Plants and Animals
Alasmidonta marginata Elktoe
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
US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G4 - Apparently secure
State Rank: S3? - Vulnerable (inexact or uncertain)
Occurrences
| County | Number of Occurrences | Year Last Observed |
|---|---|---|
| Allegan | 8 | 2019 |
| Barry | 2 | 2010 |
| Bay | 1 | 1908 |
| Berrien | 6 | 2009 |
| Calhoun | 14 | 2019 |
| Cheboygan | 1 | 1913 |
| Clare | 1 | 2002 |
| Clinton | 8 | 2021 |
| Dickinson | 7 | 2017 |
| Eaton | 5 | 2002 |
| Genesee | 1 | Historical |
| Gladwin | 3 | 1981 |
| Gratiot | 7 | 2015 |
| Hillsdale | 5 | 2003 |
| Ingham | 9 | 2015 |
| Ionia | 39 | 2021 |
| Iron | 3 | 2019 |
| Isabella | 2 | 2015 |
| Jackson | 4 | 2012 |
| Kalamazoo | 14 | 2019 |
| Kent | 16 | 2021 |
| Lenawee | 13 | 2005 |
| Livingston | 4 | 2016 |
| Mackinac | 1 | 1941 |
| Macomb | 9 | 2012 |
| Manistee | 1 | 2011 |
| Mecosta | 1 | 1934 |
| Menominee | 10 | 2011 |
| Midland | 4 | 2020 |
| Missaukee | 2 | 2002 |
| Monroe | 11 | 2020 |
| Montcalm | 2 | 2015 |
| Newaygo | 2 | 1934 |
| Oakland | 6 | 2019 |
| Osceola | 3 | 2002 |
| Ottawa | 1 | Historical |
| Presque Isle | 2 | 1952 |
| Roscommon | 1 | Historical |
| Saginaw | 4 | 2011 |
| Sanilac | 10 | 2019 |
| Schoolcraft | 1 | 2019 |
| Shiawassee | 5 | 2001 |
| St. Clair | 13 | 2019 |
| St. Joseph | 17 | 2019 |
| Tuscola | 8 | 2015 |
| Van Buren | 1 | Historical |
| Washtenaw | 13 | 2018 |
| Wayne | 9 | 2020 |
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), run; Mainstem stream (3rd-4th order), riffle.
Natural Community Types
- Mainstem stream (3rd-4th order), run
- Mainstem stream (3rd-4th order), riffle
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 Recommendations
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
Glass-bottom bucket less than waist deep water
Survey Period: From first week of June to first week of October
SCUBA searches
Survey Period: From first week of June to first week of October
Snorkeling searches
Survey Period: From first week of June to first week of October
References
Survey References
- Cummings, K.S. and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5, Champaign. 194pp.
- Strayer, D.L. and D.R. Smith. 2003. A Guide to Sampling Freshwater Mussel Populations. American Fisheries Society Monograph 8, Bethesda. 103pp.
Technical References
- Carman, S.M. 2002. Special animal abstract for Alasmidonta marginata (Elktoe). Michigan Natural Features Inventory, Lansing, MI. 3pp.
- Cummings, K.S. and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5, Champaign. 194pp.
- Dillon, R.T. Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, UK. 509pp.
- Watters, G.T. 1993. A guide to the freshwater mussels of Ohio. Revised Edition. The Ohio Department of Natural Resources, Columbus. 106 pages.