Dromedary Pearlymussel

Dromus dromas

Description

The dromedary pearlymussel, Dromus dromas, is a medium-sized species, round to triangular or elliptical in outline. Valves are generally solid and inflated. The outer surface of the shell has a hump with a curved row of smaller knobs near the middle of the shell. The outer covering is yellow-green with broken green rays covering the shell. The inner shell color is generally white or pinkish in the big river mussels (D. dromas ), while the inner shell of the headwaters mussels (D. d. caperatus ) is whitish pink, salmon, or reddish. D. dromas was first described from the Harpeth and Cumberland Rivers in Tennessee. D. d. caperatus was first described from the Clinch River in Virginia and Tennessee.

Behavior

See the Upland Combshell (Epioblasma metastriata ) entry.

Habitat

These mussels bury themselves in the substrate in shallow riffle and shoal areas, in relatively firm rubble, gravel, and sand swept free of silt by clean fast-flowing water.

Distribution

Cumberlandian mussels are endemic to the southern Appalachian Mountains and the Cumberland Plateau region. The dromedary pearly mussel was once widely distributed in the upper Tennessee and Cumberland river basins, from the headwaters of the Tennessee River as far south as Muscle Shoals, Alabama. It was also reported from the Caney Fork of the Cumberland River system, where it may have been more abundant than in the Tennessee River.

Both forms of this mussel are now found only in portions of the Tennessee, Cumberland, Clinch, and Powell Rivers. Since 1918 only three live specimens have been reported from the Tennessee River. In 1981, five live specimens were reported from the Cumberland River, 16 from the Clinch River, and six from the Powell River. These figures provide a measure of relative abundance but do not reflect the actual population size.

Threats

The reasons for the decline of these mussels are not well understood, but stream damming and channeling, siltation, and pollution are thought to be major factors. Dams and reservoirs flood some habitats, reduce water flows in others, alter water temperatures, and increase siltation—all of which have a negative impact on mussels. The effects of pollution are intensified for filter feeders, because large quantities of water are drawn through the mussel's feeding system to extract food.

Conservation and Recovery

Transplantation of mussels from larger, more viable populations to smaller populations will be attempted. Since the largest concentrations of dromedary pearly mussels are in the Clinch and Powell Rivers, the identification, survey, and protection of these populations will be the first priority for recovery. As abundance increases, the U. S. Fish and Wildlife Service will attempt to reestablish mussel populations in at least three additional streams.

Sections of the Clinch and Powell Rivers are probably eligible for "scenic river" status under the National Wild and Scenic Rivers Act. If so designated, the law would provide additional protection for these mussels and their habitat. The state of Tennessee has designated portions of the Tennessee and Cumberland Rivers and the Clinch and Powell Rivers as mussel sanctuaries.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Center Dr.
Hadley, Massachusetts 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8308
http://northeast.fws.gov/

References

Bates, J. M., and S. D. Dennis. 1978. "The Mussel Fauna of the Clinch River, Tennessee and Virginia." Sterkiana 69/70: 3-23.

Dennis, S. D. 1981. "Mussel Fauna of the Powell River, Tennessee and Virginia." Sterkiana 71: 1-7.

French, John R. P., III. November, 1990. "The Exotic Zebra Mussel: A New Threat to Endangered Freshwater Mussels." Endangered Species Technical Bulletin 15 (11).

Jenkinson, J. J. 1981. "The Tennessee Valley Authority Cumberlandian Mollusk Conservation Program." Bulletin of the American Malacological Union, 1980 : 62-63.

U. S. Fish and Wildlife Service. 1983. "Dromedary Pearly Mussel Recovery Plan." U. S. Fish and Wildlife Service, Atlanta.