Hard clam

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Hard clam
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Venerida
Superfamily: Veneroidea
Family: Veneridae
Genus: Mercenaria
Species:
M. mercenaria
Binomial name
Mercenaria mercenaria

The hard clam (Mercenaria mercenaria), also known as the round clam, hard-shell (or hard-shelled) clam, or the quahog,

mollusk that is native to the eastern shores of North America and Central America from Prince Edward Island to the Yucatán Peninsula. It is one of many unrelated edible bivalves that in the United States are frequently referred to simply as clams. Older literature sources may use the systematic name Venus mercenaria; this species is in the family Veneridae
, the venus clams.

Confusingly, the "ocean quahog" is a different species, Arctica islandica, which, although superficially similar in shape, is in a different family of bivalves: it is rounder than the hard clam, usually has a black periostracum, and there is no pallial sinus in the interior of the shell.

Alternative names

Left valve interior of Mercenaria mercenaria.

The hard clam has many alternative common names. It is also known as the Northern quahog, round clam, or chowder clam.[1]

In fish markets, there are specialist names for different sizes of this species of clam. The smallest legally harvestable clams are called countnecks or peanuts, next size up are littlenecks, then topnecks. Above that are the cherrystones, and the largest are called quahogs or chowder clams.[2]

The most distinctive of these names is quahog (

Wampanoag and some other Algonquian languages; it is first attested in North American English in 1794.[5][6] Native polities on the eastern Atlantic seaboard made valuable beads called wampum from the shells, especially those colored purple; the species name mercenaria is related to the Latin
word for commerce. Today people living in coastal New England still use Algonquian words for the clam, as they have done for thousands of years.

In many areas where aquaculture is important, clam farmers have bred specialized versions of these clams with distinctions needed for them to be distinguished in the marketplace. These are quite similar to common "wild type" Mercenaria clams, except that their shells bear distinctive markings. These are known as the notata strain of quahogs, which occur naturally in low numbers wherever quahogs are found.[7]

Distribution

An old quahog shell that has been bored (producing Entobia) and encrusted after the death of the clam

Hard clams are quite common throughout

benthic fauna of the lower Chesapeake Bay
.

gametes into the water.[2]

Parasite

Quahog parasite unknown (QPX)

aquaculturists, who suffer financially because of the mortality rates in clams that QPX inflicts and the ensuing years in which runs must be left fallow to clear the disease. It was discovered along the coast of Cape Cod
, Massachusetts in 1995.

Quahog parasite X (or quahog parasite unknown [QPX]) disease of the hard clam Mercenaria mercenaria is caused by a poorly known protistan parasite. Its DNA sequence analysis places the QPX parasite among the

thraustochytrid stramenopiles. The QPX parasite is unicellular and possesses at least one flagellum, like most other stramenopile organisms. Thraustochytrids are common protists in marine sediments and the water column, but only a few thraustochytrids are known as parasites of marine animals. Although QPX disease was first recorded on the Atlantic coast of Canada in the early 1960s, it did not become a major economic problem until its appearance in cultured clams at Prince Edward Island, Massachusetts in 1992, and Virginia in 1997. Infected clams are characterized by the presence of blisters or pustules in the mantle and later by gaping and death.[10]

Human use

Steamed clams
Raw top neck clams in New Jersey.

In coastal areas of the New England states, Long Island, and New Jersey, restaurants known as

clam cakes, and stuffed clams
, or are minced and mixed into dishes that use the smaller, more tender clams.

Historically,

Narragansetts used the hard clam for food and ornaments.[12]

A population of hard clams exists in Southampton Water in Hampshire, England. Originally bred in the warm water outflows at Southampton Power Station for use as eel bait, the population became self-sustaining and can now be found in Southampton Water and has also spread to Portsmouth Harbour and Langstone Harbour.

Clams and red tide

The term "

red tide" refers to an accumulation of a toxin, such as saxitoxin, produced by marine algae.[13][14] Filter-feeding shellfish are affected, such as clams, oysters, and mussels.[13][14] As they filter microorganisms, clams ingest K. brevis algae. This algae accumulates in the clams' tissues and be toxic to humans when they are consumed. The toxin affects the human central nervous system.[13] Eating contaminated shellfish, raw or cooked, can be fatal.[13] Some other kinds of algal blooms make the seawater appear red, but red tide blooms do not always discolor the water, nor are they related to tides.[13]

Notes

  1. ^ For the pronunciation and variant spellings of quahog, as well as for other alternative common names, see the appropriate section.

References

  1. ^ Harte, M. E. 2001. "Systematics and taxonomy, Chapter 1", pp. 3–51, in Kraeuter, J. N. and M. Castagna (eds.) "Biology of the Hard Clam", Developments in Aquaculture and Fisheries Science, Vol. 31. Elsevier Science B.V.: New York.
  2. ^ .
  3. .
  4. .
  5. ^ "Quahaug, quahog", in Shorter Oxford English Dictionary, 3rd ed (Oxford: Clarendon Press, 1973)
  6. A Key Into the Language of America
    . London: Gregory Dexter, 1643.
  7. ^ Eldridge, P.J., W. Waltz, and H. Mills. 1975. Relative abundance of Mercenaria mercenaria notata in estuaries of South Carolina. Veliger 18:396-397.
  8. ^ "QPX". Marine Symbiosis.
  9. S2CID 86080870
    .
  10. .
  11. .
  12. .
  13. ^ a b c d e "Paralytic Shellfish Poisoning". Washington State Department of Health. 2020. Retrieved 10 August 2020.
  14. ^ a b "Paralytic Shellfish Poisoning". Centre for Disease Control, British Columbia Health Services Authority. 2020. Retrieved 10 August 2020.