Listing
Nov 21, 1991
- Publication type: CNOR
- Population:
The interrupted rocksnail is a small to medium sized pleurocerid snail that historically occurred throughout the Coosa River drainage of Alabama and Georgia. It grows to about 20 millimeters (1 in) in length. The interrupted rocksnail lives attached to bedrock, boulders, cobbles and gravel. Individuals tend to move slowly, except in response to changes in water level. This species is currently found in the Oostanaula River.
The interrupted rocksnail may be ornamented by partial costae or folds in the surface of the shell. The shell is thick and subglobose, or not quite spherical. The spire or apex of the shell is very low and the aperture or shell opening is large, subrotund, and covered with an operculum when the snail withdraws into the shell.
Measurements
Length: 22 mm (1 in)
It is dark brown to olive in color, occasionally spotted and generally covered with fine striae or small ridges that extend around the whorls.
Rocksnails live in shoals, riffles and reefs or bedrock outcrops of medium to large rivers of eastern North America to the Rockies. Their habitats are generally subject to moderate currents during low flows and strong currents during high flows. The interrupted rocksnail lives attached to bedrock, boulders, cobbles and gravel.
Pleurocerid snails are considered generalist scrapers and generally feed by ingesting periphyton and biofilm detritus scraped off the substrate by the snailโs radula. In 2000, J.B.T. Morales and A.K. Ward described radula is a horny band with minute teeth that snails use to pull food into the mouth. Interrupted rocksnails have been observed grazing on silt-free gravel, cobble and boulders, as documented in 2004 by P.D. Johnson.
Interrupted rocksnails lay their adhesive eggs within the same habitat they occupy, as documented by P.D. Johnson in 2004. In a hatchery setting, mean clutch size for 2 year old interrupted rocksnails is around 8.83 (3 to 18 eggs per clutch), and clutch size of females greater than 3 years is 13.63 (2 to 21 eggs per clutch), as documented by Johnson in 2009.
The interrupted rocksnail was historically found in colonies on reefs and shoals of the Coosa River and several of its tributaries in Alabama and Georgia. It is currently found in the Oostanaula River.
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