Abra aequalis

Abra aequalis
Temporal range:
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Cardiida
Family: Semelidae
Genus: Abra
Species:
A. aequalis
Binomial name
Abra aequalis
(Say, 1822)
Synonyms
  • Amphidesma aequalis Say, 1822
  • Amphidesma equalis Say, 1822 in Conrad, 1845
  • Abra nuculiformis Conrad, 1867
  • Abra equalis (Say, 1822)

Abra aequalis, also known as the Atlantic abra, is a species of marine bivalve found in the west Atlantic Ocean.

Taxonomy

Abra aequalis was first scientifically described under the name Amphidesma aequalis by Thomas Say in 1822.[1][2] In 1858, it was transferred to the genus Abra by Francis Simmons Holmes in an account of recent fossils from South Carolina.[3][4]

Abra is classified in the family Semelidae, in the same order (Cardiida) as the cockle shells.[2] Its common names include the "Atlantic abra"[5][6] and the "common Atlantic furrow-shell".[2]

Description

Abra aequalis is a small species with plain, white, mostly smooth shells which are slightly round, but triangular in outline.[3][1] Due to their small size (about 7 millimetres [0.28 in]), A. aequalis is one of several unremarkable, similar-looking species fondly called "little white clams" by amateur shell collectors.[5] The shells are quite thin and fragile, and Robert Parr Whitfield summarized their appearance thus: "it is a very neat and pretty shell, and moderately abundant".[7]

Distribution, habitat, and ecology

Abra aequalis is found along the southeastern coast of the United States, the Gulf of Mexico, the Caribbean Sea, and the coast of southeastern Brazil.[2] The Global Biodiversity Information Facility records observations from as far north as Long Island. It is abundant along the American coast, around Florida, and is also found around Mexico and the Caribbean Islands. In South America, it is found on the coasts of Venezuela, Suriname, and Panama, as well as on the Brazilian coast from São Paulo to Pelotas.[8]

A. aequalis is usually found in shallow waters of depth less than 73 metres (240 ft).[8] It has also been observed on seamounts and underwater knolls.[2] A 1973 study off Sapelo Island, United States, found that A. aequalis became the dominant species in spring.[9] A. aequalis is the most significant food source for Luidia senegalensis in Florida.[10]

Fossil record

The fossil record of Abra aequalis is reasonably well documented. It has been found as fossils abundantly in the Quaternary (current) period in many countries and in the Pliocene of several.[11] It is also known from the Miocene.[7][12]

References

  1. ^ a b Say, Thomas (1822). "An account of some of the marine shells of the United States". Journal of the Academy of Natural Sciences of Philadelphia. 2: 307.
  2. ^ a b c d e Bieler R, Bouchet P, Gofas S, Marshall B, Rosenberg G, La Perna R, Neubauer TA, Sartori AF, Schneider S, Vos C, ter Poorten JJ, Taylor J, Dijkstra H, Finn J, Bank R, Neubert E, Moretzsohn F, Faber M, Houart R, Picton B, Garcia-Alvarez O (eds.). "Abra aequalis (Say, 1822)". MolluscaBase. World Register of Marine Species. Retrieved 2026-01-03.
  3. ^ a b Gardner, Julia Anna (1943). Mollusca from the Miocene and Lower Pliocene of Virginia and North Carolina. U.S. Government Printing Office. pp. 104–5.
  4. ^ Holmes, Francis Simmons (1860). Post-Pleiocene Fossils of South-Carolina. Russell & Jones. p. 50.
  5. ^ a b Leal, José (2020-06-19). "Shell of the Week: The Atlantic Abra". Bailey-Matthews National Shell Museum. Retrieved 2026-01-03.
  6. ^ "Atlantic Abra (Abra aequalis)". www.fws.gov. U.S. Fish & Wildlife Service. Retrieved 2026-01-03.
  7. ^ a b Whitfield, Robert Parr (1894). Mollusca and Crustacea of the Miocene Formations of New Jersey. U.S. Government Printing Office.
  8. ^ a b "Abra aequalis (Say, 1822)". Global Biodiversity Information Facility. Retrieved 2026-01-03.
  9. ^ Smith, K. L. (1973). "Respiration of a Sublittoral Community". Ecology. 54 (5): 1065–1075. Bibcode:1973Ecol...54.1065S. doi:10.2307/1935572. ISSN 0012-9658. JSTOR 1935572.
  10. ^ Halpern, J. A. (1970). "Growth Rate of the Tropical Sea Star Luidia senegalensis (Lamarck)" (PDF). Bulletin of Marine Science. 20 (3): 626–633. Archived 2026-02-09 at the Wayback Machine
  11. ^ "Abra aequalis Say 1822". Paleobiology Database.
  12. ^ "Abra aequalis". Neogene Atlas of Ancient Life. Retrieved 2026-01-03.
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