Megalonaias

highly endangered. Their habitat has been affected by siltation, erosion, polluted runoff, impoundment, channelization, and habitat fragmentation. Due to these environmetal changes, even common and widespread species have declined dramatically from historic levels. Mussels are important indicators of aquatic ecosystem health. Their complex life cycle requires a healthy fish community, stable substrates, and relatively clean water. Changes in water quality, channel stability, or fish density and diversity are usually reflected by a decline in abundance or a loss of species within the mussel community. Monitoring the health and diversity of the mussels within a drainage system is an important tool in aquatic ecosystem management.
water, which are drawn in by females through their incurrent siphon. Fertilized eggs are brooded in the female's gills, where they develop into tiny larvae called glochidia. Studies in the upper Mississippi River suggest that the washboard is tachytictic, with females brooding their young short-term before they are released as glochidia in October. Once the glochidia are expelled from the female's gills, they attach to fish gills or fins by clamping onto them with their valves. The glochidia live as parasites on the host fish until they develop into juvenile mussels, at which point they detach from the fish and fall to the streambed as free-living mussels. Host fishes for the glochidia of the washboard have been verified as the green sunfish (Lepomis cyanellus), black bullhead (Ameiurus melas), and the channel catfish (Ictalurus punctatus) (Woody and Holland-Bartells 1993).
rivers and in the Mississippi River below St. Anthony Falls (Grier 1922; van der Schalie and van der Schalie 1950). It was likely always rare in the Minnesota River, where surveys by Bright et al. (1990) found only 2 dead shells and no live individuals. The washboard is now very rare in the Mississippi (Thiel 1981; M. Davis, Minnesota DNR, pers. comm.) and St. Croix rivers (Heath 1990), comprising only 1% of the mussels identified by Hornbach et al. (1995). The washboard was listed as a threatened species in Minnesota in 1996.
valves that are thick and heavy. The posterior wing often has numerous ridges, especially in younger individuals, and the beak sculpture is comprised of well-developed, double-looped ridges. The entire surface of the shell is heavily sculptured with fine ridges and folds in the first few years of growth. The ridges become more pronounced with age. The outside of the shell is brown or black, and rayless. The pseudocardinal and lateral teeth are heavy, and the inside of the shell is white. The beak sculpture distinguishes the washboard from the rock pocketbook (Arcidens confragosus) and the threeridge (Amblema plicata). Its thick shell and heavy teeth also help distinguish it from the rock pocketbook.

References:
Hartfield, E. 2004. FRESHWATER MUSSELS OF

MDNR