molluscs
Molluscs are a diverse and widespread phylum of invertebrate animals. They vary greatly in form, from the shelled gastropods and bivalves to the highly cephalized cephalopods, and include less familiar groups such as chitons and tusk shells. Most possess a soft body and, in many species, one or more calcareous shells produced by the mantle. The defining body plan includes a muscular foot, a visceral mass containing most of the internal organs, and a mantle that often secretes the shell and encloses a mantle cavity housing the gills, nephridia, and other organs.
Major classes include Gastropoda (snails and slugs), Bivalvia (clams, mussels, oysters, scallops), Cephalopoda (octopuses, squids, cuttlefish,
Ecologically, molluscs perform important roles as grazers, filter feeders, and prey, and cephalopods are often top