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Home > Watchable Wildlife > Invertebrates > Mollusks > Aquatic Snails > Live-bearing Snails - Family Viviparidae
Common Name: Tulotoma
Description: One of largest and most distinct freshwater snails in North America. Shell globose (length may exceed 30 mm [1 1/8 in.]), whorls strongly concave with prominent shoulders, sutures impressed. Body whorl slightly to strongly convex. Shell sculpture consists of a row of large, evenly spaced nodules encircling shell whorls at midline. In some specimens, an additional row of reduced nodules present on ventral side of main body whorl below midline. Aperture ovate and obliquely angled, with ventral margin strongly recessed. Occasional specimens umbilicate. For a snail of its size, columellar lip narrow and completely white. Periostracum dark yellow to green or brown, with most individuals having dull brown bands. Shell often coated with dark layer of mineral depostis, making snail appear black in color. Nacre inside aperture white, with bands visible when present.
Distribution: Endemic to Mobile Basin. Historically found throughout much of Coosa and Alabama river systems. Known to be extant in: Coosa River below Jordan Dam, Elmore County; Kelly Creek, St. Clair County; Ohatchee and Cane creeks, Calhoun County; and Hatchet and Weogulfka creeks, Coosa County (Hershler et al. 1990).
Habitat: Flowing waters of large creeks and rivers. Remaining tributary populations generally restricted to lotic habitats in lower reaches, adjacent to Coosa River. Species does not occur in reservoir backwaters. Generally found beneath large flat rocks not in direct contact with river bottom, and having a large interstitial space beneath. Primary predator appears to be freshwater drum.
Life History and Ecology: Ovoviviparous with female's mantle cavity functioning as a marsupium for newly hatched juveniles. Once juveniles reach two to four millimeters (1/16 to 1/8 inch) in length, they crawl from mantle. Juveniles released from early spring to early fall. As with other viviparid snails, assumed that detritus is primary food source. However, likely also feeds on algae and bacteria attached to rocks. Often occurs in large clusters of individuals under large flat rocks, sometimes numbering in thousands under a single large boulder (one to two meters [3 1/4 to 6 1/2 feet] long). Likely that individuals live three to five years.
Basis for Status Classification: Limited distribution, declining population trend (outside of Jordan Dam tailwaters), and specialized habitat requirements make T. magnifica vulnerable to extinction. Eliminated from a majority of its habitat from construction and operation of hydroelectric dams on Coosa River. Poor land use practices, resulting in increased sedimentation were likely detrimental to tributary populations. Listed as endangered in Alabama (Stein 1976), but populations in Coosa River at Wetumpka have recovered due to restoration of minimum flow downstream of Jordan Dam. Listed as endangered by the U.S. Fish and Wildlife Service in 1991, Tulotoma was downlisted to threatened in June of 2011.
above from Alabama Wildlife (2004), prepared by: Paul D. Johnson, Volume 2 and updated