Striatura ferrea E.S. Morse, 1864
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.
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.
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.