Chlamys hastata (G. B. Sowerby II 1842)

How to Distinguish from Similar Species: Other similarly-shaped and ridged species, such as Chlamys rubida, do not have the prominent spines on their ribs

Mostly subtidal, Mainly on sandy or shelly hash bottoms; also among boulders

Geographical Range: Gulf of Alaska to San Diego, CA

Depth Range: Mostly subtidal; in our area they seem to predominate at shallower depths and in rockier areas than does Chlamys rubida. Sometimes also low intertidal or on floats.

This scallop has both valves convex, with ribs proceeding from the umbo to the ventral edge, which are covered with prominent spines or ruffles. There is no purple blotch on the inside of the shell near the hinge. Shells are up to about 6 cm long. The auricle at the hinge projects farther anteriorly than posteriorly

Biology/Natural History: Very common in waters near Rosario. Often attach to the bottom by a few byssal threads. Nearly always lie with the left valve upward. Their left valve is usually more brightly colored than is the right valve. Are almost always covered by the encrusting sponge Myxilla incrustans; less often by the brown or purple sponge Mycale adherens. These two sponges are found only on scallops. The symbiosis is likely mutualistic. If one of the major predators of the scallop, Evasterias troschelii, encounters the scallop it often turns away if it touches the sponge; likely in response to some secretion or to the spicules from the sponge. The sponge also appears to make it more difficult for the seastar's tube feet to adhere to the scallop. If the sponge is removed from the scallop and the scallop is prevented from swimming, it is readily captured by the seastar. The scallop will also swim from predators of the sponge, such as Archidoris spp, so the sponge is benefited as well. The swimming scallop may also help carry the sponge into areas with clean water and good currents, nd help prevent fouling of the sponge. Chlamys hastata is sometimes parasitized by the ectoparasitic Clam Sucker snail Odostomia columbiana. The foot is highly reduced and there are no siphons. The edge of the mantle is lined with small tentacles and several hundred beautiful blue eyes. These eyes can detect light and dark but cannot form an image. Filter feeds about 4 liters of water per gram per hour. Several seastars are predators of this species, including Pycnopodia helianthoides and Crossaster papposus. The scallops have a well-developed escape response of clapping the valves together like a pair of false teeth and swimming away by jet propulsion. Click here for an .MPG file of the escape. Sexes are separate. The ovary is orange, testes are white. Veligers form about 50 h after fertilization. Form annual growth rings in January or February, live about 6 years in southern BC.