Cumberland monkeyface (pearlymussel)

A medium-sized mussel roughly 2 inches in size, triangular to rectangular in shape with rounded corners. The valves are flat and display a deep beak cavity. The outer shell is a greenish yellow with spots, chevrons, zigzags, and rays, and is marked with numerous bumps and knobs. The inner shell surface is white, straw-colored, or salmon. The Tennessee and Cumberland River basins historically contained the greatest diversity of freshwater mussels anywhere in the world. Species specific to this area are referred to as "Cumberlandian". The Cumberland monkeyface is a Cumberlandian species restricted to the middle and upper Tennessee River system and has always been considered rare. It was placed on the federal threatened and endangered species list in 1976 as endangered. There are currently two populations of Cumberland monkeyface – one in the Powell River, crossing the Virginia-Tennessee state line, and one in the Duck River, entirely in Tennessee. Once known from Tennessee's Elk River, it hasn't been seen there in more than 40 years. Initial steps have been taken for it to be reintroduced to the Tennessee River in Alabama and the lower Holston and French Broad rivers, both in Tennessee. All surviving populations continue to be threatened by many of the same factors identified at the time of listing e.g., habitat fragmentation, loss, and alteration resulting from impoundments; operation of hydroelectric dams; mining; wastewater discharges; water withdrawal; competition and displacement by non-native species; and the runoff of silt and other pollutants from ground disturbance activities.

The species historical range included Alabama, Tennessee, Virginia. See below for information about where the species is known or believed to occur.

Habitat Requirements

Associated with clean, fast-moving water with relatively stable cobble, gravel, and sand substrates free of siltation. The mussel is usually found buried in the substrate in shallow riffle and shoal areas.

Food Habits

Suspension feeder on plankton; deposit feeder on bacteria and organic matter in substrate.

Movement / Home Range

Sedentary.

Reproductive Strategy

Males produce sperm which are discharged into the water and dispersed by currents. Any downstream female of the same species obtains these sperm during filter feeding. Fertilization of the female's eggs by the sperm occurs within the gills of the female. The fertilized eggs are retained in brood pouches, which are a modified section of the gills, to develop into larvae called glochidia. Once developed the females release the glochidia into the water. The glochidia must attach themselves to an appropriate fish host. After riding around on the fish for several weeks the glochidia will fall off the fish and settle on the bottom of river.

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