Hydrozoan People Come Together Presently So Separate As to Have Different Specialized Journals, with Practitioners Who Rarely Interact

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7 Wardle, D.A. et al. (1997) The influence of 12 Ward, A.K., Dahm, C.N. and Cummins, K.W. Two lively discussions were dedi- island area on ecosystem properties, Science (1985) Nostoc (Cyanophyta) productivity in cated to the possibility of new funding for 277, 1296–1299 Oregon stream ecosystems: invertebrate taxonomic research on Hydrozoa, with 8 Tilman, D. et al. (1997) The influence of influences and differences between suggestions about specific problems that functional diversity and composition morphological types, J. Phycol. 21, 223–227 the group hoped such new hydrozoan on ecosystem processes, Science 277, 13 Wagener, S.M., Oswood, M.W. and Schimel, J.P. experts might tackle during their train- 1300–1302 (1998) Rivers and soils: parallels in carbon and 9 Hooper, D.U. and Vitousek, P.M. (1997) nutrient processing, BioScience 48, 104–108 ing. The unification of classification, in- The effects of plant composition and 14 Wardle, D.A. et al. Experimental removal of cluding the use of molecular techniques, diversity on ecosystem processes, Science plant functional groups in a perennial was still perceived as the main taxo- 277, 1302–1305 grassland: implications for vegetation nomic problem. It was agreed, however, 10 Freckman, D.W. et al. (1997) Linking dynamics, decomposer food-webs, soil that knowledge of morphology and ecol- biodiversity and ecosystem functioning biodiversity and ecosystem properties, Ecol. ogy are prerequisites to the use of mol- of soils and sediments, Ambio 26, Monogr. (in press) ecular tools and that the organisms are 556–562 15 Siemann, E. (1998) Experimental tests of effects as important as the molecules of which 11 Chauvel, A. et al. An Amazonian earthworm of plant productivity and diversity on they are composed. How to merge mor- compacts more than a bulldozer, Nature grassland arthropod diversity, Ecology 79, phological and molecular taxonomy and (in press) 2057–2070 systematics was the subject of a discus- sion led by Bernd Shierwater (Freiberg University, Germany) and Diane Bridge (University of California, Irvine, USA). With very few exceptions, the molecular and the morphological approaches are Hydrozoan people come together presently so separate as to have different specialized journals, with practitioners who rarely interact. One result of this is that traditional taxonomists are often ydrozoa (Cnidaria) are common In 1985, several researchers founded aware of problems but do not know how Hthroughout the World Ocean, both the Hydrozoan Society. The main event to solve them, whereas molecular tax- in the benthos and in the plankton, that keeps the society alive is a work- onomists have the tools to solve prob- with around ten thousand living spe- shop held every four years. This year, lems they are not aware of. cies. Their basic life cycle comprises the fourth workshop of the Hydrozoan A molecular approach, based on the benthic modular polyp colonies that Society took place at the Bodega Marine complete small ribosomal subunit (18S) grow by budding and, in some cases, pro- Laboratory of the University of California gene sequence, led Allen Collins (Univer- duce individual planktonic medusae by at Davis (USA). The chance to spend two sity of California, Berkeley, USA) to explore a process related to budding. Medusae full weeks with ones scientific peers is the phylogenetic history of the Hydro- reproduce sexually, with fertilization rare today, and even two weeks is not zoa, reviving a suggestion by Haeckel that typically leading to a planula larva that enough time to pursue everything one the Siphonophora are nothing more than settles on the bottom to form a polyp would like; despite this, many new collab- a group of Anthomedusae – something colony. orations were forged. that is perceived by many specialists but Many important biological phenom- The meeting opened with an analysis that needs further support (like that pro- ena have been discovered through the of the hydrozoan literature since the vided by Collins) to become incorporated study of hydrozoans, from the possi- 1900s. Cinzia Gravili (University of Lecce, into zoology textbooks. Antonio Marques bility of tissue grafting, to sperm attrac- Italy) reported on a data set of more (Universidade de São Paulo, Brazil) pro- tion by the egg, to transdifferentiation than ten thousand papers, originally vided morphological evidence that also (the dedifferentiation and redifferen- compiled by Wim Vervoort2 (National supported this conclusion. tiation of cells) and to bioluminescence Museum of Natural History, Leiden, The Textbook knowledge was challenged with its associated green fluorescent pro- Netherlands). She showed that taxo- many times at Bodega Bay. Jack Costello tein. The separate study of polyps and nomic research on the group has nearly (Providence College, Providence, RI, medusae, however, has plagued hydro- vanished in countries that once had USA), for instance, showed convincing zoan taxonomy since its outset, with the the strongest tradition (UK, USA and video footage demonstrating that flat- building of two separate classifications, France), whereas countries with almost belled medusae do not actually use jet one for medusae and one for polyps. Sin- no tradition in this field (such as propulsion but simply flap their bells, gle species have many times been given Spain) are now among the few contribut- swimming more like other gelatinous two different names because medusae ing to its advancement. Eric Hochberg plankters, such as molluscs. Only stream- and polyps have been (and still are) stud- (Santa Barbara Natural History Museum, lined medusae – round or tall forms with ied by different specialists. This incon- CA, USA), Daphne Fautin (University a narrow velar opening – actually proceed gruency is so striking that Hennig1 sug- of Kansas, Lawrence, USA) and Cliff by jet propulsion. Ferdinando Boero gested it as a possible test for the efficacy Cunningham (Duke University, Durham, (University of Lecce) continued to dis- of cladism. He argued that a cladistic- NC, USA) discussed the recent USA rupt the certainties of zoology textbooks phylogenetic classification based just National Science Foundation (NSF) aware- by further developing an argument that on medusae should match a similar one ness that this trend is common to most the bell cavity of hydromedusae is a true based only on polyps. This test has not animal groups, and that the USA scien- coelom, being closed during ontogeny yet been attempted; hydrozoan taxono- tific community has lost or is rapidly and having a lining of striated muscle3. mists have been working at building a losing its taxonomic expertise. The NSF If this view is accepted, hydromedusae single classification since the beginning is now trying to revive taxonomy by should be triploblastic and the whole of this century, but the task is still far supporting the training of new experts scenario of metazoan phylogeny needs to from complete. through special programmes. be reassessed.

Other surprises came from Hans usually the main constraint to recruitment, Ecological contributions included that Grüger (University of Basel, Switzerland), so the most devastating predators of spe- of Sergi Rossi (Institut de Ciències del Mar, who reported on the occurrence of PAX cies that reach large adult sizes are not Barcelona, Spain), who discussed trophic (homeobox domain plus paired domain) necessarily big themselves. On the con- strategies of hydroids under different genes in hydrozoans. Some PAX genes trary, small and efficient predators can environmental conditions. A parallel ap- are responsible for the coding of eyes in cause the demise of fish populations, as proach came from Maria Pia Miglietta (Uni- vertebrates and some invertebrates; they happened in the early 1990s in the Black versity of Lecce), who described several have now even been found in hydrozoan Sea with the establishment of the non- behavioural patterns of both hydroids species deprived of specialized sense or- indigenous ctenophore Mnemiopsis leidyi. and medusae, revealing an unexpected gans, where they appear to be involved in The report by Patrizia Pagliara (Uni- diversity in the way these simple animals nerve-cell differentiation. Given that cnid- versity of Lecce), on a species of Clytia react to different kinds of stimulus. The arians are considered to be diploblastic, able to produce floating colonies that can Hydrozoa are rich in strange animals. their condition is ancestral compared eventually settle on the bottom, recon- Yayoi Hirano (Kominato Marine Labora- with triploblasts. The occurrence of PAX firmed that polyps, as well as medusae, tory, Amatsu-Kominato, Japan) dealt with genes from cnidarians to vertebrates can lead a planktonic life. Sometimes, spe- the tiny crawling medusae of Staurocladia might indicate that these genes have been cies travel across geographic barriers on that live on tide pool algae; Shin Kubota co-opted for more specialized functions unexpected vehicles. Giorgio Bavestrello (Seto Marine Laboratory, Shirahama, during metazoan evolution, while remain- (University of Genova, Italy) reported on Japan) sketched the evolution of the hy- ing rather conserved in structure. a mysterious hydroid that inverts its po- droids living only in the mantle cavity of bi- Stefano Piraino (Istituto Talassografico larity during fission. A similar or identical valve molluscs; and Heike Hadrys (Goethe del CNR, Taranto, Italy) addressed the hydroid was studied briefly 40 years ago University, Frankfurt, Germany) explored question of how medusae grow. Most of in San Francisco Bay5 but was never found the genetic diversity of the marsupial the jellyfish body is made up of extracellu- again. It seems to have reappeared re- medusa Eleutheria, which forms clones of lar matrix (the jelly), and it is still not cently as a pest in the jellyfish tank of the benthic, hermaphroditic medusae. completely understood how acellular liv- Aquarium of Genova. Bavestrello’s study In spite of having almost abandoned ing matter can grow at places that are of its life cycle showed that these polyps taxonomy, the US scientific community is very far from the tissues that distribute nu- form cysts, and one explanation of their very strong in ecology, and talks by Dawn trients. One important idea that coalesced presence in the aquarium is linked to the Murray and Kevin Raskoff (both from the during the meeting is Project Hydrozoa, use of Artemia (a classic food for captive Monterey Bay Aquarium Research Insti- suggested by Bernd Schierwater. This marine animals) imported as cysts from tute, Moss Landing, CA, USA) revealed comprehensive project will allow scien- San Francisco Bay. It is possible that this unexpected gelatinous worlds that can tists from all over the world to contribute and other encysted forms are being dis- be appreciated only by those with access to a scheme in which 50–100 selected spe- persed throughout the world along with to diving submersibles in the depths of cies, widely distributed throughout the Artemia eggs (resting cysts). marine canyons. Research performed dur- Hydrozoa, would form one axis of a grand Jellyfish are now very popular in pub- ing the workshop led to the discovery of data availability matrix (DAM). The ma- lic as well as at-home aquarium displays, species previously unreported from the trix will include columns with life history and Danielle Richardi (Aquarium of the Pacific Coast of the USA, with information characteristics, molecular sequences for Americas, New Orleans, LA, USA) reported on their life cycles. Just two weeks of work several genes, nematocyst complement, on how she maintains such delicate crea- can improve knowledge of the biodiver- polyp and medusa morphologies, develop- tures. Many species in her display were sity of even well studied areas. ment, literature citations and other data. purchased at pet stores – there is a flour- Most scientists at the meeting committed ishing commerce of exotic jellyfish in the Ferdinando Boero themselves to making a special effort to USA. The many ways a species can be dis- Dipartimento di Biologia, Stazione di Biologia fill in parts of the matrix, thus building an persed, from ballast waters to pet stores Marina, CoNISMa, Università di Lecce, unprecedented web-accessible database and pet food caused much concern to 73100 Lecce, Italy ([email protected]) from which to answer phylogenetic and researchers working on introduced spe- evolutionary questions. cies; bored home aquarists might simply Claudia E. Mills Adam Benovic´ (Institute for Oceanog- liberate their pets in the sea and intro- Friday Harbor Laboratories, raphy and Fisheries Laboratory, Dubrov- duce alien species in any country. University of Washington, 620 University Road, nik, Croatia), and John Rees (California Other conservation issues were high- Friday Harbor, WA 98250, USA State University, Hayward, USA) reported lighted by Jeanette Watson (Museum of ([email protected]) on nonindigenous hydrozoan species in Victoria, Australia), who outlined the hy- marine ecosystems, providing examples droid fauna of recently discovered (and References from both Europe and America. They already heavily exploited) seamounts off 1 Hennig, W. (1979) Phylogenetic Systematics, University of Illinois Press stressed the role of ballast water in ships Australia, and Claudia Mills (University 2 Vervoort, W. (1995) Bibliography of Leptolida as a transport vector for alien species. of Washington, USA), who discussed de- (non-Siphonophoran Hydrozoa, Cnidaria). Hydrozoa are top predators in the marine clines in populations of large semibenthic Works published after 1910, Zool. Verh. environment, feeding on the eggs and lar- polyorchid medusae that have been used Leiden 301, 1–432 vae of almost all animals, including fish4. for decades as research animals on both 3 Boero, F. et al. (1998) The cnidarian premises of metazoan evolution: from triploblasty, to When abundant populations establish, sides of the North Pacific. Emmanuelle coelom formation, to metamery, Ital. J. Zool. they can exert strong pressures on species Buecher (University of the Western Cape, 65, 5–9 of commercial importance, decimating re- Cape Town, South Africa) and Hermes 4 Purcell, J.E. (1997) Pelagic cnidarians and cruitment. Fisheries can thus be sharply Mianzan (Instituto Nacional de Investiga- ctenophores as predators: selective affected by both medusan and hydroid cion y Desarrollo Pesquero, Mar del Plata, predation, feeding rates and effects on prey populations, Ann. Inst. Oceanogr. 73, 125–137 predation; the importance of gelatinous Argentina) reported on changes in jelly- 5 Hand, C. and Jones, M.L. (1957) An example of zooplankton is generally underestimated fish populations important for fisheries reversal of polarity during asexual reproduction in ecological studies. Larval mortality is and tourism in South Atlantic regions. of a hydroid, Biol. Bull. 112, 349–357

128 TREE vol. 14, no. 4 April 1999