Butterfly
Family:
Unionidae (freshwater mussels) in the phylum Mollusca
Description:
Shell is solid, thick, noticeably flattened and triangular with a prominent and sharply angled posterior ridge. Umbo is flattened on the sides, directed forward and slightly raised above hinge line. Epidermis is yellowish-brown with interrupted but distinct brown rays that appear as spots, bars, wavy patterns or V-shapes (chevrons). Inside shell beak cavity is shallow; pseudocardinal teeth large, grooved and triangular; lateral teeth serrate, short and straight; nacre (lining) white.
Similar species: Deertoe has a similar color pattern, but the shell is much more inflated and has a deeper beak cavity.
Size:
Adult length: 3-5 inches.
Habitat and conservation:
Large rivers with strong current in coarse gravel and sand.
Foods:
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.
Distribution in Missouri:
Most common in an east-west band of north-flowing tributaries of the Missouri River and in several Mississippi River tributaries.
Status:
Moderately common.
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.
Human connections:
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. Historically important in the button industry; also valuable in the cultured pearl and polished chip industries.
Ecosystem connections:
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.
Shortened URL
mdc.mo.gov/node/6475
