Brook Floater
Alasmidonta varicosa
Brook Floater: https://www.marylandbiodiversity.org/species/281
Synonyms
Tags
G3 (Globally rare/local) Endangered (MD) S1 (Highly state rare)

Map Snapshot

35 Records

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Source: Wikipedia

Brook floater
Vulnerable
Vulnerable (NatureServe)[2]
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Unionida
Family: Unionidae
Genus: Alasmidonta
Species:
A. varicosa
Binomial name
Alasmidonta varicosa
(Lamarck, 1819)
Synonyms

Alismodonta varicosa (Lamarck, 1819)

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The brook floater[3] or swollen wedgemussel,[4] 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[5] although other research also suggests it rarely exceeds three inches (75 mm).[3]

Distribution

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This species is found in Canada (New Brunswick and Nova Scotia)[6] 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);[7] It was formerly found in Rhode Island and four watersheds in Massachusetts but are now extinct in Rhode Island and almost extinct in Massachusetts.[3] 1897 Research by Arnold Edward Ortmann showed it to be common in the Delaware and Susquehanna Rivers.[8]

Habitat and behavior

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This mussel lives in high relief streams, under boulders and in sand. Research has shown that it is highly sensitive to increased thermal temperature.[9] It associates with longnose and eastern blacknose dace, golden shiner, pumpkinseed, slimy sculpin and yellow perch.[10]

Survival threats and conservation

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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.[11] 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.[3] Trematoda rhopalocercous cercaria is a parasite of the brook floater.[12] Current research shows populations that were large and widespread have declined by 50% to 95% to almost extinct.[13]

While the IUCN lists it as Vulnerable, the states of New Jersey, Virginia, Massachusetts and New Hampshire[3] all list it as Endangered,[14] Threatened in Vermont, Maine and New York,[15] Rare/Endangered in Connecticut,[10] Extinct in Rhode Island and "Species of Special Concern" by the federal government.[16]

References

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  1. ^ Woolnough, D.; Bogan, A.E. (2017). "Alasmidonta varicosa". IUCN Red List of Threatened Species. 2017 e.T781A69490583. doi:10.2305/IUCN.UK.2017-3.RLTS.T781A69490583.en. Retrieved 17 November 2021.
  2. ^ NatureServe. "Alasmidonta varicos". NatureServe Explorer. Arlington, Virginia. Retrieved 24 December 2025.
  3. ^ a b c d e Nedeau, Ethan (1 November 2009) [Originally published as "Brook Floater Fact Sheet" in December 2007]. "Brook Floater" (PDF). mass.gov. Archived from the original (PDF) on 21 September 2017.
  4. ^ MassWildlife's Natural Heritage & Endangered Species Program (28 February 2020). "News Species Spotlight: Brook floater". Division of Fisheries and Wildlife. Commonwealth of Massachusetts. Retrieved 7 August 2023.
  5. ^ Janet L. Clayton, Craig W. Stihler and Jack L. Wallace (2001). "Status of and Potential Impacts to the Freshwater Bivalves (Unionidae) in Patterson Creek, West Virginia". Northeastern Naturalist. 8 (2): 179–188. doi:10.1656/1092-6194(2001)008[0179:SOAPIT]2.0.CO;2.
  6. ^ Caroline Caissie, Dominique Audet, Freshwater Mussel Inventory in the Shediac and Scoudouc Rivers Archived 2015-06-24 at the Wayback Machine, New Brunswick Wildlife Trust Fund, 2006, p. 12. Accessed August 21, 2014
  7. ^ "Brook floater (Alasmidonta varicosa)". ecos.fws.gov. Retrieved June 23, 2015.
  8. ^ Arnold Edward Ortmann (1897). Collected papers, Volume 1. self-published. Retrieved June 23, 2015.
  9. ^ "Thermal History Impacts Thermal Tolerance of Freshwater Mussels". co2science.org. Retrieved June 23, 2015.
  10. ^ a b Hammerson, Geoffrey A. (2004). Connecticut Wildlife: Biodiversity, Natural History, and Conservation. University Press of New England. p. 205. ISBN 978-1-58465-369-1. Retrieved June 23, 2015.
  11. ^ Strayer, David L.; Fetterman, Andrew R. (1999). "Changes in the Distribution of Freshwater Mussels (Unionidae) in the Upper Susquehanna River Basin, 1955–1965 to 1996–1997". The American Midland Naturalist. 142 (2): 328. doi:10.1674/0003-0031(1999)142[0328:CITDOF]2.0.CO;2.
  12. ^ Fischthal, Jacob H. (1954). "Cercaria tiogae Fischthal, 1953, a Rhopalocercous Form from the Clam, Alasmidonta varicosa (Lamarck)". Transactions of the American Microscopical Society. 73 (2): 210–215. doi:10.2307/3223759. JSTOR 3223759.
  13. ^ "The conservation status of the brook floater mussel, Alasmidonta varicosa, in the Northeastern United States: trends in distribution, occurrence, and condition of populations". rcngrants.org. Retrieved June 23, 2015.
  14. ^ Thomas F. Nalepa, Don W. Schloesser (2013). Quagga and Zebra Mussels: Biology, Impacts, and Control, Second Edition. CRC Press. p. 206. ISBN 978-1-4398-5437-2. Retrieved June 23, 2015.
  15. ^ McBroom, Matthew (2013). The Effects of Induced Hydraulic Fracturing on the Environment: Commercial Demands vs. Water, Wildlife, and Human Ecosystems. CRC Press. p. 285. ISBN 978-1-926895-83-3. Retrieved June 23, 2015.
  16. ^ Bruce E. Beans, Larry Niles (2003). Endangered and Threatened Wildlife of New Jersey. Rutgers University Press. p. 257. ISBN 978-0-8135-3209-7. Retrieved June 23, 2015.
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