Species of Conservation Concern
Scientific Name
Leptodea leptodon
Unionidae (freshwater mussels) in the phylum Mollusca

Shell relatively small, elongate, thin, and compressed. Anterior end rounded, posterior end pointed. Dorsal margin straight, ventral margin straight to broadly curved. Umbos small and low, about even with the hinge line. Beak sculpture, if visible, of 4 or 5 double-looped ridges. Shell smooth, yellowish-green or brown, with numerous faint green rays.

Pseudocardinal teeth reduced to a small thickened ridge. Lateral teeth moderately long; 2 low, indistinct lateral teeth in left valve, 1 fine tooth in the right. Beak cavity very shallow or absent. Nacre pinkish white or light purple and highly iridescent.

Similar species: Fragile papershell


Adult length: up to 4 inches.

Where To Find
Scaleshell Distribution Map

Found only in the Gasconade and Meramec river basins.

Occurs in clear, nonpolluted riffles with moderate current and firm gravel, cobble or sand substrates.

Algae and fine particles of decaying organic matter; extracts nutrients and oxygen from water drawn into the body cavity through a specialized gill called the incurrent siphon; sediment and undigested waste are expelled through the excurrent siphon.

Listed as endangered by both the Missouri Department of Conservation and the U.S. Fish and Wildlife Service. Current threats include loss of habitat, competition from exotic zebra mussels, and overharvesting and illegal collection.

Life Cycle

Males release sperm directly into water. Females downstream siphon sperm into the gill chamber, where eggs are fertilized. Eggs mature into larvae (called glochidia), which discharge into the water and attach to host fish. The tiny mussel eventually breaks away and floats to the bottom of the stream, and the cycle repeats.

Mussels are excellent biological indicators of water quality because they are long-lived and relatively immobile, accumulating contaminants in water that can be scientifically analyzed.

Mussels act as nature's ā€œvacuum cleaners,ā€ filtering and cleansing polluted waters. They are also an important food source for other species in the aquatic environment.

Media Gallery
Similar Species
About Aquatic Invertebrates in Missouri
Missouri's streams, lakes, and other aquatic habitats hold thousands of kinds of invertebrates ā€” worms, freshwater mussels, snails, crayfish, insects, and other animals without backbones. These creatures are vital links in the aquatic food chain, and their presence and numbers tell us a lot about water quality.