North Carolina Freshwater Mussels

North Carolina is home to more than 60 species of freshwater mussels. Unfortunately, 50% of these species are designated Endangered, Threatened, or Special Concern within the state. The Nongame and Endangered Wildlife Program strives to prevent species from becoming endangered through maintaining viable, self-sustaining populations of native wildlife, with an emphasis on species in decline. Public education is a major component of this effort. The following pages provide detailed information about North Carolina's freshwater mussel species. The following are definitions for each status:

  • "Endangered" status includes any native species whose continued existence as a viable component of the state's fauna is determined to be in jeopardy and/or is designated "Endangered" by the United States Fish and Wildlife Service under the Endangered Species Act.
  • A status of "Threatened" includes any native species likely to become endangered within the foreseeable future throughout all or a significant portion of its range within the state and/or is designated "Threatened" by the United States Fish and Wildlife Service under the Endangered Species Act.
  • The "Special Concern" designation applies to any species that is determined to require monitoring.
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Species Information and Status Species Information and Status
Species Identification Key Species Identification Key
Life History of Freshwater Mussels Life History of Freshwater Mussels
Shell Anatomy Shell Anatomy
Glossary Glossary
References References

 

 

 

 

 

 


Life History of Freshwater Mussels

During the spawning season, mature males release prodigious quantities of sperm into the water. For fertilization to occur, these sperm must pass into the incurrent apertures of sexually mature females of the same species. The sperm travel through the aperture into the suprabranchial chamber where the eggs are held. The fertilized eggs are then transferred into the gill chambers. The gill chambers form a modified brood pouch called the marsupium. While in the marsupium, the fertilized eggs metamorphose from an embryo into the larval form known as the glochidium. Glochidia may be released after a few weeks, or mature glochidia may be held in the brood chamber for months, depending upon the species.

The glochidia of most freshwater mussels are obligate parasites of fish. Once the glochidia have matured within the gills of the female mussel, they must attach to the gills or fins of a suitable fish species to go through yet another metamorphosis into free-living mussels. Fish may become infested with glochidia in several ways. The glochidia of some mussel species are lightweight and float in the water column after they are released. These are "eaten" by fish but instead of passing into the fishs digestive tract, the glochidia attach to its gills. Other glochidia are heavy, and once they are released, they sink to the bottom of the stream. These glochidia are more likely to attach to the fins of fish as they swim over them.

Females of several mussel species use mimicry to lure fish hosts to themselves before they release their glochidia. The mantle tissue of these species are modified in such a way that they look like prey fish or insects to the fish host. When the female waves these tissues, the fish host may attack the "minnow" and instead of a meal receives a mouthful of glochidia. The glochidia then attach to the gills of the fish. Other mussel species use a kind of fishing lure instead of their own tissues. These mussels produce a gelatinous matrix around the mature glochidia before they are released. This matrix and the glochidia together are called a conglutinate. Some mussel species completely release the conglutinate, and it drifts into the water column or onto the substrate, looking much like a worm or insect, where it is "eaten" by the fish host. Other mussel species release the conglutinate, but it remains tethered to the female mussel by a "fishing line" of the matrix material. The conglutinate waves about in the water column and is "eaten" by the fish host.

Once the glochidia have successfully attached to the fish host, they remain attached for a period of time that varies by species. While attached, the glochidia metamorphose into juvenile mussels, developing a true heart, liver, digestive tract, and muscular foot. When the metamorphosis is complete, the juvenile mussels excyst from the fish host and begin an independent life. 

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Shell Anatomy

 

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References

Adams, W.F. 1990. Recent changes in the freshwater molluscan fauna of the Greenfield Lake basin, North Carolina. Brimleyana 16.

Ahlstedt, S.A. 1984. Twentieth century changes in the freshwater mussel fauna of the Clinch River (Tennessee and Virginia). Master of Science in Wildlife and Fisheries Thesis. The University of Tennessee, Knoxville.

Alderman, J.M. 1988. Tar River spinymussel annual performance report. In: Annual performance report for the North Carolina Wildlife Resources Commission - Wildlife Management, October 1987-June 1988. 41: 192-218.

Baker, F.C. 1928. The freshwater Mollusca of Wisconsin. Part II. Pelecypoda. Bulletin of the Wisconsin Geologic and Natural History Survey No.70. 495 pp.

Barfield, M.L. and G.T. Watters. 1998. Non-parasitic life cycle in the green floater, Lasmigona subviridis (Conrad 1835). Triannual Unionid Report No. 16, November.

Biggins, R.G. 1990. A report on the conservation status of North Carolina's freshwater and terrestrial molluscan fauna, Tennessee heelsplitter. Pages 45-46.

Britton, J.C. and S.L.H. Fuller. 1979. The freshwater biovalve Mollusca (Unionidae, Sphaeriidae, Corbiculidae) of the Savannah River Plant, South Carolina. The Savannah River Ecology Laboratory.

Burch, J.B. 1975. Freshwater Unionacean clams (Mollusca:Pelecypoda) of North America. Rev. ed., Malacological Pubs., Hamburg, MI, 204 pp + i-xvii.

Clarke, A.H. 1981. The freshwater molluscs of Canada. National Museum of Natural Sciences/National Museums of Canada. 446 pp.

Clarke, A.H. 1981. The tribe Alasmidontini (Unionidae: Anondontinae), Part I: Pegias, Alasmidonta, and Arcidens. Smithsonian Contributions to Zoology No. 326. 101 pp.

Conrad, T.A. 1836 - 40. Monography of the family Unionidae, or naiades of Lamarch, (Fresh water bivalve shells) of North America.   Philadelphia, Penn., pp. i-v, 1-118.  Published in 13 parts.

Cummings, K.S. and C.A. Mayer. 1992. Field guide to the freshwater mussels of the Midwest. Illinois Natural History Survey Manual 5. 194 pp.

Fridell, J.A. 1992. Revised Tar spinymussel recovery plan (Elliptio (Canthyria) steinstansana Johnson and Clarke. U.S. Fish and Wildlife Service. Atlanta, GA. 34 pp.

Ellis, M.M. and M. Keim. 1918. Notes on the glochidia of Strophitus edentulus pavonius (Lea) from Colorado. Nautilus 32: 17-18.

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). 99 pp.

Hove, M.C. 1990. Distribution and life history of the endangered James spinymussel, Pleurobema collina (Bivalvia: Unionidae). M.S. Thesis, Virginia Polytechnic Institute and State University, Blacksburg, Virginia. 113 pp.

Howells, R.G., R.W. Neck, and H.D. Murray. 1996. Freshwater mussels of Texas. Texas Parks and Wildlife Department. 218 pp + i-iv.

Johnson, R.I. 1946. Anondonta implicata Say. Occasional Papers on Molluscs, Museum of Comparative Zoology 1: 109-116.

Johnson, R.I. 1947. Lampsilis cariosa Say and Lampsilis ochracea Say. Occ. Pap.Moll., Mus. Comp. Zool. 1:145-156.

Johnson, R. I. 1970. The systematics and zoogeography of the Unionidae (Mollusca: Bivalvia) of the southern Atlantic Slope region. Bulletin of the Museum of Comparative Zoology 140(6): 263-449.

Johnson, R.I. and A.H. Clarke. 1983. A new spiny mussel, Elliptio (Canthyria) steinstansana (Bivalvia: Unionidae), from the Tar River, North Carolina. Occas. Pap. Mollusks. 4(61):289-298

Knutson, K.L., and V.L. Naef. 1997. Management Recommendations for Washington's Priority Habitats: Riparian. Washington Department Fish and Wildlife, Olympia.

Lellis, W.A. and T.M. King. 1998. Release of metamorphosed juveniles by the green floater, Lasmigona subviridis. Triannual Unionid Report No. 16, November.

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Ortmann, A.E. 1911. A monograph of the naiades of Pennsylvania, Parts 1 and 2. Mem. Carnegie. Mus. 4: 279-347. Shelley, R. M. 1983. Occurrence of the unionid, Anodonta implicata Say, in North Carolina. Nautilus 97:145-147.

Ortmann, A.E. 1914. Studies in najades (Part 3). Nautilus 30(5):50-53.

Ortmann, A. E. 1919. A monograph of the naiades of Pennsylvania, part 3. Systematic account of the genera and species. Mem. Carnegie Mus. 8(1): 1-389, plates 1-21.

Ortmann, A. W. 1921. The anatomy of certain mussels from the Upper Tennessee. The Nautilus 34(3):81-91.

Parmalee P.W. and A. E. Bogan. 1998. The Freshwater Mussels of Tennessee. The University of Tennessee Press, Knoxville. 328 pp.

Porter, H. J. and K.J. Horn. 1983. Habitat distribution of sympatric populations of selected lampsiline species (Bivalvia: Unionoida) in the Waccamaw Drainage of eastern North and South Carolina. American Malacological Bulletin 1:61-66.

Porter, H.J. 1985. Molluscan census and ecological interrelationships. Rare and endangered fauna of Lake Waccamaw, North Carolina watershed system. North Carolina endangered species restoration final report - period: 1978-81. North Carolina Wildlife Resources Commission, University of North Carolina Institute of Marine Sciences, Morehead City, NC. Vol 1-2.

Porter, H.J. 1990. A report on the conservation status of North Carolina's freshwater and terrestrial molluscan fauna, Waccamaw spike. Pages 73-80.

Shultz, C. and K. Marbain. 1998. A list of host species for rare freshwater mussels in Virginia. Triannual Unionid Report Report No. 15 July.

Starnes, L.B. and A.E. Bogan. 1988. The mussels (Mollusca: Bivalvia: Unionidae) of Tennessee. American Malacologial Bulletin 6(1): 19-37.

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Tankersley, R.A. 1988. Microscopic examination of the glochidia and sybiotic mites of the freshwater mussels of the Tar River, N.C. Report to the North Carolina Wildlife Resources Commission.

van der Schalie, H. 1970. Hermaphoditism among North American freshwater mussels. Malacologia 10: 93-112.

Vidrine, M.F. 1980. Systematic and coevolution of unionicolid watermites and their unionid hosts in the eastern United States. Ph.D. dissertation, University of Southeastern Louisiana, Lafayette. 661 pp. +

Walter, W. M. 1954. Mollusks of the Upper Neuse River, North Carolina. PhD dissertation, Duke University.

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Watters, G.T. 1994. An annotated bibliography of the reproduction and propagation of the Unionoidea (Primarily of North America). Ohio Biological Survey Miscellaneous Contributions No.1. 158 pp.

Watters, G. T., and S. H. O'Dee. 1997. Identification of potential host: Elliptio fisheriana (Lea 1838), Fusconaia masoni (Conrad 1834), Fusconaia flava (Rafinesque 1820), and Pleurobema clava (Lamark 1819). Triannual Unionid Report No.13.

Zale, A.V. and R.J. Neves. 1981. Identification of a host fish for Alasmidonta minor (Mollusca: Unionidae). American Midland Naturalist 107:386-388.

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