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), whole shell valve, fan-shaped
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled), whole shell valve, fan-shaped
Family
Pectinidae (Scallop family)
Size
Approximately 1 inch in width, which is typical for a juvenile or average adult specimen found on Florida beaches. Species range is generally 1 to 2.5 inches.
Color & Pattern
Uniform stark white due to sun-bleaching. Typically, living specimens feature a mottled or checkered pattern of reddish-brown, purple, orange, or yellow on a white or cream background, hence the name 'calico'. Interior is white with a purple-tinted hinge scar.
Rarity
Common (found regularly on beaches throughout its range, especially after storms or winter cold fronts)
Habitat
Shallow subtidal zones to moderately deep waters, typically residing in sandy or shelly substrates, often found in seagrass beds from the low tide mark down to about 150 feet.
Geographic Range
Western Atlantic Ocean, from North Carolina southward through the Florida Keys, the Gulf of Mexico, and the Caribbean Sea.
Description
A charming, fan-shaped bivalve shell featuring prominent, rounded radial ribs and a distinctly asymmetrical set of 'ears' (auricles) flanking the umbo at the hinge. The margin is deeply scalloped, matching the internal ridging, and the exterior exhibits tactile, rough growth lines across the robust ribs.
Key Features
Unequal or asymmetrical ears at the hinge line (characteristic of the genus Argopecten) and 18 to 22 strong, rounded radial ribs running from the umbo to the ventral margin.
Collector Value
Low to moderate value for individual beach-worn specimens. They are extremely popular for shell crafts, jewelry-making, and casual beachcombing collections rather than high-end conchology, usually sold by the handful in shell shops.
Condition Notes
Worn and completely sun-bleached to a chalky white, indicating it has spent considerable time tumbled in the surf and exposed on the beach. Missing its natural colorful pattern. Condition is Fair to Good as a beach find, with minor chipping along the delicate marginal edges.
Interesting Facts
Unlike most bivalves that burrow or cement themselves, Calico Scallops are capable of active swimming. By rapidly clapping their valves together, they expel water to jet-propel themselves away from predators like starfish and sea urchins. They also possess dozens of tiny, functional blue eyes along the mantle edge.
Ecological Role
As suspension feeders, they filter phytoplankton from the water column, helping to maintain water clarity. They serve as an important food source for marine carnivores including fish, rays, sea turtles, and octopuses. Populations fluctuate wildly from year to year based on environmental conditions.
Similar Species
Atlantic Bay Scallop (Argopecten irradians) - can be distinguished by having slightly flatter valves and fewer, broader ribs (usually 17 or fewer), though they overlap significantly in range and general appearance.
Beach Finding Tips
Look along high tide wrack lines, especially on Gulf Coast beaches like Lido Beach in Florida after windy days or passing cold fronts. Sifting through shell piles where fine sand meets coarser shell hash often reveals intact valves.
Notes
Lido beach