What are you doing here? Investigating on an unexpected association in shallow Mediterranean dark caves sheds new light on the diet of Marionia blainvillea (Mollusca, Gastropoda, Nudibranchia)

In a shallow dark cave along the coast of Capo Palinuro (Campania, Italy), the finding of an unusual aggregation of individuals belonging to Marionia blainvillea (Gastropoda, Nudibranchia) has allowed to identify a population of Cervera atlantica (Cnidaria, Anthozoa, Alcyonacea) and to add this latter to the list of the hosts preyed by this tritoniid nudibranch. This association was confirmed by a second observation in a dark shallow cave in the Island of San Pietro (Sardinia, Italy). Moreover, a subsequent internet data mining shed light on the diet of M. blainvillea adding useful ecological notes on the scarcely known trophism characterizing Marionia species. Cervera atlantica is reported for the first time along the continental coast of Italy.