Plants and Animals

Venustaconcha ellipsiformis Ellipse

Key Characteristics

The ellipse is a small (to 3 inches) elliptical mussel with a relatively thick shell. The beaks are only slightly raised above the hinge line and the sculpturing consists of 3 to 4 concentric ridges drawn up in the middle. The lateral teeth are short, thick, and finely striated. The cardinal teeth are thick, triangular, and roughened. The shell is greenish-brown or yellowish-brown in color with wavy green rays on the posterior end. The nacre is bluish-white in the center and often tinged with a rusty salmon color.

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

Occurrences

CountyNumber of OccurrencesYear Last Observed
Allegan 1 2016
Barry 3 2013
Berrien 3 2009
Branch 2 1930
Calhoun 9 2018
Cass 2 1930
Clinton 3 2010
Eaton 5 2018
Genesee 1
Gladwin 12 1981
Gratiot 3 2015
Hillsdale 2 2018
Ingham 10 2018
Ionia 10 2015
Isabella 4 2015
Jackson 12 2018
Kalamazoo 3 2012
Kent 10 2017
Leelanau 1 2000
Livingston 1 1959
Mecosta 1 2015
Midland 3 2015
Montcalm 9 2015
Muskegon 1
Oakland 1 2013
Ogemaw 3 1981
Saginaw 2 2011
Shiawassee 5 2001
St. Joseph 8 2016
Tuscola 6 2011
Van Buren 7 2009
Washtenaw 1 2000

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 ellipse occurs in the swift currents of riffles or runs of clear, small to medium sized streams in gravel or sand and gravel substrates.

Specific Habitat Needs

Gravel substrate 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), pool; Mainstem stream (3rd-4th order), run; Mainstem stream (3rd-4th order), riffle.

Natural Community Types

  • Headwater stream (1st-2nd order), riffle
  • Headwater stream (1st-2nd order), pool
  • Headwater stream (1st-2nd order), run
  • Mainstem stream (3rd-4th order), pool
  • 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

Like other mussels, threats to the ellipse 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

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

  • Cummings, K.S. and C.A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5, Champaign. 194pp.
  • Oesch, R.D. 1984. Missouri Naiades: a Guide to the Mussels of Missouri. Conservation Commision of the State of Missouri, Jefferson City. 270pp.
  • Smith, P.W. 1971. Illinois streams: A classification based on their fishes and an analysis of factors responsible for the disappearance of native species. Illinois Natural History Survey Biological Notes 76: 1-14.