Villosa iris
Rainbow

Key Characteristics

The rainbow is a small (to 3 inches), elongate mussel with a relatively thin shell. The beak sculpture has 4 to 6 distinct double-looped bars. The cardinal teeth are small, triangular, and somewhat divergent; there are 2 in the left valve and 2 in the right valve. The shell is yellow or greenish-yellow with dark green rays. The nacre is silvery white and highly iridescent on the posterior half.

Status and Rank

  • State Status: SC
  • State Rank: S3
  • Global Rank: G5Q

Occurrences

County NameNumber of OccurrencesYear Last Observed
Allegan1
Alpena21932
Arenac1
Barry32010
Berrien21934
Branch12000
Calhoun72000
Cass22009
Clinton72010
Eaton82002
Genesee22001
Gladwin11926
Gratiot52010
Hillsdale192005
Huron21942
Ingham102002
Ionia82015
Iosco1
Jackson152010
Kalamazoo41960
Kent72015
Lapeer21926
Lenawee152004
Livingston52007
Macomb172011
Mecosta22002
Menominee11927
Midland42012
Missaukee12002
Monroe152000
Montcalm62015
Muskegon1
Oakland132011
Ogemaw11926
Ottawa11929
Roscommon42002
Saginaw42011
Sanilac52009
Shiawassee52001
St. Clair212011
St. Joseph102013
Tuscola62004
Van Buren42009
Washtenaw112010
Wayne62007
Distribution map for Villosa iris

Updated 1/31/2017. 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 rainbow occurs in coarse sand or gravel in small to medium streams.

Specific Habitat Needs

Sand and gravel substrates needed in Inland Lake, Littoral, Benthic, Inland Lake, Pelagic, Benthic, Great Lake, Littoral, Benthic Sand and gravel substrates; moderate currents needed in Headwater Stream (1st-2nd order), Riffle, Headwater Stream (1st-2nd order), Pool, Headwater Stream (1st-2nd order), Run, Mainstem Stream (3rd-4th order), Riffle, Mainstem Stream (3rd-4th order), Pool, 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

Like other mussels, threats to the rainbow 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

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Jul 20, 2017]

More Information

See MNFI Species Abstract

References

Survey References

Technical References

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