The plain pocketbook's shell is large, moderately thick, inflated, rounded to oval, with a blunt posterior end (males) or squared-off posterior end (females). Umbo is broad, raised above hinge line. Epidermis smooth, yellow or tan to yellowish-green with dark green rays. Inside shell beak cavity is deep; pseudocardinal teeth large, heavy, and serrate; lateral teeth high, blade-like, and short; nacre (lining) white, occasionally pink or salmon.
Similar species: Fatmucket’s shell is not as inflated and has a lower umbo. The mucket’s shell is more oval and compressed.
Adult length: 4–7 inches.
Almost statewide; found in all the major river systems in Missouri except for those in the far north and northwest.
Habitat and Conservation
Creeks to large rivers with quiet to swift current in gravel, sand and cobble — nearly any substrate except for moving sand.
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.
One of the most widespread and common mussels in our state.
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, white crappie, sauger, bluegill, yellow perch, and more. 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. This species was important in the button industry and is also valuable to the polished chip industry.
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. In this and other mussels in genus Lampsilis, the mantle flaps resemble a fish, which lures in host fish for the larval mussels.