White Heelsplitter

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

Shell is large, very compressed and rounded with a large wing above the hinge line. Umbo is flattened, small and not raised above hinge line. Green or greenish-brown epidermis, often with faint rays, becomes dark brown to black with age. Inside shell beak cavity shallow; pseudocardinal teeth large; lateral teeth bladelike and poorly developed; nacre (lining) bluish-white to white, iridescent posteriorly.

Similar species: Pink heelsplitter is more inflated with a pinkish-purple nacre. Pink papershell is generally smaller with a thinner shell and purple nacre.

Size: 
Adult length: 4-8 inches.
Habitat and conservation: 
Typically found in rivers having characteristics associated with larger rivers: streams that are usually sluggish and turbid with mud or mud-gravel, sand or fine gravel bottoms; also in lakes and ponds. Rarely, if ever, found in upper reaches of rivers flowing off the plateaus.
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: 
Widespread, except for south-central Ozarks. Prefers muddy, turbid streams of central Missouri and the tributaries of the Mississippi in eastern Missouri.
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—in this species, carp, green sunfish, largemouth and white crappie. 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. This species might be valuable for the polished chip 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.