What is the difference between a clam, a cockle, a mussel, and a scallop?

The clam, cockle, mussel, scallop, and even the oyster, are all marine bivalve molluscs. Bivalve means two valves.

They all have a shell structure, called a mantle, with two valves (two halves) and a ligament hinge with two adductor muscles that enable them to open and close.

All bivalves have light-sensitive cells that can detect light and motion, even though most do not have eyes. Giant clams have simple eyes on the edge of the mantle. Scallops have more complex eyes on the edge of the mantle – they have 10-100 eyes that each have a lens, a two-layered retina, and a concave mirror.

 

They are all filter feeders that sift water over their valves to eat plankton in the water.

The clam can be any shape, such as oval, triangular, or elongated. The cockle is oval or globe-shaped. The oyster and scallop are elongated.

The clam can be found in freshwater and saltwater. The cockle, mussel, oyster and scallop are only found in saltwater.

The clam and cockle breathe through siphons – an inhalant siphon and an exhalant siphon. The oyster and scallop do not have siphons.

The clam, cockle, and oyster do not have auricles. A scallop has auricles which are triangular shapes near the hinge.

The clam, cockle and scallop do not live attached to any organism or substrate. The mussel and oyster live attached to a substrate, such as a rock.

The clam does not live near the bottom of the ocean. The cockle, mussel, oyster, and scallop liver near the bottom of the ocean.

 

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM