Alasmidonta marginata
Elktoe
Image of Alasmidonta marginata

Photo by David Stagliano 

Key Characteristics

The elktoe is a relatively small (to 4 inches), elongate, thin-shelled mussel. The beak is large and centrally located above the hinge line; beak sculpture is heavy and consists of three to four double-looped ridges. Lateral teeth are generally absent and one, occasionally two, thin, elongate cardinal teeth are present. The shell has a prominent posterior ridge and is yellowish green with broad dark green rays and dots. The nacre is generally white and the foot is bright orange.

Status and Rank

  • State Status: SC
  • State Rank: S3?
  • Global Rank: G4

Occurrences

County NameNumber of OccurrencesYear Last Observed
Allegan42000
Barry22010
Bay11908
Berrien62009
Calhoun42000
Clare12002
Clinton62010
Dickinson52009
Eaton52002
Genesee1
Gladwin31981
Gratiot42010
Hillsdale52003
Ingham82001
Ionia152011
Iron12008
Jackson42010
Kalamazoo32000
Kent142011
Lenawee132005
Livingston42008
Mackinac11941
Macomb72001
Mecosta11934
Menominee82011
Midland32011
Missaukee22002
Monroe82000
Newaygo21934
Oakland52007
Osceola32002
Ottawa1
Roscommon1
Saginaw32011
Sanilac92009
Shiawassee52001
St. Clair102011
St. Joseph82013
Tuscola52011
Van Buren1
Washtenaw112010
Wayne52006
Distribution map for Alasmidonta marginata

Updated 7/21/2017. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.

Habitat

The Elktoe is found in small to large sized streams and small to medium rivers. It is a riffle species, preferring swifter currents over packed sand and gravel substrates. The Elktoe is typically only found in clean, clear water (Cummings and Mayer 1992).

Specific Habitat Needs

Rocky substrates needed in Mainstem Stream (3rd-4th order), Riffle, Mainstem Stream (3rd-4th order), Run

Natural Community Types

Methodology

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management

The elktoe needs clean, fast-flowing water to survive. Therefore, changes to its habitat, such as river impoundment, siltation and channel disturbances, including dredging, negatively affect this species. Pollution from point (industrial and residential discharge) and non-point (siltation, herbicide and surface run-off) sources is also a threat to mussels and should be limited and monitored to insure compliance with the Clean Water Act. Control of zebra mussels is critical to preserving native mussels. It is essential to protect not only the habitat of the elktoe, but also the white sucker, northern hog sucker, shorthead redhorse, rockbass and warmouth, as they serve as hosts for the glochidia.

Survey Methods

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Nov 21, 2017]

More Information

See MNFI Species Abstract

References

Survey References

Technical References

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