Quadrula metanevra

Geographic Range

The monkeyface mussel, Quadrula metanevra, has a Nearctic distribution that encompasses the Mississippi River, Ohio River, and Tennessee River basins in the United States. Within Minnesota, this mussel used to reside in the Minnesota, the Mississippi and St. Croix Rivers. Monkeyface mussles are still found in the Mississippi river, but they are very rare within Minnesota waters. They are believed to have been extirpated from the Minnesota River. (Cordeiro, 2010; Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)


Monkeyface mussels may be found in medium to large rivers and streams. The monkeyface lives mostly in areas with mixed sand and gravel or gravel areas. (Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

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

Physical Description

The outer shell color of monkeyfaces can be a green or light to dark brown. The shells will usually have zig-zags with a green line. Monkeyface mussels can have v-shaped markings as well, but these are more likely to be on the younger mussels. The shell is thick, round or square-like. The shells also have a posterior edge that has large knobs. The inner shell is white on one end while the other end has iridescent colorings. Monkeyface get their name from the profile of the posterior edge of the shell, where the outline looks like the silouette of a monkey's face. (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


Fertilized monkeyface eggs are kept in the female’s gills and develop into glochidia (larvae). The females may contain glochidia in the gills from May to July in Minnesota. They are released and must attach to host fish at the gills or fins. The glochidia live as a parasite until they develop into juveniles. After transformation, the juveniles detach and become free living at the bottom of the stream or river. (Minnesota Dept. of Natural Resources, 2011)


Monkeyfaces spawn once a year in the spring. Males release gametes into the water that are taken up by the females. (Minnesota Dept. of Natural Resources, 2011)

Monkeyfaces are short-term brooders, meaning the females brood the larvae (glochidia) in their gills for only a few months in the summer. Reproduction starts with males releasing sperm directly into the water. The females downstream siphon the sperm into their gill chamber where the eggs are fertilized. The eggs mature in the gills to become glochidia. After being brooded for a few weeks or months, the glochidia are discharged into the water and will attach to a host fish. Brooding females were found in Tennessee between March and July. Glochidia drop from the host after they transform into juveniles. (Garner, et al., 1999; Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

  • Breeding interval
    Monkeyface mussels breed once yearly.
  • Breeding season
    Monkeyface mussels breed from May to July in Minnesota.

After the eggs are fertilized, the larvae, called glochidia, reside in the female's gills 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


The specific lifespan of the monkeyface is unknown. However, unionid mussels can be long-lived, with some mussel species living from decades to a century or more. (Minnesota Dept. of Natural Resources, 2011; US Army Corps of Engineers, 2005)


Monkeyface mussels are mostly sedentary, but can move in the sediment. The mussels can move via a hatchet shaped muscle that is extended between its two shells. (Minnesota Dept. of Natural Resources, 2011)

Home Range

The home range for monkeyfaces is unknown. Adult mussels move only a few meters from where they settle as juveniles.

Communication and Perception

Mussels in general are likely able to respond to chemical cues for spawning and other behaviors.

Food Habits

Monkeyface mussels are primarily filter feeders on algae, bacteria, protozoans and other organic matter present in the water. Monkeyfaces draw water in through their incurrent siphon and the food and oxygen are removed from their gills. The filtered water and waste are released from an excurrent siphon. (Minnesota Dept. of Natural Resources, 2011)


Unionid mussels in general are preyed upon by raccoons (Procyon lotor), muskrats (Ondotra zibethicus), and river otters (Lontra canadensis). Their hard shells and the muscles that hold them closed protect them from predators. (U. S. Fish and Wildlife Service, 2011)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Unionid mussels filter the water, provide substrate for aquatic insects and are a part of nutrient cycling in streams. Some of the known host fish for the glochidia of this species are the sunfish (Lepomis), sauger (Stizostedion canadens) and the bluegill (Lepomis macrohirus). (Minnesota Dept. of Natural Resources, 2011; National Park Service, 2006)

  • Ecosystem Impact
  • creates habitat
  • parasite
Species Used as Host
  • sunfish (Lepomis)
  • saugers (Stizostedion canadens)
  • bluegills (Lepomis macrohirus)

Economic Importance for Humans: Positive

Mussels in general are good indicators of water quality. This is because they do not move around much, can be long living and can be analyzed for contaminants that are in the water where they live. As the quality of the water declines so may the population of the mussels. Mussels have also been important in the cultured pearl industry. Thicker shelled species are harvested to seed pearl oysters. (National Park Service, 2006)

  • Positive Impacts
  • body parts are source of valuable material

Economic Importance for Humans: Negative

No negative economic impacts are known for monkeyface mussels.

Conservation Status

Quadrula metanevra is listed on several state threatened and endangered lists. Monkeyface mussles are endangered in Ohio, threatened in Wisconsin and Minnesota, and special concern in Arkansas. Due to decreasing water quality throughout its range this species may be becoming more rare. (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.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.


particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.


an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season


remains in the same area


non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Cordeiro, J. 2010. "Quadrula metanevra" (On-line). NatureServe. Accessed July 07, 2011 at http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Quadrula+metanevra+.

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 http://fwcb.cfans.umn.edu/personnel/staff/hove/State.TE.mussels.html.

Howells, R. 2010. "The Ecology of Fresh Water Mussels: Species of Interest" (On-line). Accessed July 07, 2011 at http://www.texasahead.org/economic_developer/endangered_species/mussel_presentations/EcologyOfFreshwaterMusselsOfInterest_Howells.pdf.

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 http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=IMBIV39080.

National Park Service, 2006. "Monkeyface" (On-line). Mississippi National River and Recreation Area. Accessed July 11, 2011 at http://www.nps.gov/miss/naturescience/musspagemonk.htm.

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 http://www.fws.gov/news/mussels.html.

US Army Corps of Engineers, 2005. "What is a Freshwater Mussel?" (On-line). Accessed July 07, 2011 at http://el.erdc.usace.army.mil/mussels/freshwater.html.