Life History and Biology
Shell from a snuffbox mussel.
Credit: G. Thomas Watters/Ohio State University
DESCRIPTION: The snuffbox is a small to medium-sized mussel that reaches at least 3.5 inches in length. Male and female shells are shaped somewhat differently, with males being larger and longer than the truncated females. The shells of both species have a more inflated appearance than many freshwater mussels. The shell of female snuffbox are swollen on the anterior and have a sharp toothy margin. The shell surface of both sexes is typically smooth and yellowish or yellowish-green with darker squarish, triangular, or chevron-shaped marks. The color of the inside of the shell is white (mother-of-pearl).
RANGE: The snuffbox was once widespread and locally abundant in portions of the Great Lakes and Mississippi River basins. Records are known from 208 streams/lakes in 18 states although the species currently occurs in 73 streams. Habitat losses measured in the thousands of miles have occurred rangewide and the total range reduction and overall population losses for the snuffbox are about 90%.
In Pennsylvania snuffbox occur in portions of Allegheny River, French Creek, West Branch French Creek, Le Boeuf Creek, Muddy Creek, Conneaut Outlet, Little Mahoning Creek, Shenango River, and the Little Shenango River. The last population in Monongahela River watershed Snuffbox was apparently eliminated by a large mussel kill in Dunkard Creek in September 2009.
HABITAT: The snuffbox is found in small to medium-sized creeks to larger rivers and in lakes. It occurs in swift currents of riffles and shoals and wave-washed lakeshores over gravel and sand with occasional cobble and boulders, and generally burrows deep into the substrate except when spawning or attracting a host.
Adult snuffbox are sedentary filter feeders, obtaining oxygen and food directly from the water column or from water flowing through the substrate. Reproduction requires a stable, undisturbed habitat and a sufficient population of host fish to complete larval development. The logperch (Percina caprodes) and several other darters, are suitable host fish. The female snuffbox capture and hold the host fish by the head while ejecting larvae onto the fish’s gills. Among freshwater mussels, the snuffbox appear to be relatively short-lived (10 to 15 years).
REASONS FOR CURRENT STATUS: The genus Epioblasma has 25 recognized taxa, however, all but snuffbox are now either extinct or are listed as endangered. The life history traits that contribute to their sensitivity of this group of mussels are not clearly understood. Threats include exotic species, sedimentation; small population sizes; isolation of populations; livestock grazing; wastewater effluents; mine runoff; unstable and coldwater flows downstream of dams; gravel mining; and channel dredging. Many of the remaining populations are small and isolated and may be eliminated by single catastrophic events, such as toxic spills. Natural repopulation is impossible without human intervention.
Conservation actions that may benefit snuffbox are programs that support life history research and surveys and those that contribute to public understanding of the functions that sheepnose and other mussels play in the environment. Ensuring that regulations designed to protect water quality and aquatic habitats are fully implemented is vital to maintaining or enhancing sheepnose populations.