James River Spinymussel
James River Spinymussel
Pleurobema collina
| Status | Endangered |
| Listed | July 22, 1988 |
| Family | Unionidae (Freshwater Mussel) |
| Description | Medium-sized, reddish brown shell with dark brown to blackish margins. |
| Habitat | Slow-flowing stretches of head-water streams. |
| Food | Filter-feeder. |
| Reproduction | Female stores sperm in gills; glochidia are released into the stream after hatching. |
| Threats | Habitat modification; competition with the Asiatic clam. |
| Range | Virginia, West Virginia |
Description
Also known as the Virginia spinymussel or James spinymussel, Pleurobema collina, the James River spinymussel is described as having an intermediate shell size (2-3.5 in; 5-9 cm) and spine length. Shells of juvenile mussels usually bear one to three short but prominent spines on each valve. Adult shells are reddish brown with dark brown to blackish margins, and typically lack spines. The foot and mantle of the adult are vivid orange; the mantle is darkened in a narrow band around the edges of the branchial and anal openings. Scientists have variously classified this species as Fusconaia collina, Elliptio collina, and Cantheria collina.
Only two other freshwater spinymussels are known—Elliptio spinosa from the Altamaha River in Georgia, and the Tar River spinymussel (Elliptio steinstansana ) from the Tar River in North Carolina. The Tar River spinymussel was listed as Endangered in 1985.
Behavior
Spawning occurs in May, and the period of gravity in females is late May through early August. Densities of glochidia peak in late June to mid-July as stream discharge drops to summer levels and water temperature reaches 75°F (24°C.). The host fish species required for glochidial development include bluehead chub, rosyside dace, satinfin shiner, rosefin shiner, central stoneroller, blacknose dace, and mountain redbelly dace.
For more on the reproduction and diet of freshwater mussels, see the Upland Combshell (Epioblasma metastriata ) entry.
Habitat
The James River spinymussel requires freshwater streams with high water quality and a fairly high mineral content. It has been collected from sand and gravel substrates, generally in slow-moving water.
Distribution
The James River spinymussel was first discovered in the Calfpasture River (Rockbridge County), Virginia, in 1836. It was once widely distributed in the James River drainage, which includes the Rivanna River, Mill Creek, the Calfpasture River, Johns Creek, and numerous headwater creeks. The range of this species has been reduced to less than 10% of its historic size.
Currently, the James River spinymussel survives in a few headwater streams of the James River— Craig, Catawba, and Johns Creeks (Craig and Botetourt Counties, Virginia), and Potts Creek (Monroe County, West Virginia).
Threats
Habitat modification has been a major factor in the decline of this spinymussel. The few drainages still supporting the species are threatened by harmful agricultural runoff of silt, fertilizers, and herbicides. It is hoped that federal control over issuance of permits for mineral exploration, timber sales, recreational development, stream channelization, and bridge construction and maintenance can be used to prevent further disturbance of the watershed.
The Asiatic clam (Corbicula fluminea ) has invaded many formerly inhabited streams. This clam establishes very dense populations which filter most of the phytoplankton from the water—in essence, starving the spiny and other native mussels.
Muskrats apparently prey on this mussel. A sample of shells collected in muskrat middens revealed that the mussels consumed by the muskrats ranged in age from three to 19 years, averaging about eight years. It is thought that the natural annual mortality rate is about 10% of the population.
Conservation and Recovery
Survival of the James River spinymussel will probably require a program to control Asiatic clam populations. However, as water quality improves in the James River, it is feasible that remnant populations could expand and recolonize some historical habitat.
Contact
U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Drive
Hadley, Massachusetts 01035
http://northeast.fws.gov/
References
Burch, J. B. 1975. Freshwater Unionacean Clams of North America. Malacological Publications, Hamburg, Michigan.
Diaz, R. J. 1974. "Asiatic Clam Corbicula manilensis in the Tidal James River, Virginia." Chesapeake Science 15(2):118-120.
U.S. Fish and Wildlife Service. 1988. "Determination of Endangered Status for the James River Spinymussel." Federal Register 53 (141): 27689-27693.
Zeto, M. A., and J. E. Schmidt. 1984. "Freshwater Mussels of Monroe County, West Virginia." Nautilus 96(4):147-151.