Thursday 25 October 2012

'Extinct' Gastropod rediscovered in Alabama.

The Mobile River Basin in Alabama and Georgia is considered to contain the most diverse Mollusc faunas of the entire North American continent. Unfortunately the area is also heavily urbanized and industrialized, with waterways channelized to allow shipping, blocked by hydroelectric projects and polluted by urban and mine runoff, leading to a large number of species being believed to be extinct; at last count 47 endemic Molluscs, including 37 Gastropods, were thought to have died out in the Basin.

In a paper published in the journal PLoS One on 8 August 2012, Nathan Whelan of the Department of Biological Sciences at the University of Alabama, Paul Johnson of the Alabama Aquatic Biodiversity Center at the Alabama Department of Conservation and Natural Resources, and Phil Harris also of the Department of Biological Sciences at the University of Alabama describe the rediscovery of Leptoxis compacta, an aquatic Snail endemic to the Cahaba River, which has not been alive for over 70 years, and which was declared extinct in 2000.

A specimen of Leptoxis compacta from the Cahaba River. Whelan et al. (2012).

The species was found at a single site on the Cahaba River, above the junction with Shades Creek, and established as being Leptoxis compacta by comparison with museum specimens. The site is considered highly vulnerable by Whelan et al., and believe the species should be classified as critically endangered under International Union for the Conservation of Nature criteria, and that the U.S. Fish and Wildlife Service should consider L. compacta for protection under the U.S. Endangered Species Act because of its highly restricted range and susceptibility to a single pollution or siltation event. They also suggest that, since the Snail proved willing to breed in captivity, it could be re-introduced to other parts of its former range.

Map showing known historical sites of Leptoxis compacta colonies and the site of the rediscovered colony. Whelan et al. (2012).

(A) Museum specimen of Leptoxis compacta. (B-F) Newly recovered specimens showing a growth series. Whelan et al. (2012).

Museum specimens of other species of Leptoxis and the related genera Elimia and Pleurocera used for comparison in the study. (A) L. ampla (B) E. ampla (C) E. annetae (D) E. cahawbensis (E) E. clara (F) E. showalteri (G) E. variata (F) P. prasinatum. Whelan et al. (2012).

(Top) The radula ('tongue') of a Leptoxis compacta specimen collected in 1881. (Bottom) The radula of a specimen collected in 2011. Whelan et al. (2012).

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