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Leaunio umbrans (Lea, 1857)
Coosa Creekshell
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G1
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: Highest Conservation Concern
Element Occurrences (EOs) in Georgia: 43
Habitat Summary for element in Georgia: gravel and sand substrates in shoal and riffle habitats
The Coosa Creekshell has a moderately thin shell that is elliptical to irregularly oval, the posterior margin in females is bluntly pointed. The posterior ridge is low and rounded, with a steep posterior slope. Periostracum can range from a yellowish green to brown and usually has thin green rays on the posterior portion. Shell nacre in the umbo cavity is usually coppery purple (may be lighter on the margins), but occasionally white (Williams et al. 2008).
Villosa lienosa has a thicker shell and darker periostracum and the nacre may be purple, but is usually not coppery. Villosa nebulosa has more numerous rays that are wider and interrupted.
The Coosa Creekshell is typically found in medium rivers to small creeks and utilizes mixtures of sand, gravel, and cobble, and may be found in silt/clay mixtures. This mussel is typically in moderate current, and may be found on the margins of streams.
The diets of unionids are poorly understood but are believed to consist of algae and/or bacteria. Some studies suggest that diets may change throughout the life of a unionid with juveniles collecting organic materials from the substrate through pedal feeding and then developing the ability to filter feed during adulthood (Vaughn and Hakenkamp, 2001).
The Coosa Creekshell is a long term brooder and may be gravid from September to June of the following year (Williams et al. 2008).
Surveyors should consider sampling during periods when female individuals are spawning or brooding as this species may have higher detection rates during this period.
The Coosa Creekshell is endemic to the Coosa River drainage in Georgia, Alabama, and Tennessee.
Excess sedimentation due to inadequate riparian buffer zones, development, and agriculture covers suitable habitat and could potentially bury mussels. Poor agricultural practices may also cause eutrophication and degrade water quality. Industrial effluents as well as sewage treatment plant discharges also degrade water quality.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Pollution | Natural system modifications | Residential & commercial development |
| Specific Threat | Agricultural & forestry effluents | Dams & water management/use | None |
The Coosa Creekshell has been petitioned for federal listing.
Minimizing sediment and other runoff, stabilizing stream banks, and enhancing riparian buffers are important for reducing sedimentation and improving water quality.
Vaughn C.C. and C.C. Hakenkamp. 2001. The functional role of burrowing bivalves in freshwater ecosystems. Freshwater Biology 46: 1431-1446.
Williams, J.D., A.E. Bogan, and J.T. Garner. 2008. Freshwater mussels of Alabama and the Mobile Basin in Georgia, Mississippi, and Tennessee. The University of Alabama Press, Tuscaloosa.
A. Escobar
9 November 2021
