Ebonyshell

Fusconaia ebena
Endangered
Species of Conservation Concern
Family

Unionidae (freshwater mussels) in the phylum Mollusca

Description

Shell solid, heavy, rounded or oval, and inflated. Anterior end rounded, posterior end rounded or bluntly pointed. Dorsal margin slightly rounded, ventral margin curved, occasionally straight. Umbos low, inflated, about even with hinge line and curved downward. Beak sculpture consists of a few very weak ridges, apparent only in extremely small shells. Shell smooth with slightly elevated ridges indicating periods of growth. Periostracum rayless, light brown in young shells, becoming dark brown to black in older individuals.

Pseudocardinal teeth very heavy and well developed; two in the left valve, two in the right. Lateral teeth serrated and curved; two in the left valve, one in the right. Beak cavity very deep. Nacre pearly white, iridescent posteriorly.

Similar species: pigtoes (Fusconaia and Pleurobema)

Size

Adult length: up to 4 inches.

ebonyshell_interior_03-11-1.jpg

Photograph of Ebonyshell freshwater mussel shell interior view
Ebonyshell (Inside of Shell)
Habitat and conservation

Usually found in rivers with swift current and a substrate of fine gravel to cobble.

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.

image of Ebonyshell Distribution Map
Distribution in Missouri

Has been found in the Mississippi, Meramec, Osage, and Little Black rivers.

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 skipjack, green sunfish, largemouth bass, and more. 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. The ebonyshell was one of the most valuable to 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.