Flat pebblesnail (Lepyrium showalteri)

Flat pebblesnail specimens
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Flat pebblesnail fact file

Flat pebblesnail description

GenusLepyrium (1)

Despite the tiny size of this freshwater snail, the flat pebblesnail can be distinguished from other species in the Hydrobiidae family by its relatively large shell. It has two or three coils to its shell and the shell coils are, as its name indicates, flattened and oval in shape. This species can also be identified by the lack of a hole or depression in the centre of the shell and the lack of a distinct point to the shell (2). Snails in the Hydrobiidae family rarely have any colour to the shell and are often white (3).

Height: 3.4 - 4.4 mm (2)
Width: 4 - 5 mm (2)

Flat pebblesnail biology

Little is known about the biology of the flat pebblesnail, but, like other species in this family of freshwater gastropods (the Hydrobiidae), it is likely to feed on detritus and films of bacteria and algae found on the rocks in rivers (5).

The flat pebblesnail lays eggs in capsules, which are attached to hard surfaces within the river (4). After hatching, the juvenile snail, which measures 0.25 millimetres, starts grazing immediately (6). The life-cycle of this species appears to be completed in one year (4).


Flat pebblesnail range

The flat pebblesnail is found only in central Alabama, USA.  It is currently found at only two sites, in the Cahaba River in Shelby county and the Little Cahaba in Bibb County (2) (4). Historically, it had a larger distribution within these two rivers, as well as being found in the Coosa River (4).


Flat pebblesnail habitat

This small freshwater snail inhabits rivers, where it is typically found attached to clean, smooth stones in areas of rapid currents (4).


Flat pebblesnail status

Classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable


Flat pebblesnail threats

The historical range of the flat pebblesnail has decreased by 90 percent as a result of numerous threats, largely created by human activity. Mining and dredging are two of the primary causes of flat pebblesnail’s decline, destroying and polluting the freshwater habitats on which this species so desperately relies. The creation of dams is another significant factor; in 1993 and 1996 studies failed to find a single flat pebblesnail in one Coosa River portion after two dams were developed upstream (4).


Flat pebblesnail conservation

The US Fish and Wildlife Service lists the flat pebblesnail as Endangered and thus a major recovery plan was initiated in 2005 with the aim of re-classifying the species from Endangered to Threatened by 2015. As a result of the plan, the flat pebblesnail was bred in captivity and some of these captive-bred individuals have already been reintroduced into the species’ natural habitat (4). Other measures outlined in the recovery plan include protecting suitable habitat, developing public education programs and conducting further research on the flat pebblesnail (4). Implementing such conservation efforts, combined with close monitoring of the species’ progress, should hopefully avert further declines of this species.


Find out more

For more information on conservation in Alabama see:



Authenticated (15/09/10) by Paul Hartfield, Endangered Species Biologist, U.S. Fish and Wildlife Service,
http://www.fws.gov/mississippiES and Dr Paul Johnson,Program Supervisor, Alabama Aquatic Biodiversity Center,

This species information was authored as part of the Arkive and Universities Scheme.


Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
Litter formed from fragments of dead material.
A group of molluscs that have a well-defined head, an unsegmented body and a broad, flat foot. They can possess a single, usually coiled shell or no shell at all. Includes slugs, snails and limpets.
Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.


  1. IUCN Red List (March, 2010)
  2. NatureServe (November, 2009) 
  3. Hershler, R. and Ponder, W.F. (1998) A Review of Morphological Characters of Hydrobioid Snails. Smithsonian Institute, Washington.
  4. U.S. Fish and Wildlife Service. (2005) Recovery Plan for Six Mobile River Basin Aquatic Snails. US Fish and Wildlife Service, Jackson, Mississippi.
  5. Clark, S. (2004) Hydrobiidae. In: Perez, K.E., Clark, S.A. and Lydeard, C. (Eds.) Showing Your Shells: A Primer to Freshwater Gastropod Identification. Freshwater Mollusk Conservation Society, Tuscaloosa, Alabama. 
  6. Johnson, P. (2010) Pers. comm.

Image credit

Flat pebblesnail specimens  
Flat pebblesnail specimens

© Alabama Department of Conservation and Natural Resources

Paul D. Johnson
Alabama Aquatic Biodiversity Center
Tel: (334) 683-5000
Fax: (334) 683-5082


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