Plicate Rocksnail

Leptoxis plicata

Description

The Leptoxis plicata, (plicate rocksnail) grows to about 0.8 in (2 cm) in length. Shells are spherical with broadly rounded apertures. The body whorl may be ornamented with strong folds or plicae. Shell color is usually brown, occasionally green, and often with four equidistant color bands. The central column is smooth, rounded, and typically pigmented in the upper half. The aperture is usually bluish-white, occasionally pink or white. The operculum (plate that closes the shell when the snail is retracted) is dark red, and moderately thick. Although morphologically similar to the Basin's other three surviving rocksnail species, the plicate rock-snail is genetically distinct.

Behavior

The plicate rocksnail is known to graze on algae found on rocks. In addition, the plicate rocksnail lays its eggs on rocks in order to reproduce.

Habitat

Rocksnails are gill breathing snails found attached to cobble, gravel, or other hard substrates in the strong currents of riffles and shoals. Adult rock-snails move very little, and females probably glue their eggs to stones in the same habitat. The related Tennessee River rocksnail has a lifespan reported to be two years. Longevity in the painted and the basin's other rocksnails is unknown.

Distribution

The plicate rocksnail historically occurred in the Black Warrior River and its tributary, the Little Warrior River, and the Tombigbee River. Status survey efforts in 1991 found populations of plicate rock-snails only in an approximately 55 mi (88 km) reach of the Locust Fork of the Black Warrior River, Jefferson and Blount Counties, Alabama. Surveys during 1996 and 1997 indicate that the snail has recently disappeared from the upstream two-third portion of that habitat and now appears restricted to an approximately 20 mi (32 km) reach in Jefferson County.

Threats

The plicate rocksnail has lost more than 90% of its historical range because of habitat destruction caused by impoundment, and pollution by siltation and chemicals associated with coal mining and land-use practices. A site on the Locust Fork River is being considered for the construction of a water supply impoundment. Plicate rocksnails occurred in riffle and shoal habitats above and below the reservoir site in 1994. In 1996, plicate rocksnails could not be relocated in the portion of the river to be flooded by the reservoir; however, their continued survival was confirmed in an approximately 20 mi (32 km) stretch of river below the potential dam site, which would be subject to impacts from construction activities and post-construction changes in water quality.

Conservation and Recovery

The plicate rocksnail only survives in three small, isolated, critical habitats. Surveys during 1996 and 1997 found that the snail only persists in a reach of about 20 mi (32 km) of the Locust Fork of the Black Warrior River, Alabama. It is crucial that its few critical habitats are protected from any proposed impoundment, and from pollution associated with coal mining, agricultural land-use, or other sources. The surviving populations of the plicate rocksnail should be monitored, and research undertaken into its biology and ecological needs, including work on its propagation. If suitable habitat can be found, additional populations should be established.

Contacts

U. S. Fish and Wildlife Service
Jackson Ecological Services Field Office
6578 Dogwood View Parkway, Suite A
Jackson, Mississippi 39213-7856
Telephone: (601) 965-4900

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

Reference

U.S. Fish and Wildlife Service. 28 October 1998. "Endangered and Threatened Wildlife and Plants; Endangered Status for Three Aquatic Snails, and Threatened Status for Three Aquatic Snails in the Mobile River Basin of Alabama." Federal Register 63(208):57610-57620.