#pectinida

If you want pearls, don't bother looking at spiny oysters. As members of the order Pectinida, they are actually more closely related to scallops than true oysters. What's more, most species of spiny oyster have an extra layer of protection in the form of spines that grow from their shells, some of which can grow up to 5 cm (1.6 in) in length!

📍 Location: Nags Head, North Carolina 🗓 Date: May 24, 2025 🐾 Media: Image 🌿 Species: Atlantic Calico Scallop (Argopecten gibbus) 📝 Notes: Small marine bivalve found in sandy or shelly substrates in shallow coastal waters of the western Atlantic. Shell is fan-shaped with radiating ribs and variable coloration, often showing mottled patterns of orange, red, purple, and white.

Unlike many bivalves, scallops are capable of limited swimming by rapidly clapping their shells together to create jet propulsion, allowing short bursts of movement when disturbed.

Iridescent clam (Pedum spondyloideum)

Scope Out the Atlantic Sea Scallop

The Atlantic Sea scallop, also known as the deep sea scallop (Placopecten magellanicus), is a species of scallop native to the North American coastline of the Atlantic Ocean, from southern Canada to the coastal plains of the mid-region United States. They primarily reside along rocky or sandy areas of the ocean floor from depths of 18–110 m (59-360 ft), although they can occasionally be found at depths as shallow as 2 m (6 ft).

The Atlantic sea scallop is characterized by its two round, smooth shells with a squared off foot. The color of this shell can vary from red or pink to brown or white, and is on average 8 cm (3.25 in) in diameter. Around the interior edge of the shell, set in a white film-like substance called the mantle, are several dozen rudimentary eyes, which are capable of perceiving light and movement. Also emerging from the mantle are a number of small tentacles which are used to filter food from their surroundings.

Deep sea scallops are filter feeders, consuming microorganisms such as phytoplankton, zooplankton, and bits of detritus which float in the water column. In turn they are predated upon by large fish such as cod and flouders, , crabs, lobsters, sea turtles, and sea stars. Their shell provides some protection from predators, and when that fails, adults are able to move from one area to another by sucking water in through their valves and then forcefully ejecting it, much like a cephalopod.

Although they are not actively social, deep sea scallops typically occur together in large numbers; these aggregations, or beds, can have densities as high as 38 individuals per square meter. Population densities may fluctuate based on food availability and reproductive status.

About 4% of the P. magellanicus population is capable of producing both male and female gametes, but the majority produce only one or the other. However, individuals have been known to change their sex several times over the course of their lives. Reproduction typically occurs in late summer and fall, from August to October, although populations may also reproduce in the spring. During spawning, males discharge their sperm into the water; these sperm are combined with the eggs held at the edge of the female's mantle. The resulting larvae are immediately released back into the open ocean. A single female may release a hundred million eggs every year, although very few survive to adulthood.

Once in the water column, the larvae float freely for 4-6 weeks. Once they begin to secrete the material that will harden into their shells, they settle on the ocean floor. They remain in one place for 2-3 years while they continue to grow in size; once they reach their adult size, at about 2 years old, they begin to roam freely in search of a bed with other adults. Individuals become sexually mature at about 4 years old, and can live up to 20 years in the wild.

Conservation status: The Atlantic sea scallop has not been evaluated by the IUCN. Although populations in some localities have been reduced or eliminated due to over-harvest for human consumption, the species is thought to have a generally large and stable population.

Photos

Dann Blackwood

Jeff Goddard