OPISTHOBRANCH MOLLUSCS: EXTRAORDINARY MODELS TO INVESTIGATETHE ECOLOGY OF BENTHIC ORGANISMS

Guido Cimino, Margherita Gavagnin, Angelo Fontana and Maria LetiziaCiavatta
Instituto per la Chimica di Molecole di Interesse Biologico, Via Toiano,6 80072 Arco Felice, Napoli, Italy.

The opisthobranch molluscs provide excellent materials for the studyof marine ecology of benthic invertebrates. In fact, these gastropods arebarely protected by the shells which are either small and fragile or entirelyabsent. In spite of the absence of the mechanical protection, opisthobranchshave conquered numerous habitats, where they feed on different organisms:sponges, soft corals, algae, tunicates, poychaete annelids, hydroids andalso other molluscs. Often the selected food is that other animals tendto avoid, being distasteful and noxious. Natural products play a centralrole in trying to construct hypothetical scenarios concerning the evolutionof the opisthobranchs and their adaptive radiation in which the molluscshave diversified in habitat and in feeding biology.
Some selected topics will be presented to support the leading roleof natural products in driving evolution in a certain direction.Accumulation of dietary metabolites in the digestive glands, transfer ofthe protective molecules to the external parts of the mollusc and biosynthesisde novo of bioactive molecules seem to be key evolutive milestones.