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Giant Rock Scallop

Crassedoma giganteum

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Giant Rock Scallops have coarsely ribbed shells called valves. The upper valve is usually scallop-shaped but the lower valve takes the shape of the substrate to which it is attached. The thick, heavy valves are brownish on the outside and often riddled with tiny holes. Inside, they are pearly white with a dark purple blotch on the central part of the hinge. The scallop itself is orange with numerous blue eyes and sensory tentacles around the margin.

Juvenile Giant Rock Scallops are unattached and swim by clapping their valves together repeatedly and spurting jets of water outward on either side of the hinge. After attaining a diameter of about 1 inch (2.5 cm), the scallop cements its right valve to a rock and thereafter grows and lives as an attached or sessile organism. Like other bivalves, Giant Rock Scallops eat by filtering plankton and tiny organic particles from seawater.

Range and Habitat

Giant Rock Scallops are common from the Queen Charlotte Islands, British Columbia to Baja California. They live in rock crevices along the exposed outer coast, underneath floats and on pilings in bays from the low intertidal zone to subtidal depths of 164 feet (50 m).

he. Conservation Status

Common.