The spectaclecase has an elongated and compressed outer shell with rounded ends; somewhat pinched in the middle. Umbo is slightly elevated above hinge line. Epidermis is flaky and dark brown to black. Inside shell has a shallow beak cavity. Pronglike pseudocardinal teeth with poorly developed lateral teeth. Nacre (lining) white, iridescent posteriorly.
Similar species: The black sandshell has a sharply pointed posterior and lacks a flaky epidermis. The adult spike (or ladyfinger) is neither as elongate nor pinched in shape.
Adult length: 5–8 inches.
Tributaries of the Missouri and Mississippi rivers, also the Salt River.
Habitat and Conservation
Medium to large rivers, in reduced current adjacent to swift water, among boulders, or in patches of gravel, sand, and cobble. Live in large groups with up to 100 per square yard.
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.
Fairly common but vulnerable, as the population is concentrated mostly in the Meramec and Gasconade rivers. Degrading water quality and watershed destabilization could easily interfere with the survival of this species. A Missouri species of conservation concern.
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.
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.
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.