ABSTRACT
Commercially important edible shellfish include marine and freshwater animals that belong to two major taxonomic groups: the Mollusca and the Crustacea. The hard external shell is a common external characteristic that often results in the two groups being given the common name shellfish. Both groups are invertebrates that have no internal skeleton or vertebrae, and in most cases the external shell provides protection, support to soft body tissues, and a mechanism to deal with changes in the environment. The cephalopods (squid, cuttlefish, and octopus) do not possess an external shell, but are grouped with the shellfish by virtue of their molluscan taxonomic status.
