Clams are called bivalves because they belong to a class of mollusks characterized by having two shells, or valves, that are hinged together. The term ‘bivalve’ itself is derived from the Latin words ‘bi’ meaning ‘two’ and ‘valve’ meaning ‘leaf’ or ‘door’ which indicates the unique two-part structure.
Each shell of a bivalve is made of calcite or aragonite and serves not only as a protective barrier against predators but also plays a role in the clam’s feeding process. When clams open their shells, they can filter feed by drawing in water and extracting tiny food particles, like plankton, that are suspended in the water. This unique anatomical feature is what sets bivalves, including clams, oysters, and mussels, apart from other types of mollusks, such as snails which have a single shell.
In summary, clams are called bivalves due to their distinctive two-shell structure, which is integral to their biology and lifestyle.