Appalachian Elktoe

The Appalachian elktoe was listed as endangered in 1994, when only two populations were known to exist in the world - one in North Carolina’s Little Tennessee River and another in the Toe/Nolichucky rivers, straddling the North Carolina-Tennessee state line. Since then, additional populations have been discovered in western North Carolina, but over that same expanse of time, the Little Tennessee population functionally disappeared, and the Toe River population suffered setbacks. Today, the mussel is known from the Nolichucky/Toe, French Broad, and Little Tennessee River systems.  

Water quality and habitat degradation resulting from impoundments, stream channelization projects, and point and nonpoint sources of siltation and other pollutants appear to be major factors in reducing the species’ distribution and reproductive capacity. 

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Habitat 

The elktoe lives in relatively shallow, medium-sized creeks and rivers with cool, clean, well-oxygenated, moderate- to fast-flowing water. The species is most often found in riffles, runs, and shallow flowing pools with stable, relatively silt-free, coarse sand and gravel substrate associated with cobble, boulders, and/or bedrock. Stability of the substrate appears to be critical to the Appalachian elktoe, and the species is seldom found in stream reaches with accumulations of silt or shifting sand, gravel, or cobble.  

Food 

Mussels are filter feeders; they mainly eat phytoplankton, zooplankton, and bacteria suspended in the water. By drawing water inside their shells through a siphon, their gills filter out food and take in oxygen. 

Physical characteristics 

The Appalachian elktoe has a thin, kidney-shaped shell, extending to about 10 centimeters (4 inches). Juveniles generally have a yellowish-brown periostracum (outer shell surface), while in adults it’s usually dark brown to greenish-black. Although rays are prominent on some shells, particularly in the posterior portion of the shell, many individuals have only obscure greenish rays. The shell nacre (inside shell surface) is shiny, often white to bluish-white, changing to a salmon, pinkish, or brownish color in the central and beak cavity portions of the shell; some specimens may be marked with irregular brownish blotches.      

Reproduction 

The reproductive cycle of the species is like other native mussels. Males release sperm into the water, and the eggs are fertilized when the sperm are taken in by the females through their siphons during feeding and respiration. Females retain the fertilized eggs in their gills until the larvae (glochidia) fully develop. The glochidia are released into the water and must attach to the gills or fins of the appropriate fish species. They remain attached to their fish host for several weeks, drawing nourishment from the fish while they develop into juvenile mussels. They do not hurt their fish host. The juvenile mussels then detach from the fish host and drop to the bottom of the stream where they continue to develop, provided they land in a suitable place with good water conditions. This dependence on certain species of fish increases the mussels’ vulnerability to habitat disturbances. If the fish host is driven off or eliminated because of habitat or water quality problems, the mussels can’t reproduce and will eventually die out. 

Range

Available information suggests that the species once lived in most rivers and larger creeks of the upper Tennessee River system in North Carolina and the main stem of the Nolichucky River in Tennessee. Today it is found in the Cheoah, Tuckasegee, and Little Tennessee rivers of the Little Tennessee River basin; the Pigeon, Little, Mills, and French Broad rivers of the French Broad River system; and the North Toe, South Toe, Toe, Cane, and Nolichucky rivers of the upper Nolichucky River system.