Coquina Clam (Butterfly Shell, Variable Coquina)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Coquina family) · Bivalve, whole shell, wedge-shaped
Species
Donax variabilis
Shell Type
Bivalve, whole shell, wedge-shaped
Family
Donacidae (Coquina family)
Size
Approximately 0.5 to 1 inch, which is average for this species. Adults typically range from 0.5 to 1 inch in length.
Color & Pattern
Extremely variable coloration ranging from pure white, yellow, orange, pink, purple, to blue, often with radial bands or zigzag patterns. The specimens shown are primarily solid white or pale cream with slight yellowish umbones. Colors are completely natural.
Rarity
Very Common
Habitat
Intertidal zone of high-energy sandy ocean beaches, specifically in the swash zone where waves break and wash up on the shore. Marine species.
Geographic Range
Western Atlantic Ocean, from Virginia south through Florida, the Gulf of Mexico, and into the Caribbean.
Description
A small, wedge-shaped bivalve with a smooth to finely sculptured surface. The posterior end is slightly truncated while the anterior is elongated. The margins are finely toothed internally, and the shell possesses a glossy, porcelain-like finish.
Key Features
Wedge shape, smooth glossy exterior, fine internal margin crenulations, and remarkable color polymorphism.
Collector Value
Low monetary value due to extreme abundance, but highly popular for shell craft and recreational beach collections due to their vibrant rainbow of colors.
Condition Notes
Good to Fine condition. Intact single valves exhibiting natural coloration with minor wear near the umbo.
Interesting Facts
Coquina clams are famous for their ability to rapidly burrow back into the sand using their muscular foot as waves recede. They filter feed on microscopic plankton and detritus.
Ecological Role
Serves as a crucial food source for shorebirds, fish, and crabs, linking primary producers to higher trophic levels in sandy beach ecosystems.
Similar Species
Donax denticulatus (Caribbean Coquina) and Donax fossor (Eastern Little Coquina), distinguished by subtle differences in geographic range and marginal teeth.
Beach Finding Tips
Look in the wet sand of the swash zone on sandy ocean beaches just as a wave recedes, watching for tiny bubbling or shifting in the sand where they burrow.