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Nematocysts in Tubularia larynx (Cnidaria, Hydrozoa) from Scandinavia and the northern coast of Spain
C. Östman, M. Myrdal, P. Nyvall, J. Lindström, M. Björklund and A. Aguirre

The morphology, distribution and function of nematocysts of Tubularia larynx Ellis & Solander 1786 (Ectopleura larynx sensu Petersen 1990) from Scandinavia and from the northern coast of Spain were studied by light and scanning electron microscopy. Differences were found between the cnidomes of the two populations. The nominal species T. larynx might prove to comprise more than one species, one from Scandinavian waters and the other from northern Spain. Four categories of nematocysts were identified in the Scandinavian T. larynx and five categories in the Spanish T. larynx. Morphologically identical nematocysts were found within the categories of stenoteles, desmonemes, microbasic mastigophores and isorhizas in the two hydroid populations. The fifth category, the euryteles, was however only identified in the Spanish hydroids. The size of the stenoteles and differences in the nematocyst distribution were additional features separating the two hydroid populations. Prey-capturing experiments were performed with Artemia sp. nauplii, marine plankton and small invertebrates living close to or in the Tubularia colonies. Artemia nauplii were captured, paralysed and eaten. Most small planktonic crustaceans were also preyed upon, but Evadne sp., Podon sp. and large planktonic copepods often escaped. Other crustaceans, for example Corophium sp., members of the families Harpacticidae, Caprellidae and Ieridae, which lived in the Tubularia colonies were neither paralysed nor captured.

Keywords: Hydroid, nematocysts, SEM, stenoteles, desmonemes, microbasic mastigophores, isorhizas, euryteles.
Contents of this volume Sci. Mar. 59(2) : 165-179 Back PDF
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