Scallops
A student web page designed by Barbie Freeman

Closely related to oysters, clams and cockles, scallops belong to the Phylum Mollusca and the Class Bivalvia. The main features of scallops include a shell with strong radial ribs and wing-like hinges (called 'ears'), a mantle, and a foot. When relaxed, the two shells of the scallop spread to reveal a ring of blue eyes around the edge of the mantle. These eyes (called ocelli) do not form images but can detect shadows. Scallops are filter feeders and let water sweep in through their open mantle to catch tiny particles.

Swimming Scallop

There are two species of swimming scallop common to the Pacific Northwest. They are the smooth pink scallop, Chlamys rubida and the spiny pink scallop, Chlamys hastata. Both pink species of scallop often don't look pink at all as the entire surface of their shell is typically covered in sponge.

Unlike most bivalves, swimming scallops are free swimming as their name suggests. Particularly when faced with a predator, swimming scallops can propel themselves away from the danger by clapping their valves together and forcing water out through openings on both sides of their shell hinge. This motion is repeated until the scallop is out of danger.

Rock Scallop

Unlike the swimming scallop, the purple-hinged rock scallops (Crassadoma gigantea) only swims for a brief period of its life while it is still very young. As the juvenile develops and the shell gets heavier, the scallop cements its lower right shell to hard objects and so can no longer swim away. Rock scallops can be hard to spot as their shells are covered with a variety of plants and animals that disguise the scallop in its surrounding environment. Rock scallops are often infested with hungry yellow sponge that bore into and eat away at their shell. To protect itself from sponges, the rock scallop has a thicker shell, and closes itself up whenever a hungry sponge is nearby.

References:

Invertebrate Zoology Edward E. Ruppert & Robert D. Barnes

Seashore Life of the Northern Pacific Coast Eugene N. Kozloff

Whelks to Whales Rick M. Harbo

 to Marine Biodiversity index