Elephantear (Elephant's Ear)

Family: 
Unionidae (freshwater mussels) in the phylum Mollusca
Description: 

Shell thick, solid, compressed to moderately inflated, triangular. Anterior end rounded, posterior end pointed. Dorsal margin slightly curved, ventral margin curved in young shells, becoming straight in older shells. Umbos low, usually not elevated above the hinge line. Beak sculpture, if visible, of two or three loops parallel to the growth lines, usually present only in very small shells. Posterior ridge prominent and sharply angled. Surface of the shell smooth. Periostracum reddish brown with faint green rays in small shells, becoming dark brown to black in adults.

Pseudocardinal teeth well developed; two in the left valve, one in the right. Lateral teeth short, roughened, and straight. Beak cavity very shallow. Nacre color variable, usually purple, occasionally pink or white.

Similar species: Spike, mucket

Size: 
Adult length: 3-6 inches.
Habitat and conservation: 
Large rivers in mud, sand or fine gravel.
Foods: 
Algae and fine particles of decaying organic matter; extracts nutrients and oxygen from water drawn into body cavity through a specialized gill called the incurrent siphon; sediment and undigested waste are expelled through the excurrent siphon.
Distribution in Missouri: 
Only occurs in the Ozark region of Missouri; today found only in the Meramec River.
Status: 
Endangered in Missouri; candidate for federal Endangered status.
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--this species uses the skipjack herring. 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. Because of its purple nacre, the elephantear was not sought after by the commercial button industry.
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.