ZANCLEA SPECIES (HYDROIDOMEDUSAE, ANTHOMEDUSAE) FROM THE MEDITERRANEAN

Three species of hydroids referable to the genus Zanclea are recorded from the Apulian waters (Ionian Sea). Species distinction is based mai nly on cnidome, and especially on the morphology and position of macro basic euryteles: Zanclea sessilis growing on bryozoans, with apotricho us macrobasic euryteles with shaft coiled in a horseshoe shape, dispos ed in a circle around the hypostome, and in the hydrohiza; Zanclea cos tata growing on bivalve shells, with holotrichous (?) macrobasic euryt eles with a spirally coiled shaft, abundant in the hydrorhiza and rare in the hydranth body; and Zanclea sp. growing on bryozoans, with apot richous macrobasic euryteles of two sizes, both with shaft coiled alon g 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, b ut their morphological features remained unchanged and they both produ ced 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 middl e part of radial canals in Zanclea sessilis (from newly released to ad ult specimens), a feature lacking in Zanclea sp. It is confirmed that, as already suggested by several authors, cnidome is a reliable featur e for species identification of Zanclea hydroids, but medusa identific ation remains more problematic. In spite of the widespread claim that Zanclea is represented world-wide by a single species, it is here demo nstrated that the genus comprises at least three species in the Medite rranean.