Zanclea species (Hydroidomedusae, Anthomedusae) from the Mediterranean
C. Gravili, F. Boero, J. Bouillon

Three species of hydroids referable to the genus Zanclea are recorded from the Apulian waters (Ionian Sea). Species distinction is based mainly on cnidome, and especially on the morphology and position of macrobasic euryteles: Zanclea sessilis growing on bryozoans, with apotrichous macrobasic euryteles with shaft coiled in a horseshoe shape, disposed in a circle around the hypostome, and in the hydrorhiza; Zanclea costata growing on bivalve shells, with holotrichous (?) macrobasic euryteles with a spirally coiled shaft, abundant in the hydrorhiza and rare in the hydranth body; and Zanclea sp. growing on bryozoans, with apotrichous macrobasic euryteles of two sizes, both with shaft coiled along the long axis of the capsule, dispersed in the hydranth body and in the hydrorhiza. The hydroids of Zanclea sessilis and Zanclea sp. were reared under identical controlled conditions for more than one year, but their morphological features remained unchanged and they both produced medusae. The medusae of Zanclea sessilis were reared to maturity, those of Zanclea sp. just to a young age. The main difference between the medusae was the consistent presence of an enlargement of the middle part of radial canals in Zanclea sessilis (from newly released to adult specimens), a feature lacking in Zanclea sp. It is confirmed that, as already suggested by severa1 authors, cnidome is a reliable feature for species identification of Zanclea hydroids, but medusa identification remains more problematic. In spite of the widespread claim that Zanclea is represented world-wide by a single species, it is here demonstrated that the genus comprises at least three species in the Mediterranean.

Keywords: Zanclea, Hydromedusae, taxonomy, life cycle, nematocysts, Mediterranean sea.
Contents of this volume Sci. Mar. 60(1) : 99-108 Back PDF
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