Org. Divers. Evol. 6, Electr. Suppl. 6: 1 - 104 (2006) © Gesellschaft für Biologische Systematik URL: http://www.senckenberg.de/odes/06-06.htm URN: urn:nbn:de:0028-odes0606-0

Halacaroidea (Acari): a guide to marine genera

Ilse Bartsch

Forschungsinstitut Senckenberg, Deutsches Zentrum für Marine Biodiversitätsforschung, Notkestr. 85, 22607 Hamburg, Germany

Corresponding author, e-mail: [email protected]

Received 13 December 2004 • Accepted 8 July 2005

Abstract

Halacarid mites (Halacaroidea: Halacaridae) are meiobenthic organisms. The majority of species and genera are marine, only few are restricted to freshwater. Halacarid mites are present from the tidal area to the deep sea. It is the only mite family completely adapted to per- manent life in the sea. The first record was published more than 200 years ago. At present, 51 marine and brackish water genera of halacarid mites are known, including more than 1000 species. The genera are Acantho- halacarus, Acanthopalpus, Acarochelopodia, Acaromantis, Acarothrix, Actacarus, Agaue, Agauides, Agauopsis, Anomalohalacarus, Areni- halacarus, Arhodeoporus, Atelopsalis, Australacarus, Bathyhalacarus, Bradyagaue, Camactognathus, Caspihalacarus, Coloboceras, Co- lobocerasides, Copidognathides, Copidognathus, Corallihalacarus, Enterohalacarus, Halacarus, Halacarellus, Halacaroides, Halacaropsis, Halixodes, Isobactrus, Lohmannella, Metarhombognathus, Mictognathus, Parhalixodes, Pelacarus, Peregrinacarus, Phacacarus, Rhombo- gnathides, Rhombognathus, Scaptognathides, Scaptognathus, Simognathus, Spongihalacarus, Thalassacarus, Thalassarachna, Thalass- ophthirius, Tropihalacarus, Werthella, Werthelloides, Winlundia, and Xenohalacarus. The guide, which includes marine and brackish water genera, starts with an introduction to methods of collection, extraction and examination of halacarid mites, an outline of the external morphology and life history, and an overview of the commonly used terminology. Both a dichoto- mous key and tabular keys to the genera are presented. The keys have been prepared on the basis of adults. In general, in adults and nymphs the outline of idiosoma, gnathosoma and legs is similar, whereas the outline of plates, the sculpturing and number of setae on idiosoma and legs differ. In the tabular keys idiosoma, gnathosoma, palps, legs, tarsi and shape of claws are treated separately. The major part of the guide deals with descriptions of the 51 genera. Each genus is diagnosed and illustrated, namely a dorsal and ventral aspect of the idiosoma, the gnathosoma, leg I and tarsi I, II and IV. The diagnoses mention both, characters expected to be relevant in a phylogenetic sense and those thought to be mainly correlated with environment and mode of life. Rare character variants are included in the diagnoses; more variants are expected to be found in the future. In addition to the diagnoses, short notes are given on biology and geographi- cal distribution, on similar-looking genera, and distinguishing characters. At the end of the presentation of a genus, relevant and most recent descriptive or phylogenetic references are listed. Keywords: Halacaroidea; Acari, General introduction; Marine genera; Keys; Diagnoses

Introduction The first record of a marine mite (‘insecta marina’) have been described, and the family Halacaridae is from coralline algae of a seashore was published given the rank of a superfamily Halacaroidea. more than 200 years ago (Baster 1758: pl. 10, fig. 7). Halacarid mites are meiobenthic organisms within a A century later, Gosse (1855) introduced the generic length range from 150 µm to about 2000 µm. Halacarids name Halacarus for marine mites, and Murray (1877) can be found at altitudes of 5000 m (freshwater established the family Halacaridae for mites ‘living halacarids in lakes and springs) as well as at depths habitually under the sea’. Since those days, more than of 7000 m (marine mites in deep-sea trenches). They 1000 species in 51 marine and 13 freshwater genera generally live in submerged habitats, but a few species

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 2 are adapted to survive in the splash zone. Halacarids are stirring with hot water is recommended. A minority present at all latitudes, from polar to tropical regions. of species has a hydrophobic cuticle; these mites are Halacarid mites live in a variety of substrata: within trapped at the water surface film when the sample is tufts of algae, on large fronds, in and on colonies of treated with air bubbles. Techniques using density sponges, hydrozoans, bryozoans, barnacles, mussels, gradient separation can also be used when extracting polychaetes, in interstices of coarse sediment or mites, with a flotation medium prepared from cooking flocculent ooze, amongst surface structures and gill salt, sugar or colloidal silica polymers. filaments of crustaceans and molluscs, and between The material held back in the fine-mesh sieve is spines and in the gut of echinoderms. Some few species placed in a petri dish or narrow-channel sorting dish and are known or suspected to be parasites. Halacarids scanned for halacarids under a dissecting microscope are rare or absent in silty sediments, oxygen-free (magnification: 12–25x). If possible, sorting should be habitats, and biotopes regularly defaunated due to done whilst the mites are alive, crawling around in the heavy pollution, destruction of the substratum, extreme dish and thus more conspicuous. Halacarids may be temperatures or desiccation. Several species of marine badly fouled with debris attached to idiosoma and legs. halacarids inhabit brackish waters, with rare records The mites can be cleaned somewhat by allowing them even from freshwater habitats. to run around in sand. In preserved sediment samples, The keys below deal with genera described from staining with rose bengal will facilitate sorting. marine and brackish water habitats. Genera widespread Ethanol (70%) should be used for fixation and stor- in fresh water (salinity less than 0.5 ‰) are not included. ing. Formalin hardens the mites and the necessary The drawings of the genera are generalized; rare clearing will be difficult. exceptions in external characters are excluded. Both For detailed examination, the mites have to be cleared a tabular and dichotomous key are given, as each has and mounted on slides. The halacarids are placed into a advantages and disadvantages. The references given at clearing medium, pepsin or lactic acid; gentle warming the end of each chapter or genus are only recent and (40–50 °C) may facilitate the clearing. The gnathosoma major ones. is torn off using a sharp needle, and body contents are squeezed out by applying gentle pressure with a blunt Collection, extraction and examination needle. Material stored in formalin for several years In intertidal and shallow subtidal zones, collecting by should be transferred into glycerine-acetic acid (with hand at low tide is recommended. Colonies of mussels, 2% acetic acid); after 1–3 months, the contents of the polychaetes, barnacles, bryozoans and hydrozoans are idiosoma can be dissolved with lactic acid. Animals scraped off; algal tufts, holdfasts and fronds, shells or with very delicate plates should not be left in acetic pebbles covered with unicellular algae, fine and coarse acid or lactic acid for more than a few hours. deposits from a beach surface as well as from deeper Permanent mounting media are glycerine jelly, glyc- layers, or rooted saltmarsh sediments are gathered; erine or Hyrax. Careful sealing of the coverslips with 50–500 ccm of the substratum may yield hundreds of a standard microscopical sealing agent, marine epoxy halacarid mites. From the sublittoral, collections can paint or nail varnish is necessary. Berlese, modified be made with trawl, dredge and grab. Halacarids inhab- Hoyer's fluid or polyvinyl lactophenol can be used iting the flocculent ooze are collected with epibenthic for temporary mounts but are not recommended for sleds. permanent slides. Specimens cleared in lactic acid The mites are extracted from the substratum by wash- have to be rinsed (in glycerine) to prevent subsequent ing. Large algal fronds, stones, decapods, or echinoids crystallization in the permanent mount. Over-cleared are washed in a bucket with a strong jet of water; specimen can be stained with chlor-azol black. To allow subsequently the washing water is poured through a a microscopic examination of both sides, mounting be- 60–100 µm sieve. Algal tufts and colonial organisms tween coverslips is recommended. The coverslips can are placed in a series of sieves, a 1–2 mm mesh sieve be stored in a metal slide frame or attached to a glass over a 60–100 µm sieve, and washed with a jet of water. slide with a drop of glycerine. Sediment samples are either stirred vigorously in water, References. Newell (1947, 1984), Green and and the supernatant water decanted through a 60–100 MacQuitty (1987), Bartsch (1988a, 1993a). µm mesh sieve, or placed in a separatory funnel where lighter particles (such as halacarids) are elutriated by External morphology (Figs 1A, B, 2A–F, 5E) a water stream and retained in a sieve at the outflow. The body of an adult halacarid is divided into idiosoma, As intertidally living species are resistent to extreme with four pairs of legs, and gnathosoma, with palps and conditions, shock techniques with fresh water, ice water chelicerae. or anaesthetizing media may prove to be inefficient. The idiosoma is typically covered with sclerotized For sediment samples from exposed shores, subsequent plates, the dorsal plates are: the anterior dorsal plate

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 3

(AD), pair of ocular plates (OC), and posterior dorsal third palpal segments (P-1, P-3) are short, the second plate (PD) (Fig. 1A). The ventral plates are: the anterior and fourth segments (P-2, P-4) often long. Fusion and epimeral plate (AE, by fusion of epimera I and II, EI, reduction of palpal segments occur. The chelicerae are EII), pair of posterior epimeral plate (PE, by fusion of elongate, in some genera stylet-shaped. They end with epimera III and IV), and genitoanal plate (GA, by fu- a movable, generally claw-like ventral digit and a fixed sion of the genital and anal plate, GP and AP) (Fig. dorsal flap. 1B). The plates are separated by areas of striated (mem- Adult halacarids have four pairs of legs. The two braneous) integument. Occasionally plates are divided, anterior pairs, legs I and II, are directed forward, legs III reduced or enlarged and fused to a dorsal or ventral and IV backward. The six segments of the legs of adults shield. Measurement of length and width generally are trochanter, basifemur, telofemur, genu, tibia, and presented in species description are outlined in Fig. 2E tarsus. Leg segments, particulary the telofemora, may and F. have elaborate ridges or lamellae. The tarsi often have a The idiosomal plates may be smooth, uniformly dorsal cavity, the claw fossa, with its fossa membranes. porose, panelled, or bear porose areolae. The dorsal The setae of the legs may be smooth, branched or plates often have raised areas or longitudinal costae pectinate, long and delicate or short and spiniform. The (Fig. 2A) with a sculpturing different from that of ventral setae of the tibiae often are bristles or spines, the remainder. Often these areas include rosette which are smooth or pectinate. The tarsi bear at least pores which typically consist of numerous canaliculi three dorsal setae, viz. one basal and two distal (often arranged around a blindly ending central pore (ostium paired) fossary setae (Fig. 2C). At the tip of tarsus I, as and alveolus) (Fig. 2B). The AD sometimes bears well as in most tarsi II, there is a pair of parambulacral a frontal spine, the OC often two corneae. On the setae (pas), short hollow (eupathid) setae which are dorsum there are six (rarely fewer or up to 10) pairs of single, doubled or multiplied. The pas on the posterior idiosomatic setae (ds), up to five pairs of gland pores tarsi may be fili- or spiniform singlets, or even lacking. and a pair of pore canaliculi (lyrifissures, slit-organs, Tarsus I has a dorsolateral solenidion and a famulus. ring apodemes). The posteriormost pair of dorsal setae, The former is hollow, setiform, bacilliform or clavate, called adanal setae, is mostly situated on the anal plate. small or almost as long as the dorsal fossary setae. The The number of setae and gland pores may be reduced. famulus, adjacent to the solenidion, is short, digitiform The AE typically has three pairs of ventral setae, the or papilliform, but often reduced to a tiny cap at the end PE one dorsal (or lateral) seta and two or three ventral of an afferent canal. The solenidion of tarsus II is in setae. In some genera the AE bears a pair of epimeral dorsolateral, dorsal or dorsomedial position. pores (external, Fig. 1B), epimeral vesicles (internal, The tarsi terminate in a central sclerite and paired Fig. 5E), or merely tubes (internal). The genital opening claws. The flexible portion between the end of tarsus (GO), situated on the GP, is covered by a pair of genital and the central sclerite may include a rod-like sclerite sclerites and surrounded by perigenital setae (pgs). or carpite (Fig. 2D). The central sclerite often ends Small setae, the subgenital setae (sgs), are inserted on with a minute uni- or bidentate process, called median the genital sclerites. The number of sgs and pgs of males claw. Rarely the median claw is as long as, or even usually surpasses that of females. Internal structures longer than, the adjoining paired claws. The latter may are the female ovipositor, the male spermatopositor be smooth or armed with an accessory process and/or (spematophorotype), and in both sexes of most genera claw pecten. In two genera the paired claws are absent 1–3 pairs of genital acetabula. The idiosoma generally from tarsus I. ends in the anal cone with its anal sclerites. References. Newell (1947, 1984), Green and The gnathosoma consists of a gnathosomal base, MacQuitty (1987), Bartsch (1993a), Abé (1998). rostrum, palps and chelicerae. On the ventral side of the gnathosomal base there is a more or less distinct Life history pharyngeal plate with its internal panels and markings Halacarids generally are oviparous. The mites run from muscle attachments. On the dorsal side a through one larval and one to three nymphal stages tectum (epistome) bridges the trough of the rostrum. (proto-, deuto-, tritonymph) before they moult to Commonly there are two pairs of maxillary setae the adult. Most species have separate sexes; females (trito- and basirostrals), and two pairs of rostral setae often slightly outnumber males in a given population. (proto- and deutorostrals). The maxillary setae are on Parthenogenetic reproduction is documented in just the gnathosomal base or rostrum, the rostral setae at one species. Most species have a univoltine life cycle, the apex of the rostrum. The palps are attached either with either short or prolonged periods of reproduction. lateral or dorsal to the gnathosomal base. The majority In general the fecundity is low. Temperature and day of genera have four-segmented palps; the first and length influence the cycle of reproduction.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 4

The larvae have six legs, each with five segments. The Fungi found in halacarid carcasses apparently coloniz- outline and size of the plates greatly differ from those ed the mites after their death. of adults; a genital plate is lacking. The setation of the References. Lohmann (1889, 1893), Krantz (1970), ventral idiosomal plates and the legs is incomplete. Bartsch (1974), MacQuitty (1984). Protonymphs have eight legs; legs I to III are six- Terminology, abbreviations and methods segmented, leg IV is five-segmented. A genital plate, with one pair of genital acetabula, is present but is accessory process = tiny process at arc of paired smaller than in adults. The chaetotaxy is incomplete. claws. Deuto- and tritonymphs have eight six-segmented adanal setae (ads) = posteriormost pair of dorsal idioso- legs. In the majority of species, the dorsal and ventral matic setae inserted on anal cone (mostly in dorsal plates are smaller than in adults; the genital plate may position) or adjacent on posterodorsal plate. be fused with the anal plate forming a genitoanal plate; adjunct setae = marginal setae on AE and PE in addi- the genital opening is primordial. The number of setae tion to the general setation. on the idiosoma and legs often resembles that of the anal cone = end of idiosoma with anal sclerites. adults. anal plate (AP) = plate with anus which is guarded by Larvae have a life span of a few days, nymphal stages pair of anal sclerites. live a few weeks or several months, adults five to nine anal sclerites = pair of cusps flanking the anus. months. Quiescent periods, when the mite develops anterior dorsal plate (AD) = one of the dorsal plates. into the next stage, are called pupal stages. anterior epimeral plate (AE) = ventral plate, by fusion Males produce elaborate spermatophores which of epimera I and II. are attached to the substratum or to other mites. The areola = area on dorsal and ventral plates with an or- females stick the eggs firmly to or into the substratum namentation different from remainder of plates. inhabited. In species with a short period of reproduction, Areolae porose or panelled, often raised. a female normally contains 10–20 eggs at the same basifemur = second leg segment. time, and the eggs are deposited in groups. Females of basirostral setae = basalmost pair of maxillary setae. psammophilous genera bear a single large egg, and one bipartite genitoanal plate = plate with anterior trans- or two additional small ones; the large egg often has an verse portion coarsely striated, ornamentation of elaborately textured membrane. remainder of plate resembling that of AE and PE. References. Lohmann (1889), Straarup (1968), camerostome = opening receiving the gnathosoma. Kirchner (1969), Bartsch (1972), Siemer (1996). carpite = rodlike sclerite between tip of tarsus and cen- tral sclerite. Food and feeding central sclerite = sclerite articulating with paired claws The chelicerae of halacarids can move to and fro and tip of tarsus (or carpite); central sclerite often within the rostral trough, they are made for cutting bearing a claw-like process or median claw. and piercing cells rather than for grinding. Halacarids cerotegument = superficial layer. apparently feed by sucking up their food material chelicerae = first pair of appendages on gnathosoma. which presumably has been subjected to pre-oral claw = claw-like structure at the end of tarsi. Tarsi II digestion. The pair of first legs, enlarged and provided to IV always with a pair of claws and often with a with spines, are well suited to capture and hold prey more or less distinct median claw (claw-like pro- organisms. Highly modified legs probably signify a cess of central sclerite). strong prey specificity. Species with their guts intensely claw fossa = dorsal cavity at end of the tarsi in which filled with green material certainly are phytophagous. the claws can be retracted. In most halacarids the gut contents are pale or slightly deutonymph = second nymphal stage. brown; these mites are thought to be predators and deutorostral setae = pair of setae near tip of rostrum. scavengers, feeding on tissue of macrofaunal species, dorsal setae (ds) = idiosomatic setae on dorsum of idi- on meiofauna, protozoans, or on fungi and bacteria. A osoma, inserted on the dorsal plates or within the few species are known or suspected to be parasites. striated integument. Halacarid populations are reduced by predators, epicuticula = surficial layer on the procuticula. carnivorous invertebrates, amongst others also by other epimera or epimeral plates (E) = ventral plates with cox- halacarids, and small fishes, by destruction of their ae included. substratum and physical and chemical environmental epimeral pore = circular, oblong or slit-like structure disturbance. Halacarids may be infested by epizoa between epimera I and II; with internal tube. (suctorians, peritrich ciliates) and epiphyta (unicellular epimeral vesicle = large internal follicle with a slit-like green algae, diatoms). Endoparasites are not known. opening between epimera I and II.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 5 eupathidia = small, ‘hollow’ sensory setae at the tip of posterior epimeral plate (PE) = plate by fusion of legs. epimera III and IV, generally with large ventral famulus = sensory seta on tarsus I, often reduced to and marginal but small dorsal portion. small pore and afferent canal. protonymph = first nymphal stage. femur = leg segment, in adults divided into basi- and protorostral setae = pair of setae near tip of rostrum. telofemur. rosette pore = type of porosity consisting of a central fossa membrane = membrane on one or both flanks of pore (ostium) surrounded by small canaliculi. the claw fossa. rostral setae = two pairs of small setae at tip of rostrum genital acetabula (genital acetabulum) = tube- or suck- (proto- and deutorostrals); may be transformed to er-like structures, usually inside the genital ope- barbs. ning. rostrum = a trough in which chelicerae slide forward genital foramen = genital opening. and back; rarely rostrum spatula-shaped or lamel- genital opening = oval area on the venter, in general lar. surrounded by a genital plate. Present only in solenidion = minute sensory seta at tip of tarsus; al- adults. ways present on tarsus I and II. genital plate (GP) = ventral plate with genital opening, spermatophore = stalked capsule with sperm sac. often fused with anal plate. spermatophorotype = spermatopositor. genital sclerites = a pair of sclerites guarding the geni- spermatopositor = spermatophorotype; internal cuticu- tal opening. lar structure, mould for spermatophore. genitoanal plate (GA) = plate by fusion of genital and subgenital setae (sgs) = small setae inserted on the gen- anal plate. ital sclerites. genu = fourth leg segment. tarsus = sixth leg segment. gland pores = dorsal (marginal) pores; majority of ge- tectum = dorsal roof of gnathosoma bridging the rostral nera possess four or five pairs of such pores; inter- trough. nal glands, opening to the exterior through these telofemur = third leg segment. pores, in a few genera conspicuously enlarged. tibia = fifth leg segment. gnathosoma = anterior part of the body, resembling a tripartite genitoanal plate = plate divided into three head. transverse portions; middle portion coarsely stri- idiosoma = posterior portion of the body with legs. ated. lyrifissure = pore canaliculus. tritonymph = third nymphal stage. maxillary setae = generally two pairs of setae, inserted tritorostral setae = pair of maxillary setae. either on base of gnathosoma or on rostrum (trito- trochanter = first leg segment. and basirostral setae). ventral setae (vs-1, vs-2, etc.) = ventral setae on idio- median claw = claw-like process of central sclerite. soma. ocular plates (OC) = paired dorsal plates, often with Abbreviations: AD = anterior dorsal plate; ads = adanal corneae and eye spots. setae; AE = anterior epimeral plate; AP = anal plate; outlying setae = perigenital setae which lie outside the ds = dorsal setae on idiosoma, numbered ds-1 to ds-6 arrangement of the other setae. from anterior backward; E = epimeron or epimeral ovipositor = inverted tubular structure often extending plate, EI to EIV; GA = genitoanal plate; GO = genital beyond GO; everted when depositing eggs. opening; GP = genital plate; OC = ocular plate(s); P = paired claws = present on tarsi II to IV, may be absent palp, P-2 to P-4, second to fourth palpal segment; pas = from tarsus I. parambulacral setae; PD = posterior dorsal plate; PE = palps (P) = pair of appendage on gnathosoma, four- to posterior epimeral plate; pgs = perigenital setae; sgs = two-segmented or even absent. subgenital setae; vs-1, vs-2 = ventral setae on idiosoma, parambulacral setae = small setae at tip of tarsus; ma- numbering from anterior backward. Leg segments and jority of genera with these setae paired; on tarsi I epimera are numbered I to IV, leg segments 1 to 6; e.g. and II parambulacral setae usually eupathid and I-6 = tarsus of leg I. doubled. In the tabular keys idiosoma, gnathosoma, legs, tarsi, perigenital setae (pgs) = setae surrounding the GO. and shape of claws are treated separately. The keys pore canaliculus = present on ocular plates and on anal have been prepared on the basis of adults. In general, in plate (lyrifissure, slit organ, ring apodeme). adults and nymphs the outline of idiosoma, gnathosoma posterior dorsal plate (PD) = one of the dorsal plates. and legs is similar, whereas the outlines of plates, the

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 6 sculpturing and number of setae on idiosoma and legs Tabular keys (Table 1) differ. Each given option includes a combination of Idiosoma and gnathosoma, dorsal aspect (Fig. 3) characters, and this combination should be represented A. Idiosoma slender (length more than 2.3 times width); in the given specimen. 2 anterior and posterior pairs of legs inserted near The diagnoses present a combination of characters ends of idiosoma, and interval between insertions (a) expected to be relevant in a phylogenetic sense, of legs II and III more than 1.3 times width of though they might be difficult to discern, and (b) easily idiosoma. Insertion of leg III towards posterior recognized but thought to be mainly correlated with third of idiosoma. Gnathosoma directly attached environment and mode of life. The number of dorsal to idiosoma; seen in dorsal aspect (Fig. 3A). idiosomatic setae will include the adanal setae (ads or B. Interval between insertions of legs II and III almost ds-6); their position is given separately. The numbers of equal to, or less than, 1.3 times width of idiosoma. setae of a given leg segment, from I to IV, are separated Insertion of leg III about halfway between ends of by a comma, the number of dorsal/ventral setae of a idiosoma. Gnathosoma directly attached to idio- leg segment by a slash. Unless stated otherwise, the soma and distinct in dorsal aspect (Fig. 3B). tarsal formula includes the solenidia but excludes the C. Interval between insertions of legs II and III equal famulus. The solenidia may be almost as long as the to, or less than, 1.3 times width of idiosoma. In- dorsal fossary setae, or be very small and hence easily sertion of leg III about halfway between ends of escape notice. The famulus is always small. idiosoma. Gnathosoma attached to idiosoma via Broken lines in the figures indicate characters (setae, flexible neck (Fig. 3C). spines, segmentation) not present in all given genera or D. Interval between insertions of legs II and III less species. In the diagnoses and in Table 1, rare variants than width of idiosoma. Gnathosoma short, direct- are enclosed in parentheses, square brackets [] enclose ly attached to idiosoma, directed to ventral and in possible misinterpretations, and a question mark (?) dorsal aspect completely or mostly concealed by means the character state is in need of confirmation. anterior portion of idiosoma (Fig. 3D). Idiosoma, dorsal aspect (Fig. 4) A. Idiosoma slender, 2 anterior and posterior pairs of legs inserted near ends of idiosoma; interval be- tween insertions of legs II and III at least 1.3 times width of idiosoma. AD and PD present, PD may be divided into right and left half or reduced to small plate. OC small (less than 50 µm in length and in general less than half length of AD), may be divided or absent (Fig. 4A). B. Interval between insertions of legs II and III equal to, or less than, width of idiosoma. Dorsum with 4–5 pairs of gland pores, one pair in marginal (ventromarginal) position (Fig. 4B), situated within striated integument (rarely on PE). AD, PD and OC present. Dorsal plates lack raised porose areolae or costae. PE with dorsal (marginal) seta anterior to leg III but none anterior to leg IV. C. Interval between insertions of legs II and III equal to, or less than, width of idiosoma. Dorsum with 5 pairs of gland pores, one pair in marginal position. AD present, though margins may be obscured by epicuticula. PD absent (Fig. 4C). OC absent or present. D. Interval between insertions of legs II and III equal to, or less than, width of idiosoma. Dorsum with 4 or fewer pairs of gland pores. AD, PD and OC pre- sent; OC more than 35 µm in length, plate may be divided. Two or more dorsal plates may be fused.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 7

Table 1: Halacarid genera and their character states. Parentheses () enclose rare variants; character states in square bra- ckets [] may be misinterpretations; a question mark (?) means that the character state is in need of confirmation.

Idiosoma Idiosoma, Iidiosoma, Gnatho- Gnatho- Palps, Legs, Legs, Tarsus I, Tarsus IV, Claws and dorsum venter soma, soma, shape shape setae setae setae gnatho- dorsal ventral and soma setae

Figure 3 4 5 6 7 8 9 10 11 12 13 Genus

Acanthohalacarus B D C D A E A C E E A Acanthopalpus B D C D A A A A C A B Acarochelopodia B D A D A A D A C A F Acaromantis B F E B J N E H B D F Acarothrix B D D D A H A F C A A Actacarus B E C D A E A G C A B A Agaue B D G H C D C (D) E (H) A B D E A A Agauides B E C D D I A D H C F A Agauopsis B D (C) D D A E F G A (C) A (D) C E A D A Anomalohalacarus A A A D D A B D H D G C (D) A A Arenihalacarus A A A D A B H G C A A Arhodeoporus B D D D A (C) H (I?) A D G C A D A Atelopsalis B D E D J L A B D C A A Australacarus A A C D G H J A D E C A (F) A Bathyhalacarus B D C D A E A D E A D E A Bradyagaue B G (C) H D C E H (A) B D (C) E A D Camactognathus B D C D A H A F D G B A A Caspihalacarus B D C D A E A D E A A Coloboceras B D C D J L A D E D (G) A Colobocerasides B D C D G H J A D E C A A Copidognathides B D D D A J I J A E B A A Copidognathus B D D D A B H A C (A) E (G) C A B (D) A Corallihalacarus C D C D A I C F H A D Enterohalacarus B D C C K O A C H A A Halacarellus B D C D A E A A D F C D E A D E A Halacaroides A A B D A E A G C A A Halacaropsis B D D D A E H A E D A Halacarus B B C E H C G D A A H A F (K) A D E A C Halixodes B H C D E E B D E A A Isobactrus D D A C D A H A (H) F G I J A B I Lohmannella B B D C A (D) A C A (C) D C F I A D E G I Metarhombognathus B D A B J E A F A A K Mictognathus B D C D A G [I] C F B H A A Parhalixodes A A A D F I A G B A D Pelacarus B D D D D I A F B A A

Peregrinacarus B D C D A E A A D H A A Phacacarus B D D D A H A C E C A A Rhombognathides B D C D J J A F A A I J Rhombognathus B (D) D (A) C D A H A F I A I Scaptognathides B D (E) D D H M G F I A G Scaptognathus B D (E) D F A I M A D E G C B A A (C) Simognathus B F E B J K (E) F H B D E Spongihalacarus B D D C L P A A B A D Thalassacarus B D C D A E A F E A A Thalassarachna B B E C D A B E A A D K A D G A Thalassophthirius B D C D A H F F H A A Tropihalacarus B D C D A E [H] A D E A D A Werthella B D D D D I A C E F B C A A Werthelloides B D C D F I A D H A A Winlundia B D C D A H A D C A A Xenohalacarus B E D D A B A D G F H

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PE with 0–8 dorsal (marginal) setae anterior to leg F. EI and EII fused, AE with epimeral pores. GA bi- or III, none anterior to leg IV (Fig. 4D). tripartite (Fig. 5F). E. Interval between insertions of legs II and III equal G. EI and EII forming an AE. Neither epimeral pores to, or less than, width of idiosoma. AD and PD nor epimeral vesicles present. Female genital plate present, large, surface smooth, delicately porose with pair of raised, crescent-shaped cerotegumen- or reticulate. OC small (less than 35 µm in length) tal areas (Fig. 5G). (Fig. 4E), fused with PE, or absent. PE with dorsal H. EI and EII fused, forming an AE. Neither epimeral (marginal) seta anterior to leg III but none anterior pores nor epimeral vesicles present. Genital plate to leg IV. smooth, punctate or reticulate. Length of PE at F. Interval between insertions of legs II and III equal least 1.6 times that of AE; medial opposing mar- to, or less than, width of idiosoma. AD and PD gins straight (Fig. 5H). present, large, surface coarsely foveate. OC short, triangular or reduced to elongate sclerites (obscu- Gnathosoma, dorsal aspect (Fig. 6) red in coarsely striated integument) (Fig. 4F). A. Palps attached dorsally (Fig. 6A); interval between G. Interval between insertions of legs II and III equal P-1 in general less than 0.8 of width of P-1 (P-1 to, or less than, width of idiosoma. Dorsum with may be fused). Gnathosomal base longer than 4 or fewer pairs of gland pores. AD, PD and OC wide, or cubical and as long as wide. Palps longer, present. PE with dorsal (marginal) seta anterior to just as long as, or rarely somewhat shorter than, leg III and 1–2 setae anterior to leg IV (Fig. 4G). gnathosomal base. H. Interval between insertions of legs II and III equal B. Palps attached dorsally, interval in general less than to, or less than, width of idiosoma. Dorsum with width of P-1. Gnathosomal base globular. Palps (5–)4 or fewer pairs of gland pores. AD, PD and as long as or shorter than gnathosomal base (Fig. OC present. PE with dorsal (marginal) seta(e) an- 6B). terior to leg III but none anterior to leg IV. Dorsal C. Palps inserted dorsally, interval between P-1 greater and epimeral plates with cerotegumental lamellae than width of P-1. Palps distinctly shorter than (Fig. 4H). rostrum (Fig. 6C), or absent. D. Palps attached lateral to rostrum, interval between Idiosoma, epimeral plates and genital plate (Fig. 5) P-1 almost equal to, or greater than, width of P-1. A. EI and EII of right and left side fused but in the Palps as long as or longer than rostrum (Fig. 6D). median separated by striated integument. A sepa- Rostrum long and slender, or reduced to small rate median plate may be present. EIII and EIV of cone. either side partly or completely fused and forming a pair of plates (PE). EII and EIII may be conti- Gnathosoma, ventral aspect (Fig. 7 ) guous. Epimeral pores present or absent. Genital A. Rostrum triangular or parallel-sided. With 2 pairs of plate reduced (Fig. 5A) or large. maxillary setae, either both pairs on rostrum or 1 B. EI and EII fused, forming an AE. Epimeral pores pair on gnathosomal base and 1 pair on rostrum. lacking. Each of PE with longitudinal fissure (Fig. In species with long, parallel-sided rostrum the 5B). two pairs of maxillary setae distinctly separated. C. EI and EII forming an AE; this plate may be fused No barbs at tip of rostrum. Palps 4-segmented, as with one or more ventral plates. Neither epimeral long as or longer than rostrum (Fig. 7A). pores nor epimeral vesicles present (Fig. 5C). EIII B. Rostrum triangular or parallel-sided. With three or and EIV of either side partly or completely fused. more pairs of maxillary setae, 2 or more pairs of Pair of PE (EIII and EIV fused) less than 1.6 ti- setae on gnathosomal base, 1 pair on rostrum (Fig. mes length of AE; its opposing margins triangular. 7B). No barbs at tip of rostrum. Palps 4-segmen- Genital plate smooth, punctate or reticulate. ted, as long as or longer than rostrum. D. EI and EII fused to an AE, which may be fused with C. Rostrum slender, parallel-sided, longer than gna- one or more posterior ventral plates (PE, GP). AE thosomal base. One pair of maxillary setae on with epimeral pores or small slits. GA smooth, gnathosomal base, 1 pair on rostral base, the 4 reticulate, with porose areolae but without raised setae situated almost equidistantly (Fig. 7C). Pair cerotegument or markedly differing transverse of setae on rostrum often short, even minute, and sculpturing (Fig. 5D). in dorsolateral margin of rostrum. Barbs at tip of E. EI and EII fused, AE with pair of epimeral vesicles rostrum, if present, seen only at high magnifica- (Fig. 5E).

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tion. Palps 4-segmented, as long as or longer than G. 4-segmented. P-2 with 1 seta in distal half. P-3 with rostrum. spine or seta. P-4 with 1–2 setae (Fig. 8G). D. Rostrum triangular or parallel-sided, about as long H. 4-segmented. P-2 with 1 seta in distal half. No spine as gnathosomal base. One pair of maxillary setae or seta (with alveolus) on P-3. P-4 with 3–4 setae on gnathosomal base, 1 pair on rostral base, the in basal whorl (Fig. 8H) (rarely these setae situa- 4 setae situated almost equidistantly. No barbs at ted in posterior half). tip of rostrum. Palps 4-segmented, as long as or I. 4-segmented. P-2 with 1 dorsal seta in distal half. longer than rostrum (Fig. 7D). No seta on P-3. P-4 with 0–2 setae in basal half E. Rostrum parallel-sided. Maxillary setae inserted al- (Fig. 8I) (rarely seta moved to apex). most equidistantly. Rostral tip with 2 pairs of dis- J. 3-segmented. Second segment with 1 dorsal seta tinct barbs (Fig. 7E). Palps 4-segmented, as long but no apophysis. Apical segment with 0–3 basal as or longer than rostrum. setae (Fig. 8J). F. Rostrum parallel-sided. Rostral tip with 1 pair of K. 3-segmented. Second segment with 1 bristle-like barbs (Fig. 7F). Palps 4-segmented, about as long ventral seta and often an apophysis (may be lack- as rostrum. ing), 3rd segment with 1 basal seta (Fig. 8K). G. Rostrum stylet-shaped. Palps 3- or 4-segmented L. 3-segmented. No seta on 2nd segment (Fig. 8L). (Fig. 7G). Apical segment with 1 or more setae. H. Rostrum slender, parallel-sided. Palps 2-segmented M. 2-segmented (rarely seemingly 3-segmented), reach- (Fig. 7H). ing to or beyond end of rostrum. Apical segment I. Rostrum spatula-shaped or lamellar. Palps in gen- with 2 or more spines (Fig. 8M). eral 2-segmented, rarely with 3 segments (Fig. N. 2-segmented. Short. Apical segment with ventral 7I). and dorsal bristle (Fig. 8N). J. Gnathosoma short, conical, gnathosomal base glob- O. 2-segmented. Short. Apical segment with small se- ular, wider than long. Rostrum hardly longer than tae at its tip (Fig. 8O). wide, shorter than gnathosomal base. Palps short, P. Palps absent, represented by setae only. 2- or 3-segmented (Fig. 7J) (rarely with a wedge- Shape of legs (Fig. 9) like 4th segment). K. Rostrum triangular. Palps less than 1/5 of gnathoso- A. Genu I shorter than both telofemur and tibia I; its mal length (Fig. 7K). length less than 0.7 times length of telofemur. L. Rostrum triangular. Palpal segments reduced (Fig. Telofemora and tibiae often cylindrical, someti- 7L). mes wide but not club-shaped; prominent mem- branes or lamellae lacking. Tarsus I often shorter Palps, shape and number of setae (Fig. 8) (numbers given than but not distinctly dissimilar from following exclude the small apicalmost spurs and setulae) tarsi (Fig. 9A). A. 4-segmented (P-3 may be very short). P-2 with 2 B. Genu I shorter than both telofemur and tibia I. Leg setae; both setae in posterior half of that segment segments slender, cylindrical or club-shaped. Telo- (Fig. 8A). P-3 with spine. P-4 with 3 or more setae femur I with cerotegumental lamellae (Fig. 9B). in basal whorl (1 may be spiniform). C. Genu I shorter than both telofemur and tibia I. Telo- B. 4-segmented. P-2 with 1 basal and 1 apical seta femora I and II, or III and IV, or all, with large (Fig. 8B). P-3 with spine or seta. P-4 with 3 or cuticular ventral lamellae or a combination of more setae. ventral and articular lamellae; lamellae almost C. 4-segmented. P-2 with 1 basal and 1 apical seta (rar- half height of telofemur (Fig. 9C). ely with 1 or more spiniform ventral processes). D. Genu I shorter than both telofemur and tibia I. Tib- P-3 with spiniform process (no seta). P-4 with ia I with narrow base, then widened. Tarsus I cy- small spine and 2 or more setae (Fig. 8C). lindrical, slender, at least 6 times longer than high D. 4-segmented. P-2 with 1 basal seta. P-3 with spine. (Fig. 9D). Tarsus I much more slender than tarsi II P-4 with 3 setae in basal whorl (Fig. 8D). to IV. E. 4-segmented (3rd segment may be reduced to a E. Genu I distinctly shorter than both telofemur and wedge). P-2 with 1 seta in posterior half. P-3 with tibia I. Tibiae claviform, with narrow base. Tibia spine or seta (Fig. 8E). P-4 with 3–4 setae (gen- I with short, narrow base then abruptly widening; erally situated in basal half), 1 of which may be height in basal half at least 3 times that of the spurlike. base. Tarsus I short, about as long as high, rotated F. 4-segmented. P-2 with 1 seta in distal half. P-3 with inward (Fig. 9E). divaricate spine. P-4 with 3 setae in basal whorl F. Genu I distinctly shorter than both telofemur and (Fig. 8F). tibia I. Tibiae claviform, with a cylindrical, nar-

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row base. Tibia I with greatest height in distal half E. With 3 dorsal setae, a seti- or claviform solenidion, (height about 2.5–3 times that of the base) (Fig. and 1 ventral or ventromedial spine or seta, mostly 9F). Tarsus I at least twice as long as high. in basal half or middle of segment, separated from G. Genu I distinctly shorter than both telofemur and tib- the following 3–20 short ventral setae (eupathi- ia I. Telofemur I very large, its length and height dia) (Fig. 11E). Famulus shorter than solenidion, almost twice that of tibia I (Fig. 9G). lamelliform or inconspicuous. H. Genu I approximately as long (0.7-1.1 times) as telo- F. With 3 dorsal setae, a seti- or claviform solenidion, femur I and tibia I (Fig. 9H). Leg I often longer or 2 or more bristle-like ventral setae in middle of wider than leg II. segment, and apical eupathidia (Fig. 11F). Famu- lus small. Legs, shape and chaetotaxy (Fig. 10) G. With 3 dorsal setae and a setiform solenidion. Pair A. Leg I generally wider and longer than leg II. Telo- of strong ventral setae in middle of segment; femur I with 1–5 spines; spines blunt or tapering, small apical eupathidia lacking (Fig. 11G). Famu- smooth, pectinate or divaricate. Tibia I with 3–8 lus small. bristle-like setae or spines (Fig. 10A). H. With 3 dorsal setae, a seti- or claviform solenidion, B. Leg I markedly wider than leg II. Telofemur I and no ventral seta(e) in basal half but 2–20 setae longer and wider than telofemur II, spines lacking or eupathidia in apical half of tarsus (Fig. 11H). though spiniform lamellae may be present. Tibia I Famulus shorter than solenidion. with pair of ventral spines (Fig. 10B). I. With 3 dorsal setae and a setiform or claviform C. Both telofemur and tibia I with numerous (15 or solenidion, but no ventral setae. Famulus much more) dorsal plus ventral setae (Fig. 10C). smaller than solenidion (Fig. 11I). D. Telofemur I with ventral seta(e) but without large J. With 4 dorsal setae and claviform solenidion; no spine(s). Tibia I with 4–9 ventral setae, which may ventral setae. Famulus much smaller than soleni- be spiniform, pectinate or slender (Fig. 10D). dion. (Fig. 11J). E. Telofemur I with 1–5 ventral setae but no large K. With 4 or more dorsal setae, a setiform solenidion, spines. Tibia I with 3 ventral setae (Fig. 10E), ti- 1–2 spiniform ventral setae, and 2 or more eupa- bia II with 2–3 ventral setae. thidia (Fig. 11K). F. Telofemur I with 1–3 ventral setae but no large spi- nes. Tibiae I and II each with 2 ventral setae (in Chaetotaxy of tarsus IV (Fig. 12) ventral and ventromedial position) (Fig. 10F). A. With 3 dorsal setae, no ventral setae. Tip of tarsus G. Telofemur I with 2–5 dorsal but no ventral setae. with pair of pas, rarely with single, unilateral pas; Tibia I with 1–5 ventral setae (Fig. 10G). pas spini-, seti-, filiform or plumose (Fig. 12A). H. Telofemur I with 1–2 dorsal but no ventral setae. B. With 4 dorsal setae, no ventral setae. Tip of tarsus Tibia I with 1 ventral spine (Fig. 10H). Tibia II with pair of seti- or spiniform pas (Fig. 12B). with 2 ventral setae. C. With 3 dorsal setae, no ventral setae. Tip of tarsus without pas (Fig. 12C). Chaetotaxy of tarsus I (Fig. 11) (parambulacral setae ex- D. With 3 dorsal setae, 1–2 ventral setae. Tip of tarsus cluded) with unilateral or pair of pas (Fig. 12D). A. With 3 dorsal setae, a seti- or claviform solenidion, E. With 3 dorsal setae and 3 or more bristle-like ventral a similar-sized famulus, and 1 apical spiniform setae. Tip of tarsus with pair of pas (Fig. 12E). ventral seta (Fig. 11A). F. With 3 dorsal setae, one or more ventral setae. No B. With 3 dorsal setae, a small seti- or claviform sole- pas at tip of tarsus (Fig. 12F). nidion and a single ventral seta or tapering spine, G. With 4 or more dorsal setae and 1–5 ventral setae. often at about mid-segment (Fig. 11B). Shape of Tip of tarsus with pair of pas (Fig. 12G). famulus different from that of solenidion. C. With 3 dorsal setae, a seti- or claviform solenidion, Claws (Fig. 13) 1 ventral or ventromedial spine or spur in basal A. All tarsi with paired claws. These claws either sim- half, and a single or pair of eupathidia near the lar-sized on all legs, or claws of tarsus I shorter tip (Fig. 11C). Famulus lamelliform or inconspic- and often slightly wider than those of following uous. tarsi. Paired claws smooth, with accessory process D. With 3 dorsal setae, a seti- or claviform solenidion, and/or pecten; pectines of tarsus I may be less de- 2 short ventral setae or spurs in basal half of seg- veloped than on posterior tarsi. Median claw, if ment, and a pair of eupathidia apically (Fig. 11D). present, less stout than paired claws and less than Famulus lamelliform or inconspicuous, shorter half their length (Fig. 13 A). Central sclerite of than solenidion. tarsus I articulating with end of tarsus.

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B. All tarsi with paired claws. Paired claws of tarsus 2b. Palps 2- to 4-segmented, at least as long as rostrum. I shorter, median claw longer than claws of fol- Idiosoma less than 1500 µm long...... 3 lowing tarsi. Paired claws and median claw of 3a. Size of median and paired claws of tarsus I very dif- tarsus I almost similar-sized (Fig. 13B). Central ferent from that of tarsus II. Paired claws of tarsus sclerite of tarsus I articulating with end of tarsus. I much more slender than median claw, or absent. C. All tarsi with paired claws. Median claws of tarsi Paired claws of tarsus II as long as or longer than III and IV more than half length of paired claws median claw; median claw may be absent...... 4 (Fig. 13C) and longer than median claw of tarsus 3b. Paired claws of tarsus I at least as long as, generally I. Median claw of tarsus I less than half length of longer than, median claw. Paired claws of tarsus paired claws. II similar in length or longer than median claw; D. All tarsi with paired claws. On all tarsi median claw median claw may be absent...... 6 large, as wide or wider (Fig. 13D) than paired 4a. Tarsus I slender, 6 times longer than high; ending claws and at least half length of paired claws. with a single small median claw. Tarsus I ventral- Central sclerite articulating with end of tarsus. ly with 1 long seta and 2 short eupathidia. Tibiae E. All tarsi with paired claws. Size of claws of tarsus with 5–6 strong, bipectinate bristles. Palps 4-seg- I dissimilar from that of following tarsi. Paired mented; P-2 with 2 setae...... Acarochelopodia claws of tarsus I much more slender than median 4b. Length of tarsus I 1–4 times its height. Tarsus I with claw (Fig. 13E). Paired claws of tarsi II to IV wi- large median claw; paired claws absent or slender. der than those of tarsus I; their median claw minu- Tarsus I with 1 wide ventral seta but no eupathi- te. dia. Tibia I with one wide ventral seta, tibiae II F. Tarsus I with median claw, paired claws absent (Fig. to IV with 2 bristle-like ventral setae. Palps 2- or 13F). Tarsi II to IV with large paired claws; me- 3-segmented, 2nd segment with 1 ventral and 0–1 dian claw from minute to almost as long as paired dorsal seta...... 5 claws. 5a. Tarsus I as long as high and ending with single me- G. Paired claws of tarsus I large, umbrella-shaped (Fig. dian claw. Tibia I with narrow cylindrical basis; 13G). Claws of tarsi II–IV scythe-shaped, single longer than telofemur I. Rostrum short, conical; tooth or tines of pectines on claw shaft. palps 2-segmented, 2nd segment with 1 dorsal and H. Paired claws of tarsus I with long tines arranged 1 ventral seta. OC reduced to elongate sclerite. along claw shaft; length of tines may reach one- ...... Acaromantis third of length of claws (Fig. 13H). Claws of tarsi 5b. Tarsus I ending with median claw and slender paired II–IV with distinctly shorter tines. claws (the latter may be difficult to discern). Tar- I. All tarsi with paired claws, these smooth, with ac- sus I in general longer than high (exceptions do cessory process and/or with pecten. Central scle- exist !); palps 3-segmented; 2nd segment with 1 rite small, without claw-like process (Fig. 13I). ventral but no dorsal seta. OC subtriangular or re- Tarsi I–IV with carpite between end of tarsus and duced to elongate sclerite...... Simognathus central sclerite. 6a. Tines of claws I distinctly larger than those of claws J. All tarsi with paired claws. Median claw of tarsi I II to IV. Longest tines at least one third of length and II half or less than half of length of paired of claw...... 7 claws (Fig. 13J), median claw of tarsi III and IV 6b. Tines of claws I absent, smaller than, or similar in either smaller than those of tarsi I and II or absent. size to, those of claws II to IV...... 8 Tarsi I–IV with carpite between end of tarsus and 7a. Tines of claws I arranged umbrella-like. Rostrum central sclerite. slender, parallel-sided, about as long as gnathoso- K. All tarsi with three large claws; median claw more mal base. Palps 2-segmented, with 4 apical spurs. than half length of paired claws (Fig. 13K). Tarsi ...... Scaptognathides I–IV with carpite between end of tarsus and cen- 7b. Tines of claws I arranged J-shaped. Rostrum slen- tral sclerite. der, parallel-sided, 4 times longer than gnathoso- mal base. Palps 4-segmented...... Xenohalacarus Dichotomous key to the genera 8a. Gnathosoma attached to idiosoma via long flexible 1a. Palps reduced, represented by setae only. neck...... Corallihalacarus ...... Spongihalacarus 8b. Without flexible neck between idiosoma and gna- 1b. Palps present, with 2–4 distinct segments...... 2 thosoma. Gnathosoma may be concealed by ante- 2a. Palps 2-segmented. Segments slender, cylin- rior portion of idiosoma...... 9 drical, their length less than half that of ros- 9a. Idiosoma slender, at least 2.3 times longer than trum. Idiosoma approximately 2000 µm long wide. Two anterior and two posterior pairs of legs ...... Enterohalacarus

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inserted near ends of idiosoma; interval between nerally less than half width of P-1 (rarely about insertions of legs II and III at least 1.3 times width width of P-1)...... 17 of idiosoma. OC absent or reduced to sclerites 16b. Palps lateral to gnathosomal base (major part of less than 50 µm in diameter. Gnathosoma slender, P-1 seen in ventral aspect); distance between P-1 at least 2.5 times longer than wide...... 10 more than half width of that segment...... 18 9b. Length of idiosoma less than 2.3 times its width. In- 17a. Rostrum slender and parallel-sided. Palps 4-seg- terval between insertions of legs II and III almost mented, P-4 with small spur but without large spi- equal to, or less than, width of idiosoma. Gnatho- nes. Both pairs of maxillary setae on rostrum. AE soma slender or wide...... 14 with (3–)4 pairs of setae...... Lohmannella 10a. Genu I about as long (0.8–1) as adjoining telofe- 17b. Rostrum spatula-shaped or lamellar, its apex wide mur and tibia. Parallel-sided rostrum with blunt and truncate. Palps 2-segmented (rarely seeming- tip; both pairs of maxillary setae in posterior two ly 3-segmented), with 2 large apical spines. Both thirds of rostrum...... 11 pairs of maxillary setae on rostrum. AE with 3 10b. Genu I shorter (0.6 or less) than adjoining telofe- pairs of setae...... Scaptognathus mur or tibia. Slender rostrum with blunt, stylet- or 18a. P-2 with 2 setae, palps 4-segmented...... 19 arrow-shaped (barbed) tip. Basal pair of maxil- 18b. P-2 with 0 or 1 seta. Palps 2- to 4-segmented . 20 lary setae near base of rostrum or on gnathosomal 19a. Genua I and II as long as or longer than corre- base...... 12 sponding tibiae (and generally also longer than 11a. Basifemur IV with 0 setae. Female with 3 pairs telofemora). Length of genu I more than twice of perigenital setae; anterior pair of setae on its height. Telofemur with spiniform, genu and ti- minute platelets or within striated integument. bia I with spiniform or bristle-like smooth setae...... Anomalohalacarus ...... Halacarus 11a. Basifemur IV with 1 long and delicately plumose 19b. Genua I and II shorter than (less than 0.8) tibiae. seta. Female with 2 pairs of perigenital setae; an- Length of genu I less than 1.5 times its height. terior pair inserted on a plate. .... Arenihalacarus Telofemur, genu and tibia I with short, apically 12a. Rostrum parallel-sided and with blunt tip. PE with dentate or divaricate spines ...... Acanthopalpus longitudinal fissure...... Halacaroides 20a. Palps slender, 3-segmented, hardly extending be- 12b. Slender rostrum with stylet- or arrow-shaped (bar- yond rostrum. No seta on second palpal segment. bed) tip. PE of either side undivided...... 13 Apical segment with 1 seta in basal whorl. .... 21 13a. Rostrum stylet-shaped. Both pairs of maxillary se- 20b. Other combination of characters. Palps 3- or 4- tae on gnathosomal base, one pair in about midd- segmented. Second palpal segment with 1 dorsal le of gnathosomal base, one pair close to rostral seta. Apical palpal segment with 0–4 setae in ba- base...... Australacarus sal whorl...... 22 13b. Rostrum with arrow-shaped (barbed) tip. Gna- 21a. Tarsus I with 3 ventral setae. Tibia I with pair of thosomal base with one pair of maxillary setae. spines and pair of slender ventral setae. AE with ...... Parhalixodes epimeral vesicles...... Atelopsalis 14a. All tarsi ending with 3 almost equal-sized claws; 21b. Tarsus I with more than 3 ventral setae. Ventral median claw about as large as paired claws, cres- setae on leg I setiform. AE without epimeral ves- cent-shaped and smooth. Paired claws with row icles or epimeral pores...... Coloboceras of small, or few large, denticles along dorsal mar- 22a. Ocular plate divided into anterior and posterior gin...... Metarhombognathus plate...... 23 14b. Median claw of tarsi II to IV shorter than paired 22b. Ocular plate undivided or absent; may be fused claws, or absent. Paired claws smooth, with ac- with dorsal or epimeral plates...... 24 cessory process or with tines of pecten along ven- 23a. Rostrum almost as long as palps, stylet-shaped. tral flank...... 15 Tarsus I with 3 ventral setae (pas excluded). Ante- 15a. Apical fourth of rostrum with two pairs of barbs rior ocular plate with small gland pore; posterior extending beyond lateral margin of rostrum. Legs plate with small pore canaliculus but no gland pore. with cerotegumental lamellae...... Halixodes ...... Colobocerasides 15b. Apex of rostrum with rostral setae; barbs, if pre- 23b. Rostrum shorter than palps, triangular. Tarsus sent, minute and not extending beyond lateral I with more than 8 ventral setae (pas excluded). margin. Legs with or without cerotegumental la- Anterior and posterior ocular plate each with large mellae...... 16 gland pore...... Bathyhalacarus (in part) 16a. Palps inserted dorsally (major part of P-1 obscu- 24a. Tarsus I with 5 or more dorsal setae (solenidi- red in ventral aspect); distance between palps ge- on and famulus excluded) and 4 or more ven-

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tral setae (pas excluded). Solenidion setiform. less than half length of paired claws. Tarsi III and ...... Thalassarachna IV with 1–2 ventral setae...... Halacaropsis 24b. Tarsus I either with 4 dorsal setae plus small cla- 32b. Basifemur I with 2 setae. P-3 shorter than half vate solenidion but no ventral setae (pair of pas length of P-2. Median claws of tarsi II to IV min- present), or with 3 dorsal setae plus long setiform ute. Tarsi III and IV in general without ventral se- or short solenidion, number of ventral setae from tae...... Agauopsis none to numerous (pas excluded)...... 25 33a. Median claws of all tarsi nearly half length of 25a. No ventral seta on tarsus I (though pas present). paired claws. Opposing margins between pair of ...... 26 PE (at level of insertion of leg III) generally long 25b. Number of ventral setae on tarsus I from one to and straight. PE with 2 dorsal setae anterior to in- numerous...... 27 sertion of leg IV. Tarsi III and IV slightly curved. 26a. Tarsi I and II with small claviform solenidia. Tibia ...... Bradyagaue I with pair of setae, one of these setae pectinate. 33b. Median claws of tarsi I–IV less than one quarter OC with 0, rarely 1 seta. Ventral plates delicate, length of paired claws. Opposing margins of pair often separate. PE with 0–1 dorsal and 2 ventral of PE triangular or plates fused. PE with 0, rarely setae, the latter may be within striated integument. 1 dorsal seta anterior to insertion of leg IV. Tarsi Adanal setae lacking...... Isobactrus III and IV straight...... 34 26b. Tarsi I and II with short bacilliform solenidion. 34a. Apex of rostrum with single pair of minute Tibia I with pair of setae, both pectinate. OC with barbs. Legs without cerotegumental lamellae. 2 setae. Ventral plates often fused. PE generally ...... Werthelloides with 4 or more (rarely 3) setae. Adanal setae near 34b. Apex of rostrum with pairs of rostral setae, rarely anal cone...... Rhombognathus with minute barbs. If barbs present then legs with 27a. Idiosoma with more than 7 dorsal idiosomatic se- cerotegumental lamellae...... 35 tae (pair of adanal setae excluded). Tarsi I and II 35a. Ocular plates minute (less than 20 µm in length) with short ventral spine close to apex; solenidion or fused with PE...... Actacarus and famulus of tarsus I similar in length and shape. 35b. Ocular plates larger than 25 µm in length; may be ...... Rhombognathides fused with AD or PD...... 36 27b. Idiosoma with 5 or fewer dorsal setae (pair of 36a. AE with pair of epimeral pores...... 37 adanal setae excluded). Solenidion and famulus 36b. AE without epimeral pores...... 42 of tarsus I dissimilar in shape. No short ventral 37a. Tibia I with 4 ventral setae...... Arhodeoporus spine close to apex of tarsus I or II...... 28 37b. Tibia I with 2 or 3 ventral setae...... 38 28a. AE with 5 or more pairs of setae...... 29 38a. Apical palpal segment with 3 setae in basal 28b. AE with 2–4 pairs of setae...... 30 whorl...... 39 29a. Telofemora I to IV with more than 25 setae, 38b. Apical palpal segment with 0–1 setae...... 40 majority of setae arranged in rows. Tarsi IV 39a. Tibiae I and II with 3 and 3 (rarely 2) ventral se- with numerous ventral setae and pair of pas. tae...... Copidognathus ...... Acanthohalacarus 39b. Tibiae I and II each with a pair of ventral setae. 29b. Telofemora I to IV with 10 or fewer setae...... Acarothrix Tarsi IV with 0–1 ventral setae; pas lacking. 40a. Gnathosoma about as long as wide, and ros- ...... Agauides trum shorter than wide. Two of the 3 ventral 30a. With no more than 2 pairs of dorsal idiosomatic setae of tibiae I and II distinctly bipectinate. setae. Adanal setae lacking ...... Phacacarus ...... Copidognathides 30b. With 4–5 pairs of dorsal idiosomatic setae plus 40b. Gnathosoma and rostrum longer than wide, ros- pair of adanal setae...... 31 trum triangular. Ventral setae of tibiae I and II 31a. Tibia I with 3–5 spines. Spines large and wide slender, smooth, rarely delicately pectinate. ... 41 throughout their length; the latter more than half 41a. Tarsus II with 1 ventral seta; solenidion in dor- height of that segment. Blunt tip of spines serrate somedial position. Female genital sclerites with or coarsely denticulate. Spines not paired...... 32 3 subgenital setae. Perigenital setae in males scat- 31b. Tibia I with 2–8 ventral setae or spines, often tered around GO...... Pelacarus arranged in pairs. Setae slender or bipectinate; 41b. Solenidion on tarsus II in dorsolateral position; spines, if present, short, their length less than half ventral seta rarely present. No subgenital setae on height of tibia I...... 33 female genital sclerites. Perigenital setae in males 32a. Basifemur I with 3 setae. P-3 about half length of arranged in a ring close to GO...... Werthella P-2. Median claws of tarsi II to IV distinct, though 42a. Tibia I with 2 ventral setae...... 43

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42b. Tibia I with 4 or more ventral setae...... 46 52b. Tibiae I and II with 4 and 3 ventral setae, tarsi 43a. P-4 with single seta in basal whorl. I and II with 2 and 0 ventral setae, respectively...... Mictognathus ...... Winlundia 43b. P-4 with 3 setae in basal whorl...... 44 44a. Tibia I club-shaped. Tarsus I with 2 ventral setae Description of marine halacarid genera plus pas...... Thalassopthirius 44b. Tibia I cylindrical. Tarsus I with 3 or more ventral Acanthohalacarus Bartsch, 2001 (Fig. 14) setae plus pas...... 45 Diagnosis. Idiosoma: Length 450–540 µm. Dorsum 45a. Tarsus I with ventromedial seta, pair of eupathidia with AD, PD, and pair of OC, 6 pairs of idiosomatic plus pas...... Halacarellus (in part) setae and four pairs of gland pores. Adanal setae on 45b. Tarsus I with ventromedial seta, numerous eupa- anal cone. AD and PD each with pair of gland pores, thidia plus pas...... Thalassacarus OC with 2 pores. Venter with AE, pair of PE, and GA. 46a. Females and males with external pairs of genital AE and PE with adjunct setae. Female GA with up to acetabula; acetabula of males posterior to genital 5 pairs of perigenital setae and 2 pairs of subgenital opening...... Caspihalacarus setae. Male GA with numerous perigenital setae and 5 46b. Genital acetabula internal...... 47 pairs of subgenital setae. 47a. Both pairs of maxillary setae situated adjacent Gnathosoma: With 1 pair of maxillary setae to base of rostrum. Dorsal plates and margins of on gnathosomal base, 1 pair on rostrum. Palps 4- idiosoma often with cerotegumental lamellae or segmented, attached laterally. P-2 with 1 distodorsal spiniform filaments...... Agaue seta; P-3 with medial spur; P-4 with 3 setae in basal 47b. Distal pair of maxillary setae in apical half of ros- whorl. trum, basal pair near base of rostrum. No cerote- Legs: Genua of legs much shorter than adjoining gumental lamellae present...... 48 segments. Basifemora I–IV with 3–7 setae each. Tibiae 48a. Tarsus I with 1 basal seta or spur (rarely spur dou- and telofemora with ventromedial and ventrolateral, bled) separated from 2 or more apical eupathidia. dorsomedial and dorsolateral rows of short spiniform ...... 49 setae, more than 5 setae in each row. Tarsus I with 1 48b. Other arrangement of setae...... 51 ventromedial seta and numerous eupathidia; tarsi II to 49a. Ocular plate more than 3 times as long as wide; its IV with 5–6 ventral setae. Solenidia short, setiform, on posterior portion slender, tail-like. No gland pore tarsi I and II in dorsolateral and dorsomedial position, in posterior third of OC...... Tropihalacarus respectively. Famulus inconspicuous. Tarsi I to IV with 49b. OC 1–2.5 times as long as wide; its posterior por- 3 long dorsal setae each (solenidia excluded). tion not conspicuously slender. If OC elongate Apex of tarsi with pair of claws; central sclerite then a gland pore present in its posterior corner. ending with small claw-like process...... 50 Biology and distribution. With larva and 2 nymphal 50a. OC elongate, length at least twice width, with stages during ontogenetic development. The genus is gland pores in anterior and posterior half; plate recorded from a seamount (Great Meteor Seamount) sometimes divided. PE with (1–)3–6 dorsal (dor- in the northeastern Atlantic. Because of the numerous somarginal) setae. PD in general uniformly reticu- spiniform setae on the legs, Acanthohalacarus is late, without gland pores...... Bathyhalacarus (in expected to live in a close association with other part) organisms. 50b. OC mostly less elongate, with 1 or 2 gland pores. Remarks. Acanthohalacarus is characterized by its PE in general with 1 dorsal (dorsomarginal) seta. numerous spiniform setae on the legs and idiosoma. If OC long and provided with a gland pore ante- References. Bartsch (2001a). riorly and posteriorly, then PD with pair of costae Acanthopalpus Makarova, 1978 (Fig. 15) and gland pores...... Halacarellus (in part) 51a. P-3 with readily recognizable seta or spur. Tar- Diagnosis. Idiosoma: Length 440–550 µm. Dorsal sus I with 1–2 pairs of eupathidia and pair of pas. plates AD, OC and PD large; PD and anal plate fused. Dorsum with 6 pairs of idiosomatic setae; adanal setae ...... Peregrinacarus on anal plate. First pair of gland pores on AD, follow- 51b. P-3 without seta or spur. Tarsus I with 1 seta and ing gland pores vestigial. OC with pore canaliculus. 0–1 single eupathidia and pair of pas...... 52 Venter with AE, PE and GA. AE with 3 pairs of setae; 52a. Tibiae I and II with 4 and 2 ventral setae, respec- epimeral pores lacking. PE with 1 dorsal and 3 ventral tively. Tarsi I and II with a single ventral seta. setae. Female GA with 3 pairs of perigenital setae, ...... Camactognathus genital sclerites with 2 pairs of subgenital setae.

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Gnathosoma: Short. Rostrum shorter than 2 with 2 dorsal setae in distal half; these setae generally gnathosomal base, triangular in ventral aspect. Both bristle-like and pectinate. P-3 with short dorsal bristle. pairs of maxillary setae on rostrum. Palps 4-segmented, P-4 with 3 setae basally, 1 setula and 2 spinelets attached laterally, extending beyond rostrum. P-3 and apically. P-4 short. P-2 with 2 setae; P-3 with medial spine; P-4 Legs: Leg I much longer and stronger than following with 3 setae in basal whorl, 1 of these setae spiniform. legs. Genua I to IV shorter than adjoining leg segments. Legs: Leg I wider than following legs. Genua of all Basifemora I to IV with 2,2,1,0 setae. Telofemur I with legs shorter than telofemora and tibiae. Basifemora I– short, distinctly pectinate ventral spine. Genu I with 2 IV with 2 setae each. Telofemur I with short, spinose, long, heavily pectinate spines. Tibia I wide, with 5–6 divaricate spine; genua I with pair of spines, tibia I such spines. Tibiae II, III and IV ventrally with a pair with ventral spines and a seta. Tibiae II–IV with 3,2,2 of short setae. Tarsus I slender, at least 6 times longer ventral and 4,3,3 dorsal setae. Ventral spiniform setae than high. Tarsus I dorsally with 3 setae, ventrally with of telofemora, genua and tibiae often divaricate. Tarsi 1 long bristle and 2 small setae; tip of tarsus with setula I to IV with 4,4,3,3 dorsal setae and 3,1,0,0 ventral and flagelliform seta. Tarsus II with 3 dorsal setae, setae; each tarsus with pair of parambulacral setae. 1 tiny dorsomedial solenidion and (0?–)1–2 small Tarsus I with setiform solenidion and lamellar famulus ventral setae. Tarsi III and IV with 4 and 3 dorsal setae, in dorsolateral position. Solenidion on tarsus II in respectively, and 0 ventral setae. Tarsi II to IV each dorsomedial position. with paired parambulacral setae. Paired claws of tarsus I short, slightly longer than Tarsus I with small median claw; paired claws enlarged median claw. Paired claws of tarsi II to IV absent. Tarsi II to IV with ‘normal-sized’ paired claws; slender, elongate; central sclerite without a claw-like median claw either small or almost as long as paired process. Posterior tarsi with carpite between tip of claws. tarsus and central sclerite. Biology and distribution. One larval and two Biology and distribution. With three juvenile nymphal stages during ontogenetic development. stages, larva, protonymph and deutonymph. Males at Acarochelopodia is exclusively psammobiont, present not known. Two species, A. hirsutus Makarova, inhabiting tidal beaches. Nine species are described. 1978 and A. spinosus (Bartsch, 1978), are described, Records are from the Atlantic Ocean, Mediterranean the former is from the northern Pacific, the latter from and Black Sea, the Indian and Pacific Ocean. the northern Atlantic. The differences between these Remarks. Acarochelopodia is identified on the basis species are slight and A. hirsutus may be a junior syn- of the enlarged leg I with the very slender tarsus ending onym. with a single small claw. Remarks. Similar to species of the Agauopsis References. Angelier (1954), Bartsch (1977, 1988c), furcata group and Halacarellus species such as H. Morselli et al. (1998). subterraneus, but in contrast to these the P-2 of Acanthopalpus bears two setae. The presently known Acaromantis Trouessart & Neumann, 1893 (Fig. 17) Acanthopalpus species are easily separated from other Diagnosis. Idiosoma: Length 230–400 µm. AD and PD halacarid species on the basis of the divaricate and large, often foveate; OC reduced to minute sclerites. denticulate spine on telofemur I. AD generally with pairs of ds-1 and ds-3; ds-2 within References. Makarova (1978), Bartsch (1978). striated integument; ds-4 and ds-5 on PD; adanal setae usually in dorsal position. Ventral plates large. AE with Acarochelopodia Angelier 1954 (Fig. 16) a pair of epimeral vesicles and 3 pairs of setae. Epimera Diagnosis. Idiosoma: Length 140–270 µm. AD, OC III and IV of either side contiguous or fused, forming and PD separated by striated integument; plates delicate, the PE; that latter plate with 1 dorsal and 3 ventral setae. uniformly and finely porose. Dorsum with 6 pairs of Female GA with 4 pairs of perigenital setae; subgenital idiosomatic setae; ds-2, ds-3 and ds-4 within striated setae lacking. Male GA with 15–20 perigenital setae integument. AE divided into a right and left half, in arranged in a ring around GO and 0–3 pairs of outlying some species prolonged posteriorly. Each of PE may setae; genital sclerites with 3 pairs of minute subgenital be divided by longitudinal fissure. AE with 2 ventral setae. Male perigenital setae often plumose. setae; PE with 1 dorsal and 2 ventral setae. Female GA Gnathosoma: Globular, broadly attached to with 3 pairs of perigenital setae and 0 subgenital setae. idiosoma. Rostrum small, conical, much shorter than Male GA with ca 7 pairs of perigenital setae and 3 pairs gnathosomal base. One pair of long maxillary setae on of subgenital setae. gnathosomal base, 1 pair of short setae near apex of Gnathosoma: Longer than wide. Rostrum triangular rostrum. Palps attached to gnathosomal base dorsally. in ventral aspect. Both pairs of maxillary setae on Palps short, 2-segmented; second palpal segment with rostrum. Palps 4-segmented, lateral to gnathosoma. P-

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1 ventral bristle and 1 dorsal seta; palpal tip with tiny with 1 dorsal seta and 3 ventral setae. Female GA with 3 setae. pairs of perigenital setae and 1 pair of subgenital setae. Legs: Telofemora and tibiae much longer than small Male GA with numerous perigenital setae, its genital and globular genua. Basifemora I to IV with 1–2,2,1,1 sclerites with 4 pairs of subgenital setae and 1 pair of setae. Telofemora with ventrolateral and -medial external genital acetabula. carinae. Shape of leg I different from that of following Gnathosoma: Four-segmented palps attached legs. Tibia I long, its base narrow, cylindrical, then laterally. Rostrum triangular. Gnathosomal base and rapidly expanded; tibia I ending with wide, smooth rostrum each with a pair of maxillary setae. Rostral tip spine. Tarsus I hardly longer than high and rotated with 2 pairs of rostral setae. P-2 with 1 dorsal seta. No inward. Genu I with bipectinate seta. Tibia I with seta on P-3. P-4 with 3 setae in basal whorl. spine, a medial seta and 3 dorsal setae; tibiae II, III Legs: Genua shorter than telofemora and tibiae. and IV each with 2 bipectinate ventral spines and 3 Basifemora I–IV with 2,3,2,2 setae. Tibiae I to IV with dorsal setae. Tarsus I with dorsolateral solenidion and 3–4,3–4,3,3 dorsal setae and 2,2,2,2 ventral setae of famulus. Solenidion on tarsus II on inner flank of medial which the ventromedial one is bipectinate on tibiae I membrane of claw fossa. Tarsi I to IV with 4,4,3,3 to III (and IV). Solenidion on both tarsus I and II in dorsal setae (solenidia included, famulus excluded), dorsolateral position. Tarsi I–IV with 2–3,0,0,0 ventral 1,1,1,1–2 ventral setae, and each tarsus with pair of and 4,4,4,3 dorsal setae. single parambulacral setae. All tarsi end with a pair of claws. Central sclerite Tarsus I with median claw; paired claws lacking. with small, bidentate median claw. Tarsi II to IV with large paired claws; central sclerite Biology and distribution. With larva and small, claw-like process, if present, small. protonymph. Deutonymphal stage not known. At Biology and distribution. One larval and two present four species are described. Records are from nymphal stages are known. Eleven species are presently warm-temperate and tropical brackish water areas of described; all are psammobionts. With the strongly Australia, Asia, Africa and North America. sclerotized plates, the gnathosoma broadly attached to Remarks. Unique in Acarothrix is the presence of the idiosoma, and legs which can be clasped against the a pair of acetabula in the posterior portion of the male idiosoma, these creatures are protected against lesion genital sclerites. from grinding sediment particles. When walking, leg Acarothrix resembles Copidognathus and Werthella I is often raised, the tibiae are held horizontally above but bears three setae on basifemur II instead of the most the gnathosoma, the claw of tarsus I is turned inward. general number of two. In contrast to Copidognathus, Records of Acaromantis are from the western and the tibiae I and II of Acarothrix have two instead of eastern North Atlantic Ocean and the Mediterranean three ventral setae; and in contrast to Werthella, the Sea, and from the western and eastern Pacific Ocean. fourth palpal segment of Acarothrix bears three setae, The records are from tidal and shallow subtidal that of Werthella just one seta. habitats. References. Bartsch (1990a, 1997b, 2004b), Proches Remarks. Acaromantis is related to Simognathus. (2002). In contrast to Simognathus the palps of Acaromantis Actacarus Schulz, 1937 (Fig. 19) are two-segmented and tarsus I bears a single claw. In Diagnosis. Idiosoma: Length 140–360 µm. AD and general (but not always), the two genera can be sepa- PD large, opposing margins often truncate with few rated on the basis of the shape of leg I. In Acaromantis striae of membraneous integument; rarely plates widely tibia I is widest in its basal third and tarsus I is very short separated or fused. OC minute, sometimes fused with and rotated, whereas in the majority of Simognathus PE or lacking. Dorsal plates finely porose or foveate, species tibia I is club-shaped (widest in its apical third) never coarsely sculptured. Dorsum with 4 pairs of and tarsus I distinctly longer than high and ending with gland pores, 1 each on AD and OC and 2 on PD, and a large median and two slender lateral claws. 6 pairs of idiosomatic setae; adanal setae adjacent to References. Bartsch (1977), Otto (2000a). anal sclerites. AE with 3–4 pairs of setae; PE with 1 Acarothrix Bartsch, 1990 (Fig. 18) dorsal and 2–3 ventral setae. Membraneous integument Diagnosis. Idiosoma: Length 280–320 µm. AD, OC between AE and GA with 0–1 setae. Female with 3(–5) and PD present. OC with 1–2 setae. Dorsum with (3–)4 pairs of perigenital setae, though posterior pair may be pairs of gland pores, posteriormost pair situated on minute and concealed by protruding genital sclerites; cones, and 5–6 pairs of idiosomatic setae; third pair of subgenital setae lacking. Male with 7–18 pairs of setae on OC; adanal setae on anal plate in either dorsal perigenital setae and 1–3 pairs of subgenital setae. or ventral position. AE with pair of epimeral pores. PE Gnathosoma: Generally longer than wide. Rostrum triangular or elongate. Tectum truncate or with a

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 17 triangular process. Both pairs of maxillary setae inserted shorter than basal pair, sometimes that pair of setae on rostrum. Palps 4-segmented, attached laterally and hardly recognizable. Rostral setae minute, often spur- extending beyond rostrum. P-2 with 1 distal seta. P-3 like or divaricate. Slender 4-segmented palps lateral to short, with medial spur. P-4 with 3–4 basal setae and gnathosoma, reaching to or surpassing tip of rostrum. 1 spur. P-2 with 1 distodorsal seta. P-3 short, usually with 1 Legs: First two pairs not markedly dissimilar in distodorsal bristle (absent in some few species). Seta outline. No lamellae present. Genua shorter than on P-2 smooth or flattened and bipectinate. P-4 with adjoining leg segments. Basifemora I to IV with 2,2,1– 3 long setae in basal whorl (rarely situated in apical 2,1–2 setae. Tibia I with 2–4 ventral bristle-like setae, half of segment), 1 seta in about middle of segment, tibiae II, III and IV each with 2 ventral setae. Tarsus I and 1 setula and 2 spurs apically. Chelicerae slender, with large lateral membrane of claw fossa; setation: 3 cheliceral claw with few but strong teeth. dorsal setae, dorsal solenidion, 3 ventral setae. Tarsus II Legs: Generally slender; often with cerotegumental with 3 dorsal setae, 1 large dorsal solenidion, no ventral lamellae; lamellae of telofemora may even exceed the setae. Tarsi III and IV with 3–4 dorsal but no ventral segments height. Genua much shorter than telofemora setae. All tarsi with pair of parambulacral setae. and tibiae. Basifemora I–IV with 2(–3),2–3,2,2 setae. Paired claws of tarsus I smaller than those of Tibiae cylindrical or clavate, with 4–6 slender, usually following tarsi. Median claw small on all tarsi. smooth and bristle-like ventral setae. The majority of Biology and distribution. With one larval and the species with large membranes of claw fossae on all tarsi. two nymphal stages protonymph and deutonymph. Act- Tarsus I with 3 dorsal setae, dorsolateral solenidion, acarus is psammobiont, inhabiting coarse or fine sand, 1 long ventral seta, and a cluster of 10–30 ventral common in tidal areas. The deepest record is from eupathidia at tip of tarsus. Tarsus II with 3 dorsal setae, 400 m depth. Actacarus is distributed world-wide, 25 dorsomedial solenidion, and 0–4 ventral eupathidia. species are described. Tarsi III and IV with 3 dorsal but no ventral setae. Remarks. Actacarus is characterized by the Paired claws large, smooth, with single or numerous small OC, less than 20 µm in length, and can thus tines. Median claw minute. be distinguished from similar shaped psammobiont Biology and distribution. One larval and two species of the genera Arhodeoporus, Camactognathus, nymphal stages are known. More than 40 species are Copidognathus, and Winlundia. described. Most species are recorded from the southern References. Bartsch (1996a), Abé (1997), Otto hemisphere, from both tropical, temperate and polar (2000c). waters. Representatives of this genus live in a depth range from the intertidal to the abyss. Agaue Lohmann, 1889 (Fig. 20) Remarks. Species of the genera Bradyagaue, Hal- Diagnosis. Idiosoma: Length 320–1600 µm. Idiosoma acarellus and Thalassacarus may be mistaken for usually with cerotegumental layers, these may be Agaue. Agaue species never have curved tarsi and an delicate membranes, covering plates and striated enlarged median claw as present in Bradyagaue. The integument, or raised and structured like walls of a P-3 of Halacarellus species have a spiniform seta in honeycomb; other species have hair-like or spur-like medial position, and the posterior pair of maxillary filaments (cerotegumental structures may be lost during setae is in general situated in the posterior two-third the clearing procedure). Dorsal and ventral plates of the rostrum. In most of the northern hemisphere Hal- large. Dorsum with 3 pairs of gland pores, situated on acarellus species, the tip of tarsus I has no more than or lateral to AD, on OC and PD. Pairs of ds-1 to ds-5 two eupathidia beside the pair of parambulacral setae, in some species small in others long and erect; adanal whereas in Agaue species there are numerous setae. setae on anal plate. AE with 3 pairs of ventral setae. Thalassacarus bears numerous eupathidia on tarsus I PE with 1–3 dorsal setae anterior to leg III, 0–1 setae but, in contrast to Agaue, the dorsal and ventral plates anterior to leg IV, and 3 ventral setae. Female GA with are ornamented with foveae and rosette pores. 3–10 (rarely more) pairs of perigenital setae and 0–2 References. Newell (1984), Bartsch (1990b, 1999d), pairs of subgenital setae. Male GA with more than 80 Otto (1999b). perigenital setae densely arranged around GO; genital sclerites with 5 pairs of spur-like subgenital setae. Agauides Bartsch, 1988 (Fig. 21) Gnathosoma: Longer than wide, generally slender. Diagnosis. Idiosoma: Length 620–770 µm. Dorsal Tectum with scaliform lamella. Rostrum almost and ventral plates separated by wide areas of intensely parallel-sided, rarely as long, often much longer than striated integument. OC greatly reduced, wider than long, gnathosomal base. Maxillary setae inserted close corneae lacking. Dorsum with 6 pairs of idiosomatic together, 1 pair on gnathosomal base, 1 pair in basal setae; adanal setae in dorsal position. PD with pair of portion of rostrum. Distal pair of maxillary setae often gland pores. Ventral setae of AE often multiplied, plate

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 18 with 5–8 pairs of setae. PE with 1 dorsal and 2(–3) short, with median bristle- or spiniform seta, in some ventral setae. Female GA with 4–7 pairs of perigenital few species with denticulate divaricate spine. P-4 with setae; genital sclerites lack subgenital setae. 1–3 setae in basal half, rarely these setae in distal half; Gnathosoma: Rostrum triangular, about as long apically with setula and 2 spurs. as gnathosomal base. Maxillary setae short, inserted Legs: Genua distinctly shorter than adjoining adjacent on gnathosomal base and rostrum. Apical segments. Leg I much wider and longer than following rostral setae minute. Palps 4-segmented, lateral to legs and armed with conspicuous spines, viz. (0–)1–5 gnathosoma and extending to tip of rostrum. P-2 with spines on telofemur, 2 spinelets (may be bristle-like) on 1 distal seta. No seta on P-3. P-4 with 2 long setae, genu, 3–5 spines on tibia, and 1 spine on tarsus. Spines apically with setula and 2 spurs. generally blunt and delicately pectinate, in a few Legs: Genua much shorter than tibiae and telofemora. species spines conspicuously denticulate. Basifemora Basifemora I–IV with 3,3–4,2–3,2 setae. Tibiae I–IV I–IV with 2,2(–3),(1–)2,(1–)2 setae. Tibiae II–IV with with 7,6,3–6,5–6 ventral setae which are short, bristle- 2–3 ventral spines or bristles. In the majority of species, like, sometimes slightly pectinate. Tarsus I and II with tarsus I with 3 dorsal setae, dorsolateral solenidion, 1 dorsolateral and dorsomedial solenidion, respectively. ventromedial spine, and 2 (rarely 1) minute ventral Tarsi I–IV with 4,4,3,3 dorsal setae and 5–8,1,0,0–1 setae; apically with pair of parambulacral setae. ventral setae; tarsus I with pair of parambulacral setae; Tarsus II with 3 dorsal setae, dorsomedial solenidion, tarsus II with lateral but no medial parambulacral seta. 0–1 minute ventral setae, 1–2 lateral and 0–2 medial Tarsi III and IV lack parambulacral setae. parambulacral setae. Tarsus III and IV with 3–4 and 3 Claws of all tarsi similar-shaped; paired claws large, dorsal setae, respectively, and 0 (rarely 2) ventral setae; median claw small. apically with 0–1 parambulacral setae on either side. Biology and distribution. Agauides may be a Paired claws of posterior legs generally larger than temporary parasite. Two species are recorded, one from those of tarsus I, median claw small, often hardly the Atlantic, one from the Pacific Ocean, from bathyal developed. and abyssal depths. Biology and distribution. One larval and two Remarks. In contrast to the majority of halacarids, nymphal stages present. At present, 80 species are tarsi III and IV lack parambulacral setae. Unusual is the described. The genus is cosmopolitan, inhabiting the increased number of setae on the AE. range from tidal to the abyss. Most records are from References. Bartsch (1988b, 1989). warm and temperate waters. The number of species known from the southern hemisphere exceeds that Agauopsis Viets, 1927 (Fig. 22) from the north. Diagnosis. Idiosoma: Length 260–710 µm. Idiosoma Remarks. In contrast to species of Atelopsalis, usually wide, flattened and heavily armed. In the which also have enlarged leg I equipped with majority of species AD and PD with slightly raised spines, the palps of Agauopsis are four-segmented. longitudinal costae; costae with canaliculi or rosette Enlarged leg I with conspicuous spines are present pores. Gland pores small; AD, OC and PD with 1, 1 and in Acanthohalacarus and a few species of the genus 1–2 pairs of pores, respectively. Dorsum with 5–6 pairs Halacarellus (e.g. species of the subterraneus group of idiosomatic setae; adanal setae close to anal cone. and H. auzendei). These Halacarellus species have a AE large; generally extending dorsad, fused to anterior triangular rostrum, and their females often no more dorsal plate and thus forming the anterior margin of than two pairs of perigenital setae. The second palpal idiosoma. AE with 3 pairs of ventral setae and in the segment of Acanthohalacarus bears two setae. majority of species with a pair of epimeral pores (often References. Bartsch (1986b, 1996b), Otto (1999a). opening with a slit). PE with 1 dorsal and (1–)3 ventral setae. Female GA with (2–)3 pairs of perigenital setae; Anomalohalacarus Newell, 1949 (Fig. 23) genital sclerites with 0–4 subgenital setae. Male GA Diagnosis. Idiosoma: Length 200–520 µm. with approximately 30–100 perigenital setae, and often Idiosoma very slender; its width less than interval a pair of outlying perigenital setae; genital sclerites between epimera II and III. Dorsal and ventral plates with 3–5 subgenital setae. small, delicate, they lack conspicuous ornamentation. Gnathosoma: Longer than wide. Gnathosomal base OC absent or reduced to minute sclerites; corneae subquadrangular; rostrum almost parallel-sided, from lacking. PD present; in adults of most species divided slightly shorter to longer than gnathosomal base. First longitudinally. One pair of gland pores on AD, 0–1 pair of maxillary setae near base of rostrum, either on pairs of pores in striated integument, and 1–2 pairs gnathosomal base or on rostrum; 2nd pair of maxillary on PD. Dorsum with 5–6 pairs of idiosomatic setae; setae in distal third of rostrum. Palps 4-segmented, ds-1, ds-2 and ds-4 generally remarkably long; small lateral to gnathosoma. P-2 with 1 distodorsal seta. P-3 adanal setae on anal cone. AE in the majority of

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 19 species divided longitudinally (rarely epimera fused in is not divided and genu I is distinctly shorter than the the median); each plate with 3 ventral setae and pair adjoining segments. of epimeral pores. PE small, with 1 dorsal and 2–3 References. Bartsch (1981b, 2003c), Abé (1996b). ventral setae. Female genital plate divided; with 2 pairs Arenihalacarus Abé, 1991 (Fig. 24) of perigenital setae on genital plates and 1 pair within striated integument, on a pair of small sclerites or on Diagnosis. Idiosoma: Length 380–500 µm. Idiosoma a single median sclerite; genital groove present. Male spindle-shaped; its width less than interval between GA large; 7–50 pairs of perigenital setae lateral to GO insertions of legs II and III. Dorsal and ventral plates and genital groove; genital sclerites with 3 pairs of small; OC vestigial; corneae lacking. Dorsum with 6 subgenital setae. pairs of idiosomatic setae, ds-1 to ds-4 slender and Gnathosoma: Longer than wide. Rostrum slender, long; ds-2 to ds-5 within striated integument. Short parallel-sided; from half as long to almost as long as adanal setae in posterior margin of PD. AE divided into palps. Both pairs of maxillary setae inserted on rostrum. right and left plate; each plate with epimeral pore and 3 Four-segmented palps slender, attached laterally and setae. PE with 1 dorsal and 3 ventral setae. Female GA surpassing rostrum. P-2 with 1–2 setae, either a single divided into 4 platelets; male with fused GA. Female basal seta or 1 basal and 1 distal seta. P-3 short, with with 2 pairs of perigenital setae; subgenital setae 1 spine. P-4 with 3 setae in basal whorl; apically with lacking. Male with about 25 perigenital setae, genital setula and 2 spurs. sclerites with 3 pairs of subgenital setae. Legs: All legs slender; anterior 2 pairs of legs widely Gnathosoma: Slender. Palps 4-segmented, attached separated from posterior ones. Leg I longer than leg II. laterally; surpassing rostrum. P-2 with 1 basal and 1 Genu of leg I only slightly shorter than telofemur and distal seta. P-3 with medial spur. P-4 with 3 setae in tibia; genua II–IV shorter than adjoining leg segments. basal whorl. Rostrum slender. Both pairs of maxillary Dorsal and lateral setae on legs remarkably long. setae situated on rostrum. Basifemora I to IV with (1–)2,(1–)2(–3),1–2,0 setae, Legs: Slender. Genu of leg I somewhat shorter than respectively. Tibia I ventrally with 0–2 short spurs, telofemur and tibia; genua of following legs distinctly 0–2 delicately pectinated setae and 3–5 smooth setae; shorter than adjacent leg segments. Lateral membrane tibiae II–IV with 2–3,2–3,2 ventral setae, 1–3 of these of claw fossa of tarsus I enlarged. Basifemora I to setae bipectinate. Tarsus I with enlarged lateral fossa IV with 2,2,2,1 setae, at least 1 seta of each segment membrane, 3 dorsal setae, and a solenidion adjacent to long and delicately plumose. Genua and tibiae with fossa membrane; ventrally with 1 spur, rarely 2 spurs, bipectinate ventral setae. Solenidion of tarsus I and II and a pair of small, eupathid setae. Tarsus II with 3 situated dorsolaterally. Tarsi I–IV with 3,0,0,0 ventral dorsal setae, claviform dorsolateral solenidion, and setae and 4,4,3,3 dorsal setae (solenidia included). Each 0–1 ventral setae. Tarsi III and IV each with 3 dorsal of tarsi I to IV with pair of parambulacral setae. and 0 ventral setae. All tarsi with an apical pair of Paired claws of tarsus I smaller than those of parambulacral setae. following legs. Median claw present but small. Paired claws on tarsus I somewhat smaller than those Biology and distribution. With three juvenile on following tarsi. All tarsi with small median claw. stages, one larva and two nymphs. At present a single Biology and distribution. A larval and a single species is described, which was extracted from coarse nymphal stage, the protonymph, occur during sandy deposits in northern Japan. development. Juveniles have a fused, quadrangular PD. Remarks. In its shape similar to Anomalohalacarus. Anomalohalacarus exclusively inhabits the interstitium Both genera are psammobionts. Most of the of sandy deposits. Most records are from intertidal and Anomalohalacarus species bear one seta on P-2, in subtidal sediments. Anomalohalacarus, with 19 species contrast, in the single Arenihalacarus species there are described, is recorded from the North Atlantic Ocean, two setae. The female Arenihalacarus bears the anterior Mediterranean, Black Sea, Indian, and Pacific Ocean. pair of the two pairs of perigenital setae on a platelet Remarks. The general shape of Anomalohalacarus, immediately anterior to the genital slit, whereas in Arenihalacarus and Halacaroides is almost identical. Anomalohalacarus there are three pairs of perigenital Arenihalacarus has five pairs of gland pores, the setae, the anterior pair is situated on tiny sclerite(s) females have two pairs of perigenital setae and a or within the striated integument. Arenihalacarus distinct genital plate anterior to the GO, basifemur has five pairs of gland pores, Anomalohalacarus four IV bears a seta, and two nymphal stages occur during (rarely two) pairs of pores; basifemur IV bears one development. In contrast to Anomalohalacarus, species seta whereas in Anomalohalacarus there is none. In of Halacaroides still have small OC, the female GA Anomalohalacarus a free-living deutonymphal stage is suppressed. References. Abé (1991).

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 20

Arhodeoporus Newell, 1947 (Fig. 25) has two setae and Arhodeoporus three ventral setae Diagnosis. Idiosoma: Length 200–420 µm. Dorsal (except one species with two setae). Similar shaped plates large, often reticulate and with porose areas; Copidognathus species differ from Arhodeoporus in OC often tail-like extended. Majority of species with 4 the position of the solenidion on tarsus II (in lateral pairs of gland pores; in some few species glands large, instead of medial position as in Arhodeoporus) and the opening on cones. Dorsum with 6 pairs of dorsal setae; suppression of a free-living deutonymph. adanal setae at anal cone. Ventral plates large, may References. Bartsch (1983, 1997c), Otto (2000g). be fused. AE with 3 pairs of ventral setae and pair of Atelopsalis Trouessart, 1896 (Fig. 26) epimeral pores, the latter in some few species enlarged. Diagnosis. Idiosoma: Length 180–220 µm. Dorsal and PE with 1–2 dorsal and 3 ventral setae. Female GA with ventral plates large, in the majority of species almost 3 pairs of perigenital setae and 1–2 pairs of subgenital adjoining; plates often ornamented, panelled, foveate, setae. Male GA with 15–40 perigenital setae and 4–5 and/or with cup-like pores. Gland pores present pairs of subgenital setae. though rather inconspicuous. Dorsum with 6 pairs of Gnathosoma: From slightly to distinctly longer idiosomatic setae; adanal setae on anal plate. AE with than wide. Rostrum triangular or slender and almost 3 pairs of ventral setae and a pair of large epimeral parallel-sided. One pair of maxillary setae either on vesicles. PE with 1 dorsal and 3 ventral setae. Female gnathosomal base or in basal part of rostrum, 1 pair GA with 3 pairs of perigenital setae and 1–2 pairs of on rostrum. Palps 4-segmented, attached laterally, subgenital setae. Males with 4–5 pairs of perigenital extending beyond tip of rostrum. P-2 with 1 distal seta. setae, their genital sclerites with 4 minute subgenital No seta on short P-3. P-4 with 3 (rarely 2?) setae in setae. Internal genital acetabula may be enlarged. basal whorl. Gnathosoma: Almost as long as wide; base globular. Legs: Slender. Genua much shorter than adjoining Rostrum shorter than gnathosomal base. One pair of segments. Basifemora I to IV with 2,2,1–2,1–2 setae. maxillary setae in basal third of rostrum, the other pair Tibia I with 2 pairs of bristle-like ventral setae, the minute, spur-like, situated near tip of rostrum. Palps ventromedial ones either smooth or bipectinate, the 3-segmented (P-2 and P-3 fused), slender, lateral to ventrolateral ones smooth. Tibia II with 3–4 ventral gnathosoma and hardly surpassing tip of rostrum. No setae, the 2 ventromedial ones bipectinate. Tibiae III seta on second segment (corresponding to P-2 + P-3); and IV with 2 ventral setae each. Tarsus I with 3 dorsal third segment (corresponding to P-4) with 1 basal seta, setae, 1 dorsolateral solenidion, and 3(–2) ventral setae. 1 apical setula and 2 apical spurs. Tarsus II with 3 dorsal setae, 0–1, rarely 2, ventral Legs: Leg I distinctly longer and wider than setae; solenidion in dorsomedial position, often long, following legs. All legs with their genua being smaller seta-like. Tarsi III and IV with 4(–3) and 3 dorsal setae, than telofemora and tibiae. Basifemora I to IV with respectively and 0–1 ventral setae. Tarsi I and II each 2,2–3,2,2 setae. Telofemur I large, often with cuticular with pair of parambulacral setae, tarsi III and IV either spiniform lamellae. Tibia I with pair of ventral spines with pair of parambulacral setae and 0 ventral setae or in middle and pair of ventral setae near distal end of with single parambulacral seta and 1 long ventral seta. that segment. Tibia II with 1 dorsomedial spinelet and Tarsi end with pair of claws and small median claw. 2 ventral setae (1 pectinate, 1 smooth). Tibiae III and IV Claws often with pectines. each with pair of ventral setae, 1 pectinate, 1 smooth. Biology and distribution. One larval and two Tarsus I with 3 dorsal setae, dorsolateral solenidion nymphal stages are known. Arhodeoporus lives in and famulus, and 3 ventral setae. Tarsus II with 3 a variety of substrata, in coarse sand and amongst dorsal setae, dorsomedial solenidion, and 1 often long colonial organisms; it is common in shallow waters ventral seta. Tarsi III and IV with 4 and 3 dorsal setae, though present also in the bathyal. The genus is spread respectively, but no ventral setae. All tarsi with pair of in temperate and tropical areas around the globe; there parambulacral setae. are no records from polar waters. At present 30 species Tarsi I to IV end with paired claws and small median are described; several of them can be assigned to claw. species groups. Biology and distribution. Two nymphal stages are Remarks. Arhodeoporus shares several characters present. Seven species are described. Atelopsalis is with Winlundia and Camactognathus, namely four recorded from all oceans, it inhabits tidal and subtidal ventral setae on tibia I, no seta on P-3, three basal sediments. setae on P-4. The three genera can be separated on the Remarks. The enlarged legs I of Atelopsalis basis of the number of setae on tarsus I. Tarsus I of resemble those of Agauopsis. Distinguishing characters Camactognathus has a single ventral seta, Winlundia are: the AE of Atelopsalis bears epimeral vesicles and

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 21 the gnathosoma slender, 3-segmented palps, in contrast, gland pores; OC with 2 pairs of distinct gland pores, in Agauopsis there is a pair of slit-like epimeral pores generally 1 in anterior and 1 in posterior portion of OC and the palps are 4-segmented. and situated on, sometimes tube-like, cones. No gland References. Bartsch (2002). pores on PD. Dorsum with 6 pairs of idiosomatic setae; adanal setae on anal plate. AE with 3 pairs of setae. Australacarus Bartsch, 1987 (Fig. 27) PE with 1–6 dorsal (marginal) and 2–3 ventral setae. Diagnosis. Idiosoma: Length 370–600 µm. Idiosoma Female GA with 2–4 pairs of perigenital setae and 1–3 slender; its width less than interval between insertions pairs of subgenital setae. Male GO surrounded by 50– of legs II and III. Dorsal and ventral plates small; 100 perigenital setae, genital sclerites with 5 pairs of membraneous integument between plates rather thick. subgenital setae. AD and PD each with pair of gland pores. OC divided Gnathosoma: Rostrum almost as long as or into small anterior and posterior platelet; anterior longer than gnathosomal base, its shape triangular to platelet with gland pore; corneae lacking. Dorsum parallel-sided. One pair of maxillary setae inserted with 6 pairs of short idiosomatic setae; adanal setae on gnathosomal base, 1 pair on rostrum. Palps 4- on anal plates. Venter with small platelets between segmented, attached laterally, extending beyond widely separated AE and PE. AE with 3 pairs of setae. rostrum. P-2 with 1 distal seta, P-3 with 1 median spine PE with 1 dorsal and 2 ventral setae. Female GA with (may be very minute), P-4 with 3 setae in basal whorl, 2–3 pairs of perigenital setae, no subgenital setae. Male 0–1 lateral setae in middle of segment, 1 setula and 2 GA with genital groove posterior to GO and numerous spurs apically. perigenital setae on either side of GO and genital Legs: All legs slender. Genua distinctly shorter than groove; each genital sclerite with 4 subgenital setae. adjoining segments. Basifemora I to IV with 2,3,2– Gnathosoma: Slender. Rostrum attenuate, needle- 4,3–4 setae. Tibia I with 2–4 pairs of ventral bristle- shaped. Palps 3–4-segmented (P-2 and P-3 may be like setae; tibiae II, III and IV with 3–8 ventral bristles. fused), slender, about as long as rostrum. P-2 with 1 Tarsus I with 3 dorsal setae, 1 setiform dorsolateral distal seta; none on P-3 (if palps are 4-segmented); solenidion, 1 ventral seta and a cluster with up to 30 apical segment with 2–3 setae in basal whorl. ventral eupathidia. Tarsus II with 3 dorsal setae, slender Pharyngeal plate large. Both pairs of maxillary setae dorsomedial solenidion, 0–10 ventral setae; tarsi III on gnathosomal base. and IV with 3 dorsal and 0–4 ventral setae. Each tarsus Legs: Genua I–IV shorter than telofemora or tibiae. with pair of parambulacral setae. Basifemora I to IV with 2,2,1,1 setae. Tibiae I–IV Claws large, smooth or with pectines with delicate with 3–4,2,2,2 ventral setae, 1–2 setae of tibia I may tines. Median claw small. be bipectinate. Dorsal setae of legs slender. Solenidia Biology and distribution. One larval and two slender, on tarsus I in dorsolateral position, on tarsus II nymphal stages are known. A dozen species are in dorsomedial. Tarsus I–IV with 4,4,4,3 dorsal setae described. Records are from the Atlantic and Pacific (solenidia included), 3,1,0,0 ventral setae and apical Ocean. Most of the records are from the deep-sea. pair of parambulacral setae; 1 or 2 of parambulacral Remarks. Bathyhalacarus resembles Thalassacarus setae may be moved from apical position basalward. and a few species of the genus Halacarellus. In contrast Paired claws large. Median claw present but smaller to species of the two latter genera the ocular plates of than the other claws. Bathyhalacarus are elongate, often divided and bear a Biology and distribution. Five species are presently gland pore in their anterior and posterior portions, the described, all are from the southern hemisphere. PE in general have three to six dorsal setae, and the PD Australacarus is believed to be a temporary parasite. lacks gland pores. The palps form a trough, enclosing the needle-like References. Sokolov and Yankovskaya (1968), rostrum and chelicerae. Newell (1967), Bartsch (1982, 1989). Remarks. Related to Colobocerasides but Bradyagaue Newell, 1971 (Fig. 29) Australacarus has the dorsal and ventral plates more reduced and the rostrum more attenuate. Diagnosis. Idiosoma: Length 460–1100 µm. Idiosoma References. Bartsch (1987, 1993b), Otto (2000d). elongate, length about twice the width. Insertion of leg III in about middle of length of idiosoma. Dorsal Bathyhalacarus Sokolov & Yankovskaya, 1968 (Fig. 28) and ventral plates large. Plates marginally (rarely also Diagnosis. Idiosoma: Length 400–700 µm. Dorsal dorsally) with cerotegumental layers. Dorsal plates not plates often reticulate. AD in several species with small conspicuously sculptured, integument evenly pierced frontal spine. OC elongate, in some species divided by very fine canaliculi. AD, OC and PD each with pair into anterior and posterior portion; corneae usually of gland pores. Dorsum with 6 pairs of idiosomatic lacking. PD may be reduced. AD with 1 pair of large setae; adanal setae on anal plate. AE with 3 pairs of

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 22 ventral setae. PE with (1–)2–3 dorsal setae anterior to Camactognathus Newell, 1984 (Fig. 30) leg III, 2 dorsal setae anterior to leg IV, and 3 ventral Diagnosis. Idiosoma: Length 220–400 µm. Dorsal and setae. In most species opposing margins of right and ventral plates developed. Dorsum with (5–)6 pairs of left PE straight and approaching in the median. Female idiosomatic setae; adanal setae in margin of anal plate. GA with 5–12 pairs of perigenital setae; no subgenital AE with 3 pairs of setae. PE with 1 dorsal seta and 3 setae. Male GA with more than 100 perigenital setae ventral setae. Female GA with 3–4 pairs of perigenital arranged in a dense ring around GO; each genital setae and 1 pair of subgenital setae. Male GA with 50– sclerite with 5 subgenital setae which are spur- or 100 perigenital setae and 2–3 pairs of subgenital setae. stump-like. Gnathosoma: Rostrum slender, as long as or longer Gnathosoma: Longer than wide. Rostrum parallel- than gnathosomal base. Basal pair of maxillary setae sided, slender, generally longer than gnathosomal near base of rostrum, apical pair near apex. Palps 4- base. One pair of maxillary setae on gnathosomal base, segmented, attached laterally and surpassing rostrum. 1 pair in basal part of rostrum; the 4 setae situated P-2 with 1 distal seta. No seta on P-3. P-4 with 3 setae close together. Four-segmented palps slender, slightly in basal whorl. surpassing rostrum. P-2 with 1 distal seta, P-3 with 0–1 Legs: Genua much shorter than tibiae and seta, P-4 with 3 basal setae, apically with 2 setulae and telofemora. Basifemora with 2,2,1–2,1–2 setae. Tibiae 2 spurs. I–IV with 4,2,2,2 ventral setae; ventromedial setae Legs: Slender. Genua shorter than adjoining often bipectinate. Solenidion on both tarsus I and segments. Telofemora, genua and tibiae often with II positioned dorsolaterally. Tarsi I–IV with 1,1,0,0 cerotegument. Basifemora with 2,2,2,2 setae. Tibia I ventral setae and 4,4,4,3 dorsal setae. with 2–3 pairs of bristle-like ventral setae; tibiae II–IV Paired claws large. Central sclerite with very small with 4–5,3–4,3–4 ventral setae. Ventral setae of tibiae claw-like process. short, never spiniform, never bipectinate. Tibiae and Biology and distribution. Both proto- and genua III and IV in general with setigerous processes. deutonymph are free-living stages. Three species are Tarsi III and IV slightly curved. Tarsus I with 3 dorsal recorded, viz. from the Southern American Pacific setae; short dorsolateral solenidion, 1 ventral seta, coast, the Mediterranean and the North Sea. The and apically with 4–12 pairs of eupathidia (pair of records are from sandy deposits. parambulacral setae included). Tarsus II with 3 dorsal Remarks. Resembling Arhodeoporus, setae, short dorsomedial solenidion, 0–1 ventral setae Copidognathus and Winlundia in the shape of idiosoma and pair of parambulacral setae. Tarsi III and IV each and absence of a seta on P-3, but tarsi I and II of with 3 dorsal and 0 ventral setae, apically with pair of Camactognathus each bear a ventral seta, whereas in parambulacral setae. the other three genera there are two or three setae on All tarsi with massive, bidentate median claw. Paired tarsus I and one or none on tarsus II. claws longer but generally more slender than median References. Newell (1984), Morselli and Mari claw. These paired claws usually with accessory (1982), Bartsch (1991). process and long pecten. Caspihalacarus Viets, 1928 (Fig. 31) Biology and distribution. One larval and the two nymphal stages proto- and deutonymph are present Diagnosis. Idiosoma: Length 450–530 µm. Dorsum during development. Bradyagaue is world-wide with AD, OC and PD, and 6 pairs of dorsal idiosomatic distributed, in polar as well as in warm-temperate setae. Setae ds-2 to ds-4 on minute sclerites within regions, in littoral waters as well as in depths of 1500 m. striated integument. AD and OC with pair of gland pores. Almost 20 species are described, twelve of them live in AE with 3 pairs of ventral setae; PE with 1 dorsal and the southern hemisphere. Bradyagaue supposedly live 2 ventral setae. Female GA with 2 pairs of perigenital on stolons of hydrozoans. One of the males examined setae; genital sclerites with 2 pairs of subgenital setae had a spermatophor attached to leg IV. and external genital acetabula. Male GA with almost Remarks. Bradyagaue can be distinguished from 100 perigenital setae and 5 pairs of subgenital setae; 2 Agaue with help of the tarsi; in Bradyagaue the posterior pairs of large external genital acetabula posterior to GO, tarsi are slightly curved, the median claw of all tarsi is 1 pair of small acetabula between genital sclerites. enlarged, the paired claws are slender, in contrast, the Gnathosoma: Rostrum triangular, about as long tarsi of Agaue are straight, the median claw is small or as gnathosomal base. Palps 4-segmented, lateral to inconspicuous. gnathosoma. Palps extending beyond rostrum. P-2 with 1 distodorsal seta. P-3 with medial spur. P-4 with 3 References. Newell (1971), Bartsch (1992c, basal setae and 1 mid-lateral seta. Apically with setula 2004a). and spurs.

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Legs: Leg I slightly larger than leg II. Basifemora Biology and distribution. One larval and two I–IV with 2,2,2,2 setae. Tibiae I–IV with 6(–7),4,2,2 nymphal stages are known. The three species described ventral setae. Tarsus I and II with dorsolateral and are recorded from the northeastern Atlantic and the dorsomedial solenidion, respectively. All tarsi with Mediterranean. 3 dorsal setae (solenidia excluded). Tarsus I with Remarks. Coloboceras has a short gnathosoma with spiniform ventromedial seta and 3–4 apical eupathidia three-segmented palps. Similar short palps are present (without parambulacral setae), tarsus II with 1–2 apical in Atelopsalis, but in that genus legs I bear prominent eupathidia; tarsi III and IV without ventral setae. Each spiniform processes. tarsus with pair of parambulacral setae. References. Monniot (1962), Bartsch (1973). Paired claws large, with pecten. Median claw very Colobocerasides Viets, 1950 (Fig. 33) small. Diagnosis. Idiosoma: Length 470–680 µm. Dorsal Biology and distribution. A free-living larval, proto- and ventral plates distinct. OC divided into anterior and deutonymphal stage present during ontogeny. The and posterior plate. Dorsum with 6 pairs of idiosomatic single species known was described on the basis of setae; adanal setae on anal plate. Venter with individuals from the Caspian Sea, collected at salinity supplementary sclerites. AE with 3 pairs of ventral of 12.5 ‰. The species proved to be abundant in setae. PE with 1 dorsal and 2 ventral setae. Female freshwater, in rivers emptying into the Caspian Sea and with 3 pairs of perigenital setae; genital sclerites lack Black Sea. Recently, the species was collected in the subgenital setae. river Rhine. Gnathosoma: Rostrum long, slender, pointed. Remarks. In dorsal aspect similar to Halacarellus, Chelicerae with slender serrate claw. One pair of in ventral aspect easily separated from that genus on maxillary setae inserted on gnathosomal base, 1 pair the basis of the large genital acetabula. on base of rostrum. P-2 and P-3 not distinctly separate. References. Viets (1928), Bartsch (1998b). Second palpal segment with 1 distodorsal seta; P-3 Coloboceras Trouessart, 1889 (Fig. 32) (if present) without seta; apical segment with 3 basal Diagnosis. Idiosoma: Length 300–500 µm. Dorsal setae. and ventral plates large; integument evenly and finely Legs: Genua shorter than telofemora and tibiae. porose, often slightly brown or green. Gland pores Basifemora I to IV with 2,2,1,1 setae. Tibiae with strong small. Dorsum with 6 pairs of small setae; adanal ventral bristles, from I to IV numbering 3–4,2–5,2–4,3. setae on anal cone. AE with 3 pairs of setae. PE with Tarsus I with 3 ventral and 3 dorsal setae and setiform 1 dorsal seta and 3 ventral setae. Female GA with 3 dorsolateral solenidion. Tarsus II with 1 ventral seta, 3 pairs of perigenital setae and 0 subgenital setae. Male dorsal setae and long dorsomedial solenidion. Tarsi III GO surrounded by approximately 50 perigenital setae; and IV without ventral but with 3 dorsal setae. Tarsi genital sclerites with 5 pairs of subgenital setae. I–IV each with a pair of parambulacral setae. Gnathosoma: Short, slightly longer than wide. Paired claws large, slender. Median claw distinct Rostrum conical or triangular. One pair of maxillary though smaller than paired claws. setae on gnathosomal base, 1 pair on rostrum. Palps 3- Biology and distribution. Two species are described, segmented, attached laterally, only slightly extending one from the northern, the other from the southern beyond rostrum. No seta on 2nd segment. Apical Atlantic Ocean, from a depth range of 450–1400 m. segment with 1 basal seta and setula and 2 spurs near Remarks. Colobocerasides is thought to be related its tip. Chelicerae elongate, stylet-like. to Australacarus. In the latter genus, the dorsal and Legs: Genua distinctly shorter than telofemora and ventral plates are greatly reduced. tibiae. Genua and tibiae with distal lamellae, tarsi with References. Bartsch (1998a). large fossa membranes. Basifemora I to IV with 2,2,1,1 Copidognathides Bartsch, 1976 (Fig. 34) setae. Tibiae I, II and III each with 4 bristle-like ventral Diagnosis. Idiosoma: Length 300–390 µm. Idiosoma setae, tibia IV with 3 wide ventral setae. Tarsus I with wide. Dorsal and ventral plates large, with porose 3 dorsal setae, long setiform solenidion on dorsolateral panels. Gland pores present but inconspicuous. Dorsum fossa membrane, 1 ventral seta, apical cluster of with 5–6 pairs of setae; adanal setae on anal plate. AE 7–8 eupathidia, and parambulacral setae. Tarsus II with 3 pairs of ventral setae and pair of small epimeral with 3 dorsal setae, solenidion on dorsomedial fossa pores. PE with 1 dorsal seta and 3 ventral setae. Female membrane, 2–3 ventral setae, and pair of parambulacral GA with 3 pairs of perigenital setae and 1 pair of setae. Tarsi III and IV each with 3(–4?) dorsal setae, 1 subgenital setae. Male GA with 12–15 perigenital setae ventral seta and pair of parambulacral setae. on either side of GO; genital sclerites with 4 pairs of Paired claws large, often with accessory process and subgenital setae. pecten. Median claw present, minute.

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Gnathosoma: Short, only slightly longer than wide. length of gnathosomal base) and triangular to long, Rostrum shorter than gnathosomal base. One pair of slender and parallel-sided (longer than gnathosomal maxillary setae inserted on gnathosomal base, 1 pair base). Tectum truncate, with median process or huge on rostrum. Palps 3–4-segmented, attached laterally; crest. Normally with 2 pairs of maxillary setae, 1 extending beyond tip of rostrum. P-2 with 1 distal seta, pair inserted on gnathosomal base, 1 pair on rostrum; P-3 (if present) with none. Apical segment with 0–1 a few species with 2–7 pairs of maxillary setae on basal setae; its tip ending with setula and 2 spurs. gnathosomal base. Palps 4-segmented, attached Legs: Short. Genua much shorter than adjoining laterally and at least slightly surpassing rostrum. P-2 segments. Basifemora with 2,2,1–2,1–2 setae. with 1 distal seta. No seta on P-3 (there may be a small Tibiae I and II with 3 ventral setae; the ventrolateral spiniform cuticular process which is no seta because seta slender and smooth, the 2 ventromedial setae an alveolus is lacking). P-4 with 3 setae in basal whorl; bipectinate. Tibiae III and IV ventrally each with 1 apically with setula and 2 spurs. bipectinate and 1 smooth seta. Tarsus I with 3 dorsal Legs: From short and wide to long and slender in setae, setiform dorsolateral solenidion, 1 ventral seta, shape; a few species with large lamellae. Genua shorter and pair of parambulacral setae. Tarsus II with 3 dorsal than telofemora and tibiae. Basifemora I to IV with setae, dorsolateral solenidion, no ventral seta, and pair 2,2,(1–)2,(1–)2 setae. Genua I–IV with 4(–3),4(–3),3,3– of parambulacral setae. Tarsi III and IV with 4 and 3 4(–5) setae. Tibia I with 3 ventral setae, often 1 of these dorsal setae, respectively, pair of parambulacral setae, setae bristle-like and smooth and 2 setae pectinate but no ventral seta. On tarsus III lateral parambulacral or spiniform. Tibia II with 3 ventral setae (1 species seta scaliform, medial one setiform. On tarsus IV both with 2 setae), in general 1 seta slender and smooth, 2 parambulacral setae scaliform. setae bipectinate. Tibia III with 2 ventral setae, often 1 Paired claws large, with accessory process. Median slender and smooth and 1 bipectinate. Tibia IV either claw present but small. with 1 smooth and 1 bipectinate or with 2 smooth setae. Biology and distribution. A larval and a single In general, tibiae I and II with 4 dorsal setae and tibiae nymphal stage, a protonymph, present. One species III and IV with 3 such setae. Tarsus I with 3 dorsal recorded from the eastern Atlantic Ocean, one from setae, a dorsolateral seti- or baculiform solenidion, a the Mediterranean and one from the Pacific coast lamellar, rarely digitiform famulus, 3 ventral setae, and of southern South America. The three species are a pair of parambulacral setae. Tarsus II with 3 dorsal inhabitants of the middle and upper shore. setae, setiform dorsolateral solenidion, no ventral Remarks. Copidognathides resembles seta but a pair of parambulacral setae. Tarsi III and Copidognathus and Werthella. Compared with IV with 3–4 dorsal setae, no ventral setae, and pair of Copidognathus, the number of setae of both P-4 and parambulacral setae (rarely 1 of parambulacral setae and tarsus I are reduced. In contrast to Werthella, the moved to a ventral position or lacking); parambulacral epimeral pores on the AE are small. setae setiform or short and spur-like. References. Bartsch (1976, 1999c). Paired claws large; median claw present, though small. Claws of leg I may be shorter than those of Copidognathus Trouessart, 1888 (Fig. 35) following tarsi. Claws smooth or with an accessory Diagnosis. Idiosoma: Length 180–700 µm. Dorsal process, with or without pecten. and ventral plates generally large (or even fused). Biology and distribution. The ontogeny includes Plates smooth or heavily ornamented, panelled and a larval and a single nymphal stage, the protonymph. with raised circular or subquadrangular areolae and More than 300 species are described. The genus is longitudinal costae; areolae and costae with rosette cosmopolitan; present from the upper shore to deep pores or uniform porosity. With 4 pairs of gland pores sea basins. Copidognathus is found in a wide range which may be small, almost inconspicuous, or large of substrata, in sand, gravel, coral debris, bushy algae, and opening on raised cones. Dorsum with 6 pairs of colonial organisms, and amongst gills and eggs of dorsal setae; adanal setae on anal plate. AE with 3 pairs decapods. A few species live in fresh water. of ventral setae and pair of epimeral pores (rarely with Remarks. Copidognathus resembles small internal vesicles); PE in general with 1 dorsal Copidognathides and Arhodeoporus. In and 3 ventral setae. Female GA with 3(–5) pairs of Copidognathides the number of setae of tarsus I and P-4 perigenital setae and 1 pair of subgenital setae. Male is reduced. Arhodeoporus differs from Copidognathus GA with 4–40 pairs of perigenital setae; genital sclerites in having four ventral setae on tibia I, the solenidion with 3–4 (rarely 2) pairs of subgenital setae. on tarsus II in dorsomedial position, and two nymphal Gnathosoma: Longer than wide, rarely about as stages during its development. long as wide. Shape of rostrum varying from short (half

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The setation of the legs of Copidognathus within an area where rostrum is passing over into demonstrates a great uniformity, normally trochanters gnathosomal base. Palps attached dorsally but separated I–IV have 1,1,1,0 setae, basifemora I–IV 2,2,2,2, from each other by distinctly more than width of basal telofemora 4–5,4–5,2–3,2–3, genua 4,4,3,3, and tibiae palpal segment. Length of palps less than 1/3rd of that 7,7,5,5 setae. Only few species have a larger or lower of rostrum. Palps 2-segmented; apically with 2 spurs. number of setae. Legs: Cylindrical, long. Genua shorter than adjoining References. Bartsch (1994c, 1998c, 1999b), Otto segments. Basifemora with 4–7 setae each. Telofemora (2000h). I–IV each with 6–9 bristle-like ventral setae and 8–10 dorsal setae; tibiae I–IV each with 8–10 bristle-like Corallihalacarus Otto, 1999 (Fig. 36) ventral setae and 7–10 dorsal setae. Tarsi with short Diagnosis. Idiosoma: Length 580 µm. Dorsal plates fossa membranes. Tarsus I with 3 dorsal setae, tiny AD, OC, PD contiguous. Dorsal parts of AE and PE dorsolateral solenidion, 1–2 minute ventral setae, 6 fused, ventral parts contiguous. Dorsum with 4 pairs eupathidia and pair of doubled parambulacral setae. of gland pores and 5 pairs of idiosomatic setae; adanal Tarsus II with 3 dorsal setae, bud-like dorsolateral setae on anal plate. AD with 2 pairs of setae and 1 pair solenidion, 1 minute ventral seta, 5 eupathidia and a of gland pores; OC with 2 gland pores. AE with 3 pairs pair of doubled parambulacral setae. Tarsi III and IV of setae, PE with 1 dorsal seta and 3 ventral setae. each with a pair of parambulacral setae, 3 dorsal but no Female GA with 2 pairs of perigenital setae, genital ventral setae. sclerites with 1 pair of subgenital setae. Tarsi end with pair of rather small claws. Median Gnathosoma: Long and slender, fused to idiosoma claw well developed. via flexible neck. Rostrum parallel-sided. Both pairs Biology and distribution. A single species is of maxillary setae on rostrum. Palps 4-segmented, described which has been found on and in the sea attached laterally. P-2 with apical seta. No seta on P-3. urchin Plesiodiadema indicum (Döderlein, 1900), taken P-4 with 1 seta in distal half and a setula plus 2 spurs at 430 m depth, at 7°N and 127°E. Enterohalacarus is at the tip. believed to be a parasite. Legs: Genua shorter than telofemora. Telofemora Remarks. Compared with other halacarids, III and IV with large lamellae. Basifemora I–IV with Enterohalacarus has a very large idiosoma but 2,2,2,2 setae. Genua I–IV with 4,4,3,3 setae. All extremely small palps. There is only one genus, tibiae ventrally with 2 bipectinate setae. Tarsi I–IV Spongihalacarus, in which the palps are more reduced with 4,4,4,3 dorsal setae, setiform solenidia included. than in Enterohalacarus. Solenidion on tarsus I in dorsolateral, on tarsus II in References. Viets (1938). dorsomedial position. Tarsus I with pair of eupathid Halacarellus Viets, 1927 (Fig. 38) ventral setae; tarsus II with single ventral seta; tarsi III and IV lack ventral setae. All tarsi with pair of Diagnosis. Idiosoma: Length 270–840 µm. Dorsal parambulacral setae. and ventral plates present; small platelets may be Paired claws slender. Median claw only slightly found within dorsal striated integument. PD of males shorter than paired claws. sometimes larger than that of females. Surface of Biology and distribution. The single species dorsal plates smooth, finely porose or reticulated; recorded is from sandy deposits off northeastern plates often with slightly raised costae. Conspicuous Australia. ornamentation not known. Ventral plates generally Remarks. Corallihalacarus resembles Mictognathus delicately and uniformly punctate. Dorsum with 3–5 but has, unique within the Halacaridae, a very long, pairs of gland pores and 6 pairs of idiosomatic setae; flexible neck. adanal setae on anal cone. AE with 3 pairs of setae, PE References. Otto (1999c). with 1(–3) dorsal and 2–3 ventral setae. Female GA with 2–4 (rarely 7) pairs of perigenital setae and 0–5 Enterohalacarus Viets, 1938 (Fig. 37) pairs of subgenital setae. Male GO surrounded by 20– Diagnosis. Idiosoma: Length 2000 µm. AD, OC and 100 perigenital setae; genital sclerites generally with 5 PD present, in ovigerous females widely separated pairs of subgenital setae, rarely with less setae. by striated integument. Dorsum with at least 4 pairs Gnathosoma: Longer than wide. Rostrum triangular of dorsal setae. AE with 3 pairs of ventral setae, PE or elongate and parallel-sided, its length may be less, with 2 ventral setae. Female with approximately 160 same or distinctly more than length of gnathosomal base. perigenital setae arranged around GO. Genital sclerites Apical pair of maxillary setae in distal half of rostrum, with 2 pairs of subgenital setae. basal pair of setae either on rostrum or on gnathosomal Gnathosoma: Longer than wide. Rostrum short, base close to rostrum. Palps 4-segmented, lateral to tapering. Two pairs of maxillary setae close together gnathosoma and extending beyond tip of rostrum. P-2

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 26 with 1 distodorsal seta, P-3 short, with 1 medial spine similar elongate plates have a PD with a pair of costae or spinelet. P-4 with 3 setae in basal whorl, 1 setula and and gland pores. 2 minute spurs at the tip, and often with 1 lateral seta References. Bartsch (1997a). in middle or posterior half of P-4. Cheliceral claw with Halacaroides Bartsch, 1981 (Fig. 39) serrate dorsal margin. Diagnosis. Idiosoma: Length 280–370 µm. Idiosoma Legs: Leg I often longer and wider than following slender, its width less than distance between insertions legs; in a few species provided with stout ventral spines. of legs II and III. Dorsal and ventral plates delicate. OC Genua shorter than adjoining segments. Basifemora reduced to platelets. PD smaller than AD. Gland pores I–IV with 2,2–4,2(–4),2(–4) setae, respectively. Tibiae inconspicuous. Dorsal idiosomatic setae short, 6 pairs I–IV with (2–)4–8,(2–)3–8,2–8,2–6 ventral setae present; adanal setae on anal plate. Anterior epimera which are slender or spiniform, smooth or delicately fused in the median, this AE with 3 pairs of ventral pectinate. Tarsus I with 3 dorsal setae, dorsolateral setae. PE small, with a longitudinal fissure, 1 dorsal solenidion, 1 (rarely 2) ventromedial seta (which is and 3 ventral setae. Female GA small, with 3 pairs of slender, spur-like or spiniform), 2–26 eupathidia, perigenital setae and 2 pairs of subgenital setae. Male and pair of doubled parambulacral setae. Tarsus II GA larger, with approximately 20 perigenital setae and with 3 dorsal setae, dorsomedial solenidion, 0–7 5 pairs of subgenital setae. ventral setae (often eupathidia), and pair of doubled Gnathosoma: Longer than wide. Rostrum slender, parambulacral setae. Tarsi III and IV with 3–4 and 3 parallel-sided, about as long as gnathosomal base. Both dorsal setae, respectively, 0–6 ventral setae, and pair of pairs of maxillary setae inserted on rostrum. P-2 with 1 parambulacral setae. distal seta, P-3 with 1 spur, P-4 with 3 basal setae. Claws large; on tarsus I sometimes slightly smaller Legs: Slender; leg I longer than leg II. Genua shorter than on posterior tarsi. Claws smooth or with pectines. than telofemora and tibiae. Basifemora I to IV with 2 Median claw present, small. setae each. Tibia I with 3–4 ventral setae; tibiae II, III Biology and distribution. One larval and two and IV with 3 ventral setae each. Tarsus I with enlarged nymphal stages are known. Almost 50 species are lateral fossa membrane, 3 dorsal setae, solenidion and described. The genus is cosmopolitan but species famulus adjacent to lateral membrane of claw fossa, 3 groups have a restricted distribution. Records are both ventral setae, and pair of doubled parambulacral setae. from shallow waters and deep-sea regions. On cold Tarsus II with 3 dorsal setae, dorsomedial solenidion, 1 water shores, the genus Halacarellus is one of the ventral seta, and pair of parambulacral setae. Tarsi III numerically important genera in the halacarid fauna. and IV each with a pair of parambulacral setae, 3 dorsal Records from tropical beaches are rare. Several species but no ventral setae. are adapted to brackish water, few to almost fresh Claws on tarsus I somewhat smaller than on water. Most species are carnivorous, some few may following tarsi. Median claw present though small. temporarily be algivorous. Biology and distribution. Two species are known, Remarks. For several years, Thalassarachna had taken on the shores of southern South America. The been used as a synonym for Halacarellus, but the genera genus is supposed to be arenicolous. are now regarded as separate. Thalassarachna has an Remarks. The shape of Halacaroides is similar increased number of dorsal setae on the tarsi (more to that of Anomalohalacarus and Arenihalacarus. than three setae on tarsi I and II), and most species have Distinguishing characters are: the dorsum of a pair of gland pores in the marginal membraneous Halacaroides bears distinct OC, the dorsal setae are integument, which is lacking in Halacarellus. short, the PE longitudinally divided, the female GA A few species of Halacarellus resemble Agaue; undivided, and genu I distinctly shorter than tibia I. differences are: P-3 in Halacarellus bears a medial References. Bartsch (1981b). spine or seta, in Agaue there is a dorsal seta. Other Halacarellus species are similar to Agauopsis, but Halacaropsis Bartsch, 1996 (Fig. 40) Agauopsis generally has a parallel-sided rostrum, the Diagnosis. Idiosoma: Length 555–760 µm. Dorsal and arrangement of the spines on its leg I is different, the ventral plates large. Dorsum with 6 pairs of idiosomatic number of setae on P-4 generally reduced. setae; ds-2, ds-3 and ds-4 generally enlarged; adanal Thalassacarus, which also demonstrates an overall setae small, on anal plate, often seen only in ventral resemblance with Halacarellus, bears 2 large basal aspect. AD and OC with pair of gland pores. AE with tines on its cheliceral claws. Such tines are lacking in 3 pairs of ventral setae. PE with 1 dorsal and 3 ventral Halacarellus. setae. Female GA with 5–6 pairs of perigenital setae Bathyhalacarus species have elongate ocular plates and 4–5 pairs of subgenital setae. Male GA with with large gland pores. Halacarellus species with approximately 50 perigenital setae around GO, 1 pair

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 27 outlying. Genital sclerites with 5–7 spur-like subgenital like ornamented cerotegument. AD often with frontal setae. process. OC and/or PD in several species lacking. PD Gnathosoma: Longer than wide. Rostrum slender, in males often larger than in females. The majority of parallel-sided. Rostrum about as long as gnathosomal species with 5 pairs of distinct gland pores, first pair base. One pair of maxillary setae on gnathosomal base arising from or close to AD, second pair marginally, near base of rostrum, 1 pair in apical portion of rostrum. within striated integument (rarely on PE). Dorsum with Palps 4-segmented, lateral to gnathosoma; extending (5–)6 pairs of idiosomatic setae; adanal setae adjacent beyond apex of rostrum. P-3 about half length of P- to posterior pair of gland pores. PE usually with 1 dorsal 2; P-4 about as long as P-3. P-2 and P-3 each with 1 seta, rarely with 2 setae, and 3 ventral setae. Female dorsal seta. P-4 basally with 3 long setae, apically with GA with 2–15 pairs of perigenital setae; in species with 1 setula and 2 elongate spinelets. Cheliceral claw with 2 pairs of perigenital setae on GA, a 3rd pair (rarely serrate dorsal edge. a 4th pair) present within striated integument anterior Legs: Leg I longer and wider than following legs. to GA. Several species with crescent sclerotized areas Genua I somewhat shorter than telofemora. Tibiae longer on either side of GO. Female genital sclerites with 3–5 than genua. Leg I with prominent spines, telofemur to pairs of subgenital setae. Male GA rounded or oval tarsus I with 3,2,3,1 such spines. Basifemora I to IV in outline; number of perigenital setae surrounding with 3,4,2,2 setae. Tibiae II–IV with 4 ventral setae GO ranging from about 30 to more than 150; a pair each, 1–3 of these setae spiniform and pectinate. Tarsi of outlying perigenital setae may be present within slightly bent. Tarsus I with 3 dorsal setae, baculiform striated integument. Genital sclerites with 3–5 pairs of dorsolateral solenidion, 1 medial spine, 3–5 ventral subgenital setae. setae, and apical pair of doubled parambulacral setae. Gnathosoma: Longer than wide. Gnathosomal base Tarsus II with 3 dorsal setae, dorsomedial solenidion, 3 subquadrangular in ventral aspect. Rostrum almost ventral setae and pair of doubled parambulacral setae. parallel-sided, ending bluntly. Both pairs of maxillary Tarsi III and IV with 3 dorsal setae, 1–2 ventral setae setae on rostrum. Palps 4-segmented, lateral to and pair of parambulacral setae. gnathosoma and extending beyond rostrum. P-2 with Each tarsus with paired claws and stout median 2 setae, generally both in apical half. P-3 short, with claw. a medial spine. P-4 with 3 basal setae, 1 seta in the Biology and distribution. Larval, protonymphal and middle and 1 minute seta and 2 spurs at the tip. deutonymphal stage present. Five species are described, Legs: Leg I in most species longer and wider than one from the Atlantic Ocean and Mediterranean, one following legs, with spines on telofemur and spines from South Africa and three from Australia. or strong, bristle-like setae on genu and tibia. Genu I Remarks. Halacaropsis and Agauopsis share the about as long as telofemur and tibia I. Genua of the shape of leg I, enlarged and armed with long, apically other legs, too, almost as long as adjoining segments. truncate spines. Halacaropsis can be separated from Basifemora I to IV with 2(–3),2–5,2,2 setae. Telofemur Agauopsis with help of its number of ventral setae on I with 1–5 ventral spines; spines tapering or blunt. the tarsi, the length ratio of telofemur I to genu I, that Genu I with 1(–2) pair(s) of spiniform or bristle-like of P-3 to P-2, and the size of the median claw on the setae. Tibia I with 4–6 often spiniform ventral setae; tarsi. tibiae II, III and IV with 2–7 ventral bristle-like setae. Halacaropsis has characters in common with Tarsus I with 3 dorsal setae (1 species with 5 setae), Halacarus. In Halacarus, too, leg I is longer than the baculiform dorsolateral solenidion and famulus, 2–4 following legs and its telofemur, genu, tibia and tarsus ventral bristle-shaped setae , and 2–5 pairs of eupathidia are armed with spines, and the tarsi bear several ventral (parambulacral setae included). Tarsus II with 3(–5) setae. Halacarus has five (rarely four) pairs of gland dorsal setae, dorsomedial solenidion, 0–4 ventral setae, pores, whereas in Halacaropsis the posterior gland and pair of doubled or tripled parambulacral setae. Tarsi pores are vestigial or absent. Halacarus has both pairs III and IV with 3–4 and 3 dorsal setae, respectively, of the maxillary setae on the rostrum and the median 0–6 ventral setae, and pair of parambulacral setae. claw of the tarsi is rarely enlarged. Parambulacral setae of male tarsus IV often plumose. References. Bartsch (1996b), Otto (1999a), Proches Pair of claws of leg I may be slightly smaller than (2001). those of following legs. Paired claws either smooth Halacarus Gosse, 1855 (Fig. 41) or with accessory process and pecten. Median claw Diagnosis. Idiosoma: Length 250–1500 µm. Dorsal present, usually small, rarely almost as long as paired plates smooth or faintly reticulated; no prominent claws. costae or conspicuous porose areolae present. Dorsal Biology and distribution. One free-living larval plates may be obscured by layers of striated or maze- and two nymphal stages occur during development.

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More than 70 species are described. The genus is the plates are small, after feeding the dorsal aspect is cosmopolitan and abundant in polar as well as in tropical dominated by the wide areas of striated integument areas. More species have been taken in the southern and the plates are apparently small. The three species than in the northern oceans. Halacarus inhabits depths described were taken from New Zealand waters. from the low water edge to deep-sea basins. Remarks. Halixodes resembles species of the Remarks. Halacarus is distinguished from genus Agaue which have similar large cerotegumental Halacarellus, Halacaropsis, and Thalassarachna on lamellae on idiosoma and legs, but differs in that the the basis of the 2 setae on the P-2, the length of the gnathosoma bears large barbs at the tip of rostrum genua being about as long as the adjoining segments, and the palps are flattened and form a trough, whereas and the 5 pairs of large gland pores (though Halacarus Agaue species have two minute spurs at the tip of the species with no more than 4 pairs of pores do exist). rostrum and the palps are almost cylindrical. References. Bartsch (1981a, 2001c), Newell (1984), References. Bartsch (1986a). Otto (2001b). Isobactrus Newell, 1947 (Fig. 43) Halixodes Brucker & Trouessart, 1900 (Fig. 42) Diagnosis. Idiosoma: Length 275–650 µm. Dorsal Diagnosis. Idiosoma: Length 1100–1300 µm. plates AD, OC and PD present, two or more plates Dorsal and ventral plates large, with cerotegumental may be fused. OC with a single cornea. Gland pores in membranes. Dorsum with 6 pairs of setae; adanal most species present but small, AD and PD each with setae on anal plate. AE with 3 ventral setae; PE with 1 pair of such pores; OC with 2 pores. Dorsum with 1 dorsal and 3 ventral setae. Female GA with up to 13 5, rarely 4 or only 2 pairs of idiosomatic setae; adanal pairs of perigenital setae. Male with approximately 200 setae absent. Ventral plates delicate, generally reduced perigenital setae close around GO. to small platelets. Epimera I and II rarely fused to an Gnathosoma: Longer than wide. Rostrum long, AE; a median plate separated from marginal epimera parallel-sided, almost as long as gnathosomal base. may be present. Epimeral plates III and IV of each Both pairs of maxillary setae near base of rostrum. Two side contiguous or separated by striated integument. large pairs of barbs at end of rostrum. Palps lateral to Anterior half of idiosoma with 3 pairs of ventral setae. gnathosoma; extending just beyond rostrum. Dorsal and Epimeral plate III with 0–1 dorsal and 1 ventral seta ventral lamellae of P-2 and rostrum forming a trough. (the latter sometimes within the striated integument), P-2 long, with 1 distal seta. P-3 with 1 small bristle. epimeral region IV with 1 ventral seta. GP in females P-4 with 3 setae and 2 apical spinelets. Chelicerae with often reduced; 3(–4) pairs of perigenital setae positioned serrate dorsal margin. on the plate or within the striated integument; genital Legs: Slender. Telofemora with cerotegumental sclerites with 1–2 subgenital setae. Male GP larger than lamellae. Tarsi with large membranes of claw fossae. that of female; with 32–98 perigenital setae and (3–)4 Genua shorter than adjoining segments. Basifemora pairs of subgenital setae. I to IV with 2 setae each. Tibiae with short bristle- Gnathosoma: Short, its length almost same or even like setae, none of them bipectinate. Tibiae I and less than width. Gnathosoma directed ventrad and II with 5–6 ventral setae, tibiae III and IV with 4–5 often concealed in dorsal aspect. Gnathosomal base such setae. Tarsus I with 3 dorsal setae, 1 solenidion globular. Rostrum conical; both pairs of maxillary on dorsolateral fossa membrane, 1 ventral seta, and setae on rostrum. Laterally attached 4-segmented palps apically approximately 20 eupathidia (parambulacral slightly surpassing rostrum. P-2 with 1 distal seta, no setae included). Tarsus II with 3 dorsal setae, seta on P-3 (P-3 may be almost reduced), P-4 with 4 solenidion on inner flank of medial fossa membrane, (rarely 3) setae. and approximately 15 apical eupathidia (parambulacral Legs: Short. Legs I and II similar in shape. Genua setae included). Tarsus III and IV each with 3 dorsal shorter than adjoining segments. Basifemora I–IV with setae; apically with parambulacral setae. 2,2,1–2,0–2 setae. Genua I–IV with 2–3,2–3,1–3,1–2 Tarsi end with pair of claws. Central sclerite lack a setae. Tibiae I and II with pair of ventral setae; tibiae claw-like process. III and IV with 1–2 ventral setae; bipectinate setae on Biology and distribution. Two nymphal stages are tibiae I–IV numbering 1,0–1,0–1,0–1. Solenidia small, known. Halixodes has been found in the mantle cavity clavate, on both tarsus I and II in dorsolateral position. of molluscs but also free-living in crevices between Tarsi I, II, IV with 3 dorsal setae (except for 1 species gravel and colonies of barnacles and mussels. All present which has basidorsal seta doubled) and 0 ventral setae, records are from the tidal and shallow subtidal zone. tarsus III with 4 dorsal setae (except for 1 species with Nymphal stages demonstrate an enormous difference 5 setae) and 0 ventral setae. Tarsi with apical pair of in length, in just hatched individuals the areas between parambulacral setae.

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All tarsi with a carpite between tip of tarsus and Legs: The majority of species with slender legs. central sclerite. The 2 claws on tarsi I–IV smooth or Genua much shorter than adjoining segments. with accessory process, the latter with small or strong Basifemora with (1–)2–3,(1–)2–3,3(–4),(1–)3 setae. tines. No claw on central sclerite. Tibia I with 4–8 bipectinate ventral bristles. Tibia II Biology and distribution. One larval and three with 3–6 ventral setae, bristle-like and bipectinate nymphal stages (proto-, deuto-, tritonymph) present. or slender and only faintly pectinate. Tibiae III and Records of the presently described 27 species are IV with 2–7 ventral setae, either bristle-like and from the intertidal of marine and brackish waters. bipectinate or slender, only faintly pectinated. Tarsus Two species are recorded from almost freshwater I with 3 dorsal setae, baculiform solenidion, 0–4 areas. Isobactrus is found on algae and barnacles, bipectinate ventral setae, 0–4 ventral eupathidia, and shells and pebbles covered with unicellular algae. It is pair of parambulacral setae. Tarsus II with 3 dorsal phytophagous, feeding on unicellular or filamentous setae, dorsal or dorsomedial solenidion, 0–4 ventral algae. In the boreal Atlantic Ocean, this cosmopolitan setae (basal setae bipectinate, distal setae bipectinate genus is found regularly and in large numbers in the or smooth), and pair of parambulacral setae. Tarsi III upper tidal zone. and IV with 4 and 3(–4) dorsal setae, respectively, Remarks. Isobactrus, like Metharhombognathus, 0–6 ventral, usually bipectinate setae, and pair of Rhombognathides and Rhombognathus, has a dark- parambulacral setae. green body, the legs are transparent. The four genera are Claws smooth or with an accessory process; the algivorous. Isobactrus has the gnathosoma completely latter may bear tines. Central sclerite small. Tarsi often or almost completely concealed beneath the anterior with a short carpite between tip of tarsus and central idiosoma, whereas in most species of the other genera sclerite. the gnathosoma is visible in dorsal aspect. Biology and distribution. One larval and two free- References. Newell (1947), Abé (1996a, 1998, living nymphal stages are known. At present about 2001), Bartsch (2003a, b). 30 marine species are described. Lohmannella is cosmopolitan. The majority of the southern hemisphere Lohmannella Trouessart, 1901 (Fig. 44, 8C) species have large gland pores, whereas in those from Diagnosis. Idiosoma: Length 210–560 µm. Generally the north the pores are small or vestigial. Lohmannella wide and flattened. Dorsal and ventral plates large. AD species are found in shallow tidal waters as well as in subquadrangular to hexagonal. Often with 5 pairs of deep sea basins. Lohmannella inhabits marine, brackish gland pores which may be large and prominent, minute and fresh waters. Five species are recorded from fresh or, rarely, replaced by setae. Second pair of gland pores, or diluted brackish water. if present, marginally or ventromarginally on platelets Remarks. Lohmannella is related to Scaptognathus within striated integument. Dorsum with 6(–7) pairs of but has a slender rostrum and 4-segmented palps. idiosomatic setae; adanal setae inserted on anal cone. References. Newell (1984), Bartsch (1986c, 1993a, AE with 4 pairs of ventral setae. PE with 1–3 dorsal 2003d). and 3 ventral setae. Female GA with 12–74 perigenital setae and 3–4 pairs of subgenital setae. Male GA with Metarhombognathus Newell, 1947 (Fig. 45) 50–80 perigenital setae in a dense ring around GO, plus Diagnosis. Idiosoma: Length 320–610 µm. In adults 1–5 pairs of outlying perigenital setae; genital sclerites dorsal plates AD, OC and PD small. OC with 1–2 with 4 pairs of tiny subgenital setae. corneae. Dorsum with 8–10 idiosomatic setae; adanal Gnathosoma: Longer, often much longer than setae on anal plate. First pair of gland pores on AD; wide. Length ratio gnathosoma:idiosoma equalling following gland pores often replaced by setae. Ventral 0.4–1:1. Gnathosomal base cubical, rostrum slender, plates small. Anterior epimeral plate divided into parallel-sided. The majority of species with rostrum right and left half; each plate with 3 setae. PE with 1 distinctly longer than gnathosomal base. Both pairs of dorsal and 2 ventral setae. GP small, in females almost maxillary setae on rostrum, generally in distal half of reduced. Female with 3 pairs of perigenital setae and rostrum. Palps 4-segmented, inserted dorsally. Pair of 0 subgenital setae. Males with 30–40 perigenital setae P-1 adjacent or even fused, rarely separated by almost and 3 pairs of subgenital setae. width of P-1. Palps slightly surpassing rostrum. P-2 Gnathosoma: About as long as wide. Rostrum with 2 dorsal setae; in many species from the southern much shorter than gnathosomal base; apically truncate. hemisphere 1–5 cuticular ventral spines present (Fig. Palps 4-segmented; reaching beyond rostrum. P-2 with 8C). P-3 short, with spur-like process (no real spur 1 distal seta, P-3 reduced to minute ventral sclerite with because an alveolus is lacking). P-4 with 3 setae and 1 a setula, P-4 with 3 setae in basal whorl; 1 of setae wide medial spur, apically with eupathid setula and spur. and flattened.

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Legs: Legs with short, globular segments. Leg I not without enlarged fossa membranes. Basifemora I–IV markedly longer than following legs. Basifemora I–IV with 2,2,1,1 setae. Tibiae I–IV each with 2 spiniform, with 2,3,2,2 setae. All tibiae with a pair of spiniform pectinate ventral setae. Tarsus I with 3 dorsal setae, ventral setae. Tarsus I with 3 dorsal setae, clavate dorsolateral solenidion, and 1–2 ventral setae (exclusive dorsolateral solenidion, rod-like famulus, and 1 ventral of parambulacral setae). Tarsus II with 3 dorsal setae, spiniform seta near tip of tarsus. Tarsus II without dorsomedial solenidion, and 1 ventral seta. Tarsi III and famulus, otherwise identical with tarsus I. Tarsi III IV with 4 and 3 dorsal setae, respectively, but no ventral and IV with 4 and 3 dorsal setae, respectively, and 0 setae. All tarsi with pair of parambulacral setae. ventral setae. Pair of parambulacral setae on tarsi I and Paired claws large. Median claw present but II doubled and eupathid, on tarsus IV spur-like, and distinctly smaller than paired claws. on tarsus III in a combination of 1 lateral spur and 1 Biology and distribution. Two nymphal stages do medial eupathid seta plus spur. occur during the ontogeny. Three species are described, All tarsi with a rod-like carpite between tip of tarsus two have been collected in Antarctic and Subantarctic and central sclerite. Median claw almost as large as waters, one species in the tropical eastern Australia. paired claws, accordingly all tarsi with 3 stout claws. The depth range is from low water edge to 155 m. The Median claw smooth, paired claws serrate or with species supposedly live in coarse sediments. apical tines. Remarks. Mictognathus with its contiguous or Deutonymphs: Dorsal and ventral plates much fused plates and large lamellae on the legs resembles larger than in adults. Epimera I and II either separated species of Copidognathus. In contrast to the latter, P-4 in the median or fused to an AE. Genital and anal plate bears a single basal seta. fused. References. Newell (1984), Bartsch (1992a), Otto Biology and distribution. One larval and two (2001a). nymphal stages are known. The deutonymphs are, Parhalixodes Laubier, 1960 (Fig. 47) unique within the Halacaridae, much more intensely armed than the adults are. Only two species are Diagnosis. Idiosoma: Length 400 µm. Idiosoma described. Metarhombognathus inhabits the boreal and slender, its width less than distance between epimera arctic North Atlantic Ocean. The species live, often II and III. AD present, not markedly reduced, PD short, in large numbers, in the mid-tide green-algal belts, as OC lacking. Dorsum with at least 4 pairs of idiosomatic well as amongst intertidal barnacles and brown algae. setae, ds-2, ds-3 and ds-4 very long. Ventral plates small Metarhombognathus is algivorous. and delicate; widely separated. Female GA hardly Remarks. In Metarhombognathus, as in Isobactrus, extending beyond GO. Rhombognathides and Rhombognathus, the body is Gnathosoma: Slender. Rostrum long, parallel- dark-green, the legs are pale. Metarhombognathus is sided, apically with pair of barbs. Palps 4-segmented, distinguished from the other just mentioned genera on lateral to gnathosoma and surpassing rostrum. P-2 with the basis of the three large claws on the tarsi. 1 large distal seta. No seta on P-3. Apical half of P-4 References. Abé (1998), Bartsch (1979, 2003b). with 2 setae and 2 spinelets. Chelicera slender. Large cheliceral claw with few stout tines. Mictognathus Newell, 1984 (Fig. 46) Legs: Slender. Dorsal and lateral setae long and Diagnosis. Idiosoma: Length 340–450 µm. Dorsal and slender. Legs III and IV inserted close to posterior ventral plates large, contiguous or fused; plates strongly end of idiosoma. Genua shorter than telofemora and sclerotized. Dorsal plates with raised areolae. Dorsum tibiae. All tibiae with 2 ventral bristles. Tarsus I with with 5 (or 6?) pairs of dorsal setae; adanal setae on anal 3 dorsal setae, setiform solenidion, 1 ventral seta, and plate. AE with 3 pairs of ventral setae. PE with 1 dorsal pair of parambulacral setae. Tarsus II with 3 dorsal seta and 3 ventral setae. Female GA with 3 pairs of setae, dorsomedial solenidion, 0 ventral setae, and pair perigenital setae; genital sclerites lack subgenital setae. of parambulacral setae. Tarsi III and IV each with 3 Male GA with approximately 26–40 perigenital setae dorsal but no ventral setae; each tarsus with pair of and 3 pairs of subgenital setae. parambulacral setae. Gnathosoma: Longer than wide. Rostrum slender- Paired claws of ‘normal’ size. Median claw almost triangular. Both pairs of maxillary setae on rostrum. half length of paired claws. Palps 4-segmented; inserted laterally; surpassing the Biology and distribution. Parhalixodes is believed rostrum. P-2 with 1 distal seta, slender or pectinate. to be a parasite. Two species are described. Parhalixodes Medial seta on P-3 minute or absent. P-4 with 1 basal travei Laubier, 1960 was found in Mediterranean on seta; apically with setula and 2 spurs. the nemertine Cerebratulus hepaticus Hubrecht, 1879. Legs: Leg I slightly larger than following legs. P. chilensis Newell, 1971 is known from a single Telofemora with ventral (and dorsal) lamellae; tarsi

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 31 protonymph, found in a sample taken from off South arranged around the GO (in Werthella in a ring close America. to the GO). Remarks. With its slender idiosoma and legs, References. Bartsch (1986d). Parhalixodes resembles the arenicolous genera Anomalohalacarus and Arenihalacarus as well as the Peregrinacarus Bartsch, 1999 (Fig. 49) presumably temporarily parasitic Australacarus. The Diagnosis. Idiosoma: Length 480–700 µm. Dorsum three latter genera have no barbs at the end of rostrum, with AD, pair of OC and PD, and 6 pairs of idiosomatic their P-2 are much longer relative to P-3, and the P-4 setae; adanal setae on anal plate. Elongate OC with two bear three setae in the basal whorl. gland pores. Venter with AE, pair of PE and GA. AE References. Laubier (1960), Newell (1971). with 3 pairs of setae, PE with 1 dorsal seta and 3 ventral setae. Genital plate and anal plate fused; female GA Pelacarus Bartsch, 1986 (Fig. 48) with 10–14 perigenital setae, genital sclerites with 0–1 Diagnosis. Idiosoma: Length 360–450 µm. Dorsal subgenital setae. Male GA with about 40 perigenital plates AD, OC and PD panelled and with porose raised setae. Genital sclerites with 5–6 pairs of subgenital areas. With 6 pairs of dorsal setae; adanal setae on anal setae. plate. Gland pores inconspicuous. Ventral plates with Gnathosoma: Longer than wide. Rostrum elongate, porose areolae. AE with 3 pairs of setae and enlarged triangular. Basal pair of maxillary setae near base of epimeral pores. PE with 1 dorsal and 3 ventral setae. rostrum, following pair in distal half of rostrum. Apex Female GA with 3 pairs of perigenital setae and 3 pairs of rostrum with 2 pairs of rostral setae. Four-segmented of subgenital setae. Male GA with 16–22 perigenital palps lateral to gnathosoma. P-2 with 1 dorsal seta. P-3 setae scatteredly arranged; genital sclerites with 5 pairs with medial spine. P-4 with 3 setae in a basal whorl. of subgenital setae. Legs: Genua distinctly shorter than both tibiae Gnathosoma. Rostrum triangular, tapering, about and telofemora. Basifemora with 2,3,2–3,2–3 setae. as long as gnathosomal base. Tectum truncate, scale- Telofemur I with ventral seta(e) or spines. Tibia I with like. Both pairs of maxillary setae inserted within basal 6–8 ventral setae, several of them spiniform. Tibiae II– portion of rostrum. Four-segmented palps about as long IV with 5,2–3,2–3 ventral setae, 3,1–2,1–2 of these setae as rostrum and lateral to gnathosomal base. P-2 with 1 bipectinate. Tarsus I with 3 dorsal setae, dorsolateral distal seta. No seta on P-3. P-4 with 1 long basal seta solenidion, 2–4 small ventral eupathidia, and pair of and 1 apical setula and 2 spurs. parambulacral setae, but no ventral or ventromedial Legs: Genua much shorter than adjacent leg seta. Tarsus II with 3 dorsal setae, dorsomedial segments. Basifemora with 2,(2–)3,2,2 setae. All tibiae solenidion, and pair of parambulacral setae. Tarsi III with 2 smooth ventral setae. Solenidion on tarsus I in and IV each with 3 dorsal setae and apical pair of small dorsolateral position, on tarsus II in dorsomedial. Tarsi parambulacral setae. I–IV with 4,4,4,3 dorsal and 1,1,0,0 ventral setae. All Tarsi I–IV end with pair of claws and minute median tarsi with pair of parambulacral setae. claw. Paired claws of tarsus I slightly smaller than those Paired claws large; median claw small. of following legs. Biology and distribution. The ontogeny includes Biology and distribution. With one larval and two a free-living deutonymphal stage. Pelacarus is known nymphal stages. The genital acetabula of nymphs are from the sublittoral Mediterranean and the abyss in the somewhat enlarged. Bay of Biscay. Two species are known, they have been extracted Remarks. Pelacarus resembles Werthella species. from slightly brackish freshwater, from the Subantarctic The ornamentation of the dorsal and ventral plates Marion Island and the Falklands. is almost the same, the epimeral pores on the AE Remarks. Peregrinacarus resembles Halacarellus. are enlarged, the shape of the gnathosoma is almost The most marked difference is that tarsus I of identical, on P-4 there is a single seta in the basal Halacarellus has a ventromedial spine or seta distinctly whorl; the setation of the tarsi is almost identical. separated from the apical eupathidia, this seta is absent Nonetheless, Pelacarus is a separate genus; in Pelacarus in Peregrinacarus. a deutonymphal stage occurs during ontogeny (in References. Bartsch (1999a, 2001b). Werthella suppressed), on tarsus II the solenidion is in a dorsomedial position and there is one ventral seta Phacacarus Bartsch, 1992 (Fig. 50) (in Werthella solenidion in dorsolateral position and Diagnosis. Idiosoma: Length 220–310 µm. Surface ventral seta often lacking), the female genital sclerites of plates AD, OC and PD almost smooth. In males each bear three subgenital setae (in Werthella one dorsal plates very delicate. Dorsum with 2 pairs of pair), and in males the perigenital setae are scatteredly dorsal idiosomatic setae (ds-1 and ds-2). Adanal setae

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 32 not seen. AE with 3 pairs of setae and pair of epimeral I–IV with 2,3,2,2 setae, respectively. Tibiae I and II pores. PE with 1 dorsal seta and 2 ventral setae. Both each with 1 pair of ventral setae, on tibia I both setae female and male GA with 2 pairs of perigenital setae; spiniform and bipectinate, on tibia II either 1 or both subgenital setae lacking. of setae stout and bipectinate. Tibia III and IV with Gnathosoma: Short; wider than long. Pharyngeal 1–2 ventral setae. Tarsi I with 3 dorsal setae, setiform plate large. One pair of maxillary setae on gnathosomal solenidion and famulus (dorsolateral in position), and base, 1 pair at base of rostrum. Palps 4-segmented. P-2 1 ventral spur near the tip. Tarsus II resembling tarsus with 1 distodorsal seta. No seta on P-3. P-4 with 3 setae I but famulus lacking. Tarsus III with 4 and tarsus IV in basal whorl. with 3 dorsal setae; these tarsi lack ventral setae. Tarsi I Legs: Short. Genua much shorter than both and II with pair of doubled parambulacral setae. Tarsus telofemora and tibiae. Female with large lamellae III with a spiniform lateral parambulacral seta and a on telofemora I–IV; lamellae of legs of male much seti- plus spiniform medial parambulacral seta; tarsus smaller. Basifemora with 2,2,2,2 setae. Tibiae I and II IV with pair of spiniform parambulacral setae. each with 3 ventral setae, tibiae III and IV with 2 setae. All tarsi with rod-like carpite between tarsal tip and Tarsus I with 3 dorsal setae, dorsolateral solenidion, 3 central sclerite. Paired claws large; either smooth or ventral setae, and pair of apical parambulacral setae. distally widened and armed with numerous slender Tarsus II with 3 dorsal setae, dorsolateral solenidion tines. Central sclerite may bear a smooth median claw and apical pair of parambulacral setae. Tarsi III and IV which is minute or about two thirds of length of paired with 4 and 3 dorsal setae, respectively, and apical pair claws. of parambulacral setae. Tarsi II–IV lack ventral setae. Biology and distribution. One larval and two Tarsi with paired claws and small median claw. nymphal stages are known. Six species are described Biology and distribution. At present the only (exclusive of doubtful species). Rhombognathides is juvenile stage found is the larva. One species is abundant in intertidal and subtidal areas in the North described which has been collected amongst bushy Atlantic Ocean, Baltic and Black Sea, on algae and in corallines growing on rocky shores on the western unsorted sediment. The species are algivorous. coast of Australia. Remarks. The mites are dark-green due to the Remarks. Phacacarus resembles species of green gut content. Rhombognathides is separated from Copidognathus. The most marked differences are: the Isobactrus and Rhombognathus, which have a similar reduced number of dorsal idiosomatic setae, the very dark-green idiosoma, by its flattened, intensely armed short gnathosoma, and the male GA with no more than idiosoma and the presence of a ventral spur at the tip 2 pairs of perigenital setae and absence of subgenital of tarsus I and II. Metarhombognathus, with a dark- setae. green idiosoma and a ventral spur on tarsus I and II, References. Bartsch (1992b, 1994a). has 3 almost equal-sized claws on all legs whereas in Rhombognathides the median claw, if present, does not Rhombognathides Viets, 1927 (Fig. 51) reach the size of the paired claws. Diagnosis. Idiosoma: Length 280–460 µm. Often References. Abé (1998), Bartsch (2003b). flattened. Dorsal and ventral plates large, contiguous or fused. Dorsum with 10 pairs of idiosomatic setae; Rhombognathus Trouessart, 1888 (Fig. 52) adanal setae on anal plate. Several of dorsal idiosomatic Diagnosis. Idiosoma: Length 190–790 µm. Dorsal setae with a gland pore at their base. OC with 3 setae plates AD, OC and PD present, 2 or more plates may and 1–2 corneae. First pair of gland pores on AD. AE be fused. Dorsum with 5–6 pairs of idiosomatic setae; fused medially; with 3 pairs of ventral setae. PE with adanal setae on anal plate. OC with 2 dorsal setae, 2 1 dorsal and 2 ventral setae. Female GA with 3 pairs gland pores and often 2 corneae. PD with 1 or 2 dorsal of perigenital setae; genital sclerites without subgenital setae. Ventral plates often fused, rarely separated into setae. Male with 30–83 perigenital setae and 3 pairs of AE, PE and GP. AE (or area of AE) with 3 ventral subgenital setae. plus 0–6 adjunct marginal setae immediately posterior Gnathosoma: Hardly longer than wide. Rostrum to insertion of leg II; internal epimeral tubes present conical, much shorter than gnathosomal base; with 2 but rather inconspicuous. PE with (0–)1 dorsal and 3 pairs of maxillary setae. Palps flattened, 3-segmented, ventral setae, and 0–3 adjunct marginal setae anterior closely pressed to rostrum. P-2 with 1 distal seta. to insertion of leg III. Female with 1–45 pairs of Apical palpal segment with 3 wide setae, the dorsal perigenital setae and (1–)2 pairs of subgenital setae. seta flattened. Majority of males with 7–25 pairs of perigenital setae Legs: Legs short. Genua shorter than adjoining and 2 pairs of subgenital setae; perigenital setae often segments. Legs I and II similar in shape. Basifemora plumose and in trapezoidal arrangement.

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Gnathosoma: Generally longer than wide. Rostrum the pair of outlying setae. Male genital sclerites with 3 short and conical or parallel-sided and about as long subgenital setae. as gnathosomal base. Both pairs of maxillary setae on Gnathosoma: Length equalling 0.4–0.6 of idiosomal rostrum. Palps 4-segmented, extending just beyond length. Gnathosomal base quadrangular. Rostrum rostral tip. P-2 with 1 distal seta; no seta on P-3; 3 setae slender, parallel-sided, as long as or somewhat longer in basal whorl of P-4. than gnathosomal base. One pair of maxillary setae Legs: Legs I and II similar in their shape. Basifemora inserted on gnathosomal base near rostral base, 1 pair I and II with 2 and 2–6 setae, respectively; basifemora near apex of rostrum. Palps 2-segmented, P-2, P-3 and III and IV with 1–2 setae each. Tibiae I–IV normally P-4 fused; palps inserted laterally, separated from each with 2 ventral bristle-shaped setae, rarely tibiae III other by more than width of P-1, and extending to end and IV with just 1 such seta. Ventral setae of tibia I of rostrum. Second palpal segment with 1 seta in basal bipectinate. Tarsi I, II and IV with 3 dorsal and 0 portion and 3 setae plus 4 spines in apical portion. ventral setae, tarsus III with (3–)4 dorsal and 0 ventral Spines level with apex of rostrum. setae. Dorsolateral solenidion of tarsi I and II generally Legs: Leg I distinctly larger than following legs. setiform. All tarsi apically with pair of parambulacral Telofemur I long, tibia I longer than genu but less than setae which are eupathid on tarsi I and II, eupathid, half length of telofemur and often shorter than tarsus I. setiform or scaliform on tarsi III and IV. Parambulacral All genua shorter than tibiae. Basifemora I–IV with 2 setae on tarsus IV often pectinate or divaricate, in setae each. Tibia I–IV each with pair of short bristle-like males medial parambulacral seta normally long and ventral setae. Tarsi I and II each with 3 dorsal setae, 1 plumose. dorsolateral solenidion and 0 ventral setae; tarsi III and With rod-like carpite between tip of tarsus and IV with 3–4 and 3 dorsal setae, respectively, both tarsi median sclerite. Paired claws either smooth, with a J- lack ventral setae. Tarsi I–IV each with pair of small shaped pecten or with an accessory process, the latter parambulacral setae. may be widened and armed with more than 20 tines. Tarsus I with pair of large claws; their pecten with Central sclerite never with a large claw-like hook. umbrella-like arranged tines. On following legs tines Biology and distribution. Most of the almost 100 of claw pecten arranged along ventral flank of claw. species described have 3 nymphal stages, the proto- Central sclerite minute, without distinct claw-like , deuto- and tritonymph. Rhombognathus inhabits process. A carpite-like sclerite may be recognized intertidal and subtidal areas, single records are from between tip of tarsus and central sclerite. about 100 m depth. Some species are adapted to life in the Biology and distribution. One larval and two upper littoral zone. Beside on algae, Rhombognathus is nymphal stages are known, the proto- and deutonymph. found in sandy deposits. Rhombognathus is algivorous. Scaptognathides is arenicolous. The 10 species The genus demonstrates a cosmopolitan distribution. described are from tropical and warm-temperate areas. Most of the species are marine, few, probably endemic Remarks. Unique in Scaptognathides is the shape species, live in brackish waters, in the meso- and of gnathosoma and leg I. The gnathosoma has a slender oligomixohaline zone. rostrum and two-segmented palps with four apical Remarks. There is an unusual high intraspecific spines. The telofemur of leg I is long, the tibia short variability in respect of number of adjunct setae and and the tines on the claws of tarsus I are arranged setae on telofemora, often also of those on basifemora, umbrella-like. genua and tibiae. References. Monniot (1972), Bartsch (1996d), Otto References. Abé (1996a, 1998), Bartsch (2000, (2000b). 2003b). Scaptognathus Trouessart, 1889 (Fig. 54) Scaptognathides Monniot, 1972 (Fig. 53) Diagnosis. Idiosoma: Flattened. Length 140–480 µm. Diagnosis. Idiosoma: Length 130–220 µm. Idiosoma AD and PD large, panelled or porose. OC small, less flattened. AD and PD large, OC much smaller. AD than 50 µm in diameter. AD, OC and PD each with pair rectangular to hexagonal; first pair of gland pores in of gland pores. Dorsum with 7, rarely 6 pairs of small truncate anterior margin. OC with 1 or 2 gland pores, dorsal setae; no setae close to anal cone. Ventral plates rarely with a minute seta. PD with 2 pairs of gland large. AE with 3 pairs of setae and often with pair of pores. Dorsum with 6 pairs of setae; adanal setae on distinct epimeral pores. PE with 1 dorsal and 3 ventral anal plate. Ventral plates large, delicate. AE with 3 setae. Female GA rarely uniform, generally bipartite pairs of setae and minute pair of epimeral tubes. PE or tripartite, i.e., anterior (bipartite GA) or median with 1 dorsal and 3 ventral setae. Females with 2 pairs (tripartite GA) transverse portion coarsely striated, of perigenital setae and 0–1 pairs of subgenital setae. remainder of plate structured as AE and PE. Posterior Males with 7–16 pairs of perigenital setae, included portion of female GA with 2–4 pairs of subgenital

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 34 setae; majority of species with 2 (rarely 1 or 0) pairs of rounded or subtriangular, or largely reduced, elongate. subgenital setae. Male GA either uni- or bipartite, rarely Gland pores minute or vestigial. With 6 pairs of dorsal coarsely striated areola separated and situated anterior setae; pairs of ds-1 and ds-3 usually on AD, ds-4 and ds- to remainder of GA. Male GA with 12–40 perigenital 5 on PD and adanal setae on anal cone, either in dorsal setae and 3, rarely 2, pairs of subgenital setae. or ventral position. AE with 3 pairs of ventral setae and Gnathosoma: Large; length 0.5–0.9 of idiosomal a pair of generally large epimeral vesicles. PE with 1 length. Rostrum spatula-shaped or wide and lamellar, dorsal and 3 ventral setae. PE seemingly divided into apex truncate. Both pairs of maxillary setae inserted EIII and EIV though probably always fused. Female in posterior half of rostrum; two pairs of rostral setae GA with 4–5 pairs of perigenital setae, no subgenital in lateral and medial margin of apex. Palps inserted setae. Males with approximately 10–25 pairs of dorsally; interval between P-1 less than their width. perigenital setae arranged around the GO and 0–3 pairs Palps 2-segmented (P-2, P-3 and P-4 fused), rarely of outlying perigenital setae; its genital sclerites with seemingly 3-segmented (P-2 separate, P-3 and P-4 3 subgenital setae. Perigenital setae generally filiform, fused), and extending to end of rostrum. Palpal shaft rarely plumose. (corresponding to P-2) with 1 basal and 1 distal seta; Gnathosoma: Broadly attached to idiosoma. apex of palp (corresponding to P-3 and P-4) with 2 Gnathosomal base almost spherical, rostrum short, large spines, 2 long setae, its tip with 1 setula and 2 conical. Rostrum shorter than gnathosomal base. One spinelets. pair of maxillary setae near base of rostrum, 1 pair Legs: Slender. Genua shorter than adjoining segment. close to tip of rostrum. Palps attached to gnathosoma Basifemora I–IV with 1–2,1–2,1(–2),1(–2) setae. dorsally; P-1 almost adjacent. Palps 3-segmented, Telofemora I–IV with 0–3,0–2,0,0 bipectinate dorsal extending to end or somewhat beyond rostrum. Second or dorsomedial setae. Genua I–IV with 0–2,0–1,0,0 palpal segment with 1 strong ventral seta and often bipectinate ventral setae. Tibia I with 3–6 bristle-like with quadrangular ventral apophysis. Apical segment bipectinate ventral setae. Tibiae II–IV with 2–4 ventral short, with 1 dorsal seta close to base of segment and 3 setae, 1–4 are bipectinate. Tarsus I with 3 dorsal setae, setulae at the tip. dorsolateral solenidion and famulus, 0–1 bipectinate Legs: Telofemora and tibiae strong; genua small ventral setae plus 0–1 short ventral setae. Tarsus II with and spherical. Telofemora often with ventral carinae. 3 dorsal setae, a solenidion in dorsal to dorsomedial Tibia I clavate, with narrow base and wide, truncate position, and 0–1 bipectinate ventral setae. Tarsi III end. Tibia of leg I larger than tibiae of following legs. and IV with 3–4 and 3 dorsal setae, respectively, and Short tarsus I with length:height ratio 1.2–3.1; tarsi 0 ventral setae. All tarsi with pair of parambulacral II–IV at least 3 times longer than high. Basifemora I setae. to IV with 2(–3),2,1,1 setae. Tibia I with large ventral Paired claws large; usually with minute accessory spine; often that spine basally wide, distally tapering. process. Central sclerite generally with very minute Ventromedial seta of tibia I slender, rarely spiniform, process, rarely with large median claw (almost half always much shorter than ventral spine. Tibiae II, III length of paired claws). and IV with 2 pectinate ventral setae. Tarsus I with 3 Biology and distribution. One larval and two dorsal setae, dorsolateral solenidion and famulus, and 1 nymphal stages are known. Almost 30 species are strong, often spiniform ventral seta; apically with pair described as yet; most of them are recorded from warm of parambulacral setae. Tarsus II with 3 dorsal setae, and temperate regions, though Scaptognathus is also solenidion on medial membrane of claw fossa, (0–)1 found in subpolar waters. The species inhabit sandy ventral seta, and pair of parambulacral setae. Tarsi III and muddy littoral sediments; the deepest records are and IV each with 3 dorsal setae, 1–2 ventral setae, and from almost 450–770 m. 1–2(–3) parambulacral setae. Remarks. Easily identified on the base of its spatula- Large, smooth median claw of tarsus I flanked by shaped or wide and lamellar rostrum and the two large scythe-shaped or almost setiform paired claws. Tarsi spines at the end of the palps. II–IV with large paired claws; minute central sclerite References. Abé (1990), Abé and Green (1994), without or with small claw-like process. Paired claws Otto (2000b). generally with accessory process and pecten. Pecten of Simognathus Trouessart, 1889 (Fig. 55) tarsus IV often dissimilar from that of tarsi II and III. Diagnosis. Idiosoma: Length 180–560 µm. Dorsal and Biology and distribution. One larval and two ventral plates strongly sclerotized; parts of plates may nymphal stages occur during ontogeny. More than have a dark-brown pigmentation. Integument of large 40 species are described. Simognathus is found in AD and PD generally foveate or porose. OC distinctly intertidal and subtidal areas, but never in high numbers; smaller than AD and PD, its shape either distinct, the deepest record is from a depth of about 300 m.

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The genus is cosmopolitan but much more species tip of rostrum. P-2 with 1 distodorsal seta, P-3 with are recorded from the southern than from the northern 1 dorsomedial seta, P-4 with 3 setae in basal whorl, 1 hemisphere. seta midway. Claws of chelicerae with heavy hooks. Remarks. Simognathus is most similar to Legs: Shape of leg I similar to that of following Acaromantis. In Acaromantis the very short tarsus legs. Genua much shorter than adjoining segments. I bears a single claw, the palps are 2-segmented, and Basifemora I to IV with 2,3,2,2 setae. Each of tibiae the OC are always reduced to small sclerites which are with a pair of short ventral bristle-like setae. Tarsi hidden beneath the striated integument. with large membranes of claw fossa. Tarsus I with 3 References. Bartsch (1994b, 2003c), Otto (2000a). dorsal setae and dorsolateral solenidion; ventrally Spongihalacarus Otto, 2000 (Fig. 56) with 1 long seta and 8 eupathidia (parambulacral setae excluded). Tarsus II with 3 dorsal setae, a solenidion Diagnosis. Idiosoma: Length 340 µm. AD, OC and PD on dorsomedial membrane of claw fossa and 3 ventral smooth. OC with 2 pairs of gland pores. Dorsum with 6 eupathid setae. Tarsi III and IV each with 3 dorsal and 0 pairs of setae; ds-4 and ds-5 within striated integument; ventral setae. Each tarsus with a pair of parambulacral adanal setae on anal plate. AE with 3 pairs of setae and setae. 1 pair of epimeral pores. PE with 1 dorsal and 3 ventral Paired claws large; pectines with conspicuous tines. setae. Female GA short, with 4–5 pairs of perigenital Median claw present but small. setae and 2 pairs of subgenital setae. Biology and distribution. With a free-living Gnathosoma: Short; with 2 pairs of maxillary deutonymph. A single species is described which was setae. Rostrum triangular. Palps reduced to 2–3 setae in collected on the west coast of North America. dorsolateral position relative to rostrum. Remarks. Thalassacarus resembles species of the Legs: Genua I and II shorter than telofemora and genus Halacarellus. The most marked difference is the tibiae of these legs. Genua III and IV almost as long form of the chelicerae; heavy hooks as in Thalassacarus as telofemora. Leg segments dorsally with short setae. are not mentioned in any of the Halacarellus species. Basifemora I–IV with 2 setae each. Genua and tibiae The ventral plates of Thalassacarus bear porose panels, with pectinate ventral spurs. Tibiae I–IV with 3,3,3,2 in contrast, these plates of Halacarellus species are such spurs. Tarsi I–IV with 4,4,4,3 dorsal setae (solenidia uniformly and delicately punctate. Agaue demonstrates included) and 1,1,0,0 ventral setae. Solenidion on a slight overall resemblance but its ventral plates bear tarsus I in dorsolateral, that on tarsus II in dorsomedial no porose panels. position. All tarsi with pair of parambulacral setae. References. Newell (1949). Tarsi end with large median claw and slightly smaller paired claws. Thalassarachna Packard, 1871 (Fig. 58) Biology and distribution. The single species known Diagnosis. Idiosoma: Generally large, 400–1200 µm was found within an alga-sponge association, collected long. AD and PD present; OC rarely lacking. In a few in shallow waters in the Great Barrier Reef Marine species PD of male larger than that of female. Dorsal Park, northeastern Australia. plates faintly reticulated, not prominently sculptured. Remarks. The most unique character of Dorsum with 6 pairs of idiosomatic setae; adanal setae Spongihalacarus is the absence of palpal segments. on anal plate. Idiosoma generally with 4 pairs of gland References. Otto (2000e). pores; 2nd pair of pores, if present, marginally within Thalassacarus Newell, 1949 (Fig. 57) striated integument. AE with 3 pairs of ventral setae. Diagnosis. Idiosoma: Length 340–380 µm. Dorsal PE with 1 dorsal seta; ventrally either with 3 setae, and ventral plates large, dorsal plates foveate, ventral or with 2 setae and 1 pair of setae within striated plates with porose panels, marginal ornamentation integument. Female GA with 3–5 pairs of perigenital resembling rosette pores. OC elongate. Dorsum with setae and 3–5 pairs of subgenital setae. Male GA with 6 pairs of idiosomatic setae; adanal setae on ventral 40–160 perigenital setae and 4–6 pairs of subgenital side of anal plate. AE with 3 pairs of setae. PE with setae. Internal genital acetabula often large. 1 dorsal and 3 ventral setae. Female GA with 3 pairs Gnathosoma: Longer than wide. Rostrum in ventral of perigenital setae; subgenital setae absent. Male with aspect triangular or elongate; generally with 2 (rarely approximately 50 perigenital setae, arranged in a ring up to 5) pairs of maxillary setae, 1 pair on gnathosomal around GO, and 4(–5?) pairs of subgenital setae. base, 1 pair on rostrum. Palps 4-segmented, lateral to Gnathosoma: Rostrum elongate, about as long gnathosoma and extending beyond rostrum. P-2 with as gnathosomal base. One pair of maxillary setae distodorsal seta. P-3 with medial spine. P-4 with 3 on gnathosomal base, 1 pair on rostrum. Palps 4- setae in basal whorl. segmented, attached laterally and extending beyond

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Legs: Genua distinctly shorter than telofemora or Remarks. A similar combination of setation of palps tibiae. Leg I longer than leg II. In a few species leg and tarsi is known in Camactognathus but species of I equipped with long spines, namely up to 5 spines the latter genus have three pairs of setae on the AE and on telofemur, 2 on genu, and 6 on tibia. Basifemora four ventral setae on tibia I. I to IV with 2,2–3,2–3,2–3 setae. Tarsus I with 5–8 The only Thalassophthirius species described has dorsal setae, 1 setiform dorsolateral solenidion, 1 very long and robust dorsal setae directed backwards ventromedial seta or spine, and 8–19 eupathidia (pair and the PD has a large median and two smaller lateral of parambulacral setae included). Tarsus II with 4–9 cavities. Similar enlarged setae and cavities have been dorsal setae, dorsomedial solenidion, and 5–16 ventral mentioned in the descriptions of a few Copidognathus setae (pair of parambulacral setae included). Tarsi III species. and IV with 3–7 and 3–6 dorsal setae, respectively, 0–2 References. Bartsch (1988d). ventral setae and pair of parambulacral setae. Tropihalacarus Otto & Bartsch, 1999 (Fig. 60) Paired claws large, with accessory process and pecten. Median claw much smaller, bidentate. Diagnosis. Idiosoma: Slender 500–650 µm long. Dorsum with AD, OC and PD, 6 pairs of dorsal Biology and distribution. With one larval and two idiosomatic setae; adanal setae on anal cone. OC with 2 nymphal stages (except for one species which has no gland pores, AD and PD each with 1 pair of gland pores. deutonymph). Fourteen species are presently described, Venter with AE, PE and GA. AE with 3 pairs of setae; recorded from the North Atlantic and Arctic Ocean. PE with 1 dorsal and 3 ventral setae. Female GA with Thalassarachna species are generally epibiontic and 3 pairs of perigenital setae, genital sclerites without inhabit subtidal habitats. The two species recorded subgenital setae. Male GA with 30–100 perigenital from the deep-sea have greatly reduced OC. setae, each genital sclerite with 5 subgenital setae. Remarks. The Thalassarachna species are separated Gnathosoma: Elongate. Rostrum parallel-sided, from Halacarellus on the basis of the enlarged number shorter than gnathosomal base. Basal pair of maxillary of dorsal setae on the tarsi I and II and the pair of gland setae either on gnathosomal base or on rostrum; second pores in the marginal striated integument. pair of setae on rostrum. Palps 4-segmented, attached References. Bartsch (1997a, 2001c). laterally. P-2 with 1 dorsal seta. P-3 with very minute Thalassophthirius Bartsch, 1988 (Fig. 59) medial seta. P-4 with 3 setae in basal whorl. Diagnosis. Idiosoma: Length 210 µm. Dorsal and Legs. Slender. Genua shorter than adjoining ventral plates large. Dorsum with 5 pairs of setae; ds-3, segments. Basifemora I–IV with 2 setae each. Tibiae ds-4 and ds-5 very long, directed backwards. Adanal with 4,3,3,2 ventral setae; ventromedial setae of setae on anal plates. Gland pores small, inconspicuous. tibiae II and III bipectinate. Tarsus I with 1 ventral AE with 2 pairs of ventral setae, PE with 1 lateral (ventromedial) seta, its apex with numerous eupathidia. and 3 ventral setae. Male GA with approximately 75 Tarsus II with 1–2 ventral setae, tarsi III and IV with perigenital setae and 5–6 pairs of subgenital setae. 0–2 ventral setae each. Dorsal setae on tarsi I–IV numbering 4,4,3,3 (solenidia included). Solenidion of Gnathosoma: Slender; rostrum about as long as tarsus I and II on dorsolateral and dorsomedial fossa gnathosomal base. One pair of maxillary setae close to membrane, respectively. Tarsi I–IV each with pair of base of rostrum, 1 pair close to end of rostrum. Palps parambulacral setae. lateral to gnathosoma, 4-segmented and extending Paired claws large; median claw inconspicuous. beyond tip of rostrum. P-2 with 1 distodorsal seta; no Biology and distribution. Two species are known, seta on P-3. P-4 with 3 setae in basal whorl. both have been extracted from Pacific shallow water Legs: Leg I longer than following legs. Genua shorter sediments. than adjoining segments. Basifemora I to IV with 1 seta Remarks. A gnathosoma similar to that of each. Tibiae I–IV with 2 ventral setae each. Tarsus I Tropihalacarus and tarsi I with numerous eupathidia with 3 dorsal setae, dorsolateral solenidion, pair of are present also in species of the genera Agaue, small ventral setae (exclusive of parambulacral setae). Bathyhalacarus, Halacarellus, Thalassacarus, and Tarsus II with 3 dorsal setae, dorsomedial solenidion Thalassarachna, but these species have no bipectinate and 1 small ventral seta. Tarsi III and IV each with 3 setae on tibiae II and III as present in Tropihalacarus. dorsal but no ventral setae. Tip of all tarsi with pair of References. Otto and Bartsch (1999). parambulacral setae. Paired claws large; median claw small. Werthella Lohmann, 1907 (Fig. 61) Biology and distribution. One species is described, Diagnosis. Idiosoma: Wide; length 410–560 µm. it has been collected on the shores of southeastern part Dorsal and ventral plates present. Dorsal plates of South America. panelled, with raised porose areas; AD often with 2

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 37 porose areolae in middle of plate, these may be fused. of setae. PE with 1 dorsal and 3 ventral setae. Female PD with longitudinal costae. Gland pores small. GA with almost 10 pairs of perigenital setae and 0–1 Dorsum with 6 pairs of idiosomatic setae. Adanal subgenital setae. Male GA large; genital opening small setae on either side of anal sclerites. AE with 3 pairs of and surrounded by approximately 90 perigenital setae; ventral setae and pair of generally large epimeral pores; genital sclerites with 4–5 pairs of subgenital setae. these pores surrounded by numerous tines. PE with Gnathosoma: Rostrum parallel-sided; somewhat 1 dorsal and 3 ventral setae. Females with 3 pairs of shorter than gnathosomal base. Maxillary setae small, perigenital setae and 1 pair of subgenital setae. Males 1 pair on gnathosomal base, 1 pair in basal portion of with approximately 30–40 perigenital setae arranged in rostrum. Tip of rostrum with a pair of barbs. Palps 4- a ring close to GO, and 4–5(–6?) pairs of subgenital segmented; passing beyond rostrum. P-2 with dorsal setae. seta. No seta on P-3. P-4 with 1 seta, 1 setula and 2 Gnathosoma: Short, somewhat longer than wide. spurs. Rostrum short, triangular, pointed. Tectum often scale- Legs: Slender. Genua distinctly shorter than like. One pair of maxillary setae on gnathosomal telofemora and tibiae. Basifemur I to IV with 2,3,3,3 base, 1 pair on rostrum. Palps 4-segmented, lateral to setae. Tibiae I and II with 6–7 ventral bristles each, gnathosoma, slightly surpassing rostrum. P-2 with 1 tibiae III and IV with 4–5 ventral bristles. Tarsi with distal seta. P-3 short, without seta. P-4 short; with 1 large fossa membranes. Tarsi I and II each with basal seta, apically with setula and 2 spurs. solenidion on dorsolateral fossa membrane. Tarsus I Legs: Legs either slender, with elongate telofemora with 3 dorsal setae (solenidion excluded) and 7–8 pairs and tibiae, or with short segments, the telofemora of ventral eupathidia but no ventromedial seta distanced bearing wide ventral lamellae. Genua much shorter than from eupathidia. Tarsi II–IV with 3,3,3 dorsal setae adjoining segments. Basifemora I–IV with 2(–3?),2,2,2 (solenidia excluded) and 1,0,0 ventral setae. Tip of all setae. Tibiae I and II with 2–3 ventral bristle-like setae, tarsi with pair of parambulacral setae. tibiae III and IV with 2 ventral setae. Tarsus I with 3 Paired claws large; median claw small. dorsal setae, setiform dorsolateral solenidion, 1–3 Biology and distribution. With free-living ventral setae, and pair of parambulacral setae. Tarsus deutonymph. One species is described which was taken II with 3 dorsal setae, dorsolateral solenidion, 0 ventral in the Indian Ocean, off Réunion, at a depth of 1000 setae and parambulacral setae. Tarsi III and IV with 4 m. and 3 dorsal setae, respectively, 0 ventral setae and pair Remarks. A single pair of barbs on the tip of of parambulacral setae. rostrum, as present in Werthelloides, may be found in Paired claws large, smooth or with accessory process, Agaue species. But in contrast to Werthelloides, species rarely with pecten. Median claw present but small. of Agaue have 3 setae in the basal whorl of P-4, the Biology and distribution. A larva and one nymphal maxillary setae stand close together, and the ds-3 are stage, the protonymph, are present during development. not situated in the posterior half of the OC. Ten species are described. Werthella is known from References. Bartsch (1986c). the southern hemisphere, here the genus inhabits both intertidal and abyssal areas. Winlundia Newell, 1984 (Fig. 63) Remarks. Werthella is similar to Copidognathides. Diagnosis. Idiosoma: Length 300–350 µm. Dorsal and The epimeral pores in Werthella are larger than in ventral plates large. Dorsum with 6 pairs of idiosomatic Copidognathides, the rostrum pointed, the perigenital setae; adanal setae on anal plate. Anterior gland pores setae on the male GA are arranged in a ring around present though not very conspicuous. AE with 3 pairs the GO. There is an overall similarity with Pelacarus, of ventral setae. PE with 1 dorsal and 3 ventral setae. but in the latter genus tarsus II has the solenidion in Female GA with 3 pairs of perigenital setae and 2 pairs dorsomedial position, males have the perigenital setae of subgenital setae. Males with 20–40 perigenital setae not in a ring close to the GO, and females bear three and 3–5 pairs of subgenital setae. pairs of subgenital setae. Gnathosoma: Rostrum elongate. One pair of References. Newell (1971), Bartsch (1996c). maxillary setae inserted on gnathosomal base, adjacent to rostrum, 1 pair on rostrum. Palps attached laterally, Werthelloides Bartsch, 1986 (Fig. 62) 4-segmented, extending beyond rostrum. P-2 with 1 Diagnosis. Idiosoma: Length 725 µm. Dorsal plates distal seta; no seta on P-3; P-4 with 3 setae in basal AD, OC and PD separated by large areas of striated whorl. integument. Dorsum with 6 pairs of idiosomatic setae. Legs: Genua shorter than adjoining segments. Pair of ds-3 in posterior portion of OC, adanal setae Basifemora with 2,2,2,2 setae. Tibiae I–IV with 4,3,2,2 on PD. Gland pores inconspicuous. AE with 3 pairs ventral setae. Ventrolateral setae of tibiae II–IV smooth,

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 38 ventromedial setae of tibia II and III bipectinate, that coral sand in the Queensland Plateau, off northeastern seta of tibia IV either smooth or bipectinate. Tarsus Australia. I with 3 dorsal setae, dorsolateral solenidion and 2 Remarks. Xenohalacarus and Scaptognathides are ventral setae (1 slender and 1 eupathid). Tarsus II with the only marine halacarid genera with enlarged tines on 3 dorsal setae, dorsomedial solenidion but no ventral the claws of tarsi I, tines which are much longer than setae. Tarsi III and IV each with 3 dorsal and 0 ventral on the claws of the following legs. setae. All tarsi with pair of parambulacral setae. References. Otto (2000f). Paired claws large, each with an accessory process. Median claw present though minute. References Biology and distribution. A free-living deutonymph Abé, H., 1990. Two new species of the genus Scaptognathus present. Two species are described, both collected on (Acari: Halacaridae) from the Sea of Japan. Cah. Biol. the west coast of South America, in tidal sediment. mar. 31, 349-363. Remarks. Winlundia is most similar to Arhodeoporus; Abé, H., 1991. A new genus and species of the family a difference is that in general tarsus I of Arhodeoporus Halacaridae (Acari, Prostigmata) from Japan. Zool. Jb. species bears three ventral setae, namely one slender (Syst.) 118, 247-256. Abé, H., 1996a. Rhombognathine mites (Acari : and two eupathid ones, whereas in Winlundia one of Halacaridae) from Hokkaido, northern Japan. Publ. Seto the eupathid setae is reduced. Tropihalacarus differs Mar. Biol. Lab. 37, 63-166. from Winlundia by its large number of eupathidia on Abé, H., 1996b. A new species of the genus tarsus I and the very long OC. Anomalohalacarus (Acari: Halacaridae) from Japan with References. Newell (1984). notes on taxonomic characters. J. Acarol. Soc. Jpn 5, 7-16. Xenohalacarus Otto, 2000 (Fig. 64) Abé, H., 1997. Halacarid mites of the genus Actacarus Diagnosis. Idiosoma: Length 355–360 µm. AD and (Acari: Halacaridae) from Hokkaido, northern Japan. PD large. OC small, rounded. Dorsum with 6 pairs of Species Diversity 2, 31-42. dorsal setae. OC and PD each with 2 pairs of gland Abé, H., 1998. Rhombognathine Mites. Taxonomy, pores. AE with epimeral pores and 3 pairs of ventral Phylogeny, and Biogeography. Hokkaido University Press, Sapporo, 219 pp. setae. PE with 1 dorsal and 2 ventral setae; 1 pair of Abé, H., 2001. Phylogeny and character evolution of the ventral setae within striated integument. Female GA marine mite genus Isobactrus (Acari : Halacaridae). J. with 4 pairs of perigenital setae, no subgenital setae. Nat. Hist. 35, 617-625. Male GA with outlying perigenital setae and about 50 Abé, H., Green, J., 1994. A new species of the genus perigenital setae close around GO; genital sclerites Scaptognathus (Acari: Halacaridae) from Tasmania. Acta with 5 pairs of subgenital setae. arachnol. 43, 169-178. Gnathosoma: Rostrum slender, parallel-sided, Angelier, E., 1954. Halacariens des sables littoraux longer than gnathosomal base. One pair of maxillary méditerranéens. Vie Milieu 4, 281-289. setae on gnathosomal base, 1 pair in apical end of Bartsch, I., 1972. Ein Beitrag zur Systematik, Biologie und Ökologie der Halacaridae (Acari) aus dem Litoral rostrum. Palps 4-segmented, attached lateral to rostrum. der Nord- und Ostsee. I. Systematik und Biologie. Abh. P-2 with 2 setae. P-3 with short median seta. P-4 with Verh. Naturw. Ver. Hamburg (N.F.) 16, 155-230. 6 setae. Bartsch, I., 1973. Halacaridae (Acari) von der Josephine Legs: Genua of all legs shorter than adjoining Bank und der Großen Meteorbank aus dem segments. Basifemora I–IV with 2,2,2,1 setae Tibiae östlichen Nordatlantik. II. Die Halacaridae aus den with bristle-like ventral setae, tibiae I and II with Bodengreiferproben. Meteor Forsch.-Ergebn., Reihe D 4 such setae. Tarsi I–IV with 4,4,4,3 dorsal setae 15: 51-78. (solenidion included), and 2,2,1,2 bristle-like ventral Bartsch, I., 1974. Ein Beitrag zur Systematik, Biologie setae. Solenidion on tarsus I in dorsolateral, on tarsus und Ökologie der Halacaridae (Acari) aus dem Litoral II in dorsomedial position. Tarsi I and II each with der Nord- und Ostsee. II. Ökologische Analyse der Halacaridenfauna. Abh. Verh. Naturw. Ver. Hamburg pair of parambulacral setae; tarsus III with medial (N.F.) 17, 9-53. parambulacral seta only; no parambulacral setae on Bartsch, I., 1976. Copidognathides minutirostris n. g., n. tarsus IV. sp., eine psammophile Halacaride (Halacaridae, Acari). Paired claws on leg I with long strong tines. Claw Cah. Biol. mar. 17, 237-241. pectines on following tarsi with delicate tines. Median Bartsch, I., 1977. Interstitielle Fauna von Galapagos. XX. claw present but small. Halacaridae (Acari). Mikrofauna Meeresboden 65, 1- Biology and distribution. With a free-living 108. deutonymphal stage. At present known by a single Bartsch, I., 1978. Halacaridae (Acari) von Gezeitenstränden species which had been extracted from shallow water Nordnorwegens. Mikrofauna Meeresboden 70, 1-22.

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Bartsch, I., 1979. Halacaridae (Acari) von der Atlantikküste Bartsch, I., 1992b. Phacacarus flavellus gen. et spec. Nordamerikas. Beschreibung der Arten. Mikrofauna nov. (Copidognathinae, Halacaroidea, Acari), eine Meeresboden 79, 1-62. Meeresmilbe auf Kalkalgen. Zool. Anz. 228, 212-219. Bartsch, I., 1981a. Fünf neue Arten der Gattung Halacarus Bartsch, I., 1992c. Two new species of the genus (Acari, Halacaridae) aus dem Atlantik. Zool. Scr. 10, Bradyagaue (Halacaridae, Acari) from the southern 203-215. Indian Ocean. Cah. Biol. mar. 33, 433-440. Bartsch, I., 1981b. Die Gattung Anomalohalacarus und Bartsch, I., 1993a. Synopsis of the Antarctic Halacaroidea Halacaroides (Halacaridae, Acari), geographische (Acari). Synopses of the Antarctic Benthos. Vol. 4. 176 Verbreitung, Bestimmungstabelle und Beschreibung pp., Koeltz, Koenigstein. dreier neuer Arten. Zool. Beitr. 27, 67-84. Bartsch, I., 1993b. A new species of Australacarus Bartsch, I., 1982. Zur Gattung Bathyhalacarus (Acari, (Halacaridae, Acari) from southwestern Australia. Zool. Halacaridae), nebst Beschreibung fünf neuer Arten. Zool. Jb. (Syst.) 120, 65-70. Scr. 11, 209-220. Bartsch, I., 1994a. Sexualdimorphismus bei Meeresmilben Bartsch, I., 1983: Zur Systematik und Verbreitung der (Halacaridae, Acari). Übersicht und Beschreibung des Gattung Arhodeoporus (Halacaridae, Acari) und Männchens von Phacacarus flavellus. Zool. Anz. 232, Beschreibung zweier neuer Arten. Zool. Beitr. N.F. 28, 61-74. 1-26. Bartsch, I., 1994b. The genus Simognathus (Acari : Bartsch, I., 1986a. A new species of Halixodes Halacaridae), description of six new species from (Halacaridae, Acari) and a review of the New Zealand southern Australia and a tabular key to all species. species. J. R. Soc. N. Z. 16, 51-56. Acarologia 35, 135-152 Bartsch, I., 1986b. Zur Gattung Agauopsis (Acari, Bartsch, I., 1994c. Copidognathus (Halacaridae: Acari) Halacaridae), Beschreibung zweier Arten und Übersicht from western Australia. Description of twelve species of über Verwandtschaftsgruppen. Zool. Scr. 15, 165-174. the gibbus group. Rec. West. Aust. Mus. 16, 535-566. Bartsch, I., 1986c. Lohmannellinae (Halacaroidae, Acari) Bartsch, I., 1996a. New records of Actacarus from the aus dem Mittelmeer. Ent. Mitt. Zool. Mus. Hamburg 8, Caribbean area and notes on the subfamily Actacarinae 231-244. and its species (Arachnida: Acari: Halacaridae). Bartsch, I., 1986d. Zur Gattung Werthella Lohmann, Senckenberg. biol. 75, 229-241. Pelacarus n. gen. und Werthelloides n. gen. (Halacaridae, Bartsch, I., 1996b. Halacarines (Acari: Halacaridae) from Acari). Cah. Biol. mar. 27, 211-223. Rottnest Island, Western Autralia: the genera Agauopsis Bartsch, I., 1987. Australacarus inexpectatus gen. et spec. Viets and Halacaropsis gen. nov. Rec. West. Austr. Mus. nov. (Halacaridae, Acari), mit einer Übersicht über 18, 1-18. parasitisch lebende Halacariden. Zool. Anz. 218, 17-24. Bartsch, I., 1996c. Werthella ampliata n. sp., a new Bartsch, I., 1988a. Halacaroidea, in: R. P. Higgins, Thiel, H. psammophilous halacarid mite (Acari: Halacaridae: (Eds.), Introduction to the study of Meiofauna. Chapter Copidognathinae) from Western Australia. Acarologia 44, 417-422. 37, 275-280. Bartsch, I., 1988b. Halacariden (Acari) im Nordatlantik. Bartsch, I., 1996d. Two new species of Scaptognathides Beschreibungen von Halacarus balgimus sp. n. und from the Caribbean Sea (Arachnida: Acari: Halacaridae). Agauides cryosi gen. et sp. n. Cah. Biol. mar. 29, 353- Senckenberg. biol. 76, 145-151. 359. Bartsch, I., 1997a. Thalassarachna and Halacarellus Bartsch, I., 1988c. Arenicolous (Halacaridae, Acari) in (Halacaridae: Acari): two separate genera. J. nat. Hist. Hawaiian waters. Proc. Hawaii. Entomol. Soc. 28, 213- 31, 1223-1236. 228. Bartsch, I., 1997b. Copidognathinae (Halacaridae, Acari) Bartsch, I., 1988d. Thalassophthirius auster gen. et spec. from northern Australia; description of four new species, nov., a halacarid mite (Acari) suspected of being a in: Hanley, J.R., Caswell, G., Megirian, D., Larson, H.K. parasite. Polar Res. 6, 181-184. (Eds.), Proceedings of the Sixth International Biological Bartsch, I., 1989. Deep-sea mites (Halacaridae, Acari), from Workshop. The Marine Fflora and Fauna of Darwin the southwestern Pacific. Cah. Biol. mar. 30, 455-471. Harbour, Northern Territory, Australia, Museum and Art Bartsch, I., 1990a. Acarothrix palustris gen. et spec. nov. Gallery of the Northern Territory, Darwin, pp. 231–243. (Halacaroidea, Acari), ein Bewohner der Salzwiesen Bartsch, I., 1997c. Arhodeoporus (Acari: Halacaridae) Südchinas. Zool. Anz. 224, 204-210. from Rottnest Island, description of three new species. Bartsch, I., 1990b. Antarctic Halacaroidea (Acari): Genera Acarologia 38, 265-274. Agaue, Bradyagaue, and Halacarellus. Antarct. Res. Ser. Bartsch, I., 1998a. Colobocerasides koehleri (Trouessart) 52, 185-217. und C. auster n. sp. (Arachnida: Acari: Halacaridae), Bartsch, I., 1991. Taxonomic notes on halacarids (Acari) Beschreibung der Arten. Mitt. Mus. Naturkd. Berl., Zool. from the Skagerrak area. Helgoländer Meeresunters. 45, Reihe 74, 225-232. 97-106. Bartsch, I., 1998b. Halacarinae (Acari, Halacaroidea) from Bartsch, I., 1992a. Mictognathus secundus, a the northwestern Black Sea: a review. Mitt. Hamb. Zool. psammophilous halacarid mite (Acari : Halacaridae). Mus. Inst. 95, 143-178. Acarologia 33, 85-89. Bartsch, I., 1998c. A new species of the Copidognathus pulcher group (Acari: Halacaridae) from Western

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Australia: Description of adults and juveniles and notes Baster, J., 1758. Observationes de Corrallinis, iisque on developmental pattern. Species Diversity 3, 187-200. infidentibus polypis, aliisque animalculis marinis. Phil. Bartsch, I., 1999a. Peregrinacarus reticulatus gen. Trans. R. Soc., London 50, 258-279. nov. spec. nov., a freshwater halacarid mite (Acari, Crowe, J.H., Camara, C.G., 1973. Studies on acarine Halacaridae) from Marion Island. Hydrobiologia 392, cuticles—I, Cuticular pores in a marine mite. Comp. 225-232. Biochem. Physiol. 45A, 757-766. Bartsch, I., 1999b. Copidognathus (Halacaridae: Acari) Gosse, P.H., 1855. Notes on some new or little-known from Western Australia: five species of the oculatus marine animals (II). Ann. Mag. Nat. Hist. 16 (91), 27–36. group. Rec. West. Austr. Mus. 19, 299-321. Green, J.M., MacQuitty, M., 1987. Halacarid mites. Bartsch, I., 1999c. First record of Copidognathides from the Synopses Br. Fauna (N.S.) 36, 178 pp. Black Sea (Copidognathinae, Halacaridae, Acari). Ent. Kirchner, W.-P., 1969. Zur Biologie und Ökologie von Mitt. Zool. Mus. Hamburg 13: 139-145. Halacarus basteri basteri Johnson 1836 (Acari, Bartsch, I., 1999d. Halacaridae (Acari) from Rottnest Trombidiformes). Oecologia (Berl.) 3, 56-69. Island: Description of two Agaue species. Acarologia 40, Krantz, G.W., 1970. Agauopsis vidae, a new species of 179-190. Halacaridae (Acari: Prostigmata) from the northern Bartsch, I., 2000. Rhombognathinae (Acari: Halacaridae) Adriatic Sea, with notes on its behavior. Arch. Oceanogr. from the Great Barrier Reef, Australia. Mems Qld. Mus. Limnol. 16, 247-261. 45, 165-203. Laubier, L., 1960. Parhalixodes travei n. g., n. sp., un Bartsch, I., 2001a. A new halacarid genus (Acari: nouvel Halixodinae (Halacariens) ectoparasite de Halacaridae: Halacarinae) from the Great Meteor nemerte en Méditerranée occidentale. Acarologia 2, Seamount, Eastern North Atlantic. Species Diversity 6, 541-551. 117-125. Lohmann, H., 1889. Die Unterfamilie der Halacaridae Murr. Bartsch, I. 2001b. A new freshwater halacarid mite, genus und die Meeresmilben der Ostsee. Zool. Jb. (Syst.) 4, Peregrinacarus (Halacaridae, Acari) from the Falklands. 269-408. Hydrobiologia 452, 139-144: Lohmann, H., 1893. Die Halacarinen der Plankton- Bartsch, I., 2001c. Halacarus Gosse, 1855, H. ctenopus Expedition. Ergebn. Atlant. Ozean Planktonexped. Gosse, 1855 and Thalassarachna Packard, 1871 Humboldt. Stift. 2, 11-95. (Arachnida, Acari): proposed conservation of usage of MacQuitty, M., 1984. The feeding behaviour of two species the name by designation of a neotype for H. ctenopus. of Agauopsis (Halacaroidea) from California, in: D.A. Bull. Zool. Nomencl. 58, 202-205. Griffith, C.E. Bowman (Eds.), Acarology VI, John Wiley, Bartsch, I., 2002. Halacarids from the Great Meteor New York, pp. 571-580. Seamount (Northeastern Atlantic). Description of new Makarova, N.G., 1978. Marine mites (Acarina, Halacaridae) species of Agauopsis, Atelopsalis and Halacarus and from the intertidal zone of the Gulf of Anadyr (Bering redescription of H. spiniger Bartsch (Arachnida: Acari: Sea), in: Kussakin, O.G. (Ed.), The intertidal zone of the Halacaridae). Mitt. Hamb. Zool. Mus. Inst. 99, 29-45. Bering Sea and south-eastern Kamchatka. pp. 131-149. Bartsch, I., 2003a. Mangrove halacarid fauna (Halacaridae, (In Russian, with English Summary) Acari) of the Dampier region, Western Australia, with Monniot, F., 1962. Description d’une nouvelle espèce description of five new species. J. Nat. Hist. 37, 1855- d’acariens marins, Halacaridae: Coloboceras drachi, 1877. récoltée en Méditerranée. Bull. Soc. Zool. Fr. 87, 492- Bartsch, I., 2003b. The subfamily Rhombognathinae: 497. developmental pattern and re-evaluation of the Monniot, F., 1972. Scaptognathides, un nouveau genre phylogeny (Arachnida, Acari, Halacaridae). d’acariens marins (Halacaridae) dans l’Atlantique ouest. Senckenberg. biol. 82, 15-57. Acarologia 13, 361-366. Bartsch, I., 2003c. Psammophilous halacarids (Halacaridae: Morselli, I., Mari, M., (1982). Alacaridi (Acari, Acari) from Dampier, Western Australia. Description Prostigmata) di fondi sabbiosi della costa Ionica del of species and faunal comparison of the mesopsammal Salento. Atti Soc. Tosc. Sci. nat., Mem. (B) 88, 229-247. halacarid fauna of western and eastern Australia. Rec. Morselli, I., Mari, M., Sarto, M., 1998. On three species West. Aust. Mus. 22, 23-45. of the genus Acarochelopodia Angelier, 1954 (Acari, Bartsch, I., 2003d. Lohmannellinae (Halacaridae: Acari) Halacaroidea) from the Italian coasts. Ital. J. Zool. 65, from the Great Meteor Seamount (Northeastern 381–384. Atlantic). Description of new species and reflections Murray, A., 1877. Economic Entomology. Aptera. South on the origin of the seamount fauna. Mitt. Hamb. Zool. Kensington Museum Handbooks, 433 pp. Mus. Inst. 100, 101-117 Newell, I.M., 1947. A systematic and ecological study Bartsch, I., 2004a. Bradyagaue from Western Australia, of the Halacaridae of eastern North America. Bull. description of a new species (Acari, Halacaridae). Cah. Bingham Oceanogr. Coll. 10, 1-232. Biol. mar. 45, 65-69. Newell, I.M., 1949. New genera and species of Halacaridae Bartsch, I., 2004b. Acarothrix ampliata (Acari: Halacaridae: (Acari). Am. Mus. Novitat. 1411, 1–22. Copidognathinae), a new halacarid mite from Florida, Newell, I.M., 1967. Abyssal Halacaridae (Acari) from the with notes on external genital acetabula. Species southeast Pacific. Pacif. Insects 9, 693-708. Diversity 9, 259-267.

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Newell, I.M., 1971. Halacaridae (Acari) collected during Otto, J., 2000h. Six closely related species of the cruise 17 of the R/V Anton Bruun, in the southeastern Copidognathus gibbus group (Acarina: Halacaridae) Pacific Ocean. Anton Bruun Rep. 8, 3–58. from north-eastern Australia. Cah. Biol. mar. 41, 223- Newell, I.M., 1984. Antarctic Halacaroidea. Antarct. Res. 232. Ser. 40, 1-284. Otto, J.C., 2001a. A new species of Mictognathus (Acari: Otto, J.C., 1999a. Halacarid fauna of the Great Barrier Reef Halacaridae) from the Great Barrier Reef. Pac. Sci. 55, and Coral Sea: the genera Agauopsis and Halacaropsis 43-46. (Acarina: Halacaridae). Mems Qld. Mus. 43, 797-817. Otto, J.C., 2001b. Halacaridae of the Great Barrier Reef Otto, J.C., 1999b. Four new species of Agaue (Acarina: Lagoon and Coral Sea: Halacarellus and Halacarus. Halacaridae) from the Great Barrier Reef Marine Park. (Acarina: Halacaroidea). Mems Qld. Mus. 46, 691-716. Cah. Biol. mar. 40, 273-281. Otto, J.C., Bartsch, I., 1999. Tropihalacarus spio, a new Otto, J.C., 1999c. Corallihalacarus chilcottensis, a new genus and species of Halacaridae (Acarina: Prostigmata) genus and species of marine mites from the Coral Sea from the Great Barrier Reef. Acarologia 40, 171-178. (Acarina: Halacaridae). Zool. Sci. 16, 839-843. Proches, S., 2001. Halacaropsis praecognita (Acari: Otto, J.C., 2000a. Simognathinae (Acarina: Halacaridae) Halacaridae) from southern Africa. Trans. R. Soc. S. Afr. from the Great Barrier Reef and Coral Sea, description 56, 41-43. of thirteen new species. Mems Qld. Mus. 45, 505-534 Proches, S., 2002. New species of Copidognathinae (Acari: Otto, J.C., 2000b. Halacaridae from the Great Barrier Reef Halacaridae) from southern Africa. J. Nat. Hist. 36, 999- and Coral Sea: the genera Lohmannella, Scaptognathides 1007. and Scaptognathus (Acarina: Halacaridae: Siemer, F., 1996. Untersuchungen zur Verteilung, zur Lohmannellinae). Mems Qld. Mus. 45, 535-555 Biologie und zum Lebenszyklus mariner Halacaridae Otto, J.C., 2000c. Acarochelopodia and Actacarus (Acari: (Prostigmata: Acari) im ästuarinen Felslitoral. Unpubl. Halacaridae) from northern Australia, with remarks on dissert., Universität Bremen, Germany; 165 pp. A. pacificus and A. orthotectus. Species Diversity 5, Sokolov, I.I., Yankovskaya, A.I., 1968. Perwyi abissal’nyi 111-127. predstavitel’ Halacaridae (Acari) iz raina Kurilo- Otto, J.C., 2000d. Australacarus (Acari: Halacaridae) from Kamcatskoi wpadiny. Dokl. Akad. Nauk SSSR 179, northern Australia, with description of three new species. 486-488. Rec. Aust. Mus. 20, 103-114. Straarup, J.-O., 1968. On the life cycles of halacarids Otto, J.C., 2000e. Spongihalacarus longiscutatus n.gen., (Acari) from the Öresund. Ophelia 5, 255-271. n.sp., a marine mite (Acari: Prostigmata: Halacaridae) Viets, K., 1928. Wassermilben aus dem Schwarzen Meer, associated with an alga-sponge symbiosis from the Great dem Kaspischen Meer und dem Aral-See. Abh. Naturw. Barrier Reef Lagoon in Australia. Int. J. Acarol. 26, 279- Ver. Bremen 27, 47-80. 283. Viets, K., 1938. Eine merkwürdige, neue, in Tiefsee- Otto, J.C., 2000f. Xenohalacarus longirostris n.gen., n.sp., a Echiniden schmarotzende Halacaridengattung und -Art marine mite (Acari: Halacaridae: Lohmannellinae) from (Acari). Z. Parasitenkde 10, 210-216. Chilcott Islet, Australia. Int. J. Acarol. 26, 285-291. Otto, J.C., 2000g. Seven new species of Arhodeoporus (Acarina: Halacaridae) from the Great Barrier Reef and Coral Sea. Hydrobiologia 436, 1-16.

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Fig. 1: Generalized halacarid. A, idiosoma and legs, dorsal aspect. B, idiosoma and gnathosoma, ventral aspect.

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Fig. 2: A, halacarid mite with porose areolae, dorsal aspect; B, diagram of integument with rosette pores (from Newell 1947, Crowe and Camara 1973); C, tarsus I; D, ambulacrum and claws; E, idiosoma, dorsal aspect showing measure- ments of length and width; F, idiosoma and gnathosoma, ventral aspect, showing measurements of length and width [L (length) of AD, AE, GA, gnathosoma, idiosoma, OC, PD, PE; W (width) of AD, GA, gnathosoma, idiosoma, OC, PD].

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Fig. 3: Shape of idiosoma and gnathosoma, dorsal aspect.

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Fig. 4: Shape of idiosoma and dorsal plates.

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Fig. 5: Shape of ventral plates.

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Fig. 6: Shape of gnathosoma, dorsal aspect.

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Fig. 7: Shape of gnathosoma, ventral aspect.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 49

Fig. 8: Shape of palps and number of setae.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 50

Fig. 9: Shape of leg I.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 51

Fig. 10: Chaetotaxy and shape of legs.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 52

Fig. 11: Chaetotaxy of tarsus I.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 53

Fig. 12: Chaetotaxy of tarsus IV.

Fig. 13: Shape of claws.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 54

Fig. 14: Acanthohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 55

Fig. 15: Acanthopalpus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 56

Fig. 16: Acarochelopodia. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 57

Fig. 17: Acaromantis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, palp; F, leg I; G, tarsus I; H, tarsus II; I, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 58

Fig. 18: Acarothrix. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 59

Fig. 19: Actacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 60

Fig. 20: Agaue. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 61

Fig. 21: Agauides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 62

Fig. 22: Agauopsis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 63

Fig. 23: Anomalohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 64

Fig. 24: Arenihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 65

Fig. 25: Arhodeoporus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 66

Fig. 26: Atelopsalis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 67

Fig. 27: Australacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 68

Fig. 28: Bathyhalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 69

Fig. 29: Bradyagaue. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 70

Fig. 30: Camactognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 71

Fig. 31: Caspihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 72

Fig. 32: Coloboceras. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 73

Fig. 33: Colobocerasides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 74

Fig. 34: Copidognathides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, palps; E, gnathosoma, ventral aspect; F, leg I; G, tarsus I; H, tarsus II; I, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 75

Fig. 35: Copidognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, leg I, G, tarsus I; H, tarsus II; I, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 76

Fig. 36: Corallihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 77

Fig. 37: Enterohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, palp; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 78

Fig. 38: Halacarellus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 79

Fig. 39: Halacaroides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 80

Fig. 40: Halacaropsis. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 81

Fig. 41: Halacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 82

Fig. 42: Halixodes. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 83

Fig. 43: Isobactrus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 84

Fig. 44: Lohmannella. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 85

Fig. 45: Metarhombognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 86

Fig. 46: Mictognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 87

Fig. 47: Parhalixodes. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 88

Fig. 48: Pelacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 89

Fig. 49: Peregrinacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 90

Fig. 50: Phacacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 91

Fig. 51: Rhombognathides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 92

Fig. 52: Rhombognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV (male).

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 93

Fig. 53: Scaptognathides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 94

Fig. 54: Scaptognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 95

Fig. 55: Simognathus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, palp; F, leg I; G, tarsus I; H, tarsus II; I, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 96

Fig. 56: Spongihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 97

Fig. 57: Thalassacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 98

Fig. 58: Thalassarachna. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 99

Fig. 59: Thalassophthirius. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, male; C, gnathosoma, ventral aspect; D, leg I; E, tarsus I; F, tarsus II; G, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 100

Fig. 60: Tropihalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 101

Fig. 61: Werthella. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 102

Fig. 62: Werthelloides. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 103

Fig. 63: Winlundia. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006) Bartsch: Halacaroidea (Acari): a guide to marine genera 104

Fig. 64: Xenohalacarus. A, idiosoma, dorsal aspect; B, idiosoma, ventral aspect, female; C, idiosoma, ventral aspect, male; D, gnathosoma, ventral aspect; E, leg I; F, tarsus I; G, tarsus II; H, tarsus IV.

Org. Divers. Evol. 6, Electr. Suppl. 6 (2006)