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POSTER
(abstract)
K.
Iken, A Fontana and G. Cimino "FEEDING DETERRENCE IN ANTARCTIC OPISTHOBRANCHS " In recent years the number of studies dealing with natural products from marine invertebrates has increased considerably. Opisthobranch molluscs are among the main groups of interest because of the reduction or the lack of mechanical defenses. Natural products from opisthobranchs have been described to have a wide range of structural characteristics, activities and origin. Often, these chemicals are assumed to have antipredator activities, therefore playing an essential role in their survival. However, very few studies have demonstrated that the chemicals are really effective in protecting the opisthobranchs from their potential predators. During the austral summer of 1998 we had the opportunity to participate in the EASIZ II expedition (ANT XV/3) on board of the German ship R/V Polarstern and to collect opisthobranch molluscs from the Weddell sea and the Antarctic peninsula. We decided to test whether the chemicals from selected species were really feeding deterrents against potential predators from Antarctica. We carried out a number of tests, mainly using the omnivorous seastar Odontaster validus as a potential predator. The tests were made with alive animals, fresh or frozen tissue, crude extracts, fractions or isolated compounds (when possible). The results show that some species are clearly protected against predation by O. validus, and we have been able to establish which one of their chemicals is the responsible molecule for the feeding deterrence (for example, for Bathydoris hodgsoni). Secondary metabolites seem to be, therefore, important factors in controlling some interspecific relationships within the Antarctic marine benthic communities.
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