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Cambarunio nebulosus (Conrad, 1834)
Alabama Rainbow
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): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: High Conservation Concern
Element Occurrences (EOs) in Georgia: 18
Habitat Summary for element in Georgia: Large rivers to small streams; flowing water with gravel and sand substrates, may be found in fine sediments among cobble and boulders
The Alabama Rainbow has a moderately thin shell with an elliptical outline that is slightly truncate or blunt on the posterior end. Truncation can be slightly stronger and higher up on the shell in females. The posterior ridge is rounded, while the umbo is slightly elevated over the hinge line and is not inflated. The periostracum is yellow to yellow-green with numerous interrupted green rays that are typically concentrated on the posterior half of the shell. Pseudocardinal teeth are small and compressed and there may be a small accessory denticle anteriorly on the right valve. The lateral teeth are moderately long and the interdentum is short and narrow. The umbo cavity is typically white (Williams et al, 2008).
Villosa umbrans typically has fewer, narrower uninterrupted green rays concentrated on the posterior end and the umbo cavity is usually a coppery purple. Villosa vibex has large, uninterrupted rays and the periostracum is usually more yellowish.
The Alabama Rainbow can be found in flowing water from large rivers to small streams, and is often found in pockets of gravel, sand, or fine substrate (but may be in mixes of cobble-gravel).
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 Alabama Rainbow is a long term brooder and is gravid from late summer or fall to the following summer. Gravid females have a papillate mantle fold and typically displays at night.
Surveyors should consider sampling during late spring/early summer or late fall when female individuals are spawning or brooding as this species may have higher detection rates during this period. Investigators should conduct visual and tactile searches of sand, gravel, and cobble substrates along the margins of the river and in areas to moderate flows.
The Alabama Rainbow is endemic to the Mobile Basin above the fall line, excluding the Tallapoosa River system. In Georgia, it can be found in the Coosa, Conasauga, upper Coosawattee, Etowah, and Oostanaula rivers and their tributaries.
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 | Agriculture & aquaculture | Natural system modifications | Residential & commercial development |
| Specific Threat | None | Dams & water management/use | None |
The Alabama Rainbow has no state or federal protections. It has been petitioned for listing under the Endangered Species Act.
Riparian buffers should be enhanced and conserved and agricultural and water treatment best management practices should be implemented.
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, AL.
Anakela Escobar
8 November 2021
