Argopecten irradians

Argopecten irradians - Bay Scallop

Habitat The Bay Scallop typically occurs in seagrass beds of shallow waters. Unlike a lot of other bivalves, Bay Scallops simply lay on the bottom and do not bury themselves in the sand. Shells are found on sandy beaches.

Range Occurs in seagrass beds of Atlantic coastal waters from New Jersey to Florida and in the Gulf of Mexico.

Description The Bay Scallop is a member of the family Pectinidae. It can be distinguished from similar species because the right valve is more rounded than the left and its shell is a broad fan shape. It will also have more than 14 radial ribs. Their shells are symmetric and vary in color, but usually incorporates a pattern of dark grey, black, brown, orange, red or yellow.

These scallops have short tentacles, possess 30 to 40 blue eyes around the edge of their shell and, unlike most bivalves, lack a foot or a siphon. Each eye has a lens, retina, cornea and optic nerve, which allows the scallop to see movements and shadows. They grow to about 3 inches in diameter.

Ecological Notes Bay Scallops typically live anywhere from 12-18 months, but the longest living scallops can survive up to 26 months. They reach sexual maturity around age one and spawning occurs in the summer. The young scallops will attach themselves to the seagrass using threads, but eventually drop to the bottom as they grow.

These scallops are hermaphrodites, which means they possess both male and female sex organs. They will release male gametes before releasing female gametes to prevent self-fertilization. They only have one reproductive cycle during their lifetime.

Scallops are filter feeders and catch primarily plankton in their gills. Sea stars and some other bottom feeding organisms will prey upon these scallops.

Scallops can move by rapidly "clapping" their shells together. This ejects water from their cavity. This type of locomotion is different than most bivalves because most others use their foot to move around.

Personal Information I came across many bay scallop shells while walking along the beaches of North Carolina

References

Smithsonian Marine Station at Fort Pierce's Page on Argopecten irradians

Chesapeake Bay Program's Page on Bay Scallops

Additional Information

White, M.M., McCorkle, D.C., Mullineaux, A.L. 2013. Early exposure of Bay Scallops (Argopecten irradians) to high CO2 causes a decrease in larval shell growth. PLoS ONE, 8(4):1-8.

The authors of this paper focused on identifying the problems that ocean acidification may be causing for Argopecten irradians larvae. They performed tests in which a set of bay scallop larvae were placed in water with high CO2 and another set was placed in water with ambient CO2 levels. They found that many scallops placed in the high CO2 died within the first day and had significantly smaller shell sizes in comparison to the other group after 7 days of exposure. Therefore, the rising CO2 levels are affecting the larval stages of this organism.

Hernandez Cordero, A.L., Seitz, R.D. 2014. Structured habitat provides a refuge from blue crab, Calinectes sapidus, predation for the bay scallop, Argopecten irradians concentricus. Journal of Experimental Marine Biology & Ecology, 460:100-108.

This paper studied the ecology of Argopecten irradians and its predator, the blue crab. Researchers studied the survival rate of bay scallops based on the size of female blue crabs. They found that scallops of all sizes had a higher survival rate when placed with small female blue crabs. There was a significantly lower survival rate when scallops were among larger female blue crabs. However, when scallops were in oyster shells they seemed like they were able to survive. Tethering experiments were performed to further test these ideas. Transplanting these scallops to more protective substrates will increase restoration efforts, claims these researchers.

Contributed by Isabella Steiner - 2016

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