Plants and Animals

Carychium nannodes File thorn

Key Characteristics

The file thorn is a land snail characterized by a minute (to .06 inches long), elongate, smooth, translucent white shell with 4-5 whorls. The body is whitish with the head featuring a snout-like protuberance and eyes located at the base of stout tentacles.

Status and Rank

US Status:
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: SNR - Not ranked

Occurrences

CountyNumber of OccurrencesYear Last Observed
Leelanau11993

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 file thorn prefers the mesic wooded areas of carbonate cliffs and floodplains (Nekola 2009).

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

An Ontario file thorn population suffered serious negative impacts after extensive recreational rock climbing altered its limestone cliff habitat (McMillan et al. 2003). Protecting sections of such habitat  from recreational overuse will benefit this and many other vulnerable plant and invertebrate species that depend upon the unique ecosystem of carbonate cliffs. Other factors that may contribute to the loss of file thorn habitat include quarrying and road construction (Nekola 2009). Further research into the distribution and specific site preferences of this species are needed before effective management can be implemented.

Active Period

Breeding from first week of May to fourth week of June

Survey Methods

As visual detection of this species is difficult, specimens are collected by litter sampling in suitable habitat. Samples are thoroughly heat-dried, soaked in water for a number of hours to separate the various components, and finally passed through a series of sieves. The shells are then able to be hand-picked from the remaining sample material (Nekola 2003).

Litter sampling

Survey Period: From first week of April to fourth week of October

Time of Day: Daytime

References

Survey References

  • Nekola, J.C. 2003. Large-scale terrestrial gastropod community composition patterns in the Great Lakes region of North America. Diversity and Distributions 9:55-71.

Technical References

  • Baker, F.C. 1939. Fieldbook of Illinois Land Snails. Illinois Natural History Survey Manual 2, Urbana, Illinois. 166pp.
  • Burch, J.B. 1962. How to Know the Eastern Land Snails. William C. Brown Company Publishers, Dubuque. 214 pp.
  • Burch, J.B. and A.S. Van Devender. 1980. Identification of Eastern North American Land Snails: The Prosobranchia, Opisthobranchia, and Pulmonata (Actophila). Society for Experimental and Descriptive Malacology. 80 pp.
  • Hubricht, L. 1985. The Distributions of Native Land Mollusks of the Eastern US. Field Museum of Natural History. Fieldiana: Zoology, No. 24.
  • McMillan, M.A., J.C. Nekola, and D.W. Larson. 2003. Effects of Rock Climbing on the Land Snail Community of the Niagara Escarpment in Southern Ontario, Canada. Conservation Biology 17(2):616-21.
  • Nekola, J.C. 2009. Conservation Prioritization of the Ontario and Quebec Land Snail Faunas. Final Report Submitted to: Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 120 pp.