The pink papershell occurs generally statewide but is most common in the Gasconade, Osage, Grand, Chariton, Lamine, North Fabius, and Salt rivers. It and the pink heelsplitter share a regional distribution and resemble each other.
Externally, the pink papershell's shell is thin, compressed, oval to rectangular, with a high, pronounced posterior wing in addition to an anterior wing. The umbo (beak) is not raised above the hinge line. The periostracum (thin outer layer) is shiny, light tan to olive brown, becoming darker brown with age; some rays may be present; light tan juveniles may have a greenish cast.
Inside the shell, the beak cavity is shallow; the pseudocardinal teeth are thin, small, and erect; the lateral teeth are thin, bladelike, and slightly curved; the nacre (mother-of-pearl layer) is light purple.
- The pink papershell has the same geographic distribution in Missouri as the pink heelsplitter, and it generally resembles that species, too. But as the name suggests, the pink papershell usually has a thinner shell and is smaller. Also, it prefers rather shallow water with a good current.
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 pink heelsplitter has a darker, thicker shell with a deep purple nacre and larger pseudocardinal teeth. The fragile papershell is light yellow with a darker area near the umbo and whitish to whitish-blue nacre, possibly with a pink tinge. The white heelsplitter is also similar.
Adult length: 3–6 inches.
Generally statewide; most common in Gasconade, Osage, Grand, Chariton, Lamine, North Fabius, and Salt rivers.
Habitat and Conservation
Shallow areas of medium to large rivers with slow current in silt, mud, or sand.
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.
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 the freshwater drum but also sometimes the white crappie. 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. Because of its relatively thin shell, this species has had little commercial use.
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.
