The mapleleaf occurs in most of Missouri, except for the south-central Ozarks. It lives in quiet sections of medium to large rivers and reservoirs in sand, mud, and fine gravel.
Externally, the mapleleaf's shell is thick, squared to rounded, slightly inflated; it usually has two rows of pustules (bumps) radiating from the umbo (beak) to the shell margin and separated by a sulcus (smooth depression); the anterior portion is usually smooth. The umbo is small and slightly raised above the hinge line. In juveniles, the periostracum (thin outer layer) is yellowish green with faint rays; with age, it darkens to medium to dark greenish brown or brown.
Inside the shell, the beak cavity is deep; the pseudocardinal teeth are serrate and well developed; the lateral teeth are long and straight; the nacre (mother-of-pearl layer) is 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 wartyback and pimpleback do not have a depression and are more rounded. The purple wartyback is generally more compressed and has purple nacre. The monkeyface has a row of knobs instead of a depression. The winged mapleleaf (Quadrula fragosa) and Gulf mapleleaf (Quadrula nobilis) are also similar.
Adult length: 3–5 inches.
Widespread, except for the south-central Ozarks.
Habitat and Conservation
Quiet sections of medium to large rivers and reservoirs in sand, mud and fine (small to medium) gravel. Favors larger rivers or streams with the characteristics of a big river. Can be found in rivers with clear or turbid 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.
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 catfishes, especially channel, blue, and flathead catfish. 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, including this species, were an important resource historically for button manufacture. Some species are still commercially important in the cultured pearl and jewelry industries.
Ecosystem 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. This species is one that was used to make buttons. Some species are still commercially important in the cultured pearl and jewelry industries.
