Planogyra asteriscus
Eastern flat-whorl

Key Characteristics

This tiny brown land snail has a flattened spiral shell that is 1.8 mm in diameter and 0.9 mm tall. The shell has prominent, thin ribs (transverse, raised ridges of considerable size on the shell surface) with sharp edges protruding from the shell as they spiral around the outer whorl. The shell has about 4 whorls with oblique ribs that are regularly spaced and showing fine growth lines between them. The aperture is oblique and rounded.

Status and Rank

  • State Status: SC
  • State Rank: S2S3
  • Global Rank: G4

Occurrences

County NameNumber of OccurrencesYear Last Observed
Alcona11950
Antrim11949
Charlevoix11929
Cheboygan31950
Chippewa11998
Delta11998
Gogebic1
Kalkaska11949
Keweenaw21998
Mackinac162013
Missaukee11949
Montmorency11950
Ontonagon1
Schoolcraft11998
Distribution map for Planogyra asteriscus

Updated 7/21/2017. 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 eastern flat-whorl inhabits calcareous wetlands with northern white-cedar, tamarack, speckled alder and sedges. The species is apparently not found in sphagnum-dominated wetlands. The species also is found on slopes and cliffs with white-cedar.

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

Land-use activities that remove forest canopy cover and alter critical habitat requirements such as cool microclimate and moisture availability should be avoided at occupied sites. These include activities such as timber harvesting, residential development, and road building. The species also is sensitive to excessive trampling and ORV use. Use of prescribed fire in occupied sites should be avoided, if possible, or prescribed fire should be applied very conservatively, leaving multiple refugia and using a burn interval of at least 15 years. Hydrological changes at occupied sites should be strictly avoided.

Active Period

Active from first week of April to fourth week of September

Survey Methods

Surveys can be conducted anytime during the growing season, but are most successful in spring and fall following rain showers or when the soil is moist, and during higher relative humidity conditions and cooler temperatures. Visual surveys consist of looking for individuals crawling on the ground, in moist leaf litter, and on or under woody debris. Litter sampling consists of collecting soil and leaf litter samples in the field and drying, sifting and looking for snail shells in the litter samples in the laboratory.

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Nov 22, 2017]

More Information

See MNFI Species Abstract

References

Survey References

Technical References

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