A Distributional Note of the Southernmost Population of Two Rocksnail Species (Gastropoda: Pleuroceridae) in the Lower Mississippi River

David S. Ruppel^1,*, A. Bailey Coomes¹, Nicky M. Faucheux¹, Steven G. George¹, Nathan L. Prine², Calvin R. Rezac², Ashley S. Ruppel³, and Matthew D. Wagner³

¹US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180. ²Mississippi Department of Wildlife, Fisheries, and Parks, Mississippi Museum of Natural Science, 2148 Riverside Drive, Jackson, MS 39202. ³US Fish and Wildlife Service, Mississippi Ecological Services Field Office, 6578 Dogwood View Parkway, Jackson, MS 39213. *Corresponding author.

Southeastern Naturalist, Volume 25, Issue 3 (2026): N64–N70

First published early online: 20 September 2026

Abstract
Understanding the distributional extent of freshwater gastropods is challenging because of limited information known about this group of organisms. Even more challenging is detecting gastropods in large river systems such as the Lower Mississippi River. In this note, we provide information on the southernmost population of Lithasia armigera (Armored Rocksnail) and Lithasia verrucosa (Varicose Rocksnail). These 2 species were first documented in the Mississippi River in 2012 and were detected as far south as Osceola, AR. However, this note documents a reproductive population of both rocksnails, 389 river kilometers downstream of their previously known southern limit.

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