Plants and Animals

Lyogyrus walkeri Canadian duskysnail

Key Characteristics

The Canadian duskyshell has an ovately conic, finely striated, tan-colored shell of about .1 inch in length, with 4 deeply sutured whorls and a large rounded aperature. The snail body is dark in color, particularly on the head.

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: SNR - Not ranked


CountyNumber of OccurrencesYear Last Observed
Cheboygan 1 1936

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.


This species inhabits inland lakes and slow moving streams with muddy substrates and a good deal of aquatic vegetation (Burch and Jung 1992).

Specific Habitat Needs

Aquatic vegetation needed in: Headwater stream (1st-2nd order), riffle; Headwater stream (1st-2nd order), pool; Headwater stream (1st-2nd order), run; Inland lake, littoral, benthic; Inland lake, pelagic, benthic; 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
  • Inland lake, littoral, benthic
  • Inland lake, pelagic, benthic
  • 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

Snails of the Amnicolid family, to which the Canadian duskysnail belongs, have shown significantly reduced reproductive success rate in waters with a ph below 5 and reduced calcium content, as may occur in areas affected by acid rain (Shaw and Mackie 1990). Efforts to decrease the burning of fossil fuels should therefore benefit this species and many other aquatic organisms. Herbicide/insecticide application (Kosanke et al. 1988), and other sources of  heavy metal and chemical pollution should be avoided near waterbodies containing vulnerable snail species, as these often result in reproductive failure and adult fatality (Besser et al. 2007, Gomot 1998) . Major alterations to aquatic habitats in the form of dredging, impoundment or channelization should be carried out only with monitoring and mitigation measures in place to account for affected freshwater species.

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).

D-frame net, dip net

Survey Period: From first week of June to first week of October

Time of Day: Daytime

Glass-bottom bucket less than waist deep water

Survey Period: From first week of June to first week of October

Time of Day: Daytime

SCUBA greater than waist deep water

Survey Period: From first week of June to first week of October

Time of Day: Daytime

Shaking vegetation survey

Survey Period: From first week of June to first week of October

Time of Day: Daytime


Survey References

  • Groves, K. 2007. Aquatic Spring Snail Survey and Habitat Analysis. USDA Forest Service.

Technical References

  • Besser, J.M., D.L. Hardesty, I.E. Greer, C.A. Mebane, D.R. Mount, and C.G. Ingersoll. 2007. Sensitivity of freshwater snails to contaminants: chronic toxicity tests with endangered species and surrogates. U.S. Geological Survey.
  • Burch, J.B. and Y. Jung. 1992. Freshwater snails of the University of Michigan Biological Station area. Walkerana 6(15).
  • Gomot, A. 1997. Toxic Effects of Cadmium on Reproduction, Development, and Hatching in the Freshwater Snail Lymnaea stagnalis for Water Quality Monitoring. Ecotoxicology and Environmental Safety 41(3):288-97.
  • Kosanke, G.J., W.W. Schwippert, and T.W. Beneke. 1988. The impairment of mobility and development in freshwater snails (Physa fontinalis and Lymnaea stagnalis) caused by herbicides. Comparative Biochemistry and Physiology Part C: Comparative Pharmacology 90(2):373-79.
  • Shaw, M.A. and G.L. Mackie. 1990. Effects of Calcium and pH on the Reproductive Success of Amnicola limosa (Gastropoda). Canadian Journal of Fisheries and Aquatic Sciences 47:1694-99.