Basis for Listing

The Dull Gloss snail (Zonitoides limatulus) is principally a species of the Ohio River valley, with outlying populations being known from the eastern Ozarks, southern Illinois, Michigan, upstate New York, and the Paleozoic Plateau (Hubricht 1985). It is known from less than a half-dozen sites in southeastern Wisconsin and from perhaps only two in Iowa. In Minnesota, it is known only from three locations in Houston and Olmstead counties (Frest 1983; Ostlie 1990).  These populations represent the northwestern range limit for this species.  The Dull Gloss was listed as a species of special concern in 2013.

  Description

The Dull Gloss has a shell ranging in diameter from 4.5–5.0 mm (0.18-0.20 in.) and 2.0-2.5 mm (0.08-0.10 in.) tall. The shell is white - translucent, with the top surface being covered by numerous, fine, radial striae. The aperture margin is thin (Pilsbry 1948). It may be most easily confused with the relatively common Forest Disc (Discus cronkhitei), which differs in its brown shell, with coarse striae. 

  Habitat

Throughout its range, the Dull Gloss is limited to mesic wooded cliffs, talus slopes, and rock outcrops. In Minnesota, it occurs on Southern Open Talus in The Blufflands Subsection of the Paleozoic Plateau Section of the Eastern Broadleaf Forest Province. While no information is available about the exact nature of the Minnesota locations, populations on similar sites in nearby Iowa live in decaying leaf litter between and under stones, where the ground flora is dominated by Laportea canadensis (wood nettle), Urtica dioica (stinging nettle), Impatiens pallida (spotted touch-me-not), Polymnia canadensis (leafcup), and various mosses and liverworts. While the Dull Gloss may occur in habitats adjacent to algific talus slopes, this species avoids such sites, presumably because their soil temperatures are too cold.

  Biology / Life History

Little specifically is known about the life-history behavior of the Dull Gloss. Field observations suggest that this species is a generalist consumer of fungus, and perhaps algae, that cover decaying leaf litter. Because individuals at all stages of development may be found at any given time within a colony, it is likely that they reproduce throughout the growing season, with individuals taking no more than eight weeks to reach adult maturity from hatching. It is also likely that individuals are able to live longer than one growing season. 

  Conservation / Management

One of the reported sites for the Dull Gloss in Minnesota occurs in Beaver Creek Valley State Park, while the others occur on private land. Maintenance of these populations will require that their talus slope habitats remain undisturbed, with adequate forested buffer being maintained upslope and downslope to maintain shading and high humidity levels on the ground surface. Recreation activities on these sites should also be limited.

  Conservation Efforts in Minnesota

No conservation efforts are currently being undertaken on the behalf of the Dull Gloss in Minnesota; however, some of the known sites for this species exist on publically-owned lands, which should offer some protection.

  References and Additional Information

Frest, T. J. 1983. Northern driftless area survey. Draft final report to the Minnesota Department of Natural Resources. 17 pp.

Hubricht, L. 1985. The distributions of the native land mollusks of the eastern United States. Fieldiana. Zoology; New Series No. 24, Field Museum of Natural History, Chicago Illinois. 191 pp.

Ostlie, W. R. 1990. Completion of the algific slope/maderate cliff landsnail survey in Minnesota. Final report submitted to the Division of Ecological Services, Minnesota Department of Natural Resources, St. Paul.. Unpaged.

Pilsbry, H. A. 1948. Land mollusca of North America (north of Mexico). Volume 2, Part 2. Academy of Natural Sciences of Philadelphia, Monograph No. 3. Philadelphia, Pennsylvania. 1113 pp.