The snuffbox has been classified as endangered in Missouri and federally. It has a very limited range in southeastern Missouri and the Ozarks, primarily in the Bourbeuse, Meramec, and St. Francis rivers.
Externally, the snuffbox's shell is small, fairly solid, triangular (in males) to somewhat elongate (in females) and inflated (particularly in females). The anterior end is rounded; the posterior end is truncated (in males), or expanded (in females). The dorsal and ventral margins are straight to slightly curved. The posterior ridge is sharply angled; the posterior slope is wide, expanded, and ribbed (especially in females). The umbo (beak) is swollen and slightly elevated above the hinge line. The beak sculpture consists of 3 or 4 faint, double-looped bars. The periostracum (thin outer layer) is yellow or yellowish green, with numerous dark green rays, blotches, or chevron-shaped (V-shaped) markings.
Inside the shell, the beak cavity is fairly deep. The pseudocardinal teeth are elevated, roughened, relatively thin, and compressed, with 2 teeth in the left valve and 2 in the right, with the front one being thinner and much smaller. The lateral teeth are very short, slightly curved, serrated, and elevated. The nacre (mother-of-pearl layer) is pearly white, iridescent posteriorly.
For a fuller introduction to Missouri’s native freshwater mussels, and to learn the terms for their anatomy, see their group page.
Similar Species: The elktoe, deertoe, and fawnsfoot (Truncilla donaciformis) are most similar.
Adult length: up to 2½ inches.
A very limited range in southeastern Missouri and the Ozarks, primarily the Bourbeuse, Meramec, and St. Francis rivers.
Habitat and Conservation
Medium to large rivers in clear water with gravel riffles, usually buried in the gravel.
Food
Freshwater mussels consume algae, bacteria, and fine particles of decaying organic matter. They extract nutrients and oxygen from water drawn into the body cavity through a specialized structure called the incurrent siphon; sediment, undigested food, and waste (called pseudofeces) are expelled through the excurrent siphon.
Status
A species of conservation concern: classified as endangered in Missouri and federally.
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. The snuffbox's principal fish host is the logperch, though it has also been recorded on certain types of sculpins and a few other fish. The tiny mussel eventually breaks away and floats to the bottom of the stream, and the cycle repeats.
Human Connections
Mussels play important roles in maintaining the health of Missouri’s water resources:
- As food for fish, they are important for Missouri’s fisheries. Small mammals and some birds eat them, as well.
- They filter algae, bacteria, and other particles from the water, improving water quality and cycling nutrients and energy in streams and lakes. Clean water is necessary for people and nature.
- Because mussels are sensitive to habitat disturbance and pollution, they are good indicators of the overall health of aquatic ecosystems and water quality.
The shells of several types of mussels were an important resource historically for button manufacture. Some species are still commercially important in the cultured pearl and jewelry industries.
The snuffbox is a small shell of unusual shape and beauty.
Ecosystem Connections
Native freshwater mussels provide vital functions in aquatic ecosystems:
- They are an important food source for many species of fish, wildlife, and other invertebrates.
- Their shells, both while the animal is alive and after it dies, provide habitat for other organisms.
- As filter feeders, individual mussels can filter a significant amount of water per day, but not all of what they remove is eaten. What they don’t eat is combined with mucus into packets. These pseudofeces packets are eaten by some fish and invertebrates.
Freshwater mussels depend on healthy populations of certain types of fish to complete their life cycle. Although as larvae they temporarily parasitize these fish, the harm to the fish is negligible.
