Missouri Department of Conservation
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Monkeyface

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

Thick, rounded or squared and inflated shell, with very prominent posterior ridge and lobed posterior margin; pustules (bumps) extend from umbo to posterior ventral margin, increasing in size. Narrow umbo, slightly raised above hinge line. Epidermis is yellowish-green, becomes brown with age; may have randomly scattered dark-green chevron marks. Inside shell has deep beak cavity; pseudocardinal teeth large, grooved and triangular; lateral teeth short, streaked and straight; nacre (lining) white, iridescent posteriorly. The prominent posterior ridge, pustules and knobs make this species easy to identify.

Size: 
Adult length: 2-4 inches.
Habitat and conservation: 
Medium to large rivers in relatively swift current in a stable clean-swept mix of coarse sand and gravel. A typical riffle species.
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: 
Rivers flowing off the Salem and Springfield plateaus (except for south-flowing streams in the central lower Ozarks); Mississippi and Salt rivers.
Status: 
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--this species uses green sunfish, bluegill and sauger. 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 used in the pearl button industry; also used in the cultured pearl 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.

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