The uniform shell thickness and hard, white nacre (shell lining) once made the yellow sandshell a favorite mussel for button manufacturing, before button makers switched to plastic. In Missouri, it is widespread, but is absent from south-flowing streams in south-central part of the state.
Externally, the yellow sandshell's shell is thick, inflated, elongate, with a pointed posterior end. The umbo (beak) is low and broadly rounded. The periostracum (thin outer layer) is shiny; younger mussels are yellowish green with fine green rays; adults are straw-colored with faint or no rays, becoming darker with age.
Inside the shell, the beak cavity is moderately deep; the pseudocardinal teeth are thin, elongate, serrate, and well-developed; the lateral teeth are long and straight to slightly curved; the nacre (mother-of-pearl layer) is white.
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 black sandshell (Ligumia recta) has a very dark periostracum. The fatmucket's shell is not as elongate and more inflated, typically with prominent rays.
Adult length: 3–6 inches.
Widespread, but absent from south-flowing streams in south-central Missouri.
Habitat and Conservation
Small to large rivers in slow to moderate current in sand, sandy mud, or fine gravel; also ponds, sloughs, and reservoirs.
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, longnose gar and other gars, sunfishes, largemouth bass, bluegill, crappies, and several other types. 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. This species, with its large, white shell, was very important for the button industry; its long, straight sides make it valuable for inlay work.
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.
