Secondary metabolites from Mediterranean Elysioidea: origin and biological role

Three Mediterranean sacoglossans (Elysia translucens, Bosellia mimetica and Elysia viridis) have been submitted to chemical investigations. The chemical structure (diterpenoids and polypropionates) of their potential allomones has been clarified. Some metabolites (diterpenoids) are also present in the preferred algal food of the molluscs. E. viridis is able to construct de novo metabolites (polypropionates) absent in the algae. A more general evolutionary trend of Mediterranean Elysioidea molluscs is suggested by adding the results reported herewith to the previous studies on Elysia timida and Thuridilla hopei and by comparing the metabolic pattern of T. hopei with that of the algae Derbesia tenuissima