Atlantic Calico Scallop (also known as Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled), whole shell, fan shape
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled), whole shell, fan shape
Family
Pectinidae (Scallop family)
Size
Approximately 2 to 2.5 inches in width, which is average to slightly large for this species. Adults typically range from 1.5 to 3 inches.
Color & Pattern
This specimen is heavily sun-bleached and weathered, showing a pale whitish-grey exterior with faint traces of original orange or brownish mottling near the umbo. Typically, living specimens exhibit a vibrant 'calico' pattern of reddish, brownish, or purplish patches on a lighter background, but this beach-worn shell has lost its characteristic bright colors.
Rarity
Common; frequently found washed ashore on beaches throughout its native range, especially along the Gulf coast of Florida.
Habitat
Inhabits shallow marine waters, typically found in sandy or shelly substrates, often associated with seagrass beds 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 Brazil.
Description
A classic fan-shaped bivalve shell featuring symmetrical, rounded valves with prominent, well-defined radial ribs radiating from the hinge. The ears (auricles) at the hinge are somewhat unequal in size, typical of the scallop family. The exterior texture is slightly ridged and rough from wave wear, while the margin is scalloped to match the internal ribbing.
Key Features
Nearly equilateral fan shape, prominent radial ribs (usually around 18 to 22), distinct unequal auricles at the hinge, and a rounded ventral margin.
Collector Value
Low to moderate commercial value due to its abundance. While beach-worn specimens like this are common and hold little monetary value, prime gem-quality specimens with vibrant, intact color patterns are popular in shell crafts and beginner collections.
Condition Notes
Fair condition; the shell is structurally intact as a single valve, but it is heavily sun-bleached, worn down by surf tumbling, and has lost its original coloration and glossy finish. Collectibility grade is Fair.
Interesting Facts
Unlike many bivalves that burrow and stay stationary, calico scallops can swim short distances by rapidly clapping their valves together to expel water, using a simple row of dozens of tiny blue eyes along their mantle edge to detect motion and shadows.
Ecological Role
Calico scallops are important filter feeders, helping to clear organic particles from the water column. They serve as a vital food source for numerous marine predators including fish, rays, sea turtles, and octopuses. They are also commercially fished for human consumption in certain regions.
Similar Species
Atlantic Bay Scallop (Argopecten irradians), which tends to be slightly more inflated with slightly fewer and broader ribs, and the Rough Scallop (Aequipecten muscosus), which features more pronounced scaly ribs.
Beach Finding Tips
Look along high-tide lines and shell deposits on sandy beaches after storm events or strong onshore winds. Gulf Coast beaches in Florida are particularly famous for yielding an abundance of scallop shells.