Scientia Marina, Vol 64, No S1 (2000)

Life history of Perarella schneideri (Hydrozoa, Cytaedidae) in the Ligurian Sea


https://doi.org/10.3989/scimar.2000.64s1141

Giorgio Bavestrello
Istituto di Scienze del Mare dell’Università di Ancona, Italy

Stefania Puce
Istituto di Scienze del Mare dell’Università di Ancona, Italy

Carlo Cerrano
Dipartimento per lo studio del Territorio e delle sue Risorse dell’Università di Genova, Italy

Andrea Balduzzi
Dipartimento per lo studio del Territorio e delle sue Risorse dell’Università di Genova, Italy

Abstract


Perarella schneideri is a cytaeidid hydroid living in association with the bryozoan Schizoporella longirostris. In this study we have distinguished the presence of two kinds of polyps in its colonies: large gastrozooids and very extensible filiform polyps with 4 short tentacles. A study of the relationships between the hydroid and its host indicates a parasitic behaviour of P. schneideri on bryozoan adult colonies, and predation on bryozoan larvae. Study of hydroid stomach contents indicates that the trophic strategy of P. schneideri depends on two food sources: (i) a benthic one, mainly constituted of nematodes and polychaetes and (ii) a bryozoan source, which is performed in various ways. The Perarella schneideri colonies are, in turn, a food source for halacarids which perforate the hydranth wall and, penetrating the gastrovascular cavity, suck the semi-digested prey without evident damage to the polyps.

Keywords


Hydrozoa; Cytaeididae; life cycle; trofic strategy; parasitism; commensalism; Bryozoa

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