Roadless Areas
Home/Species/ Oyster Mussel

Epioblasma capsaeformis

(I. Lea, 1834)

Oyster Mussel

G1Critically Imperiled Found in 1 roadless area NatureServe Explorer →
G1Critically ImperiledGlobal Rank
EndangeredIUCN
Very highThreat Impact
Oyster mussel (Epioblasma capsaeformis). Photo by U.S. Fish & Wildlife Service, Public Domain (U.S. Government Work), via ECOS.
U.S. Fish & Wildlife Service, https://www.usa.gov/government-works
Identity
Unique IDELEMENT_GLOBAL.2.118984
Element CodeIMBIV16040
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryInvertebrate Animal
IUCNEndangered
Endemicendemic to a single nation
KingdomAnimalia
PhylumMollusca
ClassBivalvia
OrderUnionoida
FamilyUnionidae
GenusEpioblasma
Synonyms
Dysnomia capsaeformis(I. Lea, 1834)Plagiola capsaeformis(I. Lea, 1834)
Concept Reference
Turgeon, D. D., J. F. Quinn, Jr., A. E. Bogan, E. V. Coan, F. G. Hochberg, W. G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland. 526 pp.
Taxonomic Comments
There is a problem related to misidentification and priority concerning Epioblasma and Plagiola. Epioblasma is used in anticipation of a decision in its favor by the ICZN. It has been suggested that this species may be a senior synonym of Epioblasma florentina walkeri (see Buhay et al., 2002), but molecular, morphological, and life history data from Jones (2004) and Jones et al. (2006) suggest they are distinct. Based on molecular, morphological, and life history data, the population from the Duck River, Tennessee, is tentatively proposed as a separate species from Epioblasma capsaeformis populations in the Clinch River because of distinctiveness of molecular genetic markers, differences in mantle pad coloration and texture, greater height of marsupial expansion of the female shell, smaller glochidial size, differing host fish specificity, and behavioral differences in movement of micro-lures (Jones, 2004; Jones et al., 2006).
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2023-12-05
Change Date2003-10-28
Edition Date2023-12-05
Edition AuthorsCordeiro, J. (2011); rev. T. Cornelisse (2023)
Threat ImpactVery high
Range Extent5000-200,000 square km (about 2000-80,000 square miles)
Number of Occurrences1 - 20
Rank Reasons
This species has a moderate range but due to long and short-term population declines and many ongoing threats, it has few viable occurrences.
Range Extent Comments
This species occurs in the Clinch and Nolichucky Rivers, with remnant or reestablished populations in the Cumberland River and upper Tennessee River systems, in Tennessee, Kentucky, and Virginia, USA (USFWS 2019).
Occurrences Comments
This species is known from two stream reaches in 5-6 populations, including those from reintroduction efforts (USFWS 2019).
Threat Impact Comments
This species is threatened by oil and gas exploration, coal mining, and the heavy metal and chemical pollutants that result from those activities, agriculture and urbanization, as well as sedimentation and pollutants due to runoff from development and agriculture, dams or other barriers that alter its habitat, host fish distribution, and prevent habitat connectivity and recolonization, and drought conditions that reduce habitat, elevate water temperature, and reduce dilution of pollutants and sediment runoff (USFWS 2004; 2019).
Ecology & Habitat

Description

Shell medium-sized, elliptical (male) to irregularly obovate (female), slightly inflated, subsolid to quite thin posteriorly (female); anterior regularly rounded; ventral margin slightly curved (male) to almost straight (female); posterior margin obliquely sloped from an obtusely angular posterio-dorsal junction to a blunt or biangulate point at the posterio-ventral junction; posterio-ventral are of female broadly expanded to accomodate the branchial marsupia, slightly inflated, demarcated by sulci, margin may be dentate, expansion may appear bilobed in old individuals; dorsal margin rather straight; beaks broad, elevated above hinge line, sculpted by feeble undulations; posterior ridge angular and more-or-less double (male) to slight or imperceptible (female), a slight sulcus occurs anteriorly in male; periostracum dull to subshiny, yellowish to green with numerous dark green rays across surface, marsupial expansion usually dark green to blackish. Pseudocardinals rather heavy, triangular, double in left valve, single in right; interdentum slight, rather short; lateral teeth slightly curved, rather short, double in left, single in right; beak cavity shallow; anterior muscle scars well-impressed, posterior muscle scars shallow; pallial line impressed anteriorly; nacre whitish to bluish-white.

Diagnostic Characteristics

The pronounced development of the posterio-ventral region in females distinguishes EPIOBLASMA from similarly shaped species. Epioblasma capsaeformis is recognizable by the typically dark coloration and fragility of the marsupial expansion and the lack of development of the posterior ridge (e.g., not angular, no knobs). Males in comparison to similar Epioblasma tend to be more elliptical, have a moderately developed posterior ridge and accompanying sulcus, and have a regularly curved ventral margin. The ventral margin in species such as Epioblasma florentina (Lea 1857) and Epioblasma turqidula (Lea 1858) often exhibit an emargination of the ventrum just anterior to the terminus of the posterior ridge. Yellowish specimens of E. capsaeformis have been mistaken for Epioblasma walkeri (Wilson and Clark 1914) (including records in Johnson [1978: as E. florentina]). Males of E. walkeri tend to be broader and have a rounded posterior ridge; females lack the distinctive darkening of the marsupial expansion.

Habitat

This species is found in small to medium-sized rivers, and occasionally in large rivers, in areas with coarse sand to boulder substrates and moderate to swift currents (USFWS 2003, 2004).

Reproduction

This species appears to be a long-term brooder as glochidia have been found in the marsupia during winter months (Gordon and Layzer 1989).
Other Nations (1)
United StatesN1
ProvinceRankNative
VirginiaS1Yes
TennesseeS1Yes
AlabamaSXYes
KentuckyS1Yes
GeorgiaSXYes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
2 - Agriculture & aquacultureRestricted (11-30%)Serious - moderateHigh (continuing)
2.3 - Livestock farming & ranchingRestricted (11-30%)Serious - moderateHigh (continuing)
2.3.4 - Scale unknown/unrecordedRestricted (11-30%)Serious - moderateHigh (continuing)
7 - Natural system modificationsLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
7.2 - Dams & water management/useLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
9 - PollutionPervasive - largeExtreme - seriousHigh (continuing)
9.1 - Domestic & urban waste waterLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
9.1.2 - Run-offLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
9.2 - Industrial & military effluentsLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
9.3 - Agricultural & forestry effluentsRestricted (11-30%)Serious or 31-70% pop. declineHigh (continuing)
11 - Climate change & severe weatherRestricted (11-30%)Serious - moderateHigh (continuing)
11.2 - DroughtsRestricted (11-30%)Serious - moderateHigh (continuing)

—

Roadless Areas (1)
Idaho (1)
AreaForestAcres
Bear CreekCaribou-Targhee National Forest118,582
References (58)
  1. Ahlstedt, S.A. and J.M. Tuberville. 1997. Quantitative reassessment of the freshwater mussel fauna in the Clinch and Powell rivers, Tennessee and Virginia. Pages 72-97 in K.S. Cummings, A.C. Buchanan, C.A. Mayer, and T.J. Naimo, eds. Conservation and management of freshwater mussels II: initiatives for the future. Proceedings of a UMRCC symposium, 16-18 October 1995, St. Louis, Missouri. Upper Mississippi River Conservation Committee, Rock Island, Illinois.
  2. Anthony, J.L. and J.A. Downing. 2001. Exploitation trajectory of a declining fauna: a century of freshwater mussel fisheries in North America. Canadian Journal of Fisheries and Aquatic Sciences, 58: 2071-2090.
  3. Baker, F.C. 1928b. The freshwater Mollusca of Wisconsin: Part II. Pelecypoda. Bulletin of the Wisconsin Geological and Natural History Survey, University of Wisconsin, 70(2): 1-495.
  4. Barr, W.C., S.A. Ahlstedt, G.D. Hickman, and D.M. Hill. 1993-1994. Cumberlandian mollusk conservation program. Activity 8: Analysis of macrofauna factors. Walkerana 7(17/18):159-224.
  5. Biological Resources Division, USGS. 1997. Database of museum records of aquatic species. Compiled by J. Williams (USGS-BRD, Gainesville, FL).
  6. Bogan, A.E. 2002. Workbook and key to the freshwater bivalves of North Carolina. North Carolina Museum of Natural Sciences: Raleigh, North Carolina. 101 pp.
  7. Bogan, Art (Curator of Aquatic Invertebrates, North Carolina State Museum of Natural Sciences). 1997. Review and annotation of mussel watershed distribution maps for TN. Review requested by Ruth Mathews, TNC. September 1997.
  8. Buhay, J.E., J.M. Serb, C. R. Dean, Q. Parham, and C. Lydeard. 2002. Conservation genetics of two endangered unionid bivalve species, <i>Epioblasma florentina walkeri</i> and <i>E. capsaeformis</i> (Unionidae: Lampsilini). Journal of Molluscan Studies, 68: 385-391.
  9. Cicerello, Ronald R. (Kentucky State Nature Preserves). 1997b. Review and annotation of mussel watershed distribution maps. Review requested by Ruth Mathews, TNC. September 1997.
  10. Dennis, S.D. 1987. An unexpected decline in populations of the freshwater mussel, <i>Dysnomia </i>(= <i>Epioblasma</i>) <i>capsaeformis</i>, in the Clinch river of Virginia and Tennessee. Virginia Journal of Science, 38(4): 281-288.
  11. Dennis, S.D. 1989. Status of the freshwater mussel fauna, Pendleton Island Mussel Preserve, Clinch River, Virginia. Sterkiana, 72: 19-27.
  12. Fraley, S.J. and S.A. Ahlstedt. 1999. The recent decline of the native mussels of Copper Creek, Scott County, Virginia. [abstract]. Page 26 in Program Guide and Abstracts. The First Symposium of the Freshwater Mollusk Conservation Society, Chattanooga, Tennessee, March 17-19, 1999.
  13. Freshwater Mollusk Conservation Society (FMCS). 2023. The 2023 checklist of freshwater bivalves (Mollusca: Bivalvia: Unionida) of the United States and Canada. Considered and approved by the Bivalve Names Subcommittee October 2023. Online: https://molluskconservation.org/MServices_Names-Bivalves.html
  14. Gordon, M.E. and J.B. Layzer. 1989. Mussels (Bivalvia: Unionoidea) of the Cumberland River review of life histories and ecological relationships. U.S. Fish and Wildlife Service Biological Report, 89(15): 1-99.
  15. Graf, D.L. and K.S. Cummings. 2021. A 'big data' approach to global freshwater mussel diversity (Bivalvia: Unionoida), with an updated checklist of genera and species. Journal of Molluscan Studies 87(1):1-36.
  16. Hanlon, S.D., M.A. Petty, and R.J. Neves. 2009. Status of native freshwater mussels in Copper Creek, Virginia. Southeastern Naturalist 8(1):1-18.
  17. Hill, D.M. 1986. Cumberlandian mollusk conservation program, activity 3: identification of fish hosts. Office of Natural Resources and Economic Development, Tennessee Valley Authority, Knoxville, Tennessee. 55 pp.
  18. Howard, A. D. 1915. Some exceptional cases of breeding among the Unionidae. The Nautilus 29:4-11.
  19. Isom, B. G. and P. Yokley, Jr. 1973. The mussels of the Flint and Paint Rock River Systems of the southwest slope of the Cumberland Plateau in North Alabama-1965 and 1967. The American Midland Naturalist 89(2):442-446.
  20. Isom, B.G., P. Yokley, Jr., and C.H. Gooch. 1973. Mussels of Elk River Basin in Alabama and Tennessee- 1965-1967. American Midland Naturalist 89(2):437-442.
  21. James, M.R. 1987. Ecology of the freshwater mussel <i>Hyridella menziesi</i> in a small oliogotrophic lake. Archives of Hydrobiology 108:337-348.
  22. Jenkinson, J.J. 1988. Resurvey of freshwater mussel stocks in Duck River, TN. Report to the Tennessee Valley Authority, Knoxville, Tennessee. 20 pp.
  23. Jenkinson, J.J. and S.A. Ahlsedt. 1988a. Quantitative reassessment of the freshwater mussel fauna in the Clinch River, Tennessee and Virginia. Tennessee Valley Authority, Knoxville, Tennessee. 28 pp.
  24. Jenkinson, J.J. and S.A. Ahlstedt. 1988b. Quantitative reassessment of the freshwater mussel fauna in the Powell River, TN and VA. Tennessee Valley Authority, Knoxville, Tennessee. 28 pp.
  25. Jones, J.W. 2004. A holistic approach to taxonomic evaluation of two closely related endangered freshwater mussel species, the oyster mussel (<i>Epioblasma capsaeformis</i>) and tan riffleshell (<i>Epioblasma florentina walkeri</i>) (Bivalvia: Unionidae). MS Thesis, Virginia Polytechnic Institute and State University, Blacksburg, Virginia. 178 pp.
  26. Jones, J.W., M. Cuvier, V. David, J. Struthers, N.A. Johnson, R.J. Neves, S.J. O'Brien, and E.M. Hallerman. 2004. Development and characterization of microsatellite loci in the endangered oyster mussel <i>Epioblasma capsaeformis</i> (Bivalvia: Unionidae). Molecular Ecology Notes, 4: 649-652.
  27. Jones, J.W., R.J. Neves, M.A. Patterson, C.R. Good, and A. DiVittorio. 2001. A status survey of freshwater mussel populations in the upper Clinch River, Tazewell County, Virginia. Banisteria 17: 20-30.
  28. Jones, J.W., R.J. Neves, S.A. Ahlstedt, and E.M. Hallerman. 2006. A holistic approach to taxonomic evaluation of two closely related endangered freshwater mussel species, the oyster mussel <i>Epioblasma capsaeformis </i>and tan riffleshell <i>Epioblasma florentina walkeri </i>(Bivalvia: Unionidae). Journal of Molluscan Studies, 72: 267-283.
  29. Lefevre, G. and W. T. Curtis. 1912. Studies on the reproduction and artificial propagation of fresh-water mussels. Bulletin of the Bureau of Fisheries 30:102-201.
  30. Lopez, G.R. and I.J. Holopainen. 1987. Interstitial suspension-feeding by <i>Pisidium </i>spp. (Pisidiiae: Bivalvia): a new guild in lentic benthos? American Malacological Bulletin, 5: 21-29.
  31. Major, Smoot (Tennessee Division of Natural Heritage). 1997. Review and annotation of fish and mussel watershed distribution maps. Review requested by Ruth Mathews, TNC on 19 August 1997.
  32. Mirarchi, R.E., et al. 2004a. Alabama Wildlife. Volume One: A Checklist of Vertebrates and Selected Invertebrates: Aquatic Mollusks, Fishes, Amphibians, Reptiles, Birds, and Mammals. University of Alabama Press: Tuscaloosa, Alabama. 209 pp.
  33. Mirarchi, R.E., J.T. Garner, M.F. Mettee, and P.E. O'Neil. 2004b. Alabama wildlife. Volume 2. Imperiled aquatic mollusks and fishes. University of Alabama Press, Tuscaloosa, Alabama. xii + 255 pp.
  34. MolluscaBase eds. 2024. MolluscaBase. Accessed at https://www.molluscabase.org
  35. Moyle, P., and J. Bacon. 1969. Distribution and abundance of molluscs in a fresh water environment. Journal of the Minnesota Academy of Science 35(2/3):82-85.
  36. Ortmann, A.E. 1914. Studies in naiades (in partim). The Nautilus 28: 20-22, 28-34, 41-47, 65-69
  37. Ortmann, A.E. 1924. The naiad fauna of Duck River in Tennessee. The American Midland Naturalist, 9: 18-62.
  38. Parmalee, P.W. and A.E. Bogan. 1998. The Freshwater Mussels of Tennessee. University of Tennessee Press: Knoxville, Tennessee. 328 pp.
  39. Strayer, D. 1983. The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A. Freshwater Biology 13:253-264.
  40. Strayer, D. L. 1999. Use of flow refuges by unionid mussels in rivers. Journal of the North American Benthological Society 18(4):468-476.
  41. Strayer, D. L., and J. Ralley. 1993. Microhabitat use by an assemblage of stream-dwelling unionaceans (Bivalvia) including two rare species of <i>Alasmidonta</i>. Journal of the North American Benthological Society 12(3):247-258.
  42. Turgeon, D. D., J. F. Quinn, Jr., A. E. Bogan, E. V. Coan, F. G. Hochberg, W. G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. 2nd Edition. American Fisheries Society Special Publication 26, Bethesda, Maryland. 526 pp.
  43. U.S. Fish and Wildlife Service (USFWS). 1997. Determination of Endangered Status for the Cumberland Elktoe, Oyster Mussel, Cumberlandian Combshell, Purple Bean, and Rough Rabbitsfoot. Final rule. Federal Register, 62(7): 1647-1658.
  44. U.S. Fish and Wildlife Service (USFWS). 1998. Cumberland elktoe (<i>Alasmidontaq atropurpurea</i>), oyster mussel (<i>Epioblasma capsaeformis</i>), Cumberlandian combshell (<i>Epioblasma brevidens</i>), purple bean (<i>Villosa perpurpurea</i>), and rough rabbitsfoot (<i>Quadrula cylindrica strigillata</i>): Technical Draft Recovery Plan. U.S. Fish and Wildlife Service: Asheville, North Carolina. 119 pp.
  45. U.S. Fish and Wildlife Service (USFWS). 2001. Endangered and Threatened Wildlife and Plants; establishment of nonessential experimental population status for 16 freshwater mussels and 1 freshwater snail (Anthony's Riversnail) in the free-flowing reach of the Tennessee River below the Wilson Dam, Colbert and Lauderdale Counties, Alabama. Federal Register, 66(115): 32250-32264.
  46. U.S. Fish and Wildlife Service (USFWS). 2003. Endangered and Threatened Widlife and plants; proposed designation of critical habitat for five threatened mussels in the Tennessee and Cumberland River basins; proposed rule. Federal Register, 68(106): 33234-33282
  47. U.S. Fish and Wildlife Service (USFWS). 2004a. Recovery plan for Cumberland elktoe, oyster mussel, Cumberlandian combshell, purple bean, and rough rabbitsfoot. U.S. Fish and Wildlife Service, Atlanta, Georgia. 168 pp.
  48. U.S. Fish and Wildlife Service (USFWS). 2004b. Endangered and Threatened wildlife and plants; designation of critical habitat for five endangered mussels in the Tennessee and Cumberland River basins; final rule. Federal Register 69(168): 53135-53180.
  49. U.S. Fish and Wildlife Service (USFWS). 2006. Endangered and threatened wildlife and plants; establishment of nonessential experimental population status for 15 freshwater mussels, 1 freshwater snail, and 5 fishes in the lower French Broad River and in the lower Holston River, Tennessee; Proposed Rule. Federal Register, 71(113): 34195-34230.
  50. U.S. Fish and Wildlife Service (USFWS). 2019. Oyster Mussel <i>Epioblasma capsaeformis</i>, five year review: summary and evaluation. U.S. Fish and Wildlife Service Southeast Region Tennessee Ecological Services Field Office Cookeville, Tennessee. 28 pp.
  51. U.S. Fish and Wildlife Service (USFWS). 2023. Initiation of 5-Year Status Reviews for 67 Southeastern Species. Notice of initiation of reviews; <br/>request for information. Federal Register 88(91): 30324-30328.
  52. Van der Schalie, H. 1938. The naiad fauna of the Huron River in southeastern Michigan. Miscellaneous Publication of the Museum of Zoology, University of Michigan 40:7-78.
  53. Watters, G. T. 1992. Unionids, fishes, and the species-area curve. Journal of Biogeography 19:481-490.
  54. Wells, S.M., R.M. Pyle, and N.M. Collins. 1983. The IUCN Invertebrate Red Data Book. IUCN, Gland, Switzerland. 632 pp.
  55. Williams, J.D., A.E. Bogan, and J.T. Garner. 2008. Freshwater Mussels of Alabama & the Mobile Basin in Georgia, Mississippi & Tennessee. University of Alabama Press: Tuscaloosa, Alabama. 908 pp.
  56. Williams, J. D., A. E. Bogan, R. S. Butler, K. S. Cummings, J. T. Garner, J. L. Harris, N. A. Johnson, and G. T. Watters. 2017. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20:33-58.
  57. Williams, J. D., M. L. Warren, Jr., K. S. Cummings, J. L. Harris, and R. J. Neves. 1993. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9):6-22.
  58. Yeager, B.L. and C.F. Saylor. 1995. Fish hosts for four species of freshwater mussels (Pelecypoda: Unionidae) in the Upper Tennessee River drainage. American Midland Naturalist, 133(1): 1-6.