonic and pinnately branched hydro- corrugated and with terminal aperture ...... cauli; hydrocladia alternate, in the same plane, flex- ...... H. labrosum uose, varied in length, some of them branched. 7. Internodes of varied length and with undulations Hydrocladia (but not their branching) borne lateral- ...... 8 ly, originate from base of hydrothecae, these becom- – Internodes of equal length...... 9 ing axillary. Monosiphonic parts of the axis and 8. Nodes distinct; female gonothecae not hydrocladia separated into internodes by means of corrugated and without distal hydrotheca ...... slightly oblique nodes; hydrothecae borne laterally, ...... H. lankesteri alternate, at upper part of internodes. Hydrotheca – No distinct nodes, several undulations present; shallow, walls almost parallel, rim not everted. Pri- female gonothecae corrugated and with two mary hydrotheca sessile; renovation frequent, all hydrothecae opening distally...... H. nanum with hydrophores of similar length, smooth and 9. Hydrothecae sessile ...... 10 short. Female gonotheca kidney-shaped, with two – Hydrothecae with a short hydrophore...... hydrothecae in the middle of concave side; male ...... H. petrosum ovoid, elongated, with a terminal aperture. 10.Hydrothecae shallow ...... 11 Records from Mediterranean: western Mediter- – Hydrothecae deep, internodes with a thick ranean, Adriatic. perisarc ...... H. liouvillei Known seasonality: 2, 4-12. 11.Hydrothecal renovations sessile, without Reproduction: 9 hydrophores...... H. sessile Distribution: eastern and western Atlantic, Indo- – Hydrothecal renovations provided with distinct Pacific, Arctic, sub-Antarctic, Mediterranean.

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References: Millard (1975); Calder (1991); and Vervoort (2000); Peña Cantero and Carrascosa Boero and Bouillon (1993); Avian et al. (1995); (2002). Cornelius (1995); Medel and López-González (1996); Medel, García and Vervoort (1998); Medel Halecium halecinum (Linnaeus, 1758) and Vervoort (2000); Schuchert (2001a). (Figs. 74E-J)

Halecium conicum Stechow, 1919 Well developed colonies with stiffly erect, poly- (Figs. 73K-M) siphonic and pinnately branched hydrocauli up to 190 mm high; hydrocladia straight, alternate, in the Colonies small, slightly branched, with maxi- same plane, at constant angle of 40º-60º to the main mum 5 to 6 hydrothecae; hydrotheca conical, large, axis, arising frontally or backwards of the hydrothe- relatively deep, rim slightly everted, gonophores cae. Monosiphonic parts of the axis and hydrocladia generally on hydrorhiza, irregular, almost ovalate in divided into internodes by means of slightly oblique female, more slender in male. nodes. Hydrothecae borne laterally, alternate, at Records from Mediterranean: western Mediter- upper part of internodes. Hydrotheca shallow, with ranean. almost parallel walls, rim not everted; primary Known seasonality: 10-6. hydrotheca sessile, adcauline side close to intern- Distribution: endemic of Mediterranean Sea. ode; several renovations may occurs, these Reference: as Halecium minutum by Motz-Kos- hydrothecae with hydrophores of varied lengths, but sowska (1911). usually secondary hydrotheca with the longest one. Male gonothecae ovoid and elongated; female grad- Halecium delicatulum Coughtrey, 1876 ually widening towards truncated distal end, aper- (Figs. 74A-D) ture on side with two hydrothecae, on the other side a shoulder more or less developed. Colonies up to 25 mm composed of monosi- Records from Mediterranean: eastern and west- phonic or polysiphonic and irregularly branched ern Mediterranean, Adriatic. hydrocauli, often growing in dense groups. Stem Known seasonality: present all the year. and branches internodes separated by oblique nodes Reproduction: 1,5,10. alternately directed left and right; hydrantophores Distribution: eastern and western Atlantic, well developed, alternate, borne laterally at the Mediterranean, Indo-Pacific, Arctic. upper part of internodes and ended by hydrothecae. References: Naumov (1960); Patriti (1970); Mil- Hydrotheca shallow, widening towards the aperture, lard (1975); Boero and Bouillon (1993); Avian et al. rim even, circular and everted; with diaphragm (1995); Cornelius (1995, 1998); Medel and López- basally; also a perisarcal thickening (pseudodi- González (1996); Medel, García and Vervoort aphragm) at adcauline side of the hydrotheca is pre- (1998); Medel and Vervoort (2000); Schuchert sent; wall with desmocytes for attachment of the (2001a). hydranth; several hydrothecae may originate from previous one, with more or less development of their Halecium labrosum Alder, 1859 hydranthophores. Male gonotheca ovoid and elon- (Figs. 74K-P) gated, compressed laterally; female gonotheca almost spherical and slightly compressed laterally; Hydrocauli erect and polysiphonic, up to 100 aperture circular. mm high. Internodes provided with irregular undu- Records from Mediterranean: western Mediter- lations, each inserted laterally at distal part of previ- ranean. ous internode with characteristic upward curve near Known seasonality: almost always present. base; nodes no distinct. Hydrotheca at the end of Reproduction: 4-11. internode; short, rim everted and recurved down- Distribution: eastern and western Atlantic, wards; renovations frequent. Gonothecae borne on Mediterranean, Pacific, Arctic, Antarctic. short 1-2 ringed pedicels, without gonophoral References: Patriti (1970); Vervoort (1972); Mil- hydranths; male oval and elongated, aperture distal, lard (1975); Ramil and Vervoort (1992a); Boero and small; female ovoid, large, aperture on short collar. Bouillon (1993); Medel and López-González Records from Mediterranean: eastern and west- (1996); Medel, García and Vervoort (1998); Medel ern Mediterranean, Adriatic.

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Known seasonality: 7-2. from inside of hydrotheca, on annulated pedicel nar- Reproduction: 9, 10, 12, 2. rower basally, gradually widening towards distal Distribution: eastern and western Atlantic, end, this being truncated with two adnate hydrothe- Mediterranean, Pacific, Arctic. cae on side and a shoulder on the other side. Male References: Gili (1986); Ramil (1988); Ramil gonotheca unknown. and Iglesias (1988a); Boero and Bouillon (1993); Records from Mediterranean: western Mediter- Altuna (1994); Avian et al. (1995); Cornelius (1995, ranean. 1998); Medel and López-González (1996); Known seasonality: 2, 5. Schuchert (2001a). Reproduction: 2. Distribution: eastern Atlantic, Mediterranean. Halecium lankesteri (Bourne, 1890) References: Billard (1934); Patriti (1970); Ramil (Figs. 75A-C) and Iglesias (1988a); Altuna (1994); Medel, García and Vervoort (1998); Medel and Vervoort (2000). Colonies monosiphonic, up to 80 mm, erect inside the water, unbranched or imperfectly pinnate. Halecium mediterraneum Weissman, 1883 Internodes of irregular length, separated by slightly oblique nodes, 0-10 (usually 1) internodes between Colonies erect, hydrocauli monosiphonic and hydrothecae. Hydrotheca borne laterally, alternate, branched, hydrophores borne laterally at the upper at distal end of internode; sessile, short, walls almost part of internodes, nodes oblique, annulations at parallel, rim not everted, aperture directed outwards, nodes may be present. Primary hydrotheca on well almost at right angle with the main axis; renovations developed hydrophore; rim everted; hydrothecal frequent. Gonothecae borne on short pedicels below renovations frequent. Gonothecae pear-shaped, hydrothecae; male ovoid and elongated, aperture somewhat elongate and with smooth perisarc. distal; female kidney-shaped, aperture laterally, at Remarks: the description of H. mediterraneum the end of a tube at distal third, with 1-2 hydranths. by Gili (1986) is not according with his drawings, Records from Mediterranean: eastern western which resembles to H. delicatulum; the description Mediterranean, Adriatic. and drawings of H. mediterraneum by Llobet Known seasonality: 4-11. (1987) are according too with the species H. deli- Reproduction: 7-11. catulum. Medel and López-González (1996) con- Distribution: eastern Atlantic, Indian Ocean, sider H. mediterraneum as conspecific with H. del- Mediterranean. icatulum; in the present work it is considered as a References: Millard (1975); Gili (1986); Ramil doubtful species. and Iglesias (1988a); Boero and Bouillon (1993); Altuna (1994); Cornelius (1995, 1998); Medel and Halecium muricatum (Ellis and Solander, 1786) López-González (1996); Peña Cantero and García (Figs. 75G-J) Carrascosa (2002). Big colonies composed of erect, polysiphonic Halecium liouvillei Billard, 1934 and branched hydrocauli up to 200 mm. Internodes (Figs. 75D-F) separated by transverse to oblique nodes. Hydrothe- cae laterally, alternate at distal end of internodes, Hydrocauli erect, up to ca 34 mm, monosiphon- borne on short apophyses ended by a node and pro- ic or polysiphonic basally, branched or unbranched. vided with hydrophores; several renovations may Axis with a zigzag appearance; often with some occurs. Hydrotheca short, walls gradually diverging, annulations basally. Internodes with thick perisarc; rim even and curved downwards. Male and female nodes oblique. Primary hydrotheca alternate, borne gonothecae similar, borne on short and thin pedicels, laterally at upper part of internodes; sessile, deep, ovoid and flattened, provided with rows of spines, walls gradually diverging from base onward, without gonophoral hydranths; growing on main adcauline side usually longer than abcauline one; stem or, occasionally, in stolons. adcauline wall separated from internode; hydrothe- Records from Mediterranean: western Mediter- cal rim occasionally everted but not recurved; reno- ranean. vations frequent, but secondary hydrophores usually Known seasonality: 11. longer and annulated. Female gonotheca arising Reproduction: 11.

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Distribution: eastern and western? Atlantic, Records from Mediterranean: western Mediter- Mediterranean, Pacific, Arctic. ranean, Adriatic. References: Vervoort (1946); Naumov (1960); Known seasonality: always present. Gili (1982); Boero and Bouillon (1993); Medel and Reproduction: 8-11. López-González (1996); Cornelius (1995, 1998); Distribution: endemic of the Mediterranean Sea. Schuchert (2001a). References: Motz-Kossowska (1911) as H. robustum?; Stechow (1923d); García-Carrascosa Halecium nanum Alder, 1859 (1981); Llobet (1987); Peña Cantero and García (Figs. 75K-M) Carrascosa (2002).

Hydrocauli monosiphonic, up to 3 mm, Halecium pusillum (M. Sars, 1857) unbranched or irregularly branched in several planes, (Figs. 76D-G) sometimes dichotomously. Internodes borne laterally at upper part of previous internode, narrowed, curved Colonies delicate, composed of stolon giving rise and with several annulations basally; smooth distal- to erect and monosiphonic hydrocauli. Perisarc of ly; no distinct nodes. Primary hydrotheca at distal internodes thin and annulated throughout; apical end of each internode, sessile, shallow, walls fre- stolons frequent. Hydrothecae at end of each intern- quently thick and diverging, but not everted at the ode, branches originating laterally, below hydrothe- rim; secondary hydrothecae provided with cae, curved at base. Hydrothecae shallow, walls hydrophores also annulated basally. Gonophores straight at basal half and curved outward at distal fixed sporosacs. Female gonothecae sac-shaped, half. Female gonothecae ringed throughout, with a borne on short pedicels arising on lateral apophysis lateral aperture provided with two hydranth; male to the hydrothecae; one side of gonotheca with two gonothecae oval, elongated and with transverse closely adpressed tubes largely immersed in undulations. gonothecal wall and annulated, each topped by a Records from Mediterranean: western Mediter- hydrotheca provided with hydranth; opposite side of ranean. gonotheca convex; male gonothecae? Known seasonality: 1-12. Records from Mediterranean: western and east- Reproduction: 2-4, 10 ern Mediterranean, Adriatic. Distribution: eastern and western Atlantic, Known seasonality: 4-12. Mediterranean, Indic, Pacific?. Distribution: eastern and western Atlantic, References: Gili (1986); Ramil and Iglesias Mediterranean, Pacific?. (1988a); Boero and Bouillon (1993); Avian et al. References: Calder (1991); Boero and Bouillon (1995); Medel, García and Vervoort (1998); Peña (1993); Avian et al. (1995); Cornelius (1995); Cantero and García Carrascosa (2002). Medel and López-González (1996); Medel, García and Vervoort (1998); Medel and Vervoort (2000). Halecium reflexum Stechow, 1919

Halecium petrosum Stechow, 1919 Following Cornelius (1975; 1995), Roca (1986) (Figs. 76A-C) and Altuna (1994) this species is here provisionally considered as conspecific with H. labrosum. Hydrocauli monosiphonic, up to 35 mm robust, stiff, with a thick perisarc; hydrotheca alternate, lat- Halecium sessile Norman, 1867 erally at the end of each internode; nodes oblique. (Fig. 76H-L) Hydrotheca sessile, but adcauline wall not adnate to the axis; walls gradually widening towards distally, Colonies up to 50 mm, monosiphonic or polysi- rim not flared; hydrothecal renovations frequent, phonic and branched; larger colonies more or less secondary hydrantophore large and with undulate pinnate, with several order of branching and in sev- perisarc. Female gonothecae big, borne on eral planes. Internodes geniculate or not, nodes hydrorhiza or on hydrocauli, ovoid to spherical transverse to slightly oblique. Hydrocladia borne on aperture apical with two hydranths; male gonothe- distal apophysis below primary hydrothecae. cae arising from inside of the hydrotheca or below Hydrothecae laterally at distal part of internodes; it, sac-shaped, elongated. very shallow, walls gradually diverging, rim even,

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not everted; aperture at right angle with the axis of Halecium tenellum Hincks, 1861 internode; hydrothecal renovation frequent, sec- (Figs. 77A-E) ondary hydrothecae usually forming directly on diaphragm of previous hydrothecae, appearing sev- Colonies composed of hydrocauli monosiphonic eral hydrothecal rim very closed. Female gonothe- up to 20 mm high, very thin and delicate, irregularly cae kidney shaped, with a tubular aperture on con- branched. Internodes long, in zigzag, separated by cave side with two hydranths. Male gonothecae transverse nodes. Hydrothecae borne laterally at upper oval, elongated, slightly curved; aperture terminal. part of internodes, alternate and provided with a well Records from Mediterranean: western Mediter- developed hydrophore; hydrotheca shallow, walls ranean. widening from base to top giving a wide aperture; rim Known seasonality: 6. everted and curved outwards. Secondary hydrotheca, Distribution: eastern and western Atlantic, provided with hydrophore, may occurs from primary Mediterranean, Indo-Pacific. hydrothecae; branching may originate from hydrothe- References: Vervoort (1966); Ramil and Vervoort cal base. Male gonothecae ovate and flattened; female (1992a); Boero and Bouillon 1993; Altuna (1994); similar but slightly larger and broader. Cornelius (1995, 1998); Medel and López-González Records from Mediterranean: western Mediter- (1996); Schuchert (2001a). ranean, Adriatic, Algeria, Black Sea. Known seasonality: 10-5, 7, 9. Halecium sibogae Billard, 1934 Reproduction: 4-5. (Figs. 76M-O) Distribution: eastern and western Atlantic, Mediterranean, Indo-Pacific, Arctic, Antarctic. Hydrocauli erect, up to 90 mm, polysiphonic and References: Vervoort (1959); Naumov (1960); pinnately branched; perisarc thick in older parts. Patriti (1970); Millard (1975); Boero and Bouillon Distal parts of the colony monosiphonic, internodes (1993); Cornelius (1995, 1998); Migotto (1996); geniculate, nodes oblique. Each internode distally Medel, García and Vervoort (1998); Medel and Ver- with well developed primary hydrophore; next voort (2000); Schuchert (2001a). internode borne laterally to the hydrophore without distinct apophysis. Adcauline wall of primary Genus Hydrodendron Hincks, 1874 hydrophore at place of fusion with wall of internode = Ophiodissa, 1919a = Scoresbia Watson, 1969 with characteristic comma-shaped internal perisar- cal fold. Hydrotheca with distinct basal diaphragm Colonies stolonal or erect, monosiphonic or and widening distally, rim flared. Hydrothecal reno- polysiphonic; hydrothecae short cylindrical, haleci- vations frequent, secondary hydrophores sometimes id type, pedicellate or on internodal apophyses, in with one-two basal annulations; length varied. Male two alternate rows in erect colonies, basal part with and female gonothecae similar, almost spherical, or without desmocytes; hydranth with or without an frequently showing a quadrangular cross section, intertentacular web; nematophore extensile, elon- and with one or two more or less developed basal gate, simple-ended or capitate; nematotheca, when projections, more pronounced in the female present, simple, sometimes minute; gonophores as gononothecae, and apically with two more or less solitary fixed sporosacs, gonothecae simple or developed elevations between which is situated the aggregated in a glomulus. aperture at the end of a cone. Remark: the Genus Hydrodendron is here Records from Mediterranean: Alborán Sea defined as by Rees and Vervoort (1987) and Ver- (species penetrating into the Mediterranean but voort (1987) so to include, among others, the genera probably not yet dispersed in it). Ophiodissa and Scoresbia. Known seasonality: 6-8. References: Calder (1991); Cornelius (1995); Reproduction: 7. Hirohito (1995). Distribution: eastern Atlantic warm waters, Mediterranean. Hydrodendron mirabile (Hincks, 1866) References: Billard (1934); Patriti (1970); Ramil (Figs. 77F-K) and Vervoort (1992a); Medel and López-González (1996); Medel et al. (1998); Medel and Vervoort Colonies up to 50 mm, composed of erect and (2000); Peña Cantero and García Carrascosa (2002). monosiphonic hydrocauli branched distally. Intern-

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odes separated by transverse nodes. Hydrophores mastigophores of several size classes, sometimes borne laterally, alternate, at upper part of internodes, isorhizas, microbasic euryteles and pseudostenoteles; variable in length and usually with several annula- gonophores as fixed sporosacs contained in a simple tions; perisarc of hydrophores thicker basally and gonotheca, usually solitary, arising from caulus or progressively thinner towards the distal end. hydrocladia, neither aggregated or protected by phy- Hydrotheca deep, widening from halfway onward, lactocarps, frequently sexually dimorphic, with at rim everted, occasionally curved downwards. least the female normally bearing nematothecae. Nematothecae present on hydrorhiza and on References: Cornelius (1995), Migotto (1996); hydrophores, tubular in basal 2/3, cup-shaped distal- Calder (1997); Schuchert (1997); Peña Cantero et ly; nematophores elongate, capitate distally, strong- al., (1999); Watson (2000); Ansín Agís et al. (2001); ly retractile. Stems with distal stolons developing Schuchert (2001). from hydrothecae. Hydranth provided with 20 tenta- cles. Gonothecae borne hydrorhiza, on short 1. Unbranched erect stems arising directly from pedicels, barrel-shaped spacely ringed throughout, creeping hydrorhiza; without hydrocladia ...... aperture wide on a short collar...... Antennella Records from Mediterranean: eastern and west- – Erect structures branched, either as cormoids, ern Mediterranean, Adriatic. branched hydrocladia or polysiphonic stems... 2 Known seasonality: 2, 4, 6, 7, 10-12. 2. Hydrocladia with large “mamelons” (atrophied Reproduction: 7 hydrothecae) ...... 3 Distribution: eastern and western Atlantic, Indo- – Hydrocladia without “mamelons”...... 4 Pacific, Mediterranean. 3. With unbranched hydrocladia.. Pseudoplumaria References: Rees and Vervoort (1987); Gili, Ver- – With hydrocladia branched in a regular fashion . voort and Pagès (1989); Boero and Bouillon (1993); ...... Polyplumaria Medel and López-González (1996) both as 4. Stem normally monosiphonic, cormoids pinnate Ophiodissa; Cornelius (1995); Medel, García and ...... Halopteris Vervoort (1998); Medel and Vervoort (2000); Peña – Stem polysiphonic and with one main axial tube Cantero and García Carrascosa (2002). bearing hydrocladia ...... Schizotricha

Family HALOPTERIDIDAE Millard, 1962 Genus Antennella Allman, 1877

Colonies with either erect hydrocauli, or with Hydrocladia arising directly, independently, from a hydrocladia arising directly from hydrorhiza; hydro- creeping hydrorhiza, normally unbranched, not poly- caulus, when present, branched or unbranched, siphonic; hydrotheca cup- to vase-shaped, rim even monosiphonic or polysiphonic, arising from a creep- untoothed; nematotheca two-chambered, movable; ing or root-like hydrorhiza, giving rise to alternate or lateral nematothecae flanking each hydrotheca and opposite, or irregularly arranged, branched or borne on prominent peduncles adhering to hydrothe- unbranched, hydrocladia; when arising from polysi- cal wall; colony often monoecious, gonophores as phonic hydrocauli and branches, hydrocladia given fixed sporosacs, gonotheca solitary, sexually dimor- off from either a single axial tube or from superficial phic, borne on hydrocladia with basal nematothecae. tubes; hydrothecae on hydrocladia typically large, References: Hirohito (1995); Calder (1997); with cusped or uncusped rim; cauline hydrothecae Schuchert (1997). typically present, well developed, less frequently atrophied, lacking on polysiphonic hydrocladia and 1. Ahydrothecate internodes with one single distal branches, when component tubes give rise to hydro- nematotheca, colonies dioecious...... A. ansini cladia; nematophores with nematothecae, not as – Ahydrothecate internodes with two median naked sarcostyles; nemathothecae typically well nematothecae, colonies monoecious ...... 2 developed, varied in structure, one- or two-cham- 2. Hydrotheca surrounded by four nematothecae; bered, movable or immovable, not fused to hydrothe- distal chamber of lateral nematothecae widening cae (except in the lateral nematothecae of Antennel- distally...... A. secundaria lopsis which are partly fused); a minimum of three, – Hydrotheca surrounded by three nematothecae; one median inferior and a pair of lateral, adjacent to distal chamber of lateral nematothecae globose, each hydrotheca; cnidome: usually microbasic with two deep emargination...... A. siliquosa

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Antennella ansini cup-shaped, walls parallel to slightly divergent, 1/3 Peña Cantero and García Carrascosa (2002) to 1/2 adnate, rim even, aperture at 45º-55º with the (Figs. 77L-O) main axis. Nematothecae all two-chambered and with a very wide embayment; median inferior Colonies with solonal hydrorhiza giving small inmovable, not reaching the level of the hydrotheca, unbranched stems, proximal part of stem composed median nematotheca on the internodes similar; axil- of one or several ahydrothecate internodes bearing lar nematotheca similar but much shorter than the up to 3 nematothecae. Remaining stem composed of first; lateral nematothecae movable, borne on well alternately arranged hydrothecate and ahydrothecate developed pedicels; basal chamber elongated, distal internodes. Stem with up to 12 hydrothecae. chamber widening distally. Gonothecae of both Hydrothecal internode with one hydrotheca and sexes often on the same axis, borne under hydrothe- three nematotheca, one mesial inferior and two lat- cae, on pedicels of two segments ; female elongat- erals. Mesial nematothecae short without apohysis, ed, cylindrical, narrowed basally, with a circular lid lateral nematothecae short, on short apophyses, dis- and two opposite basal nematothecae; male shorter, tal part rounded with deeply scooped inner and outer curved, also provided with two basal lateral nema- walls. Ahydrothecate internodes longer than tothecae. hydrothecate ones with a single distal nematothecae. Records from Mediterranean: eastern and west- All nematothecae two-chambered.. Hydrothecae ern Mediterranean, Adriatic. abcaudally directed, cup-shaped, slightly widening Known seasonality: present all the year. at their aperture, adcauline wall free for approxima- Reproduction: 3 -11. tively half its length, abcauline wall slightly convex. Distribution: cosmopolitan species with a prefer- Hydrothecal aperture circular, rim slightly laterally ence for warmer waters. depressed. Colonies dioecious. Gonothecae usually References: Patriti (1970); Millard (1975); Gili on basal internodes, on short antero-lateral apoph- and García-Rubíes (1985); Ramil (1988); Cornelius ysis, up to two gonophores per stem. Male and Ryland (1990); Ramil and Vervoort (1992a); gonophore fusiform basally curved with one or two Boero and Bouillon (1993); Avian et al. (1995); nematothecae, aperture circular, situated at distal Medel and Vervoort (1995); Medel, and López- truncated part of gonothecae. female gonotheca on González (1996); Schuchert (1997); Ansín Agís et short apohysis with short basal segment strongly al. (2001); Peña Cantero and García Carrascosa flattened carrying one or two nematothecae, aper- (2002). ture larger than in male gonothecae. Records from Mediterranean: western Mediter- Antennella siliquosa (Hincks, 1877) ranean. (Figs. 78E-I) Known seasonality: 5, 7, 8. Reproduction: 5, 7, 8. Ramified stolons with upright and unbranched Distribution: eastern Atlantic; Mediterranean. stems up to 45 mm high, with a whitish coenosarc. References: Peña Cantero and García Carrascosa Basal part of the axis divided on a variable number (2002). of segments bearing frontal nematothecae by means of transverse nodes; remainder parts heteromerously Antennella secundaria (Gmelin, 1791) segmented, with nodes alternatively oblique and (Figs. 77P, 78A-D) transverse. Hydrothecate segments with one hydrothecae and three nematothecae, one median Colonies forming ramified, tubular stolons with inferior, and two laterals ones. Non-hydrothecate erect stems, usually unbranched up to about 25mm; segments bearing two median nematothecae. coenosarc reddish. Basal part of the axis divided Hydrotheca cylindrical, walls almost parallel, slight- into several internodes by transverse nodes, with a ly divergent distally, 1/2 adnate, rim even, aperture variable number of nematothecae. Rest of the stem at 35º-45º with the main axis. Nematothecae all two- heteromerously segmented. Hydrothecate segments chambered, aperture with embayment. Median with one hydrothecae surrounded by four nema- nematothecae all similar, but median inferior to the tothecae, one median inferior inmovable, one pair of hydrotheca wider, this one not reaching the level of laterals, and one axillar. Non-hydrothecate intern- the hydrotheca; lateral nematothecae borne on odes with two median nematothecae. Hydrotheca pedicels, not reaching the hydrothecal margin, basal

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chamber longer and elongated if compared with the nematothecae ...... H. catharina rest; distal chamber typically globose, with a deep – Hydrotheca with one pair of lateral nematothecae emargination on inner and outer side. Gonothecae ...... H. diaphana on both sexes on the same axis, borne on pedicels with two segments. Female elongate, somewhat flat- Halopteris catharina (Johnston, 1833) tened, truncated distally and curved basally, with up (Figs. 78J-N) to four nematotheca; male shorter, pyriform, extreme rounded; two basal nematothecae, both Colonies pinnate up to 40 mm high arising from with apical flat lid. branched stolons; stems monosiphonic and Records from Mediterranean: western Mediter- unbranched. Basal part composed of several seg- ranean, Adriatic. ments bearing two longitudinal rows of nematothe- Known seasonality: 5-10. cae, nodes transverse. Remainder axis heteromer- Reproduction: 5, 7, 9, 10. ously segmented by alternate oblique and transverse Distribution: eastern Atlantic (England, France, nodes. Hydrocladia opposite, borne laterally bellow Strait of Gibraltar, Morocco, Ivory Coast), Mediter- hydrothecae, on long stem apophyses. Hydrothecate ranean. segments with one hydrothecae and five nematothe- References: Vervoort (1959) as Antennella cae, one median inferior and two pairs of lateral diaphana f. siliquosa; Patriti (1970); García Cor- ones. Non-hydrothecate segments with one to four rales et al. (1978); Ramil and Vervoort (1992a) both nematothecae. Hydrocladia with a first athecate seg- as Halopteris diaphana f. siliquosa; Boero and ment; remainder segments as in the main axis, but Bouillon (1993); Avian et al. (1995); Medel and non-hydrothecates with 1-2 nematothecae. Vervoort (1995); Medel and López-González Hydrothecae cup-shaped, in the middle of the (1996); Schuchert (1997); Ansín Agís et al. (2001). internode, walls straight almost parallel, 1/2 adnate, rim smooth, aperture at 45º with the axis. Nema- Genus Halopteris Allman, 1877 tothecae all two-chambered and movable, upper chamber with a deep embayment. Outer pair of lat- Colonies typically erect, unbranched or branched, eral nematothecae reaching the rim or slightly forming pinnate cormoids arising from a creeping beyond it, on long apophyses; inner pair at base of hydrorhiza, often with a hinge-joint near base; hydro- those apophyses. Gonothecae of both sexes on the caulus usually monosiphonic, rarely polysiphonic, same colony, on the stem and hydrocladia. Female bearing hydrothecae and pinnately arranged hydro- cylindrical somewhat flattened, narrowed at base, cladia; in polysiphonic stems, all tubes can give rise with two nematothecae; truncated distally, with to cormidia; hydrocladia almost always unbranched, annular thickening and lid; basal pedicel with two alternate or in opposite pairs, or opposite basally and segments. Male gonothecae smaller and elongated. alternate distally, in one plane, sometimes (as sec- Records from Mediterranean: western and east- ondary growth-form) arising independently from ern Mediterranean. hydrorhiza; hydrothecae cup-shaped, on hydrocaulus Known seasonality: 1-4, 6-8, 12. and hydrocladia, margin entire or with one median Reproduction: 3, 6. abcauline cusp; nematothecae polymorphic, movable Distribution: temperate and southern-boreal or immovable ones on a given colony, one- or two- regions of the eastern and western sides of the chambered, lateral nemathotecae typically borne on Atlantic. prominent peduncles adhering to hydrothecal wall; References: Picard (1958b); Vervoort (1972); gonophores as fixed sporosacs, gonothecae arising Ramil and Vervoort (1992a); Boero and Bouillon from hydrocaulus or hydrocladia, solitary, with or (1993); Cornelius (1995); Medel and López without nematothecae. González (1996); Schuchert (1997, 2001a); Ansín References: Hirohito (1995); Calder (1997); Agís et al. (2001). Schuchert (1997). Halopteris diaphana (Heller, 1868) 1. Main axis homomerously segmented...... (Figs. 78O-T) ...... H. liechtensternii – Main axis heteromerously segmented...... 2 Colonies pinnate with erect, monosiphonic and 2. Hydrotheca with two pairs of lateral unbranched stems up to 12 mm. Basal parts with a

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varied number of segments separated by transverse eral ones, seated on short pedicels and reaching the nodes bearing a row of median nematothecae. hydrothecal rim, two axillar and two or three medi- Remainder parts of the axis heteromerously seg- an superior. Hydrothecate segments on hydrocladia mented, with alternate oblique and transverse nodes. with one hydrothecae surrounded by five nema- Hydrocladia alternate, on apophyses laterally to the tothecae (one median inferior, two laterals, and two hydrothecae. Hydrothecate internodes of the main smaller ones on the upper axil of the hydrothecae); axis and hydrocladia composed of one hydrothecae non-hydrothecate segments with 1-2 median nema- and three nematothecae, one median inferior and tothecae. Hydrotheca cup-shaped, walls slightly two laterals. Non-hydrothecate segments with 1-2 diverging towards margin, adcauline wall 1/2 median nematothecae (usually one on the hydrocla- adnate, rim even and circular, aperture at 40º-50º dia). Hydrotheca in the middle of the segment, cup- with the main axis. Nematothecae all two cham- shaped, walls slightly widening, 1/2 adnate, rim bered. Median inferior nematotheca with a distal even, aperture at 50º-60º with the axis. All nema- chamber scoop-shaped, without adcauline wall; lat- tothecae two chambered and movable, with eral nematotheca with a longer basal chamber; mar- adcauline embayment. Median inferior nematotheca gin of the distal chamber even or with shallow not reaching the hydrotheca, lateral ones on very emarginations on adcauline wall; pair of nema- short apophyses, just reaching the hydrothecal bor- tothecae behind hydrothecae reduced, indistinctly der. Gonothecae of both sexes only seen on separate two-chambered, scoop-shaped; remainder nema- colonies, on stem and hydrocladia, with two seg- tothecae similar to median inferior ones, but longer. mented pedicels. Female evenly curved for its entire Gonothecae of both sexes on same colony. Female length, narrowed basally, with 2-4 basal nematothe- borne on stem and hydrocladia, on two-segmented cae; distal end truncate, with a convex lid. Male pedicels; oval, truncated distally, with thickened gonothecae oblong, slightly curved, with 2 basal ring of prosaic and lid; two basal nematothecae. nematothecae. Male borne on hydrocladia, smaller, sac-shaped and Records from Mediterranean: western and east- without nematothecae. ern Mediterranean, Adriatic. Records from Mediterranean: eastern and west- Known seasonality: 1, 2, 4-10. ern Mediterranean and Adriatic (central Mediter- Reproduction: 4, 6-9. ranean?). Distribution: circumtropical species. Known seasonality: 3, 5-10. References: Boero and Bouillon (1993); Avian et Reproduction: 5-8, 10. al. (1995); Medel and Vervoort (1995); Medel and Distribution: endemic of Mediterranean Sea. López-González (1996); Schuchert (1997); Ansín References: Motz-Kossowska (1908) as Plumu- Agís et al. (2001); Peña Cantero and García Carras- laria; Rossi (1961); Boero and Bouillon (1993); cosa (2002). Medel and Vervoort (1995); Medel and López- González (1996); Schuchert (1997); Avian et al. Halopteris liechtensternii (1995); Peña Cantero and García Carrascosa (2002) Marktanner-Turneretscher, 1890 (Figs. 79A-G) Genus Polyplumaria G. O. Sars, 1874

Colonies pinnate with erect, monosiphonic and Colony with erect, strongly ramified, pinnate unbranched stems up to 30 mm. Basal part com- stems, rigid in appearance, typically polysiphonic; posed of several segments with nematothecae, sep- branches of hydrocaulus opposite or nearly so; arated by means of transverse nodes. Remainder hydrocladia branched, regularly arranged, placed on main axis homomerously segmented by means of an apophysis with a much developed, large “mamel- oblique nodes, but at distal extreme, heteromerous- on” (considered as an atrophied hydrotheca) on its ly segmentation may occurs by additional trans- superior surface; hydrothecal rim smooth; verse nodes. Hydrocladia alternate, on lateral gonophores as fixed sporosacs, gonothecae with or apophyses besides hydrothecae; most basal hydro- without nematothecae. cladia sometimes branched; hydrocladia heteromer- Remarks: sometimes included in the Plumulari- ously segmented. Segments on main axis with one idae. hydrothecae and 7-8 nematothecae; one median References: Calder (1997); Schuchert (1997; inferior almost reaching hydrothecal base, two lat- 2001a)

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Polyplumaria flabellata G.O. Sars, 1874 Gonophores as fixed sporosacs, gonothecae single (Figs. 79H-L) with a few nematothecae on basal region. Remarks: sometimes included in the Plumulariidae. Hydrocauli erect, up to 350 mm, polysiphonic References: Calder (1997); Schuchert (1997). and branched, with some thick stolonal fibers basal- ly; branches arranged opposite o nearly so, usually Pseudoplumaria marocana (Billard, 1930) polysiphonic over part of their lengths. Tubes of (Figs. 79M-P) stem and branches with nematothecae. Main axis of branches segmented into internodes, bearing alter- Colonies with a thick, polysiphonic, much nate apophyses with a large mamelon and a pair of branched stem about to 220 mm high, rising from nematothecae; hydrocladia borne on the apophyses, thick matting of hydrorhizal fibers; branches oppo- segmented, first internode shorter and athecate, site, in one plane. Axial tubes with two longitudinal occasionally fused with the apophysis, remainder rows of small nematothecae; “main” frontal axis ones each with big hydrotheca and 4 nematothecae: with alternate apophyses bearing hydrocladia (2-6 one median inferior, two laterals, and one median per internode), each with one “mamelon” surround- superior which may occasionally be placed on a sep- ed by three nematothecae. Hydrocladia with 1-2 arate internode, nodes oblique. Hydrotheca cup- basal internodes with a single nematotheca, the shaped, walls gradually widening, margin slightly remainder ones with one hydrotheca and four nema- everted and even; adcauline wall 1/3 adnate. Lateral tothecae; nodes oblique (but the first transverse). nematothecae reaching hydrothecal rim or slightly Hydrotheca big, cylindrical, margin not everted and shorter, all nematothecae two-chambered, basal even. Median inferior nematotheca two-chambered, chamber longer and narrower, apical chamber cup- basal chamber very short and immobile, apical shaped and with deep adcauline embayment. The chamber with a deep adcauline embayment; lateral hydrocladia may be branched, the branch originat- nematothecae larger, reaching hydrothecal rim, ing from the first internode. Male and female movable, two-chambered, apical chamber with a gonothecae similar, borne on short pedicels near minor embayment; fourth nematotheca found in axil base of hydrocladium, inverted pear-shaped, between free part adcauline wall and internode, obliquely truncate above, aperture large; 4 small reduced to a peridermal sac; coenosarc of the colony nematothecae near base. with zooxanthellae; gonothecae pyriform with two Records from Mediterranean: only just inside the short basal segments. Mediterranean, at the Strait of Gibraltar. Records from Mediterranean: found only at the Known seasonality: 6, 7. entrance (Algeciras Bay, Strait of Gibraltar). Distribution: sub-tropical to cool-temperate Known seasonality: 6, 7. waters on the eastern Atlantic, Mediterranean. Distribution: tropical temperate eastern Atlantic, References: Gili, Vervoort and Pagès (1989); Mediterranean. Ramil and Vervoort (1992 a, c); Cornelius (1995); References: Patriti (1970); Gili, Vervoort and Medel and Vervoort (1995); Medel and Lopez- Pagès (1989) part of the material of Polyplumaria González (1996); Ansín Agís et al. (2001); flabellata; Ramil and Vervoort (1992c), Medel and Schuchert (2001a). Vervoort (1995); Medel and López-González (1996); Ansín Agís et al. (2001) Genus Pseudoplumaria Ramil and Vervoort (1992) Genus Schizotricha Allman, 1883 Colonies composed of rigid, strongly ramified, polysiphonic, occasionally forked hydrocaulus, with Colonies with polysiphonic, erect stem, which alternate or opposite branches; hydrocladia always may be branched or unbranched, with one main unbranched, alternately arranged along axis, placed axial tube bearing pinnately arranged hydrocladia on an apophysis with a much developed, large and hydrothecae, and several undivided accessory “mamelon” (considered as an atrophied hydrotheca) tubes provided only with nematothecae; hydrocladia on its superior surface; hydrotheca exclusively alternate, the majority branched sympodially from found on the hydrocladia, hydrothecal border anterior or lateral surface immediately below smooth; mobile, immobile and reduced nematothe- hydrothecae; hydrotheca cup-shaped, with smooth cae two-chambered (bithalamic) present. rim; nematotheca 2-chambered and movable, lateral

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nemathotecae not fused to their pedicel or to Medusa: umbrella flat; manubrium short and flat, hydrothecae; gonophores as fixed sporosacs, mouth with irregular lips; with marginal cordyli; gonothecae inserted on hydrocladia between with 4 or more branched radial canals; marginal ten- hydrothecae and provided with nematothecae. tacles hollow; “gonads” linear to sinuous on the References: Schuchert (1997); Peña Cantero et radial canals; with or without marginal cirri; with or al. (1999). without adaxial ocelli; without statocysts. Remarks: this family is usually included in the Schizotricha frutescens (Ellis and Solander, 1786) Lafoeidae A. Agassiz, 1865, but has often been sep- (Figs. 80A-E) arated as a subfamily by several authors (see Calder, 1991; Boero et al., 1997 for a review). The family Colonies composed of erect, polysiphonic and Hebellidae was established by Fraser (1912) to pinnate stems up to about 75 mm high, arising from accommodate the following genera (see Calder, flattened mass of hydrorhiza tubes. Hydrocladia 1991): Bedotella; Halisiphonia, Hebella, Hebellop- alternate, laterally under the hydrothecae. Sec- sis and Scandia, whose hydroids typically have ondary and tertiary hydrocladia sometimes present, stolonal colonies, campanulate hydrothecae with a arising from the first hydrothecae of the hydrocla- diaphragm or an annular thickening or both, and sin- dia. Primary tube of the stem with a longitudinal gle gonothecae. As stated by Calder (1991), in the row of hydrothecae. Hydrocladia segmented on long Lafoeidae, Filellum is stolonal, a diaphragm is pre- segments by transverse nodes, with 1-5 hydrothe- sent in Abietinella, Cryptolaria and Zygophylax, and cae, each one surrounded by 3 nematothecae, one single gonothecae are found in some species of median inferior and two laterals. Hydrotheca cup- Cryptolarella. We recognise what Calder (1991) shaped, deep, adcauline wall completely adnate, rim considered as a subfamily of the Lafoeidae, the smooth. Median inferior nematotheca some distance Hebellinae, as a separate family: the Hebellidae. In below hydrothecae; lateral nematotheca over reach- fact, although certain of the Hebellidae characters ing hydrothecal margin. Male and female gonothe- are shared with some Lafoeidae genera, none of cae on different colonies, borne on axis and hydro- them have all those characters together; Filellum is cladia below hydrothecae; pear-shaped, narrowed stolonal but has no diaphragm and has aggregated basally, with two nematothecae. gonothecae; some Cryptollarella have a single Records from Mediterranean: western Mediter- gonotheca, but they have no diaphragm and are ranean, Adriatic. erect; Abietinella, Cryptolaria and Zygophylax have Known seasonality: 2, 6, 7. a diaphragm but have erect colonies and coppinia. Reproduction: 6. Hebellid medusae, till recent years, were only Distribution: eastern temperate and subtropical known by juvenile indeterminable stages. De Atlantic, Mediterranean. Andrade and Migotto (1997) reared immature References: Millard (1975); Ramil and Vervoort medusae from a Hebella species, showing relation- (1992a); Boero and Bouillon (1993); Cornelius and ship with Laodiceidae, perhaps with the medusa- Ryland (1990); Avian et al. (1995); Cornelius based genus Staurodiscus, and Migotto and De (1995) as Polyplumaria; Medel and López- Andrade (2000) elucidated the life cycle of Hebella González (1996); Schuchert (1997, 2001a). furax which should be referred to genus Toxorchis, possibly to T. kellneri (Toxorchis is here considered as Family HEBELLIDAE Fraser, 1912 congeneric with Staurodiscus, see below). The Laodi- ceidae contain two distinct groups of medusa genera, Hydroid: colony stolonal, hydrotheca campanu- those with unbranched radial canals from which sev- late with smooth margin, short or long distinct pedi- eral life cycles are known, the hydroids being all cel; hydrothecal base with annular perisarcal thick- “Cuspidella-like”, and two genera with branched ening and membranous diaphragm or thick radial canals, whose life cycle were unknown till the diaphragm an no annular thickening; gonotheca observations of the above cited authors, and having solitary, with or without operculum, arising from Hebella hydroids. Those two particular genera are hydrorhiza; exceptionally with nematothecae here included in the family Hebellidae. The Lep- (Bedotella); gonophores as fixed sporosacs, or tomedusae contain so four families with cordyli or swimming gonophores, or eumedusoids, or free cordyli-like structure the Hebellidae, the Laodiceidae, medusae. the Teclaiidae and the Tiarannidae.

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References: Calder (1991); Migotto (1996); De Records from Mediterranean: eastern and west- Andrade and Migotto (1997); Boero et al. (1997); ern Mediterranean, Adriatic. Migotto and De Andrade (2000); Watson (2000). Known seasonality: present all the year. Reproduction: 1-12 Key to hydroids and medusae Distribution: warm waters around the world. References: Boero (1980); Gili (1986), Medel 1. Gonophores producing fixed sporosacs ...... 2 and López-González (1996), all as Hebella parasit- – Gonophores not producing fixed sporosacs; ica; Peña Cantero and García Carrascosa (2002). hydrothecae sharply separated from pedicel.... 3 2. Colony with nematophores and nematothecae.... Genus Bedotella Stechow, 1913 ...... Bedotella – Colony without nematophores ...... Scandia Colonies stolonal or erect, branched, polysiphon- 3. Gonophores as swimming sporosacs ...... ic; hydrothecae campanulate, borne irregularly on ...... Anthohebella all surface of branches and sometimes on – Gonophores not as above ...... 4 hydrorhiza, free, non adherent, distinctly pedicel- 4. With eumedusoids or immature medusae ...... late, with thin diaphragm; margin even and slightly ...... Hebella everted; nematophore in shortly globular peduncu- – With free mature medusae; some or all of the late nematotheca on hydrocaulus and hydrocladia; radial canals branched, branches joining or not gonophores as fixed sporosacs, gonothecae solitary, ring canal ...... Staurodiscus strongly compressed, disc-shaped, not aggregated. References: Ramil and Vervoort (1992a); Genus Anthohebella Boero, Bouillon and Kubota, Alvarez (1993b). 1997 Bedotella armata (Pictet and Bedot, 1900) Hydroid: colonies stolonal; hydrotheca on short (Figs. 80I-K) pedicel, campanulate, usually with thin annular thickening and thin membranous diaphragm; swim- Colonies stolonal or with erect stems (occasional- ming gonophores, with velum, 4 radial canals, 4 ly as a combination of both), up to 15 mm high. atentaculate marginal bulbs; “gonads” on spadix Stolonal colonies with creeping tubes or an anasto- (manubrium); gonotheca solitary originating from mosing, irregular network of stolonal tubes. Erect hydrorhiza. colonies composed of a number of adnate stolons Remarks: Watson (2000) described a new species basally attached by means of creeping stolons that of Anthohebella, A. darwinensis, but the gonophores may bear hydrothecae and nematothecae. Perisarc of this species are devoid of manubrium and no ref- thin and transparent over whole colony. Hydrotheca erence is made in the description to the position of campanulate, walls narrowing towards basally, occa- the gonads, although the gonophore is considered as sionally slightly asymmetric in lower third, rim circu- nearly mature. This species is here mantained in the lar and everted. Hydrothecal renovations common. Anthohebella awaiting more information. Hydrothecal pedicels with a few rings or undulations of perisarc, near insertion on stolon. Nematothecae Anthohebella parasitica (Ciamician, 1880) globular, with a short pedicel, arranged irregularly, (Figs. 80F-H) frequently in groups of 4-5 nematothecae. Gonothe- cae of a big size (6 x 6 mm), fan-shaped, compressed Colonies stolonal; hydrothecae on short and annulated laterally borne on short pedicels. pedicels, campanulate, margin curved, usually with Records from Mediterranean: western Mediter- annular thickening and a thin membranous ranean (France, only one record); also recorded at diaphragm; hydranth with conical hypostome; repro- the Strait of Gibraltar. duction by swimming gonophores, with velum, 4 radi- Distribution: Northeastern Atlantic, Mediter- al canals, 4 atentaculate marginal bulbs; “gonads” on ranean. spadix (manubrium), gonothecae nearly twice the References: Rees and White (1966); length of the hydrotheca, originating from hydrorhiza, Marinopoulus (1981) as Campanularia; Ramil and on short and annulated pedicels tapered basally, wide Vervoort (1992a); Altuna (1994); Medel and López- and truncated distally, with 4-5 operculars flaps. González (1996).

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Genus Hebella Allman, 1888 Genus Scandia Fraser, 1912 = Hebellopsis Hadzi, 1913 = Croatella Hadzi, 1916

Hydroid: colonies stolonal; hydrotheca on short Colonies stolonal, sometimes sympodial, arising pedicel, campanulate to cylindrical, usually with from a creeping hydrorhiza; hydrotheca large, cam- annular thickening and membranous or perisarc-like panulate, usually borne on long pedicels, with a diaphragm; gonophores either as released eumedu- basal rounded annular perisarcal thickening; soids with mature “gonads” on radial canals, or as gonophores fixed sporosacs, gonotheca solitary. medusa already mature at liberation with 4 radial Remarks: Scandia differs from Anthohebella and canals, each with a proximal gonad; 4 perradial Hebella in not being associated to supporting atentaculate bulbs and 4 small interradial atentacu- hydroids and in gonothecal content. It could be late bulbs; manubrium short; mouth and gastric cav- merged with Hebella. ity present; during life span some tentacles and more marginal bulbs may grow, or as juvenile immature 1. Female gonophore spherical...... S. gigas free medusa. – Female gonophore oval, more or less corrugated Medusa: adult medusa unknown...... S. michael-sarsi Remarks: the genus Hebella will probably have to be split in the future when more life cycles will be Scandia gigas (Pieper, 1828) completely described, several hebelliform hydroids (Figs. 81F-H) giving apparently rise to different medusa morpho- types. See also remarks under Scandia. Colonies composed of erect pedicels scarcely, References: Blanco et al. (1994); Altuna Prados dichotomously or irregularly branched and ended by (1996); Boero, Bouillon and Kubota (1997). hydrothecae. Perisarc of pedicels undulated or twist- ed throughout. Hydrothecae tubular, elongated, Hebella furax Millard, 1957: walls sometimes asymmetrical, narrowing gradually see below Staurodiscus towards the base, with a hydrothecal diaphragm; margin everted, rim even. Female gonothecae spher- Hebella scandens (Bale, 1888) ical, male sac-shaped and elongated. (Figs. 81A-E) Records from Mediterranean: eastern and west- ern Mediterranean, Adriatic. Hydroid: colonies epizootic on other hydroids; Known seasonality: 1, 4-6, 8, 9, 11. hydrothecae with flared margin, mostly oblique, Reproduction: 4-8. but bent 90° when growing over host hydrothecae, Distribution: temperate waters from western and with smooth to slightly corrugated walls, asym- eastern Atlantic and North Pacific, Mediterranean. metrical, with perisarcal diaphragm; pedicels References: Boero (1981); Gili (1982; 1986); short, smooth or annulated; hydranths with 12-16 Roca (1989); Boero and Bouillon (1993); Altuna tentacles; gonothecae containing up to 4 medusa (1994); Avian et al. (1995); Medel (1996); Medel buds, bigger than hydrothecae, asymmetrical, with and López González (1996); Peña Cantero and Gar- undulated walls, truncated distally, tapering cia Carrascosa (2002). toward base, on short pedicels, operculum with 4 opercular flaps. Scandia michaelsarsi (Leloup, 1935) Records from Mediterranean: eastern and west- (Figs. 81I-L) ern Mediterranean, Adriatic. Known seasonality: 1, 2, 4-7, 11, 12. Colonies with long, erect pedicels unbranched or Distribution: Atlantic; Indo-Pacific; Mediter- branched, ended by hydrothecae. Pedicels irregular- ranean. ly wrinkled or twisted perisarc. Hydrothecae tubu- References: Rossi (1961); Millard (1975); Gili lar, deep, walls slightly asymmetrical, rounded (1986); Roca (1986); Calder (1991) as Hebellopsis; basally, margin everted, aperture circular; base of Genzano and Zamponi (1992); Avian et al. (1995); the hydrotheca with a thick hydrothecal diaphragm; Medel and López-González (1996) as Hebellopsis; gonophores unknown, gonothecae borne on stolon, Boero et al. (1997); Peña Cantero and García Car- with short pedicels, ovalate; the female longer and rascosa (2002). more slender than the male, more or less corrugated,

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truncate, with the aperture occupying only a part of (obtained from Hebella furax), described a develop- the upper part. ment of the radial canals and of their branches similar Records from Mediterranean: western Mediter- to that observed in Staurodiscus. There are so present- ranean ly no reasonable reasons to separate the two genera. Seasonality: ? Distribution: Atlantic, Mediterranean. Staurodiscus kellneri Mayer, 1910 References: Fraser (1944) as Scandia mutabilis; (Figs. 82A-D) Vervoort (1959) as Hebella michael-sarsi; García- . Corrales et al. (1979); Boero and Bouillon (1993); Diagnosis: see above. Medel and López-González (1996); Boero et al. Records from Mediterranean: western Mediter- (1997). ranean. Seasonality: ? Genus Staurodiscus Haeckel 1879 Distribution: Indo-pacific, Mediterranean. = Toxorchis Haeckel, 1879 References: García Corrales et al. (1979); Gili (1982); Boero et al. (1997); De Andrade and Migot- Hydroid: colonies generally epizootic on other to (1997); Migotto and De Andrade (2000). hydroids, mainly plumulariids and aglaopheniids, Hebella-like; with the hydrorhiza sometimes pene- Family KIRCHENPAUERIIDAE Stechow, 1921a trating into the perisarc of the host as a parasitic form; hydrothecae almost conical when growing on Colonies either with erect, branched or upper part of the host, cylindrical when growing on unbranched hydrocaulus, monosiphonic or polysi- lower part of same host; asymmetrical to symmetri- phonic or stolonal (Ophinella); issued from a creep- cal; with everted margin, sharply or slightly oblique, ing hydrorhiza; hydrocladia alternate, arising in with short to long, wrinkled or annulated pedicels; polysiphonic hydrocauli from a single dominant with membranous diaphragm (sometimes absent) axial tube; hydrothecae small, occurring only on and annular thickening; hydranth with 20-26 tenta- hydrocladia, with or without marginal cusps, with or cles; gonophores as free medusae; gonotheca as big without an abcauline intrathecal septum, adnate or or slightly bigger than hydrotheca, with four oper- not; nematophores with nematothecae often rudi- cular flaps, on short pedicel, slightly undulated mentary or occurring as naked sarcostyles; when walls, truncated distally, tapering at base, containing present, nematothecae simple, typically one-cham- up to three medusae. bered although two-chambered in some taxa (i.e.: Medusa: with 4 or more main primary radial Naumovia, Ventromma), not fused to hydrothecae; canals, some or all branching one or more times, pri- paired lateral nematophores and nematothecae mary canal and some or all of the branches reaching absent; gonophores as fixed sporosacs; gonotheca circular canal; “gonads” on primary radial canals solitary, lacking nematothecae, on stem or hydrocla- and branches; numerous tentacles and cordyli; with dia, exceptionally on hydrorhiza (Pycnotheca). or without cirri; with or without ocelli. Remark: cnidome usually composed of microba- Remarks: the life cycle Hebella furax Millard, sic mastigophores and sometimes pseudostenoteles, 1957 has been elucidated by Migotto and De Andrade microbasic euryteles, and haplonemes. Stepanjants (2000); the hydroid giving rise to a Staurodiscus (Tox- et al. (1998) described, in some specimens of orchis) type of medusa, presumably Staurodiscus kell- Wimveria, desmoneme-like capsules from undis- neri Mayer, 1910. The differences between Staurodis- charged cnidocysts. The presence of desmonemes cus and Toxorchis are ambiguous and tenuous, the seems very doubtful in Leptomedusae and result main character being the supposed mode of ramifica- presumably of contamination by cnidocysts issued tion of the radial canals. In Staurodiscus, ramifications from other species. The family Kirchenpaueriidae are described as branches formed after the develop- needs critical revision, the genera being not clearly ment of the primary canal which first reach the circu- defined and their diagnoses often overlapping. The lar canal, whereas in Toxorchis ramifications were genera Naumovia, Ventromma and Wimveria present believed to be bifurcation of the primary canal which only slight differences with Kirchenpaueria and himself never reached the circular canal (see Kramp, could eventually be included in it. 1962; Bouillon, 1984b). Migotto and De Andrade References: Cornelius (1995); Migotto (1996); (2000), studying the cycle of a Toxorschis medusa Calder (1997); Stepanjants et al. (1998); Peña Can-

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tero and Marques (1999); Ansín Agís et al. (2000). two segmented; elongated, tapered basally, widely and truncate distally. 1. Nematophores with well developed Records from Mediterranean: Alborán Sea only. nematothecae...... Ventromma Known seasonality: 6. – Nematophores nude or with reduced Distribution: North Atlantic, Indo-Pacific, Indian nematothecae...... Kirchenpaueria Ocean; Alborán Sea. References: Vervoort (1966a); Millard (1975) Genus Kirchenpaueria Jickeli, 1883 both as Kirchenpaueria triangulata; Ramil and Ver- voort (1992a); Medel and López-González (1996); Stem unbranched, monosiphonic, with alternate, Ansín Agís et al.(2001); Schuchert (2001a). pinnate, unbranched hydrocladia, in simple forms arising directly from hydrorhiza; hydrotheca cup- Kirchenpaueria pinnata (Linnaeus, 1758) shaped, without intrathecal septum, with unthooted (Figs. 82I-L, 83A-B) rim, partially or completely adnate; no cauline hydrothecae; nematotheca typically 1-chambered and Colonies pinnate with erect, monosiphonic, and movable, mesial nematothecae present or absent, occasionally branched hydrocauli up to about 42 mm. sometimes poorly developed, reduced or even absent, Basal part of the axis with several internodes separat- nematophores with or without nematothecae present ed by transverse nodes; the remainder segmented on also on stem pending species; gonophores as fixed internodes bearing hydrocladia, these alternate, on sporosacs, gonotheca solitary, not annulated, often lateral apophyses at the upper part of the segment. with longitudinal ridges and spines. Apophysis with a naked nematophore on the upper Recent references: Cornelius (1995); Schuchert side; another one is disposed laterally on the axis, just (2001a). above the apophysis. Hydrocladia with a first shorter athecate internode, with transverse node basally and 1. Nematophores with club-shaped nematothecae .. oblique one distally (occasionally several of this ...... K. bonnevieae internode may occurs); remainder internodes thecate, – Nematophores nude (stem and above or in an irregular sequence of thecate and athecate hydrotheca) or with a minute frontal peridermal internodes separate by transverse nodes. Thecate shield (below hydrotheca) ...... K. pinnata internodes with one hydrotheca and two nematophores, one median inferior and another medi- Kirchenpaueria bonnevieae (Billard, 1906) an superior. Hydrotheca cup-shaped, walls gradually (Figs. 82E-H) diverging, adcauline wall almost entire adnate. Medi- an inferior nematophore with a minute frontal perid- Colonies pinnate with erect, monosiphonic and ermal shield; median superior behind hydrotheca unbranched hydrocauli up to about 45 mm. Basal completely nude. Gonothecae of both sexes similar, parts of the main axis unsegmented, with several borne on hydrorhiza or in a row on the axis; sac- nematothecae. Remainder parts composed of seg- shaped, with short pedicels, hexagonal in cross sec- ments separated by transverse nodes; each internode tion, with six longitudinal carinae bearing digitiform bearing a latero-distal apophysis, one “mamelon” on prolongations of widely varied development, even upper surface of apophysis and two nematothecae, absent in some gonothecae. one basally and another on upper surface of apoph- Records from Mediterranean: eastern and west- ysis; two additional nematothecae may occurs. ern Mediterranean, Adriatic. Hydrocladia borne on the apophyses at the upper Known seasonality: present all the year. part of segments; alternate, with hydrothecate Reproduction: 1-12. internodes separated by slightly oblique nodes; each Distribution: eastern Atlantic, Indo-Pacific, segment with one hydrotheca in lower half and two Mediterranean. median nematothecae, below and above hydrothe- References: García-Corrales et al. (1978); Boero cae. Hydrotheca cup-shaped; completely adnate, rim and Bouillon (1993); Cornelius (1995); Avian et al. smooth, aperture tilted upwards. All nematothecae (1995); Medel and Vervoort (1995); Medel and one-chambered and movable, club-shaped, nar- López-González (1996); Ansín Agís et al.(2001); rowed basally, with a circular aperture distally; Schuchert (2001a); Peña Cantero and García Carras- gonothecae borne on apophyses, on short pedicels cosa (2002).

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Genus Ventromma Stechow 1923 References: Gili and García-Rubíes (1985); Gili (1986); García-Corrales et al. (1978); Boero and Colonies erect, monosiphonic or polysiphonic, Bouillon (1993); Avian et al. (1995); Cornelius with branched or unbranched hydrocauli arising (1995); Medel and Vervoort (1995); Medel and from creeping hydrorhiza; hydocladia alternate, typ- López-González (1996); Peña Cantero and García ically unbranched; hydrothecae only on hydrocladia, Carrascosa (2002). cup-shaped, margin entire, without intrathecal sep- tum; nematophores usually with small, 2-chambered Family LAFOEIDAE A. Agassiz, 1865 nematothecae, hydrothecate internodes with a medi- an inferior and a median superior nematotheca, no Paedomorphic hydrozoa usually reduced to lateral nematophores and nematothecae; hydroid stage, hydroids colonial, either erect or nematophores or nematothecae also on stems; stolonal, arising from a creeping hydrohiza, gonophores as fixed sporosacs, gonotheca solitary, hydrothecae varying from tubular to campanulate in with transverse annulations. shape; radially or bilaterally symmetrical, usually Remark: Cornelius (1995) pointed out that this adherent more seldom pedicellate; margin entire; genus is not satisfactorily defined; this author operculum usually absent; with or without includes Ventromma Stechow, 1923d in the Subfam- diaphragm; without annular perisarcal thickening; ily Plumulariinae L. Agassiz, 1862, instead of in the hydranth with a conical hypostome surrounded by a subfamily Kirchenpaueriinae where most authors whorl of filifom tentacles; abcauline diverticulum include it and where it is even often regarded as con- present or absent; nematophores present or absent. generic with Kirchenpaueria Jickeli, 1883. Cnidome: where known microbasic mastigophores. When known, gonophores as fixed sporosacs; Ventromma halecioides (Alder, 1859) gonothecae aggregated into coppinia or scapus, (Figs. 83C-G) exceptionally solitary. References: Calder (1991); Ramil and Vervoort Colonies pinnate with erect, basally polysiphon- (1992a); Blanco et al. (1994); Cornelius (1975b, ic and often branched hydrocauli up to about 40 mm 1995); Hirohito (1995); Calder and Vervoort (1998). high. Monosiphonic parts of the axis separated into internodes by transverse nodes; each segment with a 1. Hydrotheca stalked...... 2 lateral apophysis distally bearing a nude – Hydrotheca not stalked, usually adherent ...... 3 nematophore; a cup-shaped nematotheca is borne 2. Hydrothecae in two longitudinal rows: with laterally on the segment, above the apophysis. diaphragm or reduced annulus; nematophores Hydrocladia borne on the apophysis, alternate, het- and nematothecae usually present ... Zygophylax eromerously segmented, nodes transverse; basal part – Hydrothecae irregularly on all sides; with no beginning with a short athecate internode. Thecate diaphragm or annular thickening; without segments with one hydrotheca and two nematothe- nematophores ...... Lafoea cae, one median superior and one median inferior at 3. Mature colonies stolonal: hydrothecae adherent some distance of the hydrothecae. Hydrotheca on to hydrorhiza...... Filellum distal half of internode, cup-shaped, almost com- – Mature colonies with erect, branching stem .... 4 pletely adnate, abcauline wall slightly convex, rim 4. Diaphragm present between hydrotheca and stem smooth and circular, aperture 80º with the axis. apophysis; nematophores and nematothecae Nematothecae two-chambered, small, basal cham- normally present...... Cryptolaria bers very short, distal one cup-shaped, with – Normally no diaphragm and no nematophores... adcauline embayment. Gonothecae borne on the ...... Acryptolaria axis, barrel-shaped, narrowed basally, truncate dis- tally, with a circular lid; walls with transverse and Genus Acryptolaria Norman, 1875 distinct ribs. Records from Mediterranean: eastern and west- Colonies normally erect, stolonal when young, ern Mediterranean, including Black Sea, Adriatic. more or less alternately branched; hydrocaulus and Known seasonality: 6-3. hydrocladia polysiphonic, with an axial tube over- Reproduction: 3, 6, 7, 9. grown by accessory tubes; all branches with two Distribution: cosmopolitan species. longitudinal rows of alternate hydrothecae, sessile,

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tubular, adnate to axial tube or immersed basally in Cryptolaria pectinata (Allman, 1888) accessory tubes, curving outwards and becoming (Figs. 84A-D) free distally; diaphragm absent; nematophores absent; gonophores as fixed sporosacs, gonothecae Colonies up to 40 mm high; hydrocauli erect, aggregated in coppinia with or without modified strongly polysiphonic and occasionally forked, hydrothecal tubes. basally with small disk of stolonal fibers as attach- Remark: Stepanjants (1979) described an opercu- ment to the substratum. Hydrocladia subalternate, lum in Acryptolaria operculata? also polysiphonic. Perisarc strong and thick, becom- ing thinner at the hydrothecae. Nodes absent. Acryptolaria conferta (Allman, 1877) Hydrothecae biserially arranged in one plane on (Figs. 83H-L) stem and hydrocladia, borne on small apophyses, tubular, narrowed basally and curved distally; about Colonies composed of erect, polysiphonic and 1/2 of the adcauline wall adnate to the internode, but branched stems bearing hydrocladia. Axis and most axillary hydrothecae often completely free from part of branches and hydrocladia, composed of axial tube; diaphragm thick and oblique; rim numerous tubes longitudinally arranged and anasto- smooth, circular and slightly everted, hydrothecal mosed with each other; monosiphonic parts with a renovations frequent. Nematothecae present on sympodial structure, axis straight to geniculate, frontal part of hydrothecal apophyses, deep tumbler- hydrothecae lateral, in the same plane and alternate; shaped, rounded basally, with or practically without tubular, basal part merging into the stolon, distal part a short pedicel, rim circular and not everted. Sec- free and curved outwards, rim even and circular, ondary tubules parallel to axis and hydrocladia and hydrothecal renovations frequent. Gonothecae in covering basal portion of hydrothecae, usually bear- coppiniae with several amphora-shaped gonothecae; ing many, irregularly distributed nematothecae. acrocyst present in female gonothecae. Gonophores, fixed sporosacs, gonothecae arranged Remark: Ramil and Vervoort (1992) created the in coppinia flask-shaped, firmly adpressed for about subspecies minor based in its minor size and the lack two-thirds of length and with slender, free neck pro- of intermediate specimens between the two forms. vided with one or two lateral openings and one or Records from Mediterranean: western Mediter- two curved distal horns; coppinia provided with ranean. branched nematothecae which project above the sur- Known seasonality: 4, 6, 9. face. The coppiniae are dioecious. Distribution: cosmopolitan. Records from Mediterranean: only recorded at References: Vervoort (1968); Patriti (1970); Mil- the Strait of Gibraltar lard (1975); Roca (1986, 1989); Templado et al. Distribution: deep waters of the Atlantic and (1986); Calder (1991); Ramil and Vervoort (1992a); Pacific Oceans, Strait of Gibraltar. Boero and Bouillon (1993); Medel and López- References: Ralph (1958); Millard (1975); Gili et González (1996); Schuchert (2001a). al. (1989); Ramil and Vervoort (1992a); Medel and López-González (1996). Genus Cryptolaria Busk, 1857 Genus Filellum Hincks, 1868 Colonies normally erect, pinnate, stolonal in young stages; main stem polysiphonic, occasionally Colonies stolonal, stolon filiform, creeping on forked; hydrocladia sub-alternate, all in one plan; substrate, usually over other hydroids, irregularly main axis with 2 or 4 longitudinal rows of sub-oppo- branched; hydrotheca sessile, tubular, arising singly site hydrothecae; hydrotheca sessile, tubular, with- from hydrorhiza, adnate basally, curving centrally out pedicel, directly on apophysis, adcauline wall and becoming free and bending upwards in varying adherent to hydrocladia for some distance at least in degrees distally; no diaphragm and operculum; no some part of colony, usually curved outwards, sepa- nematophores and nematothecae; gonophores as rated from apophysis by a distinct diaphragm; nema- fixed sporosacs, gonothecae either closely adpressed tophores and nematothecae present; gonophores as together, with lateral walls contiguous, touching each fixed sporosacs, gonothecae aggregated to form a other, or weakly aggregated, being isolated, not in coppinia. close contact; coppinia usually hermaphrodite, with Reference: Rees and Vervoort (1987). or without modified hydrothecal protective tubes.

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Reference: Peña Cantero et al. (1998). maphrodite coppiniae; coppinia with simple curved accessory tubes. 1. Coppinia with protective tubes ...... 2 Records from Mediterranean: eastern and west- – Coppinia without protective tubes ...... ern Mediterranean, Adriatic...... F. disaggregatum Known seasonality: 1, 3, 5-7, 9-12. 2. With minute corrugations over the upper surface Distribution: cosmopolitan. of the adnate part hydrotheca, coppinia with References: Millard (1975); Gili (1982, 1986); straight accesory tubes...... F. serratum García-Carrascosa et al. (1987); Cornelius and – Without such corrugation, adnate part of Ryland (1990); Boero and Bouillon (1993); Avian et hydrotheca smooth, coppinia with simple curved al. (1995); Cornelius (1995); Medel and López- accessory tubes...... F. serpens González (1996); Peña Cantero et al. (1998); Schuchert (2001a); Peña Cantero and García Carras- Filellum disaggregatum cosa (2002). Peña Cantero, García Carrascosa and Vervoort, 1998 (Figs. 84E-F) Filellum serratum (Clarke, 1879) (Figs. 84I-J) Colonies stolonal, consisting of filiform hydrorhizal stolons, giving rise to hydrotheca par- Colonies stolonal and irregularly branched, gen- allel to the stolons which, depending of substratum erally epizootic on other hydroids; hydrotheca ses- forms a more or less tight mesh. Hydrotheca tubu- sile, basal part merging into the stolon, adnate por- lar adnate to substratum for more than half their tion provided with numerous external transverse length, hydrothecal aperture circular; rim even and ridges, free part curving upwards from the stolon, smooth, slightly widening and everted at aperture. tubular, rim even, usually everted, several hydrothe- Perisarc of hydrotheca smooth, hydrothecal reno- cal renovations frequent; gonophores as fixed vations frequent. Coppinia with gonothecae irreg- sporosacs, gonothecae aggregated to form a cop- ularly arranged, not in close contact, pear-shaped, pinia firmly adpressed cylindrical, with terminal with long neck. Widest part of gonothecae adnate aperture and with straight accessory tubes. to substratum, some gonothecae with renovations Records from Mediterranean: western Mediter- of aperture. Protective tubes absent, defensive ranean. functions being carried out by normal hydroids Known seasonality: 4 - 7, 9, 10, 12. from which hydrothecae are situated near Distribution: cosmopolitan species. gonothecae. Planula continuing their development References: Millard (1975); García-Corrales et outside the gonotheca connected to it by means of al. (1979); Gili (1982, 1986); Roca (1986); Calder a filament. (1991); Boero and Bouillon (1993); Medel and Records from Mediterranean: western Mediter- López-González (1996); Peña Cantero et al. (1998); ranean, Chafarinas Islands. Schuchert (2001a); Peña Cantero and García Carras- Known seasonality: 8. cosa (2002). Distribution: endemic of Mediterranean Sea. References: Peña Cantero et al. (1998); Peña Genus Lafoea Lamouroux, 1821 Cantero and García Carrascosa (2002). Colonies occasionally stolonal but usually erect, Filellum serpens (Hassall, 1848) branched, with polysiphonic hydrocaulus, terminal (Figs. 84G-H) branches of hydrocaulus monosiphonic; hydrothe- cae irregularly arranged, tubular to deeply campan- Colonies stolonal, tortuous, irregularly branched, ulate; radially symmetrical but sometimes bent and generally epizootic on other hydroids; hydrothecae thus bilaterally symmetrical, usually free from stem tubular, at irregular intervals, sessile, basal part (1/4- or stolon, pedicel generally spirally twisted, some- 2/3) merging into the stolon, distal part curving times absent, not always well defined, diaphragm upwards from the stolon, adnate portion smooth; rim absent, hydrothecal base indistinctly separated from even, usually everted, several hydrothecal renova- pedicel by ring of small desmocytes; gonophores as tions frequent; hydranth with 8-12 amphicoronate fixed sporosacs, gonothecae aggregated in hermaph- tentacles, hypostome conical; gonothecae in her- rodite coppinia with modified tubes.

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Lafoea dumosa (Fleming, 1820) geniculate, without nodes, hydrothecal apophyses (Figs. 84K, 85A-D) alternate and in the same plane. Hydrotheca tubular, narrower basally, with a short peduncle, diaphragm Colonies stolonal, erect, or both in the same oblique, walls slightly asymmetric, rim even, slight- stolon. Stolonal colonies monosiphonic; erect ly everted; nematothecae inserting on hydrothecal colonies polysiphonic and irregularly branched, apophysis, one on each side of hydrotheca, tubular, composed of parallel tubes each bearing hydrothe- with a short and spherical pedicel, rim even and cae at irregular intervals. Hydrotheca tubular, elon- slightly everted; renovations frequent on hydrothe- gate, narrower basally, rim even; hydrothecal cae and nematothecae; hydrocladia alternate, arising pedicels, when present, usually twisted. Hydranth below hydrothecae, on apophyses; hydrothecae with approximatelly 20 tentacles, amphicoronate, arranged as in the main axis; secondary hydrocladia hypostome conical. Gonothecae in hermaphrodite may occurs; gonophores as fixed sporosacs, cop- coppiniae. pinia open, loose, composed of sessile globular Records from Mediterranean: western Mediter- gonothecae, each with an outwards and downwards ranean, Adriatic. curving neck with terminal orifices, rim strongly Known seasonality: 1, 5- 7, 9-11. everted; with numerous nematophorous ramules Distribution: nearly cosmopolitan. pointing in all directions, occasionally ended by a References: García-Corrales et al. (1979); Gili small hydrotheca. (1982, 1986); Roca (1986); Ramil and Vervoort Records from Mediterranean: western Mediter- (1992a); Boero and Bouillon (1993); Avian et al. ranean. (1995); Cornelius (1995); Medel and López- Seasonality: ? González (1996); Schuchert (2001a). Distribution: eastern Atlantic, Indian Ocean, Mediterranean. Genus Zygophylax Quelch, 1885 References: Patriti (1970); Templado et al. (1986); Rees and Vervoort (1987); Ramil and Ver- Colonies usually erect, pinnate or flabellate, voort (1992a); Boero and Bouillon (1993); Altuna rarely stolonal; stem occasionally forked, polysi- and Alvarez (1995); Medel and López-González phonic with the exception of distal parts; hydrocla- (1996); Medel (1996). dia in most species in one plane but sometimes in various planes; hydrothecae arising from stem, Zygophylax brownei Billard, 1924 branches and hydrocladia, alternately in two longi- (Figs. 85K-M) tudinal rows and from the axial tube when polysi- phonic, tubular to deep campanulate, never adher- Hydrocauli slightly polysiphonic basally, weakly ent, usually merging into a pedicel of various length, geniculate in monosiphonic regions, perisarc firm, with distinct diaphragm often reduced to mere annu- pinnate, with alternate apophyses supporting hydro- lus; abcauline caecum present (?); nematophores cladia, nodes absent; each apophysis with axial and nematothecae generally present on hydrothecal hydrotheca and a nematotheca; hydrocladium sepa- apophyses and on hydrocladial tubes; gonophores as rated from apophysis by distinct perisarcal constric- fixed sporosacs, gonothecae arranged in coppinia or tion. Hydrocladia with internodes bearing one to scapus. five alternate apophyses with hydrothecae, occa- Reference: Rees and Vervoort (1987). sional nodes; hydrothecae large, almost cylindrical but asymmetric, with adcauline wall usually more 1. Gonothecae with numerous nematophorous convex than abcauline, narrowing basally, ramules pointing in all directions.... Z. biarmata diaphragm concave but perpendicular, attached by – Gonotheca with no special accumulation of means of thickened perisarcal ring; rim circular, nematothecae...... Z. brownei slightly everted, renovations frequent; pedicel irreg- ularly wrinkled, occasionally kinked; nematothecae Zygophylax biarmata Billard, 1905 cup-shaped, cylindrical, rounded basally, with short (Figs. 85E-J) pedicels, rim circular, renovations frequent; gonophores as fixed sporosac, gonothecae quite sep- Hydrocauli erect and polysiphonic, imperfectly arated from another, not conjoined in a coppinia, but pinnate. Monosiphonic parts of the axis slightly clustered thickly round parts of stem, deep oval,

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with two aperture, not compressed, with no special simple, wavy along radial canals, sometimes accumulation of nematothecae. adjacent to manubrium ...... Laodicea Records from Mediterranean: western Mediter- ranean. Genus Guillea Bouillon, Pagès, Distribution: north-eastern Atlantic, Mediter- Gili, Palanques, Puig and Heussner, 2000 ranean. References: Rees and Vervoort (1987); Ramil Laodiceidae medusae with well developed manubr- and Vervoort (1992a); Medel and López-González ial perradial pouches; with complex «gonads» on prox- (1996); Boero et al., 1997; Schuchert (2001a). imal part of manubrium and in manubrial pouches, germ cells developing in manubrial pouches on numer- Family LAODICEIDAE Agassiz, 1862 ous lateral lamellar folds of the proximal part of the radial canals; with marginal cirri and ocelli. Hydroid: of “Cuspidella” type; colony stolonal; hydrotheca tubular, sessile, often with transversal Guillea canyonincolae Bouillon, Pagès, Gili, growth-rings, sometimes with basal constriction at Palanques, Puig and Heussner 2000 origin, or exceptionally a poorly delimited pedicel (Figs. 85N-P) (Ptychogena); operculum conical comprising sever- al pleated flaps meeting centrally, with visible Medusa: umbrella higher than a hemisphere, crease-line basally; hydranth lacking intertentacular dome-shaped, 4.5 mm wide, 4.0 mm high; with ver- web, with amphicoronate tentacles; gonotheca tical walls and flatten, rounded apex, mesoglea uni- resembling hydrotheca, but larger. formly thick; velum narrow; manubrium quadrangu- Medusa: with marginal cordyli with or without lar, short, with four perradial gastric, gonadial cnidocysts; with 4 or 8, simple radial canals; mar- pouches; mouth large, almost circular, without dis- ginal tentacles hollow; “gonads” on radial canals, on tinct lips but with margin swollen, faintly folded; radial canals and lobes of manubrium or into four simple narrow radial canals penetrating manubrial pouches; with or without marginal cirri; manubrium above gonadial pouches and not meet- with or without adaxial ocelli; without statocysts. ing exactly in the centre of manubrial roof; circular References: Russell (1963a) ; Bouillon et al. canal narrow; «gonads» developing perradially on (1991); Pagès et al. (1992); Bouillon (1999); Bouil- dorsal proximal part of manubrium and extending lon and Barnett (1999); Bouillon and Boero (2000). into the gastric pouches, germ cells differentiating along numerous lateral lamellar folds issued from Key to hydroids and perpendicular to the proximal parts of the radial canals included in the pouches, folds gradually When known, the hydroids have a “Cuspidella tapering in centripetal direction towards dorsal parts facies” (see family characters); indistinguishable of the manubrium; up to 24 marginal tentacles with from each other and inadequate for diagnosis. coiled extremity; marginal bulbs broad, rounded; one club-shaped cordyli without cnidocysts and one Key to medusae to two spiral cirri between successive tentacles; one ocelli on adaxial side of each marginal bulb. 1 Radial canals open grooves forming large Hydroid: unknown. cruciform mouth...... Staurophora Records from Mediterranean: western Mediter- – Radial canals closed ...... 2 ranean. 2. With four radial canals simple or with short Known seasonality: 12. lateral diverticula...... 3 Distribution: endemic of Mediterranean Sea. – With 8 simple radial canals ...... Melicertissa References: Bouillon et al. (2000). 3 With well developed manubrial perradial pouches; «gonads» on proximal part of Genus Laodicea Lesson, 1843 manubrium and in manubrium pouches, germ cells developing on numerous lateral lamellar Hydroid:“Cuspidella” type, see family charac- folds of the proximal part of the radial canals ters; hydrotheca sessile. included in the pouches...... Guillea Medusa: with small manubrium, sometimes with – Without marginal perradial pouches; «gonads» small perradial lobes; with four radial canals, simple

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or with short lateral diverticula; with simple wavy diaphragm; hypostome tall, conical; with a single “gonads”; with or without marginal cirri; with or whorl of 10-12 filiform, amphicoronate tentacle, no without adaxial ocelli. intertentacular membranous web; gonothecae as Reference: Bouillon et al. (1991). hydrothecae but twice as long, including several Numerous non-valid species of Laodicea have developing medusae at different stages. been described from Mediterranean. See Kramp Medusa: umbrella up to 37 mm wide, slightly (1959a, 1961); Boero and Bouillon (1993). flatter than a hemisphere, saucer-shaped; mannerism - Laodicea bigelowi Neppi and Stiasny, 1912 = short, with square base and short per radial lobes; Laodicea undulata (Forbes and Goodsir, 1851). mouth with short, slightly folded, crenulated, - Laodicea neptuna Mayer 1900 = doubtful recurred lips; 4 simple radial canals, circular canal species. narrow; «gonads» elongated, with sinuated pendent - Laodicea ocellata Babnik (1948) = doubtful folds, issuing from corners of manubrium along per- species. radial lobes and half part of radial canals or almost to umbrella margin, «gonads» may be developed 1. «Gonads» in short, complexly folded lateral even in small specimens and, the same individual diverticula of the proximal half of radial canals, may present more than one sexual cycle; up to 400- tentacles without abaxial basal spurs; no 600 hollow marginal tentacles with faintly devel- marginal cirri ...... L. fijiana oped basal bulbs, small abaxial spurs on young mar- – «Gonads» sinuous on radial canals contiguous ginal tentacles, often absent in adults ones; 1-2 spi- with manubrium; tentacles with abaxial basal ral cirri present (often lost by preservation) usually spurs; with marginal cirri...... L. undulata 1 cordyli between tentacles or rudimentary bulbs; ocelli present each third or fifth tentacle, on each Laodicea fijiana Agassiz and Mayer, 1899 tentacle when juvenile. (non Maas, 1905, 1906) (Fig. 86A) Remarks: L. undulata is very similar to L. indica, differing only by quantitative characters such as the Medusa: umbrella 6 mm high and wide; manubri- number of ocelli and tentacles, several authors um quadrate, 1/4 height of umbrella cavity; «gonads» regard them as conspecific. upon short complex lateral diverticula in proximal Records from Mediterranean: eastern and west- half of radial canals; about 70 marginal tentacles ern Mediterranean, Black Sea; Adriatic Sea. without basal spurs, very few cordyli, no cirri. Known seasonality: 1-12. Kramp (1953, 1961) retains this species only for Distribution: Atlantic, Indo-Pacific?, Mediterranean. the specimens of Fiji Islands? The L. fijiana described References: Russell (1936, 1953); Goy (1973b); from other localities are synonym of L. indica which Schmidt and Benovic (1979); Bouillon (1984b, a possibly synonym of L. undulata, see below. 1985a); Benovic and Bender (1987); Gili (1986); Records from Mediterranean: eastern Mediter- Brinckmann-Voss (1987); Goy et al. (1988, 1990, ranean. 1991); Bouillon, Boero and Fraschetti (1991); Ramil Known seasonality: 11. and Vervoort (1992a); Boero and Bouillon (1993); Distribution: Indo-Pacific (Fiji Islands?); Cornelius (1995); Avian et al. (1995); Benovic and Mediterranean. Lucic (1996); Medel and López-González (1996); References: Kramp (1961); Schmidt (1973). Mills et al. (1996). Hydroid: unknown. Genus Melicertissa Haeckel, 1879 Laodicea undulata (Forbes and Goodsir, 1851) (Figs. 86B-G) Laodiceidae medusa with 8 simple radial canals; with adaxial ocelli; with or without cirri. Hydroid: colonies of “Cuspidella type”, forming Hydroid: unknown. a creeping hydrorhiza from which arise single, ses- sile, cylindrical hydrothecae; terminal operculum Melicertissa adriatica Neppi, 1915 pyramidal bearing 8-10 teeth meeting centrally, (no figure known) sharply demarcated from the hydrothecae margin; old hydrothecae with transverse growth rings; Medusa: umbrella 46 mm wide, flatter than a hydranth long, very extensile, based on a delicate hemisphere, with fairly thick mesoglea; manubrium

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short, bell-shaped; mouth with 8 short crenulated canals, more developed in middle region of each lips; «gonads» linear, along whole length of radial canal; numerous hollow, short, marginal tentacles canals; 8 perradial marginal tentacles and between (up to several thousand), with elongate conical mar- them 16 other marginal tentacles all alike; 3-5 ginal bulbs and well developed pointed endodermal cordyli between successive tentacles each with a roots; tentacles approximately alternating with black ocelli and even more marginal cirri. cordyli and each with adaxial ocelli. Remarks: Picard, in Kramp (1961) page 444, Records from Mediterranean: medusa never found refers doubtfully this species to Octogonade mediter- in Mediterranean but doubtful records of the polypoid ranea Zoja, 1896, a Tiaropsidae with compound stage from south and eastern Spanish coast. sense organs, with different marginal tentacular struc- Seasonality: ? tures and, without cordyli (See Tiaropsidae). Distribution: Arctic (circumpolar); Indo-Pacific Records from Mediterranean: Adriatic Sea. (N. Japan, Alaska, bipolar); Atlantic; Mediter- Known seasonality: 3-4. ranean?. Distribution: endemic of Mediterranean Sea. References: Naumov (1951,1960-1969); Kramp References: Neppi (1915); Kramp (1959a, 1961); (1961); García-Carrascosa (1981)?; García-Carras- Boero and Bouillon (1993); Avian et al. (1995); cosa et al. (1987)? ; Boero and Bouillon (1993); Cor- Benovic and Lucic (1996). nelius (1995); Medel and López-González (1996).

Genus Staurophora Brandt, 1834 Family LOVENELLIDAE Russell, 1953

Hydroid: a typical cuspedellid, hydrotheca ses- Hydroid: colony stolonal or erect, sympodial; sile; gonothecae unknown. hydrotheca pedicellate, elongate, everted-conical Medusa: Laodiceidae with unusual cross-shaped to bell-shaped, with diaphragm; operculum coni- manubrium; mouth openings extending along the 4 cal, formed either by many triangular plates on radial canals transformed for a long distance into embayments in shallowly cusped hydrothecal mar- open grooves, only most distal parts remaining free gin and well demarcated from hydrothecal wall by and closed; mouth arms slit-like, with strongly fold- noticeable crease line, or by a folded continuation ed lips; «gonads» on diverticula in lateral walls of of the hydrothecal wall, lacking hinge-like base; cruciform, enlarged, mouth-radial canal complex; hydrothecae may renovate, but often collapsing, without cirri; with adaxial ocelli. disintegrating in old specimens, just a crumpled collar-shaped sheath remaining around hydranth Staurophora mertensii Brandt, 1834 base; hydranth with endodermal epithelium differ- (Figs. 86H-L) entiated into distinct parts, upper one digestive, basal one formed by chordal cells; with or without Hydroid: colonies typically «cuspidellid», forming intertentacular web; gonophores as free medusae, a reptant hydrorhiza from which arise at irregular gonothecae pedunculate. intervals, wide, unstalked, cylindrical hydrothecae; Medusa: manubrium short; no gastric peduncle; operculum pyramidal formed of 10-12 triangular flaps no excretory pores; 4 simple radial canals; margin- meeting centrally, sharply demarcated from hydrothe- al tentacles hollow, with lateral cirri; no marginal cal margin; hydranths extensile, with a conical-round- cirri; “gonads” on radial canals, not reaching ed hypostome, with up to 12 tentacles; no intertentac- manubrium; without or with 8 (exceptionally 4 or ular membranous web; gonothecae not known. 12) or indefinite number of statocysts, 16 or more Medusa: umbrella 100-300 mm wide, flatter than when adult; no ocelli. hemispherical; mesoglea thick and smooth; exum- Remarks: the family Lovenellidae was created by brella with numerous short centripetal furrows; Russell (1953) for Leptomedusae with lateral cirri, 4 manubrium, mouth and radial canals combined to radial canals, no marginal cirri, peduncle and excreto- form a large perradial cross reaching nearly umbrel- ry pores, Lovenella-like hydroids with a well demar- la, mouth openings extending along the 4 radial cated operculum and hydrothecal margin embay- canals transformed for a long distance into open ments. Russell (1953) distinguished Lovenella, with grooves, only most distal parts remaining free and an indefinite number of statocysts, from Eucheilota closed; mouth arms slit-like, with strongly folded with usually 8 statocysts. Kramp (1959a) adopted lips; «gonads» on diverticulae of the four radial these views and later (Kramp, 1959b; 1961; 1968)

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added the genus Cirrholovenia with marginal cirri, so by “campanulinid polyps” with an operculum well or modifying Russell’s original definition. Calder (1971, not well demarcated from the hydrotheca, with 1975) observed that the hydroid of Lovenella gracilis hydrothecae having or not marginal embayments, or lacks the opercular embayments that should be typical reduced to a basal collar; usually with an intertentacu- of the genus Lovenella, having an operculum in con- lar web; cnidome generally with merotrichous hap- tinuation with the hydrotheca. He consequently resur- lonemes. The family Cirrholoveniidae, with marginal rected the genus Dipleuron for this species (Calder, cirri and “cuspedelliid” type of hydroids, is kept as 1991). Bouillon (1985a), considering the impossibili- valid. Two genera, Hydranthea with free eumedusoids ty to integrate the diagnostic characters of the polyps and Campalecium with newly released medusae of and medusae, separated Kramp’s Lovenellidae in Eucheilota type are here tentatively included in the three families: the Cirrholoveniidae with medusae Lovenellidae. They were formerly considered as with marginal cirri and “cuspidellid” hydroids; the Haleciidae due to the collar shape of their hydrothe- Eucheilotidae with medusae with lateral cirri, 8 stato- cae; in our opinion they are campanulinid hydroids cysts and ”campanulinid” hydroids with a well demar- with reduced thecae similar to reduced stages of cated operculum but without hydrothecal embay- Lovenellidae, but might well represent the basal state ments; and the Lovenellidae with lateral cirri, an from which paedomorphic species with fixed indefinite number of statocysts and a “Lovenella” type gonophores and reduced hydrotheca originated the of hydroid, with a well demarcated opeculum with Haleciidae. embayments of hydrothecal margin. The study of “ References: Russell (1963b); Pagès et al. (1992); Lovenellidae” life cycles, however, shows that if the Bouillon (1999); Bouillon and Barnett (1999); medusae of these family present clear diagnostic char- Bouillon and Boero (2000); Schuchert (2001a, acters, their hydroids are puzzling, all belong to a 2003). “campanulinid” type but their opercular structures present differences even within the same genus. It is Key to hydroids thus hopeless to refer with confidence one or another type of opercular structure to a family-group taxon, 1. Hydroid of “Campanulina” facies ...... 2 particularly to a medusa-based family. After Kramp – Hydroid with reduced hydrotheca, of “haleciid” (1919, 1932b), too a great importance has been given facies...... 3 to the opercular structures of the Campanulinida. 2. Hydranth with intertentacular web ... Eucheilota Opercula can be different within the same family (see, – Hydranth without intertentacular web...... for instance, the Tiaropsidae and the Lineolariidae) or ...... Lovenella even within the same genus: in Phialella, for instance, 3. Gonophores producing eumedusoids; some species have opercular flaps demarcated from gonothecae on hydrorhiza, reduced or absent..... hydrothecae and other do not (Boero, 1987), and even ...... Hydranthea different hydrothecae on the same hydrocaulus may – Gonophores producing free medusae; present the two opercular types. Opercular structure, gonothecae growing from pedicel just under thus, is evidently inconstant and cannot be used to dis- hydrothecae ...... Campalecium tinguish families or even genera. The more, in many campanulinids the operculum can completely disap- Key to medusae pear, with the apical part of the hydrotheca, during normal colony growth, as shown by Werner (1968 a 1. With usually no more than 8 statocysts ...... and b) in Eucheilota maculata and Eutonina indicans ...... Eucheilota or can even be absent in some species of a normally – With an indefinite number of statocysts (16-32) operculate genus (many Eirenidae), only a little more ...... Lovenella than a collar remaining at the base of the hydrothecae of fully developed hydranths, looking like a haleciid Genus Campalecium Torrey, 1902 theca (see for instance Werner, 1968, fig.14 and Fig. 87: Figs. 8 to 13). The family Eucheilotidae is conse- Hydroid: colony typically stolonal, pedicel of var- quently considered as synonym of the Lovenellidae ied length bearing terminal hydranth, often secondary and the genera Eucheilota and Lovenella are again pedicels forming sympodial branches; hydrotheca included in the Lovenellidae, being defined as above collar-shaped, shallow, often regenerated, with a dis- for the medusa stage, the hydroid being characterised tinct diaphragm, large desmocytes; hydranth relative-

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ly large, elongated, cylindrical, not retractable into Remarks: The systematic position of these two hydrotheca; up to 30 amphicoronate tentacles; with or species is discussed under Lovenella cirrata. without intertentacular web endodermal epithelium differentiated into distinct part the upper digestive, Genus Eucheilota McCrady, 1859 the basal part formed by chordal cells; gonophores giving rise to free medusae; gonothecae clavate or Hydroid: colony of “campanulinid” type; rounded arising beneath hydrothecal pedicel, each hydrotheca with diaphragm, often reduced to a col- with several medusa buds. lar shaped sheath around base of adult hydranths, Medusa: only medusa buds or juvenile medusae operculum well developed, not demarcated; of Eucheilota type presently known, pending the hydranth with intertentacular web; gonotheca long, species. pedicellate on erect stems, with one to five medusa References: Watson (1993); Bouillon and Boero buds. (2000); Boero, unpublished observations. Medusa: with usually 8 statocysts. References: Ramil (1988); Cornelius (1995); 1. Cnidome with merotrichous haplonemes...... Bouillon and Boero (2000)...... C. medusiferum Remarks: the polyp of the species Campomma – Cnidome microbasic mastigophores ...... hincksii (Hartlaub, 1897) has been considered by ...... C. cirratum Cornelius (1995) as synonymous of Eucheilota maculata. If it is so, Eucheilota maculata would be ? Campalecium cirratum “Millard and Bouillon present in the Mediterranean, recorded under the (1975)”; not Haeckel, 1879 (Figs. 87A-B) name of Campomma hincksii. However, the hydroids of most Campanuliniidae are very similar, Hydroid: as for genus, cnidome microbasic the medusa being necessary to identify the species; mastigophores. as the medusa has not been found in the Mediter- Medusa: only medusa buds known from ranean, we consider the following records Mediter- gonothecae, with four perradial marginal bulbs of ranean of “Eucheilota maculata” hydroids as doubt- which two bear tentacles, with lateral cirri, without ful: Gili (1982, 1984); Gili and Castelló (1985) all as marginal warts, with eight statocysts. Campanulina; Medel and López-González (1996) Records from Mediterranean: ? as Campomma. Distribution: Indo-Pacific; Mediterranean? Seasonality: ? Key to medusa References: Millard and Bouillon (1975); Calder (1991); Altuna Prado, 1993b. 1. With medusa buds on radial canals; with 4 marginal tentacles and 4 or more rudimentary Campalecium medusiferum Torrey, 1902 bulbs, all with 1-3 pairs of lateral cirri; 8 (Figs. 87C-E) statocysts...... E. paradoxica – Without medusa buds on radial canals...... 2 Hydroid: As for genus, cnidome with merotric- 2. With 16 marginal tentacles an 16 rudimentary hous haplonemes bulbs all with one pair of lateral cirri; about 24 Medusa: Only young medusae known with four small knobs without cirri; 8 statocysts...... perradial marginal tentacles, four perradial marginal ...... E. ventricularis bulbs and eight statocysts, without lateral cirri and – With 4 marginal tentacles with one pair of marginal warts. lateral cirri and a number of rudimentary bulbs, Records from Mediterranean: eastern and west- some of which have cirri; 8 statocysts; immature ern Mediterranean, Adriatic. medusae...... E. maasi Known seasonality: 5-9, 11, 12. Distribution: Atlantic, eastern Pacific, Mediter- Eucheilota maasi Neppi and Stiasny, 1911 ranean. (Fig. 87F) References: Motz-Kossowska (1911); Huvé (1954); Boero (1981); Gili (1986); Boero and Sara Medusa: only young medusa known. Umbrella (1987); Calder (1991); Altuna Prado (1993b) Avian 3-5 mm wide, 3 mm high, mesoglea thick; manubri- et al. (1995). um cylindrical, half as long as umbrella cavity;

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small, immature, «gonads» on middle part of radial Known seasonality: 2-12. canals; 4 marginal tentacles with rounded bulbs with Distribution: Atlantic; Indo-Pacific; Mediter- one pair of lateral cirri, a number of rudimentary ranean. bulbs, some of which flanked by cirri; 8 statocysts. References: Kramp (1959b, 1961); Uchida and Hydroid: unknown. Sugiura (1975); Schmidt and Benovic (1977); Records from Mediterranean: Adriatic Sea. Bouillon (1984 a, b; 1995b); Castelló i Tortella Known seasonality: 4, 7, 9, 10, 12. (1986); Bouillon et al. (1988b); Dallot et al. (1988); Distribution: endemic of Mediterranean Sea. Carré and Carré (1990); Goy et al. (1988, 1990, References: Neppi and Stiasny (1913); Kramp 1991); Boero and Bouillon (1993). (1961); Boero and Bouillon (1993); Avian et al. (1995); Benovic and Lucic (1996). Eucheilota ventricularis McCrady, 1959 (Fig. 88A) Eucheilota maculata Hartlaub, 1894 (Figs. 87G-L) Medusa: umbrella 10 mm wide, hemispherical; manubrium short; mouth with four prominent lips; Hydroid: see genus definition. Hydroid doubtful- «gonads» linear, along middle 1/3 or 2/3 of radial ly reported from Mediterranean and Adriatic Seas. canals; 16 marginal tentacles and 16 rudimentary Medusa never collected in Mediterranean Sea bulbs all with one pair of lateral cirri and about 24 minute knobs without cirri; 8 statocysts. Eucheilota paradoxica Mayer, 1900 Hydroid: unknown. (Fig. 87M) Records from Mediterranean: eastern Mediter- ranean. Hydroid: not known from field. Carré and Carré Known seasonality: 1-5, 12. (1990) obtained in culture hydranths differentiat- Distribution: Atlantic; Indo-Pacific, Mediter- ing from medusae maintained during two months ranean. at 15°C. The hydroids developed on the radial References: Kramp (1959b, 1961); Bouillon, canal at the position usually occupied by the 1984b; Lakkis and Zeidane (1985)); Goy et al., gonads. Those hydranths were able to capture 1988, 1990, 1991; Boero and Bouillon (1993). preys and to feed but medusae reduction occurred gradually and finally the medusae were reduced to Genus Hydranthea Hincks, 1868 a mass constituting the base of the polyps. Follow- ing Carré and Carré those polyps are very similar Hydroid: colonies stolonal, hydrotheca short, to those described for Eucheilota maculata by collar-shaped, shortly pedicellate; hydranth elongat- Werner (1968a), unfortunately the authors never ed, large, with intertentacular web with merotric- could induce their settlement. hous haploneme cnidocysts; gonophores as eumedu- Medusa: umbrella 5 mm wide, higher than a soid, only short-lived male free eumedusoids hemisphere, sometimes with a slight apical projec- known; without tentacles; with four radial canals; tion, mesoglea moderately thick; manubrium small, “gonads” on radial canals, 8 statocysts; gonothecae flask-shaped; mouth with 4 simple lips; 4 narrow reduced or absent; when present, attached to radial canals and narrow circular canal; «gonads» hydrorhiza. along middle portion of radial canals; with 4 hollow References: Cornelius (1995); Bouillon and marginal tentacles with large bulbs, and 4 or more Boero (2000). rudimentary bulbs; all bulbs with 1-3 pairs of later- al cirri of unequal size; with 8 marginal statocysts; Hydranthea margarica (Hincks, 1862) active medusa budding on radial canals in non sex- (Figs. 88B-D) ual mature specimens, the daughter medusae begin to develop medusa buds before they become free; Hydroid: colonies stolonal bearing single frustules and hydranths developing on radial canals hydranths at irregular intervals, stolon with haustor- at the position usually occupied by the «gonads» ial projections beneath providing additional attach- under certain environmental conditions. ment; hydrothecae very short, collar-shaped with Records from Mediterranean: eastern and west- slightly divergent walls and basal diaphragm, on ern Mediterranean smooth short pedicels inserted directly to stolon;

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hydranth very elongated, slender, not retractable in Records from Mediterranean: western Mediter- hydrothecae, widest just below tentacles base and ranean, Adriatic. tapering gradually to base, with a cone-shaped Known seasonality: not found in nature, only hypostome, with 20-30 amphicoronate webbed ten- known from laboratory rearing. tacles; endodermal epithelium differentiated into Distribution: endemic of Mediterranean Sea. distinct part the upper digestive, the basal part References: Hadzi (1914) as Georginella formed by chordal cells; gonothecae short or absent, diaphana; Huvé (1954); Boero and Sara (1987); when present a shallow dish on a short pedicel; Boero and Bouillon (1993); Avian et al. (1995). gonophore a single eumedusoid; merotrichous hap- lonemes scattered or in clumps through tissues of Genus Lovenella Hincks, 1868 hydranth, stolon and particularly conspicuous on = Mitrocomium Haeckel, 1879 tentacular web, developing eggs reported in hydrorhiza of colonies lacking gonophores. Hydroid: colony “Campanulina” type; stolonal or Medusa: released eumedusoids almost spherical, upright and sympodial; hydrotheca pedicellate, elon- about 0.5 mm in diameter, surrounded by a thin gate, everted-conical to bell-shaped; operculum coni- perisarc, with four branched radial canals filled with cal, formed either by many triangular Figs. with purplish or orange granules as well as ring canal; embayments of the hydrothecal margin and well with eight statocysts; «gonads» on manubrium fill- demarcated from hydrothecal wall by noticeable ing the whole subumbrella, numerous cnidocyst on crease line, or formed by a folded continuation of the exumbrella. hydrothecal wall, lacking hinge-like base; diaphragm Records from Mediterranean: eastern and west- present; no intertentacular web; no nematophores. ern Mediterranean, Adriatic. Medusa: with an indefinite number of statocysts. Known seasonality: 5-8, 10, 11. Remark: all Lovenella-like hydroids with Reproduction: 8, 10. unknown cycle must be included in the Campan- Distribution: Atlantic, Indo-Pacific (Seychelles), ulinidae incertae sedis. Mediterranean. References: Hincks (1868); Huvé (1954); Millard Key of the medusae and Bouillon (1973); Cornelius (1975b, 1995); Gili (1986); Boero and Sara (1987); Boero and Bouillon 1. 8-16 marginal tentacles, each with 3-4 pairs of (1993); Avian et al. (1995); Peña Cantero and Gar- lateral cirri; several marginal warts without cirri cía Carrascosa (2002)...... L. cirrata Remarks: the presence of only eight statocysts in – With more than 16 marginal tentacles, with no the eumedusoid could indicate some relationship of marginal warts ...... 2 this genus with the genus Eucheilota. 2. With 16-24 marginal tentacles, each with 1-3 pairs of lateral cirri; «gonads» oval, longitudinal- Hydranthea incertae sedis ly divided, very close to circular canal ...... L. clausa Hydranthea aloysii (Zoja, 1893) – With 21 marginal tentacles, each with one pair of lateral cirri; «gonads» oval, midway of radial Colony reptant, stolon bearing single hydranths canals length ...... L. gracilis at irregular intervals. Hydranth up to 4mm in height, on a slightly ringed pedicel, with 12-18 amphicoro- Remarks: included here there is information on nate tentacles linked by an intertentacular web. Lovenella chiquita Millard, 1957 whose juvenile Hydrotheca very short, delicate, with a thin medusae are known from South Africa and the diaphragm. Large cnidocysts kidney-shaped up to polyps described doubtfully from the Spanish coasts 15 x 5.0 µm occuring throughout stolon, hydranth (see below). tissues and in tentacular web, small cnidocysts 9-10 x 2.5 µm scattered throughout entire colony. Lovenella chiquita Millard, 1957 Gonophores unknown. (Figs. 88E-H) Remark: this species is insufficiently described, its reproduction is unknown it could be any haliciid Hydroid: hydrorhiza creeping, often epizootic on or lovenelliid, perhahs a juvenile of H. margarica. other hydroids giving rise to short erected stems bear-

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ing a terminal hydranth or branched sympodially up to Medusa: umbrella 16 mm wide, almost hemi- 9 times each limb terminating in a hydrothecae, stems spherical; manubrium short, urn-shaped; 4 simple annulated throughout; hydrothecae deep- campanulate, lips; 4 sausage-shaped «gonads» on distal half of smooth, margin with 8-10 shallow bays; operculum of radial canals; 8-16 marginal tentacles with conspic- 8-10 converging segments with a gap between their uous basal bulbs, each flanked by 3-7 pairs of later- central points; diaphragm delicate; hydranth with over al spiral cirri; usually with 3-5 rudimentary margin- 12 tentacles; gonothecae arising from hydrorhiza on al warts between successive tentacles; about 16 sta- short annulated pedicels, smooth elongated, tapering tocysts. below truncated above, containing two medusa. Records from Mediterranean: eastern and west- Medusa: only newly liberated medusae of this ern Mediterranean, Adriatic. species are known. Umbrella 0.4 mm wide, 0.3 mm Known seasonality: 4, 6, 10. high, mesoglea thin; manubrium short; mouth quad- Distribution: Atlantic (Brazil, W. Africa); Indo- rangular simple; «gonads» not yet developed; with- Pacific (Malayan Archipelago, Bismarck Sea); out lateral cirri or marginal warts; 8 marginal tenta- Mediterranean. cles; 8 statocysts. References: Kramp (1959a, 1961); Brinckmann Records from Mediterranean: western Mediter- (1959a); Millard and Bouillon (1975); Boero ranean, only the polyp stage has been described (1981); Dowidar (1983); Boero and Sara (1987); once from the Spanish coast (García-Corrales et al., Brinckmann-Voss (1987); Calder (1991); Altuna 1979), presumably a doubtful determination, this Prados (1993b); Pagès et al. (1992); Boero and species being considered as endemic from South Bouillon (1993) Avian et al. (1995). Africa, see Millard (1975). Remarks: Brickmann (1959a) reared young References: Kramp (1961); García-Corrales et al. medusae, which at birth presented already lateral cirri (1979); Boero and Bouillon (1993). and marginal warts from a hydroid that she tentative- Remark: the juvenile medusae of the above ly identified with the Haleciidae Haleciella microthe- described species do not present enough diagnostic ca Hadzi, 1914. The comparison of the 14 days old features to be assigned to one or another medusa medusae from laboratory with young and adult family, the polyp stage closely resembles that of medusae found in the plankton let her to identify Lovenella clausa hence its inclusion in the genus those young medusae as Lovenella cirrata. Haliciella Lovenella by Millard (1957, 1975) and Bouillon microtheca considered as a Haleciid has been syn- (1985a) and in the present paper, awaiting further onymized with Campalecium medusiferum Torrey, informations about the mature medusa stage. 1902 by Huvé (1954), as Campalecium cirrata by Millard and Bouillon (1975) and Yamada (1995) and Lovenella cirrata (Haeckel, 1879) as Mitrocomium cirratum by Calder (1991). (Fig. 88I) In our opinion, the hydroid described by Brinck- mann (1959a) (see above for the description) is not Hydroid: colonies typically stolonal issued from a haleciid but is a campanulinid hydroid with a creeping hydrorhiza from which arise numerous reduced hydrotheca similar to those described by (up to almost 100) solitary, almost sessile, Werner in Eucheilota maculata and in Eutonina unbranched; hydranths; hydrothecae very shallow, indicans and found in several Eirenidae hydroids collar shaped, marginal rim somewhat everted, with (see Werner, 1968 Fig. 14, and Figs. in Russell, a distinct basal diaphragm; hydranth very elongated, 1970a). Brinckmann in 1959 was not aware of the slender, tapering gradually to base and just below existence of such hydrothecal structures and nor- tentacles base which is the widest part of the body, mally interpreted the short priest collar-shaped with a cone-shaped hypostome, with 24 tentacles in hydrotheca of Lovenella cirrata as a haleciid one. one whorl, amphicoronate, hydranths not retractable Millard (1975) already pointed out the resemblance into hydrothecae, intertentacular web present with existing between the hydrothecae of haleciids to large elongated cnidocysts (presumably merotric- those of some campanulinids which have loosed hous haplonemes); gonothecae borne at the base of their operculae and distal parts; Boero and Sara the hydrothecae, half as long as the living hydranth, (1987) underlined the possibility that Campanulin- tubular, conical tapering from end to base, aperture idae hydranths with reduced hydrothecae could have apical extending along whole width; gonophore been assigned to the Haleciidae and speculated that with 4 medusa buds (after Brinckmann, 1959a). such a type of campanulinids could be at the origin

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of the haleciids which by paedomorphis loosed the tude to any Leptomedusae family, their polyps are medusa phase while the hydroids became more rather similar to those of L. cirrata. Campalecium developed. Very close affinities seems thus undeni- cirratum medusae are only known from gonophores ably exist between this two families and the sub- as medusa buds which seems to present lateral cirri; order Haleciida proposed by Bouillon (1984b) to their polyps have pedicels of variable length, they match with the other orders he introduced at the occasionally may present one or two sympodial same time should be suppressed, the Halecioidea branches, they have microbasic mastigophores being included in the Campanulinida. cnidocysts (Millard and Bouillon, 1975) instead of Hydranthea margarica hydroids liberate free the merotrichous haplonemes present in the two eumedusoids and have great affinities with the cam- other species. More studies on Campalecium panulinid polyps mainly by their particularly elon- medusiferum and C. cirratum life cycles are gated body with a long non-digestive basal part, undoubtly needed, only the knowledge of their adult their unbranched polyps and merotrichous hap- medusae will clear up their real affinities. It is also lonemes cnidocysts. Hydranthea may represent still necessarily to clarify the problem of the syn- what could have been a first step to the loose of a onymy between the Mediterranean, American Cali- free medusae stage in the Lovenellidae leading so by fornia and Bermuda forms of Campalecium. It is paedomorphis and specialisation of the hydroid to interesting to underline that presently the adult the Haleciids with fixed gonophores (see Boero and medusae of L. cirrata are known from Mediter- Sara, 1987). Nemalecium lighti with campanulinid ranean, from the Malayan Archipelago, from the hydranths and eumedusoids is already a true haleci- Bismarck Sea, from Brazil and W.African waters id having pseudostenotele cnidocysts; this species but have never been found in eastern Pacific and the could represent a further step in the evolution to the North American basin from where the polyps of colonial and polymorphic haleciids. If this is the Campalecium medusiferum have been described case one of the two families (Lovenellidae and respectively by Torrey (1902) and Calder (1991). Haleciidae) both created by Hincks (1868) should have priority under the condition that the Haleciids Lovenella clausa (Lovén, 1836) are monophyletic. (Figs. 88J-K, 89A-D) There is a great confusion between the “Cam- palecium” like species. It is far from excluded that Hydroid: colonies comprising either single Haleciella microtheca, Campalecium medusiferum, pedicels or short erect shoots arising from a creep- Campalecium cirratum and Lovenella cirrata are all ing hydrorhiza; pedicels with 2-5 rings below conspecific as suggested by Clader (1991) who unit- hydrothecae and above origin from hydrorhiza; ed them all under the reintroduced generic name of hydrothecae long and narrow, thin walled, roughly Mitrocomium Haeckel, 1879. The differences cylindrical, tapering towards base, widest at aper- observed at the hydroid level being nothing else than ture; operculum of 8-10 triangular converging flaps variations that could be expected within a single seated in embayment of the hydrothecae margin and species. If such is the case the genus Lovenella sharply demarcated from the wall; often 2-3 reno- Hincks, 1868 has nevertheless precedence over: vated hydrothecae inside oldest one; hydranth long Campalecium Torrey, 1902; Haliciella, Hadzi, 1914 extending length of hydrotheca beyond aperture, and Mitrocomium Haeckel, 1879. with ca 14 –16 tentacles, probably no intertentacular However, we concur with Boero (1981a) that web; gonothecae elongated, axillary, tapering from Lovenella cirrata, Campalecium medusiferum and truncated end towards base, sides often slightly sin- Campalecium cirratum cannot be at the present uous, aperture terminal, containing up to 25 medusa stage of our knowledge considered as synonyms. buds maturing simultaneously The hydranths of Lovenella cirrata are different Medusa: umbrella 5-9 mm wide, hemispherical, from those of Campalecium cirratum being almost mesoglea moderately thick; manubrium short, sessile; solitary, their juvenile medusae present not small; without gastric peduncle; mouth with 4 sim- only lateral cirri but also the rudimentary warts char- ple lips; «gonads» oval, longitudinally divided, very acteristic of the adult medusa species. Only the new close to circular canal; 16-24 marginal tentacles; borne medusa of Campalecium medusiferum are marginal tentacular bulbs large, conical; 1-3 pairs of known and they are deprived from lateral cirri and lateral, spiral cirri on either side of each tentacular warts and cannot presently been assigned with certi- base; 16-23 statocysts.

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Records from Mediterranean: western Mediter- canals; «gonads» completely surrounding radial ranean. Medusa not known from Mediterranean, canals and separated from manubrium; with adaxial only dubious records of hydroids. excretory papillae; no permanent rudimentary mar- Known seasonality: 1, 4, 6, 7-9. ginal bulbs (all bulbs potentially transforming into Distribution: Atlantic; Mediterranean? tentacles); with closed statocysts; without ocelli; References: Kramp (1961); Picard (1958b); Gili without cirri. (1986); Boero and Bouillon (1993); Cornelius (1995); Medel and López-González (1996); Peña Genus Octophialucium Kramp, 1955 Cantero and García Carrascosa (2002). Malagazziidae medusa with normally 8 radial Lovenella gracilis (Clarke, 1882) canals; mouth with 8 lips. (Figs. 89E-G) Hydroid: where known of the “campanulinid” type, see family characters (Bouillon, 1984a, b). Hydroid: colonies with monosiphonic hydro- caulus slightly branched or unbranched; divided into Octophialucium funerarium internodes by septa at more or less regular intervals; (Quoy and Gaimard, 1827) (Figs. 89H-J) typical annulations absent except on the hydranth pedicels and at base of the stems; hydrothecae alter- Medusa: umbrella 30-40 mm wide, lens-shaped nate on short pedicels, operculum a folded continu- to saucer-shaped, mesoglea thick except near exum- ation of the hydrothecal wall, lacking hinge-like brellar margin, virtually no subumbrellar cavity; base, with about 8 facets when folded; 14 or more velum fairly broad; manubrium very small, with tentacles, no intertentacular web; diaphragm thin; base in form of eight-rayed star; mouth with 8 sim- gonothecae clavate, truncate terminally, borne near ple, short pointed lips; typically 8 straight, narrow, the base of hydrothecal pedicels, several medusa radial canals in adults (4 when young); «gonads» buds in each. short, along distal 1/4 of radial canals, near margin, Medusa: umbrella about 2.1 mm wide, 1.1 mm but not reaching circular canal; 64-128 marginal ten- high, hemispherical; velum wide; manubrium urn- tacles; marginal bulbs well developed, with excreto- shaped; mouth with 4 simple lips; 4 radial canals ry papillae; usually one to three, usually two, stato- and circular canal narrow; «gonads» oval midway of cysts between successive tentacles. radial canals length; oldest specimens with 21 mar- Hydroid: unknown. ginal tentacles each with 1 pair of cirri; 33 stato- Records from Mediterranean: eastern and west- cysts. ern Mediterranean; Adriatic. Remark: diagnosis taken from Calder (1971) and Known seasonality: 3-8, 12. based on raised material from polyp colonies. Distribution: Atlantic; Mediterranean. Records from Mediterranean: western Mediter- References: Kramp (1961); Goy (1973b); Bouil- ranean only juvenile medusae and hydroids known. lon (1985a, 1995a); Gili (1986); Benovic and Ben- Known seasonality: 5. der (1987); Boero and Bouillon (1993); Avian et al. Distribution: Atlantic; Mediterranean. (1995); Cornelius (1995); Benovic and Lucic References: Huvé (1952 a, b); Picard (1958b); (1996); Medel and López-González (1996); Mills et Calder (1971, 1991); Boero and Bouillon (1993). al. (1996).

Family MALAGAZZIIDAE Bouillon, 1984 Family MELICERTIDAE Agassiz, 1862

Hydroid: Where known of the “campanulinid Hydroid: where known colonies stolonal with type”; colonies stolonal; hydrothecae shortly pedi- branching stolons and erect shoots bearing one, cellate, with a conical operculum formed by numer- sometimes two, hydranths; perisarc thinning away ous convergent segment not clearly demarcated completely below base of the hydranths, no hydrothe- from the hydrothecal wall; hydranths with an inter- ca; hydranth large, broad in the middle, attenuate tentacular web; gonothecae claviform arising from below, tapering gently above, with narrow, amph- the stolons. icoronate tentacles; without intertentacular web; Medusa: with small manubrium; without gastric gonophores borne on the column of hydranth, no peduncle; with 4-8, sometimes up to 12 radial gonothecae (hydroid only known in Melicertum).

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Medusa: with base of manubrium attached over cles hollow; marginal cirri present in some genera; its whole surface; with eight simple or bifurcated with «gonads» oval or linear, only on radial canals; radial canals; with hollow marginal tentacles; with- with open statocysts. out marginal or lateral cirri and statocysts; with or References: Kramp (1932a); Pagès et al. (1992); without ocelli. Bouillon (1999); Bouillon and Barnett (1999); Reference: Russell (1963a). Bouillon and Boero (2000).

Genus Orchistomella Kramp, 1959 Key to medusae

Melicertidae with eight or more radial canals, all 1. With marginal cirri ...... 2 of which arise from manubrium; with or without – Without marginal cirri; with numerous open ocelli, «gonads» unknown. statocysts...... Foersteria Hydroid: unknown. 2. With numerous open statocysts ...... Mitrocoma – With 8-16 open statocysts...... Mitrocomella Orchistomella graeffei (Neppi and Stiasny, 1911) (No figure known) Genus Foersteria Arai and Brinckmann-Voss (1980) Medusa: umbrella 4 mm wide, highly vaulted, mesoglea very thick; gastric peduncle?; manubrium Mitrocomidae medusae with 4 radial canals; with quite flat; mouth with 8 simple lips; 8 fully devel- numerous open statocysts; without marginal cirri. oped radial canals and in each octant about 12 young Hydroid: unknown. blindly ending canals; 8 marginal tentacles with large pear-shaped marginal bulbs; 2-3 rudimentary 1. Manubrium short and very broad, 1/3 umbrella bulbs between successive tentacles. Probably young width, entirely coloured in dark purple-brown; specimens of Aequorea (Picard in Kramp, 1961 40 open statocysts; mouth with simple lips; with page 444). large rounded marginal bulbs...... F. antoniae Hydroid: unknown. – Manubrium short, small, 1/7 umbrella width, Records from Mediterranean: western Mediter- with 4 interradial brown lines; 7080 open ranean; Adriatic Sea. statocysts; mouth lips groove-shaped; marginal Known seasonality: 7-10. bulbs small, conical ...... F. araiae Distribution: endemic of Mediterranean Sea. References: Neppi and Stiasny (1911); Kramp Foersteria antoniae Gili, Bouillon, Pagès, (1959b, 1961, 1968); Goy (1973b); Boero and Palanques, Puig, and Heussner, 1998 Bouillon (1993); Avian et al. (1995); Benovic and (Figs. 90A-C) Lucic (1996). Medusa: umbrella up to 6 mm wide, 3 mm high, Family MITROCOMIDAE Haeckel, 1879 (part); flatter than a hemisphere, almost quadratic from Torrey, 1909 above, mesoglea rather thick; without gastric pedun- cle; manubrium very short and large with quadratic Hydroid: usually poorly known, most of the base, 1/3 of the width of the umbrella, intensely and “Cuspidella” type; hydrothecae tubular sessile; with uniformly coloured in dark purple-brown; mouth pyramidal operculum made either of several trian- with four simple, very short lips; radial canals and gular flaps, or of pleats in the continuing of circular canal narrow; «gonads» form and size hydrothecal tube, all not well demarcated from the depending on sex, male «gonads» elongated, on hydrothecal wall, lacking a crease-line at base of the about the 4/5 of the distal half of radial canals, flaps or pleats; hydranth extensile, with a single usu- female, «gonads» small, spherical, with few eggs (5- ally amphicoronate whorl of filiform tentacles; no 15) near circular canal; up to 40 marginal tentacles; intertentacular web; no nematophores; gonophores marginal bulbs large, rounded, with two masses of where known scarcely pedicellate, on hydrorhiza. brown pigment; up to 40 open statocyst, 0-2 Medusa: with bases of manubrium attached to between successive marginal tentacle. subumbrella along continuation of radial canals; Records from Mediterranean: western Mediter- with 4 or more simple radial canals; marginal tenta- ranean.

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Known seasonality: 4 and 5. tentacular membranous web; gonothecae unknown. Distribution: endemic of Mediterranean Sea. Medusa: umbrella 30-40 mm wide, flatter than a References: Gili et al. (1998). hemisphere, mesoglea thick; manubrium very small, Hydroid: unknown. 1/8-1/10 of umbrella diameter; mouth lips fairly short; radial canals and circular canal narrow; Foersteria araiae Gili, Bouillon, Pagès, «gonads» linear, sinuous, along distal 1/2-3/4 of Palanques and Puig, 1999 radial canals, not reaching circular canal, with a (Figs. 90D-E) median division; 60-100 wrinkled marginal tenta- cles, with conical bulbs; with 3-8 marginal cirri Medusa: umbrella up to 7 mm wide and high, between successive marginal tentacles; 60-100 open hemispherical, mesoglea thick; without gastric statocysts. peduncle; manubrium very short, with square base, Records from Mediterranean: western Mediter- with 4 interradial dark brown lines, 1/7 as high as ranean; Adriatic. umbrellar cavity and 1/7 as wide as umbrella; Known seasonality: 1-3; 5. mouth with four short, groove-shaped lips, sur- Distribution: endemic of Mediterranean Sea. rounded by cnidocysts, four radial canals and cir- References: Kramp (1932a, 1957b, 1961); Brin- cular canal narrow; «gonads» small, oval or round- ckmann-Voss (1987); Boero and Bouillon (1993); ed, split longitudinally, on distal half of radial Avian et al. (1995); Benovic and Lucic (1996). canals near but not in contact with circular canal; up to 40 long, coiled, marginal tentacles; marginal Genus Mitrocomella Haeckel, 1879 tentacular bulbs conical, small with brown pigment inside; 70-80 open marginal statocysts, 1-3 Hydroid: where known, colonies of “Cuspidella” between each two tentacles. type; with pleated operculum, presenting no clear Records from Mediterranean: western Mediter- limits with the hydrothecal margin; see family char- ranean. acters. Known seasonality: 5. Medusa: with 4 radial canals; with marginal cirri Distribution: endemic of Mediterranean Sea. which may or not be spirally coiled; with 8, 12 or 16 References: Gili, Bouillon, Pagès, Palanques and (exceptionally up to 19) statocysts. Hydroid: Where Puig (1999). known, colonies of “Cuspidella” type; with pleated operculum, presenting no clear limits with the Genus Mitrocoma Haeckel, 1864 hydrothecal margin; see family characters.

Hydroid: colonies where known of “Cuspidella” Mitrocomella brownei (Kramp, 1930) type, operculum with numerous sharp pointed, trian- (Figs. 91A-D) gular flaps meeting centrally and presenting no clear limits with the hydrothecal margin. Hydroid: only an incomplete diagnosis of a pri- Medusa: with 4 radial canals; with numerous mary polyp is known (Rees and Russell, 1937). open statocysts; with marginal cirri. Hydrothecae tubular, arising from a creeping stolon, with pleated conical operculum of about 5-7 teeth Mitrocoma annae Haeckel, 1864 meeting centrally and not clearly demarcated from (Figs. 90F-J) the hydrotheca; hydranth extensile, with 8-12 fili- form, amphicoronate tentacles, no basal web Hydroid: (Metschnikoff, 1886a) reared the between tentacles; hypostome conical; gonothecae hydroid of this medusa which is typically a «cuspi- unknown. dellid», the hydrothecae are sessile, cylindrical, Medusa: umbrella 4-9 mm wide; flatter than a wide and elongated and arise at irregular intervals hemisphere, mesoglea uniformly thin; manubrium from a linear, creeping, stolon; hydrothecae closed small, short, quadratic; mouth with 4 simple, slight- by a pyramidal operculum with numerous sharp ly recurved lips; 4 straight, narrow radial canals pointed, triangular flaps meeting centrally and pre- widen proximally as enter manubrium, circular senting no clear limits with the hydrothecal margin; canal narrow; 4 «gonads» near distal ends of radial hydranths extensile, with conical hypostome; 12-16 canals divided longitudinally, female somewhat filiform tentacles in a single whorl, no basal inter- elongated, male oval; typically 16, up to 24 margin-

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al tentacles; 6-8 spiral marginal cirri between suc- References: Kramp (1959a, 1961); Bouillon cessive tentacles; typically 8 (-11) open statocysts. (1984 a, b); Boero and Bouillon (1993). Records from Mediterranean: western Mediter- ranean. Family PHIALELLIDAE Russell (1953) Known seasonality: 4; 5. Distribution: Atlantic; Indo-Pacific; Mediter- Hydroid: colony stolonal or erect sympodial, ranean. arising from a creeping hydrorhiza; hydrotheca References: Kramp (1930, 1932a, 1957b, 1961); pedicellate, tubular to deeply campanulate, persis- Gili (1986); Pagès et al. (1992); Boero and Bouillon tent, with a cone-shaped operculum formed by sep- (1993); Cornelius (1995); Medel and López- arate triangular flaps demarcated or not from González (1996). hydrothecal margin by a basal crease line; diaphragm present; gonophores as free medusae, Family ORCHISTOMATIDAE Bouillon, 1984a gonotheca usually stolonal, sometimes on erect shoot. Leptomedusae with very short manubrium; with Medusa: manubrium small; no gastric peduncle; large gastric peduncle; mouth with 8-30 sinuous or 4 radial canals; “gonads” on radial canals, separated crenulated lips; with 8 or more radial canals, simple, from manubrium and divided into two lateral parts ramified, or in clusters of 4; up to 64 marginal ten- by a median groove; tentacles hollow, smooth or tacles, laterally compressed; no marginal cirri, but moniliform; no excretory pores, lateral or marginal numerous filiform tentaculiform structures devoid cirri; 8 closed statocysts, usually each on a bulbous- of marginal bulbs, not in contact with circular canal, like swellings; without ocelli. in each intertentacular space; «gonads» usually on References: Russell (1963b); Boero (1987); proximal parts of radial canals; numerous (up to Calder (1991). 800) adaxial ocelli; no statocysts or cordyli; without excretory pores or papillae. Genus Phialella Browne, 1902 Hydroid: unknown. Medusa and hydroids with the characters of the Genus Orchistoma Haeckel, 1879 family.

With the characters of the family. Phialella quadrata (Forbes, 1848): (Figs. 91F-J, 92A-C) Orchistoma agariciforme Keller, 1884 (Fig. 91E) Hydroid: colonies formed of simple or alternate- ly branched hydranths rising from a creeping Medusa: umbrella up to 15 mm wide, 5 mm high; smooth hydrorhiza; hydrocaulus erect, distinctly flat-topped with vertical sides, apical mesoglea very annulated throughout; hydrothecae conical, campan- thick; manubrium cruciform, wide and very shal- ulinid, on ringed pedicel closed by a ca 10 pleated low; large funnel-shaped, gastric peduncle, longer membranous operculum formed of deep and acute than umbrella cavity; mouth with 4 groups of 4 long convergent segments, meeting centrally and not complexly folded lips; 16-20 or more radial canals, clearly demarcated from the hydrothecal margin, more or less in group of 4-5; one swollen gonad on with a delicate diaphragm; hydranths very extensile each radial canal, close near manubrium; 16-27 or with about sixteen oral filiform tentacles in one more short marginal tentacles; with elongated coni- whorl; gonothecae large, flat-topped, tapering cal marginal tentacular bulbs; about 8-10 tentaculi- sharply below, usually rising from hydrorhiza more form structures without bulbs and connections with occasionally from hydrocaulus on short annulated the circular canal, adnate to exumbrella, between stems. tentacles; about 16-20 adaxial ocelli between suc- Medusa: umbrella 13 mm wide, nearly hemi- cessive tentacles, no ocelli on the tentacular bulbs. spherical, mesoglea fairly thick; manubrium qua- Records from Mediterranean: western Mediter- dratic, short, with small base; with 4 short, slightly ranean. folded recurved lips; radial canals and circular canal Known seasonality: 9-11. narrow; «gonads» on distal third of radial canals, but Distribution: Indo-Pacific; Mediterranean. not reaching bell margin, elongated-oval, with a

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characteristic median groove; 16-32 hollow margin- Genus Monotheca Nutting, 1900 al tentacles with small globular marginal bulbs; no ocelli; with 8 statocysts on cushion-like bulbous Colonies minute, erect, monosiphonic, with swellings; often with 4 black interradial spots on unbranched or sparingly branched stems; hydrocladia base of manubrium. alternate, typically unbranched, short, each with two Records from Mediterranean: eastern and west- internodes: a basal ahydrothecate one and second, ern Mediterranean, Adriatic. bearing the terminal hydrotheca; hydrotheca large, Known seasonality: 6, 8, 10, 11. only on hydrocladia, margin more or less entire, sinu- Distribution: Atlantic; Indo-Pacific; Mediter- ous; adcauline side completely adnate to internode, ranean. hydrothecate internode with a single median inferior References: Huvé (1953) ?; Kramp (1961); nematotheca and a terminal pair of lateral nematothe- Schmidt (1973); Schmidt and Benovic (1977); Gar- cae above hydrothecae, cauline nematothecae present cía-Corrales et al. (1979)?; Fulton et al. (1985); Gili or not ; nematothecae ordinarily bithalamic, movable; (1986); Goy et al. (1988, 1990, 1991); Boero and gonophores as solitary fixed sporosacs or swimming Bouillon (1993); Avian et al. (1995); Cornelius gonophores (M. obliqua, M. margaretta), gonothecae (1995); Medel and López-González (1996). at base of hydrocladium, usually large, ovate, truncat- ed distally and tapering at base, with wide terminal Family PLUMULARIIDAE McCrady, 1859; opening, usually lacking nematothecae, not protected. Remarks: some Monotheca may occasionally Colonies upright, monosiphonic or polysiphon- have 2-3 hydrotheca per hydrocladium so, they are ic, arising from creeping, rootlike, or disc-shaped often treated as a synonym of Plumularia (see Mil- hydrorhiza; hydrocauli branched or unbranched, lard, 1975; Bouillon, 1985; Hirohito, 1995). hydrocladia alternate, opposite or in verticils, aris- References: Medel and Vervoort (1995); Migotto ing in polysiphonic hydrocauli from a single axial (1996); Calder (1997); Gravier and Migotto (2000). tube; hydrothecae typically small (hydranths usual- ly too large to fit inside hydrotheca), with or with- 1. Abcauline wall of hydrotheca convexe; one or out marginal cusps, uniseriate, usually at least par- two nematotheca in axil of hydrocladium...... tially adnate, occurring only on hydrocladia, ...... M. obliqua. cauline hydrothecae absent; nematophores with – Abcauline wall of hydrotheca straight or well developed nematothecae, not as naked sar- concave; two nematothecae in axil of costyles; all nematothecae (axillar, cauline or hydrocladium ...... M. pulchella. hydrothecal) usually two-chambered (bithalamic) and movable, a minimum of three nematothecae Monotheca obliqua (Johnston, 1847) adjacent to hydrothecae, one mesial inferior and a (Fig. 92D-F) pair of lateral ones; gonophores as fixed sporosacs, exceptionally as swimming gonophores; gonothe- Colonies with erect and unbranched stem up to cae solitary, without nematothecae; with or without 40 mm, growing on flattened stolons with distinct phylactocarps (Fig. D: Figs. 2 and 3; Fig. G: Fig. internal partitions. Stem zigzag, internodes slight- B2; Fig. H: Fig. 2A). ly curved, each bearing a latero-distal apophysis, References: García Corrales et al. (1978); Cor- one to two nematothecae at the level of the apoph- nelius (1995); Hirohito (1995); Migotto (1996); ysis insertion, and another nematothecae on the Medel and Vervoort (1995); Calder (1997); Calder segment. Hydrocladia borne on the apophyses, and Vervoort (1998); Peña Cantero and Vervoort each comprising a basal athecate internode and (1999); Watson (2000); Ansín Agís et al. (2001). another with one hydrotheca surrounded of three nematothecae, one median inferior which reach 1. Hydrocladia bearing a single hydrothecae, the base of the hydrotheca, and two immediately pseudoterminally ...... Monotheca above and behind hydrotheca. All nematothecae – Hydrocladia bearing several hydrothecae ...... 2 two chambered, basal chamber narrow, tubular; 2. Hydrocladia arranged in alternate verticils ...... distal cup-shaped. Hydrothecae cup-shaped, entire ...... Nemertesia adnate, rim even but sinuous, aperture at right – Hydrocladia not arranged in verticils...... angle with the internode. Gonothecae imperfectly ...... Plumularia known: male oval narrowing both ends, apical

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aperture small; female cylindrical, truncate distal- Genus Nemertesia Lamouroux, 1812 ly, tapering basally, borne on stem below = Sciurella Allman, 1883 hydrothecae. Records from Mediterranean: western and east- Colonies monosiphonic or polysiphonic, ern Mediterranean, Adriatic. branched or unbranched; coenosarc of the stem Known seasonality: 1-6-10, 12. canaliculated or not; hydrocladia arranged in verti- Reproduction: 2, 5-10. cils in mature colonies, number of hydrocladia per Distribution: cosmopolitan. verticil typically increasing with age, young colonies References: García-Corrales et al. (1978); Boero sometimes just biseriate, pinnate; hydrocladia of one and Fresi (1986); Gili (1986); Roca (1987); Avian et verticil typically alternating with those above and al. (1995); Cornelius (1995); Medel and López- below, forming twice (or more) the number of longi- González (1996); Peña Cantero and García Carras- tudinal rows, increasing progressively up the colony; cosa (2002) hydrothecae cup-shaped, margin even; hydrothecal nematothecae two-chambered, movable; gonophores Monotheca pulchella (Bale, 1882) as fixed sporosacs; gonotheca unprotected, usually (Figs. 92G-K) borne on hydrocladial apophysis, without nema- tothecae. Colonies comprising strong and reticulated Remarks: Allman (1871) reported reduced medu- hydrorhizae with erect, monosiphonic and usually soids in Nemertesia antennina but his observation unbranched hydrocauli up to about 7 mm high. Main has not been confirmed by further studies (see Mil- stem segmented into internodes by means of trans- lard, 1975; Hughes, 1977). verse nodes. Each segment with three nematothecae Recent references: Schuchert (2001a, 2003). and a latero-distal apophysis; nematothecae seated one lower on the axis, and the others flanking the 1. Hydrocladia having a hydrotheca not on every apophysis. Hydrocladia borne on the apophyses, internode or on alternate internodes alternate, each composed of two segments, the basal (heteromerously segmented) ...... 2 one athecate, limited by transverse nodes and with an – Hydrocladia having a hydrotheca on every internal perisarcal rim distally; the distal one thecate, internode (homomerously segmented)...... 4 with one hydrotheca and three nematothecae, one 2. First hydrocladial internode athecate, with one median inferior reaching the base of the hydrotheca, nematotheca; rest of hydrocladium composed of and two laterals above the hydrotheca. Hydrotheca thecate intenodes separated by oblique nodes..... deep campanulate, completely adnate, margin even ...... N. fascicule somewhat everted, aperture almost 90º with the axis. – Thecate and athecate hydrocladial internodes Nematothecae all similar and two-chambered; basal alternating...... 3 chamber narrower and longer; distal chamber cup- 3. Non hydrothecate internodes usually with one shaped, inner side lowered. Gonothecae inserting nematothecae ...... N. antennina usually on basal segments of stem; female big, cylin- – Non hydrothecate internodes constantly with two drical, truncate distally, ringed throughout, aperture nematothecae...... N. perrieri apical, with a circular lid. 4. Internodes with several transverse perisarcal Records from Mediterranean: western Mediter- septa ...... N. ventriculiformis ranean (Spain). – Internodes without septa ...... 5 Known seasonality: 2, 5, 7, 8, 12. 5. Coenosarc of main stem not caniculate, Reproduction: 2, 7, 8. gonotheca crescent-shaped ...... N. norvegica Distribution: Atlantic coasts of the Strait of – Coenosarc of main stem caniculate, gonotheca Gibraltar; Indo-pacific (Australia, New Zealand), curved-ovoid or elongated...... 6 South Africa and Argentine, western Mediterranean 6. Hydrocladial internodes with 4 nematothecae .... (Spain)? ...... N. ramosa References: Ralph (1961); Watson (1973); Mil- – Hydrocladial internodes with 3 nematothecae .... lard (1975); García-Corrales et al. (1978) as Plumu- ...... N. tetrasticha laria femina; Boero and Bouillon (1993) as Plumu- laria; Medel and Vervoort (1995); Medel and Nemertesia antennina (Linnaeus, 1758) López-González (1996). (Figs. 92L-S)

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Hydrorhiza formed by a mass of intertwining in distal part apophysis and hydrocladia alternately and branched fibers springing from basal part of the directed left an right, forming a plumularoid form of stems. Hydrocauli monosiphonic, up to 350 mm colony in those part; each apophysis with “mamel- high, unbranched and divided into internodes by on” on superior surface, with two axillary and occa- means of indistinct transverse nodes; each segment sionally additional nematothecae above “mamelon”; bearing one or two verticils with four to six first hydrocladial internodes with one nematotheca, apophyses; each verticil alternate in position with rest of hydrocladium composed of thecate intenodes the following; a “mamelon” and up to seven nema- separated by oblique nodes, each with one hydrothe- tothecae on upper surface of each apophysis. cae and four nematothecae: one mesial inferior, two Coenosarc of the stem canaliculated. Perisarc of the laterals, and one suparcalycine; hydrothecae small, hydrocladia thin, contrary to the thick one of the cup-shaped, adcauline wall completely adnate; apophyses. Hydrocladia heteromerously segmented abcauline wall thickened in older hydrothecae; rim by means of oblique to transverse nodes; basal- even, perpendicular to the length of the axis; lateral most part with two shorter internodes each bearing nematothecae inserted on small apophyses near one nematotheca; non-hydrothecate segments with hydrothecal rim; all nematothecae two-chambered one nematotheca (occasionally two), hydrothecate and movable; gonothecae inserted on apophyses, internodes with one hydrotheca and three nema- with a short pedicel, strongly curved, falcate; aper- tothecae, one median inferior and two laterals. ture laterally displaced, circular, apparently with a Hydrotheca small, cup-shaped, entire adnate to the circular operculum; male and female gonothecae on axis, rim even, somewhat sinuous, aperture slightly same colonies, female gonothecae in medio-distal directed downwards. All nematothecae two cham- part, male gonothecae above female ones on distal bered and conical; basal chamber longer than api- part of colony. cal, this provided with adcauline embayment; in Records from Mediterranean: western Mediter- some colonies, basal chamber of lateral nematothe- ranean. cae rather elongated. Gonothecae borne on the Known seasonality and reproduction: 6-7. apophyses, male and female similar, ovoid, with Distribution: Atlantic, Mediterranean. oval latero-distal aperture. References: Ramil and Vervoort (1992a); Medel Records from Mediterranean: western Mediter- and López-González (1996) all as Plumularia falci- ranean, Adriatic. cula; Ansín Agís et al., 2001. Known seasonality: 5-8, 10-12. Reproduction: 7, 10. Nemertesia irregularis (Quelch, 1885) Distribution: cosmopolitan. = Nemertesia antennina. References: Vervoort (1966); Gili (1982); Ramil and Vervoort (1992a); Cornelius (1995); Avian et al. Nemertesia norvegica (G.O. Sars, 1874) (1995); Medel and Vervoort (1995); Medel and (Figs. 93F-K) López-González (1996); Schuchert (2001a). Colonies up to 100 mm, small, delicate, main Nemertesia falcicula (Ramil and Vervoort (1992) stem straight, usually monosiphonic; coenosarc of (Figs. 93A-E) main stem not caniculated; internodes elongated; 2- 8 hydrocladia per internode; hydrocladia biseriate, Colonies rising from an intertwining hydrorhiza straight; alternate-pinnate basally, bushy distally; of perisarcal fibers, supporting one tubular polysi- hydrotheca wholly adnate, uniseriate, with straight- phonic stem giving rise to several monosiphonic and sides with a tendency to jug-like lip towards outer unbranched hydrocauli, up to 25 mm high; margin; nematothecae typically one mesial and two hydrorhiza covering basal part of the axis with laterals, but arrangement varied between colonies; numerous two chambered nematothecae (basal gonothecae borne single or by pairs, on minute chamber narrow and longer, distal one cup shaped); apophysis, crescent-shaped to sausage-shaped, aper- hydrocauli divided into internodes by straight, at ture circular. times obscure nodes; each internode with one to Records from Mediterranean: western Mediter- three distal apophyses and one to four nematothecae ranean. under apophysis; in basal part of hydrocauli apoph- Known seasonality: 1, 7. ysis and hydrocladia in decussate verticils of three, Reproduction: ?

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Distribution: Atlantic and Mediterranean. ramified tubes giving rise large polysiphonic and References: Cornelius (1995); Schuchert (2000; branched stems up to about 200 mm high. Hydro- 2001a); Ansín Agís et al. (2001). cauli with a thick perisarc, one of the tubes of greater diameter, giving rise hydrocladia in the Nemertesia perrieri (Billard, 1901) monosiphonic and weakly polysiphonic parts and (Figs. 93L-Q) divided into internodes by means of transverse nodes. Coenosarc of main stem canaliculate. Colonies with a intertwined hydrorhizal matting Apophyses of hydrocladia at nodes, in opposite springing from basal parts of the axis; hydrocauli pairs in younger parts of the axis, in verticils of three monosiphonic, up to about 250 mm, each with sever- to ten in the older ones; verticils of succeeding pairs al internal coenosarcal tubes, with a thick perisarc, alternate. Apophyses with a “mamelon” on the segmented into internodes by badly visible straight upper surface and several nematothecae (up to transverse nodes; each internode with a verticil of seven); perisarc very thick, contrary to the thin three to four apophyses distally, verticils decussate; perisarc of the hydrocladia. Hydrocladium separated no nematothecae visible on hydrocaulus, each apoph- into thecate internodes by means of transverse ysis with small “mamelon” on superior surface and nodes, each with one hydrothecae and four nema- four or five nematothecae, two in the axil, one pair tothecae, one median inferior, two laterals and one above “mamelon” and one unpaired at distal end of median superior at the distal part of the segment. apophysis near node; hydrocladia with a thin perisarc, Hydrothecae small, cup-shaped, entire adnate, rim heteromerously segmented into hydrothecate and even, aperture at right angle with the axis. Nema- non-hydrothecate internodes by means of transverse tothecae all two-chambered, conical; basal chamber to oblique nodes; basal-most internode shorter, longer, apical chamber shorter, with a wide hydrothecate segments with one hydrotheca and three adcauline embayment. Male and female gonothecae nematothecae, one median inferior and two laterals; similar, ovoid, obliquely truncated distally with a non-hydrothecate internodes with two nematothecae, subterminal and oval aperture, narrower basally, one in lower third one in upper third; all internodes with a short pedicel. with two internal perisarc rings of varied develop- Records from Mediterranean: eastern and west- ment; hydrotheca small, cup-shaped, with diverging ern and central Mediterranean, Adriatic. walls, adcauline wall entirely adnate, rim smooth, Known seasonality: 6, 7, 10-3. even, without lateral undulations; all nematothecae Reproduction: 1, 2, 7, 12. two-chambered, conical, basal chamber longer than Distribution: eastern Atlantic; western Atlantic apical, this with adcauline embayment, movable; only in Greenland, Mediterranean. gonothecae on apophysis, on short pedicel, ovoid, References: García-Carrascosa et al. (1987) as N. with elongated latero-distal and oval aperture. disticha; Ramil and Vervoort (1992a); Boero and Records from Mediterranean: western and cen- Bouillon (1993); Avian et al. (1995); Cornelius tral Mediterranean. (1995); Medel and Vervoort (1995); Medel and Known seasonality: 1 to 8. López-González (1996); Ansín Agís et al. (2001); Reproduction: 2 to 8. Schuchert (2001a); Peña Cantero and García Carras- Distribution: mainly eastern Atlantic; Pacific, cosa (2002). Mediterranean. References: Vervoort (1959); Gili, Vervoort and Nemertesia tetrasticha (Meneghini, 1845) Pagés (1989); Ramil and Vervoort (1992a) as N. (Figs. 94G-K) irregularis; Medel and Vervoort (1995) as N. irreg- ularis; Medel and López-González (1996) as N. Polysiphonic colonies irregularly branched. Seg- irregularis; Ansín Agís et al., (2001); Peña Cantero ments of the stem with two lateral apophysis with one and García Carrascosa (2002). “mamelon” and four nematothecae at upper surface. Coenosarc of main stem canaliculate; hydrocladia Nemertesia ramosa (Lamarck, 1816) borne on the apophyses, two cladia per segment, (Figs. 94A-F) alternate in position. Internodes of the hydrocladium with one cup-shaped hydrotheca and three nema- Well developed colonies composed of strongly tothecae, one median inferior and two laterals; nodes intertwined hydrorhizal matting, formed by many slightly oblique. Gonothecae on short pedicels, borne

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on the axils of the stem with the apophyses; elongat- hydrothecae occurring only on hydrocladia, typical- ed, aperture sub-apical and circular. ly two or more per hydrocladium, small, typically Records from Mediterranean: western Mediter- cup-shaped, partly or almost totally adnate, margin ranean, Adriatic. entire, unthoothed; with or without intrathecal sep- Distribution: endemic of the Mediterranean Sea. tum; axil and cauline nematothecae variable in num- References: García-Carrascosa et al. (1987) as N. ber, three hydrothecal nematothecae, one median disticha; Boero and Bouillon (1993); Avian et al. and two lateral ones flanking each hydrotheca, ordi- (1995); Medel and López-González (1996). narily bithalamic and movable; gonophores as soli- tary, unprotected, fixed sporosacs, neither armed Nemertesia ventriculiformis (Marktanner- with nematothecae, sometimes with acrocyst. Turneretscher, 1890) (Figs. 94L-P) 1. With one nematothecae on non-hydrothecal segments ...... P. setacea Hydrocauli up to about 50 mm high, monosi- – With two nematothecae on non-hydrothecal phonic, occasionally polysiphonic basally, and segments ...... P. syriaca unbranched; hydrorhiza composed of many ramified tubes. Stem in adult colonies undivided, arrange- Plumularia setacea (Linnaeus, 1758) ment of apophyses along axis without characteristic (Figs. 95A-E) pattern, but all in various vertical planes with ten- dency to form verticils; however many different Colonies pinnate composed of monosiphonic and arrangement may occur, including an irregular dis- unbranched hydrocauli up to ca 60 mm, with alter- position. A “mamelon” and generally four nema- nate hydrocladia. Stem divided into internodes by tothecae are disposed on upper surface of apophy- means of transverse nodes, each segment bearing ses. Hydrocladia homomerously segmented; nodes two nematothecae, one basal and one distal, the last oblique. Segments, also the apophyses, may develop almost in the axil of a lateral apophysis. Hydrocla- internal transverse septa (up to 12 per internode). dia borne on the apophyses of the stem, alternate, in Internodes with one hydrotheca in basal third and the same plane, heteromerously segmented into four nematothecae, one median inferior, two laterals hydrothecate and non-hydrothecate internodes by and one median superior (occasionally placed on means of transverse nodes. Hydrothecate internodes separated intermediated segment). Hydrotheca with one hydrotheca and three nematothecae, one small, cup-shaped, entire adnate, rim even, aperture median inferior and two latero-superiors. Non- at right angle with the axis. All nematothecae two- hydrothecate segments with one frontal nematothe- chambered. Gonothecae on short pedicels, elongat- ca, usually with one perisarcal septum above and ed and curved, aperture sub distal. below it; septum also may occurs basally on Records from Mediterranean: western Mediter- hydrothecate internodes. First hydrocladial intern- ranean. ode athecate and shorter. Hydrotheca cup-shaped, Known seasonality and reproduction: 6. entire adnate, rim even, aperture slightly tilted Distribution: temperate eastern Atlantic and downwards. Nematothecae all two-chambered, con- Mediterranean. ical, basal chamber longer, apical one shorter and References: Castric-Fey (1970); Vervoort (1959, wider, provided with adcauline embayment. 1972) both as N. incerta; Ramil and Vervoort Gonothecae on the same stem or not, typically form- (1992a); Medel and López-González (1996). ing neat continuous line down central axis; female elongated fusiform, smooth, narrower distally with a Genus Plumularia Lamarck, 1816 tubular neck more or less developed; apical aperture narrow and circular; male narrower and smaller than Colonies normally erect (stolonal when epi- female, less attenuate above, tapering to a minute zooic), arising from a creeping hydrorhiza or from orifice. anchoring filaments; hydrocauli mostly monosi- Records from Mediterranean: western and east- phonic, branched or unbranched, giving off alternate ern Mediterranean (up to Greece), Adriatic. apophyses; hydrocladia typically unbranched, pin- Known seasonality: 2-8, 11, 12. nately arranged or sometimes occurring in gradual Reproduction: 2, 3, 5-9. spiral, but not in verticils, divided into internodes; Distribution: cosmopolitan.

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References: Rossi (1961); Millard (1975); Gar- Fraseroscyphus gonothecae arising from within cía-Corrales et al. (1978); Gili (1982); Ramil and hydrothecal cavity. Vervoort (1992a); Boero and Bouillon (1993); Avian Remarks: the Sertulariidae is the most speciose et al. (1995); Cornelius (1995); Medel and Vervoort Hydrozoan family and are generally easily recog- (1995); Medel and López-González (1996); Watson nised at family level. Their delimitation into genera (2000); Ansín Agís et al.(2001); Schuchert (2001a) is, however, a hazardous and controversial question Peña Cantero and García Carrascosa (2002). due to the great variability among genera, generic diagnoses being poorly differentiated from each Plumularia syriaca Billard,1931 other and often overlapping. Generic diagnoses are (Fig. 95F) mostly based on colony form (stolonal or erect) and on thecae characters such as hydrothecal shape, Colony erect, not branched, monosiphonic, 5 cm in position, structure, and number hydrothecal teeth, height. Hydrocaulus with caulines nematothecae. number of opercular flaps, etc., but some of these Hydrocladia alternate, borne on apophyses of the stem characters are variable, even in a single colony. having two or three nematothecae and a mamelon at Hydranth characters such as the presence or absence their base. Hydrocladia heteromerously segmented of an abcauline caecum, of an annular ectodermal into hydrothecate and non-hydrothecate internodes by fold (see glossary) have been given great importance means of transverse nodes. Hydrothecate internodes for separating genera, but those structures have also with one hydrotheca and three nematothecae, one not been seriously and systematically investigated in median inferior and two latero-superiors. Non- all the described genera or species or even families. hydrothecate segments with two nematothecae. The Sertulariidae comprise an unreasonable number Hydrotheca small, cup-shaped, entire, adnate, rim of species, more than 500! (only 800 valid species of even. Nematothecae all two-chambered, conical, basal medusae have been recorded for all the superclass chamber longer, apical one shorter and wider. Hydrozoa), population variations of a single species Gonothecae not known. have often been given a specific rank, and it should Records from Mediterranean: eastern Mediter- be refrained to describe new genera and species ranean (Alexandrette). without having actually studied specific population Seasonality: ? variations, both external and internal hydranth mor- Distribution: endemic of Mediterranean Sea. phology and life cycles. References: Billard (1930-1931); Boero and References: Nutting (1904); Splettstösser (1929); Bouillon (1993). Vervoort (1993b) list; Cornelius (1995); Hirohito (1995); Migotto (1996); Calder and Vervoort Family SERTULARIIDAE Lamouroux, 1812 (1998); Watson (2000); Schuchert (2001, 2003); Vervoort and Watson (2003). Colonies normally erect, exceptionally stolonal; hydrothecae bi- or multiseriate, exceptionally, secon- 1. Hydrothecae apparently uniseriate ...... darily apparently uniseriate trough secondary modifi- ...... Hydrallmania cation, sessile through adnate to wholly sunk within – Hydrothecae biseriate...... 2 perisarc, or exceptionally pedicellate, radially to bilat- 2. Hydrotheca with operculum of one flap (valve). erally symmetrical, rim usually cusped, operculum of ...... 3 1-4 flaps; diaphragm in the few pedicellate forms, – Hydrotheca with operculum of two or four flaps others having a clearly defined basal floor pierced by ...... 5 narrow and eccentric hydropore (excepting Sertu- 3. Flap adcauline...... Diphasia larella diaphana); hydranth completely retractable in – Flap abcauline ...... 4 hydrotheca, in some species with abcauline gastric 4. Retracted hydranth with abcauline caecum...... caecum when hydranth contracts and mantle (ecto- ...... Thuiaria dermal lamella); cnidome: generally small and often – Retracted hydanth without abcauline ceacum..... large microbasic mastigophores and sometimes hap- ...... Salacia lonemes; gonophore as fixed sporosacs, exceptional- 5. Operculum of four flaps; rim with four cusps .... ly as swimming gonophores (Amphisbetia opercula- ...... Sertularella ta), gonothecae solitary, usually sexually dimorphic, – Operculum of two flaps...... 6 on stem or branches, acrocyst often present, in 6. Hydrothecal cusps markedly unequal ......

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...... Amphisbetia opposite to alternate pairs, hydrothecal margin sprout- – Hydrothecal cusps approximately equal ...... 7 shaped, unthoothed or with 2 to 4 teeth, operculum of 7. Retracted hydranth without abcauline caecum; one adcauline flap; gonophores as fixed sporosacs; hydrothecal pairs often grouped ...... Dynamena gonothecae sometimes with spines forming brood – Retracted hydranth with abcauline caecum; chambers (marsupium) in females. hydrothecal pairs never grouped...... Sertularia References: Calder (1991); Cornelius (1995); Hirohito (1995). Genus Amphisbetia L. Agassiz, 1862 1. Hydrotheca typically totally transversally ringed Colonies erect, usually branched, monosiphonic; ...... D. delagei hydrothecae opposite and biseriate, roughly tubular – Hydrotheca not transversally ringed ...... 2 and partly adnate, with 2 long sharp abcauline mar- 2. Main stem broader than hydrocladia in well ginal cusps and sometimes a small adcauline one; developed colonies ...... 3 operculum of 2 unequal valves, larger one adcauline, – Main stem same width as hydrocladia in well smaller one abcauline; retracted hydranth with developed colonies* ...... 4 abcauline caecum; gonophores as fixed sporosacs, or 3. Hydrotheca sharply out-turned, hydrocladia swimming gonophores (Amphibestia operculata), rigidly straight, male and female gonothecae gonothecae solitary, large, usually ovate. similar...... D. pinastrum – Hydrotheca gradually out-turned, hydrocladia Amphisbetia operculata (Linnaeus, 1758) not rigidly straight, male and female gonothecae (Figs. 95G-I) different...... D. margareta 4. Hydrotheca with longitudinal grooves on the Colonies with erect stems (up to ca 145 mm) and wall; female gonotheca with brood chamber and reticulated hydrorhizae; hydrocauli dichotomously without spines ...... D. rosacea branched, no difference between hydrocaulus and – Hydrotheca without longitudinal grooves on the hydrocladia structure, nodes transverse; hydrothecae wall; female gonotheca without brood chamber tubular, one pair per internode, adcauline walls con- and with spines...... D. attenuata vex, 1/2 to complete adnate; abcauline walls straight, with a thick perisarc, aperture sloping inwards, rim *excepting in D. attenuata var. robusta. with a long abcauline cusp and one or two short lat- eral ones; reproduction by swimming gonophores; Diphasia attenuata (Hincks, 1866) gonothecae of both sexes probably indentical, large, (Figs. 95J-N) ovate, aperture terminal and circular, on a very short collar and one-flapped operculum. Colonies (up to ca 50 mm) with erect and mono- Records from Mediterranean: western Mediter- siphonic hydrocauli bearing hydrocladia arranged ranean, Adriatic. pinnately, in the same plane; stem and hydrocladia Known seasonality: 6, 7. same width (excepting in the var. robusta). Hydrothe- Reproduction: 6. cae in opposite pairs on axis and on hydrocladia, Distribution: almost cosmopolitan, though tubular, curved gradually (not sharply) outwards; avoiding pure Arctic and Antarctic. adcauline wall 1/2-1/3 adnate; aperture circular, rim References: Millard (1975); García-Corrales et al. even, with deep adcauline embayment; operculum (1980); Gili (1982); Ramil (1988); Boero and Bouil- circular attached to adcauline side; hydrothecal reno- lon (1993); Cornelius (1979, 1995); Medel and vations frequent. Male gonotheca cylindrical, with 6 López-González (1996); Medel and Vervoort (1998). longitudinal ridges ending above in points; female 6- sided, with 1-3 whorls of elongated spines distally Genus Diphasia L. Agassiz, 1862 and aperture on small terminal cone. Records from Mediterranean: Strait of Gibraltar. Colonies erect, pinnately branched or unbranched; Known seasonality: 1, 5, 6. hydrocaulus mono- or polysiphonic; hydrocaulus, and Reproduction: 5. hydrocladia when present, with hydrothecae in 2, Distribution: mainly records from temperate and rarely 3 longitudinal rows; hydrotheca tubular, sessile, tropical eastern Atlantic, but also several records adnate to partly sunk, usually expanding distally, in from the Pacific, Strait of Gibraltar.

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References: Vervoort (1959); Cornelius (1979, in cross section, with a spine in each upper corner, 1995); Medel et al. (1991); Ramil and Vervoort aperture at the end of a cone. (1992a); Medel and López-González (1996); Medel Records from Mediterranean: western Mediter- and Vervoort (1998) spp. robusta. ranean, Adriatic. Known seasonality: 1, 2 5, 6, 7, 10. Diphasia delagei Billard, 1912 Reproduction: 1, 2, 7, 10. (Figs. 96A-C) Distribution: temperate and sub-tropical north- eastern Atlantic, Mediterranean. Colonies up to 23 mm high, growing on others References: Vervoort (1959) as D. pinaster; hydroids; hydrorhiza lineal, giving rise hydrocauli Teissier (1965) as D. pinaster; Cornelius (1979, alternately to oppositely arranged, erect and 1995) as D. pinaster; García et al. (1980); Ramil unbranched. Basal most internode of the axis athe- (1988); Gili, Vervoort and Pagés (1989); Ramil and cate, topped by oblique node; remainder internodes Vervoort (1992a); Boero and Bouillon (1993); thecates, nodes indistinct. Hydrothecae in opposite Medel and López-González (1996); Medel and Ver- pairs; tubular, elongated, adnate almost completely voort (1998); Schuchert (2001a). to the internode, distal portion curved outwards; adcauline wall of a pair not touching; rim with a Diphasia pinastrum (Cuvier, 1830) shallow adcauline sinus into which the circular oper- (Figs. 96H-L) culum is attached. Hydrotheca totally and finely ringed transversally; rings well marked and running Colonies robust, with erect and monosiphonic distally till close under hydrothecal rim; rings also hydrocauli and hydrocladia arranged pinnately, sec- visible on dorsal and frontal aspect of the internode. ondary branches may occurs; main stem thicker than Gonothecae (male = female ?) borne under a pair of hydrocladia. Hydrothecae on opposite pairs, both on hydrothecae, large, sack-shaped, disposed parallel to axis and hydrocladia, tubular sharply curved out- the axis, a major part of its dorsal wall in direct con- wards to form an angle of c. 90º with the axis, tact with the internode; narrowed and curved adcauline wall 2/3 adnate, abcauline wall with frontally distally, with a small circular aperture; the strong perisarcal peg or ledge at the lever of inflex- gonotheca is also densely transversally ribbed. ion; hydrothecal rim even, with a large adcauline Records from Mediterranean: only found at the embayment, aperture wide, operculum single, Strait of Gibraltar (Tarifa, Spain). attached to the adcauline sinus. Gonothecae male = Known seasonality: 7. female, borne on basis of hydrothecae, quadrangular Distribution: temperate and tropical eastern in cross section, shaped as an inverted pyramid, nar- Atlantic, Strait of Gibraltar. rowing towards basally; apically with four blunt References: Cornelius (1979; 1995); Ramil and cusps, circular aperture in the middle, at the end of a Vervoort (1992a); Medel (1996); Medel and López- cone; interior of each cusp with fine canal commu- González (1996); Medel and Vervoort (1998). nicating with small opening at top of cusp. Records from Mediterranean: Strait of Gibraltar Diphasia margareta (Hassall, 1841) and Alboràn Sea. (Figs. 96D-G) Known seasonality and reproduction: 6. Distribution: temperate eastern Atlantic and Stem erect, robust (up to ca 210 mm), monosi- Mediterranean. phonic and pinnately branched; nodes transverse; References: Patriti (1970); Cornelius (1979); main axis thicker than hydrocladia in older Ramil and Vervoort (1992a); Altuna (1994); Cor- colonies. Hydrothecae biseriated, opposite to sub- nelius (1995) as D. alata; Medel and Vervoort opposite on both stem and branches; at half their (1998). length sharply curving outwards, abcauline wall internally with perisarcal thickening in area of cur- Diphasia rosacea (Linnaeus, 1758) vature; adcauline wall 1/2-3/4 adnate; rim directed (Figs. 97A-D) upwards, with a large adcauline embayment where the circular operculum is attached. Female Colonies small (up to 50 mm) composed of erect gonotheca large, pyriform, with four longitudinal and monosiphonic hydrocauli with hydrocladia ribs bearing 1-3 spines; male smaller, quadrangular alternately arranged (with some secondary branch-

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ing); hydrocladia same width as stem. Axis and opposite pair of frontally placed hydrothecae. hydrocladia with internodes separated by oblique Hydrotheca tubular, basal half parallel with the axis, nodes, each with a pair of opposite to sub-opposite distal half curving outwards forming 45º with the hydrothecae. Hydrotheca tubular, gradually to rather axis; adcauline walls of each pairs of hydrothecae abruptly curved outwards, adcauline wall 1/2-1/3 1/2 – 2/3 touching frontally. Gonothecae almost adnate; aperture circular, rim even, with slight spherical, with rounded transverse ridges and trun- adcauline embayment, operculum circular, attached cate distally, aperture circular on a short collar; oper- to the inner side. Male gonotheca straight-sided, nar- culum with one valve circular. rowed basally, with 6-8 longitudinal ridges ending Records from Mediterranean: eastern and west- in blunt spines surrounding terminal cone and aper- ern Mediterranean, Adriatic ture. Female gonotheca tubular, narrowing towards Known seasonality: 1-12. basally, with 8 longitudinal ridges ending above and Reproduction: 2, 6-11. forming brood chamber; one opposite pair of spines Distribution: circumglobal, in subtropical and usually longer than remaining six and often notched tropical seas. on outer edge. References: Rossi (1961); Millard (1975) as D. Records from Mediterranean: only found at the cornicina; Boero and Fresi (1986); Calder (1991); Strait of Gibraltar. Boero and Bouillon (1993); Cornelius (1979); Known seasonality: 6, 7. Medel, García and García-Gómez (1991); Avian et Reproduction: 7. al. (1995); Medel and López-González (1996); Distribution: eastern and western Atlantic, Strait Medel and Vervoort (1998); Peña Cantero and Gar- of Gibraltar. cía Carrascosa (2002). References: Naumov (1960); Cornelius (1979, 1995); Ramil and Vervoort (1992a); Medel and Genus Hydrallmania Hincks, 1868 López-González (1996); Schuchert (2001a). Colonies erect, monosiphonic; hydrocaulus giv- Genus Dynamena Lamouroux, 1812 ing off spirally-arranged pinnate branches bearing alternate hydrocladia; hydrothecae sessile, partially Colonies erect, branched or unbranched, monosi- adnate, secondarily arranged along one side of phonic; hydrocaulus, and hydrocladia when present, hydrocladia and appearing uniseriate though slight- with hydrothecae in two longitudinal rows; ly inclined alternately to the left and right, contigu- hydrothecae tubular, sessile, partly to completely ous, in groups of 3-10; young colonies and occa- adnate, usually expending distally, in opposite to sional branches of mature ones with alternate and sub-opposite pairs, occasionally in groups of 2 or biseriate arrangement; hydrotheca with two margin- more pairs per internode; hydrothecal margin triden- al cusps often ill-defined or absent; operculum of tate; median adcauline tooth smaller and less con- two delicate flaps; retracted hydranth with abcauline spicuous than lateral teeth; operculum of 2 flaps, caecum; gonophores as solitary fixed sporosacs. adcauline one usually smaller than the abcauline and divided into two parts by a median line; some Hydrallmania falcata (Linnaeus, 1758) species with mantle (ectodermal lamella), with or (Figs. 97I-L) without distal batteries of large cnidocysts; gonophores as fixed sporosacs, planula often brood- Colonies long (up to 640 mm) but drooping when ed in an external acrosyst, gonothecae solitary. out of water, hydrocaulus monosiphonic, separated References: Calder (1991); Cornelius (1995); into athecate internodes by oblique nodes; hydrocla- Hirohito (1995); Schuchert (2001a, 2003). dia pinnately branched, borne on apophysis with axil- lary hydrothecae, alternately arranged in basal part of Dynamena disticha (Bosc, 1802) the axis and becoming helicoidal in upper parts; basal (Figs. 97E-H) most internode short and athecate, the remainders with three hydrothecae, one of which is axillary, and Hydrocauli erect, (up to ca 30 mm) monosiphon- apophysis supporting a secondary hydrocladium, ic, and unbranched. Axis athecate basally and ended these being alternate, in a same plane. Hydrothecae by oblique node; remainder internodes thecates with on primary and secondary hydrocladia in a single transverse nodes distinct or indistinct; each with an row, but alternately curved towards left and right

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sides of the axis (but alternate and in two rows in Known seasonality: 4, 5, 7, 8, 10. young colonies). Hydrotheca more or less tubular but Reproduction: 7, 8. widest basally, rim with two blunt lateral cusps bor- Distribution: tropical and subtropical Pacific and dering a large adcauline and a smaller abcauline Atlantic; also Indian Ocean, Mediterranean. sinus; operculum of two flaps. Gonothecae male = References: Gili (1986) as S. dubia; Roca female, ovate, aperture terminal, broad, circular. (1987); Boero and Bouillon (1993) also as S. Records from Mediterranean: only found at the dubia; Peña Cantero (1995); Medel et al. (1991); Strait of Gibraltar (in the west side). Medel and López-González (1996); Medel and Known seasonality: 6, 7. Vervoort (1998); Peña Cantero and García Carras- Reproduction: 7. cosa (2002). Distribution: mainly north Atlantic (western and eastern), but also records from South Africa (probably Genus Sertularella Gray, 1848 doubtful) and from N Pacific Ocean, Strait of Gibraltar. References: Naumov (1960); Cornelius (1979, Hydroid: colony erect, branched or unbranched, 1995); Ramil and Vervoort (1992a); Vervoort monosiphonic or polysiphonic; hydrocaulus and (1993a); Medel and López-González (1996); Medel hydrocladia, when present, with two longitudinal and Vervoort (1998); Schuchert (2001a). rows of alternate, sessile hydrothecae; hydrothecal margin with 4 teeth; submarginal teeth present or Genus Salacia Lamouroux, 1816 absent, operculum pyramidal, composed of 4 trian- gular valves; retracted hydranth with abcauline cae- Colonies erect, monosiphonic; hydrocladia, cum; gonophores as solitary fixed sporosacs, acro- when present, either opposite or alternate and of dif- cyst in some species. ferent structure than hydrocaulus, internodes being Remarks: the number of inner teeth may some- of irregular length; hydrothecae on hydrocaulus and times vary in the same colony; namely in S. miuren- hydrocladia, in 2 longitudinal rows, in opposite or sis, where they can vary from 0 to 5 (Hirohito, subopposite pairs, sessile, partly or completely 1995). Due to the great variability existing among adnate, without marginal cusps, hydrothecal aper- the species belonging to this genus, there are not ture triangular, operculum with single abcauline cir- “good” characters to separate the different species. cular flap; retracted hydranth without abcauline cae- In this key, we have included only the species con- cum; gonophores as solitary fixed sporosacs. sidered valid; a revision of the specific characters is References: Calder (1991); Hirohito (1995); needed in this genus. Schuchert (2003). References: Ramil, Parapar and Vervoort (1992); Vervoort (1993b) list; Hirohito (1995). Salacia desmoides (Torrey, 1902) (Figs. 98A-E) 1. Hydrotheca with intrathecal projections ...... 2 – Hydrotheca without intrathecal projections ..... 3 Hydrocauli erect (up to ca 75 mm), monosiphon- 2. Hydrothecal walls symmetrical, aperture more or ic, usually irregularly branched, hydrocladia similar less perpendicular to the hydrothecal axis ...... in structure with hydrocauli. Athecate basal part of ...... S. ellisii the axis of variable length, remainder thecates – Hydrothecal walls asymmetrical, aperture tilted internodes with one or two pairs of opposite upwards; usually abcauline marginal cusp hydrothecae; nodes oblique. Hydrothecae tubular, enlarged...... S. mediterranea straight at their bases and curved outwards distally, 3. Stem and hydrocladia dichotomously branched forming 90º with axis; adcauline walls of each pairs ...... S. crassicaulis. partially touching frontally; plane of aperture tilted – Stem pinnate or irregularly branched...... 4 to the basal part of the axis; rim almost circular, 4. Colonies pinnate, stiff and polysiphonic when operculum attached at the middle of abcauline part. adult; gonothecae often with 2 wide rounded Gonothecae barrel-shaped, with shallow transverse apical cusps ...... S. gayi grooves, gradually disappearing on distal part, with – Colonies irregularly branched, flexuous, a short collar and a wide circular aperture. monosiphonic or polysiphonic basally; Records from Mediterranean: eastern and west- gonothecae with 2-4 pointed narrow apical ern Mediterranean. cusps...... S. polyzonias

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Sertularella crassicaulis (Heller, 1868) Note: we consider that S. fusiformis Hincks, 1861 (Figs. 98F-I) and S. lagenoides Stechow, 1919 are conspecific of S. ellisii. Hydrocauli erect, polysiphonic basally, up to ca Records from Mediterranean: eastern and west- 60 mm, dichotomously branched in different planes; ern Mediterranean, Adriatic. hydrocauli and hydrocladia similar in structure; Seasonality: present all the year. internodes separated by oblique nodes alternately Reproduction: 2-12. sloping towards left or right side. Hydrothecae later- Distribution: mainly eastern Atlantic, but also ally to the axis, alternate, one per internode, cylin- records in western Atlantic and Pacific; Mediter- drical, almost as wide as long, adcauline wall 1/2 ranean. adnate to the internode; aperture directed to the References: Rossi (1961, 1971); Cornelius (1979, upper part of the axis. Gonothecae elongated, ovoid, 1995) as S. gaudichaudi ; Morri (1981); Gili with transverse undulations, apical distinct neck (1986); Gili et al. (1989); Ramil et al. (1992a); with three cusps. Boero and Bouillon (1993) as S. gaudichaudi ; Records from Mediterranean: western Mediter- Medel et al. (1991); Medel and López-González ranean, Adriatic. (1996); Medel and Vervoort (1998); Peña Cantero Seasonality: present all the year. and García Carrascosa (2002). Reproduction: 10-2, 4-5. Distribution: endemic of the Mediterranean Sea. Sertularella gayi (Lamouroux, 1821) References: Stechow (1919); Picard (1956b); (Figs. 99F-I, 100A) Gili (1982, 1986); Boero and Bouillon (1993); Medel et al. (1991); Avian et al. (1995); Medel and Well developed colonies with stems erect, poly- López-González (1996). siphonic and pinnate (up to ca 160 mm); secondary branches may be present; hydrorhiza strong, radial- Sertularella cylindritheca (Allman, 1888) ly ramified. Internodes thecates, separated by = Sertularelloides cylindritheca (Allman, 1888) oblique nodes alternatively directed to the left and the right. Hydrothecae present in the monosiphonic Sertularella ellisii parts of the hydrocaulus and hydrocladia; lateral, (Deshayes and Milne-Edwards, 1863) alternate; tubular, swollen basally and slightly nar- (Figs. 99A-E) rowed distally, usually with the margin tilted out- wards, in abcauline direction; approximately 1/2 of Hydrocauli erect, up so 50 mm high, monosi- the adcauline wall adnate to the internode; old phonic, irregularly branched; stem and hydrocladia hydrothecae many times with the abcauline wall with the same structure, divided into thecate intern- thickened; adcauline wall many times with trans- odes by oblique nodes alternatively directed to the verse undulations, more or less pronounced. left and the right. Hydrothecae lateral to the axis, Gonothecae elongated ovoid, distal half annulated; alternate, one per internode and in the same plane; aperture circular usually flanked by two cusps, typi- tubular, walls symmetrical, swollen in basal half and cally one larger than the other, but 3-4 cusps may narrowed in distal half; abcauline wall 1/3 adnate; occurs; colonies dioecious, with acrocyst external to aperture more or less perpendicular to the hydrothe- female gonothecae. cal length axis; 3-5 intrathecal projections more or Records from Mediterranean: western Mediter- less developed; when are 5, three are adcaulinar ranean. (one medium, in the same axis of the marginal cusp, Known seasonality: 1-10. and two laterals) and 2 are abcaulinar (lateral to the Reproduction: 1, 5, 9. cusps). Gonothecae ovoid, transversally undulated, Distribution: eastern Atlantic; Mediterranean. often smooth basally, neck with 3-4 apical cups. References: Vervoort (1959, 1966, 1972); Picard Great variability through the species and with inter- (1956b); Teissier (1965); Cornelius (1979, 1995); mediate forms; thus, the internodes may have sever- García-Corrales et al. (1980); Gili (1986); Gili et al. al weak annulations, aperture of hydrothecae in (1989); Medel et al. (1991); Ramil et al. (1992); some colonies are tilted in adcauline or abcauline Ramil and Vervoort (1992a); Boero and Bouillon direction and the walls of the hydrotheca may have (1993); Medel and López-González (1996); Medel transverse undulations. and Vervoort (1998); Schuchert (2001a).

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Sertularella mediterranea Hartlaub, 1901 ly, with 2-4 (usually 4) apical cusps; female (Figs. 100B-D) gonothecae with acrocyst. Records from Mediterranean: western Mediter- Hydrocauli erect (up to 23 mm high), monosi- ranean, Adriatic, Black Sea, Red Sea. phonic and irregularly branched; stem and hydrocla- Known seasonality: almost always present. dia divided into thecate internodes by oblique nodes Reproduction: 1-12. alternatively directed to the left and the right. Distribution: cosmopolitan. Hydrothecae tubular, displace laterally, alternate one References: Picard (1956b); Naumov (1960); per internode, 1/3-1/2 of the adcauline wall adnate; Rossi (1971); Millard (1975); Cornelius (1979, abcauline and adcauline walls not symmetrical, the 1995); Gili et al. (1989); Medel et al. (1991); Ramil first one usually more or less straight, enlarged dis- and Vervoort (1992); Ramil and Vervoort (1992a); tally in a pronounced marginal cusp; the second one, Boero and Bouillon (1993); Avian et al. (1995); swollen basally and narrowing distally; margin of Medel and López-González (1996); Medel and Ver- the hydrothecae tilted upwards in adcauline direc- voort (1998); Schuchert (2001a); Peña Cantero and tion; internal projections present, in the same García Carrascosa (2002). arrangement that in Sertularella ellisii. Great vari- ability throughout the species, the marginal Sertularella tenella (Alder, 1856) abcauline cusp may be not enlarged, and the aper- (Figs. 100J-K, 101A) ture of the hydrotheca may vary its orientation even inside of the same colony; the abcauline wall some- Hydrorhiza tortuous giving rise erect and mono- times undulated. Gonothecae elongated, ovoid, siphonic stems, usually unbranched (up to ca 20 transversally ringed, and narrowed distally, with 3-4 mm), variously zigzag. Hydrothecae alternate, walls apical cusps; with acrocyst external to female more or less symmetrical, usually with 3-6 annula- gonothecae. tions, sometimes slight or even absent; adcauline Records from Mediterranean: eastern and west- wall 1/4 adnate, rim 4 cusped, aperture perpendicu- ern Mediterranean, Adriatic lar to the longitudinal axis of the hydrotheca. Known seasonality and reproduction: always. Gonothecae oval, with 3-4 apical cusps and trans- Distribution: eastern Atlantic, Mediterranean. versally ribbed. References: Picard (1956b) as S. ellisi f. mediter- Records from Mediterranean: ? ranea; Millard (1975); Cornelius (1979, 1995) as S. Distribution: Northern Atlantic, Caribbean Sea; gaudichaudi; García-Corrales et al. (1980) as S. N Pacific Ocean. picta; Medel et al. (1991); Ramil and Vervoort References: Vervoort (1993a); Boero and Bouil- (1992a); Medel and López-González (1996); Medel lon (1993); Cornelius (1995); Medel and López- and Vervoort (1998); Peña Cantero and García Car- González (1996); Schuchert (2001a). rascosa (2002). Note: doubtful species, probably conspecific with Sertularella rugosa (Cornelius (1995). Sertularella polyzonias (Linnaeus, 1758) (Figs. 100E-I) Doubtful species

Colonies erect but flexuous, up to ca 70 mm, Sertularella cubica García-Corrales, Aguirre- main stem monosiphonic or polysiphonic basally, Inchaurbe and González-Mora, 1980 hydrocladia arranged irregularly, with some second (Fig. 101B) and third order branching. Thecate intenodes of hydrocauli and hydrocladia separated by oblique Colonies erect, monosiphonic, simple or branched nodes alternatively directed to the left and the right. (with one or two hydrocladia). Hydrocaulus divided Hydrothecae lateral, alternate, in the same plane, into internodes by oblique nodes. Hydrothecae alter- tubular, swollen basally and narrowed distally, walls nate, narrow at base, widening abruptly towards rim, usually thin, approximately. 1/2 adcauline wall with a circular section basally being slightly rectan- adnate; margin slightly tilted outwards or perpendic- gular distally; adcauline wall 1/3 adnate; rim large ular to the axis of the hydrotheca, internal projec- with 4 cusps separated by shallow incisions; three tions can be present, but this is incidental. Gonothe- intrathecal cusps reduced to absent in some hydrothe- cae elongated, horizontally ridged, narrowed distal- cae. Gonothecae not known.

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Records from Mediterranean: western Mediter- the axis; margin with two lateral cusps and a third ranean. smaller adcauline one, operculum with two valves, Distribution: not known. the adcauline smaller and folded in the middle. References: García-Corrales et al. (1980). Gonothecae arising from short pedicels, elongate- ovoid, to nearly spherical in cross section, smooth, Genus Sertularia Linnaeus, 1758 aperture nearly circular at the end of a short collar; operculum circular. Colonies erect, arborescent, pinnate or simple, Records from Mediterranean: eastern and west- monosiphonic; hydrothecae borne on stem and ern Mediterranean, Adriatic branches, sessile, partly adnate, oppositely or alter- Known seasonality: present all the year. nately in two longitudinal rows, hydrothecal margin Reproduction: 3, 4, 5, 7, 8. with two lateral cusps about midway of abcauline Distribution: temperate and tropical Atlantic, and adcauline edges and, in some species, a third Pacific and Indian Ocean; Mediterranean. median adcauline one; operculum non pyramidal, References: Rossi (1971); Millard (1975); Calder two-valved, adcauline valve smaller than abcauline; (1991) as Tridentata; Medel et al. (1991); Ramil and retracted hydranth with abcauline caecum, in some Vervoort (1992a); Boero and Bouillon (1993); Cor- species mantle or ectodermal lamella present, with nelius (1995) as Tridentata; Medel and López- or without distal batteries of large cnidocysts; González (1996); Medel and Vervoort (1998); Peña gonophore as fixed sporosacs, sometimes planula Cantero and García Carrascosa (2002). brooded in external acrocyst, exceptionally as swim- ming gonophores (Sertularia marginata). Sertularia marginata (Kirchenpauer, 1864) (Figs. 101H-K) 1. Hydrotheca with transverse perisarcal septum at the curvature of abcauline wall ...... 2 Hydrocauli monosiphonic, up to ca 25 mm, pin- – Hydrotheca without transverse septum ...... 3 nate when adult, unbranched when younger; straight 2. Adult colonies pinnate; internodes of the stem to geniculate in younger parts; all internodes the- with three hydrothecae, one most basal and two cates, except in the basal part of the colony and superior subopposite ...... S. marginata hydrocladia; nodes slightly oblique; axial internodes – Adult colonies unbranched; internodes of the with three hydrothecae (occasionally two), one stem with two opposite hydrothecae...... basal, axilary with the apophysis of the hydrocladi- ...... S. turbinata um, and two subopposite. Hydrocladial internodes 3. Colonies usually dichotomously branched, nodes with two hydrothecae opposite touching frontally; transverse and oblique; perisarc of the gonotheca tubular and curved outwards slightly frontally and smooth and without apical cusps...... S. distans obliquely upwards, forming 30º-90º with the axis of – Colonies usually unbranched, nodes oblique; the internode; adcauline wall 2/3 adnate, abcauline perisarc of the gonotheca with transverse ribs basally with a transverse line of perisarc to the level and four apical cusps ...... S. perpusilla of the elbow; margin with two lateral cusps, occa- sionally enlarged, and a third small adcaulinar; oper- Sertularia distans Lamouroux, 1816 culum with two valves, a larger semicircular (Figs. 101C-G) abcauline flap, and a smaller adcauline flap folded in the middle. Gonothecae large, drum-shaped, with Colonies erect, up to 40 mm high, monosiphonic transverse ribs and two rounded lateral spines some- and dichotomously branched, branches borne times very developed, aperture circular wide provid- frontally and dorsally to the axis; stem and branches ed of a circular operculum, releasing swimming divided into alternated athecates and thecates intern- gonophores. odes; the athecates with basal transversal node and Records from Mediterranean: western Mediter- distal oblique one, which constitute the basal node ranean. of several thecates internodes separated by more or Known seasonality: 4 9. less distinct transverse nodes. Hydrothecae arranged Distribution: tropical and subtropical Atlantic, in opposite pairs, usually separated frontally; tubular Pacific and Indian Ocean; Mediterranean. and curved outwards, forming 60º-90º with the axis; References: Patriti (1970); Millard (1975); Gar- narrowed distally; adcauline wall 1/3-1/2 adnate to cía-Corrales et al. (1980); Calder (1991) as Triden-

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tata; Medel et al. (1991); Boero and Bouillon References: Vervoort, (1959); Millard, (1975) (1993); Watson (1994); Medel and López-González Boero and Bouillon, (1993); Watson, (1994); Peña (1996); Medel and Vervoort (1998). Cantero, Svoboda and Vervoort (1997); Medel and Vervoort, (1998). Sertularia perpusilla Stechow, 1919 (Figs. 102A-B) Genus Thuiaria Fleming, 1828

Colonies erect, up to ca 7 mm, usually unbranched; Colonies pinnate, palmate or bottle-brush- internodes thecate excepting in basal parts, separated shaped; hydrocladia subopposite, alternate, or all by distinct or indistinct oblique nodes; hydrothecae around stem; hydrothecae on hydrocaulus and opposite, touching frontally, tubular and curved out- hydrocladia, cylindrical, broadened in lower part, wards, forming 80º-90º with the axis; adcauline wall narrowed toward aperture; partly or completely 1/2 adnate to the axis; margin with three cusps, two adnate or totally sunk in cladia, hydrothecal rim laterals and one abcauline; operculum with two usually circular (except in T. gonorhiza, where it is valves. Gonothecae elongated-ovoid, with transverse sinuous), hydrothecal operculum of a single ribs and four small apical cusps. abcauline attached flap; hydrothecae multiseriate, Records from Mediterranean: eastern and west- on hydrocaulus in two opposite, subopposite or ern Mediterranean, Adriatic. alternate longitudinal rows, (except in a few species Known seasonality: present all the year. like: T. arctica, with 4 longitudinal rows, and T. Reproduction: 3-9. zachsi, with 6 to 8 longitudinal rows) falling in the Distribution: Mediterranean. same plane, on hydrocladia, with a similar distribu- References: Gili (1982, 1986); Boero and Fresi tion to hydrocauli or as verticils formed by three or (1986); Roca (1987); Boero and Bouillon (1993); more hydrothecae, verticils alternately crossing in Avian et al. (1995); Medel and López-González right angles, the number of longitudinal rows of (1996); Peña Cantero and García Carrascosa (2002). hydrothecae being so twice the number of hydrothecae (up to 13 rows recorded); retracted Sertularia turbinata (Lamouroux, 1816) hydranth with abcauline caecum; gonophores as (Figs. 102C-E) fixed solitary sporosacs, in many species female ones forming a marsupium (acrocyst), in other Hydrocauli monosiphonic, up 10-16 mm high, species female ones with distal spines forming an unbranched, basal portion with one to several athecate external brood chamber (pseudomarsupium), internodes separated of the remainder thecate ones by gonothecae on hydrocauli and hydrocladia, inserted an oblique hinge-joint; nodes oblique, distinct or directly under a hydrotheca. indistinct. Hydrothecae opposite, one pair per intern- ode, usually contiguous frontally and separated at the Thuiara thuja (Linnaeus, 1758) back; tubular and curved outwards, adcauline wall (Figs. 102F-J) 1/2-3/4 adnate to the axis, abcauline wall convex basally; perisarc of the hydrothecae thickened near the Main stem unbranched, slightly zigzag, dark margin, internal surface of abcauline wall with a ridge brown to black, often lacking hydrocladia in basal of perisarc at elbow; hydrothecal aperture facing out- 1/3-3/4, in nature colonies up to 50-250 mm high, wards to obliquely upwards, margin with two large with hydrocladia all around stem, in form of bottle pointed lateral cusps and smaller median adcauline bush; hydrocladia usually dichotomous, pale horn cusp; operculum of two valves, a larger abcauline one coloured, inserted close together, forked 2-4 times, and a smaller adcauline flap folded in the middle. ending bluntly; young colonies pinnate; hydrothecae Hydranth with an abcauline diverticulum. Gonothecae only on hydrocladia, alternate in two rows (rarely barrel-shaped, with transverse ribs and with a wide three) entirely sunk within hydrocladia, cylindrical distal aperture. below, tapering above; operculum circular attached Records from Mediterranean: western Mediter- on lower side; gonothecae male = female, egg- ranean. shaped, inverted-conical smooth to slightly rugose, Seasonality: ? tapering below and more sharply above, aperture Distribution: Warmer parts of Atlantic, Pacific circular, often a short collar, no pedicel, acrocyst in and Indian Ocean, Mediterranean. female.

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Records from Mediterranean: the record of this part. Hydrothecae lateral and opposite, one to two species in the Mediterranean by Naumov (1969) pairs per internode, cylindrical, distal part curving needs confirmation. outwards; adcauline wall 2/3 adnate to the axis; rim Seasonality: ? even, circular, renovation of the margin very fre- Distribution: Atlantic, Pacific, Mediterranean? quent. Gonothecae borne on the aperture of the References: Naumov (1969); Cornelius (1995); hydrotheca, fusiform, pointed apically, with deep Peña Cantero, Svoboda and Vervoort (1997). transversal ridges. Records from Mediterranean: western Mediter- Family SYNTHECIIDAE ranean, Adriatic. Marktanner-Turneretscher, 1890 Known seasonality: present throughout all the year. Colonies erect, unbranched or with pinnately Reproduction: 6, 7, 10, 11. arranged hydrocladia, arising from a creeping Distribution: eastern Atlantic (Strait of Gibraltar hydrorhiza, commonly monopodial with terminal and Canary Islands), Mediterranean. growing points, hydrothecae sessile, bilaterally sym- References: Gili (1982, 1986); Roca metrical, in two or more longitudinal rows on hydo- (1986,1989); Izquierdo et al. (1986); Boero and caulus and hydrocladia, alternate or opposite, partly Fresi (1986); Ramil and Vervoort (1992a); Boero adnate, no real diaphragm but with a definite basal and Bouillon (1993); Avian et al. (1995); Medel and floor perforated by a distinct hydropore, hydrothecal López-González (1996); Peña Cantero and García rim unthooted, operculum and nematophores absent; Carrascosa (2002). gonophore as fixed sporosacs, gonothecae arising from within hydrothecal cavity or from fenestrae Family TECLAIIDAE Bouillon, Pages, below hydrothecae or from hydrorhiza. Gili, Palanques, Puig and Heussner 2000 Remarks: following Broch (1918) the hydrotheca of the Syntheciidae is lined by an ectodermal lamel- Leptomedusae with 4 simple radial canals; with la and the hydranths should possess an abcauline hollow tentacles; with 4 simple lips; with «gonads» caecum (Synthecium hians) but those characters elongated forming linear sacs on radial canals, sepa- have not been verified for all the species. rated from manubrium; with one to three cordyliform References: Calder (1991); Watson (2000); structure between successive tentacles; without ocel- Schuchert (2003). li; without cirri; with or without open stotocyst.

Genus Synthecium Allman, 1872 1. Medusae with open statocysts...... Parateclaia – Medusae without statocysts...... Teclaia Colonies erect, branched or unbranched, mono- or polysiphonic; hydrocaulus bearing hydrocladia Genus Parateclaia Bouillon, Pages, Gili, usually in opposite pairs to subopposite pairs form- Palanques, Puig and S. Heussner 2000 ing two longitudinal rows; two longitudinal rows of opposite to subopposite sessile hydrothecae on Medusa: Teclaiidae with open statocyst. hydrocaulus and hydrocladia, usually tubular, partly Hydroid: unknown. adnate, margin entire; without operculum; hydranths with abcauline caecum in some species; gonophores Parateclaia euromarge Bouillon, Pages, Gili, as solitary fixed sporosacs, gonothecae generally Palanques, Puig and S. Heussner 2000 dioeciuos arising from within hydrothecal cavity. (Figs. 103A-B)

Synthecium evansi (Ellis and Solander, 1786) Medusa: umbrella 6.0 mm wide, 4.5 mm high; (Figs. 102K-L) somewhat flatter than hemispherical; mesoglea fair- ly thick at the apex, thinning towards umbrella mar- Colonies erect, pinnate and monosiphonic, up to gin; exumbrella sprinkled with cnidocysts; velum 100 mm high; thick perisarc in old colonies; hydro- narrow; manubrium short, square, with large base, cladia opposite, in the same plane. Stem and hydro- about 1/4 of subumbrella cavity height and 1/3 of cladia divided into thecate internodes by distinct or umbrella cavity width without gastric peduncle, indistinct transverse nodes, except in the most basal colour light brown; mouth with 4 simple groove-

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shaped lips, white in colour; as long as manubrium pedicellate in the same colony, or sessile but adnate height; with 4 simple radial canals not meeting in only at diaphragm level (?); hydrothecal margin the centre of the manubrial roof, circular canal nar- either entire or with 2 to 4 teeth; operculum of one, row; up to 24 hollow marginal tentacles; with elon- 3 or 4 valves and either persistant or shed early; gated conical marginal bulbs each with two large annular perisarcal diaphragm usually present; brown bands; «gonads» elongated, cylindrical hydranths with mantle (ectodermal lamella) and a extending along the middle 2/3 of the radial canals basal annular ectodermal fold; cnidome: microbasic and living both ends free; up to three cordyliform and macrobasic mastigophores; gonophores as fixed conical structures, each with central brown pigment sporosacs. spots and terminal cnidocysts; one to two open sta- Remarks: Calder (1991) considered that the pres- tocysts between successive marginal tentacles. ence of an ectodermic lamina or mantle lining the Records from Mediterranean: western Mediter- interior of the hydrotheca could be diagnostic of the ranean. Thyroscophidae but this structure is polyphyletic Known seasonality: 12. being also present in some Aglaopheniidae and Distribution: endemic of Mediterranean Sea. amongst the Sertulariidae, for instance in some References: Gili et al. (2000), Dynamena, Sertularella and Sertularia, and so is not Hydroid: unknown. a convenient family or generic character (see also Cnidoscyphus below). We concur, however, with Genus Teclaia Gili, Bouillon, Pagès, Calder that the presence of an ectodermal annular Palanques and Puig, 1998 ectodermal fold is, at the state of our knowledge about hydranth structure, a good diagnostic charac- Medusa: Teclaiidae without statocyst. ter for the delimitation of the Thyroscyphidae. The Hydroid: unknown. genera with an abcauline caecum previously includ- ed in this family are considered here as belonging to Teclaia recincolae Gili, Bouillon, Pagès, the Sertulariidae. Palanques, and Puig, 1998 (Figs. 103C-F) 1. Hydrotheca pedicellate...... Thyroscyphus – Hydrotheca sessile ...... Sertularelloides Medusa: umbrella 6 mm wide, 4 mm high, a lit- tle flatter than hemispherical, mesoglea rather thick Genus Sertularelloides Leloup, 1937 in the apical region; manubrium square, flat, 1/4 subumbrellar cavity height, 1/3 umbrella width; Hydroid: colony erect, simple, monosiphonic, mouth with 4 groove-shaped simple lips; 4 radial arising from a strong ramified, reticulate hydrorhiza; canal and circular canal narrow; «gonads» elongat- hydrocauli monosiphonic, split in slender internodes ed, linear, half to three-quarters length of radial with a hydrotheca near distal end; hydrocladia alter- canals, close to manubrium, up to 26 marginal ten- nate in the same plane and with same structure than tacles; marginal tentacular bulbs elongated, cylindri- the hydrocauli, arising immediately under a cauline cal; 1-2 cordyliform structures between successive hydrotheca; hydrothecae large, cylindrical, alternate, tentacles, no cirri, no ocelli. sessile or on renovate apophyses in old colonies, Records from Mediterranean: western Mediter- adcauline adnate portion much reduced; hydrothecal ranean. rim quadrangular, with 4 teeth separated by shallow Known seasonality: 5. embayments; operculum with 4 low flaps, which do Distribution: endemic of Mediterranean Sea. not close the aperture of the hydrotheca, diaphragm References: Gili et al. (1998). present; hydranth with a basal annular ectodermal Hydroid: unknown. fold; gonophores as fixed solitary sporosacs, gonothecae larger than hydrothecae, arising just Family THYROSCYPHIDAE Stechow, 1920 below a hydrotheca, pedicellate, elongate and quad- rangular apex with 4 marginal cusps. Colonies stolonal or erect, arising from a creep- Remarks: Sertularella mercatoris Leloup, 1937 ing hydrorhiza, commonly monopodial, with termi- the type and only species of this genus, is conspe- nal growing points; hydrothecae radially to bilater- cific with the nominal species Sertularella cylin- ally symmetrical, pedicellate, or both sessile and dritheca Allman, 1888. Microscopical examination

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of the type material of Sertularelloides and of spec- roscyphus has no generic diagnostic value and imens of Sertularella cylindritheca from the “Insti- Cnidoscyphus is thus kept here as congeneric with tut Royal des Sciences naturelles de Belgique” Thyroscyphus. shows the presence of an annular membrane, already described in the latter species by Vervoort Thyroscyphus fruticosus (Esper, 1793) (1959). For this reason we follow here Vervoort (Figs. 104D-H) (1959) and Calder, (1991), in considering this species a member of the Thyroscyphidae. Stem stiff and woody, monosiphonic, giving of References: Calder (1991); Medel et al. (1991); irregularly alternate hydrocladia predominantly in Ramil and Vervoort (1992a); Migotto (1996); Medel one plane, reaching 150 mm, no division into nodes, and Vervoort (1998); Watson (2000). segmentation visible on smaller branches only, branches not in zigzag; two rows of hydrothecae Sertullaroides cylindritheca (Allman, 1888) strictly alternate on opposite side of stem and (Fig. 103G-I, 104A-C) branches, pedicel short, thick, smooth or with one or two constrictions, borne on a wide apophysis, nor- With the characters of the genus. mally demarcated from hydrotheca by a shallow Records from Mediterranean: western Mediter- groove on abcauline side; hydrotheca tubular, not ranean. expanding to margin, curved outwards, with Known seasonality: 5-8. adcauline wall convex and abcauline wall straight or Reproduction: 7. slightly concave; hydrothecal margin with four low, Distribution: western and eastern Atlantic (sub- rounded teeth and thickened ridge just below edge; tropical and tropical waters); Mediterranean. operculum of four equal triangular valves, shed References: as Sertularella cylindritheca: Ver- early; diaphragm in form of thickened perisarcal voort (1959, 1968); Patriti (1970); García-Corrales ring; more powerfully developed on adcauline side; et al. (1980); Gili et al. (1989); Ramil and Vervoort hydranth with a basal annular ectodermal fold; (1992a); Boero and Bouillon (1993); Medel et al. gonothecae arising from stem apophysis, below (1991); Medel and López-González (1996); Medel hydrotheca, female wider and shorter than male, and Vervoort (1998). obliquely truncated distally contening one egg which develop in planula in situ. Genus Thyroscyphus Allman, 1877 Records from Mediterranean: western Mediter- = Cnidoscyphus Splettstösser, 1929 ranean. Seasonality: ? Colonies erect, branched, monosiphonic or poly- Distribution: Indo-Pacific; Mediterranean. siphonic; hydrothecae large, pedicellate, cone- Reference: Vervoort (1967); Millard (1975); Watson shaped, campanulate, to nearly cylindrical, alter- (2000). nately arranged on opposite side of hydrocaulus and hydrocladia; hydrothecal adcauline wall usually Family TIARANNIDAE Russell, 1940 more protuberant than abcauline wall; margin entire or with 4 teeth; diaphragm present; operculum of Colonies erect or stolonal, of “Stegopoma” type; one or 4 valves either shed early or persistent; hydrotheca pedicellate or sessile, deep, asymmetric- hydranth with mantle (ectodermal lamella) and tubular; operculum formed by two pleated mem- basal annular ectodermal fold, with or without distal branes which meet one another like a gabled roof, batteries of large cnidocysts, abcauline caecum with straight ridges above and on the sides of absent; gonophores as fixed sporosacs. hydrotheca, continuing up at each end, thus all Remarks: Cnidoscyphus was included by Millard imparting a bilateral symmetry to the distal part of (1975), Bouillon (1985) and Calder (1991) in the hydrotheca; gonophores as free medusae or fixed genus Thyroscyphus. Vervoort (1993b), Medel and sporosacs, gonothecae usually resembling hydrothe- Vervoort, (1998) nevertheless, retained the genus cae, but larger. Cnidoscyphus for the species having large cnido- Medusa: no apical projection; no gastric pedun- cysts in the distal part of the mantle or ectodermal cle; manubrium wide, cross-shaped, with 4 perradi- lamella; this character being also found in some al pouches joined to subumbrella; mouth with 4 sim- Dynamena, Sertularia, Symmetroscyphus and Thy- ple or crenulated lips; 4 simple radial canals;

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“gonads” folded on interradial walls of manubrium longitudinally; 4 perradial and 4 interradial margin- and/or on perradial manubrial pouches; marginal al tentacles; marginal tentacular bulbs conical; 3-6 tentacles numerous, hollow; hollow cordyli-like small marginal cirrus-like tentacles between each structures bearing cnidocysts; no ocelli. pair of marginal tentacles; no statocysts nor ocelli References: Pagès et al. (1991; 1992); Bouillon seen. (1999); Bouillon and Barnett (1999); Bouillon and Hydroid: unknown. Boero (2000). Records from Mediterranean: western Mediter- ranean; Adriatic Sea. Key to polyps Known seasonality: 5, 8, 10. Distribution: Atlantic; Mediterranean. 1. Colonies stolonal ...... Modeeria References: Kramp (1961); Russell (1957, – Colonies erect ...... Stegopoma 1970a); Goy (1973b); Schmidt and Benovic (1977); Benovic and Bender (1987); Boero and Bouillon Key to medusae (1993); Benovic and Lucic (1996); Gili et al. (1998).

1. «Gonads» on perradial manubrial pouches only, Krampella tardenti Gili, Bouillon and Pagès, 1998 widely split longitudinally ...... Krampella (Figs. 105A-C) – «Gonads» on manubrium and perradial gastric pouches, in regular transverse folds ... Modeeria Medusa: umbrella 4.5 mm wide, 4 mm high, almost hemispherical, with a slightly conical or Genus Krampella Russell, 1957 rounded apex, mesoglea of uniform thickness; manubrium large, 2/3 of bell height, with quadrate Tiarannidae medusa with 4 perradial manubrial base, with 4 broad and long perradial pouches pouches extending almost to circular canal; extending almost till umbrella margin, manubrium «gonads» not sac-like nor folded on radial pouches, walls with 4 interradial bands of brown pigments; widely separated longitudinally; 8 marginal tenta- mouth quadrate, with 4 simple lips; radial canals cles; up to five cirrus like tentaculae between suc- very short, linking the most distal parts of manubri- cessive marginal tentacles. al pouches to ring canal; no tissue strands linking Hydroid: unknown. radial canals or manubrial pouches to exumbrella ; 8 «gonads» oval to bean-shaped along the most distal 1. With fine strands of tissue connecting walls of third of the manubrial perradial pouches, widely radial canals and manubrial pouches with separated longitudinally; 4 perradial and 4 interradi- exumbrellar surface; «gonads» elongated...... al marginal tentacles; marginal tentacular bulbs con- ...... K. dubia ical; 3 (2-4) long, solid cirrus like spirally coiled – Without fine strands of tissue connecting walls of tentaculae between successive tentacles; no stato- radial canals and manubrial pouches with cysts nor ocelli seen. exumbrellar surface; «gonads» oval to Hydroid: unknown. bean-shaped...... K. tardenti Records from Mediterranean: Antikhytira Strait, eastern Mediterranean. Krampella dubia Russell, 1957 Known seasonality: 6. (Figs. 104I-J) Distribution: endemic of Mediterranean Sea. References: Gili et al. (1998). Medusa: umbrella 4 mm high, 4.5 mm wide, hemispherical, mesoglea moderately thick; Genus Modeeria Forbes, 1848 manubrium with large base, quadrate, with four per- radial pouches extending along all length of radial Hydroid: colonies stolonal. Hydrotheca pedicel canals; 4 radial canals, very short, linking the most late, deep and tubular, with margin produced on two distal parts of manubrial pouches to ring canal; sides. Operculum of two longitudinally pleated about sixteen fine strands of tissue connecting walls membranes seated in the embayment of the margin of radial canals and manubrial pouches with exum- and meeting one another like a gable. No brellar surface; «gonads» elongated, along distal 2/3 diaphragm, no nematothecae, no intertentacular of perradial manubrial pouches, widely separated web; gonothecae similar to hydrothecae.

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Medusa: with «gonads» transversally folded on Genus Stegopoma Levinsen, 1893 interradial walls of manubrium and extending out- wards along the perradial pouches. Tiarannidae with pleated hydrothecal operculum in form of gabled roof, hydranth lacking intertentac- Modeeria rotunda (Quoy and Gaimard, 1827) ular web, gonotheca resembling hydrotheca but (Figs. 105D-K) larger. Remark: All species with a Stegopoma hydroid Colonies stolonal; hydrothecae arising singly and with medusa buds are referable to the genus from hydrorhiza at irregular intervals, large, tubular, Modeeria; the genus Stegopoma is here kept for the tapering below into a smooth, straight or slightly species with fixed sporosacs; all the species with curved, non annulated pedicel; hydrothecal aperture unknown gonophores should be considered as closed by an operculum formed by two pleated Tiarannidae incertae sedis. membranes which meet one another like a gabled roof, with straight ridges above and sides of Stegopoma bathyale Vervoort, 1966 hydrotheca continuing up at each end, the all impart- (Figs. 106A-C) ing a bilateral symmetry to the distal part of the hydrotheca; with a very thin diaphragm often Colonies big, about 100 mm high, of sympodial destroyed by preservation; hydranth not extending structure; hydrocauli strongly polysiphonic, thick, far beyond hydrothecal aperture; up to 13 filiform axis usually forked; branching irregular but in the tentacles in a single unicoronate whorl, no basal same plane. Monosiphonic parts divided into weak- intertentacular membranous web, hypostome round- ly geniculate or slightly undulate internodes, each ed-conical; gonothecae resembling hydrothecae topped by a pedicelate hydrotheca, following intern- with gabled operculum, but larger, pedicel reported- ode arising basally to the hydrotheca. Perisarc thick ly short to non existent; gonophore with up to 4 on axis and in nodes but fairly abruptly thinning out developing medusae. on pedicel. Hydrotheca similar to those of Modeeria Medusa: umbrella 20 mm wide, somewhat less rotunda, but a trifle more bulky, slightly curved out- high, hemispherical, mesoglea very thick, with wards; hydrothecal pedicels wrinkled or indistinctly rounded apex; manubrium short, broad, cruciform, ringed, hydrothecal walls very thin. Branches perradial edges of manubrium connected over entire becoming rapidly covered by secondary tubules, length with subumbrella, forming 4 perradial pouch- axillary hydrotheca remaining free; branch es; mouth with 4 large, slightly crenulated lips; 4 rebranching repeatedly. Gonophores as fixed radial canals, straight, smooth, entering middle of sporosacs? Gonothecae borne on stem and branches, manubrium to form the perradial pouches, narrow elongated, tubular, apparently produced by one of circular canal; «gonads» in regular transverse folds secondary tubules, completely adnate with branch or on interradial walls of manubrium, extending out- axis and covered by net of anastomosing tubules; wards on perradial pouches; 16-28 hollow marginal aperture apical and circular; it is unknown if they tentacles with large conical marginal bulbs; 1-3 (4) produce free medusae or not. minute cordyli-like appendages with distal bundle Records from Mediterranean: only records from of cnidocysts between successive tentacles; the area of the Strait of Gibraltar (off Cádiz). cnidome microbasic euryteles. Distribution: temperate and subtropical eastern Records from Mediterranean: western Mediter- Atlantic (from deep waters), Strait of Gibraltar. ranean, Adriatic. References: Vervoort (1966); Ramil and Vervoort Known seasonality: 4, 6. (1992a); Medel and López-González (1996). Distribution: Atlantic; Indo-Pacific; Antarctic; Arctic; Mediterranean. Family TIAROPSIDAE References: Kramp (1961); Edwards (1963a, Boero, Bouillon and Danovaro, 1987 1973b); Ramil and Vervoort (1992a); Alvarez (1993a); Altuna (1994); Avian et al. (1995); Cor- Hydroid: colony “Cuspidella” like; hydrotheca nelius (1995); Mills et al. (1996); Stepanjants et al. tubular, sessile or with reduced pedicel; operculum (1997); Brinckmann-Voss and Arai (1998); Gili et of numerous flaps demarcated or not from the rest of al. (1998); Peña Cantero and García Carrascosa hydrotheca by a crease line; gonophores as free (2002). medusae, gonotheca tubular or rounded, laterally

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compressed, operculate or not, with short peduncle, compound sense organs; with two kind of tentacles; growing singly from hydrorhiza. without marginal cirri. Medusa: 4 or 8 radial canals (exceptionally up to 16); one or two types of marginal tentacles (long and Tiaropsidium mediterraneum (Metschnikoff, rudimentary, both with marginal bulbs); sense 1886a) organs compound, comprising an ecto-endodermal (Figs. 106G-I) ocellus and an open velar statocyst. References: Boero, Bouillon and Danovaro Hydroid: colonies stolonal; hydrothecae tubular, (1987); Pagès et al. (1992); Bouillon (1999); with short, wavy or straight annulated hydroclade, Bouillon and Barnett (1999); Bouillon and Boero operculum with 7-10 flaps with broad base and (2000). pointed apex, meeting centrally and sharply demar- cated from the hydrothecal margin; hydranth com- 1. With numerous (50-60) compound sense organs; pletely retractable in the hydrothecae; with one mouth with eight lips ...... Octogonade whorl of amphicoronate tentacles; no intertentacular – With 8 or 16 (exceptionally 48) compound sense membranous basal web; gonothecae borne on organs; mouth with four lips...... Tiaropsidium hydrorhiza, large, pyriform, almost not pedunculate and developed in one plane. Genus Octogonade Zoja, 1896 Medusa: umbrella 7 mm wide, 5 mm high, mesoglea thick; manubrium short, fairly broad; Tiaropsidae medusae with 8 radial canals; mouth mouth with four short, simple lips; 4 radial canals with 8 lips; with numerous compound statocysts; and circular canal narrow; 2 opposite, long, perradi- with two kinds of tentacles; without marginal cirri. al tentacles, and 2 small perradial bulbs; with five Hydroid: unknown. rudimentary tentacles in each quadrant, smaller than the marginal bulbs; «gonads» elongated, on distal Octogonade mediterranea Zoja, 1896 2/3 of the radial canals; eight compound sense (Figs. 106D-F) organs. Records from Mediterranean: western and cen- Medusa: umbrella 60-70 mm, globular, with tral Mediterranean. bulging sides, mesoglea thick; velum fairly broad; Known seasonality: 1, 2, 12. manubrium small, tubular, octagonal; with 8 small Distribution: endemic of Mediterranean Mediter- but distinct lips; «gonads» linear, along almost ranean. entire length of the 8 radial canals, living a short part References: Hadzi (1915); Huvé (1956); Kramp free at both ends; 16 long marginal tentacles and (1961); Picard (1958b); Boero, Bouillon and Don- 150-160 small rudimentary tentacles, containing avaro (1987); Boero and Bouillon (1993). diverticula from the circular canal; 50- 60 com- pound sense organs. Order PROBOSCOIDA Broch, 1910 Records from Mediterranean: western Mediter- ranean; Adriatic Sea. Hydroid: hydranths with a complex, flared to Known seasonality: 2, 4, 6-12. globose, more or less pedunculate hypostome, form- Distribution: endemic of Mediterranean Sea. ing a “buccal cavity” beneath the mouth. References: Zoja (1896); Kramp (1961); Picard Medusa: varied in expression, with closed stato- (1958b); Boero and Bouillon (1993); Avian et al. cysts; never with cordyli, open statocysts, excretory (1995); Benovic and Lucic (1996) pores, cirri or ocelli.

Genus Tiaropsidium Torrey, 1909 Key to hydroids (see family characteristics)

Hydroid: colonies of “Cuspidella” type; opercu- Key to medusae lum formed by several flaps sharply demarcated from the hydothecal margin; gonothecae rounded, 1. Without permanent tenon-like rudimentary compressed laterally, without operculum. marginal bulbs...... Campanulariidae Medusa: with 4 or more (up to 16) simple radial – With triangular, tenon-like permanent canals; mouth with four lips; with 8 or 16 (rarely 48) rudimentary marginal bulbs...... Phialuciidae

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Family CAMPANULARIIDAE Johnston, 1836 panularia, Tulpa and Campanularia could be merged without great difficulty. Hydroid: colony erect or stolonal; hydrothecae bell-shaped or campanulate, radially or, secondarily, Key to hydroids bilaterally symmetrical; generally pedicellate, rim cusped or not, with basal diaphragm or inward annu- 1. Colony usually stolonal or with short unbranched lar projection of perisarc; hydranth generally tubu- uprights...... 2 lar, with flared or globose hypostome delimiting a – Colony with erect stems, bearing alternate “buccal cavity”, gastric endoderm of uniform struc- hydrothecae ...... 4 ture; hydrothecal spherules present or not; 2. Hydrotheca with true diaphragm, with free gonophores as free medusae, eumedusoids or medusae ...... Clytia sporosacs, in gonothecae. – Hydrotheca without true diaphragm; with Medusa: manubrium short; no gastric peduncle; annular perisarcal thickening near base ...... 3 4 radial canals (except in Gastroblasta and Pseudo- 3. Hydrothecal walls with unthickened perisarc; clytia); with or without velum (without in Obelia); gonophores as fixed sporosac ..... Campanularia “gonads” completely surrounding radial canals, sep- – Pydrothecal walls with perisarc variably arated from manubrium; tentacles hollow (except in thickened; gonophores as eumedusoids ...... Obelia where they are solid and with a short prolon- ...... Orthopyxis gation of endoderm into bell mesoglea); with or 4. Gonophores released as free medusae ...... 5 without tenon-like rudimentary bulbs; no cirri, – Gonophores not released as free medusae ...... 7 excretory papillae or pores; numerous (16-200) 5. Medusa with solid marginal tentacles; no velum closed, velar, marginal statocysts (8 in Obelia, each (see key below)...... Obelia situated on underside of the basal bulb of some mar- – Medusa with hollow tentacles and velum...... 5 ginal tentacle); no ocelli. (Fig. 7: 3) 6. Medusa with one manubrium...... Clytia References: Nutting (1915); Russell (1963b); – Medusa with more than one manubrium ...... García Corrales et al. (1978); Östman (1983); ...... Gastroblasta Calder (1991); Pagès et al. (1992); Cornelius 7. Gonophores forming degenerate medusae, (1995); Hirohito (1995); Boero et al. (1996); Migot- meconidia ...... Gonothyraea to (1996); Bouillon (1999); Bouillon and Barnett – Gonophores as fixed sporosacs or degenerate (1999); Bouillon and Boero (2000); Medel and Ver- medusae...... 8 voort (2000). 8. Stem typically monosiphonic ...... Laomedea Remarks: the classification of the Campanulari- – Stem polysiphonic already early in life...... idae is unsatisfactory; generic divisions, as in many ...... Hartlaubella other families of Leptomedusae hydroids, are not well defined, and vary even in modern works (see: Key to medusa Calder 1991, Cornelius 1982; 1995; Hirohito 1995). Hirohito (1995), for instance, taking in account 1. With more than four radial canals...... 2 some morphological characters such as presence – With normally four radial canals...... 3 and absence of diaphragm, presence or absence of 2. With up to 20 radial and centripetal canals; with sub-hydrothecal spherules, treated Orthopyxis and numerous manubria each with 4 lips ...... Rhizocaulus as Campanularia, and Laomedea and ...... Gastroblasta Gonothyraea as Obelia so simplifying greatly the – With up to seven radial canals; with one generic contents of the family. But Obelia is a very manubrium and as many lips than radial canals . different from the other Campanulariidae genera at ...... Pseudoclytia the medusa level and the reduction of free medusae 3. With reduced medusae; without manubrium; to fixed gonophores may have occurred several without tentacles...... Orthopyxis times independently during the evolution of the – With normally developed medusae; with one Campanulariidae and so it is impossible to refer manubrium with 4 lips; with tentacles...... 4 presently the taxa with fixed sporosacs to any 4. With hollow marginal tentacles and normal presently known medusa genus. Nevertheless many velum = Clytia genera are very close to each other for instance: – With solid marginal tentacles; without velum..... Hartlaubella and Lameodea, Rhyzocaulus and Cam- ...... Obelia

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Genus Campanularia Lamarck, 1816 Campanularia raridentata Alder, 1862 (Fig. 107G) Colonies stolonal, seldom erect and branched; hydrorhiza not anastomosing; hydrothecal pedicel Colonies stolonal, composed of erect pedicels unbranched; hydrothecae campanulate or bell-shaped, each supporting a hydrotheca, perisarc of pedicels with entire or cusped margin, demarcated from pedi- smooth, ringed basally and below hydrothecae. cel basally by a variably developed annular perisarcal Hydrotheca cylindrical, sub-hydrothecal spherule thickening; hydrothecal walls with unthickened peris- present, rim with 6-8 wide rounded triangular cusps. arc, not abruptly everted distally; true diaphragm Gonothecae usually borne on stolons from short and absent, sub-hydrothecal spherule present; gonophores ringed pedicels, barrel-shaped, smooth and with cir- as fixed sporosacs, gonothecae on hydrorhiza. cular distal apertures. References: Calder (1991); Cornelius (1995); Records from Mediterranean: western Mediter- Schuchert (2001). ranean. Known seasonality: 4, 5, 6. 1. Length of the hydrotheca > 500 mm, with lines Distribution: northeastern Atlantic. running down from rim; cusps castellate; References: Gili and Castelló (1985) as Clytia gonotheca truncate distally, aperture wide...... hemispherica raridentata; Gili and García-Rubíes ...... C. hincksii (1985); Gili (1986); Llobet (1987); Llobet et al. – Length of the hydrotheca < 500 mm, without (1991); Medel and López-González (1996). lines; cusps pointed; gonotheca with a narrow Remarks: Campanularia raridentata described aperture at the end of a neck of variable length.. by Hincks, 1868 was referred to Clytia hemisphaer- ...... C. volubilis ica by several authors such as Vervoort (1968) or Cornelius (1982). Llobet (1987) showed, in her Campanularia hincksii Alder, 1856 drawings, hydrothecae without diaphragm, but with (Figs. 107A-F) annular thickening and gonothecae smooth and bar- rel-shaped. We agree with the author o.c., that Colonies up to 15 mm high, composed of stolon Hincks, 1868 described something similar in C. with erect and unbranched pedicels bearing a single hemispherica; the same occurs with Gili (1986). The hydrotheca at the top. Perisarc of the pedicels record of Campanularia raridentata, Alder, 1862 by smooth to sinuous, usually with several annuli Llobet (1987) is here considered as doubtful. basally and with a characteristic spherule below hydrothecae. Hydrothecae cylindrical, sides parallel, Campanularia volubilis (Linnaeus, 1758) clearly longer than wider, rim castellate, 8-15 cusps (Figs. 107H-M) either truncate, notched or distinctly bicuspidate, distal half of hydrothecae usually slightly polygonal Stolonal colonies up to 3-4 mm high, with erect on cross section, surface with longitudinal striae; pedicels each with a single hydrotheca, arising at basal diaphragm thick, conspicuous. Gonothecae irregular intervals from the hydrorhiza. Pedicels borne on stolon, male and female similar, cylindri- smooth to spirally annulated throughout. Hydrothe- cal, perisarc smooth or irregularly undulated, trun- cae with sub-hydrothecal spherule, rim with 10-12 cated apically, with operculum circular; planula shallow bluntly pointed cusps, fine longitudinal stri- brooded within the female gonotheca ae running to the cusps may be present. Male and Records from Mediterranean: eastern and west- female gonothecae similar, usually borne on stolon, ern Mediterranean; Adriatic, Black Sea. flask shaped, smooth, aperture narrow at the end of Known seasonality: 1-12. neck of indefinite length, absent when young. Plan- Reproduction: 1-12. ula as dispersal stage. Distribution: almost cosmopolitan, avoiding Records from Mediterranean: western Mediter- pure Arctic and Antarctic. ranean. References: Millard (1975); Cornelius (1982, 1995); Distribution: NE Atlantic, eastern Pacific, Gili (1986); Calder (1991); Boero and Bouillon (1993); Mediterranean. Avian et al. (1995); Medel and López-González (1996); References: Aguirrezabalaga et al. (1986); Cor- Medel and Vervoort (2000); Schuchert (2001a); Peña nelius and Ryland (1990); Boero and Bouillon Cantero and García Carrascosa (2002). (1993); Cornelius (1995); Medel and López-

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González (1996); Schuchert (2001a); Peña Cantero – «Gonads» thick; without blastostyles ...... 2 and García Carrascosa (2002). 2. Manubrium, «gonads» and marginal bulbs bright green ...... C. viridicans Genus Clytia Lamouroux, 1812 – Manubrium, «gonads» and marginal bulbs transparent or of different colour ...... 3 Hydroid: colony reptant, unbranched stolonal or 3. «Gonads» voluminous along almost whole erect branched, usually minute, monosiphonic or length of radial canals ...... 4 polysiphonic; hydrorhiza branched but not anasto- – «Gonads» linear or oval, along maximum 1/3 of mosing; hydrothecae deep, campanulate, hydrothe- the length of radial canals nearer to margin than cal rim sinuous or deeply indented, with clefts to manubrium ...... 5 between round to sharply-pointed cusps; true 4. With 16 marginal tentacles; usually 3 statocysts hydrothecal diaphragm; subhydrothecal spherule between successive marginal tentacles ...... absent (present in C. hummelincki); gonophores as ...... C. discoida free medusae, gonotheca conical. – With 24-36 marginal tentacles; one statocysts Medusa: manubrium short; velum normal; mar- between successive tentacles...... C. macrogonia ginal tentacles hollow; no tenon-like permanent 5. With oval «gonads»; 16 marginal tentacles; rudimentary bulbs; numerous statocysts. umbrella up to 6-8 mm wide...... C. gracilis Remarks: very few species of Clytia medusae are – With linear «gonads»...... 6 clearly identified, most morphological characters used 6. Up to 32 marginal tentacles and more than 16 to distinguish them possibly falling in the range of statocysts in adults, umbrella up to 20 mm wide variation that can be expected in a single species and ...... C. hemisphaerica having little or no taxonomic value. Most of the Clytia – No more than 16 marginal tentacles and 16 species described hereunder are only known by their statocysts in adults, umbrella 6 mm wide ...... hydroids stage and should be considered as incertae ...... C. noliformis sedis. The genus needs a careful revision, with careful elucidation of life cycles and molecular work. Clytia discoida (Mayer, 1900) Reference: Pagliara et al. (2000). (Fig. 108A)

Key for Hydroid Medusa: umbrella 4 mm wide, almost hemi- spherical; manubrium urn-shaped, with bulging 1. Hydrothecal cusps projecting inwards and with sides, mouth with four recurved lips; 16 short mar- outwards perisarc projections in bays between ginal tentacles with large basal bulbs; usually three nearby cusps ...... C. viridicans statocysts between tentacles; gonads on greater part – Hydrothecal cusps different ...... 2 of radial canals , thick, cylindrical, eggs very large. 2. Hydrothecal cusps oblique ...... C. gracilis. Hydroid: unknown. – Hydrothecal cusps upright...... 3 Records from Mediterranean: western Mediter- 3. Hydrothecal cusps with characteristic ranean. longitudinal perisarcal ridge...... C. linearis Seasonality: ? – Hydrothecal cusps without any perisarcal ridge Distribution: Atlantic, Mediterranean ...... 4 References: Kramp (1959a, 1961); Bouillon and 4. Hydrothecal cusps usually bicuspidate, Boero (2000). hydrotheca cylindrical, deep ...... C. paulensis – Hydrothecal cusps not bicuspidate, hydrotheca Clytia gracilis (M. Sars, 1850) campanulate, not deep...... 5 (Figs. 108B-G) 5. Hydrothecal diaphragm thin .... C. hemispherica 5. Hydrothecal diaphragm thick...... C. noliformis Hydroid: colonies delicate, up to 20 mm high, comprising a creeping hydrorhiza from which arise Key to medusa several erect hydrocauli, some forking 2-3 times, with long internodes and pedicels; hydrothecae 1. «Gonads» small in the middle of the radial canals deep-campanulate, with 8-12 large pointed cusps and giving rise to numerous blastostyles carrying inclined to one side, diaphragm thin, pedicel base medusa buds ...... C. mccradyi incurving; 1-ca 25 annuli at internodes and pedicel

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base; hydranth about 7 times as long than broad Medusa: umbrella up to 20 mm wide, nearly when fully extended, with typically 18-20 tentacles; hemispherical or flatter, mesoglea fairly thin; gonothecae arising from hydrorhiza on short slender manubrium small, quadrate, with small base; mouth pedicels, long, urn-shaped, constricted abruptly always with 4 simple lips; «gonads» oval or linear below rim and below this more gradually, smooth 1/2-3/4 of length of radial canals without median walled, wide mouthed; planktonic colonies have furrow, nearer to margin than to manubrium; usual- been described in Atlantic waters. ly 4 straight radial canals (sometimes more, up to Medusa: umbrella up to 8 mm wide, nearly hemi- 12); typically 32 (16-58) marginal tentacles; mar- spherical, mesoglea thin; manubrium small quadrate ginal tentacular bulbs globular, prominent; few par- to cruciform; mouth with 4 simple lips; 4 straight tially developed marginal bulbs; velum narrow; 1-3 radial canals; «gonads» oval to round, with few usually 2 statocysts between successive tentacles. eggs, along the third distal quarter of the radial Records from Mediterranean: eastern and west- canals; up to 16 marginal tentacles; marginal bulbs ern Mediterranean; Adriatic. with spherical base; 1-2 statocysts between succes- Known seasonality: 1-12. sive tentacles. This medusa is often confound with Reproduction: 1-12. other Clytia medusae mainly with C. hemisphaeri- Distribution: Atlantic; Indo-Pacific; Mediter- ca, the discrimination between those different ranean. species may perhaps be possible by the use cnido- References: Trégouboff (1957); Roosen-Runge cysts microstructure (Östman, 1979, 1983). (1970); Goy (1973b); Gili (1986); Benovic and Ben- Records from Mediterranean: hydroid found in der (1987); Calder (1991); Goy et al. (1988, 1990, eastern and western Mediterranean and Adriatic. 1991); Cornelius (1982, 1995); Boero and Bouillon Known seasonality: 4-8, 10, 11. (1993); Avian et al. (1995); Benovic and Lucic Reproduction: 6-9. (1996); Mills et al. (1996); Medel and López- Distribution: Atlantic; Indo-Pacific; Mediter- González (1996); Medel and Vervoort (2000); ranean for the hydroid stage. Atlantic for the plank- Schuchert (2001a); Peña Cantero and García Carras- tonic colonies. cosa (2002). References: Kramp (1961); Cornelius and Öst- man (1986); Calder (1991); Boero and Bouillon Clytia hummelincki (Leloup, 1935) (1993); Vervoort (1993a); Avian et al. (1995); Cor- (Figs. 109A-E) nelius (1995); Medel and López-González (1996); Medel and Vervoort (2000); Schuchert (2001a); Hydroid: colonies stolonal, up to 4.5 mm high, Peña Cantero and García Carrascosa (2002). with a creeping hydrorhiza. Pedicels long, relatively thick, annulated basally and with occasional groups Clytia hemisphaerica (Linnaeus, 1767) of annuli elsewhere; distal end of pedicel with slight (Figs. 108H-K) swelling just beneath a subhydrothecal spherule. Hydrotheca shallow, cup-shaped, hydrothecal walls Hydroid: colonies usually stolonal but occasion- with relatively thin perisarc; margin smooth, occa- ally erect, arising from a creeping hydrorhiza; sionally oblique; diaphragm thin, slightly oblique, hydrothecal pedicels borne at close intervals, some- basal chamber shallow. times forking; hydrothecae campanulate, rim with Medusa: only immature medusa known. ca 8-14 broad rounded-triangular cusps; diaphragm Records from Mediterranean: Ionian coast of thin; pedicels straight, with one to several rings top southern Italy. and bottom and in some specimens also centrally; Records outside the Mediterranean: eastern and some pedicels with secondary pedicels, these having western Atlantic. characteristic upward curved basal region; References: Millard (1975); Cornelius (1982) as hydranths 3-4 times as long than broad when fully Laomedea; Calder (1991); Boero et al. (1997b). extended, with usual 24-30 tentacles; gonothecae arising from hydrorhiza on short, slender pedicels, Clytia linearis (Thorneley, 1899) tubular, typically with deeply concertinared walls (Figs. 109F-I) resembling a Chinese lantern, but gonothecal walls may be smooth in some specimens, wide mouthed Hydroid: colonies reptant, up to 40 mm high, (Calder, 1988; Cornelius, 1995). bearing erect pedicels unbranched or subsympodial-

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ly branched; pedicels and branches ringed basally Records from Mediterranean: eastern and west- and distally, topped by hydrothecae; branches aris- ern Mediterranean. ing laterally, at the upper part of the axis; hydrothe- Known seasonality: 7-10. cae very deep, cylindrical, sides almost parallel, nar- Distribution: Atlantic; Indo-Pacific; Mediter- rowing basally, with a thin diaphragm, straight or ranean. slightly oblique; margin wide, 10-12 acute cusps References: Brooks (1888); Kramp (1961); Goy with characteristic longitudinal central perisarcal (1970, 1972); Cornelius (1982); Bouillon et al. (1986); band or ridge extended further of the cusps. Benovic and Bender (1987); Brinckmann-Voss (1987); Gonothecae usually axillar, borne on short and Goy et al. (1991); Boero and Bouillon (1993); Carré et ringed pedicels, elongate-oval, truncate distally, nar- al. (1995); Benovic and Lucic (1996). row sub-distally and basally; enclosing up to eight developing medusa buds. Clytia macrogonia Bouillon, 1984 Medusa: only juvenile medusa just released (Fig. 109K) known. Records from Mediterranean: eastern and west- Medusa: umbrella 4 mm wide, discoidal; manubri- ern Mediterranean, Adriatic. um small, cruciform, with rounded perradial lobes; Known seasonality and reproduction: throughout mouth with 4 simple lips; 4 radial canals and circular the year. canal narrow; «gonads» cylindrical, along almost Distribution: tropical and subtropical waters of whole length of radial canals, females with few (about Atlantic, Pacific and Indian Ocean, Mediterranean. 20) very large eggs; with 24- 36 short marginal tenta- References: Rossi (1961); Marinopoulos (1979); cles; marginal tentacular bulbs large, globular; with Millard (1975); García-Corrales et al. (1978); Gili one statocyst between successive tentacles. and García-Rubíes (1985); Boero and Fresi (1986); Records from Mediterranean: eastern Mediter- Cornelius (1987); Calder (1991); Ramil and Ver- ranean. voort (1992a); Boero and Bouillon (1993); Altuna Seasonality: ? Prados (1995); Avian et al. (1995); Migotto, 1996; Distribution: Indo-Pacific, Mediterranean. Medel and López-González (1996); Medel and Ver- References: Kramp (1961); Bouillon (1984); Goy voort (2000); Peña Cantero and García Carrascosa et al. (1991); Boero and Bouillon (1993). (2002). Hydroid: unknown.

Clytia maccradyi (Brooks, 1888) Clytia noliformis auct. (McCrady, 1859) (Fig. 109J) (Figs. 110A-E)

Hydroid: Brooks (1888) saw young medusae Hydroid: colonies stolonal with creeping released from a hydroid colony and identified them hydrorhiza; pedicel strongly annulated basally and as C. mccradyi medusae. Brook’s description of the distally; hydrothecae campanulate, margin with hydroid did not differ from that of C. hemisphaerica about 13-15 blunt, broadly triangular teeth; with a (see Cornelius 1982, Carré et al., 1995). Mayer thick diaphragm; basal chamber shallow, subspheri- (1910) doubted Brook’s observation; the hydroid cal; hydranth with about 25-30 filiform tentacles; phase of this medusae is thus still not known with gonothecae laterally flattened, arising from certitude. hydrorhiza, on short annulated stalks. Medusa: umbrella 15 mm wide, about twice as Medusa: umbrella 6 mm wide, 3 mm high, flatter broad than high; mesoglea of soft consistence; than a hemisphere; manubrium tubular; mouth manubrium short and stout; mouth with four quadrate, with four simple lips; 4 radial canals; 16 recurved lips; sexual development by four small, marginal tentacles; 16 intervening statocysts; swollen, «gonads», situated in the middle part of the «gonads» elongated, on the distal third or fourth of radial canals, asexual reproduction through hydroid the radial canals, female «gonads» bearing 20-35 blastostyles giving rise to medusae buds and origi- large ova. The newly hatched medusa of Clytia nating at the same place than «gonads» and instead noliformis differs from corresponding stages of C. them in sexually immature specimens; 16- 24 mar- hemiphaerica by complete absence of «gonads». ginal tentacles; marginal tentacular bulbs conical; 1- Records from Mediterranean: western Mediter- 2 statocysts between tentacles. ranean, Adriatic.

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Known seasonality: 1-5, 7-12. Medusa: not known from nature. Umbrella flat- Distribution: Atlantic; Indo-Pacific; Mediter- tened, about 11 mm wide, exumbrella transparent, ranean. mesoglea thin; manubrium bottle-shaped on a short References: Picard (1949); Brian and Pérès peduncle; mouth with four corrugated lips, 16-32 (1953); Vannucci and Ribeiro (1955); Vannucci marginal tentacles,; 24-40 statocysts; «gonads» oval (1957); Kramp (1961); Berhaut (1970); Gili (1986); elongated along the distal part of radial canals not Calder (1991); Llobet et al. (1991); Boero and reaching umbrellar margin; manubrium, «gonads» Bouillon (1993); Avian et al. (1995). and tentacular bulbs bright green in living material. Records from Mediterranean: western Mediter- Clytia paulensis (Vanhöffen, 1910) ranean. (Figs. 110F-J) Seasonality: ? Distribution: endemic of Mediterranean Sea. Hydroid: colonies with erect and delicate smooth References: Haeckel (1864); Metschnikoff pedicels, ringed basally and below hydrothecae (1886a,b); Russell (1953); Cornelius (1982); (sometimes also centrally), usually unbranched, Pagliara et al. (2000). each supporting a hydrotheca. Hydrotheca cylindri- cal, deep, with a thin diaphragm at base; rim with 7- Genus Gastroblasta Keller 1883 11 cusps usually bicuspidate and rounded. Hydranth provided with 16-22 tentacles. Gonotheca cylindri- Medusa: Campanulariidae with several cal, probably male similar than female, tapering manubria; with up to 20 radial and centripetal gradually below and slightly above, smooth, borne canals; with normal velum; with hollow marginal on stolon on short and ringed pedicels. tentacles; without tenon-like permanent rudimentary Medusa: undescribed, pre-release medusa with 4 bulbs; with numerous statocysts. tentacle buds. Hydroid: Clytia-like, living embedded in Records from Mediterranean: eastern and west- sponges, gonophores on hydrorhiza. ern Mediterranean. Known seasonality: 4-9. Gastroblasta raffaelei Lang, 1886 Reproduction: 4, 5, 7, 8. (Figs. 110M, N) Distribution: cosmopolitan. References: Millard (1975); Marinopoulos Hydroid: see above. (1979); Cornelius (1982); Boero and Fresi (1986); Medusa: umbrella up to 6 mm wide, more or less Calder (1991); Cornelius and Ryland (1990); Ramil elliptical; with up to 20 radial and centripetal canals; and Vervoort (1992a); Boero and Bouillon (1993); up to 9 complete and 7 rudimentary urn-shaped Cornelius (1995); Medel and López-González manubria, each with four simple lips; «gonads» (1996); Medel and Vervoort (2000); Peña Cantero sometimes developed in the middle parts of on one and García Carrascosa (2002). or more radial canals; with 26 well developed mar- ginal tentacles and 17 rudimentary ones; 34 margin- Clytia viridicans (Leuckart, 1856) al statocysts. Reproduction by fission; perhaps a (Figs. 110K-L) variety of Clytia hemisphaerica (see Russell, 1953; Cornelius, 1982). Hydroid: colonies stolonal, growing on algae; Records from Mediterranean: western Mediter- pedicel short, annulated at base and below hydrothe- ranean; Black Sea. ca; hydrotheca conical, with 7-9 cusps, projecting Known seasonality: 7-10. inwards and with outwards perisarc projections in Distribution: endemic of Mediterranean Sea. bays between nearby cusps; hydranths with pedun- References: Lang (1886); Kramp (1959a, 1965); culate hypostome and 14-18 amphicoronate tenta- Vannucci (1966); Cornelius (1982). cles, the ones oriented downwards laying on the perisarc projections between adjacent cusps, the Genus Gonothyraea Allman, 1864 ones oriented upwards being sustained by cusps; gonophores as free medusa; gonothecae on Colonies erect, branched or unbranched, monosi- hydrorhiza either corrugated or smooth, containing phonic or polysiphonic; stem divided into regular up to four developing green medusae. internodes bearing alternate hydrothecae; hydrothecae

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campanulate to bell-shaped, radially symmetrical; Hartlaubella gelatinosa (Pallas, 1766) hydrothecal rim cusped; with true diaphragm; (Figs. 111F-J) gonophores forming degenerate medusae (mecodonia), extruded from gonotheca but remaining attached while Well developed colonies bushy, main stem erect, planula develops in a sac-like mecodonium with mar- up to 200 mm, branched, thick and polysiphonic. ginal tentacles, but no mouth or sense organs; gonothe- Final branches monosiphonic, alternate on both ca urn-shaped, pedicellate axillary on stem. sides of the axis, tending to be disposed in right Reference: Cornelius (1995). angle pairs, more or less dichotomously branched and flexuose. Internodes basally ringed, nearly Gonothyraea loveni (Allman, 1859) straight to curved. Hydrothecae borne on ringed (Fig. 111A-E) pedicels, small, cylindrical, rim often abraded smooth but firstly castellate, 12-14 blunt cusps each Hydrocauli erect, up to 100 mm, flexuous, mono- with a central notch of varied depth, gaps between siphonic, internodes straight to strongly curved, rounded; diaphragm transverse. Gonothecae (male somewhat irregularly branched and ringed basally. and female similar) cylindrical, borne on ringed Hydrothecae borne distally on the internodes, alter- pedicels, narrower basally, wider distally, circular nate, hydrothecal pedicels usually annulated aperture on a short collar. throughout; hydrothecae bell-shaped, deep, rim del- Records from Mediterranean: western Mediter- icate with 6-12 castellate cusps provided with a ranean, Black Sea. minute notch; diaphragm straight. Hydranth with Distribution: northeastern Atlantic, western 19-33 tentacles. Gonothecae long, cylindrical, nar- Atlantic and Indo-Pacific (New Zealand); Mediter- rowing basally, borne on ringed pedicels; medusoids ranean. develop internally and, when ripe, dangle in groups References: Cornelius (1982, 1995); Cornelius of 2-3 at entrance to gonotheca; medusoids roughly and Ryland (1990); Boero and Bouillon (1993). spherical, with 4-8 long, irregularly held tentacles, a circular canal, without mouth neither sense organs; Genus Laomedea Lamouroux, 1812 males with about 5 marginal tentacles; females with 8 marginal tentacles and 3-5 eggs which are fertil- Colonies erect, monosiphonic, branched or ized and develop into planulae in situ. unbranched, growing on branched but not anasto- Records from Mediterranean: western Mediter- mosing hydrorhiza; hydrocauli divided in regular ranean, Adriatic. internodes bearing alternate hydrothecae; hydrothe- Known seasonality: 4, 7-9. ca campanulate, rim even or cusped, radially sym- Reproduction: 4, 9. metrical, on pedicels, with true diaphragm; Distribution: eastern and western Atlantic, Indo- gonophores as fixed sporosacs, gonothecae sessile Pacific and Arctic Ocean, Mediterranean. or shortly pedicellate stolonal or axillary. References: Millard (1975); Östman (1979); Gili References: Östman (1982); Cornelius (1995). (1982, 1986); Isasi and Sáiz (1986); Boero and Bouillon (1993); Altuna (1994); Avian et al. (1995); 1. Colonies monosiphonic or bisiphonic...... 2 Cornelius (1995); Medel and López-González – Colonies polysiphonic ...... L. pseudodichotoma (1996); Schuchert (2001a). 2. Female gonotheca with a characteristic sub- terminal introverted curving tubular aperture ..... Genus Hartlaubella Poche, 1914 ...... L. calceolifera – Female gonotheca without this character...... 3 Colonies erect, polysiphonic, branched or 3. Internodes long, usually rigidly straight, in unbranched, growing on branched but not anastomos- zigzag...... L. angulata ing hydrorhiza; hydrocauli divided in regular intern- – Internodes slightly curved or flexuose...... 4 odes bearing alternate hydrothecae; hydrothecae 4. Rim of the hydrotheca smooth ...... L. flexuosa campanulate with castellated, often abraded rim, radi- – Rim of the hydrotheca bimucronate...... ally symmetrical, on pedicels, with true diaphragm; ...... L. neglecta gonophores as fixed sporosacs with large embryos, gonothecae axillary, inverted conical. Laomedea angulata Hincks, 1861 Reference: Cornelius (1995). (Figs. 111K-P)

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Colonies up to 15 mm high, composed of erect, Altuna (1994); Avian et al. (1995); Medel and López- flexuose, monosiphonic and unbranched stems, González (1996); Medel and Vervoort (2000). markedly zigzag, growing on an almost straight, lit- tle branched or unbranched stolon. Internodes dis- Laomedea flexuosa Alder, 1857 tinctly straight, forming angle 90º-120º between (Figs. 112G-M) them, ringed basally; when present, tendril stolons recurved at the tip. Hydro thecae borne on ringed Colonies up to 30 mm high, comprising erect, pedicels, bell-shaped, delicate, rim even more often branched or unbranched and flexuose stems grow- flared distally, diaphragm usually transverse, deli- ing on a branching stolon. Internodes usually curved cate to thickened specially at the extremes. and ringed basally. Hydrothecal pedicels slightly Gonothecae growing on stolons, borne on ringed narrower distally, ringed throughout, although pedicels; female ovate, aperture apical and wide, smooth central portion may occurs, pedicels lateral- planulae developed inside; male also ovate, but api- ly to the axis, alternate to the left and right. cal aperture narrower, with several gonophores. Hydrothecae bell-shaped, walls strong, sometimes Hydranth with 16-28 tentacles. thickened, rim even, diaphragms transverse. Female Records from Mediterranean: eastern and west- gonotheca borne on ringed pedicel, cylindrical, ern Mediterranean, Adriatic. elongated, narrower basally, distally truncate, aper- Known seasonality: 1, 2, 9. ture distal and wide; male gonotheca shorter, rough- Reproduction: 9. ly ovated, also with a circular and apical aperture Distribution: northeastern Atlantic (Europe), but narrower than female. Mediterranean. Records from Mediterranean: western Mediter- References: Gili (1982, 1986); Cornelius (1982, ranean, Adriatic. 1995); Ramil (1988); Boero and Bouillon (1993); Known seasonality: 4, 5, 8. Reproduction: 4. Avian et al. (1995); Medel and López-González (1996). Distribution: western and eastern Atlantic, Mediterranean. Laomedea calceolifera (Hincks, 1871) References: Cornelius (1982, 1995); Gili (1982, (Figs. 112A-F) 1986); García-Carrascosa et al. (1987); Ramil (1988); Boero and Bouillon (1993); Alvarez (1993); Colonies up to 30 mm high, comprising erect and Altuna (1994); Medel and López-González (1996); monosiphonic stems usually unbranched, growing Schuchert (2001a). on smooth but tortuous stolons. Axis flexuose, internodes slightly curved, separated by several Laomedea neglecta Alder, 1856 annuli at their base. Hydrothecae at the upper part of (Figs. 113A-D) the internodes, lateral and alternate to the left and the right, borne on pedicels with several annuli, Colonies delicate with monosiphonic or bisi- sometimes with smooth central portions; hydrothe- phonic stems; internodes long and narrow, often cae deep, bell-shaped, margin even and flared dis- wider in the middle than at ends, 3-10 rings basally, tally; diaphragm transverse to oblique. Male and curved to almost straight; each sharply inturned female gonothecae dissimilar when mature, female basally. Hydrothecae on long tapering distally club-shaped, with sub-terminal introverted curving pedicels with up to 20 annuli; delicate, walls tubular aperture on one side; male cylindrical, elon- unthickened and cylindrical; diaphragm oblique to gate, narrower basally and truncate distally, aperture transverse; rim usually bimucronate. Gonotheca terminal, central, at the end of introverted tube. male similar to female, cylindrical to inverted-coni- Records from Mediterranean: western and east- cal, truncate above. Acrocyst in female, eggs or ern Mediterranean, Adriatic, Black Sea. embryos possibly extruded singly. Known seasonality: 1, 4-7, 10. Records from Mediterranean: Adriatic. Reproduction: 1, 5, 7, 10. Known seasonality: 4-10. Distribution: eastern and western Atlantic (main- Reproduction: 4-10. ly northern parts), Mediterranean. Distribution: northeastern Atlantic, Mediter- References: Vervoort (1968); Marinopoulos (1979); ranean. Cornelius (1982, 1995); Gili (1986); Boero and Fresi References: Vervoort (1946); Cornelius (1995); (1986); Ramil (1988); Boero and Bouillon (1993); Schuchert (2001a).

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Laomedea pseudodichotoma Vervoort, 1959 Remarks: various nominal species of Obelia (Figs. 113E-H) hydroids are common throughout the world but the medusae specimens of this genus cannot be reliably Hydrorhiza composed of a tangle mass of peris- determined down to species level. The following arcal tubules, giving rise erect, polysiphonic and nominal species have been cited from Mediter- branched stems up to 50 mm high; branches with ranean: Obelia bidentata Clarke, 1875; Obelia secondary ramifications. In monosiphonic parts, dichotoma (L., 1758); Obelia fimbriata (Dalyell, stem slightly geniculate, internodes separated by 2- 1848); Obelia geniculata (L.1758); Obelia longissi- 3 annuli. Hydrothecae borne laterally at the extreme ma (Pallas, 1766) their medusa are undiscernable of each segment, hydrothecal pedicel oblique, on and are designed under Obelia spp. (Figs. 114A-B). distinct apophysis, with 4-8 annulations; hydrotheca According to Zamponi and Genzano (1990 a), the elongated conical, rim even and slightly everted; medusae of Obelia dichotoma Hincks, 1868 and diaphragm at basal part oblique. Male gonotheca Obelia longissima (Pallas, 1766), could be distin- sac-shaped and truncated distally; the female thin, guishable by their cnidome composed by atrichous elongated and narrowing distally. isorhizas, atrichous anisorhizas and basitrichous Remark: Cornelius, 1982 pointed out that the isorhizas in O. dichotoma and by microbasic gonophores could be free heteromedusoids. mastigophores and macrobasic mastigophores in O. Records from Mediterranean: western Mediter- longissima. The presence of macrobasic mastigo- ranean (Alborán Sea and Chafarinas Islands). phores appears nevertheless improbable in the genus Known seasonality: 1-8. Obelia although they have been found in other Lep- Reproduction: 1-7. tomedusae. Östman (1982) has found by electron Distribution: temperate and tropical eastern microscopy minute differences in the cnidocyst fine Atlantic; Mediterranean. morphology of newly liberated medusae O. References: Vervoort (1959, 1966); Cornelius dichotoma, O. longissima and O. geniculata. (1982, 1995); Ramil and Vervoort (1992a); Peña Records from Mediterranean: eastern and west- Cantero (1995); Medel and López-González (1996); ern Mediterranean, Adriatic Sea. Medel and Vervoort (2000); Peña Cantero and Gar- Known seasonality: 1-12. cía Carrascosa (2002). Distribution: cosmopolitan genus. References: Kramp (1961); Goy (1973b); Bouil- Genus Obelia Péron and Lesueur, 1810 lon (1984b); Fulton et al. (1985); Gili (1986); Cor- nelius (1975a, 1987, 1990, 1995); Benovic and Ben- Hydroid: colonies erect, branched or unbranched, der (1987); Brinckmann-Voss (1987); Zamponi and monosiphonic or polysiphonic, variably flexuose; Genzano (1990 b); Pagès et al. (1992); Boero and stolons not anastomosing; internodes annulated Bouillon (1993); Benovic and Lucic (1996); Medel proximally, supporting distally a pedicellate and López-González (1996). hydrothecae on apophysis; hydrotheca bell-shaped to campanulate, radially symmetrical, margin Key to the hydroid cusped or uncusped, true hydrothecal diaphragm, no sub-hydrothecal spherule; hydranth with globose 1. Hydrothecal rim with bimucronate cusps hypostome forming a “buccal cavity”; gonophores (embayments sometimes uniform) ...... as free medusae, gonothecae inverted conical, usual- ...... O. bidentata ly with raised terminal aperture but sometimes sim- – Hydrothecal rim smooth or with shallow cusps.. ply truncated...... 2 Medusa: umbrella 2.5- 6 mm wide, circular, flat, 2. Perisarc of internodes thickened, usually one side mesoglea very thin; without gastric peduncle; mouth thicker than the other one; hydrothecal pedicel with 4 simple lips; 4 radial canals; «gonads» spher- short, perisarc of hydrotheca thickened, rim ical to ovoid, sac-like, hanging from middle to end smooth ...... O. geniculata of the radial canals; numerous short, stiff solid, not – Without these characters ...... 3 extensile marginal tentacles; tentacles with short 3. Colony very long, flexible, stem brown to black; endodermal roots extending into bell mesoglea; 8 in older colonies side branches ceasing growth at statocysts situated on underside of basal bulbs of roughly uniform length but gradually shorter some marginal tentacles. towards growing tip ...... O. longissima

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– Colony loosely fan-shaped, stem pale to mid- Records from Mediterranean: eastern and west- brown, never black; sides branches typically ern Mediterranean, Adriatic. irregular in length ...... O. dichotoma Known seasonality: present all the year. Reproduction: all the year. Obelia bidentata Clarke, 1875 Distribution: cosmopolitan. (Figs. 113I-M) References: Millard (1975); Cornelius (1975, 1982, 1995); Gili (1982, 1986); Calder (1991); Ramil Hydroid: well developed colonies up to 350 mm and Vervoort (1992a); Boero and Bouillon (1993); high, comprising polysiphonic although slender Avian et al. (1995); Medel and López-González main stems, from which, lateral branches, roughly in (1996); Medel and Vervoort (2000); Schuchert right-angles pairs are given on both sides. Branches (2001a); Peña Cantero and García Carrascosa (2002). flexuose, giving alternately secondary branches with alternate branchlets provided with hydrothecal Obelia geniculata (Linnaeus, 1758) pedicels at nodes; third, even fourth, order ramifica- (Figs. 114H-I, 115A-E) tion may occur. Internodes long, ringed basally; hydrothecal pedicels originated distally, alternate, Hydroid: colonies erect, usually unbranched, ringed throughout or with smooth central portion. monosiphonic up to about 20 mm; stems markedly Hydrotheca almost cylindrical, elongated, often flexuose, internodes curved, thickened (more evi- slightly asymmetric, rim with bimucronate cusps, dent in older parts), usually one side thicker than the but embayments sometimes uniform. Female and other one and alternate towards the internodes, male gonothecae equal, usually inverted-conical, which are ringed basally. Hydrothecal pedicels short aperture apically, on a short collar. (composed of 2-3 wide annuli), alternate, borne lat- Records from Mediterranean: western Mediter- erally at distal end of each internode. Hydrotheca ranean, Adriatic, Black Sea. bell-shaped, not very deep, walls and diaphragm Known seasonality: 5,6,8-1. thickened, rim smooth. Gonothecae borne on the Reproduction: 5-11. stem or on the stolon; on short annulated pedicels, Distribution: warmer waters of eastern and west- male and female equal, inverted-conical to cylindri- ern Atlantic and Indo-Pacific, Mediterranean. cal, narrower at their base, wider distally domed References: Cornelius (1982, 1995); Gili with a central tubular aperture. (1986); Boero and Fresi (1986); Gili et al. (1989); Records from Mediterranean: eastern and west- Calder (1991); Boero and Bouillon (1993); Altuna ern Mediterranean, Adriatic. (1994); Avian et al. (1995); Migotto (1996); Medel Known seasonality and reproduction: throughout and López-González (1996); Medel and Vervoort the year. (2000); Peña Cantero and García Carrascosa Distribution: cosmopolitan. (2002). References: Patriti (1970); Cornelius (1975, 1982, 1995); Millard (1975); Gili (1982, 1986); Obelia dichotoma (Linnaeus, 1758) Boero and Bouillon (1993); Vervoort (1993a); (Figs. 114C-G) Altuna (1994); Avian et al. (1995); Medel and López-González (1996); Migotto (1996); Medel and Hydroid: colonies very varied in size and shape. Vervoort (2000); Schuchert (2001a); Peña Cantero Stems erect, up to 35 cm high, monosiphonic and and García Carrascosa (2002). branched, flexuose to straight, thickened in old colonies. Internodes with several annuli at their Obelia longissima (Pallas, 1766) base. Hydrothecae alternate, lateral, borne on com- (Figs. 115F-K) pletely annulate pedicels at the upper part of the internodes. Hydrotheca bell-shaped, usually not Hydroid: colonies long and flexuose, up to 40 cm very deep, thin walled, many times thrown into fine high; main stem monosiphonic, dark, with lateral longitudinal folds; rim even to crenate, slightly and alternated branches; in older colonies may be flared; diaphragm transverse to oblique. Gonothecae polysiphonic, and forked. Internodes usually nearly usually inverted-conical on annulate pedicels, trun- straight, thickened in older portions of the stem, cated at the distal end, with a short distal neck when annulated basally; nodes (but not the internodes) mature, where the aperture is. dark in young branches. Side branches of the stem

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also flexuose, usually branched in two at their ori- mosing. Perisarc of pedicel thickened and usually gin; internodes pale when young, becoming darker undulated throughout; sub-hydrothecal spherule after; internodes long, in zigzag, ringed basally. present. Hydrotheca bell-shaped, walls thickened in Hydrothecal pedicels alternate, at the end of each more or less degree, ring of perisarc basally separat- internode; hydrotheca elongate, bell-shaped, with- ing a small spherical chamber; rim with 8-13 short out longitudinal striae, perisarc very thin, diaphragm rounded cusps varied from deep and distinct to very transverse to oblique, rim shallow castellate or with shallow; hydranth with about 14 tentacles. Gonothe- shallow rounded cusps, slightly flared. Gonothecae cae borne on stolons, on short pedicels; sac-shaped, inverted-conical, narrower basally, aperture distally truncate distally, strongly compressed laterally, on a short collar. perisarc irregularly undulated; containing 2 eume- Records from Mediterranean: western Mediter- dusoids buds. ranean, Adriatic. Eumedusoid: umbrella pyriform, up to1.5 mm Distribution: nearly cosmopolitan, Red Sea. high, thin walls; exumbrella with 30-40 longitudinal References: Ramil (1988); Boero and Bouillon meridional ridges; circular canal narrow; 4 radial (1993); Altuna (1994); Avian et al. (1995); Cor- canals closed and obliterated near apex, giving rise nelius (1995); Medel and López-González (1996); to numerous blindly ending side branches; no Schuchert (2001a). manubrium; no marginal tentacles; «gonads» devel- oped between branches of radial canals, bell cavity Genus Orthopyxis L. Agassiz, 1862 almost filled with sexual products; 8 adradial stato- cysts. Hydroid: colonies stolonal or with short Records from Mediterranean: eastern and west- unbranched uprights stems; hydrorhiza branched ern Mediterranean. Only hydroids known. and anastomosing; hydrotheca campanulate, funda- Known seasonality: 3-12. mentally radially symmetrical but sometimes biradi- Reproduction: 3, 9. ally symmetrical with walls laterally compressed Distribution: Atlantic; Indo-Pacific; Mediter- and oval in cross section; perisarcal wall variably ranean. thickened; rim even or toothed; without true References: Millard (1975); Marinopoulos diaphragm but variably developed perisarcal thick- (1979); Boero (1981); Cornelius (1982, 1992, ening, sub-hydrothecal spherule; gonophores as 1995); Gili (1986); Ramil (1988); Boero and Bouil- eumedusoids either free, facultatively retained, or lon (1993); Medel and López-González (1996); never released; no manubrium and tentacles but with Genzano and Zamponi (1997); Medel and Vervoort 8 statocysts, gonothecae on hydrorhiza. (2000); Peña Cantero and Carrascosa (2002). Remark: Sometimes considered as congeneric with Campanularia. Orthopyxis everta (Clarke, 1877) References: Calder (1991); Cornelius (1995). Cornelius (1982) suggests that this species could Orthopyxis asymmetrica Stechow, 1919 be synonymous with O. crenata.

Remarks: Cornelius (1982) considers Campanu- Orthopyxis integra (MacGillivray, 1842) laria assymetrica Stechow, 1919 conspecific with (Figs. 116I-S) Orthopyxis integra. Östman et al. (1987) did not find distinct differences in the cnidome of both species. Hydroid: stolonal colonies with pedicels bearing Nevertheless many authors studying Mediterranean hydrothecae; hydrorhiza tortuous, anastomosing and material keep the two species separated (see Peña thick. Pedicels thick-walled and usually undulated Cantero and García Carrascosa, 2002). throughout; sub-hydrothecal spherule present. Hydrothecae bell-shaped, thick walled in variable Orthopyxis crenata (Hartlaub, 1901) (= Eucopella degree, rim smooth, usually unthickened and often bilabiata and Eucopella crenata) flared; basally a ring of perisarc limiting a small (Figs. 116A-H) spherical chamber; hydranth with 25-30 tentacles. Gonothecae of both sexes similar, borne on stolons, Hydroid: colonies composed of unbranched on a short pedicels; sac-shaped, contour often irreg- erected pedicels bearing hydrothecae; stolon anasto- ular, truncate distally, usually flattened, but some-

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times circular in transverse section; females with 1- Distribution: Atlantic; Indo-Pacific; Mediter- 3 eumedusoids buds. ranean. Eumedusoid: umbrella bell-shaped, higher than References: Kramp (1959a, 1961); Goy (1970); wide, mesoglea fairly thick; 4 radial canals either Schmidt and Benovic (1977); Cornelius (1982); meeting at apex or each closing before they meet, Bouillon (1984); Boero and Bouillon (1993). each one with one irregularly-lobed sac-like out- Hydroid: unknown. growth midway along each side; «gonads» on lobes of radial canals outgrowths; no marginal tentacles; 8 Subclass LIMNOMEDUSAE Kramp, 1938 statocysts; sexually mature on release. Records from Mediterranean: eastern and west- Hydroid: when known, very simple, solitary or ern Mediterranean, Adriatic. colonial; small, sessile; with or without tentacles; Known seasonality: present throughout the year often close to planula structure and budding planu- Reproduction: 4-8. la-like structures or frustules; body plans range from Distribution: Atlantic; Indo-Pacific; Mediter- forms without mouth and permanent gastric cavity = ranean. feeding planula: Microhydrulidae, to forms with References: Kramp (1961); Teissier (1965); Cor- mouth and hypostome, but without tentacles, form- nelius (1982, 1995); Boero and Fresi (1986); Boero ing transitory colonies or definitive colonies with a and Bouillon (1993); Vervoort (1993a); Avian et al. limited number of individuals: Craspedacusta, Lim- (1995); Medel and López-González (1996); Medel nocnida, Olindias; to forms with hypostome and and Vervoort, (2000); Schuchert (2001a); Peña Can- tentacles: Calpasoma, Gonionemus, Scolionema, tero and García Carrascosa (2002). Vallentinia; no perisarcal thecae, but cysts and stolons covered by chitin. Orthopyxis rubra (Behner, 1914) = Agastra rubra Medusa: usually without marginal cnidocyst ring Behner, 1914 (except Craspedacusta and Limnocnida); with “gonads” along radial canals or exceptionally on Remarks: Kramp (1961) considering the medusa manubrium (Armorhydra and Limnocnida). Margin- stage alone keeps A. rubra as a distinctive species. Nev- al tentacles peripheral, hollow, without true basal ertheless, the majority of authors consider it an invalid bulb, tentacles base usually with a parenchymatic species (see Cornelius, 1982) or conspecific with endodermal core embedded in the umbrellar Orthopyxis integra (see Stefani, 1959; Millard, 1975). mesoglea. Marginal sense organs as internal enclosed ecto-endodermal statocysts embedded in Genus Pseudoclytia Mayer, 1900 the mesoglea near ring canal or in the velum (only in Craspedacusta); without ocelli. Exceptionally Hydroid: unknown. reduced medusoids (Monobrachium). Planulae, Medusa: more than 4 radial canals and a corre- when known, with cnidoblasts but without embry- sponding number of manubrial lips. onic glandular cells. The Limnomedusae is a small group of Hydroi- Pseudoclytia pentata (Mayer, 1900) domedusa (medusa budding with entocodon) with a (Fig. 117A) dimorphic benthic-pelagic cycle; the hydroid stages are small, poorly developed, rarely modular; Medusa: umbrella up to 8 mm or more; with medusa production is comparatively much reduced; more than four radial canals; manubrium flask- many of the present-day Limnomedusae inhabit shaped; mouth with the same number of lips than fresh-or brackish-waters and their medusae are often radial canals; «gonads» sac-like round or oval in the seasonal, whereas the hydroids and the resting middle or distal part of radial canals without median stages are perennial, resisting adverse conditions: furrow; up to 20 marginal tentacles; tentacular bulbs Craspedacusta cysts can survive 40 years while globular, prominent; few partially developed mar- completely desiccated. ginal bulbs; velum narrow; normally 1, sometimes up to 3 statocysts between successive tentacles. Key to hydroids Records from Mediterranean: eastern and west- ern Mediterranean; Adriatic Sea. 1. Hydroids reduced to a spherical or irregular Known seasonality: 8; 9. body having from 20 to 480 µm, without

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tentacles, mouth and gastric cavity ...... Family MICROHYDRULIDAE ...... Microhydrulidae Bouillon and Deroux, 1967 – Hydroids with permanent mouth and gastric cavity ...... Olindiidae Reduced to a spherical or irregular body rang- ing from 20 to 480 µm, included in the superficial Key to medusae biological layer covering immersed objects in the sea or epibiotic on bivalve shells; didermic but 1. Reduced medusae, creeping burrowed in coarse very simple, without tentacles and mouth, gastric sand sediments; without radial canals, statocysts cavity becomes temporarly visible only when and nerve system ...... Armorhydridae food is engulfed; body covered by mucus, with a – Free swimming medusae, with radial canals, basal lamella of periderm; sexual reproduction statocysts and nerve system ...... Olindiidae unknown, asexual reproduction by mobile frus- tules. Family ARMORHYDRIDAE References: Thiel (1988); Jarms and Tiemann Swedmark and Teissier, 1958 (1996).

Hydroid: polyp small, solitary, mesopsammic, Key to hydroids attached to sand grains by mucoid periderm; about 10 short but extensible capitate-like tentacles, small 1. Cnidocysts: microbasic euryteles ...... hypostome, mouth inconspicuous; tentacular frus- ...... Microhydrula tules and podocysts; gonophores as free medusae, – Cnidocysts: microbasic semiophoric euryteles ... borne on body (Lacassagne, 1968a; 1973)...... Rhaptapagis Medusa: reduced, creeping within the interstices in coarse sand sediments; umbrella margin with a Genus Microhydrula Valkanov, 1965 whorl of two kind of solid tentacles, filiform and adhesive; manubrium voluminous, linked to subum- Hydroid: body rounded or elongated, terminal brella by longitudinal septa containing endodermal end either hemispherical or cauliflower-like in shape tubes; “gonads” on manubrium; velar opening nar- and armed with cnidocysts pending the species, row; no radial canals, nerve system, statocysts or ectoderm in a well definite unistratified layer, basal any other visible sense organ; sexes separate. layer of periderm thin; frustules formed by a great References: Swedmark and Teissier (1958d), number of small cells; living in biotic substrata and Thiel (1988). in sediments or on burrowing bivalves; cnidome: microbasic euryteles. Genus Armorhydra Swedmark and Teissier, 1958 Microhydrula pontica Valkanov, 1965 With the characters of the family. (Figs. 117D-E)

Armorhydra janowiczi Hydroid: 0.24 mm in height, living in biotic sub- Swedmark and Teissier, 1958 (Figs. 117B-C) strata and in sediments. Records from Mediterranean: eastern Mediter- Medusa: umbrella 1-4 mm; with 8-30 marginal ranean. tentacles, filiform ones alternating with capitate Known seasonality: 6-9. ones having a terminal adhesive papillae; about 12 Distribution: Atlantic; Mediterranean. longitudinal septa; gonads on manubrium. References: Bouillon and Deroux (1967); Thiel Hydroid: see family. (1988); Jarms and Tiemann (1996). Records from Mediterranean: western Mediter- ranean, Adriatic. Genus Rhaptapagis Bouillon and Deroux, 1967 Known seasonality: 3, 4. Distribution: Atlantic; Mediterranean. Hydroid: body irregular; ectoderm not very regu- References: Swedmark and Teissier (1958d); larly organised; peridermal basal lamella thick; frus- Salvini-Plawen (1966); Lacasagne (1968a; 1973); tules formed by a reduced number of large cells; Clausen (1971); Avian et al. (1995). cnidome: microbasic semiophoric euryteles.

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Rhaptapagis cantacuzenei – Statocysts spherical enclosed in mesoglea of Bouillon and Deroux, 1967 (Fig. 117F) umbrella margin ...... 2 2. With centripetal canals ...... 3 With the characters of the genus. – Without centripetal canals...... 4 Records from Mediterranean: eastern Mediterranean. 3. With primary tentacles projecting above Known seasonality: 6-9. umbrella margin and with terminal adhesive Distribution: Atlantic; Mediterranean. pads, secondary tentacles on umbrella margin References: Bouillon and Deroux (1967); Thiel without adhesive pads ...... Olindias (1988); Jarms and Tiemann (1996). – All tentacles on umbrella margin and without adhesive pads...... Maeotias Family OLINDIIDAE Haeckel, 1879 4. Tentacles in groups on bell margin ...... Gossea – Tentacles not in groups...... 5 Hydroid: usually solitary, seldom colonial; general- 5. With numerous statocysts ...... Gonionemus ly reduced, minute, either without tentacles or with one – With no more than 16 statocysts ..... Scolionema tentacle, or with a few tentacles in a single ring, some- times with dactylozooids; no theca; active asexual Genus Craspedacusta Lankester, 1880 reproduction by buds or frustules; usually with free medusae, exceptionally with free or fixed eumedusoids. Hydroid: fresh-water, solitary or forming small Medusa: with or without centripetal canals; inter- reptant colonies of 2 to 4, rarely 7 polyps; hydranths nal ecto- endodermal statocysts; simple, unbranched without tentacles, cylindrical, with apical mouth radial canals; “gonads” on radial canals or excep- (hypostome) surrounded by cnidocysts forming a tionally on manubrium (Limnocnida); no ocelli. spherical capitulum under which the polyp is slight- References: Uchida (1929); Pagès et al. (1992); ly tapering, forming a distinct neck; basal portion of Bouillon (1999); Bouillon and Barnett (1999); hydranths with periderm covering, attaching colony Bouillon and Boero (2000). to substrate; medusa buds lateral, on the middle or lower part of body column, often becoming terminal Key to hydroids by hydranth reduction; asexual reproduction by frustules, transversal division and resting stages 1. With tentacles ...... 4 (cysts). – Without tentacles...... 2 Medusa: well developed marginal cnidocyst ring, 2. Enclosed in a long perisarcal tube, solitary, no gastric peduncle; 4 simple radial canals; no cen- marine ...... Olindias tripetal canals; “gonads” only on radial canals, – Hydranth not enclosed in perisarc...... 3 hanging, pouch-like; evenly distributed marginal 3. Fresh-water form; solitary but often forming tentacles all of one kind, no adhesion organs; closed small transitory colonies ...... Craspedacusta ecto-endodermal statocysts in the velum and form- – Sea water form; only primary polyps known, ing centripetal tubes. inconspicuous (almost 0,1mm) atentaculate, Remarks: numerous species of Craspedacusta gross morphology similar to those of have been described, mainly from China, and it is Craspedacusta ...... Maeotias not unlikely that they represent nothing more than 4. Colonial, hydranth with one tentacle ...... variations of a single species...... Monobrachium – Solitary, hydranth with more than one tentacle .. Craspedacusta sowerbyi Lankester, 1880 ...... 5 (Figs. 118A-F) 5. Small, flat, discoid; with not well defined hypostomial region ...... Scolionema Hydroid: with the character of the genus. – Small, with a conspicuous conical hypostome ... Medusa: umbrella 10-20 mm wide, slightly flat- ...... Gonionemus ter than a hemisphere; mesoglea fairly thick; with well developed marginal cnidocyst ring; velum Key to medusa broad and well developed; manubrium large, upper portion conical with broad square base, tapering 1. Statocysts in elongated vesicles enclosed in downwards to cross-shaped distal region; mouth velum...... Craspedacusta with four simple or slightly folded lips, extending

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beyond umbrella margin; four straight radial canals clinging to the substrate with some of their tentacles; and circular canal broad and massive; four large medusa buds arising from the lower part of the smooth triangular pouch-like gonads, with rounded hydranth; elongated, mobile frustules formed in the comers, hanging down into subumbrellar cavity same area, polyps may reduce themselves and trans- from points of junction of radial canals with form in cysts. manubrium; with 200 to 400 or more, hollow mar- Medusa: umbrella 15-20 mm wide, hemispheri- ginal tentacles, in several series situated at different cal or somewhat flatter; mesoglea moderately thick; levels on umbrella margin, oldest four perradial manubrium fusiform, slightly shorter than umbrella marginal tentacles being largest and highest; bases cavity; with a slight gastric peduncle; mouth with 4 of marginal tentacles adherent to exumbrella; sur- short slightly crenulated lips; gonads along greater face of marginal tentacles covered with evenly dis- portion of radial canals, each in form of pendant sac tributed papillae each with three to ten cnidocysts; folded sinuously on alternate sides of radial canals; 100 to 200, or more statocysts, usually about half 60-80 long rather stiff marginal tentacles, with spi- number of marginal tentacles; statocysts situated in ral or annular cnidocysts clusters, each with an velum, forming centripetal tubes with basal enlarge- adhesive pad near distal end which is sharply bent; ments near umbrella margin. closed ecto-endodermal statocyst about as numerous Records from Mediterranean: in freshwaters of as tentacles. Mediterranean coasts. Records from Mediterranean: western Mediter- Known seasonality: 1-3. ranean, Adriatic. Distribution: cosmopolitan in freshwaters and Known seasonality: 6-9. sometimes in brackish waters of temperate and trop- Distribution: Arctic; Atlantic; Indo-Pacific; ical areas. Mediterranean. References: Payne (1924); Dejdar (1934); Kramp References: Joseph (1925); Werner (1950 a and (1961); Reisinger (1957); Bennett (1966); Naumov b); Kramp (1961); Picard (1951b, 1955a); Goy and Stepanjants (1971); Acker (1976); Acker and (1973b); Edwards (1976); Arai and Brinckmann- Muscat (1976); Culberson (1976); Ludwig (1977); Voss (1980); Boero and Bouillon (1993) Avian et al. Dendy (1978); Dumont (1994); Avian et al. (1995); (1995). Stepanjants et al. (1997); Jankowski (2001). Genus Gossea L. Agassiz, 1862 Genus Gonionemus A. Agassiz, 1862 Medusa: Olindiidae with four simple radial Hydroid: hydroid small, solitary, devoid of canals; with or without gastric peduncle; without hydrorhiza, with a conspicuous conical hypostome centripetal canals; with folded ribbon-like gonads and a circlet of 4-6 very long tentacles; medusa only on radial canals; with one kind of tentacles, buds, frustules, cysts formed by intensive asexual some of which are arranged in groups; without adhe- budding. sive pads; with statocysts enclosed in exumbrellar Medusa: Olindiidae without or with slight mesoglea. peduncle; with 4 simple radial canal; without cen- Hydroid: unknown. tripetal canals; with folded gonads on radial canals only; with evenly distributed marginal tentacles all Gossea corynetes (Gosse, 1853) of one kind, with organs of adhesion; with numerous (Figs. 119E-F) statocysts enclosed in mesoglea. Medusa: umbrella 12-16 mm wide, 8-10 mm Gonionemus vertens A. Agassiz, 1862 high, bell-shaped or hemispherical, mesoglea fairly (Figs. 118G-J, 119A-D) thick and rigid especially in apical region; manubri- um short, quadratic, one third to one half height of Hydroid: polyp generation in form of a small, subumbrellar cavity; mouth with four simple crenu- short, solitary, sessile conical or flask-shaped lated lips; 4 gonads linear, wavy, forming deep hydranths devoid of hydrorhiza, base large circular, hanging pouches along two thirds of radial canals; with a thin basal periderm, with a conspicuous con- 24 marginal tentacles in eight groups, 4 perradial ical hypostome and a circlet of 4-6 very long tenta- and 4 interrradial, all of about equal size, and 8-16 cles; the polyps often embedded in detritus and smaller isolated marginal tentacles, one between

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adjacent groups, all tentacles with rings of cnido- Genus Monobrachium Mereshkowsky, 1877 cysts, endodermal core of tentacles extending into marginal mesoglea; 24 statocysts, 3 between adja- Hydroid: colonies stolonal creeping, living on cent groups of tentacles. bivalve shells; hydrorhiza reticulated or incrusting Records from Mediterranean: eastern Mediter- or both reticulated and incrusting, covered or not by ranean. a thin perisarc; hydranth sessile, claviform, only one Known seasonality: 9, 11. oral filiform tentacle; hypostome large, club-shaped; Distribution: Atlantic; Mediterranean. sometimes dactylozooids in form of peduncled References: Kramp (1961); Bouillon (1978a); cnidocyst knobs; gonophores peduncled on Dowidar (1983), Boero and Bouillon (1993). hydrorhiza giving fixed or free eumedusoids, sexual Hydroid: unknown. cells borne in hydrorhizal coenosarc and migrating in eumedusoid radial canals after eumedusoid for- Genus Maeotias Ostroumoff, 1896 mation; with or without statocysts. Reference: Marche-Marchad (1963). Hydroid: only primary polyps known, incon- spicuous (almost 0,1 mm) atentaculate, gross mor- Monobrachium parasiticum phology similar to that of Craspedacusta. Mereschkowsky, 1877 Medusa: with centripetal canals; numerous tenta- (Fig. 120A) cles with tightly packed cnidocyst rings, all on umbrellar margin and without adhesive pads; Hydroid: colonies stolonal, with densely reticulat- “gonads” on radial canals, statocysts about in same ed hydrothiza, often forming a fused mat on bivalves number as tentacles. molluscs, growing usually on the apex zones and References: Mills and Sommer (1995); Mills along the grooves of the shell; thin perisarc present in (2000); Rees and Gershwin, (2000); Mills and Rees reticulated part of colonies; hydranths grouped, tubu- (2000). lar, narrower at base, hypostome separated from body by a rather deep constriction, with only one long api- Maeotias marginata (Modeer, 1791) cal tentacle, with a considerable accumulation of = Maeotias inexspectata Ostroumoff, 1896 cnidocysts around hypostome; dactylozooids in form (Figs. 119G-H) of short peduncled cnidocyst knobs; gonophores on hydrorhiza, on a short peduncle, ovoid, giving rise to Hydroid: see family characters. free or attached eumedusoids, with rudimentary Medusa: umbrella up to 39 mm wide and 24 mm manubrium, without mouth, with 4 radial canals and high; with numerous centripetal canals of different up to 16 short marginal tentacles; gonads on radial size, up to 15 per quadrant; manubrium prismatic, canals in eight longitudinal rows, living distal and with four perradial lobes extending onto radial proximal parts of the canals free. canals; mouth with four very long crenulated, frilly, Records from Mediterranean: western Mediter- lips with clusters of cnidocysts; gonads folded, ranean extending only along the manubrial lobes, up to 600 Distribution: Atlantic; Pacific; Mediterranean. marginal tentacles with simple tightly packed rings References: Ramil (1988); Besteiro et al. (1990); of cnidocysts and numerous short, club-shaped mar- Kubota (1991); Medel and López-González (1996); ginal appendages corresponding to the base of the Jarms and Mühlenhardt-Siegel (1998). oldest tentacles; statocysts about in same number as tentacles. Genus Olindias F. Müller, 1861 Records from Mediterranean: Black Sea; Azov Sea; Danube estuary. Medusa: Olindiidae with 4 radial canals and Known seasonality: 7-9. numerous centripetal canals; numerous tentacles of Distribution: Atlantic; Indo-Pacific; Mediter- two kinds: primary tentacles issuing above bell mar- ranean. gin, with distal adhesive pads and cnidocysts in trans- References: Kramp (1961); Borcea (1929); verse clasps, and secondary tentacles on bell margin, Calder and Burrell (1969); Denayer (1973); Boero without adhesive pads, with cnidocysts in rings; and Bouillon (1993); Mills and Sommer (1995); gonads with papillliform processes; numerous mar- Rees and Gershwin, (2000); Mills and Rees (2000) ginal clubs which may transform into tentacles, stato-

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cysts usually in pairs at base of primary tentacles. medusa bud formation the hydranth is reduced to a Hydroid: Only known in Olindias phosphorica kind of frustule without mouth and tentacles. see below. Medusa: umbrella 9 mm wide, about 6 mm high, mesoglea thick; gastric peduncle indicated; Olindias phosphorica (Delle Chiaje, 1841) manubrium cruciform, about half as long as umbrel- (Figs. 120B-E) lar cavity; mouth with four small lips; gonads extending along distal 1/2 - 1/3 of radial canals, rib- Medusa: umbrella 40-60 mm wide, almost hemi- bon-shaped, much folded; 40 to 70 marginal tenta- spherical, mesoglea fairly thick; 11-19 centripetal cles of different lengths, with globular marginal canals per quadrant; 30-60 primary tentacles; usually bulbs, cnidocysts rings along whole length of tenta- two statocysts at base of each primary tentacle; 100- cles, distal end sharply bent; adhesive pats rudimen- 120 secondary tentacles; 100-170 marginal clubs. tary except in old tentacles; 16 statocysts; medusa Hydroid: the polyps have not been yet found in budding on radial canals. field. Weill (1936) described from laboratory obser- Reference: Goy (1973a). vations a small solitary hydranth without tentacles enclosed in a cylindrical or irregularly curved Limnomedusae incertae sedis hydrothecae covering more than half its length, and much longer than the polyp itself; mouth distal sur- Genus Calpasoma Furmann, 1939 rounded by large cnidocysts. Records from Mediterranean: western Mediter- Hydroid: living in freshwater, of small size (100- ranean, Adriatic. 600µm); solitary but sometimes bi- or tripolar; 2 Known seasonality: 6-11. irregular whorls of tentacles at oral end, each tenta- Distribution: Atlantic; Mediterranean. cle consisting of a process of a single ectodermal References: Kramp (1961); Goy (1973b); Castel- cell (tentaculocyte) scattered with a few cnidocysts; ló i Tortella (1986); Gili (1986); Brinckmann-Voss hydranth reproducing only asexually, forming new (1987); Boero and Bouillon (1993); Avian et al. polyps of their own type or frustules, never produc- (1995); Medel and López-González, 1996; Goy ing medusae; sometimes considered as a tentaculate (1997). form of Craspedacusta but no inter-conversion has been observed between the two forms. Following Genus Scolionema Kishinouye, 1910 the authors they are considered or as two distinct species or as two stable forms of the same species. Hydroid: solitary, small, and discoid; with not well defined hypostomial region, with up to 5 tenta- Calpasoma dactyloptera Fuhrmann, 1939 cles; presenting varied and intensive lateral asexual (Fig. 121A) budding: medusa buds, frustules, cysts. Medusa: Olindiidae without or with slight With the characters of the family. peduncle; with 4 simple radial canals; without cen- Records from Mediterranean: fresh water aquar- tripetal canals; with folded gonads on 1/2 to1/3 of iums in Israel. distal part of radial canals only; with evenly distrib- Known seasonality: all the year ? uted marginal tentacles all of one kind, with rudi- Distribution: Brazil; Hawaii; Hungary; Israel; mentary organs of adhesion; with never more than Switzerland; USA (Indiana). 16 statocysts enclosed in mesoglea. References: Furmann (1939); Rahat and Camp- bell (1974); Jankowski (2001). Scolionema suvaensis (Agassiz and Mayer, 1899) (Figs. 120F-H) Subclass SIPHONOPHORAE Eschscholtz, 1829 (Figs. 14, 15, 19) Hydroid: solitary, small, short, flat, discoid, with not well defined hypostomial region, with up to 3-5 Pelagic, pleustonic or epibenthic Hydrozoa, tentacles; hydranths embedded in diatoms and detritus, forming highly polymorphic modular colonies of presenting intensive lateral asexual budding of frus- polypoid and medusoid zooids attached to a stem or tules or of resting stages (cysts) depending on environ- stolon supported by a floating and/or swimming mental condition and more seldom medusa buds, after system.

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Polypoid zooids of several sorts: pneumatophore, the Anthomedusae since desmonemes, typical of gastrozooids, dactylozooids, and bracts. All of them this subclass, are present in some groups; also usually associated with the gonophores in repetitive stenoteles are typical of Anthomedusae but are groups, or cormidia, along the stolon. All polypoid shared also with some Automedusae. Recent mole- structures without oral tentacles. The part of the cular analysis of siphonophore species also support stem below the floating system, bearing the their relationship with Anthomedusae (Collins, cormidia, is the siphosome, usually representing 2000, 2002). There is no alternation of benthic and most of animal’s length. Floating system composed pelagic life; the colonies remain pelagic along all by pneumatophores and/or nectophores (swimming their life-cycle (except the bentho-pelagic Rhodali- bells) together forming the nectosome. The com- idae). Each gonophore has a limited number of plete and fully developed animal is referred as the eggs (1 in the Physonects, 2 to 30 in the Caly- polygastric stage. Histologically, the polypoid and cophores, see above), but a cormidium can form medusoid zooids resemble the corresponding types successive gonophores increasing the number of of Hydroidomedusae. eggs, and the modular colonies, furthermore, are Three orders of Siphonophorae may be distin- formed by numerous cormidia. Compared to most guished on the basis of the presence or absence of Antho-and Leptomedusae, whose benthic colonies either an apical pneumatophore or of nectophores are long-lived, can undergo a resting phase and to grouped in a nectosome: the Cystonectae possessing produce higher numbers of eggs or medusae, the only a pneumatophore; the Physonectae possessing Siphonophorae apparently have a much lower both a pneumatophore and a nectosome; the Caly- reproductive rate but little is known on this part of cophorae with only a nectosome. its biology. Cnidome. The Siphonophorae have a cnidome of References: Mackie and Boag (1963); Purcell 9 cnidocyst types depending on the suborders: (1984); Pagès and Gili (1992); Mackie et al, (1987); acrophores, anacrophores, desmonemes, stenoteles, Kirkpatrick and Pugh (1984); Purcell and Mills homotrichous anisorhizae, atrichous isorhizae, (1988); Pugh (1999). microbasic mastigophores and birhopaloids, 4 of them being exclusive to the group but not common Order CYSTONECTAE Haeckel, 1887 to all species: acrophores, anacrophores (doubtfully recorded for Tiaricodon coeruleus by Wenqiao and Siphonophores with a relatively large pneu- Xu, 1990), homotrichous isorhizae and matophore and without nectosome; pneumatophore birhopaloids. The cystonects seem to posses only with apical pore; cormidia with gastrozooid, tentacle isorhizae and stenoteles; the physonects have a gen- and gonodendron, without bracts; gonodendron with eral cnidome formed by acrophores, desmonemes, gonopalpons, gonophores and asexual swimming homotrichous anisorhizae, atrichous isorhizae, bells. microbasic mastigophores, stenoteles and birhophaloides, the latest being exclusively found in Key to the families the apolemiids Apolemia uvaria and Tottonia con- torta; the calycophorans have anacrophores, 1. Pleustonic, pneumatophore horizontal ...... desmonemes, stenoteles, homotrichous anisorhizae, ...... Physaliidae microbasic mastigophores. The singlet microtubules – Epi- and mesopelagic, pneumatophore oval to of the cnidocyst cilium are very numerous, varying rounded ...... Rhizophysidae from 300 to 400, whereas in the other Hydrozoa the number varies between 8 and 22. Family PHYSALIIDAE Brandt, 1835 Remarks: the Siphonophorae can be considered as colonies of cormidia, formed by polypoid struc- This family is monotypic for Physalia physalis, tures that are so specialised to be assimilated to the the Portuguese Man O’War. organs of an individual (the colony). They are Reference: Totton, (1960), Carré and Carré (1995). sometimes considered as an enlarged larval nurse carrier or paedophore not becoming sexually Genus Physalia Lamarck, 1801 mature but budding off sexual medusoids which may be released along with other stem constituents Physalids with huge, asymmetric pneu- (Totton 1965). The cnidome suggests affinity with matophore, purplish blue in colour, up to 30 cm in

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length; top of the pneumatophore formed by an erec- Rhizophysa filiformis (Forskål, 1775) tile “sail” running diagonally; cormidia attached to (Figs. 121E-F) one side of the float, tentacles can stretch down many meters. Pneumatophore oval, 4.9 mm high by 4.0 mm References: Totton (1960); Pagès and Gili wide. Apical pore surrounded by a dark red circular (1992). spot. Pneumacodon, or outerwall, separated from pneumtosaccus, or inner wall, by a large cavity. Physalia physalis (Linné, 1758) Pneumatosaccus occupying the upper half of the (Figs. 121B-D) pneumatophore. Hypocystic villi well developed occupying the lower half. Polyps developing at the The only pleustonic siphonophore. Colonies con- base of the pneumatophore. Gastrozooids with three sisting of a large, purplish blue pneumatophore that types of tentilla: tricoronuate, the most common; floats on the sea surface, reaching about 30 cm in palmate, or dendritic; and in the shape of a bird’s length in the largest specimens. The pneumatophore beak. Gonotheca shaped like clusters of grapes carries the polyps, which form cormidia at the oral located halfway between each pair of gastrozoids. end; its top an erectile sail, the all drifting at the Records from Mediterranean: western Mediter- mercy of the winds. Pneumatophore enantiomor- ranean. phic, two forms, each the mirror image of the other. Known seasonality: 2-9. Each cormidium consisting of a gastrozooid associ- Distribution: Uncommon but widely distributed ated with a tentacle and a gonodendron; however, in the three great oceans and the Mediterranean. unlike other siphonophores, tentacle separating from References: Biegelow and Sear (1937); Pagès the basigaster during the later stages of develop- and Gili (1992); Mills et al. (1996); Pugh (1999). ment. The tentacles may attain several metres in length. Continuous formation of new cormidia. As Order PHYSONECTAE Haeckel, 1888 the cormidia mature, new gastrozooids gradually lose their tentacles and becoming palpons. Small Siphonophorae with an apical pneumatophore medusoid gonophores developing at the bases of the and, beneath it, a series of nectophores, except the terminal palpons. Functional gonophores of a given Athorybiidae which lack nectophores or with a colony are of a single sex only. reduced nectophore. Nectophores arranged in two Records from Mediterranean: eastern and west- opposite rows or circular chains forming the necto- ern Mediterranean, Adriatic. somal region around the stem. Most of Physonectae Known seasonality: 3-6. present two budding zones, one under the pneu- Distribution: widely distributed in tropical and matophore giving nectophores and the other at the subtropical regions in the three great oceans and basal end of the nectosome, giving the cormidia that sporadically found in the Mediterranean. form the siphosome. Cormidia with bracts, with References: Totton (1965); Daniel (1974); Kirk- dactylozooids. Without asexual medusoids on the patrick and Pugh (1984); Gili (1986), Pagès and Gili siphosome. When known with siphonula larvae. (1992); Avian et al, (1995); Pugh (1999). Key to families (mostly after Pugh, 1999) Family RHIZOPHYSIDAE Brandt, 1835 1. Nectophores present ...... 2 Oval-rounded pneumatophore with hypocystic – Nectophores absent ...... 7 villi at its base. 2. Nectophores deeply hollowed axially and with References: Carré and Carré (1995); Pugh tentacles between them; small delicate bracts..... (1999)...... Apolemiidae – Nectophores not hollowed axially, nectosomal Genus Rhizophysa Péron and Lesueur, 1807 tentacles absent...... 3 = Epibulia Haeckel, 1888 3. Nectosome and siphosome elongate, with a narrow stem...... 4 Rhizophysids with no wing-like processes – Nectosome and/or siphosome contracted or (ptera) in young gastrozooids. reduced ...... 7 Reference: Purcell (1981a). 4. Nectophores bilaterally symmetrical, arranged

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biserially ...... 5 References: Bedot (1888); Mills et al. (1996). – Nectophores dorso-ventrally flattened, usually asymmetric in shape, arranged in spiral...... Agalma elegans (Sars, 1846) Fewkes, 1880 ...... Forskaliidae (Figs. 122D-F) 5. Nectophores with straight dorsal radial canal.. 6 – Nectophores with sinuous dorsal radial canal..... Pneumatophore elongate, small, 1.1 mm high, ...... Pyrostephidae* apex red. Two rows of alternating nectophores 6. Tentilla uncoiled; cnidoband hypertrophied; no attached to the stem. Nectophores V-shaped, with cnidocyst on terminal process...... Erennidae* two prominent lateral wings. An apico-lateral ridge – Tentilla coiled; cnidoband normal . Agalmatidae running from the apex of the lateral wing to the mid- 7. Nectosome reduced or absent; siphosome point of the nectophore, an infero-lateral ridge run- reduced to solid body or corm ...... Athorybiidae ning along the outer margin, and a latero-ventral – Nectosome normal...... 8 ridge located on the central portion of the nec- 8. Nectosome elongated; siphosome shortened into tophore. Nectosac T-shaped. Pedicular canal short. laterally expanded spiral sac bearing enlarged Siphosomal stem contractile. Bracts triangular, elon- palpons; bracts absent...... Physophoridae gate, foliaceous in appearance, dorsal surface con- – Nectosome and siphosome contracted to form a vex, 9 mm long, with a central bracteal canal, solid corm; with a pneumatophore and an extending to about four-fifths the length of the bract, aurophore ...... Rhodaliidae* occasionally continuing as a very fine canal to the distal end. Tentilla tricornuate. *not present in Mediterranean Sea. Records from Mediterranean: eastern and west- ern Mediterranean. Family AGALMATIDAE Brandt, 1835 Known seasonality: 12, 2 to 6. Distribution: widely distributed in tropical and Physonect siphonophores with a biserial arrange- subtropical regions in the three great oceans and the ment of nectophores in the nectosome and a long Mediterranean (Alvariño, 1971). usually contractile siphosome. This is rather a catch References: Totton (1956, 1965); Palma (1973); all family. For many agalmatids four types of cnido- Kirkpatrick and Pugh (1984); Pagès and Gili (1992); cysts are present in the tentillum: homotrichous Lakkis and Zeidane (1995); Pugh (1999). anisorhizas; either microbasic mastigophores or stenoteles; desmonemes and acrophores. Agalma okeni Eschscholtz, 1825 Remark: this is rather a catch all family. (Figs. 122G-I) References: Carré and Carré (1995); Pugh (1999). Pneumatophore elongate, 7.0 mm high, apex pig- Genus Agalma Eschscholtz, 1825 mented. Nectophores similar to those of A. elegans, but nectosac Y-shaped. Bracts firm, up to 5.0 mm Agalmatids with tricornuate tentilla consisting of a long, prismatic, triangular, gradually thickening central swelling and two contractile lateral filaments. towards the distal portion, which has three vertical References: Pagès and Gili (1992); Mills et al. (1996). ridges delimiting four distal facets. Bracteal canal filiform, central, not reaching the distal facets. Agalma clausi Bedot, 1888 Records from Mediterranean: eastern and westen (Figs. 122A-C) Mediterranean. Known seasonality: 5 and 6. Siphosomal stem rigid. Leaf-like bracts with Distribution: widely distributed in tropical and deep red pigment spots on the surface, particularly subtropical regions in all seas and in the Mediter- the younger ones. Tricornuate tentilla that can be ranean (Alvariño, 1971). completely enclosed inside the involucrum. References: Totton (1965); Gili (1986); Pagès and Records from Mediterranean: Strait of Messina, Gili (1992); Lakkis and Zeidane (1995); Pugh (1999). Alborán Sea. Known seasonality: 4. Genus Cordagalma Totton, 1932 Distribution: Mediterranean and tropical Atlantic (Mills et al. 1996). Agalmatids with unicornuate tentilla; with heart-

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shaped nectophores devoid of lateral or vertical lat- appearance, up to 5.2 mm in height, 6.6 mm in eral ridges. width, and 4.0 mm in dorso-ventral length. Two References: Pagès and Gili (1992); Margulis prominent lateral wings and extensive central (1993); Carré and Carré (1995); Mills et al. (1996); thrust block containing the pedicular canal, more Pugh (1999). conspicuous in older nectophores. Nectosac large, T-shaped. Characteristic pattern of lateral radial Cordagalma ordinata (Haeckel, 1888) canals describing three curves along the lateral sur- = Cordalgama cordiforme Totton, 1932 face of the nectosac; middle curve widest. Apico- (Figs. 123A-B) lateral ridges not always reaching the level of the ostium. Bracts thin and leaf-shaped, variable in Colonies extremely fragile, reaching up to 30 cm shape but usually with two lateral processes and a in length. Nectosome occupying a third of colony larger central one. length. Pneumatophore fusiform, apex lightly pig- Records from Mediterranean: eastern and west- mented. Two opposing rows of alternating nec- ern Mediterranean. tophores. Adult colonies having up to 40 heart- Known seasonality: 2-6, 10,12. shaped nectophores with two rounded latero-anteri- Distribution: widely distributed in the three great or lobes and an acute centro-inferior lobe, 2.0 mm oceans and in the Mediterranean (Alvariño, 1971). high by 1.4 mm wide. Lateral radial canals, ascend- References: Totton (1965); Alvariño (1971) as ing from the ostial canal, join the dorsal canal at the Stephanomia rubra; Carré D. (1971); Kirkpatrick apex without describing a sigmoidal curve. Bracts and Pugh (1984); Avian et al. (1995); Lakkis and shaped like a truncated pyramid, with four lateral Zeidane (1995); Pugh (1999). facets. Very distinctive tentilla with a larval struc- ture and simplified cnidome. Genus Lychnagalma Haeckel 1888 Records from Mediterranean: western Mediter- ranean. Agalmatids with nectophores arranged biserially; Known seasonality: 4, 5. apico-lateral ridges prominent and divided close to Distribution: uncommon but widely distributed the base; lateral ridges extending out towards the top in warm waters throughout the world (Carré C., of the nectophore before reaching the apico-lateral 1968b; Carré D., 1973; Gili, 1986), Great Barrier ridges. Characteristic large tentilla consisted of a Reef (Totton, 1932), Chile (Palma, 1977). Epipelag- stalk, a tightly coiled cnidoband heavily armed with ic species also present at depths down to 726 m cnidocysts, and a terminal vesicle from which arise depth in the Alborán Sea (Mills et al., 1996). eight regularly spaced filaments (Pugh and Harbi- References: Totton (1932, 1965); Carré C. son, 1986). (1968b); Carré D. (1973); Palma (1973, 1977); Pagès and Gili (1992); Mills et al. (1996); Pugh (1999). Lychnagalma utricularia (Claus, 1879) (Figs. 123, 124A-D) Genus Halistemma Huxley, 1859 Diagnosis: like the genus Agalmatids whose tentilla have a single terminal Records from Mediterranean: Strait of Messina, filament (unicornuate) and only a vestigial involu- Alborán Sea. crum. Characteristic sigmoidal courses for radial Known seasonality: 4. canals on the nectosac of the nectophore that begins Distribution: Mediterranean and Atlantic with a downward sweep. (Bahamas) References: Pugh and Youngbluth (1988); Pagès References: Pugh and Harbison (1986); Mills et and Gili (1992); Pugh (1999). al. (1996).

Halistemma rubrum (Vogt, 1852) Genus Marrus Totton, 1954 (Figs. 123C-G) Agalmatids with nectophores truncated apically, Pneumatophore oval, 5.0 mm high by 5.3 mm nectosacs with straight, unlooped radial canals; with wide. Up to 46 nectophores per colony in two unicornuate tentilla. rows. Nectophore shape variable but squarish in Reference: Andersen (1981).

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Marrus orthocanna Totton, 1954 tacle or clump of tentacles between each pair of nec- (Figs. 124E-G) tophores. Nectophore deeply hollowed axially, forming a pair of large axial wings. Nectosac exten- Nectophores longer than broad, up to 15 mm in sive, lateral radial canals follow an S-shape course length, with no distinct lateral ridges. The apical of varying complexity. Bracts small and flimsy. This ridges divide close to the ostium and delimit two family requires a through review. narrow, triangular distal facets. Thrust block well- References: Carré and Carré (1995); Pugh (1999). developed and longer than the rounded lateral processes. Nectosac triangular. Bract roughly trian- Genus Apolemia Eschscholtz, 1829 gular with a flimsy, tacky appearance. Records from Mediterranean: western Mediter- Apolemiids with 1-6 tentacles between each pair ranean. of nectophores. Known seasonality: 6,12. Reference: Carré and Carré (1995). Distribution: North Atlantic and Mediterranean. References: Totton (1965); Andersen (1981); Apolemia uvaria (Lesueur,? 1811) Kirkpatrick and Pugh (1984); Gili (1986). (Figs. 126A-D)

Genus Nanomia A. Agassiz, 1865 Colonies reaching several metres in length. Pneu- Agalmatids whose unicornuate tentillum has a matophore bulb-shaped, widening near the apex. basal involucrum. Characteristic arrangement of the Nectosome with up to twelve nectophores arranged in gonodendra in that male and female ones, attached two parallel rows along the stem. Largest nectophore at the base of palpons, alternate on either side. 3.7 mm high, 3.4 mm wide and 4.2 mm deep. Nec- Reference: Pagès and Gili (1992). tophore consisting of two wings looking like those of a butterfly, with a deep ventral thrust block. Nectosac Nanomia bijuga (delle Chiaje, 1841) large. Lateral radial canals S-shaped with short (Figs. 125A-D) branches on the upper loop. Groups of five to six nec- tosomal tentacles issuing from the base of the nec- Pneumatophore elongate, very small, 1.8 mm high, tophores near the pedicular canal, at the base of mus- apex pigmented. Nectophores quadrangular, flattened cular lamellae. Siphosome up to several metres in in the abaxial-adaxial plane, L-shaped in lateral view, length, composed of several cormidia. Each cormidi- up to 2.3 mm high. Lateral wings twisting towards the um consists of a gastrozooid and about fifty palpons, adaxial or ventral surface of the colony. Nectophore both with thin filiform tentacles of a single type issu- with a well-developed ostial mouth, ostial velum ing from their bases. Palpons long and delicate. broad. Looped lateral radial canals on extensive nec- Bracts, like the nectophores, covered by opaque spots tosac. Pedicular canal long. Bracts leaf-like, variable bearing cnidocysts on the outer surface. in morphology, often with 3 processes at the distal Records from Mediterranean: western Mediter- end, occasionally with a cross ridge. ranean. Records from Mediterranean: eastern and west- Known seasonality: 8-4. ern Mediterranean. Distribution: Seldom caught epiplanktonic Known seasonality: 4-11. species. Cited in the Mediterranean, in the vicinity Distribution: widely distributed in warm and of Naples, Messina, Monaco, and Villefranche-sur- temperate regions of the three great oceans, and the Mer (Alvariño, 1971). In the Atlantic Ocean cited Mediterranean (Alvariño, 1971). off the British Isles (Kirkpatrick and Pugh, 1984) References: Totton (1965); Carré D. (1969b); and Norwegian fjords (Båmstedt et al., 1998). Alvariño (1971) as Stephanomia bijuga; Rottini References: Totton (1965); Carré and Carré (1973, (1971); Palma (1986); Gili (1986); Pagès and Gili 1995), Alvariño (1971); Kirkpatrick and Pugh (1984); (1992); Avian et al. (1995); Lakkis and Zeidane Pagès and Gili (1992); Båmstedt et al. (1998). (1995); Pugh (1999). Family ATHORYBIIDAE Huxley, 1859 Family APOLEMIIDAE Huxley, 1859 Physonects with relatively large pneumatophore. Uniquely, amongst the physonects, there is a ten- Nectosome greatly reduced or absent. Siphosome

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reduced to a dense corm on which the cormidia are incisions or pockets. No rete mirabile. Adult bracts arranged in a spiral. of four types. Gonodendra bearing long gono- References: Biggs and Harbison (1978); Carré palpons, with palpacles; with female gonophores and Carré (1995). attached close to their bases. Male gonophores attached at end of a stalk. Genus Athorybia Eschscholtz, 1829 Records from Mediterranean: off Villefranche- sur-Mer, off Messina (Sicily) and in the Alborán Sea. Athorybiids without nectosome; pneumatophore Known seasonality: 4. large; bracts flimsy with inconspicuous rows of Distribution: Mediterranean and Atlantic (the cnidocysts. Bahamas; off Woods Hole, USA). References: Totton (1954); Pagès (2002). Reference: Pugh (2003).

Athorybia rosacea (Forskål, 1775) Forskalia contorta (Milne Edwards 1841) (Figs. 126E-F) = F. leuckarti Bedot 1893 (Fig. 127A-F) Pneumatophore large, red pigmented, with cormidia arranged in spiral around it. No nectosome. Large nectophores with large left axial wing, Elongate, flimsy bracts with 7 inconspicuous rows without central apical incision. Longitudinal flap on of cnidocysts running down the convex dorsal side. upper side in apical half. Lateral basal pockets Records from Mediterranean: western Mediterranean. extend in flaps onto the lower surface. Nectosac Known seasonality: 9-4. with pronounced lateral wings, with dorsal and ven- Distribution: Atlantic and Mediterranean. tral canals usually not arising from pedicular canal. References: Pugh (1999); Pagès (2002). No pigment spots on ostium. Rete mirabile present or absent in pedicular canal. Three types of adult Family FORSKALIIDAE Haeckel, 1888 bract; with only one knee-shaped type, whose bracteal canal bends through a right-angle and has a Physonects with cylindrical or cone-shape necto- short side branch. Female gonophores, in two some, whose numerous nectophores have a multise- bunches, borne on long stalk, extending beyond rial, spiral arrangement. Nectophores flattened male ones. dorso-ventrally, often asymmetrical in shape. Nec- Records from Mediterranean: western Mediter- tosac restricted to basal half, with straight radial ranean, Adriatic. canals. Siphosome also coiled, with gastrozooids Known seasonality: 9-6. borne on long stalks. Gastrozooids borne on long Distribution: rare, to date only caught in the peduncles that are covered in bracts. Bracts usually Mediterranean (Totton, 1965) and observed from gelatinous and of variable shape of four types: stem, submersibles at depths between 150 and 600 m in bolster and two kinds of knee-shape. Several the Bahamas (Youngbluth, 1984). gonopalpons, with palpacles, present on gonoden- References: Totton (1965); Youngbluth (1984); dra, which bear both male and female gonophores. Pagès and Gili (1992); Avian et al. (1995); Pugh References: Carré and Carré (1995); Pugh (1999), Pugh (2003). (1999), Pugh (2003). Forskalia edwardsi Kölliker, 1853 Genus Forskalia Kölliker, 1853 (Figs. 127G-H)

With the characters of the family. Nectophores with small left axial wing, and no Reference: Pagès and Gili (1992); Pugh (1999); central apical incision; with apical thickened Pugh (2003) mesoglea. Small yellow pigment spot on ostium where dorsal radial canal joins ring canal. No rete Forskalia asymmetrica Pugh 2003 mirabile. Four types of adult bract: knee-shape (Figs. 126G-H) ones without side branch to bracteal canal. Gon- odendra with female gonophores not having elon- Large nectophores, with small rounded left axial gated base. Palpacle of gonopalpon has appearance wing, and a small central apical incision. No lateral of a string of beads.

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Records from Mediterranean: off Villefranche- shaped. Upper half of radial canals describes a high- sur-Mer. ly characteristic sigmoidal curve. Pedicular canal Known seasonality: in winter. prominent. Palpons characteristic by their large size Distribution: western Mediterranean, Red Sea, and banana-shape, with long and fine palpacles. Atlantic and Pacific. Palpons covering and protecting the rest of the ele- References: Totton (1965); Youngbluth (1984); ments making up the bag-like siphosome and bear- Pagès and Gili (1992); Pugh (1999), Pugh (2003). ing clusters of cnidocysts on their distal ends. Records from Mediterranean: western Mediterranean Forskalia formosa Keferstein and Ehlers 1861 Known seasonality: 9-4. (Figs. 127I-K) Distribution: widely distributed in tropical and subtropical regions in the three great oceans and in Nectophores with large, pointed left axial wing, the Mediterranean (Alvariño, 1971). and shallow but broad and rounded right wing. Small References: Totton (1965); Alvariño (1971); apical incision between them. Small lateral, but no Kirkpatrick and Pugh (1984); Gili (1986); Pagès and baso-lateral pockets. No rete mirabile. Four types of Gili (1992); Pugh (1999). adult bract; knee-shaped ones without side branch to canal. Gonodendra with female gonophores, in two Order CALYCOPHORAE Leuckart, 1854 bunches, attached close to bases of gonopalpons; male gonophores borne on long stalk. Highly polymorphic Siphonophorae without Records from Mediterranean: off Villefranche- pneumatophore, with a reduced nectosome typically sur-Mer, off Messina (Sicily) and Alborán Sea. formed by one or two but sometimes more nec- Known seasonality: in winter. tophores. Usually with a single bract per cormidia Distribution: Mediterranean and Atlantic (The (except the Hippopodiidae without bracts), without Bahamas). dactylozooids (except in Stephanophyes), in some References: Avian et al. (1995); Mills et al. cases with asexual medusoid structures on sipho- (1996), Pugh (2003). some. Generally the cormidial units are detached successively from the stem and become eudoxid or Family PHYSOPHORIDAE Eschscholtz, 1829 sexual stage. Usually a calyconula larvae.

Physonects with a flimsy, apparently ridgeless Key to the families (after Pugh, 1999) nectophores each with an extensive nectosac, which has characteristic, looped lateral radial canals. Both 1. Nectophores dorso-ventrally flattened ...... 2 dorsal and ventral canals are sinuous. Siphosome – Nectophores not dorso-ventrally flattened, bracts compact sac on which the simple, bractless cormidia present ...... 3 are borne in spiral. Each cormidium has a single, 2...... Up to 15+ similar, closely applied, dorso- greatly enlarged palpon. Monotypic family for the ventrally fattened nectophores bearing species Physophora hydrostatica. protuberances or spines; large but shallow Reference: Carré and Carré (1995). nectosac; bracts absent ...... Hippopodiidae – Small, flattened nectophores, with vestigial Genus Physophora Forskål, 1775 nectosac and reduced somatocyst...... Prayidae, subfamily Amphicaryoninae With the characters of the family. 3. Nectophores and bracts rounded, smooth-walled, Reference: Pagès and Gili (1992). with thick mesoglea...... 4 – Nectophores and bracts pointed, toothed or of Physophora hydrostatica Forskål, 1775 irregular shape ...... 6 (Figs. 128A-C) 4. Usually 2 nectophores ...... 5 – Single, fragile, larval nectophore, with a simple Pneumatophore elongate, 4.5 mm high, 1.1 mm somatocyst and narrow hydroecium; small, wide, with a pore in the apical reddish region. Nec- fragile bract with a single canal ...... tosome consisting of up to 12 nectophores in two ...... Sphaeronectidae alternate rows. Nectophore flimsy, devoid of con- 5. Two nectophores of approximately equal size, spicuous ridges and up to 20 mm high. Nectosac Y- forming an apposed pair; somatocyst simple or

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branched; bracts with 5 or 6 branches to the canal References: Sears (1953); Carré and Carré system...... Prayidae, subfamily Prayinae (1995); Pugh (1999). – Two nectophores of unequal size, with reduced somatocysts; nectosac of smaller nectophore Genus Abyla Quoy and Gaimard, 1827 usually reduced or obsolent; bracts with two branches to canal system...... Abylid with 10 or 11 facets in anterior nec- ...... Prayidae, subfamily Amphicaryoninae* tophores. The apical facet is divided by a transverse 6. Two morphologically different nectophores; one ridge, and many ridges are serrated, particularly (anterior) superimposed over the other basally. Dorsal nectosac and median hydroecium are (posterior) ...... 8 long tubes extending almost to apex of nectophore. – With usually a single nectophore ...... 7 The large oval somatocyst lies ventrally. Posterior 7. Single, usually large nectophore bearing simple nectophore with long, tapering apical apophysis, has or toothed ridges; somatocyst usually branched; only 4 ridges. The ventral ridges define the hydroe- large bract without neck shield and extensively cial wings and are heavily serrated basally. The left branched canal system...... hydroecial wing bears a toothed comb or flap. Five, ...... Prayidae, subfamily Nectopyramidinae* usually serrated, ostial teeth. Prismatic bracts with 6 – Single, usually small, apically pointed facets, the dorsal one being rectangular. Very large nectophore, with simple caecal somatocyst; bract phyllocyts, with 2 canals running down toward the conical or angular...... 9 ventro-lateral corners of the apical facet. The bracts 8. Posterior nectophore with a somatocyst; anterior cannot, at present, be identified specifically. nectophore with extensive opening of Reference: Pugh (1999). hydroecium onto ventral surface; small bract with phyllocyst and 2 canals extending into neck Abyla haeckeli Lens and van Riemsdijk, 1908 shield...... Clausophyidae (Figs. 128D-F) – Posterior nectophore without somatocyst; hydroecium of anterior nectophore usually opens Anterior nectophore as wide as long, without basally; bracts conical or angular, with wing-like processes. Transverse ridge separates ven- phyllocyst and, at most, one canal ...... 9 tral facet from apico-ventral one. Posterior nec- 9. Conical stream-lined anterior nectophore, tophore with up to 5 teeth on comb. Lateral ostial usually with shallow hydroecium; posterior teeth closer to dorsal tooth than ventral ones. nectophore, when present, usually apically Reference: Pugh (1999). truncated and of similar size or smaller than anterior one; conical bracts...... Diphyidae Genus Abylopsis Chun, 1888 – Anterior nectophore angular, with inflated somatocyst and deep hydroecium; posterior Abylid whose anterior nectophore has a pentagonal nectophore, when present, larger than anterior dorsal facet without a median ridge. Seven-facet one; rigid angular bracts ...... Abylidae anterior nectophore, but without an apical facet, and pentagonal dorsal and ventral facets. The somato- *not present in the Mediterranean Sea. cyst has an apical diverticulum. Posterior nec- tophore has prominent basal teeth and with 5 ridges Family ABYLIDAE Agassiz, 1862 and a short curved apical apophysis. The left lateral ridge bifurcates close to the apex. Flaps on both Calycophorans with rigid, angular nectophores, the wings of hydroecium. Bracts with 7 facets. Phyllo- posterior one, without a somatocyst, usually being cyst with swollen apico-lateral branches and apical much larger, and bearing serrated ridges and teeth. In diverticulum, while distally is a narrow tube. all but one species the somatocyst of the anterior nec- References: Pagès and Gili (1992); Pugh (1999). tophore has curved over to occupy a ventral position. The hydroecium of the anterior nectophore is an Abylopsis eschscholtzi (Huxley, 1859) enclosed tube opening basally. During development a (Figs. 128G-K) temporary larval bract is formed before the larval nec- tophore. The latter is retained in the polygastric stage Dorsal and ventral facets of anterior nectophore as the anterior nectophore. almost pentagonal, of nearly equal size, with strong-

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ly serrated ridges. Lateral radial canals forming a Gonophore in the shape of a rectangular prism 4.6 right angle from the pedicular canal and directed mm high with four distinct ridges ending in four towards the ostial canal, without ascending loop. acute basal cusps, the ventral cusps somewhat larg- Posterior nectophore less than twice as long as wide, er than the dorsal ones. with relatively large apical apophysis. Each hydroe- Records from Mediterranean: eastern and west- cial wing bearing a secondary wing whose inner ern Mediterranean. margins is fused. Between four and eight teeth on Known seasonality: present all the year. the curve on the left wing, three or four on the right Distribution: quite common in the temperate wing. Bracts cuboidal, their dorsal facet forms a reg- regions of the three main oceans, and in the Mediter- ular pentagon, their apico-lateral facets rectangular. ranean (Alvariño, 1971). Epipelagic (Pugh, 1974), Records from Mediterranean: eastern and west- but also present in the mesopelagic zone (Gili et al., ern Mediterranean. 1987a). Known seasonality: 4 to 7. References: Totton (1965); Carré C. (1967b); Distribution: common and abundant in the warm Alvariño (1971); Palma (1973); Pugh (1974, 1999); and temperate regions in the three great oceans, less Bone and Trueman (1982); Gili (1986); Gili et. al. common in the Mediterranean (Alvariño, 1971). (1987a); Pagès and Gili (1992), Avian et al. (1995); Epipelagic distribution (Pugh, 1974). Lakkis and Zeidane (1995); Buecher (1999); References: Totton (1965); Alvariño (1971); Rot- Gamulin and Krisnic (2000). tini (1971); Daniel (1974); Pugh (1974, 1999); Gili (1986); Pagès and Gili (1992); Avian et al. (1995); Genus Bassia Agassiz, 1862 Lakkis and Zeidane (1995). Abylines whose anterior nectophore has not an Abylopsis tetragona (Otto, 1823) apical diverticulum to the somatocyst, and with the (Figs. 129A-E) hydroecium not extending below the basal facet. Somatocyst large and globular. Posterior nectophore Polygastric stage: anterior nectophore polyhedral with 4 ridges ending in short basal teeth. Bract with with seven faces. Ventral and dorsal surfaces pen- median apical ridge has a quadrilateral dorsal facet. tagonal, the latter higher, up to 10 mm in height. Phyllocyst is a long tube, swollen apically, without Ridges weekly serrated. Hydroecium deep, reaching apico-lateral branches. Gonophore with four longi- nearly the midpoint of the nectophore. Radial canals tudinal ridges which end basally in minute teeth. of nectosac originating at the junction with the pedicular canal and rising towards the upper end, Bassia bassensis (Quoy and Gaimard, (1833) forming an ascending loop, and then descending to 1834) (Figs. 129F-I) the circular canal. Somatocyst globular, with an api- cal diverticulum at the level of the nectosac. Poste- Polygastric stage: ridges on specimens fixed in for- rior nectophore up to 40 mm in length, rectangular, malin taking on a bluish-white hue (same applies to three times as long as wide, with a prominent apoph- eudoxids). Anterior nectophore a seven-sided polyhe- ysis. Four radial canals in the upper half, five in the dral with pentagonal dorsal and ventral surfaces. Two lower one because the left ventral canal has a blind quadrangular apico-lateral surfaces joined by a central termination halfway up and a little above the origin apical ridge. Two large baso-lateral surfaces separated of a new canal forming a right angle and directed from the apico-lateral surfaces by a horizontal ridge. towards the ostial canal. A “rete” at the base of the Hydroecium deep, reaching the midpoint of the nec- right ventral canal, from which a short, blind ventral tophore, with a large quadrangular opening. Nectosac canal issues towards the left. Upper half of the right relatively small, with lateral radial canals running wing of hydroecium bearing a comb-like structure from the ostial canal to the junction with the pedicular with about nine teeth. Lower portion bearing five canal, with only a slight curve instead of an arc. basal teeth varying in size, right ventral tooth Apices of hydroecium and nectosac more or less at the largest. Bract up to 7.0 mm high, elongated, penta- same level. Somatocyst large, globular, devoid of gon with apico-lateral facets trapezoidal. Upper half diverticulum or apical projection. Posterior nec- of phyllocyst bearing two thick, lateral processes tophore higher than the anterior nectophore, up to 15.0 above the hydroecium and extending towards the mm high, consisting of four ridges, not as thin as in the apical surface in the form of a narrow diverticulum. anterior nectophore. Bases of ventral ridges compris-

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ing two prominent teeth, right tooth larger than left of the hydroecium; not extending past the apex of tooth. Eudoxid: bract in the form of a seven-sided the hydroecium. Posterior nectophore elongated, polyhedral with well-developed ridges. Dorsal surface oblong, up to 50.0 mm high, pointed apically. Left rhomboidal, ventral surface in the shape of a five- ventral wing ending in a characteristic prominent, pointed star. Apico-lateral surfaces quadrangular. elongate, serrated basal tooth. Comb on right ventral Baso-ventral margins of lateral surfaces describing a wing bearing six teeth; inferior margins of both curve ending in a medial tooth. Hydroecium large, wings dentate. Eudoxid: bract roughly triangular, deep, hook-shaped, reaching to the midpoint of the with two supra-lateral horns and a dorsal ridge end- bract. Phyllocyst is a long tube long, without lateral ing in a point basally. Up to 20.0 mm high. Apical processes. Gonophore with four lateral ridges that end surface triangular, concave. Characterized by a right basally in minute teeth. lateral ridge, originating at the lower margin, stop- Records from Mediterranean: eastern and west- ping before it reaches the apico-dorsal ridge. Phyl- ern Mediterranean. locyst cylindrical, with two filiform lateral projec- Known seasonality: 3, 12. tions and a basal tip recurved upwards. Gonophore Distribution: Present in the temperate regions off with basal teeth varying in size. A relatively short, the three great oceans and in the Mediterranean inconspicuous hook issuing from one of the ventral (Alvariño, 1971). ridges, curving towards the base of the hydroecium. References: Totton (1965); Palma (1973); Daniel Teeth located above the hook on the ventral margin (1974); Kirkpatrick and Pugh (1984); Gili (1986); of the opposite wing. A small dorsal tooth. Lateral Pagès and Gili (1992); Carré and Carré (1995); ridge near the bracteal wall deeper than the oppos- Lakkis and Zeidane (1995); Pagès et al. (2001). ing ridge at the apex. Records from Mediterranean: Strait of Gibraltar. Genus Ceratocymba Chun, 1888 Seasonality: ? Distribution: widely distributed in the Atlantic Abylid with characteristically shaped bract, called Ocean, where its range is very broad. Also present in a cymba. Anterior nectophore with 7 facets. Apical temperate regions in other seas and in the Mediter- facet not divided by a transverse ridge. Posterior nec- ranean (Alvariño, 1971). tophore long and narrow, without wing-like expan- References: Bigelow and Sears (1937); Totton sions. Short dorsal ridge ends on the dorsal tooth. (1965); Casanova (1980); Alvariño (1981); Kirk- Bracts with a median dorsal ridge. Left lateral facet patrick and Pugh (1984); Pagès and Gili (1992); divided by another ridge. Bracts roughly triangular Pugh (1999). with a concave apical facet and prominent lateral horns. Phyllocyst with 2 thin ventro-lateral branches. Genus Enneagonum Quoy and Gaimard, 1827 Its distal end bends dorsally to form a blind sac. References: Pagès and Gili (1992); Pugh (1999). Abylids where the large, pyramidal anterior nec- tophore is the only developed. The conical somato- Ceratocymba sagittata (Quoy and Gaimard, 1827) cyst is situated above the hydroecium, and extends (Figs. 130A-C) to a greater height than the nectosac. The bract is cuboidal, with slightly concave facets. Swollen Polygastric stage: anterior nectophore pyramidal, somatocyst with 2 lateral and apical processes. elongate, up to 40.0 mm high. Large, tapered apical Reference: Pagès and Gili (1992). process called a pyramidal process. Four ridges con- verging at the apex. Characteristic apical surface of Enneagonum hyalinum Quoy and Gaimard, 1827 the family Abylinae no longer present. Hydroecium (Figs. 130D-F) bell-shaped, with a large opening, in the centre of the base of the nectophore. Nectosac narrow, high, Polygastric stage developing only a single nec- reaching almost to the apex of the nectophore. Lat- tophore. Nectophore pyramidal, up to 15.0 mm wide. eral radial canals ascending over a short segment of All surfaces homologous to those in other Abylopsi- the nectosac from the pedicular canal, describing a nae, except that in E. hyalinum, there is a median ridge very tight arc and then descending towards the ostial subdividing what is equivalent to the dorsal surface in canal. Somatocyst oval, positioned between the dor- other Abylopsinae. The two dorsal surfaces and the sal surface of the nectophore and the dorsal surface two apico-lateral surfaces visible when viewed from

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the apex. A triangular basal surface beneath the dorsal base. The deep hydroecium reaches to about the surfaces, the two baso-lateral surfaces, and the ventral height of the nectophore and is open at the ostial surface all visible when viewed basally. Ridges and level. Posterior nectophore up to 30 mm in height, basal margins slightly dentate. Somatocyst carrot- with a large notched mouth. The hydroecium shaped, consisting of two thickened lateral processes extends the length of the nectophore and is bounded and an apical diverticulum, lacking a descending dor- by large lateral wings. The somatocyst is long and sal segment, differentiating it from the somatocysts of narrow. the rest of the members of the family Abylidae. Arc Eudoxid: bract conical, up to 8 mm in height, followed by the lateral radial canal including a blind with a rounded apex and an extensive neck-shield. diverticulum. Eudoxid: bract cuboidal, 4.0 mm high. The phyllocyst, slightly swollen basally reaches the Five surfaces: apical, dorsal, ventral, and two laterals. apex. The gonophore is undescribed. No baso-lateral surfaces, the entire space being occu- Records from Mediterranean: off Messina (Sici- pied by the large hydroecial opening. Swollen phyllo- ly), Adriatic, western Mediterranean. cyst with 2 lateral and apical processes. Gonophore Known seasonality: present all the year. with a well-developed apophysis occupying nearly a Distribution: Atlantic, Pacific, Mediterranean third of the gonophore. References: Keferstein and Ehlers (1861, as Records from Mediterranean: eastern and west- Diphyes ovata), Kirkpatrick and Pugh (1984); Patri- ern Mediterranean. ti (1969) as Clausophyes massiliana, Gamulin and Known seasonality: 3. Krisnic (2000). Distribution: common in warm and temperate regions in the three great oceans, and in the Mediter- Family DIPHYIDAE Quoy and Gaimard, 1827 ranean (Alvariño, 1971). Epipelagic but also abun- dant in the mesopelagic zone down to a depth of Calycophorae with polygastric stage with one or 1000 m (Pugh (1974). two dissimilar streamlined definitive nectophores References: Bigelow and Sears (1937); Totton arranged serially. Anterior nectophore with somato- (1965); Daniel (1974); Pugh (1974, 1999); Kirk- cyst, posterior not; hydroecium generally reduced in patrick and Pugh (1984); Gili (1986); Pagès and Gili anterior nectophore; the nectosac occupies most of (1992); Lakkis and Zeidane (1995). the nectophore. References: Carré and Carré (1995), Pugh Family CLAUSOPHYIDAE Totton, 1965 (1999).

Both anterior and posterior nectophores possess Genus Chelophyes Totton, 1932 a somatocyst: The phyllocyst of the eudoxid bract when known has two fine branch canals that run Diphyids with rigid nectophores; anterior one down into the neck shield. with 5 ridges, dorsal one extends only a short dis- tance up from the ostium. Claw-shaped hydroecium. Posterior nectophore apically pointed, mouth-Fig. Genus Clausophyes Lens and Riemsdijk, 1908 divided with two strong asymmetric teeth. Bracts with conical eudoxids, small rounded neck-shield, Nectophores rounded, smooth, unridged, lateral- hydroecium cylindrical and long that almost stretch- ly flattened. Anterior nectophore usually smaller es the apex. than posterior one, with deep hydroecium in basal References: Pagès and Gili (1992); Pugh (1999). half and with a long, thin somatocyst which has an elongated swelling towards its apex. Lateral canal of Chelophyes appendiculata (Eschscholtz, 1829) both nectophores are looped. (Figs. 130J-K, 131A-C) References: Pugh (1995, 1999). Polygastric stage: Anterior nectophore of firm Clausophyes ovata (Keferstein and Ehlers 1860) consistency. Up to 12.0 mm in height by 3.6 mm in (Figs. 130G-I) dorso-ventral width. Only three ridges, the two ven- tral ridges and the right lateral ridge (sensu Bigelow) Polygastric stage: anterior nectophore up to 20 converging at the apex. Left lateral ridge not reach- mm in height, roughly triangular but rounded at its ing the apex and only a short section of the dorsal

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ridge visible above the ostium. Hydroecium horn- cornuate, directed towards the ventral surface, not shaped, directed towards the ventral surface and as deep as in C. appendiculata, edge blunt. Basal extending to approximately one sixth of the nec- lamella divided into two quadrangular wings, with tophoral height. Basal lamella divided into two a small tooth on the baso-central end of each. Pos- square wings with sharp outer ends; basal lamella terior nectophore with five serrate ridges, ventral margin convex. Fusiform, long somatocyst that aris- ridges longer on upper half of nectophore, shorter es at the apex of the hydroecium, reaching two- on the lower half, ending in sharp point longer on thirds to three-quarters of nectosac height. Posterior the left ventral ridge. Upper ventral Fig. fingernail- nectophore 8.2 mm in height by 2.0 mm in dorso- shaped issuing from the right ridge and directed ventral width, apex pointed, same consistency as towards the left ridge. that of the anterior nectophore slightly asymmetri- Eudoxid: very similar to that of C. appendicula- cal. Four ridges each ending basally in a conspicu- ta (Totton, 1965). ous tooth, left tooth longer than right one. Ventral Records from Mediterranean: ?Alborán Sea. ridges bearing a tooth at the level of the ostium. Seasonality: ? Basal lamella entire, concave. Hydroecial canal Distribution: widely distributed in warm and long. temperate regions in the Pacific and Indian oceans. Eudoxid: bract roughly conical, hood-shaped, Occasionally present in the Atlantic, where it has with a short, rounded neck-shield. Hydroecium been recorded off Honduras, Venezuela, Bermuda, deep. Phyllocyst cylindrical elongated reaching and Cape Verde. Cited in the Alborán Sea in the nearly to the apex. Gonophore composed of four Mediterranean, near the Strait of Gibraltar (Alvar- longitudinal ridges. Peduncle long, penetrating into iño, 1971). Nevertheless, the Atlantic records are the bracteal cavity, rigidly attached to the bracteal doubtful because it seems that this species shows margin. mainly an Indo- Pacific distribution. Records from Mediterranean: eastern and west- References: Alvariño (1971); Pagès and Gili ern Mediterranean. (1992); Pugh (1999). Known seasonality: 1-12. Distribution: widely distributed in warm and Genus Dimophyes (Chun, 1897) temperate regions in the three great oceans and the Mediterranean (Alvariño, 1971); one of the most Diphyids with anterior nectophore without common and abundant siphonophores in all seas. ridges, mouth Fig. undivided, hydroecium largely Epipelagic species also dwelling in the mesopelagic opened on its ventral side, carrot-shape somatocyst zone (Pugh, 1974; Gili et al., 1987). reaching to about two thirds the height of the nec- References: Totton (1965); Pugh (1974, 1999); tophore. Posterior nectophore reduced, with the Bone and Trueman (1982); Mackie and Carré opening of the nectosac lying dorso-basally. Conical (1983); Kirkpatrick and Pugh (1984); Gili (1986), bract with extensive neck-shield that is run by a Gili et al. (1987); Pagès and Gili (1992), Carré and median canal from the phyllocyst; the latter with Carré (1995); Lakkis and Zeidane (1995); Buecher apical and lateral horns. Monotypic genus. (1999); Gamulin and Krisnic (2000). References: Pagès and Gili (1989, 1992d); Pugh (1999). Chelophyes contorta (Lens and Van Riemsdijk, 1908) Dimophyes arctica (Chun, 1897) ( Figs. 131D-F) (Figs. 131G-I)

Polygastric stage: anterior nectophore consis- Polygastric stage: anterior nectophore devoid of tency firm, up to 4.6 mm in height by 1.7 mm in ridges, apex arched, 15.0 mm in height. Hydroecium dorso-ventral width. Similar to that of C. appen- deep, bell-shaped, with ventral opening, and summit diculata, the main difference is that the ventral above the ostium. Basal lamella high, entire, without facet is strongly twisted to the right. Five serrate wings. Somatocyst carrot-shaped, reaching to three- ridges, (three to the apex) only a short section of quarters of nectophore height. Posterior nectophore the dorsal ridge visible above the ostium, right lat- seldom found and much reduced. The deep hydroe- eral ridge not reaching the apex. Ventral surface cium is bounded by two broad wings. The nectosac and somatocyst twisted to the right. Hydroecium opens on to the baso-dorsal surface.

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Eudoxid: up to 10 mm in height. The bract is Records from Mediterranean: western Mediter- conical with an extensive, thin neck shield. The ranean. phyllocyst has apical and lateral horns and a fine Known seasonality: present all the year. basal process, which passes down the neck shield. Distribution: widely distributed in tropical and The gonophore has a very small mouth and any subtropical regions in the three great oceans and in traces of a hydroecium. the Mediterranean (Alvariño, 1971). Records from Mediterranean: western Mediter- References: Totton (1965); Alvariño (1981); ranean. Pagès and Gili (1992); Pugh (1999). Known seasonality: present all the year. Distribution: cosmopolitan species, inhabiting Diphyes dispar Chamisso and Eysenhardt, 1821 the three great oceans as well as the Antarctic, Arc- (Figs. 132A-C) tic, and Mediterranean (Alvariño, 1971). Meso- pelagic distribution in tropical latitudes, more Polygastric stage: anterior nectophore large, up epipelagic distribution in boreal and austral latitudes to 36.0 mm in height by 18.0 mm in dorso-ventral (Pugh, 1984; Pagès and Schnack-Schiel, 1996), width. Five ridges; dorsal ridge slightly dentate, though it may be found throughout the upper 1.000 dorso-basal tooth larger than the two baso-lateral metres of the water column (Pugh, 1974). teeth. Nectosac cylindrical, the upper portion References: Totton (1965); Pugh (1974, 1984, tapering to a narrow caecal extension ending close 1999); Kirkpatrick and Pugh (1984); Pagès and Gili to the apex of the nectophore. Hydroecial opening (1992). large, square, very deep, reaching to half of nec- tophore height or more. Somatocyst cylindrical, of Genus Diphyes Cuvier, 1817 variable length, but not exceeding the filiform apex of the nectosac, curving dorsally towards the nec- Diphyids with 5 complete longitudinal ridges in tosac until it touches. Basal lamella entire, margin the anterior nectophores and 3 prominent dorsal concave. The dorsal ostial tooth is considerably teeth in general. Deep hydroecium. Posterior nec- larger than the lateral one. Mouth Fig. not divided. tophores, when developed, also with 3 ostial teeth in Posterior nectophore bearing five ridges, height general and a long apical process (apophysis). 27.0 mm, dorso-ventral width 13.0 mm. Prominent Bracts generally helmet-shaped. apical apophysis fitting into the hydroecium of the References: Pagès and Gili (1992); Pugh (1999). anterior nectophore. Hydroecial groove large, bounded ventrally by a flat hook-shaped plate Diphyes bojani (Eschscholtz, 1829) directed towards one of the lateral walls. Tooth at (Figs. 131J-K) basal end of dorsal ridge dentiform, slightly larger than the lateral teeth. Polygastric stage: anterior nectophore elongated Eudoxid: Bract conical, hood-shaped, with a bearing five long, variably serrated ridges converg- large, rounded base. Hydroecium shallow, phyllo- ing at the apex to form a pyramid, pentagonal in cyst cylindrical, narrow, tapering near the tip, not cross-section, 10.0 mm in height by 3.0 mm in reaching the apex of the bract. Gonophore with four dorso-ventral width. Three basal teeth all of the denticulate ridges. Bases of the two dorsal ridges same size. Nectosac cylindrical, reaching nearly to sharp, each of the two ventral ridges terminating in the apex of the nectophore, upper third tapering. a small tooth and joined by an entire basal lamella. Hydroecium deep, extending to about one-third the Records from Mediterranean: eastern and west- height of nectophore, narrower than in D. dispar. ern Mediterranean. Somatocyst fusiform, tip reaching nearly to the apex Known seasonality: 9-12. of the nectosac. Basal lamella entire, bearing a thin Distribution: widely distributed in temperate and median crest. Posterior nectophore with five serrat- warm regions of the three great oceans, and the ed ridges, upper third tapering, forming a prominent Mediterranean (Alvariño, 1971). Species epipelagic, apophysis. Up to 6.6 mm in height by 2.2 mm in occasionally present at greater depths (Pugh, 1974). dorso-ventral width. References: Cervigón (1958); Totton (1965); van Eudoxid: bract shield-shape that covers the upper Soest (1973); Pugh (1974, 1999); Pagès and Gili ventral half of the gonophore, different from that (1992); Lakkis and Zeidane (1995); Gamulin and from all other diphyids. Krisnic (2000).

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Genus Eudoxoides Huxley, 1859 rounded mouth. Bracts helmet-shaped. Shape of phyllocyst generally resembling that of somatocyst Diphyids with small, rigid anterior nectophores, of anterior nectophore; (need of review). spirally twisted or not, with 5 serrated ridges, the References: Pagès and Gili (1992); Pugh (1999). dorsal one being complete. Mouth Fig. divided; no conspicuous ostial teeth. Posterior nectophore, when Lensia campanella (Moser, 1925) developed, with curved furrow between apex and (Fig. 133A-B) pedicel. Reference: Pagès and Gili (1989, 1992); Pugh Polygastric stage: anterior nectophore up to 6.3 (1999). mm in height by 3.0 mm in dorso-ventral width lat- erally compressed. Often twisted due to preserva- Eudoxoides spiralis (Bigelow, 1911) tion. Walls smooth, rounded, bearing five very fine, (Figs. 132D-H) barely discernible ridges, one dorsal, two laterals, and two ventral. Basal lamella slanted upwards Polygastric stage: only one nectophore devel- towards the ventral surface. Hydroecium very flat. oped, spiralled, up to 12 mm in height, consistency Basal lamella short, divided into two halves with firm. Five twisted serrated ridges, but only four at rounded margins. Nectosac large, occupying nearly apex as left ventral ridge joins the right ventral ridge the entire nectophore. Somatocyst ovoid, slanted just below the apex. Bases of ventral ridges dissim- towards the basal lamella, with a short, thin pedun- ilar, in that the right ridge starts from the ventral cle. Pedicular canal moving to the base of the soma- notch in the hydroecium, while the left ridge starts at tocyst. Posterior nectophore not been described. the level of the ostium. Hydroecium deep, carrot- Eudoxid: bract conical with rounded apex, with shaped, with a rounded apex. Bases of the lateral minute hydroecium. Club-shaped phyllocyst. walls of the hydroecium asymmetrical, with sharp Records from Mediterranean: eastern and West- ends. Basal lamella divided into two lanceolate ern Mediterranean. wings, right wing larger than left one somatocyst, Known seasonality: present all the year. carrot-shaped, arising from a tiny peduncle and Distribution: epipelagic (Pugh, 1974) common reaching around the midpoint of the nectosac. in tropical regions of the three great oceans and in Eudoxid: bract hood-shaped about 4.0 mm the Mediterranean (Alvariño, 1971). height, with two serrated ridges and a large, deep References: Totton (1965); Carrè D. (1967); neck-shield. Phyllocyst thick and straight, reaching Carré C. (1968a); Pugh (1974, 1999); Pagès and Gili nearly the apex. Gonophore twisted, with four (1992); Avian et al. (1995); Lakkis and Zeidane slightly dentate ridges, truncated at the summit. (1995); Gamulin and Krsˇinic´ (2000). Records from Mediterranean: eastern and west- ern Mediterranean. Lensia conoidea (Keferstein and Ehlers, 1860) Known seasonality: 3-6, 9,10. (Figs. 133C-E) Distribution: widely distributed in the temperate regions of the three great oceans and the Mediter- Polygastric stage: anterior nectophore up to 20 ranean (Alvariño, 1971; Pugh, 1974). mm high, consistency firm, with five complete References: Cervigón (1958), Totton (1965); ridges converging at an acute apex; basal end of Pugh (1974, 1999); Kirkpatrick and Pugh (1984); dorsal ridge forming a tooth extending to below the Gili (1986); Pagès and Gili (1992); Avian et al. level of the ostium. Basal lamella short, wide, cleft, (1995); Lakkis and Zeidane (1995). extending underneath the nectosac. Hydroecium basal and minute. Somatocyst fusiform and vacuo- Genus Lensia Totton, 1932 lated, reaching the midpoint of the nectosac. Base of basal lamella slanted upwards towards the ven- Diphyids with pyramidal anterior nectophores, tral surface. Posterior nectophore rectangular but generally ridged, number and disposition of the bearing five ridges, up to 20 mm high. Mesogloea ridges being variable, from 5 to many. Small, divid- thick, occupying nearly the entire ventral half of ed mouth, with shallow hydroecium, rarely extend- the nectophore. Basal lamella asymmetrical, with a ing above ostial level. No ostial teeth. Posterior nec- central notch; left lappet somewhat higher than tophore, when developed, truncated apically with a right lappet.

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Eudoxid: bract conical, approximately 4 mm in height. Hydroecium minute, very flat, located below height, with a long, swollen phyllocyst. the level of the ostium. Somatocyst, short, angled Records from Mediterranean: eastern and west- obliquely, exhibiting great morphological variabili- ern Mediterranean. ty, ovate or sausage-shaped, ventrally slanted, with a Known seasonality: present all the year. short peduncle. Basal lamella divided into two Distribution: common and abundant in all seas, rounded, dorsally slanted wings. Posterior nec- and in the Mediterranean (Bigelow and Sears, 1937; tophore difficult to distinguish from that of the other Alvariño, 1971), spanning a broad depth distribution Lensia species but has a rounded notch on the from the surface down to the bathypelagic zone. mouth-Fig.. Eudoxid: not yet discovered. References: Bigelow and Sears (1937); Totton Records from Mediterranean: western Mediter- (1965); Carré D. (1967); Rottini (1971); Palma ranean, Alborán Sea. (1973); Pugh (1984,1999); Kirkpatrick and Pugh Known seasonality: in winter. (1984); Gili (1986); Pagès and Gili (1992); Lakkis Distribution: widely distributed in tropical and Zeidane (1995); Gamulin and Krisnic (2000). regions of the Atlantic Ocean, but distribution range extending from latitude 59° N (Fraser, 1967) to 40° Lensia fowleri (Bigelow, 1911) S. Isolated presence in the Indian and Pacific oceans (Figs. 133F-H) (Alvariño, 1971). Recently cited in the Alborán Sea, near the Strait of Gibraltar (Dallot et al., 1988). Polygastric stage: anterior nectophore high, up to References: Pagès and Gili (1992); Pugh (1999). 20.0 mm in height. Five complete ridges converging at the apex. Lateral ridges curving slightly towards the Lensia meteori (Leloup, 1934) ventral surface at the base. Basal lamella large. (Fig. 134A) Hydroecium extremely flat. Somatocyst ovoid or spherical, resting on the extensive basal lamella, entire- Polygastric stage: anterior nectophore very small ly below the level of the ostium. Basal lamella divided and delicate, apex rounded, apparently without into two wings. Posterior nectophore smaller and deli- ridges, up to 7.0 mm high. Hydroecium narrow, cate. Hydroecium delimited, by two triangular-shaped high, slanting ventrally upwards, basal lamella wings, the small mouthFig. is undivided. Eudoxid: the indistinguishable from ventral surface of hydroeci- bract is elongated, up to 4.5 mm in height, and round- um, divided into two quadrangular wings. Upper ed apically, with a wide neck shield which bears a mar- edge of hydroecium above the level of the ostium. ginal notch. The phyllocyst is small and globular. Somatocyst small, pyriform or globe-shaped, with a Records from Mediterranean: eastern and west- short pedicel. Posterior nectophore and eudoxid ern Mediterranean. have not been described. Known seasonality: present all the year. Records from Mediterranean: eastern and west- Distribution: more frequent and abundant in the ern Mediterranean. Atlantic Ocean but extending into temperate regions Known seasonality: present all the year. of the Pacific and Indian oceans and the Mediter- Distribution: inhabiting temperate regions in the ranean (Bigelow and Sears, 1937; Alvariño, 1971). three great oceans (Alvariño, 1971), and in the Reported at depths down to 800 m (Leloup and Mediterranean (Leloup, 1934; Gili, 1986). Broad Hentschel, 1935) but mainly dwelling in the upper vertical distribution extending down to 800 m in 250 m (Pugh, 1974). depth (Pugh, 1974). References: Totton (1965); Gamulin (1966); Rot- References: Totton (1965); Rottini (1971); tini (1971); Pugh (1974, 1999); Casanova (1980); Daniel (1974); Pugh (1974, 1999); Kirkpatrick and Kirkpatrick and Pugh (1984); Pagès and Gili (1992); Pugh (1984); Gili (1986); Pagès and Gili (1992); Avian et al. (1995); Lakkis and Zeidane (1995). Avian et al. (1995); Carré and Carré (1995); Lakkis and Zeidane (1995); Gamulin and Krsˇinic´ (2000). Lensia hotspur Totton, 1941 (Fig. 133I) Lensia multicristata (Moser, 1925) (Figs. 134B-D) Polygastric stage: anterior nectophore with five complete ridges, lateral ridges closer to dorsal ridge Polygastric stage: anterior nectophore elongate, than to ventral ridges. Small, less than 10.0 mm in up to 15 mm in height, with seven longitudinal

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ridges, latero-ventral ridges reaching neither the References: Cervigón (1958); Totton (1965); apex nor the ostial margin of the nectophore, lateral Pugh (1974, 1999); Ianora and Scotto di Carlo ridges ending slightly above the level of the ostium. (1981); Kirkpatrick and Pugh (1984); Gili (1986); Hydroecium small, as a shallow groove located Pagès and Gili (1992); Avian et al. (1995); Carré below the level of the ostium. Basal lamella wide, and Carré (1995); Lakkis and Zeidane (1995); divided into two wings whose inner margins are Gamulin and Krsˇinic´ (2000). formed by a rounded tooth directed towards the hydroecium. Somatocyst filiform, with an extreme- Lensia subtiloides (Lens and Van Riemsdijk, 1908) ly thin peduncle, reaching nearly the midpoint of the (Figs. 135A-B) nectosac. Posterior nectophore with five ridges, lat- eral ridges not reaching the ostium. Basal lamella Polygastric stage: anterior nectophore 3.7 mm low and broad. Eudoxid not yet discovered, high by 1.4 mm wide, consistency firm with five although Kirkpatrick and Pugh (1984) suggested ridges converging at the apex. Hydroecium very that it might be Eudoxia tenuis (Patriti, 1965). shallow, summit at the same level as the ostium. Records from Mediterranean: Adriatic, eastern Basal lamella slanting upwards towards the ventral (Crete and Ionian Seas) and western Mediterranean. surface. Mouth wide, with two short wings with Known seasonality: present all the year. rounded borders slightly overlapping. Somatocyst Distribution: mesopelagic species (Pugh, 1984) club-shaped, one-third/one-fifth of nectophore distributed in the temperate regions of the three height. Posterior nectophore 3 mm in height with a great oceans, and the Mediterranean (Bigelow and slight apical promontory and a small tooth on the Sears, 1937; Alvariño, 1971). right side of the apex. References: Bigelow and Sears (1937); Totton Eudoxid: bract rounded with club-shaped phyllo- (1965); Rottini (1971); Pugh (1974, 1999); Kirk- cyst. patrick and Pugh (1984); Pugh (1984); Gili (1986); Records from Mediterranean: western Mediter- Pagès and Gili (1992); Lakkis and Zeidane (1995); ranean. Gamulin and Krsˇinic´ (2000). Known seasonality: 12. Distribution: present, though uncommon, in tem- Lensia subtilis (Chun, 1886) perate coastal waters of the three great oceans and (Figs. 134E-G) the Mediterranean (Alvariño, 1971). Frequently col- lected together with Diphyes chamissonis, to which Polygastric stage: anterior nectophore conical, appear to be associated in the Indo-Pacific region fragile, laterally compressed, apex rounded, appar- (Totton, 1954; Pagès et al., 1989). ently devoid of ridges but with folds. Up to 10 mm References: Bigelow and Sears (1937); Totton in height. Hydroecium wide, short, slanting upwards (1965); Daniel (1974); Gili (1986); Pagès and Gili towards the ventral surface, upper edge above the (1992); Lakkis and Zeidane (1995); Pugh (1999). level of the ostium. Somatocyst composed of a long, straight peduncle reaching to the midpoint of the Genus Muggiaea Bush, 1851 nectophore, ending in a globe. Basal lamella small, divided into two wings. Posterior nectophore Diphyids with posterior nectophore not devel- approximately the same size as the anterior nec- oped. Pyramidal anterior nectophore with 5 ridges. tophore, with five ridges, truncate apex, and round- Deep hydroecium, not open ventrally, oblique, ed small basal lamella. divided mouth. Somatocyst lies very close to nec- Eudoxid: bract small and rounded with a short tosac wall. phyllocyst. The gonophore has hydroecial folds only References: Pagès and Gili (1989, 1992); Pugh on the proximal part. (1999). Records from Mediterranean: eastern and west- ern Mediterranean. Muggiaea atlantica Cunningham, 1892 Known seasonality: 1-12. (Figs. 135C-D) Distribution: temperate regions of the three great oceans and the Mediterranean (Alvariño, 1971). Polygastric stage: Nectophore small, up to 7 mm Epiplanktonic, though it may extend down to depths in height, with five complete relatively straight of 500-1000 m (Pugh, 1974; Gili et al., 1987a). ridges converging at the apex. No basal teeth.

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Hydroecium bell-shaped, relatively deep, up to one- Brazil (Leloup and Hentschel, 1935). In the Pacific third of nectophore height, the lower half situated reported in the vicinity of the Galapagos Islands below the level of the ostium. Somatocyst long, fil- (Alvariño and Leira, 1986) and near the Panama iform, running closely along the ventral surface of Canal after entering from the Atlantic (Alvariño, the nectosac, ending in a small thickening at the 1974), Mediterranean. level of the apex of the nectosac. Basal lamella References: Totton (1965); Alvariño (1971, wide, divided into two wings whose medial margins 1974); Rottini (1971); Kirkpatrick and Pugh (1984); overlap. Gili (1986); Pagès and Gili (1992); Lakkis and Zei- Eudoxid: bract small, conical, dorsal surface dane (1995); Pugh (1999); Gamulin and Krsˇinic´ longer than ventral surface. Sutural surface broad, (2000). flattened, suture prominent. Phyllocyst club-shaped. Hydroecial cavity shallow. Gonophore slightly Genus Sulculeolaria Blainville, 1834 twisted, with four ridges running from the base to the apex. Basal lamella short, curved. Diphyids whith anterior nectophore with round- Records from Mediterranean: eastern and west- ed apex, and without ridges; posterior nectophore of ern Mediterranean. similar size with extensively looped lateral radial Known seasonality: 1-12. canals. Replacement nectophores of both types fre- Distribution: neritic species inhabiting warm and quently with different characters. Small leaf-like temperate regions of the three great oceans and the bracts with direct release of gonophores, without Mediterranean (Bigelow and Sears, 1937; Alvariño eudoxid stage. Bracts of various species are not dis- 1971). tinguishable. References: Russell (1938); Totton (1965); References: Carré C. (1979); Pagès and Gili Daniel (1974); Purcell (1982); Kirkpatrick and Pugh (1992); Pugh (1999). (1984); Gili (1986); Gili et al. (1987a), Gili et al. (1987b); Gili et al. (1988); Pagès and Gili (1992); Lakkis and Zeidane (1995); Pugh (1999); Gamulin Sulculeolaria biloba (M. Sars, 1846) and Krsˇinic´ (2000). (Figs. 135G-I) Polygastric stage: anterior nectophore conical, Muggiaea kochi (Will, 1844) without ridges, apex rounded. Firm consistency. Up (Figs. 135E-F) to 20 mm high. Ostial margin devoid of teeth. Radi- al canals with transverse commissures connected to Polygastric stage: nectophore similar to that of the ventral canal nearly at the level of the ostium. M. atlantica, with five ridges converging at the Somatocyst ovoid or filiform, sloping ventrally, one- apex. Up to 7 mm in height. Lateral ridges describ- sixth of nectophore height. Basal lamella divided ing a characteristic sigmoidal curve. Hydroecium into two large, rounded lappets, without protuber- conical, less deep than in M. atlantica, reaching one- ances. Posterior nectophore rectangular, up to 24.6 quarter of nectosac height. Basal lamella divided mm in height. No ostial teeth. Basal lamella consist- into two equal rectangular wings. Somatocyst fili- ing of two lateral lappets and a central mouth, with form, cylindrical, reaching the midpoint of the nec- furrows reaching to half of lamella height; protuber- tosac. ances absent. Eudoxid: the bract is roughly conical, with a Records from Mediterranean: eastern and west- flattened facet, an asymmetrical basal process, ern Mediterranean, Adriatic. and a very shallow hydroecial depression. The Known seasonality: 4. phyllocyst is club-shaped. The gonophores have Distribution: warm, and temperate waters of the four longitudinal ridges. There is a short, curved three great oceans (Alvariño, 1971), and in the mouth. Mediterranean (Gili, 1986). The numerous syn- Records from Mediterranean: eastern and west- onyms used for this species in the past make it diffi- ern Mediterranean. cult to confirm some of the early records, as dis- Known seasonality: 1-12. cussed previously by Totton (1954). Distribution: Atlantic species abundant in neritic References: Carré C. (1979); Kirkpatrick and waters of temperate regions (Alvariño, 1971). In the Pugh (1984); Pagès and Gili (1992); Avian et al. southern hemisphere collected to latitude 23° S off (1995); Lakkis and Zeidane (1995; Pugh (1999).

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Sulculeolaria chuni disappearing in replacement nectophores. Posterior (Lens and van Riemsdijk, 1908) nectophore up to 26.6 mm high. Nectosac with an (Figs. 136A-B) oblique annular constriction affecting the upper dor- sal and lower ventral halves. Ostial margin with two Polygastric stage: anterior nectophore conical, dorsal and two lateral teeth. Basal lamella divided without ridges, apex rounded, consistency more del- into two large, rounded lobes with a central furrow icate than other species of the genus. Up to 8 mm occupying three-fourths of basal lamella length. high. Ostial margin without teeth. Radial canals Each lappet bearing an acute protuberance on the without transverse commissures in the first anterior upper dorsal portion. nectophore, but commissures present in the replace- Records from Mediterranean: eastern and west- ment nectophore. Somatocyst quite straight, filiform ern Mediterranean. or fusiform, up to two-fifths to three-fifths of nec- Known seasonality: present all the year. tophore height. Basal lamella short, divided into two Distribution: widely distributed in tropical and lappets, without protuberances. Posterior nec- subtropical regions in the three great oceans and in tophore cylindrical, up to 8.6 mm in height. No teeth the Mediterranean (Bigelow and Sears, 1937; Alvar- on the ostial margin. Basal lamella divided into two iño, 1971). rounded lappets separated by a shallow medial References: Totton (1965); Alvariño (1981); notch. Secondary posterior nectophore similar. Palma (1973); Carré (1979); Kirkpatrick and Pugh Records from Mediterranean: eastern and west- (1984); Gili (1986); Pagès and Gili (1992); Avian et ern Mediterranean. al. (1995); Lakkis and Zeidane (1995); Pugh (1999); Known seasonality: present all the year, mainly Gamulin and Krsˇinic´ (2000). 4-12. Distribution: common species in equatorial and Sulculeolaria turgida (Gegenbaur, 1853) tropical regions in the three great oceans (Alvariño, (Figs. 136E-F) 1971) and the Mediterranean (Bigelow and Sears, 1937; Carré C., 1979). Polygastric stage: anterior nectophore conical, References: Cervigón (1958); Totton (1965); apex rounded, firm consistency, reaching 15 mm in Rottini (1971); Palma (1973); Carré C. (1979); Iano- height. Ostial margin devoid of teeth. Somatocyst ra and Scotto di Carlo (1981); Gili (1986); Pagès small, ovoid or filiform, one-twentieth of nec- and Gili (1992); Avian et al. (1995); Lakkis and Zei- tophore height. Radial canals without transverse dane (1995); Pugh (1999); Gamulin and Krsˇinic´ commissures in the first nectophore (NA1), but (2000). transverse commissures are present in the replace- ment nectophore (NA2), attached to the ventral Sulculeolaria quadrivalvis Blainville, 1834 canal above the level of the pedicular canal. Basal (Figs. 136C-D) lamella divided into two lappets by a deep furrow reaching to the ostial margin, shorter in NA2. Tooth- Polygastric stage: anterior nectophore conical, like protuberances absent. Posterior nectophore apex rounded, without ridges firm consistency. cylindrical, tapering towards the ostial margin. Up Large, up to 20 mm in height. Ostial margin bearing to 10.0 mm high. No teeth on the ostial margin. two lateral and two dorsal teeth, well-developed, Basal lamella entire, large, rounded, devoid of pro- decreasing in size in the replacement anterior nec- tuberances. tophores. Radial canals with transverse commis- Records from Mediterranean: mainly Adriatic, sures linking the canals to the ventral canal at the eastern and western Mediterranean. level of the lower third of the nectosac. Transverse Known seasonality: 12-9. commissure tending to be smaller in replacement Distribution: uncommon but distributed in tem- nectophores and sometimes not reaching the dorsal perate regions in the three great oceans, and in the canal in the second following nectophore. Somato- Mediterranean (Bigelow and Sears, 1937; Alvariño, cyst elongate, sinuous, ventrally slanted, one-fifth to 1971). Epiplanktonic distribution. two-fifths of nectophore height in size, tending to be References: Totton (1965); Carré (1979); Kirk- straighter in following nectophores. Two prominent, patrick and Pugh (1984); Gili (1986); Pagès and Gili rounded basal lappets, each with a small protuber- (1992); Avian et al. (1995); Pugh (1999); Gamulin ance on the dorsal margin, decreasing in size and and Krsˇinic´ (2000).

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Family HIPPOPODIIDAE Kölliker, 1853 Vogtia glabra Bigelow, 1918 (Figs. 137E-F) Calycophorae with biserial arrangement of up to 16 or more flattened definitive nectophores in vary- Colonies composed of two parallel rows of nec- ing stages of development, the youngest being api- tophores attached obliquely to a central stem. Oldest cal, nectophores fitting tightly together around a thin nectophores placed at the base of the colony. Youngest stem which can be retracted between them; without nectophores elongate, up to 7.3 mm high by 4.6 mm bracts, somatocyst curving smoothly over mid-dor- wide, with a triangular apical process consisting of sal surface of hydroecium and is without central three rounded protuberances, a larger central protuber- organ. ance and two smaller lateral protuberances, halfway Reference: Carré and Carré (1995). along the height of the nectophore. Rete mirabile pre- sent. Deep hydroecial groove from the base of the Genus Hippopodius Quoy and Gaimard, 1827 apex on the ventral surface of the nectophore, protect- ed by lateral wings. Adult nectophore more rounded, Hippopodiid whose larval nectophore nectosac up to 30.0 mm in diameter, horseshoe-shaped. Char- has only two radial canals. acterized by two rounded dorso-lateral processes and References: Pagès and Gili (1992); Pugh (1999). an additional apical process. Hydroecial groove shal- lower; hydroecium large and flattened. Hippopodius hippopus (Forskål, 1776) Records from Mediterranean: eastern and west- (Figs. 137A-D) ern Mediterranean. Known seasonality: 5. Colonies formed by up to 16 nectophores Distribution: widely distributed in the Atlantic arranged in two series opposite each other joined by Ocean from Ireland to Tristan da Cunha (Leloup, a thin central stem. Upper nectophores younger, 1955). Sporadically present in the Pacific and Indi- lower nectophores dropped from the colony as new an oceans and the Mediterranean (Alvariño, 1971). nectophores form at the apex. Definitive nectophore References: Pugh (1974, 1984, 1999); Kirk- hard and tough, horseshoe-shaped, up to 20.6 mm patrick and Pugh (1984); Gili (1986); Pagès and Gili high and 16.0 mm wide. It may become opaque dur- (1992); Lakkis and Zeidane (1995). ing fixation. Four rounded dorsal protuberances variable in size forming an arc above the ostium; the Vogtia pentacantha Kölliker, 1853 two central protuberances smaller. The nectosac is (Fig. 137G) relatively large and a rete mirabile is located on the ventral radial canal, larger in juveniles. Colonies organized like the rest of the hip- Records from Mediterranean: eastern and west- popodiids. Nectophore five pointed, up to 15 mm ern Mediterranean. with small gelatinous teeth on the ridges, but with Known seasonality: present all the year. smooth facets except for occasional protuberances Distribution: widely distributed in tropical and near the central ridge. Nectosac relatively small. subtropical regions in the three great oceans, and in Polygastric stage fragile and seldom found intact in the Mediterranean (Bigelow and Sears, 1937; Alvar- net collections. iño, 1971; Pugh 1974). Records from Mediterranean: southern Adriatic, References: (Bigelow and Sears, 1937); Totton eastern and western Mediterranean (1965); Carré D. (1968a); Rottini (1971); Pugh Seasonality: ? (1974, 1999), Kirkpatrick and Pugh (1984, 1999); Distribution: Atlantic, Mediterranean. Gili (1986); Pagès and Gili (1992); Avian et al. References: Bigelow and Sears (1937); Tré- (1995); Lakkis and Zeidane (1995); Gamulin and gouboff (1957); Rottini (1971); Gamulin and Krsˇinic´ (2000). Krsˇinic´ (2000).

Genus Vogtia Kölliker, 1853 Vogtia serrata (Moser, 1925) (Fig. 137H) Hippopodiid of which the nectosac of larval nec- tophore has 4 radial canals. Nectophore roughly triangular, up to 40 mm in References: Pagès and Gili (1992); Pugh (1999). diameter, with two small flaps at the centre of base.

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Neither the distinctive ridges nor the facets bear Genus Amphicaryon Chun, 1888 spines or protuberances, and a small, deep hollow exist beneath each lateral process. Prayid with two dissimilar nectophores; the larg- Records from Mediterranean: western Mediter- er, witch is possibly the retained larval nectophore, ranean. partly encloses the reduced or vestigial definitive Seasonality:? . nectophore. The nectosac of the latter does not have Distribution: infrequent but inhabiting tropical an external opening. The eudoxid bract has a pair of and subtropical regions in the three great oceans, lateral hydroecial canals. and the Mediterranean (Alvariño, 1971). References: Pagès and Gili (1992); Pugh (1999). References: Bigelow and Sears (1937); Kirk- patrick and Pugh (1984); Pugh (1999). Amphicaryon acaule Chun, 1888 (Figs. 138B-C) Vogtia spinosa Keferstein and Ehlers, 1861 (Fig. 138A) Polygastric stage: colonies globe-shaped, com- posed of two nectophores. Larval nectophore large, Colonies composed of two parallel rows of nec- ovoid, up to 10.7 mm in height, higher than wide, tophores attached obliquely to a central stem. Up to partially surrounding the vestigial nectophore. Larg- 19 nectophores, pentagonal in shape, up to 20 mm in er nectophore has a nectosac somewhat higher than length. Spine-like gelatinous tubercles closely half nectophore height with four radial canals, the spaced on the upper surface of the nectophore. Ven- dorsal canal longer than the ventral canal. Upper tral surface a deep concavity devoid of spines. Nec- portion of lateral canal forming a right angle. Vesti- tosac large, flattened, with four radial canals and a gial nectophore is a disc within the ventral cavity of rete mirabile on the ventral surface. the larger nectophore. Nectosac with four simple Records from Mediterranean: western Mediter- radial canals, not open to the outside. ranean. Eudoxid: small and thin, with two straight canals. Seasonality: ? It is folded to form a shield to the bell-shaped Distribution: infrequent but inhabiting tropical gonophores. and subtropical regions in the three great oceans, Records from Mediterranean: western Mediter- and in the Mediterranean (Alvariño, 1971). ranean. References: Bigelow and Sears (1937); Totton Known seasonality: 9-4. (1965); Pugh (1974, 1999); Kirkpatrick and Pugh Distribution: present in tropical and subtropical (1984); Pugh, 1984; Pagès and Gili (1992). regions of the three great oceans, and of the Mediterranean (Alvariño, 1971; Pugh, 1974). Family PRAYIDAE Kölliker, 1853 Epipelagic species that has been caught in the mesopelagic zone (Pugh, 1974). Nectophores relatively large and usually round- References: Bigelow and Sears (1937); Totton ed, mesoglea abundant; larval nectophore some- (1965); Palma (1973); Daniel (1974); Pugh (1974, times retained during polygastric stage or replaced 1999); Kirkpatrick and Pugh (1984); Pagès and Gili by one to four definitive nectophores, whose soma- (1992). tocysts are often complexly branched; the eudoxid bracts are rounded and unridged. Subfamily PRAYINAE Chun, 1897 References: Carré and Carré (1995); Pugh (1999). Prayid with two, occasionally up to 4, rounded, Subfamily AMPHICARYONINAE Chun, 1888 smooth-walled nectophores of similar size. Bracts with 6 canals, occasionally reduced to 5. Two nectophores differing in size. The larger, References: Carré and Carré (1995); Pugh (1999). rounded one is believed to be the retained larval nec- . tophore. The first definitive one smaller or vestigial. Genus Desmophyes Haeckel, 1888 The bracteal canals are reduced to 2 long hydroe- cials. Bracts undistinguishable at present. Prayid with usually two avoid flimsy, cylindrical References: Carré and Carré (1995); Pugh nectophores but there can be up to 6 biserially (1999). arranged nectophores. Nectosac occupying less than

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half the height of the nectophores; with an ascending References: Carré and Carré (1995); Pugh (1999). but no descending branch to the somatocyst; with Lilyopsis rosea Chun, 1885 four straight radial canals. Somatocyst unbranched (Figs. 139D-F) and with a distinctive whitish swelling at the apex. Bracts small, compact and kidney-shaped, character- Diagnosis: like for the genus ized by the presence of a large white spherical or Records from Mediterranean: western Mediter- ovoid central organ, giving rise to the thin bracteal ranean. canal. Gonophores fragile and reduced. Known seasonality:? References: Pugh and Harrison (1987); Pugh (1992). Distribution: Atlantic; Mediterranean. References: Carré C. (1969b); Carré and Carré Desmophyes annectens Haeckel, 1888 (1995), Pugh and Harbison (1987), Pugh (1999). (Figs. 138D-F) Genus Prayola Carré, 1969 Polygastric stage: large swelling at the distal end of the ascending branch of the somatocyst. Nectosac Prayid with an apposed pair of conoid nec- occupying one-quarter the nectosac height. tophores, whose extensive nectosacs (>half the Eudoxid: bracteal dorsal canal arises centrally height of the nectophore) open dorso-basally. The from an inflated vesicle. Gonophore with two sym- radial canals on the nectosac are slightly curved, metrically arranged mantle canals and without later- suggesting an open S. The very short somatocyst al flaps toward their apices. possesses neither an ascending nor a descending Records from Mediterranean: Villefranche-sur- branch. The bracts have only five bracteal canals, mer. there being no dorsal canal. The gonophores possess Known seasonality:? a hydroecial gutter and two mantle canals of equal Distribution: Atlantic; Mediterranean. length. No special, asexual nectophores are present. References: Pugh and Harbison (1987); Pugh (1992). Reference: Pugh and Harbison (1987).

Desmophyes villafrancae (Carré, 1969) Prayola tottoni Carré 1969 (Figs. 139A-C) (Figs. 140A-D)

Polygastric stage: nectosac occupying two- Polygastric stage: both nectophores conoidal, of third/two-fifth the nectophore height same size, up to 5 mm in height and 4.5 mm in Eudoxid: bracteal dorsal canal arises from the diameter. Pedicular canal almost horizontal. Nec- right hydroecial canal. Gonophore with a single tosac more than half of nectophore height. Radial mantle canal. canals unequal, the ventral short straight the other Records from Mediterranean: Villefranche-sur- slightly curved. Simple and very short superficial mer (western Mediterranean). somatocyst, in both nectophores. Known seasonality: 5. Eudoxid: bracts elliptical, cushion-like, with five Distribution: endemic of Mediterranean Sea. short branched bracteal canals, no dorsal canal. References: Carré C. (1969a); Pugh and Harbi- Gonophore subspherical; pedicular canal vertical son (1987); Pugh (1992). giving rise to two symmetrical mantle canals. Records from Mediterranean: off Villefranche- Genus Lilyopsis Chun, 1885 sur-Mer (western Mediterranean). Known seasonality: 4. Prayid whose polygastric stage has two, possibly Distribution: endemic of the Mediterranean Sea. more very delicate and opposite conoid nectophores References: Carré C. (1969c); Pugh and Harbi- up to 10 mm in height; large nectosacs. Definitive son (1987). nectophore has a bifurcated somatocyst and sinuous lateral canals on the nectosac. Larval nectophore has Genus Rosacea sensu Bigelow, 1911 a simple somatocyst, slightly swollen at its tip, and straight radial canals on the nectosac. Prayid with two medium, rounded nectophores Eudoxid: bract like a cushion, with central origin of with simple somatocyst without side branches. Sinu- dorsal canal. Gonophore with a single mantle canal. ous lateral radial canals on nectosac. Bracts kidney-

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shaped, but with characteristic arrangement of canals. ed at the base of the nectophore, reaching to one the References: Pugh and Harbison (1987); Pagès quarter nectophore height. Radial canals curving and Gili (1992); Pugh (1999. twice to form a horizontal S. Hydroecium ventral, deep, occupying a large part of the central portion of Rosacea cymbiformis (Delle Chiaje 1822) the nectophore without reaching either the apex or (Figs. 140E-F, 141A) the base. Somatocyst simple with descending branch. Polygastric stage: definitive nectophore less Eudoxid: bract kidney-shaped and compact. The rounded, more flattened and elongate than in R. pli- longitudinal bracteal canals are reduced to spurs, cata, up to 17.5 mm high. The two definitive nec- and the dorsal canals raise distal to the spur on the tophores are attached ventrally, one partially sur- left hydroecial canal. The gonophores are simple rounding the other. Hydroecium shallow, compris- and bell-shaped. ing a ventral canal with two faint lateral projections Remark: the nectophores of the two Rosacea extending, dorso-basally, from near the apex to the species can be difficult to tell apart. Generally R. ostium of the nectosac. Nectosac displaced dorsally, cymbiformis lives in shallower depth than R. plicata. small, less than two-fifths of nectophore height, lat- Records from Mediterranean: western Mediter- eral radial canals curving three times, forming a W ranean. from the pedicular canal to the ostial ring canal. Known seasonality: 9. Somatocyst with descending branch as in R. plicata. Distribution: mesopelagic species (Pugh, 1984) Eudoxid: bract less compact than that of R. plicata, widely distributed in the three great oceans and in with the dorsal bracteal canal arising proximal to the the Mediterranean (Alvariño, 1971). spur on the left hydroecial canal. References: Totton (1965); Kirkpatrick and Pugh Records from Mediterranean: Adriatic and west- (1984); Pugh (1984, 1999); Gili (1986); Pugh and ern Mediterranean. Harbison (1987); Pagès and Gili (1992). Known seasonality: 9-5. Distribution: relatively common species, more Family SPHAERONECTIDAE Huxley, 1859 abundant in the Atlantic, taken off the British Isles (Kirkpatrick and Pugh (1984), in the Bay of Biscay Calycophorae that retain the larval nectophore as and off the Azores (Leloup, 1955), also taken in the the only one in the polygastric stage. Mediterranean (Bigelow and Sears, 1937). The References: Carré and Carré (1995); Pugh depth distribution appears to be more epiplanktonic (1999). than that of R. plicata. References: Totton (1965); Daniel (1974); Pur- Genus Sphaeronectes Huxley, 1859 cell (1981); Kirkpatrick and Pugh (1984); Pagès and Gili (1992); Avian et al. (1995); Pugh (1999); With the characters of the family. Gamulin and Krsˇinic´ (2000). References: Pagès and Gili (1992); Pugh (1999).

Rosacea plicata sensu Bigelow 1911 Sphaeronectes bougisi Carré D, 1968 (Figs. 141B-C) (Figs. 141D-E)

Polygastric stage: two types of nectophore, a Polygastric stage: nectophore small, 1.0 mm in temporary larval and a definitive one. Larval nec- height; spheroidal, slightly conical apically. Nec- tophore small, globe-shaped, 4.7 mm in size. Simi- tosac sub spherical, occupying the quasi totality of lar to that of the Hippopodidae, except that the pal- nectophore volume. Velum large, ventral. Pedicular lial canal makes a sharp turn around the central canal virtual, very short, giving rise sagittally to two organ. This nectophore is replaced by two larger radial canals, the ventral short in almost immediate definitive nectophores up to 18.0 mm in height. contact with the marginal canal, the dorsal longer Mesoglea thick but not rigid, and consequently and running up to the apex of the nectosac, the two specimens when preserved and easily deformed, lateral canals are straight, issued from to different hindering identification and creating confusion with points of the nectosac apex, the right one being R. cymbiformis.Nectophores without ridges, globe- located more ventrally than the left one, both con- shaped or cylindrical. Nectosac dome-shaped, locat- nected to the marginal canal. Hydroecium conical,

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symmetrical to the sagittal plan, triangular, small, Eudoxid: bract hemispherical, flat, hydroecium located at the base of the ventral face. Somatocyst indistinct. Phyllocyst fungi form, globular with a without peduncle, vertical, fusiform, at the ventral peduncle of about the same size than body. side of the nectosac. Siphosome with 3 to 4 cormidi- Records from Mediterranean: eastern and west- al buds. ern Mediterranean. Eudoxid: only just detached cormidia known, Known seasonality: present all the year. bract hemispherical with a globulous phyllocyst, Distribution: endemic of the Mediterranean Sea. gastrozooid with a short peduncle. References: Carré (1968e); Ianora and Scotto Di Records from Mediterranean: western Mediter- Carlo (1981); Avian et al. (1995); Gamulin and ranean. Krsˇinic´ (2000). Known seasonality: 7. Distribution: endemic of the Mediterranean Sea. Sphaeronectes gracilis (Claus, 1873, 1874) References: Carré D. (1968 b), Carré C. (1968 d); (Figs. 142E-F) Gili (1986). Polygastric stage: nectophore spheroidal, quite Sphaeronectes fragilis Carré C. 1968 fragile, up to 8.0 mm in height. Nectosac small, (Figs. 141F-G) reaching to half of nectophore height. Four straight radial canals arising from the same point at the apex Polygastric stage: nectophore spheroidal, slight- of the nectosac over which bends the long, narrow, ly cylindrical, with thin walls, fragile, up to 5mm in tubular, hydroecium which runs from the external height. Pedicular canal virtual. Nectosac large up to opening to the pedicular canal at the apex of the nec- 4.5mm, subspherical. Radial canals looped with a tosac. Velum broad. Pedicular canal long, readily secondary loop on the descending branch, their distinguishable. Somatocyst horizontal, short, intersection with dorsal canal in ventral position on fusiform, and curved with a distal swelling, directed the nectosac. Hydroecium conical, symmetrical, in towards the dorsum above the apex of the nectosac. the sagittal plan, not very deep, 2/5 of nectosac Eudoxid: (called diplophysa) bract small and spher- height. Somatocyst vertical on ventral side of nec- ical, with clear basal wings. The phyllocyst is long, tosac with a subspherical thickening and a long obliquely angled and club-shaped. The gonophore is peduncle. a simple bell, thickened towards its apex. Eudoxid: not known. Records from Mediterranean: Adriatic, eastern Records from Mediterranean: eastern and west- and western Mediterranean. ern Mediterranean. Known seasonality: present all the year. Known seasonality: present all the year. Distribution: common in Mediterranean (Trè- Distribution: endemic of Mediterranean Sea. gouboff, 1957; Patriti, 1964; Rottini, 1971; Ianora References: Carré C. (1968e); Avian et al. and Scotto Di Carlo, 1981); in the Atlantic collected (1995); Gamulin and Krsˇinic´ (2000). off the Canary Islands (Chun, 1892) and the British Isles (Kirkpatrick and Pugh, 1984). In the Pacific Sphaeronectes gamulini Carré C. 1966 collected off California (Purcell and Kremer, 1983); (Figs. 142A-D) Chile (Palma, 1977) and Japan. References: Totton (1965); Carré C. (1968e); Polygastric stage: nectophore spheroidal, slight- Carré D. (1969a); Rottini (1971); Palma (1973); ly conical up to 1.5 mm in height and diameter. Nec- Ianora and Scotto Di Carlo (1981); Purcell and Kre- tosac subspherical, 3/4 of the nectophore height. mer (1983); Kirkpatrick and Pugh (1984); Pagès and Pedicular canal short but visible. Right lateral canal Gili (1992); Avian et al. (1995); Lakkis and Zeidane inserted slightly above left radial canal. Radial (1995); Pugh (1999); Gamulin and Krsˇinic´ (2000). canals looped, their intersection with dorsal canal in the ventral position on the nectosac. Hydroecium Sphaeronectes irregularis (Claus, 1873) conical relatively deep, laterally flattened, 1/2 nec- (Fig. 142G) tosac height, on the left of the sagittal plan. Somato- cyst horizontal, on the right lateral ventral side of Polygastric stage: nectophore spheroidal slightly the nectosac, with a terminal ovoid thickening and a conical, up to 7.1 mm in height and 5.7 mm in diam- distinct stalk of the same size eter. The radial canals are looped, their intersection

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in the ventral part of the nectosac. Nectosac the 2/3 1. With conical aboral adhesive organ; a nerve ring; of nectophore height. Pedicular canal virtual. two aboral amphicoronate rings of tentacles; Hydroecium conical laterally flattened, not very gonochoric; without brood pouch deep, 1/3 of nectophore height. Somatocyst pyri- (i.e. subumbrellar cavity)...... Halammohydridae form not pedunculate, vertical on the ventral side of – No aboral adhesive organ; no nerve ring; one the nectosac. marginal ring of tentacles of two kinds, adhesive Eudoxid: hemispherical, slightly conical. Phyllo- and armed ones; with or without a brood pouch cyst ovoid to piriform with a very short peduncle, (i.e. subumbrellar cavity); hermaphroditic, length less than 1/2 of the bract height. Hydroecium viviparous ...... Otohydridae not well developed, basal wing not very distinct. Records from Mediterranean: eastern and west- Family HALAMMOHYDRIDAE Remane 1927 ern Mediterranean. Known seasonality: present all the year. Body as a long gastric tube (manubrium) with a Distribution: Mediterranean, Pacific. terminal mouth, with a small aboral cone, separated References: Trégouboff (1957); Avian et al. from manubrium by a neck, bearing an adhesive (1995); Lakkis and Zeidane (1995); Gamulin and organ; aboral nerve ring; one aboral whorl of amph- Krsˇinic´ (2000). icoronate solid tentacles, alternating with ecto-endo- dermic statocysts; gonochoric; without brood pouch. Class AUTOMEDUSA Lameere, 1920 References: Thiel (1988); Bouillon and Boero emend. (see Bouillon and Boero 2000). (2000). (Actinulidae, Narcomedusae, Trachymedusae) Genus Halammohydra Remane, 1927 Subclass ACTINULIDAE Swedmark and Teissier, 1959 With the characters of the family. References: Swedmark (1956, 1957); Clausen Free living, solitary, minute (up to 1.5-2 mm) (1967, 1971); Swedmark and Teissier (1958 a and members of the interstitial fauna of marine sand, b); Laccasagne (1968b). resembling “actinuloid” larvae (e.g. Solmundella larvae); umbrella present or reduced; manubrium, or 1. 14 tentacles and 7 statocysts...... H. octopodides gastric tube, elongated, terminating into a simple – up to 28 tentacles and 12 statocysts ...... mouth-opening; without canal system; with or with- ...... H. schulzei out a cone-shaped aboral adhesive organ formed by incurved ectoderm; with one or two amphicoronate Halammmohydra octopodides Remane, 1927 rings of solid tentacles, either aboral or marginal; (Fig. 143A) with or without brood chamber (= remains of sub- umbrellar cavity); sexual cells in the endoderm of Hallammohydra usually with up to 14 amph- the manubrium wall; free ecto-endodermal stato- icoronate tentacles and 7 statocysts, tentacles with- cysts similar to those of the Trachy- and Narcome- out large basal thickening; one unique gonad; body dusae, inserted between adjacent tentacles; body 0.3 to 0.4 mm high. covered by flagella; direct development and no clas- Records from Mediterranean: Adriatic. sical planula-like stage, embryonic development Seasonality: ? giving rise to halhydrula larvae; no asexual repro- Distribution: Cosmopolitan. duction; cnidome containing either stenoteles or References: Salvini-Plauwen (1966); Thiel microbasic mastigophores and, among others, atric- (1988); Avian et al. (1995). hous anisorhizas and two particular cnidocysts: spirotele and aspirotele spironemes. Halammohydra schulzei Remane, 1927 Distinctive Automedusa features: statocyst struc- (Figs. 143B-D) ture, embryonic development, formation of the brood chamber (subumbrellar cavity) by means of a Halammohydra with usually 28 amphicoronate circular invagination around the manubrium. tentacles (sometimes up to 32) and 12 statocysts; References: Swedmark and Teissier (1966); Lac- tentacles with a large basal thickening; generally cassagne (1968a). two opposite gonads; body 0.7 to 0.8 mm high.

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Records from Mediterranean: Adriatic, western larvae parasitizing other medusae, polychaetes, or fish- Mediterranean. es; those primary larvae by successive budding give Seasonality: ? rise to numerous juvenile medusae or to secondary lar- Distribution: Cosmopolitan. vae which transform later on into juvenile medusae. References: Salvini-Plauwen (1966); Thiel They may also develop more complicate structures (1988); Avian et al. (1995). (stolo-prolifers) which give rise to numerous medusae, representing perhaps the first step to colony formation Family OTOHYDRIDAE and modular life. All medusa buds never develop Swedmark and Teissier, 1958 through a medusary nodule. Longitudinal axis of the larvae and adults correspond to the transversal planula Umbrella ovoid, containing the manubrium; one axis (in the other medusae those axes coincide). Mar- ring of marginal tentacles of two kinds: adhesive ginal sense organs as free ecto-endodermal statocysts and armed ones; with one whorl of statocysts; with (only one species with closed ecto-endodermal stato- or without a brood pouch (= subumbrellar cavity); cysts). With or without otoporpae. Cnidome: atrichous hermaphroditic, viviparous. and apotrichous isorhizae. References: Swedmark and Teissier (1958 a and References: Uchida (1928); Bouillon (1987, c); Clausen (1971); Laccasagne (1973); Bouillon 1999); Bouillon and Barnett (1999); Bouillon and and Boero (2000). Boero (2000).

Genus Otohydra Swedmark and Teissier, 1958 1. Without manubrium pouches ...... Solmarisidae – With manubrium pouches ...... 2 With the characters of the family. 2. Pouches perradial...... Cuninidae – Pouches interradial...... Aeginidae Otohydra vagans Swedmark and Teissier, 1958c (Figs. 143E-F) Family AEGINIDAE Gegenbaur, 1857 (sens em. Maas, 1904) Otohydridae with brood pouch, with up to 24, usually 12-16 tentacles; 8 to 12 statocysts; body Narcomedusae with interradial divided manubri- 0.35 mm long. al pouches containing the gonads; with or without Records from Mediterranean: Adriatic. peripheral canal system. With perradial primary ten- Seasonality: ? tacles living umbrella between marginal pouches, in Distribution: Atlantic, Mediterranean. number at least half than manubrial pouches; with or References: Swedmark and Teissier (1958c); without secondary tentacles on umbrella margin. Thiel (1988); Avian et al. (1995). Pouches extending beyond the point of origin of pri- mary tentacles. With or without otoporpae. Subclass NARCOMEDUSAE Haeckel, 1879 References: Bouillon (1999); Bouillon and Bar- nett (1999); Bouillon and Boero (2000). Umbrella usually flattened, with a central lens- shaped mass of mesoglea and much thinner rim. 1. With only 2 tentacles...... Solmundella Umbrellar margin lobed, divided by peronial grooves. – With 4 or more tentacles ...... 2 Tentacles solid, inserted on exumbrella at some dis- 2. With 8 (or more) tentacles and twice as many tance from margin, just above peronial grooves, with- manubrial pouches; with secondary tentacles..... out tentacular bulbs, their endodermal core in contact ...... Aeginura* with the manubrial endoderm passing through the – With 4-6 tentacles; 4-6 peronia and 8-12 mesoglea of the umbrella as a “root”; sometimes small manubrial pouches ...... Aegina secondary tentacles on margin. Manubrium very broad and short, with entire circular periphery or with perra- *not present in the Mediterranean. dial or interradial peripheral pouches. Generally with- out radial canals; circular canal absent or looped into Genus Aegina Eschscholtz, 1829 the marginal flaps to form a “peripheral canal system”. “Gonads” on manubrium and/or on manubrial pouch- Aeginidae with typically 8 primary manubrial es. Medusa with direct development or with tentacled pouches, occasionally 10 to 12; with peripheral

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canal system; with typically 4, occasionally 5 or 6, Records from Mediterranean: eastern and west- marginal primary tentacles; without secondary ten- ern Mediterranean; Adriatic. tacles; without otoporpae. Known seasonality: 1-12. Distribution: Atlantic, Indo-Pacific, Mediter- Aegina citrea Eschscholtz, 1829 ranean, Antarctic. (Fig. 144A) References: Babnik (1948); Trégouboff (1957); Kramp (1961); Goy (1973b); Castello i Tortella Umbrella up to 50 mm, hemispherical, mesoglea (1986); Gili (1986); Benovic and Bender (1986, rigid, thick at the apex, thinner toward periphery; 1987); Brinckmann-Voss (1987); Goy et al. (1991); velum well developed; manubrium large, circular Boero and Bouillon (1993); Avian et al. (1995); and flattened, lower portion conical, usually with 8 Benovic and Lucic (1996); Medel and López- rectangular gastric pouches, occasionally with 10- González (1996); Gili et al. (1998); Bouillon 12, some or all may have slight medium clefts or (1999); Bouillon and Barnett (1999). notches; mouth simple circular; peripheral canal system present; gonads on manubrial pouches some- Family CUNINIDAE Bigelow, 1913 times extending to manubrium; 4 solid tentacles emerging at upper end of the 4 peronia in deep fur- Narcomedusae with perradial and undivided rows; no secondary tentacles; 4 lappets with numer- manubrial pouches; with or without peripheral canal ous statocysts, 2-20 per lappet; no otoporpae; 5 or 6- system; with tentacles living umbrella opposite centre rayed specimens occur frequently. of each manubrial pouch and thus equal in number to Records from Mediterranean: western Mediter- that of the pouches; pouches not extending beyond ranean. point of origin of tentacles; with or without otoporpae. Known seasonality: 4-5. References: Bouillon (1999); Bouillon and Bar- Distribution: Atlantic, Indo-Pacific, Mediter- nett (1999); Bouillon and Boero (2000). ranean, Antarctic, Arctic. References: Kramp (1961); Arai and Brinck- 1. Without otoporpae ...... Solmissus mann-Voss (1980); van der Spoel and Bleeker – With otoporpae ...... Cunina (1988); Carré D. et al. (1989); Larson et al. (1991); Bouillon (1995b, 1999); Gili et al. (1998); Bouillon Genus Cunina Eschscholtz, 1829 and Barnett (1999). Cuninidae with otoporpae, with or without Genus Solmundella Haeckel, 1879 peripheral canal system.

Aeginidae with 8 manubrial pouches; without 1. With peripheral system; manubrial pouches wide peripheral canal system; with 4 peronia but only 2 and quadratic, more than twice as wide as the long tentacles; without secondary tentacles; without septa between them...... C. globosa otoporpae. – Without peripheral canal system...... 2 2. Manubrium on a broad conical gastric peduncle; Solmundella bitentaculata 9-14 manubrial pouches; up to 57 mm wide...... (Quoy and Gaimard, 1833) (Figs. 144B, 148F) ...... C. proboscidea – Without peduncle...... 3 Umbrella up to 12 mm wide, usually much 3. With 4 manubrial pouches and primary tentacles smaller, rounded apex, keel-shaped along the axis ...... C. simplex leading to tentacles, apical mesoglea very thick, lat- – With (7-9) usually 8 manubrial pouches and eral walls thin; velum well developed; manubrium primary tentacles...... C. octonaria short, lenticular, with 8 rectangular manubrial pouches with rounded edges; mouth circular simple; Several doubtful and unrecognisable species of 2 long, tapering, opposite tentacles issuing from the genus Cunina have been described from the umbrella above manubrium, near apex; gonads in Mediterranean waters namely C. lativentris Gegen- subumbrellar wall, under manubrial pouches; 4 per- baur, 1857 = probably C. globosa; C. polygonia onia in deep grooves; no peripheral system or oto- (Haeckel, 1879); C. vitrea, Gegenbaur, 1857 juve- porpae; 8-32 statocysts. nile = C. proboscidea.

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Cunina globosa Eschscholtz, 1829 beyond velar opening; with a large gastric peduncle; (Figs. 144C-D) 9-14 manubrial pouches, long, rectangular, separat- ed by narrow spaces; peripheral canal system degen- Umbrella up to 18 mm wide; conical or almost erated; tentacles very short; marginal lappets blunt- globular; mesoglea thick; manubrium circular on a ly rounded, each with 3-4 statocysts, otoporpae, broad gastric peduncle; up to 10-14 manubrial short, club-shaped. pouches, wide and quadratic, more than twice as Hydroid: Complex development in the manubri- wide as the septa between them; 10-14 relatively um of the mother medusae and afterwards in the short tentacles, issuing from the centre of the bases manubrial cavity of Geryonia (Trachymedusae) (see of the manubrial pouches at a short distance only Bouillon, 1987). above the umbrella margin, no ectodermal pads Records from Mediterranean: western Mediter- below tentacles bases; peripheral canals well devel- ranean. oped; marginal lappets short and broad with 3 stato- Known seasonality: 3, 9. cysts; otoporpae short and oval. Distribution: Mediterranean. Records from Mediterranean: western Mediter- References: Ranson (1936); Kramp (1961); ranean. Bouillon (1987); Boero and Bouillon (1993). Known seasonality: 4, 6; 7. Distribution: Atlantic, Indo-Pacific, Mediter- Cunina simplex Gili, Bouillon, Pagès, ranean. Palanques, Puig and Heussner, 1998 References: Kramp (1961); Gili (1986); Bouillon (Fig. 145D-E) (1987,1999); Pagès et al. (1992); Boero and Bouil- lon (1993); Medel and López-González (1996); Gili Umbrella higher than a hemisphere, almost glob- et al. (1998); Bouillon and Barnett (1999). ular, 3.7 mm wide and 2.8 mm high; mesoglea thick, manubrium large, circular with 4 small, perradial, Cunina octonaria McCrady, 1859 tongue-shaped, undivided manubrial pouches nar- (Figs. 144E, 145A, 149A-H) rowing in width from base outwards; septa between pouches very wide; with 4 primary tentacles living Umbrella 5-7 mm wide, somewhat flatter than a umbrella opposite centre of each stomach pouch; hemisphere, usually 8 (7-9) square manubrial with 4 peronia; without secondary tentacles on pouches, very close together; no peripheral canals; umbrella margin; gonads on manubrium and tentacles project about midway between margin and manubrial pouches walls; with a narrow peripheral apex, a thick and broad ectodermal pad below base canal system; marginal lappets rectangular, large of each tentacle; with 2-5 generally 3 statocysts on each with 3 small, circular, otoporpae and 1-2 stato- each marginal lappet; otoporpae small; larvae devel- cysts per quadrant. oped in manubrium or attached to the medusae. Records from Mediterranean: western Mediter- Reproduction: development through a secondary ranean. larval structure or a “stolon prolifer”. Known seasonality: 4. Records from Mediterranean: eastern and west- Distribution: endemic of the Mediterranean Sea. ern Mediterranean. References: Gili et al. (1998). Known seasonality: 2, 3, 6, 8-12. Distribution: Atlantic; Indo-Pacific; Mediter- Genus Solmissus Haeckel, 1879 ranean. References: Kramp (1961); Schmidt (1973, Cuninidae without otoporpae, without peripheral 1976); Lakkis and Zeidane (1985); Goy et al. (1988, canal system. 1990, 1991); Bouillon (1987); Boero and Bouillon References: Bouillon (1999); Bouillon and Bar- (1993). nett (1999).

Cunina proboscidea E. and L. Metschnikoff, 1871 1. Exumbrella with numerous gelatinous warts or (Figs. 145B-C) discoid cnidocysts patches; manubrial pouches pentagonal; umbrella up to 50 mm wide; Umbrella up to 57 mm wide, somewhat conical; maximum number of tentacles 16; 5-8 manubrium long, conical, mouth often projecting statocysts per marginal lappet ...... S. albescens

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– Exumbrella smooth; manubriual pouches oval; Seasonality: ? umbrella up to 100 mm wide; number of Distribution: Atlantic, Indo-Pacific, Mediter- tentacles 20-40; 2-5 statocysts per marginal ranean?. lappet...... S. incisa References: Ranson (1936); Russell (1953); Kramp (1961); Arai and Brinckmann-Voss (1980); Solmissus albescens Gegenbaur, 1857 Larson et al. (1991); Boero and Bouillon (1993). (Figs. 146A-B) Remarks: S. incisa is closely related to S. albescens, Ranson (1936) suggested that S. incisa is Umbrella up to 50 mm in diameter; central part merely a giant form of S. albescens. of umbrella doubly convex, lenticular; bell collar thin, flexible, contractile; exumbrella scattered Family SOLMARISIDAE Haeckel, 1879 either with small but distinct gelatinous warts and/or with flat discoid or elongated cnidocyst patches Narcomedusae without manubrial pouches, the which may be found only on the lappets; velum periphery of the manubrium being circular and broad; manubrium large, circular with 14-16 mar- unbroken; with or without peripheral canal system; ginal perradial pouches, pentagonal in shape and gonads on manubrial wall or on manubrial wall somewhat wider than long, their outer angles lying diverticula; with numerous tentacles living umbrella under the tentacle roots; with wide mouth opening; at level of periphery of the manubrium. With or with 14 -16 tentacles nearly as long as the umbrella without otoporpae. diameter, tapering and not very flexible; about 14-16 References: Bouillon (1999); Bouillon and Bar- marginal lappets, rectangular but with rounded nett (1999); Bouillon and Boero (2000). angles on their outer margin, each with 5-8 stato- cysts; gonads developed in the subumbrellar ecto- 1. With peripheral canal system; with otoporpae.... derm of manubrium and manubrial pouches...... Pegantha Records from Mediterranean: eastern and west- – Without peripheral canal system; without ern Mediterranean. otoporpae...... Solmaris Known seasonality: 1-12. Distribution: endemic of the Mediterranean Sea. Genus Pegantha Haeckel, 1879 References: Trégouboff (1957); Kramp (1961); Berhaut (1970); Goy (1973b); Gili (1986); Benovic Solmarisidae with gonads forming diverticula of and Bender (1987); Goy et al. (1988, 1990, 1991); margin of oral manubrium wall; with peripheral Mills and Goy (1988); Boero and Bouillon (1993); canal system; with otoporpae. Avian et al. (1995); Benovic and Lucic (1996); Medel and López-González (1996); Mills et al. 1. Exumbrella with deep radiating furrows from (1996); Gili et al. (1998), Osborn (2000). tentacles to apex, surrounded by ribs and supplementary ridges...... P. triloba. Solmissus incisa (Fewkes, 1886) – Exumbrella smooth; peripheral canals narrow (Figs. 146C-D) throughout their length; with 12-16 marginal lappets ...... P. rubignosa Umbrella up to 100 mm wide, flat, disk-like, with thin and flexible margin, mesoglea fairly thick but soft Two other Pegantha species, P. mollicina and fragile, exumbrella smooth; velum well developed; (Forskäl, 1775) and P. zonaria (Haeckel, 1879) have manubrium large, circular, covering subumbrella sur- been described from the Mediterranean waters but face; 20 to 40 perradial manubrial pouches, oval in out- are considered as unrecognisable species (see line, usually somewhat longer than wide, septa Kramp, 1961). between them alternating with tentacle roots; 20-40 marginal tentacles, stiff, tapering, up to slightly longer Pegantha rubiginosa (Kölliker, 1853) than diameter of umbrella; no peripheral canal system; (Figs. 147A-B) gonads?; marginal lappets rectangular, about as long as broad, each with 2-5 statocysts, no otoporpae. Umbrella up to about 16 mm wide, dome- Records from Mediterranean: western Mediter- shaped, mesoglea very thick, smooth, with 12-16 ranean marginal lappets, rectangular with rounded corners,

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each with 4-6 statocysts; the two middle otoporpae 1. With 6-8 statocysts on each marginal lappet; up long and narrow, frequently longer than the lappet, to 35 mm wide; with 18-20 tentacles...... the lateral ones shorter; peripheral canals very nar- ...... S. solmaris row throughout their length; gonads without radial – With 1-4 statocysts on each marginal lappet ... 2 diverticulae. 2. Umbrella less than 7 mm wide when adult...... Development through two sexual generations ...... S. leucostyla and a “stolon prolifer”. – Umbrella more than 7 mm wide when adult ... 3 Records from Mediterranean: eastern and west- 3. Umbrella 12-15 mm wide; with 30-36 or more ern Mediterranean. tentacles and lappets ...... S. corona Known seasonality: 1-12. – Umbrella 15-23 mm wide; with 12-17 tentacles Distribution: Atlantic; Indo-Pacific; Mediter- and lappets ...... S. flavescens ranean. References: Kramp (1957b, 1959, 1961); Goy Solmaris vanhoeffeni Neppi and Stiasny, 1911 (1973b); Schmidt (1976); Bouillon (1987); Boero has been described from the Adriatic Sea, this and Bouillon (1993); Avian et al. (1995); Goy species is considered by Thiel (1936) as conspecific (1997). with S. flavescens and Kramp (1961) regards it as a juvenile stage of some other species. Pegantha triloba Haeckel, 1879 (Figs. 147C, 148G) Solmaris corona (Keferstein and Ehlers, 1861) (Figs. 147D-E) Umbrella up to 30 mm wide, hemispherical; mesoglea very rigid, apex somewhat flattened; Umbrella 12-15 mm wide, lens-shaped, with exumbrella with deep radiating furrows from ten- thick mesoglea; manubrium circular covering all tacles to near apex, surrounded by ribs and sup- lower surface of upper half of umbrella; gonads plementary ridges; velum broad; manubrium cir- forming a broad ring on outer part of subumbrellar cular, broad; mouth simple, circular; 12-16 tenta- manubrium wall; with 30-36 or more marginal ten- cles somewhat longer than umbrella diameter; 12- tacles and marginal lappets, lappets rectangular up 16 marginal lappets ovate, with sharp pointed to twice as long as broad, usually with 2 (1-4) stato- end, each with up to 20 statocysts; gonads adher- cysts mounted on large cushion, with long bristles. ing to base of manubrium consisting in central Records from Mediterranean: western Mediter- sacs with variously subdivided lobes projecting ranean. into each lappet cavities; otoporpae long tapering Known seasonality: 7. outwards. Distribution: Atlantic; Indo-Pacific; Mediter- Development through primary larvae with eight ranean. capitate tentacles budding of successive medusa References: Russell (1953); Trégouboff (1957); buds and finally metamorphosing himself in Kramp (1961); Boero and Bouillon (1993). medusae. Records from Mediterranean: western Mediter- Solmaris flavescens (Kölliker, 1853) ranean. (Figs. 148A-C) Known seasonality: 5. Distribution: Atlantic, Indo-Pacific, Mediter- Umbrella 15-23 mm wide, thick, lens-shaped, ranean. mesoglea of central umbrellar disk lenticular and References: Vanhöffen (1913); Kramp (1961); quite thick, lateral sides thin; velum large; manubri- Schmidt (1973); Winkler (1982); Bouillon (1987); um flat and lenticular; gonads in the subumbrellar Pagès et al. (1992). floor of the manubrial margin; with 12-17 (usually 13-15) long, stiff, marginal tentacles at right angles Genus Solmaris Haeckel, 1879 to the umbrellar sides and as many marginal lappets and peronia; marginal lappets thin, quadrate, each Solmarisidae without peripheral canal system; with 2- 4 statocysts. without otoporpae, with simple annular gonads. Records from Mediterranean: western Mediter- References: Bouillon (1999); Bouillon and Bar- ranean; Adriatic. nett (1999). Known seasonality: 1-5, 9-12.

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Distribution: Atlantic; Indo-Pacific; Mediter- with or without gastric peduncle. “Gonads” usual- ranean. ly on radial canals. Without polyp stage; a differ- References: Trégouboff (1957); Kramp (1961); entiated planula stage is lacking in a number of Gili (1986); Brinckmann-Voss (1987); Bouillon et Trachymedusae, the gastrula developing immedi- al. (1988a); Boero and Bouillon (1993); Avian et al. ately into young medusae, in others, the planula (1995); Medel and López-González (1996); Goy stage is retained and gives rise to a post-embryon- (1997). ic tentacled larval stage before transforming into medusae. No adult or larval asexual budding Solmaris leucostyla (Will, 1844) observed. Marginal sense organs as free sensory (Fig. 148D) clubs exceptionally enclosed in the mesoglea or in the velum. Cnidome: generally stenoteles associ- Umbrella 3-7 mm wide, flat to hemispherical; ated with microbasic euryteles or/and atrichous velum small; 12-26 slender tentacles and as many isorhizae. marginal lappets; the lappets quadratic, each with References: Uchida (1928); Bouillon (1999); usually one statocysts (1-3); perhaps a variety of S. Bouillon and Barnett (1999); Bouillon and Boero flavescens. (2000). Records from Mediterranean: western Mediter- ranean; Adriatic. 1. With centripetal canals ...... Geryoniidae Known seasonality: 1-12. – Without centripetal canals...... 2 Distribution: endemic of Mediterranean Sea. 2. With broad, circular manubrium and broad References: Trégouboff (1957); Kramp (1961); radial canals ...... Halicreatidae Berhaut (1970); Goy (1973b); Castelló i Tortella – Manubrium and radial canals narrow...... (1986); Gili (1986); Benovic and Bender (1987); ...... Rhopalonematidae Bouillon (1987); Boero and Bouillon (1993); Avian et al. (1995); Medel and López-González (1996); Family GERYONIIDAE Eschscholtz, 1829 Mills, et al. (1996). Trachymedusae with gastric peduncle; 4-6 radial Solmaris solmaris (Gegenbaur, 1857) canals (sometimes more); with centripetal canals; (Fig. 148E) gonads on radial canals, flattened and leaf-shaped; 2 kinds of marginal tentacles, solid and hollow; ecto- Umbrella 25-35 mm wide, flat, lenticular; conca- endodermal statocysts enclosed in mesoglea. vo-convex; 18-20 long tentacles; marginal lappets References: Bouillon (1999); Bouillon and Bar- quadratic, each with 6-8 statocysts nett (1999); Bouillon and Boero (2000). Records from Mediterranean: western and cen- tral Mediterranean. 1. With 6 radial canals, six gonads, mouth with six Known seasonality: 3, 5. lips ...... Geryonia Distribution: endemic of Mediterranean Sea. – Usually with 4 radial canals and gonads References: Trégouboff (1957); Kramp (1961); (sometimes more), mouth with four lips...... Gili (1986); Boero and Bouillon (1993); Medel and ...... Liriope López-González (1996). Genus Geryonia Péron and Lesueur, 1810 Subclass TRACHYMEDUSAE Haeckel, 1866 Geryoniidae with six lips; six radial canals and Medusa with hemispherical or deep bell- six gonads. shaped umbrella. Margin entire with a thickened peripheral cnidocyst ring. Radial canals and circu- Geryonia proboscidalis (Forskäl, 1775) lar canal present. Velum often with heavy muscu- (Figs. 150A-C) lature. With solid marginal tentacles or with a mix- ture of solid and hollow ones, without true tentac- Umbrella 35-80 mm wide, almost hemispherical; ular bulbs, with endodermal cores continuing in manubrium small, on long, conical, gastric pedun- the mesoglea of the umbrella as short “roots”. cle; mouth with 6 simple lips; with six radial canals; With or without centripetal canals. Manubrium up to 7 centripetal canals between each radial

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canals; gonads heart-shaped, very broad above; 6 Family HALICREATIDAE Fewkes, 1886 long, perradial hollow tentacles with cnidocyst rings and 6 small, solid interradial tentacles with adaxial Trachymedusae with wide, circular manubrium; cnidocyst clusters; 12 statocysts. mouth circular, without distinct lips; without pedun- Records from Mediterranean: eastern and west- cle; without centripetal canals; with 8 or more broad ern Mediterranean; Adriatic. radial canals; with numerous marginal tentacles of Known seasonality: 1-3, 6-8, 11, 12. different size, but all structurally alike and arranged Distribution: Atlantic, Indo-Pacific, Mediter- in single series; each marginal tentacle with flexible ranean. proximal portion and stiff spine-like distal portion; References: Kramp (1961); Berhaut (1970); Goy with free ecto-endodermal statocysts. (1973b); Brinckmann-Voss (1987); Goy et al. (1988, References: Bouillon (1999); Bouillon and Bar- 1990, 1991); Boero and Bouillon (1993); Avian et nett (1999); Bouillon and Boero (2000). al. (1995); Benovic and Lucic (1996); Medel and López-González (1996). 1. With about 16 or more radial canals ...... Halitrephes Genus Liriope Lesson, 1843 – With 8 radial canals...... Haliscera

Geryoniidae with four lips; usually four radial Genus Haliscera Vanhöffen, 1902 canals and four gonads, sometimes more. Halicreatidae with 8 radial canals; with a contin- Liriope tetraphylla uous row of marginal tentacles; without papillae on (Chamisso and Eysenhardt, 1821) the exumbrella. (Figs. 150D-I) 1. Umbrella hemispherical, with evenly rounded Umbrella 10-30 mm wide, hemispherical, apex and fairly thin walls; gonads close to apex somewhat flattened; mesoglea thick, rigid; manubrium; six tentacles in each octant ...... velum broad; manubrium small, on long, cylin- ...... H. racovitzae. drical gastric peduncle, longer than umbrellar – Umbrella with very thick dome-shaped apex; diameter; mouth with 4 simple lips boarded with gonads well separated from manubrium, eight to cnidocysts; with normally 4 radial canals (some- twelve tentacles in each octant...... 2 times more); 1-7 centripetal canals in each quad- 2. Umbrella with distinct conical apical projection; rant; with marginal cnidocyst ring; typically 4 64-72 marginal tentacles in adult ...... H. conica long hollow perradial tentacles with cnidocyst – Umbrella with very thick, hemispherical apex, rings and 4 small solid interradial tentacles with about 96 marginal tentacles in adult ...... adaxial cnidocyst clusters; with gonads variable ...... H. bigelowi in shape and size, generally heart-shaped, on either side of the middle of radial canals; 8 sta- Haliscera bigelowi Kramp, 1947 tocysts. (Figs. 151A-B) Records from Mediterranean: eastern and west- ern Mediterranean; Adriatic; Black Sea. Umbrella 15-19 mm wide, 9-10 mm high, Known seasonality: 1-12. almost hemispherical, umbrella with a very thick Distribution: Atlantic, Indo-Pacific, Mediter- dome-shaped mesogleal apex comprising about ranean. 2/3 of the umbrella height, mesoglea thin at sides References: Kramp (1961); Berhaut (1969, and margin; velum very broad; manubrium 1970); Goy (1973b); Castelló i Tortella (1986); broad, flat, slightly conical; mouth simple, circu- Gili (1986); Benovic and Bender (1987); Brinck- lar; 8 straight, broad radial canals and broad cir- mann-Voss (1987); Zamponi and Genzano (1988); cular canal; in adults, about 12 solid marginal Scemes and McNamara (1991); Boero and Bouil- tentacles in each octant, flexile proximally, stiff lon (1993); Avian et al. (1995); Benovic and distally; the base of each tentacles surrounded by Lucic (1996); Desouza et al. (1996); Medel and a small thickening of marginal cnidocyst tissue; López-González (1996); Mills et al. (1996); Goy with 8 gonads broadly oval, flat, about 2/5 as (1997). long as the radial canals, situated slightly nearer

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the manubrium than to bell margin; 3 statocysts Genus Halitrephes Bigelow, 1909 in each octant. Records from Mediterranean: western Mediter- Halicreatidae with 16 or more radial canals; with ranean; Adriatic. a continuous row of tentacles; without papillae on Known seasonality: 1, 5, 7, 12. exumbrella. Distribution: Atlantic; Indo-Pacific, Mediter- ranean; Arctic. Halitrephes maasi Bigelow, 1909 References: Kramp (1961); Naumov (1960- (Fig. 151F) 1969); Schmidt and Benovic (1977); Gili (1986); Boero and Bouillon (1993); Avian et al. (1995); Umbrella up to 100 mm wide, low, rounded, Medel and López-González (1996); Gili et al. smooth, without exumbrella papillae; mesoglea thin, (1998). soft and flaccid; velum well developed; manubrium small with simple circular mouth; 16-30 broad, ribbon- Haliscera conica Vanhöffen, 1902 like radial canals, some may be bifurcated, circular (Fig. 151C) canal broad; 100-300 marginal tentacles, flexile proxi- mally and stiff distally in continuous row; shape of adult Umbrella up to 18 mm wide, with thick, bluntly gonads unknown; number of statocysts unknown. conical apical projection; gonads oval on the middle Records from Mediterranean: eastern Mediter- portion of the eight broad radial canals; 8-9 margin- ranean. al tentacles, flexile proximally and stiff distally and Known seasonality: 3. 2 statocysts in each octant, the base of each tentacle Distribution: Atlantic, Indo-Pacific, Antarctic, surrounded by a broad thickening of the marginal Mediterranean. cnidocyst tissue. References: Kramp (1961); Goy et al, (1991); Records from Mediterranean: western Mediter- Gili et al. (1998). ranean. Known seasonality: 2, 4-10. Family PETASIDAE Haeckel, 1879 Distribution: Antarctic; Atlantic; Indo-Pacific; Mediterranean. Trachymedusae with four radial canals; without References: Kramp (1961); Goy (1973b); Dallot, peduncle and centripetal canals; with well devel- Goy and Carré (1988); Boero and Bouillon (1993), oped manubrium; with 4 sac-like gonads on radial Mills et al, (1996); Goy (1997); Gili et al. (1998). canals; with marginal tentacles not in clusters, solid, with a terminal club-shaped knob of cnidocysts; Haliscera racovitzae (Maas, 1906) with free statocysts. (Figs. 151D-E) References: Bouillon (1999); Bouillon and Bar- nett (1999); Bouillon and Boero (2000). Umbrella 8 mm wide, 4 mm high, almost hemispherical; with fairly thin walls, mesoglea Genus Petasus Haeckel, 1879 thin, flaccid, apex evenly rounded; velum very wide; manubrium a truncated cone, broad, flat; Petasidae with marginal tentacles regularly mouth simple, circular; 8 radial canals, narrow arranged, at equal intervals. distally, circular canal fairly narrow; gonads flat, shield-shaped, along 1/2- 2/5 of proximal part of Petasus atavus Haeckel, 1879 the radial canals, very close to manubrium; with (Fig. 151G) 6 solid tentacles, flexile proximally and stiff dis- tally in each octant; with 2 statocysts in each Umbrella 1 mm wide and high, globular; octant. manubrium prismatic; mouth with 4 short lips; with Records from Mediterranean: western Mediter- 4 protrusive, spindle-shaped or band-shaped gonads, ranean. along greater part of the radial canals; four marginal Known seasonality: 9. tentacles with ciliated club–shaped end; four free Distribution: Atlantic, Indo-Pacific, Antarctic, statocysts. Mediterranean. Records from Mediterranean: eastern Mediter- References: Kramp (1961); Gili et al. (1998). ranean.

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Known seasonality: 4. References: Kramp (1961); Picard (1955a); Distribution: Atlantic, Mediterranean. Brinckmann-Voss (1987); Boero and Bouillon References: Kramp (1959a, 1961); Mayer (1993); Avian et al. (1995); Gili et al. (1998, 1999). (1910). Family RHOPALONEMATIDAE Russell, 1953 Family PTYCHOGASTRIIDAE Mayer, 1910 Trachymedusae with a narrow manubrium; with Trachymedusae with either simple manubrium or without peduncle; without centripetal canals; usu- without mesenteries, or with eight-lobed manubri- ally 8, rarely more, narrow radial canals; mouth with um, with eight mesenterial partitions; with marginal distinct lips; with marginal tentacles evenly distrib- tentacles grouped into more or less well defined uted, sometimes of two kinds, each marginal tenta- clusters, some with adhesive disks or with very cle of uniform structure throughout or with proximal numerous tentacles, not in clusters but inserted at portion differing from distal one; with gonads either various levels of exumbrella; no centripetal canals on radial canals globular, linear, or hanging in or peduncle; with 8 radial canals; gonads either pouches into subumbrellar cavity, or forming a con- attached onto manubrium, on sides of 8 manubrial tinuous ring around base of manubrium and extend- lobes, or on radial canals adjacent to manubrial lobe; ing outwards along radial canals; with free, rarely free ecto-endodermal statocysts. enclosed ecto-endodermal statocysts. References: Bouillon and Boero (2000). References: Bouillon (1999); Bouillon and Bar- nett (1999); Bouillon and Boero (2000). Genus Ptychogastria Allman, 1878 1. Gonads in a continuous band around manubrium Ptychogastriidae with marginal tentacle in clus- extending outwards on radial canals ...... ters, some with adhesive disks; manubrium with lat- ...... Homoeonema eral lobes; with eight mesenterial partitions; gonads – Gonads isolated, on radial canal, sometimes on the sides of the manubrial lobes or on radial adjacent to manubrium...... 2 canals adjacent to manubrial lobes. 2. Without gastric peduncle...... 3 – With gastric peduncle...... 7 Ptychogastria asteroides (Haeckel, 1879) 3. With 4 gonads only, pendent; 4 large and 24 (Figs. 152A-C) small marginal tentacles...... Tetrorchis – With 8 (rarely more) gonads ...... 4 Umbrella 4-5 mm wide, hemispherical to bell- 4. With two kinds of marginal tentacles; with shaped, with fairly thin mesoglea and a small round- enclosed statocysts ...... Rhopalonema ed apical projection; exumbrella with 16 raised radi- – With tentacles all of one kind; with free ating ridges extending from centre of exumbrella to club-shaped statocysts...... 5 margin where they end in 16 conical marginal lobes 5. onads adjacent to manubrium (sometimes also 8 beset with a few cnidocysts and numerous varied gonads free from manubrium); very numerous inclusions; manubrium eight-lobed; with eight tentacles...... Arctapodema mesenteries; mouth with four simple lips, rich in – Gonads separated from manubrium ...... 6 cnidocysts and granular gland cells; with 8 radial 6. Gonads globular, distal, contiguous to circular canal; with 8 egg-shaped gonads on proximal 1/3 of canal; with 8 tentacles ...... Sminthea radial canals adjacent to manubrium and linked to – Gonads linear, with 48 or more marginal him by the mesenterial septa; with 16 isolated solid tentacles...... Pantachogon tentacles armed with rings of cnidocysts and 200 to 7. Gastric peduncle short conical (in young 260 solid tentacles, most of them with adhesive specimens almost invisible); gonads attached on organs, and few scattered cnidocysts, in 16 clusters subumbrellar portions of radial canals...... 8 arising from the marginal lobes, velum thick, pow- – Gastric peduncle long, slender; gonads attached erful; 16 free statocysts. to peduncular portions of radial canals ...... 9 Records from Mediterranean: western Mediter- 8. With only two pendent gonads ...... Persa ranean, Adriatic. – With 8 gonads ...... Amphogona Known seasonality: 1-12. 9. Gonads linear on peduncle only...... Ransonia Distribution: endemic of the Mediterranean Sea. – Gonads sausage-shaped, pendent ...... 10

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10.Gonads attached to peduncle ...... Aglaura peduncle cylindrical about half as long as bell cavi- – Gonads attached to subumbrellar portions of ty; manubrium small, 1/8 as long as gastric pedun- radial canals ...... Aglantha cle; four triangular lips; eight gonads about as long as gastric peduncle, attached to about middle points Genus Aglantha Haeckel, 1879 of subumbrellar parts of radial canals; 40-48 mar- ginal tentacles; 16 free statocysts. Rhopalonematidae with a long and slender gas- Records from Mediterranean: Adriatic Sea. tric peduncle; with eight pendent sausage-shaped Known seasonality: 8. gonads on subumbrellar portions of the eight radial Distribution: Atlantic; Pacific; Mediterranean. canals; with numerous tentacles all alike; with free References: Kramp (1959a); Schmidt and Ben- club shaped marginal statocysts. ovic (1977).

1. Gonads on radial canals close to base of Genus Aglaura Péron and Lesueur, 1810 peduncle, 8 statocysts ...... A. digitale – Gonads on radial canals about midway between Rhopalonematidae with slender gastric peduncle; peduncle and umbrela margin, 16 statocysts ...... with 8 sausage-shaped gonads attached on peduncle, ...... A. elata not on subumbrella; with numerous tentacles all alike, with free club-shaped statocysts. Aglantha digitale (O.F.Müller, 1766) (Figs. 152D-E) Aglaura hemistoma Péron and Lesueur, 1810 (Fig. 152G) Umbrella cylindrical, 10-40 mm high, about twice high than wide, with a small conical projec- Umbrella 4-6 mm high, 3-4 mm wide; with ver- tion, lateral mesogleal walls thin, subumbrellar mus- tical, parallel walls, with very narrow longitudinal cles strong; peduncle slender, long, conical, almost ridges, with flattened apex, mesoglea exceedingly as long as subumbrellar cavity; manubrium small; thin; margin almost octagonal in cross section; mouth with four simple lips, eight, long, sausage- velum extremely broad, usually hanging down- shaped gonads, arising from the radial canals near wards; gastric peduncle, conical, somewhat shorter the apex of the subumbrella and hanging freely in than subumbrellar radius; manubrium small, flask- subumbrellar cavity; 80 or more solid marginal ten- shaped; mouth with four small, simple, projecting tacles with a core of single endodermal chordal lips; 8 narrow radial canals and narrow circular cells; 8 free statocysts. canal; gonads sausage-shaped attached on the Records from Mediterranean: western Mediter- peduncle at the place of juncture of the radial canals ranean. with the manubrium; 48-85 marginal tentacles all Known seasonality: 4 alike; 8 statocysts. Distribution: Atlantic; Indo-Pacific; Mediter- Records from Mediterranean: eastern and west- ranean. ern Mediterranean; Adriatic Sea. References: Kramp (1924, 1959a); Russell Known seasonality: 1-12. (1953); Gili (1986). Distribution: Atlantic, Indo-Pacific; Mediter- Remarks: Kramp (1924) described this species ranean. from the middle of the Strait of Gibraltar and esti- References: Kramp (1961); Berhaut (1970); mated that this species was attempting to enter in the Albertini-Berhaut (1971b); Goy (1973b); Castelló i Mediterranean where this species had however Tortella (1986); Gili (1986); Benovic and Bender never been found (see Kramp, 1959a, 1961; Goy (1987); Brinckmann-Voss (1987); Goy et al. (1988, 1972); Gili in 1986 collected 2 specimens in front of 1990, 1991); Boero and Bouillon (1993); Avian et Barcelona. al. (1995); Benovic and Lucic (1996); Medel and López-González (1996). Aglantha elata (Haeckel, 1879) (Fig. 152F) Genus Amphogona Browne, 1905

Umbrella 10-12 mm high, 3-4 mm wide, narrow, Rhopalonematidae with short, conical gastric elongated, with pointed apical projection; gastric peduncle, exumbrella smooth; with ellipsoidal or

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sac-shaped, pendant gonads on the 8 radial canals, proximal parts of radial canals; sometimes also 8 gonads usually of unequal size; with tentacles all pairs of small gonads on radial canals, separated from alike, not densely crowded; with free club-shaped manubrium; about 100 tentacles; 4-8 statocysts. statocysts. Records from Mediterranean: western Mediter- ranean, Adriatic. Amphogona pusilla Hartlaub, 1909 Known seasonality: 3, 5, 7, 9-11. (Fig. 152H) Distribution: Antarctic; Southern and tropical Atlantic; Mediterranean. Umbrella 1.5- 6 mm wide, nearly hemispherical, References: Kramp (1961); Goy (1973b); Boero with thin mesoglea; manubrium small, short; with and Bouillon (1993); Avian et al. (1995). short conical gastric peduncle; mouth with four sim- ple lips; 8 simple radial canals; 8 gonads, spherical Arctapodema australis (Vanhöffen, 1912) to elongated, on distal part of the radial canals, liv- (Figs. 153A-C) ing 1/4 of the length of radial canal near circular canal free; 16 marginal tentacles with basal enlarge- Umbrella up to 23 mm wide and 14 mm high, ments, statocysts unknown. mesoglea thin; manubrium short and broad, with 16 Records from Mediterranean: western Mediter- radial folds; mouth with four simple lips; 8 gonads ranean. globular or club-shaped, pendent, on the radial Known seasonality: 4. canals near base of the manubrium; about 112 mar- Distribution: Indo-Pacific; Mediterranean. ginal tentacles; statocysts unknown; manubrium red References: Kramp (1961, 1965); Goy (1973b); in adults. Boero and Bouillon (1993). Records from Mediterranean: western Mediter- ranean; Adriatic Sea. Genus Arctapodema Dall, 1907 Known seasonality: 4, 7-10. Distribution: Antarctic; Indo-Pacific; Mediter- Rhopalonematidae without gastric peduncle; ranean. with gonads on radial canals adjacent to manubrium; References: Kramp (1961); Schmidt and Benovic with 8 narrow radial canals; numerous tentacles, all (1977); Benovic and Bender (1987); Benovic and alike, in a single row; free statocysts. Lucic (1996); Gili et al. (1998).

1. Manubrium with 16 radial folds; gonads pendent Genus Homoeonema (Maas, 1893). on radial canals, near base of manubrium...... Browne, 1903 ...... A. australis – Manubrium with 8 radial lobes; gonads Rhopalonematidae without gastric peduncle; extending from radial lobes of the manubrium gonads forming a continuous band around base of outwards on proximal parts of radial canals, manubrium and extending outwards along proximal sometimes also pairs of small gonads on radial half of 8 radial canals; numerous tentacles, all alike; canals separated from manubrium...... A. ampla vesicular statocysts.

Mills et al, (1996) found in the Alborán Sea an Homoeonema platygonon Browne, 1903 Arctapodema sp. that they could not assign to either (Figs. 153D-G) of the above-cited species. Umbrella up to 2 mm high, bell shaped, higher Arctapodema ampla (Vanhöffen, 1902) than wide, with round or more rarely conical apex (Figs. 152I-J) mesoglea thin, apical part containing numerous fat droplets and irregular inclusions (crystals); no Umbrella up to 15 mm wide, somewhat flatter peduncle; manubrium short, flat, quadratic; mouth than a hemisphere, mesoglea thin; manubrium short, with 4 simple, short, recurved lips, the tips armed urn-shaped, with 8 radial lobes; mouth with four sim- with stenoteles; no apical process; up to 80 close- ple lips; 8 simple radial canals; with 8 swollen gonads ly crowded marginal tentacles, issued from an of unequal size, some divided in two halves, extend- exumbrellar marginal ring rich in cnidocysts and ing from radial lobes of manubrium outwards onto irregular inclusions; base of tentacles enlarged,

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containing cnidocysts and inclusions, giving broad; manubrium small, varying in length, octago- rather abruptly rise to the proximal parts of the nal at base; mouth with 4 simple, small, pointed lips; tentacles which are straight, devoid of cnidocysts no gastric peduncle; 8 narrow, straight radial canals, and have their endodermal core built by large circular canal narrow; gonads initially forming dis- cubical chordal cells (perhaps flexible), distal continuous linear swellings along distal 2/3 or parts of the tentacles spirally coiled, crowded with almost whole length of the radial canals, which cnidocysts, endodermal core formed by flattened, eventually coalesce and become folded transversal- disk-shaped, chordal cells; no cirri or non tentacu- ly; 64 marginal tentacles all alike in one row; 64 free lar bulbs; eight fairly wide radial canals, full of club-shaped statocysts. irregular inclusions, circular canal not visible Records from Mediterranean: eastern Mediter- included in the marginal cnidocyst ring; velum ranean. very large; gonads, in adults 8 elongated masses Known seasonality: 1, 3, 9, 11, 12. along the 1/2 or 2/3 of the proximal part of the Distribution: Atlantic, Indo-Pacific, Antarctic, radial canals, their most proximal ends being fused Arctic, Mediterranean. and forming a small ring surrounding the base of References: Kramp (1961); Dowidar and El- the manubrium, in young specimens the gonads Maghraby (1970); Arai and Brinckmann-Voss appear first as oval masses on the proximal third (1980); Winkler (1982); Dowidar (1983); Goy et al. of the radial canals and then slowly extend down- (1988, 1990, 1991); Boero and Bouillon (1993); Gili wards and upwards, they finally become confluent et al. (1998). in the upper interradial parts and encircle the manubrial base; vesicular statocysts. Pantachogon militare (Maas, 1893) Records from Mediterranean: western Mediter- (Fig. 154B) ranean; Adriatic. Known seasonality: 2, 4, 5, 7, 8, 10-12. Umbrella 7-10 mm wide, 6 mm high; mitre- Distribution: Atlantic; Mediterranean; Arctic. shaped, with a well developed apical projection; References: Kramp (1947, 1959, 1961); Boero gonads lancet-shaped, on distal half of 8 radial and Bouillon (1993); Avian et al. (1995); Benovic canals; 48 tentacles all alike; 4 (or more) statocysts. and Lucic (1996); Gili et al. (1998). Records from Mediterranean: western Mediter- ranean. Genus Pantachogon Maas, 1893 Seasonality: ? Distribution: Atlantic; Mediterranean; Antarc- Rhopalonematidae without gastric peduncle; tic?. with the apical outlines of the subumbrellar muscu- References: Kramp (1959a, 1961); Boero and lar fields forming an entire circle; with gonads on Bouillon (1993). the 8 radial canals separated from manubrium; with 48 or more tentacles all alike; free club-shaped mar- Genus Persa McCrady, 1859 ginal statocysts. Rhopalonematidae with a short gastric peduncle; 1. Umbrella mitre-shaped, with gelatinous apical with only two oval or sausage-shaped gonads, pen- projection; 48 marginal tentacles...... P. militare dant, near middle point of the subumbrellar portions – Umbrella without apical projection; 64 marginal of two opposite radial canals; 8 radial canals; with tentacles...... P. haeckeli numerous long tentacles, all alike, each with a ter- minal knob; with free club-shaped statocysts. Pantachogon haeckeli Maas, 1893 (Figs. 153H-J, 154A) Persa incolorata McCrady, 1859 (Figs. 154C-D) Umbrella about 20 mm wide and high, bell- shaped, sometimes wider than high, without apical Umbrella 3 mm wide, 4 mm high, with or with- projection, mesoglea fairly thin; umbrella with very out a small apical projection, mesoglea very thin; strong and conspicuous musculature, forming an velum broad; with a very retractile gastric peduncle; entire circle; large specimens with 32 fine exum- manubrium tubular, elongated; mouth with four brellar longitudinal meridional furrows; velum very small, broadly rounded, prominent lips; 8 narrow

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radial canals; with only two oval or sausage-shaped 1. Umbrella with a distinct apical knob; gonads gonads, pendant, near middle point of the subum- oval, in the middle third of radial canals; brellar portions of two opposite radial canals; up to statocysts close beside tentacles...... R. velatum 48 marginal tentacles all alike, each with a terminal – Umbrella without apical knob; gonads along knob; 8 club-shaped statocysts. distal 2/3 of radial canals; statocysts in the Records from Mediterranean: eastern and west- middle of spaces between tentacles ...... ern Mediterranean; Adriatic...... R. funerarium Known seasonality: 1-12. Distribution: Atlantic; Indo-Pacific; Mediter- Rhopalonema funerarium Vanhöffen, 1902 ranean. (Figs. 155A-D) References: Kramp (1961); Berhaut (1970); Albertini-Berhaut (1971b); Goy (1973b); Castelló i Umbrella up to 17 mm wide and 14 mm high, Tortella (1986); Gili (1986); Benovic and Bender hemispherical to somewhat conical but without api- (1987); Goy (1987); Goy et al. (1988, 1990, 1991); cal projection, mesoglea stiff, but fairly thin; no gas- Pagès et al. (1992); Boero et al, (1993); Avian et al. tric peduncle; velum very broad; manubrium nar- (1995); Benovic and Lucic (1996); Medel and row, elongated, quadrilateral with octagonal base, López-González (1996); Gili et al. (1998). contractile, hardly reaching velar opening; mouth with 4 simple lips; 8 narrow straight radial canals, Genus Ransonia Kramp, 1947 narrow circular canal; gonads as elongated, linear pouches, extending along distal 2/3 of the radial Rhopalonematidae with high conical umbrella canals; 8 large radial marginal tentacles with (similar to Aglantha); with long and narrow gastric swollen ends, 3 very short, club-shaped cirrus-like peduncle; 8 radial canals; linear, discontinuous, tentacles in each octant, 32 enclosed statocysts in gonads along peduncular portions of radial canals, the middle of the spaces between tentacles. not on subumbrella; numerous tentacles, all alike; Remarks: Rhopalonema funerarium is consid- statocysts unknown. ered by several authors as a deep-water race of R. velatum. However, it is a distinct species for Kramp Ransonia krampi (Ranson, 1932) (1961; 1965; 1968). In fact, most of the characters (Fig. 154E-G) used to distinguish between the two presumed species (form of the umbrella, development of the Umbrella 8 mm wide, 15 mm high, conical, with gonads) appears to be nothing more than intraspe- thin walls, with small apical projection; gonads cific variations, perhaps the position of the stato- more or less discontinuous along the eight radial cysts is the only valid character allowing the separa- canals on the long, narrow peduncle; about 88 mar- tion of the two forms. ginal tentacles. Records from Mediterranean: eastern and west- Records from Mediterranean: western Mediter- ern Mediterranean,Adriatic. ranean. Known seasonality: 1-3, 6, 9, 10. Known seasonality: 4. Distribution: Atlantic, Indo-Pacific, Mediter- Distribution: Atlantic; Mediterranean. ranean. References: Kramp (1959a, 1961); Gili (1986); References: Kramp (1961); Dowidar (1983); Gili Boero and Bouillon (1993); Medel and López- (1986); Benovic and Lucic (1996); Medel and González, 1996; Mills et al. (1996). López-González (1996); Gili et al. (1998).

Genus Rhopalonema Gegenbaur, 1857 Rhopalonema velatum Gegenbaur, 1857

Rhopalonematidae without gastric peduncle; Umbrella 8-10 mm wide, 6.6 mm high, somewhat with gonads along the radial canals separated from flatter than a hemisphere, with a solid conical or manubium; with marginal tentacles of two kinds: dome-like apical thickening, mesoglea stiff, but fairly large, club-shaped, perradial tentacles with swollen thin, except at apex; velum very broad almost closing ends and inter-and adradial short, stiff, cirri-like ten- umbrella cavity; manubrium narrow, elongated, tacles also with swollen ends; with enclosed stato- cylindrical, with octagonal base, contractile, reaching cysts. extended almost velar opening; no gastric peduncle;

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mouth with 4 simple or somewhat elongated lips, Genus Tetrorchis Bigelow, 1909 often strongly recurved; 8 straight radial canals and circular canal narrow; gonads linear or oval on mid- Rhopalonematidae without gastric peduncle; dle third of the 8 radial canals; 8 large radial margin- with only 4 pendant sausage-shaped gonads al tentacles, 1-3 short cirrus-like tentacles in each attached to 4 of the 8 radial canals near the middle octant, all tentacles with swollen ends; an enclosed points; with 4 large perradial and several small mar- statocyst close besides each right side of the perradi- ginal tentacles. al tentacles and interradial cirrus-like tentacles. Records from Mediterranean: eastern and west- Tetrorchis erythrogaster Bigelow, 1909 ern Mediterranean; Adriatic Sea; Black Sea. (Figs. 155J-L) Known seasonality: 1-12 (see Albertini-Berhaut, 1971a). Umbrella 10-12 mm wide and 8 mm high, pyri- Distribution: Atlantic; Indo-Pacific; Antarctic; form, apex mesoglea very thick, lateral mesoglea Mediterranean. thin; velum well developed; no gastric peduncle; References: Kramp (1961); Albertini-Berhaut manubrium tubular, brilliant carmine, reaching (1970a); Goy (1973b); Castello i Tortella (1986); slightly beyond velar opening; mouth with 4 small, Gili (1986); Benovic and Bender (1987); Brinck- simple lips; 8 straight radial canals, circular canal mann-Voss (1987); Goy et al. (1988, 1990, 1991); narrow; 4 sausage-shaped gonads attached to every Boero and Bouillon (1993); Avian et al. (1995); second radial canals, middle to distal in position; 4 Benovic and Lucic (1996); Medel and López- large perradial tentacles opposite fertile radial canals González (1996); Gili et al. (1998). and 16-24 small tentacles not placed in reference to the radial canals; statocysts unknown. Genus Sminthea Gegenbaur, 1857 Records from Mediterranean: eastern Mediter- ranean. Rhopalonematidae without gastric peduncle; Known seasonality: 10-12. with globular gonads on very distal parts of the 8 Distribution: Atlantic; Indo-Pacific; Mediter- radial canals; with only 8 perradial tentacles; with ranean. enclosed statocysts. References: Bigelow (1909); Kramp (1961); Lakkis and Zeidane (1985); Goy et al. (1988, 1990, Sminthea eurygaster Gegenbaur, 1857 1991); Boero and Bouillon (1993); Gili et al. (1998). (Figs. 155G-I) Class POLYPODIOZAE Umbrella up to 6 mm wide and about half as high, umbrella-shaped, with a small apical projec- Family POLYPODIIDAE Poche, 1914. tion, mesoglea stiff, fairly thin; velum well devel- oped; manubrium short, cylindrical; mouth with 4 See characters of subclass short simple lips; no gastric peduncle; 8 straight radial canals, circular canal narrow; 8 perradial mar- Genus Polypodium Ussow, 1887 ginal tentacles; gonads globular to egg-shaped on radial canals very close to circular canal; 8 interra- See characters of subclass. dial enclosed statocysts. Records from Mediterranean: eastern and west- Polypodium hydriforme Ussow, 1885 ern Mediterranean; Adriatic. (Fig. 156) Known seasonality: 1, 5-9. Distribution: Atlantic; Indo-Pacific; Antarctic; See characters of subclass, free stage 2-5 mm in Mediterranean. size. References: Kramp (1961); Vannucci (1966); Records from Mediterranean: Fresh water basins Berhaut (1970); Goy (1973b); Gili (1986); Benovic of the Azov and Black Sea. and Bender (1986, 1987); Goy et al. (1988, 1990, Known seasonality: Free living stage: 5-7. 1991); Boero and Bouillon (1993); Avian et al. Distribution: Fresh-water Basins of Russia; Rou- (1995); Benovic and Lucic (1996); Medel and mania; Iran, North America. López-González (1996); Gili et al. (1998). References: Raikova (1958, 1973, 1980, 1988,

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1994); Suppes and Meyer (1975); Dick et al. (1991). have recently been found to produce swimming Monteiro, Okamura and Holland (2002); Okamura gonophores. Far too many species and genera have et al. (2002); Zrzavy (2001); Zrzavy and Hypsa unknown hydroids or medusa stages, so that life (2003). cycle elucidation is still a priority for the study of this group.

COLLECTION OF THE MATERIAL Medusae

Hydroids Gelatinous plankton is very fragile and easily torn and damaged when collected. Benthic hydroids have been traditionally col- Hydromedusae can be caught by plankton nets lected with dredges and grabs, from ordinary that are very slowly towed behind a large or a boats or research vessels. This practice has led to small powered vessel or a even a row boat for the collection of a host of large colonies of Sertu- about ten to twenty minutes depending on the lariidae, Aglaopheniidae, Syntheciidae, Sertulari- abundance of the plankton. For hydromedusae the idae, these being evident during sorting. The iden- mesh size of the net should be about 200-250 µm, tification of inconspicuous hydroids, either alive larger meshes let escape many small specimens, or preserved, necessitates careful sorting of mate- smaller meshes are to easily clogged and damage rial, inspecting each substrate fragment while in the specimens. In coastal waters the opening of the liquid. Many hydroids are commonly associated net should be from 30 cm to 1 m depending the with algae, sea grasses, sponges, other hydroids, power of the vessel, much wider openings are used anthozoans, bryozoans, molluscs (bivalve, gas- in open sea and deep waters where the fauna is tropods, pteropods), annelids, crustaceans, ascidi- sparser. In areas very rich in plankton, a hand net ans, fishes, and must be searched for under a or even a bucket may be used. The richest catches stereomicroscope. Hydroids are common inhabi- are generally obtained in the early morning or at tants of shaded hard substrates. Intertidal speci- dusk and on rising tides. For qualitative horizontal mens can be collected easily at low tides, where- subsurface sampling the plankton net is towed by as subtidal specimens are best collected by a rope of 50 m or more behind the vessel to elim- SCUBA diving, since the crevices and small cav- inate turbulence. For sampling in few meters ities they prefer are difficult to sample from the below the surface a buoy can be attached with a surface. While collecting, it is important to be rope of known length to one side of the ring open- aware of the substrates that are possibly con- ing and a weight on the other side. Sampling ducive to hydroid settlement. These must be col- between fixed depths requires closing nets. Quan- lected even if no specimens are evident. Kept in titative sampling is possible with plankton nets fit- the laboratory, in calm water, these substrates ted with a flow-meter a little behind their front, might reveal fruitful catches. after calibration these water-meters give a mea- Deep and soft-bottom species must be collect- sure of the quantity of water filtered. ed from boats, with either dredges or grabs. In If it is impossible to sort the medusae immedi- shallow water, however, soft bottom hydroids can ately, the catch should as quickly as possible be be seen while SCUBA diving, since some species fixed at once with formaldehyde, so to obtain a are rather conspicuous. Interstitial species are col- final solution of 5% fixative (see fixation). If the lected by the standard techniques of meiobenthic material can be brought rapidly to the laboratory, research. the plankton samples, shielded from direct sun- Many hydroids are not recognisable if not fertile, light and kept as cool as possible should be exam- and information on complete life cycle is necessary ined under stereo-microscope and the medusae for an accurate identification. If at a specific site an individually removed with wide-mouthed pipettes hydroid without gonophores is located, it is advis- and placed in finger bowls of clear sea water. After able to collect specimens periodically (at least once observation they can either be kept for rearing or per month) until ripe colonies are found These must anaesthetised and fixed as described below. This be kept in the laboratory for gonophore rearing. last method is of course the most rewarding, Even groups that are usually thought to be com- allowing observation of the living animals charac- pletely paedomorphic, and so deprived of medusae, ters and perfect fixation.

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TECHNIQUES distortion and contraction of the specimens. Never- theless, for long term preservation, for instance in Fixation and preservation of the material museum collections, the formaldehyde is not ade- quate causing auto-maceration of the tissues and Hydroids should be replaced by 70 % alcohol. The passage from formaldehyde to alcohol must imperatively be Colonies are usually preserved directly either in gradual, going from formaldehyde to a very dilute formaldehyde or alcohol. This practice usually leads alcoholic solution (less than 10%) and then, step by to specimens with poorly preserved coenosarc, step (10% by 10%), in several days, to the final 70 skeletal parts being the only well preserved items. % solution (Petersen, 1976). Polythene containers This is the reason why the material coming from should be avoided, chemical precipitates being able “expeditions” is very rich in large thecate colonies, to damage the specimens. For histological studies whereas athecate and delicate forms are apparently the best fixative is, after anaesthetisation, cold (5-8° absent. In order to have properly preserved hydroid C.) acidic Bouin’s fixative (= 75% of a solution of material, the same techniques employed for the saturated aqueous solution of picric acid + 25% medusae should be used. Modern molecular tech- from a commercial formaldehyde: just before use niques require fixation in alcohol, since DNA 5% glacial acetic acid should be added to this solu- probes are impossible in formalin-preserved materi- tion). The material can afterwards be preserved for al. When possible, thus, a batch of specimens should a long time in 5% commercial formaldehyde the be preserved in alcohol. Whole mounts, obtained by specimens being less affected after this treatment by dehydration of specimens and mount in microscope formaldehyde auto-maceration. slides, is very advisable. Mounted specimens can be A method of long-term storage has been devel- studied also after centuries, whereas those preserved oped by Van Impe (1992) where the medusae are in liquid tend to disintegrate. This is very important suspended in a solid agar-agar gel colored with for the preservation of type material. serva-blue and from which extraction is easy when required. This method is particularly useful for Medusae transportation and for long term conservation; all holotypes should be stored in such a gel which up to Hydromedusae should be anaesthetised before a certain point also avoids drying out and stain nice- being fixed; most of the fixatives cause shrinking ly the medusae tissues in blue. and deformations. The animals should be allowed to In most of the Museum collections the majority extend in a vessel of water where the anaesthetic of the hydromedusae specimens, including holo- substance should be added slowly, crystal by crystal types, have been destroyed because of the disastrous or drop by drop. The most common anaesthetic sub- habit of the museum keepers to put label cards into stances for marine medusae are menthol crystals, the storing jars containing the specimens. Such a propylene phenoxetol and magnesium chloride custom should be totally avoided because after a few (about 7.5% Mg Cl2, 6H20 in fresh water), the last manipulations or a single material expedition to a being the most recommended (Smaldon and Lee, specialist, only the label remains. Should also be 1979). For general taxonomic purposes hydrome- avoided the cotton or paper material caps whose dusae can be fixed in 10% buffered formaldehyde in fibers adhere and damage the specimens. seawater (the commercial formaldehyde being con- sidered as 100%) and preserved for short periods in Preparation of permanent microslides 5% formaldehyde. The effects of formaldehyde preservation on size and weight of hydromedusae Hydromedusae and siphonophores have been studied by de Lafontaine and Leggett (1989). Buffering with borax or calcium carbonate Anaesthetisation: 1) with magnesium chloride should be avoid since the medusae may adhere to 7.5% in fresh water, add drop by drop to the jar con- any precipitate formed by those chemicals on the taining the medusa or siphonophore in sea water till bottom of the containers, so should be hexamine complete anaesthetisation. 2) with menthol crystals, which destroy the mesoglea, the best buffer seems add crystal by crystal till complete anaesthetisation. to be sodium glycerophosphate. Alcohol should not Fixation: buffered formaldehyde 10% be used as fixative because it leads to shrinkage, Coloration: hemalun*; boracic carmin**

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1) mount in hydro-or aquamount: *hemalun: - from formaldehyde to water - solution of 1gr of hematoxylin, 0.2gr of sodium - from water to aquamount 50%-water 50%, half iodate, 50gr of potassium alum in 1000cc of distil- an hour late water; colour from 5 to 20 minutes depending - to pure aquamount, half an hour size - place a drop of aquamount on the stand-slide - differentiate (removing the excess of colour so - place the material in the drop to have a pure nuclear stain) in a solutions of 1 % of - put a little drop of aquamount on the cover slide alum - put the cover-slide on the stand-slide - wash in tap (calcareous) water till the colour becomes dark bleu 2) mount in Canada balsam: - put in alcohol 75 % and mount in balsam or in keep in water and mount in hydro-or aquamount - from fixator to alcohol 10% and then step by (see above) step, 10% by 10% to final alcohol 100%; all steps half an hour ** boracic carmin: - 75% alcohol 100% and xylol 25 %, half an hour - solution of (Na2B407, 10H2O) (borax) 4% in - 50% alcohol 100% xylol 50%, half an hour 100cc of water + 2 to 3gr of carmin. - pure xylol, half an hour - let the objects from a few minutes to several - balsam 50% xylol 50%, half an hour ones in this solution depending their size - place a large drop of balsam 50% xylol 50% on - differentiate in a solution of 100cc of alcohol the stand-slide 75% + 6 droplets of HCl - place the material in the drop - when the colour is satisfactory put in alcohol - place a little drop of pure balsam on the cover 90% and mount in balsam or return to water and slide mount in hydro-or aquamount (see above) - put the cover-slide on the stand-slide ***hemalun, eosin, light green Hydroids hemalun see* - colour in eosin 1 % in distillate water for one Anaesthetisation: a) with magnesium chloride minute 7.5% in fresh water, add drop by drop to the jar con- - wash in distillate water and dedifferentiate in taining the hydroid in sea water. b) with menthol alcohol 70% crystals, add crystal by crystal till complete anaes- - put in alcohol 90% thetisation. - colour in a solution of light green 0.5% alcohol Fixation: formaldehyde 10% or alcohol 7 5% or 50 or 70 % for a few minutes Bouin’s fixative**** - differentiate in 90% alcohol Coloration: hemalun*; boracic carmin**; - transfer in alcohol 100% and mount in balsam hemalun, eosin, light green*** (see above)

- from fixator to alcohol 75% (can stay for ever) **** Bouin’s fixative - alcohol 75% to alcohol 90%, half an hour saturated picric acid in distillate water 75% + pure - alcohol 90% to alcohol 100%, half an hour formaldehyde 25% - alcohol 100% to 50% alcohol 100% and 50% - this two solutions can be mixed and prepared in pure xylol, half an hour advance = 100% - to pure xylol, half an hour - at the moment of fixation add 5% glacial acetic - balsam 50% xylol 50%, half an hour acid - place a large drop of balsam 50% xylol 50% on - wash the hydroids in 75% alcohol till disap- the stand-slide pearing of picric acid; transfer them for staining or - place the material in the drop conservation in alcohol 75% - put a little drop of pure balsam on the cover slide - put the cover-slide on the stand-slide

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GLOSSARY adhesive pad: adhesive structure lacking cnidocysts, usually located near tentacle tip, sometimes abaxial: away from the main axis, or on a site remote along tentacle surface. from it; in a medusa marginal tentacle, the outer adnate: having part or all of one side in contact with, tentacular surface, in siphonophores the dorsal side. or fixed to, another structure, (e.g. adaxial side of abcauline caecum, or blind sac, or abcauline diver- a marginal tentacle fixed to the exumbrella in ticulum: a finger-shaped, blind expansion of the Leuckartiara adnata; hydrothecae having part or abcauline wall of the hydranth in many Sertulari- all of one side in contact with the supporting idae and some Syntheciidae, mainly evident in stem). contracted hydranths. Due in part to the attach- adradial: the axes or sectors lying between the per- ment of the ectoderm of this region to the mantle radial and interradial ones; in a medusa with 4 and/or hydrothecal wall, preventing its complete radial canals there are 4 perradial axes; 4 interra- withdrawal. It imparts a bilateral symmetry to the dial axes and 8 adradial axes and 16 sectors. hydranth. In the Sertulariidae used in generic alternate: in hydroids, hydrocladia or hydrothecae diagnoses, although the caecum is less evident arising alternately on the left and the right side of when the hydranth expands. For instance in the the stem. Sertulariidae present in Abietinaria, Calampho- amphicoronate: alternate up and down arrangement ra, Cratitheca, Hydrallmania, Parascyphus, Ser- of a single row of oral tentacles. tularella, Sertularia, Symplectoscyphus, ampulla: superficial or internal rounded chamber Thuiaria. In other genera of Sertulariidae the from the outer surface (coenosteum) of calcare- hydranth is withdrawn symmetrically into the ous hydrozoan colonies, containing the hydrotheca and there is no caecum, although a gonophores, usually forming blister-like convex- mantle may be present (for instance Dictyocladi- ities on the surface in the Stylasteridae, often um, Diphasia, Dynamena, Idiellana, Salacia). with an efferent duct. abcauline: on the side away from the caulus, the anastomosing: branched structure in which some opposite is adcauline. branches rejoin and fuse with others to form a acnide tentacle: tentacle deprived from cnidocysts, network. sensory tentacle in capitate hydroids. aneural conduction: type of conduction where the acraspedote: medusae lacking velum. impulses are linked with electrical activities of acrocyst: a gelatinous, apparently structureless body cellular membranes other than neural (e.g. extending from the gonophore and held outside epithelial cells, muscular cells, of both ectoder- the gonothecal opening, where embryos develop mal and endodermal origin). (brood chamber). annular ectodermal fold = ring fold: folding of the acrosphere: conspicuous ectodermal knob at the end mantle, linking the proximal part of the hydranth of a tentacle, laden with numerous cnidocysts = to the hydrotheca, evident in contracted capitation. hydranths (Thyroscyphidae). actinula: creeping, postembryonic, tentaculated lar- annular perisarcal ring or thickening: see val stage, characteristic of some Anthomedusae, diaphragm. resembles a small hydranth, usually with two or annulus - annulation: an encircling groove or any more circles of tentacles, developing directly into ring-shaped structure in a hydroid stem, usually a hydroid stage. Not homologous to the tentacu- with thinning of perisarc, allowing passive bend- lated post-embryonic larvae of the Tra- ing. One in a series of rings in perisarc, typically chymedusae and Narcomedusae, inappropriately in groups directly below hydranths, demarcating called “Actinulae”, with only one aboral circle of the internodes, at nodes, or where stems branch. tentacles, a different histological structure and apical knob or chamber: small aboral chamber at the giving rise directly to medusae. apex of the manubrium, protruding into the api- adaxial: position opposite to abaxial, facing towards cal umbrellar mesoglea (e.g. some Coryne; the main axis; in a medusa marginal tentacle, the Amphinema rubra; Euphysora furcata, Plotoc- inner tentacular surface, in siphonophores the nide borealis, etc.). ventral side. apical or umbilical canal: during the development of adcauline: directed towards the caulus, see a medusa bud, an opening provides continuity abcauline. and exchanges between the “maternal” gastric

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cavity and that of the bud. Generally this opening the specific name. disappears after liberation, but in some medusae biseriate: in two rows. it remains as a small canal or duct projecting blastostyle: carrier of gonophores generally reduced from the manubrium into the apical mesoglea to a didermic axis or stalk bearing the developing and often leading upwards to the outside (e.g. gonophores: medusae or their reduced deriva- Coryne producta, Corymorpha nutans). tives medusoids or sporosacs. apical projection or process: a rounded or pointed, blind canal: centrifugal or radial canal that do not usually roughly conical mesoglear extension of join circular canal (e.g. Toxorchis); centripetal the top of the umbrella (e.g. Amphinema, canals that do not join radial canals or manubri- Leuckartiara). um (e.g. some Calycopsis). apical wings: apico-lateral processes of physonect bract: protective or buoyant siphosomal element, nectophores, which extend around stem. usually containing much mesoglea and gas- apical: situated at the apex. trovascular expansions. Absent in Cystonects, apophysis: short process of the hydrocaulus that present both in Physonects (except the family bears the hydrocladia, or of the hydrocladia bear- Physophoridae) and Calycophores (except in the ing the hydrothecae (see hydrophore). Family Hippopodiidae) arborescent: polyp colony with a stout hydrocaulus brood chamber: protective chamber within which bearing many scattered branches at its distal end. planulae develop (gonothecal acrocyst, marsupi- Athecate-athecata: In polyps, lacking a proper um, brood chamber of Eleutheria medusae etc.). hydrotheca (ahydrothecate): the hydroids of the budding: asexual reproduction in which a new Anthomedusae. In stems internodes lacking any organism develops as an outgrowth or bud from thecate formation: hydrothecae, nematothcae, the parent, either remaining attached (to form a gonothecae etc. colony) or becoming detached from the parent. athorybia stage: larval stage in physonect develop- Common in Cnidaria. Budded polyps and ment bearing a pneumatophore, primary gastro- Automedusa derive from simple buds; the zooid, tentacles and a ring of larval bracts. medusae of Hydroidomedusa derive from special aurophore: gas secreting portions of the pneu- buds, containing the entocodon. matophore, partially constricted off as bell-like bugle: in haleciids an annular thickening of bodies in the physonect family Rhodaliidae. unknown function often present half way up the basal facet of mouthFig.: ventral surface of mouth in gastric column of the hydranths, perhaps the calycophoran anterior nectophore, which may limit between two histological distinct regions of articulate with posterior nectophore. the endoderm. basal lamella: a thin extension of the nectophore bulb: see tentacular or non tentacular marginal bulb. below the ostium of the nectosac on its ventral bushy: polyp colony whose hydrocaulus bears many side; one or more lamellae comprise the mouth- lateral branches throughout its length. plate. butt = shaft: enlarged portion of cnidocyst tubule, it basal web = intertentacular web = umbrellula may bear stylets and/or spines, either of uniform basigaster: basal part of the siphonophore gastro- or not uniform diameter. zooid. campanopsid: hydroids having hydrothecae reduced battery: aggregation of various types of cnidocysts or absent of the form characteristic of the nominal within a single ectoderm cell, often in groups. genus Campanopsis, i.e. hydranths with an inter- bell: see umbrella. tacular web, each arising singly from a stolon; bicoronate: arrangement of oral tentacles in two perisarc is thinning completely away below the whorls. hydranths, medusae buds formed on hydranth (see bicuspidate: having two cusps (said of hydrothecal Helgicirrha shulzei; Eirene viridula). cusps). campanulate or campanuliform: bell-shaped. bifid: forked into two roughly equal parts. campanulinid: hydroids having hydrothecae of the bimucronate: with two sharp points (e.g. the form characteristic of the nominal Genus Cam- hydrothecal cusps of Obelia bidentata). panulina, i.e., with campanulate, pedicellate binomen: ( binominal) comprising the two names hydrotheca with conical operculum formed by that together form the scientific name of a several triangular, convergent pleats or segments species, comprising the genus name followed by meeting centrally and which may be or may not

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be sharply demarcated from the hydrothecal mar- flexile cirri: straight, do not coil and have cnidocysts gin, usually with diaphragm; such forms are not in rings (e.g. Cosmetira). necessarily closely related. Cirri may be immediately adjacent to the marginal canaliculate: of a stem comprising several coenosar- bulbs and are then said lateral cirri (e.g. cal tubes in a common perisarc. Eucheilota), they may also occur along the capitate: tentacle or nematophore with a distinct dif- umbrellar margin in the inter-spaces between ferentiated, large ectodermal knobbed end marginal tentacles, they are then called marginal (acrosphere) richly armed with cnidocysts and cirri (e.g. Cosmetira, Phialopsis). often with sensory cells. Not to be confused with cladium: a branchlet off the main stem or caulus a simple accumulation of cnidocysts. (hydrocladium). capsule (cnidocyst capsule): double-walled enve- clasp: part of a marginal bulb embracing the exum- lope of cnidocysts, containing the soft, coiled brella (e.g. Leuckartiara) (see exumbrellar spur). tubule, intracapsular liquid and bearing a distal cleptocnidae (cnidosacs): cnidocysts deriving from operculum. cnidarian prey, kept in specialised structures of cateniform: tentacle with cnidocysts in a distinct nudibranchs, Nemertea, Turbellaria etc. large terminal capitation and with numerous spi- cnidae: a general term for the stinging or adhesive rally arranged small cnidocyst clumps. cells characteristic and source of the name of the cathamnal lamella: endodermal sheet connecting the phylum Cnidaria: cnidocysts, spirocysts and pty- radial canals through the umbrellar jelly and sep- chocysts. arating the outer from the inner mesoglea. cnidoband: structure on the tentillum bearing dense caulus: main stem (hydrocaulus). aggregations of various kinds of cnidocysts, and central organ: swelling at junction of the canal sys- gives rise to endfilament. tem and stem in some Prayidae siphonophores. cnidoblast: developing cnidocyte, often used as syn- centrifugal canal: canal issued from the manubrium onym with cnidocyte. and directed towards umbrellar margin. cnidocil: bristle-shaped projection adjacent to oper- centripetal canal: canal issued from the circular culum at the distal end of a cnidocyte; serves as canal and directed towards the manubrium (e.g. trigger to discharge the cnidocyst. Calycopsis). cnidocyst (or stinging cell): stinging organelle char- cheval-de-frise: see ring palissade. acteristic of the Cnidaria, it consists of a double- chordal or chordoid: formed by a core of single disk- walled capsule, secreted by a particular cell like or cylindrical cells placed end to end in a sin- called cnidocyte, containing a refringent fluid, a gle row (e.g. solid tentacles of Obelia medusae). distal operculum, and a coiled and folded tubule circlet: whorl or ring of tentacles whose bases are (shaft, thread or internal tube) which everts and almost at the same level. straightens on discharge. Following the structure circular or ring canal: simple canal running around of the internal tube, different types of cnidocysts the umbrellar margin, linking the ends of the are recognised, they are of great use in taxonomy. radial canals; occasionally the circular canal is Cnidocyst are used for prey capture, defense, and not hollow but consist of a solid core of endoder- attachment. They are known to be under nervous mal cells (e.g. Proboscidactyla, Laingiome- control (= nematocyst). dusae). In the Narcomedusae, with umbrellar cnidocyst marginal ring = nettle ring: a dense band margin deeply cleft into broad flaps, the circular of cnidocytes and cnidocysts encircling the canal when present, follows the edge of the mar- exumbrellar margin, characteristic of the Tra- gin of the exumbrellar flaps and is called chymedusae but present also in some species of “peripheral canal system”, whose vertical parts other sub-classes. are the peronial canals. cnidocyte: specialised cell type, usually located in cirrus (cirri): small tentacular-like organ situated on the ectoderm. It consists of a basal nucleus, a dis- the umbrellar margin between the marginal ten- tal cnidocil and contains the cnidocyst; cell walls tacles, solid and devoid of swollen marginal ten- with supporting roots. Typically concentrated in tacular bulbs. Two types are generally found: the tentacles. spiral cirri: coiling spirally, with scattered cnido- cnidome: entire complement of cnidocyst types in a cysts and a terminal cluster of cnidocysts (e.g. given taxon. Mitrocomella). cnidophore: cnidocyst-filled cellular capsules cov-

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ered by numerous long cilia and attached to ten- space within Aglaopheniidae. (see phylacto- tacles by elongated, filiform and very contractile carps). The primary modified hydrocladium, stalks of special structure; characteristic of most rachis or axis of the corbula, is called gonocladi- of the Zancleida (see remarks in Weill 1934 p. um, it bears the first secondary hydrocladium, or 404; Bouillon, 1974), not to be confused with gonohydrocladium, which support the accessory branched capitate tentacles or with the special hydrocladia differentiated in corbulacosta. cnidocysts-bearing processes of Eudendrium corbulacosta (corbulacostae): one of the modified racemosum and E. armatum. hydrocladia of a corbula; also called ribs, they cnidothylacium: cluster of cnidocysts enclosed in an are alternately inserted to the gonocladium. endodermal canals running along the umbrella. cordylus (cordyli): minute, marginal, club-shaped coenosarc: the living tissue of a hydroid colony, the structures situated on the umbrellar margin living tubes connecting the various polyps of a between the tentacles. With a narrow peduncle colony, formed by ectoderm, mesoglea and endo- and a thick distal portion, either hollow or com- derm, typically covered by perisarc. pletely filled by endoderm, with cnidocysts or coenosteum: calcareous exoskeleton in hydrozoan not, function unknown, probably sensory (e.g. colonies (i.e. Milleporidae, Stylasteridae), bear- Laodiceidae, Tiarannidae). ing pores for the gastrozooids (gastropores), corm: contracted nectosome and siphosome of the dactylozooids (dactylopores) and “nemato- Rhodaliidae forming a globular mass below the phores” (nematopores). In Stylasteridae the tex- pneumatophore. ture of the coenosteum is either a reticulate maze cormidium: in thecate hydroids, a repeated unit of or a series of straight parallel, longitudinal bands the cladium comprising an internode, one of calcium carbonate (= linear coenosteal strips); hydrotheca and usually three nematothecae, these often covered by granules or bear imbricat- delimited by annuli; in siphonophores, an organ- ed scales. The coenosteum has mainly to types of ised group of siphosomal elements, usually texture: reticulate-granular and linear-imbricate. including a gastrozooid, tentacle, palpons (in The two other combinations, i.e. reticulate-imbri- physonects), blastostyle and bracts. cate and linear- granular, are very rare. cormoid: erect polyp-bearing elements of a colony colony: asexually-produced assemblage of zooids that arise from a common hydrorhiza or that have a common coenosarc, deriving from a hydrorhiza-like stem, e.g. one single feather-like single event of sexual or asexual reproduction. structure of a Halopteris colony or a simple stem column: the tubular part of a polyp, excluding the of Antennella species. A cormoid is a hydro- hypostome, the tentacles and, if any, the most caulus, or its homologue, and all accessory struc- basal region. tures. commissural canals: transverse connections of the craspedote: medusae with a velum. nectosac between lateral radial and dorsal canals crenulated: having low rounded cusps or lobes sep- (in Sulculeolaria spp. only). arated by sharp but shallow notches (e.g. of compound sense organ: marginal sense organ mouth lips). formed by an ecto-endodermal ocellus and an cruciform: cross-shaped. open ectodermal statocyst (in the Tiaropsidae). crumpling: see introversion. congeneric: species referable to the same genus. cryptomedusoid: strongly reduced medusa; seldom conspecific: referable to the same species. with free pelagic life (swimming sporosacs, and coppinia: a close aggregation of numerous gonothe- gonophores); without radial canals but with an cae together in a muff-like structure including endodermal lamina lining the exumbrellar ecto- also modified, elongate polyps (presumed defen- derm: the umbrella endoderm (homologous to sive) (e.g. in the Lafoeidae). the cathamnal lamella); subumbrellar cavity corallum: the calcareous skeleton of a colony as a reduced or represented only by an ectodermal whole. layer: the internal ectoderm, germ cells on spadix corbula (corbulae): protective basket-like group of (= manubrium), in eccentric position. modified hydrocladia (called corbulacostae or cusp: distal projection (often called tooth) from the ribs) typically provided with nematothecae, rim of a hydrotheca or a gonotheca. loosely fused or lying closely parallel, bent cuspidellid: hydroid morphologically referable to around and protecting several gonangia in the the nominal Genus Cuspidella. Colonies stolon-

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al; hydrotheca tubular, usually sessile, without entiated connective layer, the mesoglea, usually pedicel; operculum conical, made of several not regarded as a real tissue layer. pleats or cusps meeting centrally, with or without direct development: development where the medusa crease-line at base; differing from “campanulid” stage will give rise to another medusa without in lacking pedicel and diaphragm. passing through a hydroid phase (e.g. Tra- cyclosystem: an arrangement of pores in which sev- chymedusae) or where a hydroid will produce eral dactylopores surround central gastropore in directly another hydroid (e.g. Hydra). calcareous Hydrozoa. distal: at the far end, near the end (opposite = prox- cymba: angular and flattened eudoxid bract, charac- imal). teristic of Abyla spp. ectoderm: outermost cellular layer (epidermis). cymose: colony not growing distally but from suc- ectodermal lamella or lining = ectodermal lamina: cessive lateral branches. see mantle. cyst: generally chitinous, protective structure con- ectodermal statocyst: marginal sense organ of equi- taining eggs, embryos or even portion of an librium developed in the velum and entirely ecto- organism in an inactive stage. Cysts are resting dermal, formed in depressions or pockets of the stages, usually resistant to adverse environmental velum and either remaining open (open ectoder- conditions. They can be either part of the normal mal statocysts of, e.g. Mitrocomidae, Tiaropsi- life cycle or appear depending on circumstantial dae) or being sealed by velar tissues (closed ecto- conditions. dermal statocysts, e.g. the other Leptomedusae). dactylopore: a small pore in the coenosteum of cal- Characterised by special cells or lithocytes con- careous Hydrozoa housing dactylozooids, may taining one or more tiny polygonal or spherical be borne on projections. concretion (statolith = otolith). Closed statocysts dactylostyle: see style. with a basal cushion of cells with sensory cilia. dactylotome: the lateral slits which borders the gas- ecto-endodermal ocelli: photoreceptors found in the tropores tube in Stylasteridae. Tiaropsidae where the cup-shaped mass of pig- dactylozooid (= machozooid): defensive polyp, usu- ment is formed by the endoderm of the circular ally highly extensible and mobile, richly armed canal, the nerve elements being ectodermal. The with cnidocysts, often a reduced and modified ocelli of the other Hydroidomedusa are com- gastrozooid; usually deprived of mouth and pletely ectodermal in origin. In the Tiaropsidae either without or with a reduced number of tenta- the ocelli are associated with open ectodermal cles. Some with characteristic structure (see ten- statocysts forming a compound sense organ. taculozooid, nematophore, sarcostyle and spiral ecto-endodermal statocyst = tentaculocyst = sensory zooid), some with chemioreceptors. club: club-like, sense organ of equilibrium grow- desmocyte: minute chitinous rivet anchoring the ing out of the umbrellar margin in the fashion of skeleton (theca) to the mesoglea of the hydranth a tentacle; formed by an endodermal axis origi- (= punctae or birefringent nodules). nating from the circular canal and covered by the diaphragm: protrusion of the endoderm partitioning umbrellar ectoderm. With one or more distal, the gastric cavity in some hydroids (Corymor- large endoderm cell (lithocytes) each containing phidae); in many thecate hydroids, a thin inward- a solid concretion (statolith). In this form they ly projecting, circular, chitinous shelf at the base are called “free ecto-endodermal statocysts or of the hydrotheca, sometimes an annular thicken- free sensory clubs ” (e.g. Narcomedusae and Tra- ing of a less defined nature occupies the same chymedusae). In some species sensory clubs are position. The centre of the diaphragm is perforat- enveloped by mesoglea or by an ectodermal vesi- ed by a hole by which the ceoenosarc passes. cle embedded in the mesoglea, being called diastemas: a gap, a space between. In the Stylasteri- “closed ecto-endodermal statocysts” (e.g. Lim- dae, when cyclosystems are aging, the dactylo- nomedusae, few Trachymedusae and of a genus pores become obsolete and are filled with of Narcomedusae: Sigiweddelia). coenosteum. The section of cyclosystem missing ecto-theca: ectodermal layer surrounding in some dactylopores is called a diastema. species medusa buds and more generally reduced diploblastic: being composed of two epithelia, i.e. gonophores. formed by an outer ectoderm and an inner endo- egestion: the elimination of undigested food through derm, separated by a kind of relatively undiffer- the mouth opening.

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embayment: a rounded or pointed gap between two with velum; “gonads” on manubrium when adjacent cusps along the rim of a hydrotheca. Anthomedusae, on radial canals when Leptome- embryo: an early developmental stage resulting dusae. Often with short free pelagic life; the first from repeated cleavage and subsequent growth step in medusa reduction. of a zygote. Embryological development passes excretory papillae: papillae situated either between through several stages, such as morula, blastula, marginal tentacles, or at base of some marginal and gastrula, the latter corresponding to the structures (tentacular bulbs, non-tentacular or embryonic stage where the germ layers become rudimentary bulbs, or marginal warts), or on the established first. In the Hydrozoa, the gastrula is radial canals. With an opening, or excretory pore, the two-layered developmental stage in which in contact with the cavity of the bulbs or of the the rudimentary endoderm layer differentiate = gastro-vascular system. Used for the elimination planula. In contrast to larvae, embryonic stages of undigested material. are neither planktotrophyc nor lecythotrophic excretory pore: opening of the excretory papillae. and cannot lead a long independent existence, Sometimes papillae are absent and pores open at except when encysted. the surface of the supporting structures (see endoderm: innermost cellular layer, lines the gas- excretory papillae). trovascular cavities. exumbrella: upper, aboral convex surface of the entocodon = glockenkern = medusary nodule: a umbrella (see umbrella). solid multistratified nodule produced between exumbrellar cnidocyst cluster or band: exumbrellar ecto- and endoderm by an invagination of the specialised tissue in form of oval, club-shaped, apical budding zone during the morphogenesis of spoon-shaped, or elongated patches containing medusa buds or of fixed gonophores, later on cnidocysts, localised immediately above the mar- developing a cavity: the future subumbrellar cav- ginal bulbs (Zancleoidea) or on exumbrellar mar- ity. Endodermal components of buds (manubri- gin between tentacles (e.g. Proboscidactyla). um, gastro-vascular canals) formed by evagina- exumbrellar spur: upwards growth of marginal ten- tion of the “mother” endoderm (spadix). In few tacular bulbs, clasping umbrellar margin (e.g. medusae, budding is exclusively ectodermic Leuckartiara). (Bougainvillia niobe, Lizzia blondina, Hydrac- fascicled: stem comprising two or more coenosarc tinia minima, Rathkea octopunctata), the tubes united in a composite single stem structure entocodon developing both ectodermal and (= polysiphonic). Sometimes fascicled stems are endodermal components of the buds. due to coalescence of colonies deriving from epibolic: a type gastrulation with the smaller cells of several planulae that settled together on the same the animal pole growing down over the vegetal spot. pole cells and enclose them, the large cells filiform: a straight tentacle, lacking prominent becoming the endoderm and forming an archen- cnidocyst clusters, the cnidocyst appearing more teron. or less evenly distributed. epilithic: living on stones or inorganic hard sub- flabellate: fan-shaped hydroid colony. strates in general. flexuose: hydroid with hydrocauli or hydrocladia epiphytic: living on plants, without parasitising with successive internodes directed alternately them. left and right, in a zigzag fashion. Flexuose epizoic: living on animals, without parasitising colonies are usually biseriate, bearing hydranths them. in two opposite, often alternate rows. eudoxid: reproductive stage of calycophorans that frustule: little didermic tissue portion formed asexu- usually becomes detached from polygastric ally either by budding or by constriction, acting stage. Each eudoxid comprises typically a bract, as dormant and/or dispersion stage. Generally a gastrozooid, a tentacles with tentilla, and a suc- formed by polyps, exceptionally by medusae; all cession of sexual gonophores and, possibly asex- develop into polyps. ual gonophores. funnel: an expanded chamber at the bottom of the eumedusoid: reduced medusa with radial canals and pneumatophore where the lining ectoderm is subumbrellar cavity, with or without manubrium; modified to form the gas gland. when present, manubrium not eccentric; general- gas-gland: specialised area of modified ectoderm ly without tentacles, usually with sense organs, which secretes gas to inflate pneumatophore (see

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funnel), the gas gland may be simple (Agalma) or gonangium (gonangia): in colonial hydroids, a branched (Rhizophysa). reproductive unit consisting of the outer gastric cavity: in medusae see manubrial cavity; in gonotheca and enclosed blastostyle bearing one the hydranth, simple undivided enlargement of or many gonophores. the digestive part of the hydranth body. gonodendron: in siphonophores, an organised group gastric peduncle = peduncle: a cone-shaped median of gonopalpons, gonophores and occasionally extension from the subumbrellar mesoglea pro- asexual nectophores, developed from the sipho- jecting downwards into the subumbrellar cavity, some. bearing the manubrium terminally; the radial gonopalpon: a specialised palpon, budded from the canals run down along the peduncle to reach the gonodendron. manubrium; varied in shape and size (e.g. long gonophoral polyp: polyp protruding from the and narrow in Eutima mira; large and pyramidal gonothecal opening of some Halecium species, in Bougainvillia macloviana; very short in perhaps with defense and/or feeding function. Phialopsis diegensis). gonophore: asexual reproductive structure normally gastric pouches: see manubrial pouches. developing into medusa buds; in many Hydro- gastropore: the large pores housing the gastrozooids, zoa, however, the medusae are reduced to a vary- in calcareous Hydrozoa. ing degree and are not liberated anymore, gastrostome: the mouth of the gastropore. remaining attached to the hydroid, or to the gastrovascular system: in medusae the coelenteron siphosome, in the gonophoral structures. They or enteron, comprising the manubrium cavity are then called fixed gonophores, or sporosacs, (stomach) and the gastrovascular canals (i.e., the or fixed sporosacs since they are not released radial and circular canals and their derivatives). anymore. The gonophores give origin to the gen- In hydroids the hydranth cavity and the erative elements, ova or spermatozoa (see coenosarcal canals. It serves for the digestion and medusa reduction). distribution of food, the circulation of oxygen, gonosome: the gonophores and their protective waste, cnidoblasts and even gametes. structures. gastrozooid: feeding polyp with mouth and normal- gonotheca: chitinous structure with a distal opening, ly with tentacles, without reproductive organs. surrounding and protecting a gonophore. gemmule: asexual reproductive body, see cyst and gonozooid: reproductive polyp, male or female, frustule. bearing gonophores; usually a modified gastro- glomulus: in certain Haleciidae, a grouping of sev- zooid at various stages of morphological reduc- eral to numerous laterally contiguous gonothecae tion and often with few or no tentacles. each with a tubular neck, jointly borne on an hermaphroditic: a colony of hydroids is hermaphro- irregularly branched network of tubes. ditic when all its zooids are hermaphroditic; but gonad: an organ such as an ovary or a testis which a colony may functionally be hermaphroditic produces sex cells or gametes. There are no real when composed of both male and female zooids. organs in Hydrozoa, so this term is inappropriate heteromedusoid = sporosac: highly atrophied although largely used by specialists. We use this medusa devoid of radial canals, umbrellar endo- term in brackets, being aware that, in medusae, derm, tentacles and sense organs; internal ecto- “gonads” indicates the place, usually on manubri- derm remnant of subumbrellar cavity still pre- um walls or/and on the radial canals, where the sent. sex cells become mature. The position of the heteromerous segmentation: segmentation of hydro- germ cells has a considerable value in classifica- caulus or hydrocladia by alternate hydrothecate tion. When “gonads” are on the manubrium they and non-hydrothecate segments, oblique and may completely surround it, being cylindrical, or transverse nodes thus alternating. be in interradial, adradial or perradial position. hinge joint: a joint consisting of diamond-shaped When situated on the radial canals, they usually thickenings of the stem perisarc, set obliquely in develop on their lateral walls but, in some the sagittal plane and connected by relatively medusae, they are continuous also over the ven- thin perisarc; it allows some bending in certain tral wall (e.g. Clytia hemisphaerica). Their posi- directions but not in others. The function is to tion along the course of the radial canals is often orientate the colony in a favorable position in a diagnostic character as are their shape and size. respect to food-bearing currents.

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hollow tentacle: tentacle either with a central cavity age these become reduced, losing their opercu- in continuation with the cavity of the tentacular lum and apical part, and are no longer high bulbs or, when these are missing, of the circular enough to accommodate the hydranths (haleciid- canal, or without any lumen but with an endo- like). dermal core formed by several peripheral rows of hypocystic villus (villi): ectodermal processes of the cells (parenchymatic). In the Bythotiaridae the gas-gland or pneumadenia in some Cystonect tentacles are hollow, but the mesoglea of the dis- siphonophores. tal part of the tentacles is often enlarged and hypostome: distal end of the hydranth, carrying the reduces strongly the endodermal axis. mouth at its end. homomerous segmentation: segmentation of hydro- intathecal ridge: small internal perisarc extension caulus or hydrocladia through uniform segments, into cavity of hydrotheca, for structural rein- usually separated by oblique nodes. forcement. homonym: identical names denoting different taxa internode: a segment often dividing hydrocauli and (see International Code of Zoological Nomencla- hydrocladia by partitions or nodes, part between ture for further explanation). two nodes, often delimited above and below by hydranth: the feeding polyp of a hydroid colony. perisarcal annuli. hydrocaulus: main stem of a fixed, erect hydroid interradial: the radial axis lying in between two adja- colony, typically bearing branches, the final of cent perradii; between the radial canals. In Nar- which, or hydrocladia, bearing the hydranths. comedusae the axis between gastric pouches. hydrocladia: final lateral, hydranth-bearing branch intertentacular web = basal web = umbrellula: thin, of the main stem (or hydrocaulus) or of its transparent sheet, often containing cnidocysts, branches, in an erect hydroid colony. connecting the base of the hydranth tentacles of hydroecium: ventral cavity of calycophoran nec- some leptomedusan hydroids. tophore into which the siphosome may be whol- intrathecal septum: internal and transversal shelf or ly or partly retracted. ridge of perisarc inside the hydrotheca. hydroid: the polypoid stage, or prolonged post-plan- introversion = crumpling: the turning inwards of the ula larva, of the Hydroidomedusa. exumbrellar margin and the tentacles into the hydrophore: perisarcal structure at the base of the subumbrellar cavity afterwards closed by the hydranths in some members of the family Solan- velum, often with distal part of manubrium hang- deriidae. Often as two parallel triangular process- ing out. An answer to various excitations like, es. In some Leptomedusae species each hydranth stress, the presence of other medusae, chemicals, arise from a short process situated near the the food, etc.; it depends on excitation of the epithe- distal end of an internode termed hydrophore lial aneural conduction. (apophysis). In Haleciidea protusion or pedicel involucrum: in siphonophores a fold rounds the carrying the hydrotheca. base, or the whole, of a tentillum. hydropore: a hole in the definite floor of hydrotheca, juvenile: a developmental stage which has attained the in Syntheciidae, Sertulariidae and Plumulariidae, adult body plan (i.e., symmetry, general body trough which the coenosarc passes, connects the shape and major functional systems such as loco- hydranth with the rest of the gastrovascular system. motion and feeding), but not sexual reproduction. hydrorhiza (hydrorhizae): all structures by which lappet: a lobe-like extension around umbrellar mar- fixed hydroids are attached to the substratum, gin (some Laingiomedusae, the Narcomedusae). normally in form of a network of branching, larva: in the post-embryonic development of an ani- anastomosed, creeping tubes or stolons; mal, an immature intermediate stage distinctly hydrorhizal tubes may fuse in a mat, becoming different in morphology and physiology from the encrusting or forming other different structures. sexual adult. A complex life cycle can have more hydrotheca (hydrothecae): chitinous structure sur- than one larval stage. In the Hydrozoa, the plan- rounding entirely or partially the hydranth in ula is often referred to as larva, whereas it is most Leptomedusae. more properly defined as a gastrula (either hol- hydrotheca reduction: In some Campanulinida fam- low, coelogastrula, or solid, stereogastrula). In a ilies, for instance the Eirenidae and the strict sense, the larva of the Hydrozoa with a Eucheilotidae, only the newly developed polyps complex cycle is the hydroid, even though, have a completely developed hydrotheca, with through paedomorphosis, many species perform

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sexual reproduction in the hydroid stage, due to extension. In some genera the distal part of the medusa reduction or suppression. mantle may contain cnidocysts, often in large lateral cirri: see cirri. aggregations (= kind of nematophores?). The lateral nematothecae: nematothecae arranged one ligula is presumably a mantle differentiation. A each side of hydrothecal aperture, to which they mantle may also exist in some gonangia of pae- are lateral in position. domorphic Leptomedusae, enveloping temporar- lateral ridges: cross ridges, bordering the apical ily the gonophores. wings, present on some physonect nectophores; mantle canal: in siphonopores, upper and lower there may be apico-lateral, infra-lateral, and ver- diverticula of the pedicular canal at the point of tical-lateral ridges. its entry into a nectophore or gonophore. ligula: an extensile outgrowth armed with cnido- manubrial or gastric cavity (= stomach): central cav- cysts from the base of the adcauline side of ity of the manubrium in connection with the exte- hydranths in some Salacia and Sertularia (a rior by the mouth and ending in the radial canals nematophore? see mantle). openings, delimited by an endodermal layer his- lip: lobe-like extension of manubrial margin sur- tologically divided into several regions, named rounding the mouth (see mouth). Lips may be of according to function: oral, digestive, stomachal, simple or complicated structure (i.e. crenulated, cnidoblastic, or sexuated when the “gonads” folded, short, elongated, pointed, rounded) develop on the manubrium. Rather uniform in armed or not with cnidocysts distributed uni- structure throughout the various subclasses, formly or in clusters. In the Rathkeidae, lips are except in Koellikerina (Bougainvilliidae) where elongated, simple or branched and armed with the endoderm of the gastric cavity presents terminal and usually also lateral cnidocyst knobs. numerous conspicuous endodermal expansions lithocyte: a cell containing a movable concretion or sustained by a mesoglean axis and containing statolith, closely associated with sensory cells, excretory vacuoles. located in a statocyst. (see ectodermal statocyst manubrial or gastric pouch or pocket: lateral perra- and ecto-endodermal statocyst). dial or interradial extension of the manubrial lithostyle: see statocyst. cavity (e.g. in Narcomedusae, Tiarannidae, mamelon: a minute mound or nipple-shaped peris- Gotoea). arc protuberance found on the upper surface of a manubrium: axial didermic projection of the subum- hydrocladia-bearing apophysis. A small aperture brella containing the gastric or stomachal cavity, in the centre communicates with the coenosarc. distally bearing the mouth and proximally lead- Origin and function unclear: either associated ing to the radial canals. Manubria are greatly var- with nematophores Plumulariidae and ied in shape and size, ranging from tubular to Aglaopheniidae, or considered as an atrophied cruciform, quadratic, fusifom, barrel-shaped, hydrotheca in the Halopterididae. flask-shaped, short, long, narrow or very large, mantle: In Porpitidae (Anthomedusae) an outfolding etc. Erroneously considered as synonym with along the float edge of the hydroid stage, proba- stomach (see stomach). bly acting as stabilizer. In Leptomedusae marginal bulbs: see tentacular or non tentacular mar- hydroids (some Sertulariidae and the Thy- ginal bulbs. roscyphidae), the mantle, or ectodermal support- marginal cirri: see cirri. ing lamella or “Haftlamella”, is a thin layer of marginal cnidocyst ring: see cnidocyst marginal ectoderm lining the interior of the hydrotheca. ring. Usually issued from the base of the hydranth, marginal lappet: one in a series of lobe-like exten- wrapping the hydranth completely when with- sions around umbrellar margin (e.g. Narcome- drawn, forming a roofing plate (“deckenplatte”). dusae). Sometimes with specialised regions of attach- marginal tentacle: a tentacle inserted on the edge, or ment to the hydranth and to the hydrotheca. In margin, of the umbrella. some genera a medio-basal annular lamella, the marginal vesicle: see statocyst. annular ectodermal fold, may link, like a marginal wart or swelling: small, wart-like swelling diaphragm, the mantle to the hydranth body, in of the umbrellar margin, never destined to carry other genera the abcauline caecum region is tentacles and not in connection with the circular attached to mantle directly or by a perculiar canal (e.g. Eutima mira).

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marsupium: brood chamber formed by longitudinal mesial (= median) nemathotecae: nematothecae gonothecal ribs, spines or leaves in female located in the vertical mid-line of the hydrotheca, gonophores of some species of sertulariids one below, or median inferior, and one above hydroids (see brood chamber). hydrotheca, or median superior, more rarely on medusa budding: asexual budding of medusae. In ahydrothecate stems, cauline nematothecae, or hydroids, it occurs on the lateral wall of the on internodes. polyp, on the hydrorhiza, on the hydrocauli, on mesoglea: a non-cellular substance lying between the hydrocladia or on specialised structures. the ectoderm and the endoderm; it forms the Common also among hydromedusae; medusa gelatinous bulk of the umbrella (the jelly of jel- buds are formed either on the manubrium, the lyfish) and a lamella-like layer (mesolamella) in radial canals, the marginal bulbs or the subum- polypoid forms. Synonym with extracellular brellar rim. Medusa buds, in the Hydroidome- matrix (ECM). dusa, imply the presence of an entocodon (see modular: consisting of a series of morphologically entocodon). similar structural units. medusa reduction: in many Hydoidomedusae, the monilifiliform: with dispersed small isolated clus- medusa becomes reduced, abortive, not living ters of cnidocysts on the adoral side of the tenta- the colony anymore, the hydroid becoming the cle and with a continuous band of cnidocysts paedomorphic carrier of the sexual cells. Medusa along the aboral side. reduction to fixed gonophores or sporosacs moniliform: a tentacle with a terminal capitation and evolved independently in many Hydrozoa fami- rather regularly spaced conspicuous clumps or lies and has no phylogenetic value. Reduction bands of tall epidermal cells bearing cnidocysts. may be more or less pronounced pending the monopodial: branching pattern of stems in which the species, ranging from stages similar to the adult oldest hydranth remains at the distal end. medusa (free or fixed medusoids) to stages mouth arm: expansion or dilatation of a perradial where all medusan structures fail to develop, the corner of the manubrial mouth rim armed with germ cells being located in the ectoderm of the cnidocyts clusters, usually open, groove-shaped polyp body. Different main morphological stages (e.g. Hydractiniidae). of medusa regression have been recognised and mouth: opening of the gastric cavity to exterior; in described (see: eumedusoids; cryptomedusoid; hydranth, at the end of the hypostome; in heteromedusoid; styloids), they represent the medusae, at the end of the manubrium, simple most typical stages of reduction, with intermedi- and circular or with either simple or complicated ate grades in each type. In many species male lips (see lips). Serves for both ingestion and and female fixed gonophores belong to different elimination (egestion). types of sporosac. Medusa reduction is excep- mouth: see basal lamella. tional in Limnomedusae; at the species level it is neck shield: thin extension of eudoxid bract, partly less common in the Anthomedusae than in Lep- surrounding gonophores. tomedusae where this phenomenon is the rule in nectophore: Asexual medusoid swimming bells, most of the families with conspicuous colonies, grouped together in the apical part of the which never present a real free medusa stages, siphonophores l to form a region called necto- like the: Aglaopheniidae; Clathrozoidae; Haleci- some. Differ from hydromedusae bell by their idae; Halopterididae; Plumulariidae; Sertulari- bilateral symmetry. Velum, radial canals, ring idae; Syntheciidae. The small leptomedusan canal, endodermal lamella, a double nerve ring, colonies are usually characterised by free striated muscles present. Manubrium, tentacles, medusae, the smallest hydroids often producing “gonads”, sense organs absent. Polymorphic, the biggest medusae! serving for propulsion. Absent in Cystonectae medusa: free living, sexual, pelagic adult stage in and in the physonect, Athorybia. the cnidarian life cycle. nectosac: the central cavity of nectophore, opening medusary nodule: see entocodon. to exterior via an ostium and having muscular mesentery: in some species, a perradial tissue layer walls with propulsive function (= subumbrella attaching the lateral walls of the manubrium to cavity). the subumbrella (see: Leuckartiara octona, Neo- nectosome: section of stem bearing the nectophores. turris papua, Pandeopsis ikarii) nematocladium (nematocladia): the upper fused part

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of a corbula rib. superba, Aequorea macrodactyla, and bulbs on nematodactyl: specialised tentacle with glandular which marginal tentacles will develop later on base and bearing a strong cnidocyst armature during medusan growth (developing tentacular (typical of Nemalecium). marginal bulbs, as in Clytia and Malagazziidae). nematocyst: = cnidocyst oblate: flattened at the two poles; in medusae, nematophore: type of highly extensible dactylo- species which contract primarily near bell margin zooid, mainly known in Leptomedusan hydroids, when swimming, producing a low-velocity jet representing a strongly reduced hydranth richly (e.g. Aequorea, Clytia). armed with cnidocysts, without mouth or tenta- ocellus (pl. ocelli): multicellular photoreceptor, cles, with virtual or totally absent gastric cavity, common in Anthomedusae, usually abaxial or either protected (see nemathotheca) or naked. In adaxial on marginal bulbs. Round, oblong or some Aglaopheniids the nematophores have two elongated spots, black, brown, yellow or red, recognised portions, the body of the structure consisting of a small mass or cupule of pigment- also called “sarcostyle” (see sarcostyle) and the ed cells associated with nerve cells. A lens may region bearing the cnidocysts or cnidostyle. In be present. Of ectodermal origin, except in the Stylasteridae see nematopore. (see tentaculo- Tiaropsidae (see ecto-endodermal ocelli). zooid). octant: an eighth of the umbrella; the space between nematopore: small shallow pores in the coenosteum the interradii in a medusa with 4 radial canals. of Stylasteridae housing the “nematophores”, operculum: lid-like structure closing hydrothecae or dense concentrations of long slender cnidocysts gonothecae. Some comprise a single flap, others perpendicular to the branch surface, common have two, three, four or many flaps meeting in the around cyclosystems especially on pseudosepta centre; opercular valves may be simple inwards and lids. folds of the distal part of the hydrothecae (pleat- nematotheca: chitinous theca of varied structure sur- ed), or segments of the primary covering of the rounding a nematophore. In the Plumularioidea hydrotheca seated and hinged in embayments either sessile, immovable and one-chambered (prominent crease-line) of the hydrothecal margin; (monothalamic), or pedicillate, mobile and two- they may be cast away during hydranth growth or chambered (bithalamic). Present also in some after medusa liberation. The term also refers to the anthomedusan hydroids (Merona). lid covering the opening of cnidocysts. neoteny: a type of paedomorphosis due to retarda- opposite: in hydroids, two hydrocladia or hydrothe- tion of somatic development, so that sexual cae that arise on the same level, one pointing to maturity is attained by organisms retaining juve- the right, the other to the left. nile characters. oral tentacle: tentacle arising above the mouth rim of nerve ring: hydromedusae have two nerve rings some medusae with circular mouth. Simple and around umbrella margin, usually on opposite sides located just above the mouth rim in the Cytaeidi- of the velum, separated by a mesoglean lamella: a dae, simple or branched and situated well above subumbrellar one, above velum attachment (inner the mouth rim in the Bougainvilliidae. Tentacles or upper nerve ring) and an exumbrellar one, located immediately below the hypostome of below velum attachment (outer or lower nerve hydroids. ring). The two are connected by neurites. oral: near the mouth, the opposite end being aboral. nettle ring: see cnidocyst ring. ostium: nectosac opening, through which water is node: externally visible constricted section of expelled for propulsion (= velar opening). hydrocaulus or hydrocladium marking junction otoporpae: in some Narcomedusae, vertical, elon- of two internodes (see internode). gated, oval or even rounded ectodermal tracts non-tentacular marginal bulb or rudimentary bulb: with bristles and cnidocysts running upwards marginal bulb developed on the umbrella margin from each statocyst over the exumbrella margin. without bearing tentacles; such bulbs never paedomophosis: acceleration (progenesis) or retar- develop tentacles; others can be the result of ten- dation (neoteny) of somatic development, lead- tacle reduction. It is necessary to distinguish ing to adults retaining juvenile features. between bulbs that are permanently without ten- paedophore: an asexual, larval nurse carrier (i.e. tacles, permanent non-tentacular marginal bulbs colonies of siphonophores, the hydroids) bud- or rudimentary marginal bulbs, as in Cirrhitiara ding of the sexual adults medusoids or medusae.

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pallial canal: section of gastrovascular system which growth, the tentacles remain attached close to the joins the radial canals on nectosac to the pedicu- manubrium and the tentacular ectoderm, main- lar canal or the somatocyst = pedicular canal taining its connection with the umbrella margin, palmate: a form like that of an open palm or hand; in extends on the exumbrella forming the peronia hydroids, a hydrocaulus with largely ascending, (see also tentacular roots). long branches converging strictly or loosely in peronial canal: in Narcomedusae the part of the one plane = thuja-like. peripheral canal system running vertically along palpacle: a small tentacle borne on a palpon in the peronia (see circular canal). siphonophores. perradial: the main radial axes of a medusa, corre- palpon: in siphonophores, a cormidial element, sponding in most species to the radial canals. In probably a reduced gastrozooid, which may have Narcomedusae the axis opposite each gastric sensory or excretory functions? pouch. pedicel: stalk of a hydrotheca, a gonotheca or a phagocytosis: the process by which cells surround, hydranth (= stem, hydroclade); in general, in and engulf, a food particle which is then digest- animals any stalk like structures (= pedicle = ed. The feeding method employed in particular peduncle). by some unicellular protozoans and Cnidaria. pedicle: in zoology a small stalk (= pedicel = pedun- phorocyt: nurse cell. cle). phylactocarps: in some Aglaopheniidae, modified pedicular canal: section of gastrovascular system hydrocladia or appendages to a hydrocladium, which joins the apical point of convergence of forming a protective structure typically armed the radial canals to somatocyst in calycophoran with nematohecae around gonothecae, similar to siphonophores, may present descending, ascend- corbula hydrocladia, but more widely spaced, not ing expansions or even branches. (see mantle fused and less modified. canal) phylactogonium: in some mature Aglaopheniids, peduncle: see gastric peduncle. In general in animals accesory branch of bifurcated hydrocladia bear- any stalk or stalk-like process (= pedicel = pedi- ing the gonangium and its defensive differentia- cle). tions. periderm: mucoproteinic coating (= glycocalyx) of phyllocyst: reduced canal system in an eudoxyd the exposed surface of hydroids and medusae. bract, equivalent to the somatocyst in a nec- Not to be confused with perisarc. tophore. peripheral canal system: see circular canal. phyllozooid: = bract peripheral canal: in some hydroids, longitudinal pinnate: hydroid colony with branches (alternate or peripheral canals of the hydrocaulus, in medusae, opposite) on each side of hydrocaulus, usually see circular canal. nearly in one plane, resembling a feather. perisarc: the chitinous exoskeleton surrounding the planula: an embryonic free-swimming post blastula coenosarc of most hydroids. In the Anthomedusae stage into which most of the Hydrozoa eggs the polyps are usually never surrounded by peris- become directly developed (= gastrula = coelo- arc, in the Leptomedusae they usually are (see gastrula or stereogastrula). Improperly called hydrothecae, gonothecae and nematothecae). larva since, from a developmental point of view, peronia: in Narcomedusae and some Laingiome- it is an embryo (see embryo and larva). Planula dusae, an ectodermal strands at the base of the of Hydrozoa do not feed but live entirely off tentacles rich in cnidocysts, muscles and nerves. yolk, the planulae of some species have zooxan- The peronia are formed by the fusion of subum- thellae. Attached to substratum by their usually brellar and exumbrellar ectoderm without inter- broader anterior end. position of mesoglea. At the base of the peronia Fig.lets: see coenosteum. the margin of the umbrella remains curved, giv- plumose: hydroid colony with closely arranged lat- ing the umbrella its lobed, scalloped appearance eral branches, usually in one plane (see pinnate). (marginal lappets). The peronia and the exum- pneumadenia: gas-gland at the base of the pneu- brellar position of the tentacles result from devel- matophore cavity. opmental circumstances; during Narcomedusae pneumatocodon: outer ectodermal wall of the pneu- development, the endodermal core of the tenta- matophore separated from the inner wall or cles issues from the manubrium; when umbrella pneumatosaccus by gastrovascular space lined

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by endoderm, containing muscle fibers. pseudosepta: radially arranged ridges between the pneumatophore: apical gas-filled float, present in dactylozooids of a cyclosystem. Cystonectae and Physonectae; in the latter its ptera: lateral aliform expansions in the gastrozooids function can be for orientation rather than buoy- of the rhizophysid physonect genus Bathyphysa ancy. Derived directly from the larval stage, quadrant: a quarter of the umbrella; the space probably represents a highly modified polyp. In between perradii in a medusa with 4 radial some species the gastrovascular cavity may be canals. divided by vertical septa clothed with endoderm radial canal: canal leading from the perradial corners (Anthophysa). of the manubrium to the circular canal. Usually pneumatosaccus: inner ectodermal wall of the pneu- straight and narrow, with smooth sides. In some matophore, separated from pneumatocodon by species large, ribbon-like (e.g. Amphinema) and gastrovascular space and typically lined by a with jagged outgrowths (e.g. Leuckartiara). Typ- chitinous layer (see pneumatocodon). ically four, but more numerous in many podocyst: multicellular capsule from nipped-off por- medusae, exceeding sometimes more than 100 tions of coenosarc, functioning as a cyst. (e.g. Aequorea). Normally simple, but in certain polygastric stage: in siphonophores, the complete species branched and sometimes whose branches animal bearing both asexual and reproductive never reach the circular canal (e.g. Staurodiscus). elements (nectosome and siphosome). Generally growing centrifugally, from the polymorphic: bearing different morphs (in hydroids: manubrium to the circular canal, except in a few gastrozooids, gonozooids, dactylozooids, etc.). species where they arise centripetally (e.g. polyp: basic individual of the hydroids; may either Melicertoides; the centripetal canals). be isolated or form colonies; represented by dif- Siphonophore nectosacs have four radial canals ferent types, such as hydranths, gonozooids and linked by the ring canal. They are unequally dactylozooids. developed and their point of convergence is only polysiphonic = fascicled: a hydroid stem made of exceptionally at the apex of the nectosac. more than one coenosarc and perisarc tube. ramified capitate: branched tentacles with a capita- primary polyp: the hydranth formed by the develop- tion on each branch. ment of a newly settled planula. renovation: a new hydrotheca developing within an proboscis: hypostome in a hydranth. old one, sometimes repeatedly, resulting in a tier progenesis: a type of paedomorphosis due to accel- of hydrothecae one within the other; sometimes eration of the gonad development, so that sexual only the hydrothecal margin renovates. maturity is attained by organisms retaining juve- rete: (rete mirabile) in siphonophores a flattened, nile characters. disc-shaped expansion on a canal; function prolate: lenghtened in the direction of the polar unknown. diameter; in medusae, species which contract rhizocaulomic: stolonal colonies with erect over their entire length when swimming, produc- hydrorhiza formed by a bundle of parallel ing a high velocity jet: i.e., Aglantha, Sarsia. stolons. propagule: any asexual or sexual morph leading to rhizoid: in hydroids, lateral rootlike structure attach- propagation. ing the stolon to the subtratum proximal: at the near end, towards or at the base of ring canal: see circular canal. attachment. ring fold: see annular ectodermal fold. pseudofiliform: tentacles with scattered cnidocysts ring palisade = cheval-de-frise: In Stylasteridae ring in a relatively low epidermis along the adoral of tiny, blunt spines projecting from the wall of side and a concentration of cnidocysts in tall epi- the gastropore tube at the level of the gastrostyle dermis on the aboral side. tip. It constricts the gastropore tube in a lower pseudohydrotheca: a film-like, often gelatinous, gastrostyle chamber and an upper funnel-shaped flexible coat covering partly or entirely the part leading to the branch surface. When the gas- hydranth body of some Anthomedusae hydroids, trostyle is absent, the ring palisade forms a solid it has little form and adheres closely to the ring constricting the gastropore tube in a small hydranth ectoderm, not homologous to the peris- flat lower chamber, which contains the bulk of arcal hydrothecae but apparently similar in func- the gastrozooid and a larger spacious upper tion (e.g. some bougainvilliids and pandeids). chamber into which the dactylozooids enter.

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rudimentary bulb: see non-tentacular marginal bulb. colony. sail: thin erect, sail-like structure extending across spermatophore: a compact mass or packet of sper- surface in Velella. matozoa either liberated as such or transferred to sarcopore: see sarcostyle. a female. sarcostyle: specialised type of nematophore found spherule = locule = basal space: a globular region of mainly in the Plumularioidea and exceptionally in pedicel directly beneath hydrotheca, formed by a few other families, naked, emerging through a two adjacent annular constrictions. hole of the perisarc (sarcopore) or protected by a sphincter (isthmus): cellular structure at the aboral minute nematotheca, or sarcotheca. Mobile, end of hydranths that can be closed so to allow armed with cnidocysts, some distally rich in adhe- localised digestion of prey and to prevent the sive gland cells and playing a role in phagocytosis transfer of too large prey pieces from the gastric or in cleaning the surrounding perisarc. Body of cavity to the lumen of the stolonal system; in the nematophores in some Aglaopheniids. Campanulariids and Eudendriids also to the con- sarcotheca: see sarcostyle. striction of the base of the hypostome. scapus: a structure similar to coppinia but lacking spine: one of numerous chitinous spines projecting the protective elongate polyps. from perisarc-covered hydrorhizal network. Also scutum: Fig. or shield-like process. one in the series of minute spines on tubule of semifiliform: tentacle with a capitation stretched cnidocysts. towards the aboral side. spiral zooid: modified polyp without mouth, with a semimoniliform: tentacle with a large capitation and gastric cavity, bearing either terminal cnidocyst numerous small cnidocyst clusters on the adoral side. aggregations or stout cnidocyst knobs or very sensory club: see ecto-endodermal statocyst. short tentacles richly armed with cnidocysts and septum: an internal partition, for instance an inward tending to twist or coil into spiral, characteristic projection of hydroid perisarc which may occur of some Hydractiniidae (a type of dactylozooid). in the stolon, hydrocaulus, hydrocladium or spiral: colony appearance due to spiral arrangement hydrothecae. of hydrocladia around the main stem. shaft: see butt. sporosac: reduced type of gonophore remaining siphon: unusual specialisation for attachment and fixed to the hydroid and in which the sex cells strengthening, seen in Hartlaubella gelatinosa ripen directly, of different types (see eumedu- and some other hydroids, consisting of an unseg- soids, cryptomedusoids, heteromedusoids and mented tubular outgrowth of hydrocaulus, styloids). resembling a stolon, running back from the distal spur canal: reduced longitudinal canals in gastrovas- end of each segment of the main hydrocaulus cular system of siphonophore prayid eudoxid toward the base of the colony and closely pressed bracts; in medusae, see exumbrellar spur. to the main stems; the siphon branch out basally statocyst = lithostyle = tentaculocyst = sensory club: into the substratum and ends blindly. see ectodermal statocyst and ecto-endodermal siphosome: in siphonophores, section of the stem statocyst. below nectosome, usually long, bearing statolith = otolith: minute concretion composed of cormidia. organic material and minerals, mainly calcium solid tentacle: tentacle without central cavity, with carbonate, enclosed within the lithocytes of sta- an endodermal core formed by a single row of tocysts, their movement stimulates sensory disk-like or superimposed cylindrical vacuolated receptors (see ectodermal statocyst and ecto- cells (see chordal). endodermal statocyst). somatocyst: in calycophoran siphonophores, promi- stem: in hydroids, a general term for any main erect nent extension of the stem into the nectophore structure which can bear hydrocladia or may contain oil droplets. hydranths; in siphonophores, the stem or stolon spadix: the central finger-shaped core formed by an is divided in two distinct regions (see stolon). evagination of the “mother” endoderm, covered stolon: in hydroids, creeping or erect hollow tube by entocodonial ectoderm, forming the manubri- protected by perisarc and containing the same um in a medusa or supporting ripe sex cells in ecto-endodermal tissues of the polyps most of the reduced gonophores (see sporosacs). (coenosarc), generally adhering to the substrate Its central cavity is continuous with that of the forming a complex system, or hydrorhiza. Under

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adverse environmental conditions only the reproductive structure of the medusa: radial stolons of many colonies survive, acting as rest- canals, circular canal, velum, sense organs, with ing stages until proper conditions return. In maturation of the sexual cells according the siphonophores, the stolon or stem is an extensile classes (on manubrium in Anthomedusae on or not, ecto-endodermic tube (coenosarc) along radial canals in Leptomedusae) and with a non which the various types of zooids are borne, eccentric position of the manubrium. Found organised down such that two distinct regions mostly in Leptomedusae families with paedo- can be recognised the nectosome and the sipho- morphic hydroids characterized by the posses- some (only one the siphosome in Cystonect), sion of fixed and highly reduced gonophores; both forming the polygastric stage. some are known in Anthomedusae (e.g. Pachy- stolonal colonies: colonies where the growth is hor- cordyle). izontal and the hydranths arise directly or from swimming sporosac: liberated sporosac with a non short unbranched pedicels from a common medusoid swimming apparatus (ex. Dicoryne). creeping hydrorhiza. synonym: two or more names applied to the same stomach: internal pouch or cavity of the manubrium taxon. Synonymised species or genera are said or of the hydranth in which food digestion is ini- conspecific or congeneric. tiated. Often erroneously used instead of synonymy: the list of synonyms applied to a taxon, manubrium (see manubrium, manubrial or gas- other than the currently accepted name. tric cavity). tabulae: in Milleporidae, horizontal calcareous Figs. straight: hydroid colony with a non-flexuose main crossing the cavities of the gastropores and stem, either biseriate (with hydranths in two dactylopores, the most recent secreted tabula cor- opposite rows) or uniseriate (with hydranths in a responds to the level of the alive part of the single row). coenosteum. striated muscle: a muscle with striated fibers, in tentacle: usually highly contractile cnidocyst-bear- Hydrozoa present in the subumbrella of medusae ing processes with sensory, defending, feeding or reduced gonophores. and occasionally anchoring functions. In the style: in some calcareous hydrozoans, upright spine medusae, the tentacles are usually on the umbrel- at the base of gastropore, occasionally also in la margin = marginal tentacles, or on exumbrella. dactylopore. They may also occur around the mouth = oral styloid sporosac: the most regressed type of tentacles; in hydroids, the tentacles may be locat- gonophore, without internal ectoderm and ed immediately below the hypostome = oral ten- umbrellar endoderm; reduced to a single evagi- tacles and/or in one or more distinct rings on the nation of the two germ layers, between which the hydranth body = aboral tentacles or even scat- genital elements accumulate. tered over the whole body. Tentacles types vary subumbrella: see umbrella. according to the distribution of cnidocyst arma- subumbrellar cavity: see umbrella. ture; the most common types are capitate, cateni- subumbrellar surface: see umbrella. form, filiform, moniliform, pseudofiliform, ram- sucker: adhesive structure in medusae, located either ified capitate. along or at the tip of the tentacles or at the tip of tentaculae: small solid marginal tentacles (usually specialised stalk-like structures, usually lacking without marginal bulbs, but in contact with the cnidocysts. circular canal) located between normal hollow swimming gonophore: pelagic stage derived from tentacles (e.g. Amphinema rugosum). strongly reduced medusa stages (cryptomedu- tentacular marginal bulb: in most Antho- and Lep- soids and perhaps heteromedusoids) developing tomedusae, a dilated portion of the proximal part as free gamete carriers; usually without radial of a marginal tentacle, next umbrellar margin, canals and circular canal (present in Anthohebel- contains a cavity in communication with the cir- la); without tentacles; without sense organs; with cular canal and with the tentacular cavity of hol- sexual elements always on “manubrium” even in low tentacles. Of various shapes, mostly simple Leptomedusae, the manubrium or spadix in but in some medusae compound, originating sev- eccentric position. They can not been confused eral tentacles (e.g. Hybocodon, Bougainvillia); with eumedusoids, the first step of medusa they perform digestive activities; are centers of reduction, still with most of the original non cnidoblast formation and, in some species, bear

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ocelli. In Anthomedusae and Leptomedusae a new the umbrella is the umbrellar margin. marginal tentacle is normally preceded by the for- umbrellula: see intertentacular web. mation of a bulb on which it will develop (see vasiform: vase-shaped, with broad base and slender marginal bulb). In some medusae there are no true top. tentacular bulbs: i.e. in the Limnomedusae, Nar- velar ridge: in calycophoran siphonophores, dorsal comedusae, Trachymedusae, in the majority of the cross ridge parallel to the ostium, on nectophores Bythotiaridae, in the Anthomedusae Eugtoea of Gilia reticulata and some Lensia species (e.g. petalina and Rhabdoon singularis. Lensia lelouveteau) tentacular root: projection of the endodermal tentac- velar: of the velum. ular core into the umbrella mesoglea (Blackfor- velum: horizontal fold projecting inwards from dia, Obelia, some Limnomedusae, Trachyme- umbrellar margin, living a central, circular hole, dusae and the Narcomedusae) (see peronia). the velar opening. It consists of two layers of tentaculiform structure: solid marginal structure ectoderm separated by a thin mesoglean lamella; resembling tentaculae, without marginal bulb the inner ectoderm, of subumbrellar origin, pos- and with no contact with circular canal (exclu- sesses striated muscles. The velum serves in the sive to Orchistomatidae). propulsion and the orientation of the medusa, by tentaculocyst: see ecto-endodermal statocyst. acting like a photographic diaphragm, during tentaculozooid: reduced dactylozooid similar to ten- swimming the medusa can adjust the diameter of tacle in structure, with a solid core of chordal its aperture, which can become as wide as the endoderm and no mouth or gastric cavity, richly umbrella or almost closed. (in Siphonophores armed with cnidocysts and often with chemosen- often called ostium). sory receptors; very extensible and contractile. veronica: in siphonophores, a spiral movement tentilla: in siphonophores, side branches of the gas- which spreads the tentacles into a characteristic trozooid tentacle, bearing expanded terminal pattern. aggregations of cindocysts (see cnidoband). verticillate: arranged in a succession of whorls, theca: chitinous extension typically protecting any whorled. kind of polyp. zooid: in colonial hydroids, any of several types of thecate: name for the hydroid stage of the Leptome- individual polyps: dactylozooids, gastrozooids, dusae, usually with thecae protecting hydranths gonozooids etc. and gonophores. zooxanthellae: unicellular algae, living in symbiotic thread: hollow thin tube coiled inside cnidocyst cap- association in the tissues of many Cnidaria. sule. Turned inside out when discharged. Dis- charged threads may be differentiated into a proximal dilated section, shaft or butt, and a thin- ACKNOWLEDGEMENTS ner distal section, the thread or tubule. thrust block: in physonect siphonophores, aboral The publication of this book has been partially sup- section of a nectophore, separating apical wings ported by a grant of the Spanish Ministerio de Ciencia and abutting against nectosomal stem. y Tecnología, REN2002-11397-E). This study was transverse commisures: = commissural canals. partially supported by a PEET project of the National trophosome: all structures of a colony except the Science Foundation of the USA, by COFIN and FIRB reproductive ones. projects of MIUR, and by the Provincial Administra- tubule: see thread. tion of Lecce. J.B. gratefully acknowledges the finan- umbilical canal: see apical canal. cial support of the “Foundation Universitaire David umbrella: main body of medusa, excluding manubri- and Alice Van Buuren”, he is greatly indebted to Mr um and tentacles; generally resembling a bell or Jean-Philippe Bouillon for some of the medusa draw- an umbrella. Shapes: bell-shaped, bowl-shaped, ings, and finally last but not least he thanks his wife dome-shaped, flat, hemispherical, pointed, “Janine” in whose time this work has been done, saucer-shaped, tall, turreted. The outer, generally mainly for her patience and daily support. We are convex, surface is the exumbrellar surface indebted to Jordi Corbera for permission to reproduce (exumbrella); the inner concave surface is the his drawings previously published in Pagès et al. subumbrellar surface (subumbrella), the concav- (1992), Pagès and Gili (1992), Gili et al. (1998b, c, ity being the subumbrellar cavity. The edge of 1999) and Bouillon et al. (2000).

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