Infralittoral molluscs from the Scilla cliff (Strait of Messina, Central Mediterranean)

The mollusc taxocoenosis characterizing the photophilic zone of the Scilla cliff (Strait of Messina, Central Mediterranean) has been described on hard bottom samples from 6, 16 and 24 m depth. Seasonality has been evaluated by replicates carried out in autumn and spring. Overall, 229 benthic taxa have been recorded, 87 of which occurred in both seasons, while 109 were exclusively recorded in spring and 29 only in autumn. Specimen abundance also notably decreased from autumn to spring (1581 and 892 individuals, respectively). Depth scarcely affected the species distribution, probably due to water transparency, thermal homogeneity, and nutrient mixing. The recorded species cannot be all assigned to the photophilic rocky habitat, since ubiquitous taxa, organisms of other habitats settled in micro-enclaves, and juveniles of not established species have been frequently recorded. The role of algal covering as larval collector from disparate habitats is confirmed, as also proved by the high occurrence of planktonic molluscs (14 species) in all the examined samples. The whole mollusc taxocoene, whose diversity is high with respect to other areas at comparable latitudes, showed a marked western footprint, in accordance with the known biogeographic peculiarities of the Messina Strait.