{{Short description|Species of bivalve}} {{Speciesbox | name = Brook floater | image = Alasmidonta varicosa - Springfield Science Museum - Springfield, MA - DSC03461.JPG | status = VU | status_system = IUCN3.1 | status_ref =<ref name="iucn status 17 November 2021">{{cite iucn |author=Woolnough, D. |author2=Bogan, A.E. |date=2017 |title=''Alasmidonta varicosa'' |volume=2017 |article-number=e.T781A69490583 |doi=10.2305/IUCN.UK.2017-3.RLTS.T781A69490583.en |access-date=17 November 2021}}</ref> | status2 = G3 | status2_system = TNC | status2_ref = <ref name=NS>{{cite NatureServe |id=2.111437 |title=''Alasmidonta varicos'' |access-date=24 December 2025}}</ref> | genus = Alasmidonta | species = varicosa | authority = (Lamarck, 1819) | synonyms = ''Alismodonta varicosa'' (Lamarck, 1819) }} {{Commons category|Alasmidonta varicosa}}
The '''brook floater'''<ref name="mass.gov">{{cite web|last=Nedeau|first=Ethan|url=http://www.mass.gov/eea/docs/dfg/nhesp/species-and-conservation/nhfacts/alasmidonta-varicosa.pdf|archive-url=https://web.archive.org/web/20170921133437/http://www.mass.gov/eea/docs/dfg/nhesp/species-and-conservation/nhfacts/alasmidonta-varicosa.pdf|archive-date=21 September 2017|date=1 November 2009|orig-date=Originally published as "Brook Floater Fact Sheet" in December 2007|title=Brook Floater|publisher=mass.gov}}</ref> or '''swollen wedgemussel''',<ref>{{cite web|url=https://www.mass.gov/news/species-spotlight-brook-floater|title=News Species Spotlight: Brook floater|author=MassWildlife's Natural Heritage & Endangered Species Program|date=28 February 2020|website=Division of Fisheries and Wildlife|publisher=Commonwealth of Massachusetts|access-date=7 August 2023}}</ref> '''''Alasmidonta varicosa''''', is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. It measures 25.1 mm to 80.2 mm in length<ref>{{Cite journal|author=Janet L. Clayton, Craig W. Stihler and Jack L. Wallace|title=Status of and Potential Impacts to the Freshwater Bivalves (Unionidae) in Patterson Creek, West Virginia|journal=Northeastern Naturalist|volume=8|issue=2|pages=179–188|date=2001|doi=10.1656/1092-6194(2001)008[0179:SOAPIT]2.0.CO;2}}</ref> although other research also suggests it rarely exceeds three inches (75 mm).<ref name="mass.gov"/>
==Distribution== This species is found in Canada (New Brunswick and Nova Scotia)<ref>Caroline Caissie, Dominique Audet, [http://shediacbaywatershed.com/wp-content/uploads/2013/08/Freshwater-mussel-Inventory-in-Shd-and-Scd-Rivers-FWM_Final-Report-March_2006.pdf Freshwater Mussel Inventory in the Shediac and Scoudouc Rivers] {{Webarchive|url=https://web.archive.org/web/20150624133003/http://shediacbaywatershed.com/wp-content/uploads/2013/08/Freshwater-mussel-Inventory-in-Shd-and-Scd-Rivers-FWM_Final-Report-March_2006.pdf |date=2015-06-24 }}, New Brunswick Wildlife Trust Fund, 2006, p. 12. Accessed August 21, 2014</ref> and northeastern United States (Connecticut, Georgia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Vermont, Virginia and West Virginia);<ref>{{cite web|url=http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=F03D#conservationPlans|title=Brook floater (Alasmidonta varicosa)|publisher=ecos.fws.gov|access-date=June 23, 2015}}</ref> It was formerly found in Rhode Island and four watersheds in Massachusetts but are now extinct in Rhode Island and almost extinct in Massachusetts.<ref name="mass.gov"/> 1897 Research by Arnold Edward Ortmann showed it to be common in the Delaware and Susquehanna Rivers.<ref>{{cite book |author=Arnold Edward Ortmann |date=1897 |title=Collected papers, Volume 1 |url=https://books.google.com/books?id=GnYuAAAAIAAJ&q=Alasmidonta+varicosa&pg=RA1-PA370 |publisher=self-published |access-date=June 23, 2015}}</ref>
==Habitat and behavior== This mussel lives in high relief streams, under boulders and in sand. Research has shown that it is highly sensitive to increased thermal temperature.<ref>{{cite web|url=http://www.co2science.org/articles/V16/N14/B1.php|title=Thermal History Impacts Thermal Tolerance of Freshwater Mussels|publisher=co2science.org|access-date=June 23, 2015}}</ref> It associates with longnose and eastern blacknose dace, golden shiner, pumpkinseed, slimy sculpin and yellow perch.<ref name="ConnecticutWildlife">{{cite book |last=Hammerson |first=Geoffrey A. |date=2004 |title=Connecticut Wildlife: Biodiversity, Natural History, and Conservation |url=https://books.google.com/books?id=FWc3zDq9P10C&q=Alasmidonta+varicosa&pg=PA205 |publisher=University Press of New England |page=205 |isbn=978-1-58465-369-1 |access-date=June 23, 2015}}</ref>
==Survival threats and conservation== The brook floater is sensitive to habitat loss for development, dams and road crossings, pollution, summer droughts, trampling, sedimentation, flow alteration, and low oxygen conditions. Hybridization with elktoe (''Alasmidonta marginata''), a longtime ally, has also been shown to be a threat.<ref>{{Cite journal|title=Changes in the Distribution of Freshwater Mussels (Unionidae) in the Upper Susquehanna River Basin, 1955–1965 to 1996–1997|journal=The American Midland Naturalist|volume=142|issue=2|page=328|doi=10.1674/0003-0031(1999)142[0328:CITDOF]2.0.CO;2|year=1999|last1=Strayer|first1=David L.|last2=Fetterman|first2=Andrew R.}}</ref> Research has also shown the population is highly fragmented, low in density, prone to mortality due to old age and there are also low chances of longevity and viable reproduction.<ref name="mass.gov"/> Trematoda ''rhopalocercous cercaria'' is a parasite of the brook floater.<ref>{{cite journal|jstor=3223759|title=Cercaria tiogae Fischthal, 1953, a Rhopalocercous Form from the Clam, Alasmidonta varicosa (Lamarck)|journal=Transactions of the American Microscopical Society|volume=73|issue=2|pages=210–215|date=1954|last1=Fischthal|first1=Jacob H.|doi=10.2307/3223759}}</ref> Current research shows populations that were large and widespread have declined by 50% to 95% to almost extinct.<ref>{{cite web|url=http://rcngrants.org/content/conservation-status-brook-floater-mussel-alasmidonta-varicosa-northeastern-united-states|title=The conservation status of the brook floater mussel, Alasmidonta varicosa, in the Northeastern United States: trends in distribution, occurrence, and condition of populations|publisher=rcngrants.org|access-date=June 23, 2015}}</ref>
While the IUCN lists it as Vulnerable, the states of New Jersey, Virginia, Massachusetts and New Hampshire<ref name="mass.gov"/> all list it as Endangered,<ref>{{cite book |author=Thomas F. Nalepa, Don W. Schloesser |date=2013 |title=Quagga and Zebra Mussels: Biology, Impacts, and Control, Second Edition |url=https://books.google.com/books?id=Cy7OBQAAQBAJ&q=Alasmidonta+varicosa&pg=PA206 |publisher=CRC Press |page=206 |isbn=978-1-4398-5437-2 |access-date=June 23, 2015}}</ref> Threatened in Vermont, Maine and New York,<ref>{{cite book |last=McBroom |first=Matthew |date=2013 |title=The Effects of Induced Hydraulic Fracturing on the Environment: Commercial Demands vs. Water, Wildlife, and Human Ecosystems |url=https://books.google.com/books?id=U6GNAgAAQBAJ&q=Alasmidonta+varicosa&pg=PA285 |publisher=CRC Press |page=285 |isbn=978-1-926895-83-3 |access-date=June 23, 2015}}</ref> Rare/Endangered in Connecticut,<ref name="ConnecticutWildlife"/> Extinct in Rhode Island and "Species of Special Concern" by the federal government.<ref>{{cite book |author=Bruce E. Beans, Larry Niles |date=2003 |title=Endangered and Threatened Wildlife of New Jersey |url=https://books.google.com/books?id=AihUrC8PfOkC&q=Alasmidonta+varicosa&pg=PA257 |publisher=Rutgers University Press |page=257 |isbn=978-0-8135-3209-7 |access-date=June 23, 2015}}</ref>
==References== {{Reflist}}
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Category:Alasmidonta Category:Bivalves described in 1819 Category:Taxonomy articles created by Polbot
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