Coquina clam

For more information on coquina (clam), visit Britannica.com.

Donax variabilis

ORDER

Veneroida

FAMILY

Donacidae

TAXONOMY

Donax variabilis (Say, 1822), Georgia and eastern Florida, United States.

OTHER COMMON NAMES

English: Bean clam, butterfly clam, donax clam, southern coquina, variable coquina; French: Donax de Floride; Japanese: Kocyo-naminoko.

PHYSICAL CHARACTERISTICS

Shell is unequally triangular, with a subcentral umbo. The shorter anterior end is radially sculptured; the shell is otherwise smooth, not gaping. Polychromic, in wide variety of colors including white, yellow, orange, pink, purple, and blue; frequently radially striped. Interior is non-nacreous, often deep purple, with a denticulate (finely toothed) margin. Grows as long as 1 in (20 mm).

DISTRIBUTION

Eastern coast of North America from Chesapeake Bay to Florida; Gulf of Mexico to Yucatan.

HABITAT

Infaunal, on intertidal sandy beaches with wave action, sometimes numbering in thousands per square meter.

BEHAVIOR

Intertidal migration behavior is well documented. Coquina clams use their muscular foot to repeatedly rebury themselves after being washed from sand by incoming waves. Migration is both vertical (between tide levels) and horizontal (along the beach).

FEEDING ECOLOGY AND DIET

Filter feeder.

REPRODUCTIVE BIOLOGY

Dioecious, broadcast spawner. Life span is about 1–2 years.

CONSERVATION STATUS

Not listed by the IUCN.

SIGNIFICANCE TO HUMANS

Human food source, locally in "coquina broth." Coquina rock, a subfossil conglomerate of Donax shells and sand, was used as a building material by early Spanish settlers in North America. More recently, it has been used in ornamental landscaping.