Plants and Animals

Planorbella smithi An aquatic snail (no common name)

Key Characteristics

This is a medium-sized freshwater snail with a discoidal (flat spiral) shell that is 0.5 to 0.75 in (1.2 to 1.9 cm) in diameter with a distinctive funnel-shaped rather than ascending spire and a narrow, deep umbilicus (depression on the central axis). The shell is also marked with regularly spaced transverse striations (appearing like growth rings).

Status and Rank

US Status:
State Status: E - Endangered (legally protected)
Global Rank: G5T2
State Rank: SH - Possibly extirpated

Occurrences

CountyNumber of OccurrencesYear Last Observed
Cheboygan21985

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 marl, sand, and mud substrates along the shores of large oligotrophic lakes.

Natural Community Types

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

Disturbance of marly shores through dredging, construction of breakwalls, marinas, and excessive lakeshore housing development and associated septic fields should be avoided. Snail-killing chemical molluscicides (copper sulfate or copper carbonate) that are used to treat lakes with swimmer's itch should be strictly avoided in lakes and streams occupied by rare snails. The introduction of fish species for recreational or commercial fishing is also strongly discouraged since many fish prey on aquatic snails and could greatly reduce populations or cause local, state, or global extirpation.

Active Period

Active from first week of July to first week of September

Survey Methods

This species can be surveyed using several techniques. One survey method consists of sweeping aquatic vegetation or scraping the substrate with a fine mesh aquatic sampling net or dip net (e.g., D-frame net). Another survey technique consists of vigorously shaking aquatic vegetation over a pail of water causing the various snails clinging to the plants to drop to the bottom of the pail. Visual surveys also can be conducted for this species by looking for snails attached to vegetation, rocks, woody debris and other cover. Glass bottomed buckets may be used to see snails clinging to vegetation or rocks underwater. Rocks, vegetation, and other cover also should be picked up, examined for snails, and returned to their original positions.

Sweeping with dip net

Survey Period: From first week of July to first week of September

Visual survey

Survey Period: From first week of July to first week of September

Shaking vegetation survey

Survey Period: From first week of July to first week of September

References

Survey References

  • Berry, E.G. 1943. The Amnicolidae of Michigan: Distribution, Ecology, and Taxonomy. University of Michigan Press, Ann Arbor. 68pp.
  • Clarke, A.H. 1981. The Freshwater Molluscs of Canada. National Museum of Natural Science, National Museums of Canada, Ottawa. 446pp.

Technical References

  • Burch, J.B. and Y. Jung. 1992. Freshwater snails of the University of Michigan Biological Station area. Walkerana 6(15).
  • Dillon, R.T. Jr. 2000. The Ecology of Freshwater Molluscs. Cambridge University Press, Cambridge, UK. 509pp.