ABUNDANCE, FEEDING-BEHAVIOR AND NEMATOCYSTS OF SCYPHOPOLYPS (CNIDARIA) AND NEMATOCYSTS IN THEIR PREDATOR, THE NUDIBRANCH CORYPHELLA-VERRUCOSA (MOLLUSCA)

The abundance of Aurelia and Cyanea scyphopolyps on Laminaria sacchari na was higher in sheltered, shallow areas compared with more exposed o r deep ones. Liberated planulae probably were not transported far away from stranded and trapped jellyfish and settled nearby, preferably in patches on the downward side of the Laminaria thallus. The principal prey for the scyphopolyps seems to be small copepods and the cladocera ns Podon sp, and Evadne sp., which are abundant in surface waters duri ng the summer. Temporarily abundant planktonic organisms, e.g., Sagitt a setosa, Pleurobrachia pileus and hydromedusae might, also be importa nt prey. Harpacticids, halacarideans and Corophium sp., whose natural habitat is on L. saccharina, were not captured by the scyphopolyps. Sc yphopolyps cultured in running sea water rich in detritus and phytopla nkton fill their enteron with organic substrates, particularly diatoms . A new category of heterotrichous microbasic rhopaloid nematocysts wa s identified in the scyphopolyps. These rhopaloids were earlier includ ed within the euryteles and were not considered to be separate nematoc ysts. They are distinctive from the euryteles due to the two swellings on their discharged shaft. The absence or presence of the nudibranch Coryphella verrucosa laminarian thalli possibly has an effect on the n umber of scyphopolyps, as this nudibranch consumes numerous scyphopoly ps. Isorhizas and the new category of rhopaloid nematocysts, identical to those present in the Aurelia polyps, occurred in the cnidosacs of examined C. verrucosa. The proportion of rhopaloid nematocysts compare d with a-isorhizas was noticeably higher in C. verrucosa than in scyph opolyps. The nudibranch may selectively store rhopaloids.