Donax (bivalve)

''Donax'' is a genus of small, edible saltwater clams, marine bivalve molluscs with highly variable color patterns. The genus is sometimes known as bean clams or wedge shells; however, ''Donax'' species have different common names in different parts of the world. In the southeastern U.S. they are known as "coquina", a word that is also used for the hard limestone concretions of their shells and those of other marine organisms.

Ecology

Species of ''Donax'' live in the swash zone, sometimes in high concentrations, vertically aligned in the sand on exposed beaches, on tropical and temperate coasts worldwide. When the waves wash these small clams out of the sand, they can dig back in again quite rapidly. They are phytoplankton filter feeders. They are an import source of food for crabs, fish and shorebirds. They are sensitive to environmental conditions and are considered an indicator of beach habitat health. Some species, such as '' Donax variabilis'', migrate vertically and horizontally with changes in the tides. The genus enjoys a global distribution. These coquina clams are found extensively on the east coast beaches of Trinidad (Mayaro) and widely available in Venezuela.

Human use

''Donax'' is an edible mollusk that has been consumed since pre-historic times and is still consumed today. Numerous recipes for coquina soup have been published. Recreational foragers should follow seafood safety guidelines and shellfish harvesting restrictions, and should be aware of any harmful algal blooms that may contaminate shellfish with biotoxins. In some parts of the world ''Donax'' clams are still gathered by indigenous people as an important subsistence food.

Species

Species within the genus ''Donax'' include:

* '' Donax asper'' Hanley 1845eol Encyclopedia of Life
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* '' Donax assimilis'' Hanley, 1845
* '' Donax baliregteri'' Huber, 2012
* '' Donax bertini'' Pilsbry, 1901
* '' Donax bipartitus'' Sowerby III, 1892
* '' Donax brazieri'' Smith, 1892
* '' Donax bruneirufi'' Huber, 2012
* '' Donax burnupi'' Sowerby III, 1894
* '' Donax caelatus'' Carpenter, 1857
* '' Donax californicus'' Conrad, 1837
* '' Donax carinatus'' Hanley, 1843
* '' Donax clathratus'' Reeve, 1855
* '' Donax culter'' Hanley, 1845
* '' Donax cuneatus'' Linnaeus, 1758
* '' Donax denticulatus'' Linnaeus, 1758
* '' Donax dentifer'' Hanley, 1843
* '' Donax ecuadorianus'' Olsson, 1961
* '' Donax erythraeensis'' Bertin, 1881
* '' Donax faba'' Gmelin, 1791
* '' Donax fossor'' Say, 1822 - was thought at one time to be a northern form of '' D. variabilis''
* '' Donax francisensis'' (Cotton & Godfrey, 1938)
* '' Donax gemmula'' Morrison, 1971
* '' Donax gouldii'' Dall, 1921 - The bean clam, aka ''Donax gracilis'' Hanley 1845
* '' Donax hanleyanus'' (Philippi, 1847)
* '' Donax kindermanni'' (Philippi, 1847)
* '' Donax lubricus'' Hanley, 1845
* '' Donax madagascariensis'' Wood, 1828
* '' Donax nitidus'' Deshayes, 1855
* '' Donax obesulus'' Reeve 1854
* '' Donax obesus'' d'Orbigny, 1845
* '' Donax oweni'' Hanley, 1843
* '' Donax paxillus'' Reeve, 1854
* '' Donax punctatostriatus'' Hanley, 1843
* '' Donax rothi'' Coan, 1983
* '' Donax semistriatus'' Poli, 1795
* '' Donax serra'' Röding, 1798
* '' Donax simplex'' Sowerby III, 1897
* '' Donax sordidus'' Hanley, 1845
* '' Donax striatus'' Linnaeus, 1767
* '' Donax texasianus'' Philippi, 1847
* '' Donax townsendi'' Sowerby III, 1894
* '' Donax transversus'' Sowerby I, 1825
* '' Donax trunculus'' Linnaeus, 1758
* '' Donax variabilis'' Say, 1822 - Known in Florida under the Spanish word "coquina", is the common and colorful ''Donax'' species of the southern Atlantic and Gulf shores from Virginia to the Caribbean. This species is locally abundant on beaches with fine sand from the mid-Atlantic coast to Texas.
* '' Donax variegatus'' (Gmelin, 1791)
* '' Donax vellicatus'' Reeve, 1855
* '' Donax veneriformis'' Lamarck, 1818
* '' Donax veruinus'' Hanley, 1913
* '' Donax vittatus'' ( da Costa, 1778)

The empty small (15 to 25 mm) shells of ''Donax variabilis'' and ''Donax fossor'' may be found washed up on the beach, especially at low tide. The living animals can often be seen where the waves wash the sand around in the shallowest part of the littoral zone as the tidal level changes. These clams can use the action of waves to move themselves up and down the beach, quickly burrowing into a new location before they can be swept away (the so-called "dance of the coquina").

References

Wildlife of Sydney - Fact File - Pipi, Goolwa Cockle, Surf Clam Fact File

Further reading

The Nautilus
''On the species of Donax of Eastern North America'', March 1892, pp. 125-126

Wayne A. O'Connor & Stephan J. O'Connor, "Early ontogeny of the pipi, Donax (Plebidonax) deltoides (Donacidae; Bivalvia)"
''Molluscan Research'' 31(1): 53–56;

{{Taxonbar, from=Q2302897

Donacidae
Bivalve genera