Basis for Listing

The mucket mussel was once extremely important in the pearl button industry. Dawley (1947) reported that this species occurred in "all parts of the Mississippi drainage and in the Hudson Bay drainage", and while widely distributed in medium and large rivers, it was not present in large numbers. Specimens reported from the Red River of the North drainage are fat mucket (Lampsilis siliquoidea), a separate species. The mucket's widespread historical occurrence is supported by the distribution of dead shells found during surveys (Bright et al. 1988, 1990; Davis 1987). It is now common only in the St. Croix River and some of its tributaries (Doolittle 1988). It is apparently extirpated from the Minnesota River (Bright 1990) and many of its tributaries (Minnesota DNR, unpublished data), and occurs in only low densities in the Mississippi (M. Davis, Minnesota DNR, pers. comm.), Zumbro (Bright et al. 1988), Cannon (Davis 1987), and Otter Creek rivers. As the mucket mussel is now found alive in only a small number of drainages, it is vulnerable to habitat degradation and catastrophic events. For these reasons, the mucket was listed as a threatened species in Minnesota in 1996.

  Description

The mucket's shell is oblong, moderately thick, up to 15 cm (6 in.) long, and the posterior is sometimes bluntly pointed. The outside of the shell is yellowish to dark brown, with wide green rays often present, especially in young mussels. The beak sculpture is largely absent, and the pseudocardinal teeth are heavy and triangular. The mucket resembles the male fat mucket (Lampsilis siliquoidea) and the male plain pocketbook (L. cardium), but can be distinguished from these species by its uniformly oblong shape, heavier pseudocardinal teeth, and lack of beak sculpture.

  Habitat

The mucket mussel is known to inhabit medium to large rivers. Substrates that are most preferred include coarse sand and gravel (Parmalee and Bogan 1998).

  Biology / Life History

Mussels are long-lived animals. Members of many species may live for several decades and in some instances, a century or more. They spend most of their lives buried in the bottom sediments of permanent water bodies, and often live in multi-species communities called mussel beds (Sietman 2003).

Mussels are primarily sedentary, but they can move around with the use of their "foot", which is a hatchet shaped muscle that can be extended out between the valves (shells). A mussel will burrow its foot into the sediment and then contract it to pull itself slowly along the bottom of its aquatic habitat (Sietman 2003).

Mussels eat by filtering bacteria, protozoans, algae, and other organic matter out of the water. They draw water into their body through their incurrent siphon, remove food and oxygen with their gills, and then expel the filtered water through their excurrent siphon. Food particles are carried to the mussel's mouth by tiny hairlike cilia located on the gills. Waste is expelled through the excurrent siphon (Sietman 2003).

Mussels have a complex and distinctive reproductive cycle. Males release sperm into the water, which are drawn in by females through their incurrent siphon. Fertilized eggs are brooded in the female's gills, where they develop into tiny larvae called glochidia. The mucket is bradytictic, with females brooding their young long-term, from August through May, before they are released as glochidia (Parmalee and Bogan 1998). Once the glochidia are expelled from the female's gills, they attach to fish gills or fins by clamping onto them with their valves. The glochidia live as parasites on the host fish until they develop into juvenile mussels, at which point they detach from the fish and fall to the streambed as free-living mussels. Fish hosts for the mucket's glochidia include crappies (Pomoxis spp.), sunfish (Lepomis spp.), and bass (Micropterus spp.) (Watters 1994).

  Conservation / Management

The continued persistence of mucket populations in Minnesota is threatened by the hydrologic alteration of streams and their watersheds; the continuing decline in habitat conditions on the Mississippi River associated with its management as a navigation canal; and water and sediment pollution from non-point and point sources. Dams, channelization, and dredging increase siltation, physically alter habitat conditions, and block the movement of fish hosts. The mucket is also being impacted by the infestation of non-native zebra mussels (Dreissena polymorpha) in the Mississippi River and its tributaries. Zebra mussels can attach themselves in large numbers to the shells of native mussels, eventually causing death by suffocation.

  Conservation Efforts in Minnesota

A 10-year statewide mussel survey initiated by the Minnesota DNR in 1999 resulted in a better understanding of the mucket's ecology and current status in Minnesota. Additionally, six muckets were collected from zebra mussel infested habitats in the Mississippi River in 2000 and translocated into areas of the Mississippi River south of the Twin Cities, where habitats were devoid of zebra mussels. Efforts are also underway to propagate juveniles for restocking into areas where habitat has improved.

  References and Additional Information

Bright, R. C., C. Gatenby, D. Olson, and E. Plummer. 1990. A survey of the mussels of the Minnesota River, 1989. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources. 106 pp.

Bright, R. C., E. Plummer, and D. Olson. 1988. A survey of the mussels of the Zumbro River drainage, southeastern Minnesota. Report submitted to Minnesota Department of Natural Resources. 27 pp. + tables, figures, and appendices.

Davis, M. 1987. Freshwater mussels (Mollusca: Bivalvia: Unionidae) of the Cannon River drainage in southeastern Minnesota. Final report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. 21 pp. + figures and original data sheets.

Davis, M. 2007. Site reintroduction plan for Actinonaias ligamentina (mucket) and Epioblasma triquetra (snuffbox) at St. Paul, MN (Mississippi River at Hidden Falls). 7 pp.

Dawley, C. 1947. Distribution of aquatic mollusks in Minnesota. American Midland Naturalist 38:671-697.

Doolittle, T. C. J. 1988. Distribution and relative abundance of freshwater mussels in the Saint Croix National Scenic Riverway. Final report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resouces. Unpaged.

Parmalee, P. W., and A. E. Bogan. 1998. The freshwater mussels of Tennessee. The University of Tennessee Press, Knoxville, Tennessee. 328 pp.

Sietman, B. E. 2003. Field guide to the freshwater mussels of Minnesota. Minnesota Department of Natural Resources, St. Paul, Minnesota. 144 pp.

Watters, G. T. 1994. An annotated bibliography of the reproduction and propagation of the Unionoidea (Primarily of North America). Ohio Biological Survey Miscellaneous Contributions No. 1, Columbus, Ohio. 158 pp.