Fragile Papershell

fragile papershell
Scientific Name
Leptodea fragilis
Unionidae (freshwater mussels) in the phylum Mollusca

Shell is thin, fragile or brittle, oblong to oval; dorsal wing on young, often eroding with age. Umbo is flattened and barely above hinge line. Epidermis is light yellowish-tan to dirty yellow-brown in adults; faint, narrow green rays may cover shell. Inside shell beak cavity is shallow; pseudocardinal teeth small, thin and reduced; lateral teeth smooth, moderate length, very thin, blade-like and high; nacre (lining) bluish-white, iridescent throughout and may be pinkish dorsally.

Similar species: Pink papershells have darker epidermis and purple to purplish-bronze nacre.


Adult length: 3-6 inches.

Where To Find
image of Fragile Papershell Distribution Map

Widespread and locally common where found; absent from southward-flowing streams in south-central Ozarks, just north of the Arkansas border.

Streams of all sizes in reduced current in pure mud to firm sand to mud-gravel and gravel. Does well in both clear and murky water.

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.

Common, although degrading water quality and watershed destabilization interfere with the survival of this and all freshwater mussels.

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--in this species, usually freshwater drum. 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 “vacuum cleaners,” filtering and cleansing polluted waters. They are also an important food source for other species in the aquatic environment.

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Similar Species
About Aquatic Invertebrates in Missouri
Missouri's streams, lakes, and other aquatic habitats hold thousands of kinds of invertebrates — 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.