Calico Scallop (also known as the Atlantic Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled clam), whole single valves, fan-shaped disc
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled clam), whole single valves, fan-shaped disc
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2 inches in width and length, which is average for this species. Adults typically range from 1.5 to 2.5 inches.
Color & Pattern
The visible exteriors are predominantly whitish to cream-colored with subtle hints of pinkish-red blotches, suggesting they are somewhat sun-bleached or weathered variants of the typically highly patterned calico scallop, which usually features mottled reddish, brown, or purplish patches on a lighter background. The interior is smooth and whitish.
Rarity
Very Common, frequently washed up on beaches throughout its native range, especially along the coasts of Florida.
Habitat
Shallow marine waters, typically found in sandy substrates, seagrass beds, and offshore shoals from the low intertidal zone down to depths of about 150 feet.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina down through Florida, the Gulf of Mexico, the Caribbean, and south to the West Indies and parts of South America.
Description
These charming, fan-shaped bivalve shells exhibit strong, symmetrical radial ribs radiating from a pointed umbo at the hinge. The margins are distinctly scalloped and crenulated, matching the external ribs. The surface texture is finely ribbed, creating a classic fluted appearance characteristic of the scallop family.
Key Features
Symmetrical fan-shaped valve, approximately 18 to 22 rounded to slightly angular radial ribs, and asymmetrical auricles (ears) at the hinge line, which is typical of the genus Argopecten.
Collector Value
Low to moderate value. While extremely popular among casual beachcombers and crafters, commercial abundance makes individual beach specimens inexpensive, usually valued at a few cents to a dollar, though pristine, brightly colored specimens with both matching valves intact are more desirable.
Condition Notes
Good condition. The valves are intact with well-defined margins and prominent ribs, though they show mild fading and slight wear consistent with beach-worn specimens, earning a 'Good' collectibility grade.
Interesting Facts
Unlike many bivalves that burrow and remain sedentary, calico scallops are capable of swimming short distances by rapidly clapping their valves together to expel water, allowing them to escape predators like sea stars and crabs. They also possess dozens of tiny, bright blue eyes along the mantle edge that can detect light and shadow.
Ecological Role
Calico scallops serve as important filter feeders, helping to clear the water column of phytoplankton and suspended organic matter. They form a vital link in the marine food web, serving as prey for fish, rays, sea turtles, and marine mammals.
Similar Species
Atlantic Bay Scallop (Argopecten irradians), which tends to be slightly larger with fewer, flatter ribs (usually 17 or fewer) and a slightly different geographical and depth preference.
Beach Finding Tips
Look along high-tide wrack lines on sandy ocean-facing beaches, particularly after storms or high winds. Florida's Atlantic and Gulf coasts—especially Sanibel Island and areas near Cape Canaveral—are legendary for finding these shells.