Thursday, September 23, 2010

Acipenser fulvescens

Family: Unionidae (Freshwater Mussels)
Synonyms: The elktoe has also been called the Ridged
Wedge-Mussel (Clarke 1981).
Total Range: The elktoe is widespread in North America although patchy in distribution. It occurs in the Great Lakes and St. Lawrence drainages south to the Tennessee drainage. It is most abundant in the center of its range (NatureServe).

While in Wisconsin, Illinois, Tennessee, Pennsylvaniaand New York the elktoe is considered apparentlysecure (S4), in other areas of its range it is less secure.The elktoe is considered possibly extirpated (SH) inAlabama and critically imperiled (S1) in Quebec, South Dakota, Kansas, Oklahoma and Vermont. InMinnesota, Missouri, Kentucky, West Virginia and Virginia, the elktoe is considered imperiled (S2) and in Ontario, Iowa and Indiana it is vulnerable (S3). In
several states, the elktoe is unranked (S?) (North Dakota, Nebraska, Arkansas, Ohio and Washington..

State Distribution: The elktoe has been found in several areas of Lower Michigan. Historically, it was present in the Grand River in Kent and Ionia Counties (Van der Shalie 1945). Recent surveys indicate that it still occurs in the Grand River, but in reduced numbers (Goforth et al. 2000). Live specimens have also been found in the St. Joseph River in Berrien and Calhoun Counties, St. Joseph (Maumee) River in Hillsdale County, and the Raisin River in Lenawee County (Badra and Goforth 2002, Goforth et al. 2001, Badra and Goforth 2001). During a survey of the Muskegon River watershed in the summer of 2002, live elktoe were found in Osceola County and spent shells were found in Clare and Missaukee Counties. Other recent surveys have found live elktoe in the Pine River in Montcalm County, the Maple River in Gratiot and Clinton Counties, the Looking Glass River in Clinton County and the Red Cedar River in Ingham County. Spent shells have been found recently in the Tittabawassee River in Saginaw County, the Thornapple River in Eaton County, the St. Joseph River in St. Joseph County, and the Black River in Sanilac County, but no live specimens have been recovered in these areas (Badra and Goforth 2002).

Recognition: The elktoe is a relatively small, thinshelled mussel, that may reach up to four inches in length. The shell of the elktoe is elongate, with arounded anterior end and an angled, square posteriorend. It has a prominent posterior ridge, and the posterior slope is ribbed. The umbo is large and centrally located above the hinge line. Beak sculpture is heavy and consists of three to four double-looped ridges. Lateral teeth are generally absent, and one, occasionally two, thin, elongate pseudocardinal teeth are present. The exterior color of the elktoe shell is yellowish green, with prominent broad dark green rays and dots. Thenacre is white and may have some salmon coloring nearthe beak. The foot of the elktoe is bright orange.

In Michigan, the elktoe may be confused most often with the strange floater (Strophitus undulatus). The strange floater lacks the rays and flecks of the elktoe, as well as the heavy beak sculpture. The elktoe may also be confused with the snuffbox (Epioblasma triquetra),slippershell mussel (Alasmidonta viridis) and deertoe (Truncilla truncata). These species lack the ribs found on the posterior dorsal area of the elktoe.

Habitat: The elktoe is found in small to large sized streams and small to medium rivers. It is a riffle species, preferring swifter currents over packed sand and gravel substrates. The elktoe is typically only found in clean, clear water (Cummings and Mayer 1992, Watters 1995, NatureServe).

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