Molluscs

The Molluscs phylum in the Italian seas shows a high level of variety and diversity  with about 1619 species (divided into 8 Classes: Caudofoveata, Solenogastres, Monoplacophora, Polyplacophora, Gastropoda, Bivalvia, Scaphopoda and Cephalopoda).
From a morphological point of view, Molluscs are generally characterized by a head, a muscular foot, a shell (which can be external, internal, or in some cases absent) and a radula (a scraping organ used for feeding themselves, which is absent in Bivalvia).  As a whole, this group shows an evolutionary plasticity that allowed it to occupy a wide range of ecological niches. Evidence is given by the differences between an oyster on a hard substrate  in comparison with the speed of movement of a cuttlefish or squid, placing between these two extreme examples a multitude of intermediate adaptations.