Rare Species Guide

  Basis for Listing

The Black Striate snail (Striatura ferrea) is common throughout New England and the Canadian maritime provinces. It also extends south along the Appalachian crest to North Carolina and Tennessee and west along the Great Lakes to Minnesota (Pilsbry 1948; Hubricht 1985). Only a single location, found in 1998 within the city of Duluth, has been reported from the state (Nekola et al. 1999). This population represents the western known limit of this species’ global range. It is rare in western Wisconsin and does not become of frequent occurrence until one reaches the western part of the Upper Peninsula of Michigan (Nekola 1998). The Black Striate was listed as a species of special concern in 2013.

  Description

The Black Striate has a shell approximately 3 mm (0.12 in.) in diameter by 1.5 mm (0.06 in.) tall. It has a relatively shallow spire and whorls that approximately double with each rotation. The shell is off-white and translucent, with a dull luster from the presence of irregular, low and perpendicular ribs and microscopic spiral lines (Pilsbry 1948). The spiral lines are especially noticeable on the initial 1-2 whorls and serve to most readily distinguish this species from the similar-looking Blue Glass Snall (Nesovitrea binneyana) that often lives in the same habitats.

  Habitat

In Minnesota, the Black Striate is found on a shaded basalt talus slope within a northern rich mesic hardwood forest in the North Shore Highlands Subsection of the Northern Superior Uplands Section of the Laurentian Mixed Forest Province (Nekola et al. 1999). At this site, it lives in decomposed leaf litter accumulations, often among boulders.

  Biology / Life History

Little, specifically, is known about the life-history behavior of the Black Striate. 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. 

The Black Striate is one of a small number of North American land snails that prefer moderately acidic and relatively base-poor habitats (Nekola 2010). Across its range, typical sites for this species include heathlands, sedge (Carex spp.) meadows, alder (Alnus rugosa) and tamarack (Larix laricina) swamps, northern white cedar (Thuja occidentalis), willow (Salix spp.), red maple (Acer rubrum), pine (Pinus spp.), hemlock (Tsuga canadensis), yellow birch (Betula lutea), and spruce-fir (Picea-Abies) forests. 

  Conservation / Management

The lone documented Black Striate site in Minnesota is adjacent to the southern section of the Superior Hiking Trail, presumably within public open space in the city of Duluth. The greatest concerns for the long-term survival of this population are recreational development, habitat alteration, and aerial pesticide drift. 

  References and Additional Information

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.

Nekola, J. C. 1998. Terrestrial gastropod inventory of the Niagaran Escarpment and Keewanaw volcanic belt in Michigan's Upper Penninsula. Final report submitted to the Natural Heritage Program, Michigan Department of Natural Resources, Lansing. 133 pp.

Nekola, J. C. 2002. Distribution and ecology of terrestrial gastropods in northwestern Minnesota. Final Report to 2001-2002 Natural Heritage and Nongame Research Program, Division of Fish and Wildlife, Minnesota Department of Natural Resources, St. Paul, Minnesota.

Nekola, J. C. 2004. Terrestrial gastropod fauna of northeastern Wisconsin and the southern Upper Peninsula of Michigan. American Malacological Bulletin 18:21-44.

Nekola, J. C. 2008. Land snail ecology and biogeography of eastern Maine. Final report submitted to Maine Department of Inland Fisheries & Wildlife and the Aroostook Hills and Lowlands Inventory, Augusta, Maine. 119 pp.

Nekola, J. C. 2010. Acidophilic terrestrial gastropod communities of North America. Journal of Molluscan Studies 76(2):144-156.

Nekola, J. C. In press. Acidophilic terrestrial gastropod communities of North America. Journal of Molluscan Studies.

Nekola, J.C., M. Barthel, P. Massart, and E. North. 1999. Terrestrial gastropod inventory of igneous outcrops in northeastern Minnesota. Final Report submitted to the Natural Heritage and Nongame Research Program, Minnesota Department of Natural Resources, St. Paul, Minnesota. 60 pp.

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.