Halocoryne epizoica (Cnidaria: Hydrozoa) a hydroid that "bites"
Stefano Piraino, J. Bouillon, F. Boero
Halocoryne epizoica is abundant along the Apulian coast of SE Italy in association with the locally dominant cheilostome bryozoan Schizobrachiella sanguinea. Colonies are polymorphic, with gastrozooids and dactylogonozooids both deprived of tentacles. Reproduction occurs by liberable eumedusoids. The presence of macrobasic mastigophores and macrobasic euryteles (?) in the eumedusoid indicates a phylogenetic affinity with the Zancleidae. Halocoryne is therefore removed from the Corynoidea and is assigned here to the Zancleoidea. Halocoryne feeds on lophophoral tentacles of its bryozoan host. Single tentacles are engulfed and detached after a short period in the hydranth mouth while the bryozoan polypide is extended and later retracted. This behaviour is considered as a form of parasitism. Possible evolutionary trends of hydroids symbiotic with bryozoans are discussed.