Fusconaia cor





On June 14, 1976, the shiny pigtoe mussel was designated as endangered throughout its entire range in Alabama, Tennessee, and Virginia (USFWS 1976), except where listed as experimental populations (in the free‑flowing reach of the Tennessee River below the Wilson Dam, Colbert and Lauderdale Counties, AL) (USFWS 2001). A recovery plan addressing the shiny pigtoe was approved August 9, 1984 (USFWS 1984).



The shiny pigtoe is a medium-sized (reaching over 60 mm in length) freshwater mussel with a smooth and shiny yellowish-brown shell with prominent dark green to blackish rays (NatureServe 2003, INHS 1997). Like other freshwater mussels, the shiny pigtoe feeds by filtering food particles from the water column. The specific food habits of the species are unknown, but other juvenile and adult freshwater mussels have been documented to feed on detritus, diatoms, phytoplankton, and zooplankton (Churchill and Lewis 1924). The diet of shiny pigtoe glochidia, like other freshwater mussels, comprises water (until encysted on a fish host) and fish body fluids (once encysted).



The reproductive cycle of the shiny pigtoe is similar to that of other native freshwater mussels. Males release sperm into the water column; the sperm are then taken in by the females through their siphons during feeding and respiration. The females retain the fertilized eggs in their gills until the larvae (glochidia) fully develop. The mussel glochidia are released into the water, and within a few days they must attach to the appropriate species of fish, which they parasitize for a short time while they develop into juvenile mussels. The shiny pigtoe is likely a short term brooder with spawning occurring in May and release of glochidia in June or early July (ESIE 1996, USFWS 1984). Glochidia were found naturally encysted in the North Fork Holston River on the following species: the whitetail shiner (Notropis galacturus), common shiner (Notropis cornutus), warpaint shiner (Notropis coccogenis) and telescope shiner (Notropis telescopus) (Kitchel 1983). Laboratory infestation studies confirmed that the whitetail and common shiners are likely host species for the shiny pigtoe (USFWS 1984). The life span of shiny pigtoe mussels has been reported to exceed 25 years (Stansbery 1972).



This species was historically widespread Tennessee River and ten of its tributaries. It was last collected from Mussel Shoals, an 85 km reach of the Tennessee River in Alabama, prior to 1925 (Ortmann 1925) and is presumed to be extirpated from the shoal. It is currently known from five river systems including the Clinch River (from the Virginia-Tennessee border upstream to Nash Ford), Powell River (from the Virginia-Tennessee border upstream to Lee County, Tennessee), North Fork Holston River (Virginia), Elk River (Tennessee, though it has not been reported since 1980), and Paint Rock River (Alabama, where it is exceedingly rare) (USFWS 1984, NatureServe 2003). One fresh dead individual was found in the Paint Rock River in 1997 (Garner 1997).



The shiny pigtoe is a riffle species and prefers moderate to swiftly flowing streams and rivers with stable substrates (ESIE 1996, USFWS 1984). The species is not found in deep water or impounded areas (USFWS 1984). Substrate preferences include sand, gravel, and cobble (NatureServe 2003, ESIE 1996).



Many of the historic populations of the shiny pigtoe were apparently lost when the river sections they inhabited were impounded (ESIE 1996). Over 50 impoundments on the Tennessee and Cumberland Rivers have eliminated the majority of riverine habitat for the species in its historic range (ESIS 1996, USFWS 1984). The Powell River and upper tributaries of the Clinch River, in particular, are also subject to sediment and particulate matter loading from coal mining activities (Stansbery 1973). Water quality degradation has also been attributed to the decline of this species. In particular, the shiny pigtoe has been eliminated from the North Fork Holston River below the town of Saltville, VA as a result of releases of sodium chloride and mercury from a chemical plant (which is no longer operational). Contamination from this facility likely affected over 80 miles of riverine habitat downstream of the plant, and the shiny pigtoe is now only known to survive upstream of this facility. A population in the Holston River above the Cherokee Reservoir was adversely affected by wastewater discharges from industrial and municipal sources. In addition, two chemical spills in the Clinch River in 1967 and 1970 of fly ash slurry and sulfuric acid, respectively, severely reduced the distribution of the shiny pigtoe near Carbo, Virginia (ESIE 1996). In addition, Neves reports that between 1979 and 1986, 28 percent of the shiny pigtoe population at North Holston Ford, North Fork Holston River were eliminated by muskrat predation (Neves 1989). Other threats that are attributed to population declines are similar to those described in the general mussel description.



Current threats to freshwater mussels are well documented in the general mussel description.





Exposure Scenario Summary Table for the Shiny pigtoe




Life Stage


Habitat Type


Exposure Route




Significant Interspecies Relationships


shiny pigtoe






contact with water, diet


water (until encysted), fish body fluids (once encysted)


whitetail shiner

common shiner

warpaint shiner

telescope shiner


juvenile / adult


sediment dweller


contact & ingestion of water, diet, sediment


filter feeder (bacteria, algae, detritus, sediment)







Churchill, E.P., Jr., and S.I. Lewis. 1924. Food and feeding in freshwater mussels. Bull. U.S. Bur. Fish. 39: 439-471.


Endangered Species Information Exchange. 1996. Species Id ESIS404001. Virginia Tech Fish and Wildlife Information Exchange. Available (Accessed: December 8, 2003)


Garner, J.T. 1997. 1997 records of Alabama endangered species. In: Triannual Unionid Report No. 13. Available (Accessed: December 8, 2003).


Kitchel, H.E. 1983. The life history of Fusconaia edgariana (Mollusca: Bivalvia) from the North Fork Holston River, Smyth Co., Virginia. MS Thesis, VPI and SU, Blackburg, Virginia.


NatureServe. 2003. NatureServe Explorer: An online encyclopedia of life [web application]. Version 1.8. NatureServe, Arlington, Virginia. Available (Accessed: December 8, 2003 ).


Ortmann, A.E. 1925. The naiad fauna of the Tennessee River system below Walden Gorge. The American Midland Naturalist. 9(8): 321-372.


Stansbery, D.H. 1973. A preliminary report on the naiad fauna of the Clinch River in the southern Appalachian Mountains of Virginia and Tennessee (Mollusca: Bivalvia: Unionidae). Bull. Am. Malacol. Soc. 1972: 20-22.


U.S. Fish and Wildlife Service. 1976. Endangered Status for 159 Taxa of Animals. Federal Register 41: 24062-24067.


U.S. Fish and Wildlife Service. 1984. Recovery Plan for the Shiny Pigtoe Pearly Mussel, (Fusconaia edgariana). Region 4. Atlanta, GA. 67 pp.


U.S. Fish and Wildlife Service. 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, AL. Federal Register 66(115): 32250-32264.