Birgella subglobosus
Globe siltsnail

Key Characteristics

The glossy amber shell of the globe siltsnail is about .4 inches long, subglobose in shape, with 3-4 shouldered and finely striated whorls terminating in an elevated, rounded spire. The aperature is large and of a teardrop shape with a sharp outer lip.

Status and Rank

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

Occurrences

No known occurrences in Michigan

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

This species is found in large streams, rivers and lakes, often in deep water (Burch 1988, Burch and Tottenham 1980)

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

As waters with a pH below 5 are unable to support freshwater snail communities (Okland 1992), acid rain reduction efforts are an important management step. Exposure to heavy metal and chemical pollution from agricultural/urban runoff, industrial waste, and pesticide treatment is lethal to many species (Besser et al. 2007, Johnson 2009). River impoundments, channelization, and dredging alter necessary habitat, fragment snail populations, and increase sedimentation, smothering individuals and eliminating food items (Johnson 2009). Protecting healthy aquatic systems, and restoring those which have been degraded, is key to the successful management of freshwater snails.

Active Period

Active from first week of June to first week of October

Survey Methods

There are several effective methods for conducting aquatic snail surveys. Areas of coarse cobble substrate are best surveyed with a glass-bottomed bucket or scuba search, and hand collecting. Stones and sunken pieces of wood can be picked up, searched, and replaced. Dip net suveys are employed at soft substrate locations. Aquatic vegetation held over a bucket and vigorously shaken to remove individual snails is another technique (Groves 2007).

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Sep 24, 2017]

References

Survey References

Technical References

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