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Actinonaias ligamentina

What do they look like?

The mucket grows up to 15 cm (six inches), and is long and oval in shape. The shell is usually thick, heavy, and compressed. The front end is rounded and the rear end is bluntly pointed.

The outer shell layer (periostracum) is smooth. The color is yellow to yellow-brown with green rays. Older muckets tend to be more brown.

On the inner shell, the left valve has two tooth-like structures, which are heavy, large, and serrated. The inside surface (nacre) is white but occasionally it has a pink or salmon tint and is iridescent at the rear end.

In Michigan, this species can be confused with the fat mucket. Muckets tend to be more elliptical and compressed than fat muckets.

  • Sexual Dimorphism
  • sexes shaped differently
  • Range length
    15 (high) cm
    5.91 (high) in

Where do they live?

The mucket is found in the Mississippi River drainage from New York through Wisconsin, and from Minnesota south through eastern Texas and Alabama. In the St. Lawrence drainage, it is found in tributaries from Lake Michigan to Lake Ontario.

In Michigan this species is found in rivers in the lower peninsula, as far north as the Muskegon, Cass, and Chippewa Rivers. Historically it was common on the Grand River and its drainages. The mucket was also fairly common in rivers of the Lake Erie drainage, including the Huron, Raisin, and Clinton Rivers. (Burch, 1975)

What kind of habitat do they need?

The mucket is usually found in medium to large rivers, usually in areas with fairly good flow. The substrates it prefers include sand and/or gravel. (Cummings and Mayer, 1992; van der Schalie, 1938; Watters, 1995)

  • These animals are found in the following types of habitat
  • freshwater
  • Aquatic Biomes
  • rivers and streams

How do they grow?

Fertilized eggs are held in the water tubes for up to 11 months. The develop into larvae, called "glochidia", while inside the tubes. The glochidia are then released into the water where they must attach to the gill filaments or body surface of a host fish. After the glochidia attach, the fish's skin tissue grows over the glochidia. The glochidia then grows on the fish and transforms into a juvenile mucket within a few days or weeks. After it transforms, the young mucket falls of its host fish and falls to the bottom of the river. While on the river substrate, it develops into an adult.

How do they reproduce?

Mussels in this family (Unionidae) reproduce with both sexes (a male and a female). Females release larvae rather than eggs (they are viviparous).

Reproduction is stimulated by increasing water temperatures. Males release sperm into the water. The sperm is taken up by females through the water current. Females have to take in water through their respiratory valve to breath and the sperm comes in with that water. The female's eggs are then fertilized inside of her and pass into her gills where they develop into "glochidia" (larvae).

In the Huron River, female muckets are pregnant from early August to mid-June. They release their glochidia into the water in the summer after they are fertilized.

  • How often does reproduction occur?
    The mucket breeds once in the warmer months of the year.
  • Breeding season
    In Michigan, the breeding season is likely late June through July.
  • Range gestation period
    10 (high) months

Females hold fertilized eggs in water tubes until they develop into larvae (glochidia). After the female releases the glochidia there is no more parental help for the young.

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

How long do they live?

The age of mussels can be determined by looking at annual rings on the shell. However, nobody has gathered data on muckets to know how long their average lifespan is.

How do they behave?

Mussels generally stay in one place, although they may move when water levels or other conditions change. They may also swim up into the water column to spawn or release larvae (glochidia). This kind of movement is called vertical migration.

How do they communicate with each other?

The middle lobe of the mantle edge has most of a mussels sensory organs. Paired statocysts are in the mussel's foot. The statocysts help the mussel figure out directions: which way is up, as well as north, south, east, and west. Mussels are sensitive to temperature. They also may have some form of chemical sensitivity so that they can recognize fish hosts.

Glochidia respond to touch, light, and some chemical cues. In general, when touched or when a fluid is introduced, they will respond by clamping shut.

What do they eat?

Muckets are filter feeders. These mussels use small hair-like structures (cilia) to pump water into the incurrent siphon where food is caught in a mucous lining. Food particles are sorted and then directed to the mouth. Mussels eat mostly algae, but also take in bacteria, protozoans, and other organic particles.

The parasitic larval (glochidial) stage absorbs blood and nutrients from fish hosts after they attach to the skin or gills.

What eats them and how do they avoid being eaten?

Mussels in general are preyed on by muskrats, raccoons, minks, otters, and some birds. Juvenile mussels are probably also fed on by fish, including freshwater drum, sheepshead, lake sturgeon, spotted suckers, redhorses, and pumpkinseed sunfish.

Mussel reproduction and death is affected by certain parasites, including mussel-specialist mites, trematodes, and chironomids feeding on gill and mantle tissue.

What roles do they have in the ecosystem?

The glochidia stage of the mucket exists as a parasite on a fish. The glochidia can attach to almost any fish, but it will only transform to a juvenile if it attaches to a suitable host.

It is hard for scientists to tell exactly which fish are suitable hosts for muckets. They have to use both lab studies and collect samples from rivers. Based on these studies, scientists are confident that the following fish serve as suitable hosts for mucket larvae (glochidia): green sunfish, white crappie, smallmouth bass, largemouth bass, sauger, yellow perch and white bass. It's also possible that mucket larvae can parasitize banded killifish, central stonerollers, silverjaw minnows, black crappies, orange spotted sunfish, rock bass and Tippecanoe darters.

Species (or larger taxonomic groups) used as hosts by this species

Do they cause problems?

There are no significant negative impacts of mussels on humans.

How do they interact with us?

Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.

Are they endangered?

Muckets don't have any federal protection, but are listed as endangered in Kansas and threatened in Minnesota.

Some more information...


Renee Sherman Mulcrone (author).


Arey, L. 1921. An experimental study on glochidia and the factors underlying encystment. J. Exp. Zool., 33: 463-499.

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Burch, J. 1975. Freshwater unionacean clams (Mollusca: Pelecypoda) of North America. Hamburg, Michigan: Malacological Publications.

Cummings, K., C. Mayer. 1992. Field guide to freshwater mussels of the Midwest. Champaign, Illinois: Illinois Natural History Survey Manual 5. Accessed August 25, 2005 at

Cummings, K., G. Watters. 2004. "Mussel/Host Data Base" (On-line). Molluscs Division of the Museum of Biological Diversity at the Ohio State University. Accessed September 21, 2005 at

Graf, D. 2002. Historical biogeography and late glacial origin of the freshwater pearly mussel (Bivalvia: Unionidae) faunas of Lake Erie, North America. Occasional Papers of Mollusks, 6: 175-211.

Haag, W., M. Warren. 1997. Host fishes and reproductive biology of six freshwater mussel species from the Mobile Basin, USA. Journal of the North American Benthological Society, 16: 576-585.

Hoeh, W., R. Trdan. 1985. Freshwater mussels (Pelecypoda: Unionidae) of the major tributaries of the St. Clair River, Michigan. Malacological Review, 18: 115-116.

Hove, M. 2004. "Links to each state's listed freshwater mussels, invertebrates, or fauna" (On-line). Accessed September 21, 2005 at

Lefevre, G., W. Curtis. 1912. Experiments in the artificial propagation of fresh-water mussels. Proc. Internat. Fishery Congress, Washington. Bull. Bur. Fisheries, 28: 617-626.

Lefevre, G., W. Curtis. 1910. Reproduction and parasitism in the Unionidae. J. Expt. Biol., 9: 79-115.

Meglitsch, P., F. Schram. 1991. Invertebrate Zoology, Third Edition. New York, NY: Oxford University Press, Inc.

Oesch, R. 1984. Missouri naiades, a guide to the mussels of Missouri. Jefferson City, Missouri: Missouri Department of Conservation.

Watters, G. 1995. A guide to the freshwater mussels of Ohio. Columbus, Ohio: Ohio Department of Natural Resources.

van der Schalie, H. 1938. The naiad fauna of the Huron River, in southeastern Michigan. Miscellaneous Publications of the Museum of Zoology, University of Michigan, 40: 1-83.

University of Michigan Museum of ZoologyNational Science Foundation

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Mulcrone, R. 2005. "Actinonaias ligamentina" (On-line), Animal Diversity Web. Accessed April 17, 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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