Chlamys rubida

Lore & Background

The pink scallop has two convex valves joined by a hinge joint, each with an umbo from which 20 to 30 shallow ridges radiate to the margin. The left valve is usually uppermost and is some shade of red intermixed with white streaks, with annual growth rings and concentric sculpturing. The lower valve is either a paler shade of pink or dull white. A large auricle is present on one side of the umbo. When feeding, the mantle becomes visible, fringed with short tentacles and a ring of tiny eyes near the margin of each valve. It can be distinguished from the spiny scallop (Chlamys hastata) by its more rounded valves and lack of spines on the ribs, giving a smooth texture; its glossy white interior lacks purplish markings.

Reader's Guide

The pink scallop is found on the Pacific Coast of North America at depths down to about 300 metres, ranging from Alaska to San Diego, California, and is more common in the northern half of this range. It also occurs in Kamchatka, the Sea of Okhotsk and Japan, on rocks or sandy or muddy sea beds. Its ecological significance is highlighted by its symbiotic relationship with the encrusting sponge Myxilla incrustans, which grows on its left valve. The sponge provides camouflage and may deter predators; it also makes it harder for a starfish to pull open the scallop with its tube feet. In laboratory conditions, sponges on empty scallop shells died when sediment was stirred up, while those on living shells flourished. When a starfish such as the mottled star (Evasterias troschelii) approaches, the scallop detects it with chemoreceptors on its tentacles and swims away by clapping its valves. If a starfish touches the sponge, it often turns away, apparently repelled by the distasteful coating.

Did You Know?

• The pink scallop grows to a diameter of about 6 centimetres.
• It has a symbiotic relationship with the orange sponge Myxilla incrustans.
• The scallop can detect a starfish using chemoreceptors at the tips of its tentacles.
• Its left valve is usually red with white streaks, while the lower valve is paler pink or dull white.