| Hard clam | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Bivalvia |
| Order: | Venerida |
| Superfamily: | Veneroidea |
| Family: | Veneridae |
| Genus: | Mercenaria |
| Species: | M. mercenaria |
| Binomial name | |
| Mercenaria mercenaria | |
Thehard clam (Mercenaria mercenaria), also known as theround clam,hard-shell (orhard-shelled)clam, or thequahog,[a] is an ediblemarinebivalvemollusk that is native to the eastern shores ofNorth America andCentral America fromPrince Edward Island to theYucatán Peninsula. It is one of many unrelated edible bivalves that in the United States are frequently referred to simply asclams. Older literature sources may use the systematic nameVenus mercenaria; this species is in the familyVeneridae, 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 blackperiostracum, and there is nopallial sinus in the interior of the shell.
The hard clam has many alternativecommon 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 calledcountnecks orpeanuts, next size up arelittlenecks, thentopnecks. Above that are thecherrystones, and the largest are calledquahogs orchowder clams.[2]
The most distinctive of these names isquahog (/ˈkoʊhɒɡ/KOH-hog,/ˈkwɔːhɒɡ/KWAW-hog, or/kwəˈhɒɡ/kwə-HOG, also speltquahaug,quohog orcohog).[3][4] The word comes from theNarragansett word "poquauhock", which is similar inWampanoag and some otherAlgonquian languages; it is first attested in North American English in 1794.[5][6] Native polities on the eastern Atlantic seaboard made valuable beads calledwampum from the shells, especially those colored purple; the species namemercenaria is related to theLatin 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 whereaquaculture 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 thenotata strain of quahogs, which occur naturally in low numbers wherever quahogs are found.[7]
WesternAtlantic Ocean:Hard clams are quite common throughoutNew England, north intoCanada, and all down theEastern seaboard of theUnited States toFlorida; but they are particularly abundant betweenCape Cod andNew Jersey, where seeding and harvesting them is an important commercial form ofaquaculture. For example, the species is an important member of the suspension-feeding,benthic fauna of the lowerChesapeake Bay.
Rhode Island is situated right in the middle of "quahog country" and has supplied a quarter of the U.S.'s total annual commercial quahog catch. The quahog is theofficial shellfish of the U.S. state ofRhode Island and is the namesake of the fictional Rhode Island town featured in the animated sitcomFamily Guy. The species has also beenintroduced and is farmed on thePacific coast of North America and inGreat Britain and continentalEurope. It reproduces sexually by females and males sheddinggametes into the water.[2]
Shallow water: found intertidally on sand flats, at low tide. Hard Clams are found spread throughout the South Atlantic Region. They can be found at a depth of 15 meters or more.
Quahog parasite unknown (QPX)[8] is aparasite that affects the hard shell clamMercenaria mercenaria. While little is known about the disease, research is currently under way in several laboratories.[9] This research is fueled by the need to informaquaculturists, who suffer financially because of the mortality rates in clams that QPX inflicts and the ensuing years in which runs must be leftfallow to clear the disease. It was discovered along the coast ofCape Cod, Massachusetts in 1995.
Quahog parasite X (or quahog parasite unknown [QPX]) disease of the hard clamMercenaria mercenaria is caused by a poorly known protistan parasite. Its DNA sequence analysis places the QPX parasite among thethraustochytridstramenopiles. 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]
In coastal areas of the New England states, Long Island, and New Jersey, restaurants known asraw bars or clam bars specialize in serving littlenecks and topnecks raw on an opened half-shell, usually with acocktail sauce withhorseradish, and often withlemon. Sometimes littlenecks are steamed and dipped in butter, though not as commonly as theirsoft-shelled clam cousin the "steamer". Littlenecks are often found in-the-shell in sauces, soups, stews, andclams casino, or substituted for European varieties such as thecockle in southern European seafood dishes. The largest clams are quahogs or chowders and cherrystones; they have the toughest meat and are used in such dishes asclam chowder,clam cakes, andstuffed clams, or are minced and mixed into dishes that use the smaller, more tender clams.
Historically,Native Americans used the quahog as a component inwampum, the shell beads exchanged in theNorth American fur trade.[11] TheNarragansetts used the hard clam for food and ornaments.[12]
A population of hard clams exists inSouthampton Water inHampshire,England. Originally bred in the warm water outflows atSouthampton Power Station for use as eel bait, the population became self-sustaining and can now be found in Southampton Water and has also spread toPortsmouth Harbour andLangstone Harbour.
The term "red tide" refers to an accumulation of a toxin, such assaxitoxin, produced by marine algae.[13][14] Filter-feeding shellfish are affected, such as clams, oysters, and mussels.[13][14] As they filter microorganisms, clams ingestK. brevis algae. This algae accumulates in the clams' tissues and is toxic to humans when they are consumed. The toxin affects the humancentral 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]