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Quadrula metanevra

What do they look like?

Monkeyfaces are mussles with thick, round, or squarish shells. They get their name because the back edge of the shell looks like the face of a monkey. Their shells are green, light brown, or dark brown on the outside with green zig-zags. Younger monkeyfaces often have v-shaped markings, too. The shells also have bumps along the back edge. Inside, the shell is white on one side and iridescent on the other. (Cordeiro, 2010; Howells, 2010; Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    5.1 to 12.7 cm
    2.01 to 5.00 in
  • Average length
    8.9 cm
    3.50 in

Where do they live?

Monkeyface mussels live in the United States. They live in the Mississippi River, the Ohio River, the Tennessee River, and the rivers that drain into them. They used to be found in the Minnesota River, but are not found there anymore. (Cordeiro, 2010; Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

What kind of habitat do they need?

Monkeyface mussels live in medium and large rivers and streams. They mostly live mostly in places with sand and gravel or all gravel bottoms. (Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

  • Aquatic Biomes
  • rivers and streams
  • Average depth
    2 m
    6.56 ft

How do they grow?

Monkeyface eggs develop into larvae called glochidia inside the gills of their mother. Females might have larvae in their gills from May to July. The females release the larvae, and they attach to the gills or fins of fish. They stick themselves on the fish and keep growing until they become juveniles. Later, they let go of the fish and settle on the bottom of the stream or river, where they grow into adults. (Minnesota Dept. of Natural Resources, 2011)

How do they reproduce?

Monkeyfaces reproduce once a year in the spring. Males release reproductive cells into the water. Females take up these cells to fertilize their eggs. (Minnesota Dept. of Natural Resources, 2011)

Males release their reproductive cells into the water, and females downstream take them up to fertilize the eggs. The eggs hatch into larvae inside the gills of their mothers. They stay there for just a few months in the summertime. After a few weeks or months, they are released into the water and attach to a host fish. The larvae grow and develop attached to the host, and then let go and settle on the bottom. (Garner, et al., 1999; Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

  • How often does reproduction occur?
    Monkeyface mussels breed once yearly.
  • Breeding season
    Monkeyface mussels breed from May to July in Minnesota.

Monkeyface larvae grow in the gills of their mother for a few months until they are released into the water. (Minnesota Dept. of Natural Resources, 2011)

  • Parental Investment
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

How long do they live?

Scientists don't know the lifespan of monkeyfaces in particular. Freshwater mussels can live 20 to even 100 years or more. (Minnesota Dept. of Natural Resources, 2011; US Army Corps of Engineers, 2005)

How do they behave?

Monkeyface mussels mostly stay in the same place, but are able to move around on the bottom. They move using a muscle that they stick out from between their two shells. (Minnesota Dept. of Natural Resources, 2011)

Home Range

Scientists don't know the size of the area where monkeyfaces live. Most mussels don't move very much after they grow into adults.

How do they communicate with each other?

Mussels can probably respond to chemical signals that cause them to reproduce or other behaviors.

What do they eat?

All mussels are filter feeders, meaning that they strain bits of food out of the water. They pull water through pores and into their gills using cilia, which look like tiny hairs. The bits of food get trapped in their gills and then mucous moves the food to their digestive system. This way, they eat on algae, bacteria, protozoans and other bits of plants or animals found in the water. (Minnesota Dept. of Natural Resources, 2011)

What eats them and how do they avoid being eaten?

Freshwater mussels are eaten by raccoons, muskrats, and river otters. Their hard shells and the muscles that hold them closed protect them from predators. (U. S. Fish and Wildlife Service, 2011)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Freshwater mussels filter and clean the water where they live, and cycle nutrients through streams. They provide a surface for insects living in the water. Some of the fish their larvae attach to are sunfish, saugers, and bluegills. (Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

  • Ecosystem Impact
  • creates habitat
  • parasite
Species (or larger taxonomic groups) used as hosts by this species
  • sunfish (Lepomis)
  • saugers (Stizostedion canadens)
  • bluegills (Lepomis macrohirus)

Do they cause problems?

No negative economic impacts are known for monkeyface mussels.

How do they interact with us?

Mussels are used by researchers to test water quality. They don't move around much and live for a long time, so scientists can check their bodies for contaminants. When the water quality declines, the number of mussels might also decline. Mussels are also used for pearl oysters. (National Park Service, 2006)

  • Ways that people benefit from these animals:
  • body parts are source of valuable material

Are they endangered?

Monkeyface mussels are endangered in Ohio, threatened in Wisconsin and Minnesota, and under special concern in Arkansas. Their numbers might be decreasing because the water quality is getting worse. (Cordeiro, 2010; Hove, 2008; Minnesota Dept. of Natural Resources, 2011)


Jordy Veit (author), Minnesota State University, Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Renee Mulcrone (editor), Special Projects, Catherine Kent (editor), Special Projects.


Cordeiro, J. 2010. "Quadrula metanevra" (On-line). NatureServe. Accessed July 07, 2011 at

Garner, J., T. Haggerty, R. Modlin. 1999. Reproductive cycle of Quadrula metanevra (Bivalvia: Unionidae) in the Pickwick Dam tailwater of the Tennessee River. American Midland Naturalist, 141 (2): 277-283.

Hove, M. 2008. "State's listed freshwater mollusks, invertebrates, or fauna" (On-line). Accessed February 03, 2012 at

Howells, R. 2010. "The Ecology of Fresh Water Mussels: Species of Interest" (On-line). Accessed July 07, 2011 at

Minnesota Dept. of Natural Resources, 2011. "Quadrula metanevra (Rafinesque, 1820)" (On-line). Minnesota Department of Natural Resources Rare Species Guide. Accessed July 21, 2011 at

National Park Service, 2006. "Monkeyface" (On-line). Mississippi National River and Recreation Area. Accessed July 11, 2011 at

U. S. Fish and Wildlife Service, 2011. "Discover Freshwater Mussels: America's Hidden Treasure" (On-line). U. S. Fish and Wildlife Service News. Accessed July 11, 2011 at

US Army Corps of Engineers, 2005. "What is a Freshwater Mussel?" (On-line). Accessed July 07, 2011 at

University of Michigan Museum of ZoologyNational Science Foundation

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Veit, J. 2013. "Quadrula metanevra" (On-line), Animal Diversity Web. Accessed February 28, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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