Common Name: Plicate Rocksnail
Scientific Name: Leptoxis plicata (Conrad)
Other Names: Pleated Round Riversnail, Smith"s Round Riversnail
Size: 20 mm [3/4 in.]
Description: Shell moderately thick (max. length = 20 mm [3/4 in.]) and subglobose in outline. Whorls strongly convex and shouldered, with a raised ridge on shoulder. Small, regularly spaced plicae set on ridge of most specimens. Periostracum generally dark yellowish green, with up to three dark bands, but generally becomes darker with age and bands become obscure. Columella mostly white, but may have light brown area on lower edge. Columellar lip reflected to completely cover umbilicus. Aperture ovate in shape and most commonly bluish white to pink, with no internal banding. Operculum dark red and moderately thick, with curved left margin and straight right margin. Juveniles same general shape, have tightly coiled whorls, and often display a weak carina on mid-whorl. Banding pattern dominates juvenile coloring, making them appear nearly all black. (Modified from Goodrich 1922)
Distribution: Endemic to Black Warrior River system, historically, occurring from headwaters to near confluence with Tombigbee River, Greene County. Now restricted to 15 shoals in a 30-kilometer (18.6-mile) reach of Locust Fork, Jefferson County, between Kimberly and Sayre (Johnson 2002).
Habitat: Occurs in shoals, on silt-free bedrock, cobble, and boulders, in less than one meter (3 1/4 feet) of water. Often found on undersides of large, flat boulders (Johnson 2002). Grazes on exposed rock surfaces. More commonly found marginally than at mid-channel..
Life History and Ecology: Females deposit eggs late February through late April. Eggs laid on river bottom in shallow water (less than 50 centimeters [20 inches] deep) with exposure to direct current (P. D. Johnson, unpubl. data). Eggs laid simply and not in well-formed clutches. Juveniles grow rapidly and can reach 10 millimeters (3/8 inch) their first year. Have survived four years in captivity (P. D. Johnson, unpubl. data).
Basis for Status Classification: Vulnerable to extinction due to limited distribution, decreasing population trend, and specific habitat requirements. Tombigbee-Black Warrior Waterway Project destroyed over half of available riverine habitat within its distribution. Poor water quality apparently caused extirpation from Mulberry Fork. Has disappeared from upper Locust Fork since late 1980s, but causes of decline are uncertain, possible including sedimentation, organic pollution, and hydrologic disruption. Eliminated from over 90 percent of distribution. Populations appear to be declining at over half of 15 shoals where extant (Johnson 2002). Listed as endangered in Alabama (Stein 1976). However, it responds well to captive propagation, and recovery efforts under Mobile Basin Recover Plan (USFWS 2000) are currently ongoing. Listed as endangered by the U.S. Fish and Wildlife Service in 1998.
above from Alabama Wildlife, Volume 2 (2004), prepared by: Paul D. Johnson
September 25, 2012, AABC staff and Jeff Garner released 4,002 Leptoxis plicata into the reintroduction site of the Locust Fork. Jeff found additional young of the year snails as he completed the 2012 release. Although there have been water quality problems at the site, this population has continued recruiting for 2-years, so the stocking efforts will discontinue at this site.
The Locust Fork received 1,281 juvenile and one-year-old Plicate Rocksnails from the Alabama Aquatic Biodiversity Center on October 3, 2011.