The fragile papershell's shell is thin, fragile, or brittle, and oblong to oval; there is a dorsal wing on young individuals that often erodes with age. The umbo (beak) is flattened and is barely above the hinge line. The periostracum is light yellowish tan to dirty yellow brown in adults; faint, narrow green rays may cover the shell.
Inside the shell, the beak cavity is shallow; the pseudocardinal teeth are small, thin, and reduced; the lateral teeth are smooth, of moderate length, very thin, bladelike, and high; the nacre (lining) is bluish white and iridescent throughout, and it may be pinkish dorsally.
For a fuller introduction to Missouri’s native freshwater mussels, see their group page.
Similar species: The pink papershell has a darker periostracum and purple to purplish-bronze nacre. The scaleshell is also similar.
Adult length: 3–6 inches.
Widespread and locally common where found; absent from southward-flowing streams in south-central Ozarks, just north of the Arkansas border.
Habitat and Conservation
Streams of all sizes in reduced current in pure mud to firm sand to mud-gravel and gravel. Does well in both clear and murky water.
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
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, usually freshwater drum. 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.
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.
