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Polymorphism in hydroids: the extensible polyp of Halecium halecinum (Cnidaria: Hydrozoa: Haleciidae)

Published online by Cambridge University Press:  18 December 2008

Nicole Gravier-Bonnet
Nicole Gravier-Bonnet*
Affiliation:
Laboratoire d'Ecologie Marine, Faculté des Sciences et Technologies, Université de La Réunion, 15 Avenue René Cassin-BP 7151, 97715 Saint-Denis Messag Cedex 9-La Réunion, France
*
Correspondence should be addressed to: Nicole Gravier-Bonnet, Laboratoire d'Ecologie Marine, Faculté des Sciences et Technologies, Université de La Réunion, 15 Avenue René Cassin-BP 7151, Saint-Denis Messag Cedex 9, La Réunion, France email: Nicole.Gravier-Bonnet@univ-reunion.fr
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Abstract

The study of living Halecium halecinum colonies revealed a new case of zooid polymorphism. Besides the ordinary hydranth, the polyp devoted to feeding, this species is provided with a second kind of polyp, differing only slightly in structure and morphology but most conspicuously in its behaviour. It is named ‘extensible polyp’ in reference to its great extensibility and the resulting filiform shape. There are slight differences in the tentacles: lower number, shorter length, thicker diameter, and the tip slightly swollen and rounded instead of tapering. Their large microbasic mastigophores are abundant and evenly distributed, while the hydranth has a few large ones only on the oral side but has otherwise numerous small ones. When extended and at rest, the tubular column is much longer than that of the hydranth and not delimited from the head of the polyp by a bulge followed by a constriction. Behavioural differences are its capacity to coil and bend during extension and thus being able to move in all directions and exploring a large volume of seawater, and also its ability to produce regional swellings (peristalsis) and to contract by folding and bulging though still extended. Besides a probable role in defence, the extensible polyp exhibits an excretory function and it could also have sensory functions. The extensible polyp type is not classified as a nematophore because it has a functional gastrovascular cavity and a mouth. Polyp dimorphism (hydranth/extensible polyp) is reported in one more halecid and two sertularids.

Keywords

polymorphismhydroidsextensible polypHalecium halecinum
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 88 , Special Issue 8: Hydrozoans , December 2008 , pp. 1731 - 1736
Copyright
Copyright © Marine Biological Association of the United Kingdom 2008

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References

REFERENCES

Bouillon, J. (1986) Nemalecium gen. nov., genre nouveau de Haleciidae (Thecatae–Leptomedusae, Hydrozoa, Cnidaria). Indo-Malayan Zoology 3, 71–80.Google Scholar
Bouillon, J. (1994) Classe des Hydrozoaires. In Grassé, P.P. (ed.) Traité de zoologie. Paris: Masson, pp. 29–416.Google Scholar
Bouillon, J., Gravili, C., Pagès, F., Gili, J.M. and Boero, F. (2006) An introduction to Hydrozoa. Publications Scientifiques du Muséum, Paris [Mémoires du Muséum National d'Histoire Naturelle, T. 194.].Google Scholar
Calder, D.R. (1991) Shallow-water hydroids of Bermuda. The thecatae, exclusive of Plumularioidea. Life Sciences Contributions of the Royal Ontario Museum 154, 1–140.Google Scholar
Cornelius, P.F.S. (1975) A revision of the species of Lafoeidae and Haleciidae (Coelenterata: Hydroida) recorded from Britain and nearby seas. Bulletin of the British Museum of Natural History, Zoology 28, 375–426.Google Scholar
Cornelius, P.F.S. (1995) North-west European thecate hydroids and their medusae. Parts 1 & 2. Shrewsbury: Field Studies Council for the Linnean Society of London and the Estuarine and Coastal Studies Association. [Synopses of the British Fauna (New Series) (Barnes, R.S.K. and Crothers, J.H. (eds)) no. 50.]Google Scholar
Cornelius, P.F.S. (1998) Taxonomic characters from the hydranths of live thecate hydroids: European Haleciidae (Cnidaria: Leptothecatae). Zoologische Verhandelingen 323, 79–97.Google Scholar
Gravier-Bonnet, N. (1998) Undescribed polymorphism in sertularids (Cnidaria Hydrozoa, Thecatae): morphology and behavior of tentaculate polyps presumed to be defensive. Abstract, 4th Workshop of the Hydrozoan Society, Bodega Marine Laboratory, USA (19 September–3 October 1998).Google Scholar
Gravier-Bonnet, N. (2004) Hydroid nematophores types: morphological, structural and behavioural variety from old knowledge and new data. Hydrobiologia 530/531, 199–208.Google Scholar
Gravier-Bonnet, N. and Bonnet, B. (2000) Contribution of studies on live corals to estimate hydroid biodiversity in coral reefs. 9th International Coral Reef Symposium, Bali, 23–27 October 2000, Abstract, p. 145.Google Scholar
Gravili, C. (2007) Plymouth marine fauna and hydrozoa, an illustrated guide. Plymouth: Marine Biological Association of the United Kingdom, 144 pp.Google Scholar
Hincks, T. (1868) A history of the British hydroid zoophytes. London: J.V. Voorst.Google Scholar
Hirohito, Emperor of Japan (1971) Additional notes on Clathrozoon wilsoni Spencer. Tokyo, Japan: Biological Laboratory Imperial Household, 5pp.Google Scholar
Migotto, A.E. (1996) Benthic shallow-water hydroids (Cnidaria, Hydrozoa) of the coast of São Sebastiao, Brazil, including a checklist of Brasilian hydroids. Zoologische Verhandelingen 306, 1–125.Google Scholar
Naumov, D.V. (1960) Hydroids and Hydromedusae of the USSR. Jerusalem: Israel Program for Scientific Translations, 1969.Google Scholar
Vervoort, W. (1987) Evaluation of taxonomic characters in the Hydroida, particularly the Thecata (=Leptomedusae). In Bouillon, J., Boero, F., Cicogna, F. and Cornelius, P.F.S. (eds) Modern trends in the systematics, ecology and evolution of hydroids and hydromedusae. Oxford: Clarendon Press, pp. 29–42.Google Scholar