{{redirect|Quahog|other clams|Ocean quahog|and|Southern quahog|the fictional setting of the sitcom ''Family Guy''|Quahog (Family Guy){{!}}Quahog (''Family Guy'')}} {{Short description|Mollusc species native to the Americas}} {{Speciesbox | image = LittleNeck_clams_USDA96c1862.jpg | status = G5 | status_system = TNC | status_ref = <ref name=NS>{{cite NatureServe |id=2.107614 |title=''Mercenaria mercenaria'' |access-date=23 January 2026}}</ref> | taxon = Mercenaria mercenaria | display_parents = 3 | authority = (Linnaeus, 1758) }} The '''hard clam''' ('''''Mercenaria mercenaria'''''), also known as the '''round clam''', '''hard-shell''' (or '''hard-shelled''') '''clam''', or the '''quahog''', is an edible marine bivalve 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.
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== thumb|Left valve interior of ''Mercenaria mercenaria''. The hard clam has many alternative common names, including the '''Northern quahog''', '''round clam''', and '''chowder clam'''.<ref>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.</ref>
Fish markets use specialist names for different sizes of this species of clam. The smallest legally harvestable clams are called ''countnecks'' or ''peanuts'', the next size up are ''littlenecks'', then come ''topnecks''. Above these are the ''cherrystones'', and the largest are called ''quahogs'' or ''chowder clams''.<ref name=Rice>Rice, M.A. (1992). The Northern Quahog: Biology of ''Mercenaria mercenaria''. Rhode Island Sea Grant Publication No. RIU-B-92-001, University of Rhode Island, Narragansett. 60 pp. {{ISBN|0-938412-33-7}} [https://eos.ucs.uri.edu/seagrant_Linked_Documents/riu/riub92001.pdf web link] {{Webarchive |url=https://web.archive.org/web/20220616004647/https://eos.ucs.uri.edu/seagrant_Linked_Documents/riu/riub92001.pdf |date=2022-06-16 }}.</ref>
The distinctive name ''quahog'' ({{IPAc-en|ˈ|k|oʊ|h|ɒ|ɡ}} {{respell|KOH|hog}}, {{IPAc-en|ˈ|k|w|ɔː|h|ɒ|ɡ}} {{respell|KWAW|hog}}, or {{IPAc-en|k|w|ə|ˈ|h|ɒ|ɡ}} {{respell|kwə|HOG|'}}, also spelt ''quahaug'', ''quohog''<ref> {{cite book |last1 = Ingersoll |first1 = Ernest |author-link1 = Ernest Ingersoll |year = 1900 |chapter = August 18 |title = Nature's Calendar: A Guide and Record for Outdoor Observations in Natural History |url = https://books.google.com/books?id=rH8UAAAAYAAJ |publication-place = New York |publisher = Harper & Brothers |page = 184 |access-date = 19 April 2026 |quote = [...] a comparatively small variety of shells [...]' The most common are familiar 'hard' or 'soft' clams, or quohog and maninose, as they are called locally. The quohog is a type of heavy shell that lives on the surface of the sand, ploughing its way along from place to place, and the little ribbed heart-shell is a small and pretty cousin that is common. }} </ref> or ''cohog'').<ref>{{Cite book |title=The Chambers Dictionary |publisher=Chambers |year=2003 |isbn=0-550-10105-5 |edition=9th |chapter=quahog}}</ref><ref>{{Cite book |title=Collins English Dictionary |publisher=HarperCollins |year=2018 |isbn=978-0-008-28437-4 |edition=13th |chapter=quahog}}</ref> comes from the Narragansett word {{lang | xnt | poquauhock}} (similar terms occur in Wampanoag and in some other Algonquian languages); it is attested (as 'quauhogs') in English-language usage from 1781.<ref> {{oed | quahog}}, quoting Samuel Andrew Peters: [https://books.google.com/books?id=InsFAAAAQAAJ ''A General History of Connecticut, from its first settlement under George Fenwick, Esq. to its latest period of amity with Great Britain; including a description of the country and many curious and interesting anecdotes. With an appendix, pointing out the causes of the rebellion in America; together with the particular part taken by the people of Connecticut in its promotion. By a Gentleman of the Province''], page 262. </ref><ref>{{Cite book |last =Little |first =William |url =https://archive.org/details/shorteroxfordeng0000litt/page/1723/mode/1up?q=quahog |title =The Shorter Oxford English Dictionary on Historical Principles |date =1973 |publisher =Clarendon Press |others = |isbn =978-0-19-861116-5 |edition =3rd |page =1723}}</ref><ref>{{Cite book |last =Williams |first =Roger |author-link =Roger Williams |url =https://archive.org/details/bub_gb_wOfpAPRxlVYC/ |title =A Key Into the Language of America |date =1643 |publisher =Gregory Dexter |location =London |pages =115, 152, 156}}</ref> Native polities on the eastern Atlantic seaboard manufactured valuable beads called wampum from the shells, especially from those colored purple; the species name ''mercenaria'' is related to the Latin word for "commerce".<ref>{{Cite web |author =Sea Wolf |title=Wampum |url=https://www.thundermtlenape.org/culture/wampum/ |url-status=live |archive-url =https://web.archive.org/web/20111110132254/https://www.thundermtlenape.org/culture/wampum/ |archive-date =2011-11-10 |access-date =2026-04-18 |website =Thunder Mountain Lenapé Nation |language =en-US}}</ref> {{As of | 2026}} people living in coastal New England still use Algonquian words for the clam.
In many areas where aquaculture is important, clam-farmers have bred specialized versions of these clams with distinctions for use 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.<ref> Eldridge, P.J., W. Waltz, and H. Mills. 1975. "Relative abundance of ''Mercenaria mercenaria notata'' in estuaries in South Carolina". [https://books.google.com/books?id=q3ktAQAAIAAJ ''The Veliger'', 18:396-397].</ref>
==Distribution== [[File:BoredEncrustedShell.JPG|thumb|right|An old quahog shell that has been bored (producing ''Entobia'') and encrusted after the death of the clam]] Hard clams are quite common throughout New England, north into Canada, and all down the Eastern seaboard of the United States to Florida; but they are particularly abundant between Cape Cod and New Jersey, where seeding and harvesting them is an important commercial form of aquaculture. For example, the species is an important member of the suspension-feeding, benthic fauna of the lower Chesapeake 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 the official shellfish of the U.S. state of Rhode Island and is the namesake of the fictional Rhode Island town featured in the animated sitcom Family Guy. The species has also been introduced and is farmed on the Pacific coast of North America and in Great Britain and continental Europe. It reproduces sexually by females and males shedding gametes into the water.<ref name=Rice />
==Parasite== {{main|Quahog parasite unknown}}
Quahog parasite unknown (QPX)<ref>{{cite web |title=QPX |url=http://serc.carleton.edu/microbelife/topics/marinesymbiosis/qpx.html |website=Marine Symbiosis |language=en}}</ref> is a parasite that affects the hard shell clam ''Mercenaria mercenaria''. While little is known about the disease, research is currently under way in several laboratories.<ref>{{cite journal |last1=Calvo |first1=LMR |last2=Ford |first2=S. E. |last3=Kraeuter |first3=J. N. |last4=Leavitt |first4=D. F. |last5=Smolowitz |first5=R. |last6=Burreson |first6=E. M. |title=Influence Of Host Genetic Origin And Geographic Location On Qpx Disease In Northern Quahogs (=Hard Clams), Mercenaria Mercenaria |journal=Journal of Shellfish Research |volume=26 |date=1 January 2007 |pages=109–119 |url=https://www.researchgate.net/publication/232684560|doi=10.2983/0730-8000(2007)26[109:IOHGOA]2.0.CO;2|s2cid=86080870 |hdl=1912/3240 |hdl-access=free }}</ref> This research is fueled by the need to inform 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.<ref>{{Cite journal|last1=Dove|first1=Alistair|last2=Bowser|date=28 September 2020|orig-year=9 January 2011|title=Histological Analysis of an Outbreak of QPX Disease in Wild Hard Clams Mercenaria mercenaria in New York|journal=Journal of Aquatic Animal Health|volume=16|issue=4|pages=246–250|doi=10.1577/H03-052.1}}</ref>
==Human use== thumb|Steamed clams [[File:Top neck clams.JPG|thumb|Raw top neck clams in New Jersey.]]
In coastal areas of the New England states, Long Island, and New Jersey, restaurants known as raw bars or clam bars specialize in serving littlenecks and topnecks raw on an opened half-shell, usually with a cocktail sauce with horseradish, and often with lemon. Sometimes littlenecks are steamed and dipped in butter, though not as commonly as their soft-shelled clam cousin the "steamer". Littlenecks are often found in-the-shell in sauces, soups, stews, and clams casino, or substituted for European varieties such as the cockle 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 as clam chowder, clam cakes, and stuffed clams, or are minced and mixed into dishes that use the smaller, more tender clams.
Historically, Native Americans used the quahog as a component in wampum, the shell beads exchanged in the North American fur trade.<ref>{{cite book |last=White |first=Richard |year=1991 |title=The Middle Ground: Indians, Empires, and Republics in the Great Lakes Region, 1650–1815 |url=https://books.google.com/books?id=fHLfiOZVzmMC&pg=PA97 |edition=2nd |location=New York |publisher=Cambridge University Press |page=97 |isbn=9781139495684 |oclc=772696326}}</ref> The Narragansetts used the hard clam for food and ornaments.<ref>{{Cite book |first=Kathy |last=Feeney |year=2003 |title=Rhode Island Facts and Symbols |url=https://books.google.com/books?id=Nu_a1V1CVaEC&pg=PA18 |edition=Revised and Updated |others=Albert T. Klyberg (consultant) |location=Mankato, Minn. |publisher=Capstone Press |pages=18–19 |isbn=9780736822701 |oclc=51204649}}</ref>
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.<ref name="wash">{{cite web |title=Paralytic Shellfish Poisoning |url=https://www.doh.wa.gov/CommunityandEnvironment/Shellfish/RecreationalShellfish/Illnesses/Biotoxins/ParalyticShellfishPoison |publisher=Washington State Department of Health |access-date=10 August 2020 |date=2020}}</ref><ref name="bc-cdc">{{cite web |title=Paralytic Shellfish Poisoning |url=http://www.bccdc.ca/health-info/diseases-conditions/paralytic-shellfish-poisoning |publisher=Centre for Disease Control, British Columbia Health Services Authority |access-date=10 August 2020 |date=2020}}</ref> Filter-feeding shellfish are affected, such as clams, oysters, and mussels.<ref name=wash/><ref name=bc-cdc/> As they filter microorganisms, clams ingest ''K. brevis'' algae. This algae accumulates in the clams' tissues and is toxic to humans when they are consumed. The toxin affects the human central nervous system.<ref name=wash/> Eating contaminated shellfish, raw or cooked, can be fatal.<ref name=wash/> 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.<ref name=wash/>
==References== {{Reflist}}
{{Edible molluscs}} {{taxonbar|from=Q2279087}}
{{DEFAULTSORT:Hard Clam}} Category:Clams Category:Veneridae Category:Marine molluscs of North America Category:Molluscs of the Atlantic Ocean Category:Molluscs of the United States Category:Molluscs of Mexico Category:Fauna of the Northeastern United States Category:Fauna of the Southeastern United States Category:Bivalves described in 1758 Category:Animal taxa named by Carl Linnaeus Category:Symbols of Rhode Island Category:Cuisine of Rhode Island Category:Native American culture<!--please keep this category, as they were used for than just seafood--> Category:Seafood in Native American cuisine <ref>Eversole, A. (1987, August). Special Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (South Atlantic) [Review of Special Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (South Atlantic)]. Google Books. https://books.google.com/books?hl=en&lr=&id=PvuECX0o7wMC&oi=fnd&pg=PR6&dq=what+do+hard+clams+eat&ots=QsSbK-dY6X&sig=gar5L8ow9qxr9ZmawA1I1xP-tJg#v=onepage&q=what%20do%20hard%20clams%20eat&f=false</ref>