Obovaria subrotunda
Round hickorynut

Key Characteristics

The round hickorynut is a small mussel (average size is 1 ¾ inch) that has a nearly perfect circular shell that is moderately thick and inflated. The shell is brown, smooth, and lacks rays. The beak is centrally located and the beak sculpture has slight, indistinct circular ridges, which are especially apparent on young individuals.

Status and Rank

  • State Status: E
  • State Rank: S1
  • Global Rank: G4

Occurrences

County NameNumber of OccurrencesYear Last Observed
Lenawee31930
Macomb71993
Monroe71977
Sanilac11934
St. Clair92013
Wayne82007
Distribution map for Obovaria subrotunda

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 round hickorynut is typically found in medium to large rivers and along the shores of Lake Erie and Lake St. Clair, near river mouths. The round hickorynut generally is found in sand and gravel substrates in areas with moderate flow.

Specific Habitat Needs

Sand, gravel, muddy substrates needed in Mainstem Stream (3rd-4th order), Run, River (5th-6th order), Riffle, Great Lake, Littoral, Benthic

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.

Feel free to send questions and comments to Brad Slaughter at slaugh14@msu.edu.

Management

Like other mussels, threats to the round hickorynut 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 Apr 26, 2017]

More Information

See MNFI Species Abstract

References

Survey References

Technical References

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