Villosa fabalis (Rayed bean) - MNFI Rare Species Explorer

Villosa fabalis

Rayed bean

Key Characteristics

The rayed bean is a small (to 1.5 inches), elliptical mussel with a solid shell. The hinge teeth are heavy. The shell is light to dark green or olive with heavy wavy rays and the nacre is white to whitish-blue, and often iridescent posteriorly.

Status and Rank

State Status: E - Endangered (legally protected)
US Status: LE - Listed Endangered
State Rank: S1 - Critically imperiled
Global Rank: G2 - Imperiled

Occurrences

County Name	Number of Occurrences	Year Last Observed
Hillsdale	1	1997
Lenawee	1	1941
Macomb	2	1935
Monroe	5	1984
Oakland	4	2009
St. Clair	8	2011
Wayne	4	2006

Updated 05/08/2013. 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 rayed bean occurs in small, shallow rivers, in and near riffles and often near aquatic vegetation. It also occurs along shallow, wave-swept shores of lakes. This species is often buried deep in sand and/or gravel.

Specific Habitat Needs

Sand or gravel substrates, macrophytes needed in Headwater Stream (1st-2nd order), Riffle, Mainstem Stream (3rd-4th order), Riffle, Inland Lake, Littoral, Benthic, Inland Lake, Pelagic, Benthic

Natural Community Types

Headwater stream (1st-2nd order), riffle
Mainstem stream (3rd-4th order), riffle
Inland lake, littoral, benthic
Inland lake, pelagic, benthic

Management

The rayed bean is historically rare in Michigan (Goodrich 1932). Like other mussels, threats to the rayed bean include: natural flow alterations, siltation, channel disturbance, point and non-point source pollution, and exotic species. Maintenance or establishment of vegetated riparian buffers can help protect mussel habitats from many of their threats. Control of zebra mussels is critical to preserving native mussels. And as with all mussels, protection of their hosts habitat is also crucial.

Survey Methods

These species bury themselves into substrates and so sampling may need to include excavation.

Aqua-scope searches
- Survey Period: From first week of April to first week of October
Snorkeling searches
- Survey Period: From first week of April to first week of October
SCUBA searches
- Survey Period: From first week of April to first week of October

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed May 20, 2013]

More Information

See MNFI Species Abstract

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

Burch, J.B. 1994. Mollusk: Species Accounts. Pages 395-410 in D.C. Evers, ed. Endangered and Threatened Wildlife of Michigan. University of Michigan Press, Ann Arbor.

Carman, S.M. 2001. Special Animal Abstract for Villosa fabalis (Rayed bean). Michigan Natural Features Inventory, Lansing, MI. 2pp.

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.

Evers, D.C. 1994. Endangered and Threatened Wildlife of Michigan. The University of Michigan Press, Ann Arbor. 412pp.

Goodrich, C. 1932. The Mollusca of Michigan. The University of Michigan Press, Ann Arbor. 121pp.

LaRocque, A.C. 1966-1970. Pleistocene mollusca of Ohio. Ohio Division of Geology Survey Bulletin, 62(1-4).

Ortmann, A.E. 1919. Monograph of the naiades of Pennsylvania. Part III. Systematic account of the genera of the naiades. Annals of the Carnegie Museum 8:222-365.