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Amblema elliottii (I. Lea, 1857)
Coosa Fiveridge
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G3
State Rank: S2
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): No
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: Moderate Conservation Concern
Element Occurrences (EOs) in Georgia: 12
Habitat Summary for element in Georgia: Medium to large rivers; slow to strong current with sand, gravel, and cobble substrate.
Thick, somewhat inflated shell with a truncate or broadly rounded posterior margin. Shell has 3-5 well-developed ridges that become deeper with age. Periostracum (outer shell) is dark olive to black in adults, greenish brown in younger individuals (Williams et al. 2008).
Megalonias nervosa, the washboard, is also large-shelled mussel, however, has shallower ridges than A. elliotti. A. elliotti also lacks plications on the posterior ridge of the shell and has a shallower umbo cavity (Willdiams et al. 2008).
The Coosa Fiveridge can be found in large streams to large rivers, often in substrate composed of sand, gravel, and cobble.
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 Fiveridge is a short-term brooder, gravid during spring and summer. It’s glochidial hosts are unknown, however, its congener A. plicata is a host generalist (Williams et al 2008).
Surveyors should consider sampling during during spring and summer months when female individuals are spawning or brooding as this species may have higher detection rates during this period.
In Georgia, A. elliotti can be found in large streams and rivers within the Coosa River drainage. This species is endemic to the upper Mobile Basin.
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 effluent as well as sewage treatment plant discharges may also be degrading water quality.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Pollution | Pollution | Residential & commercial development |
| Specific Threat | Agricultural & forestry effluents | None | None |
The Coosa Fiveridge is a somewhat common species in the upper Coosa drainage.
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
August 2021
