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Lasmigona etowaensis (Conrad, 1849)
Etowah Heelsplitter
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: High Conservation Concern
Element Occurrences (EOs) in Georgia: 47
Habitat Summary for element in Georgia: Small to medium creeks, often in very small streams where no other mussels occur. Some current, mainly sandy substrates but occasionaly in mud or gravel. May be associated wit
The Etowah Heelsplitter has a thin, elliptical shell, with a truncate posterior margin and a rounded anterior margin. The posterior ridge is broadly rounded (and may be slightly doubled), with a moderately steep slope. The umbo barely raises over the hinge line and the dorsal margin is convex, while the ventral margin is straight to slightly convex. The periostracum is tawny to greenish brown in color, becoming a darker brown with age. Usually there are no rays. Nacre is usually bluish white, but may have a pale salmon tint in the umbo cavity. Psuedocardinal teeth are low and compressed (2 in left valve, 1 in right valve) and the lateral teeth are rudimentary. There is a small, compressed interdental projection, which may join with the posterior pseudocardinal tooth. (Adapted from Williams et al, 2008).
Lasmigona etowaensis may resemble Villosa lienosa, V. umbrans, and V. nebulosa; however, the Villosa species will have well-developed lateral teeth and lack the inter-dental projection in the left valve. Additionally, V. nebulosa usually has rays on the periostracum, and V. lienosa and V. umbrans usually have purple nacre, in contrast to the white nacre of L. etowaensis.
Lasmigona etowaensis typically occupies small to medium creeks, and can often occur in very small streams that are not occupied by any other mussel species.
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).
This species is a long term brooder, and can be gravid from late summer or fall into the following summer. A number of fish have been found to serve as suitable glochidial hosts, including the Rock Bass, Bluegill (Lepomis macrochirus), the redeye bass (Micropterus coosae), sculpin (family Cottidae), and members of the minnow and darter groups (Williams et al 2008).
Surveyors should look in medium to small streams, including headwater streams.
Lasmigona etowaensis is found above the fall line in the Coosa Basin of Georgia, Alabama, and Tennessee, and the Cahaba and Black Warrior drainages in Alabama.
Excess sedimentation due to inadequate riparian buffer zones, development, and agriculture covers suitable substrate, and could potentially bury mussels. Poor agricultural practices may also cause eutrophication and degrade 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 Etowah heelsplitter not an uncommon species, however, its distribution is not fully known as survey data for headwater streams is lacking.
Maintenance and restoration of riparian buffers along headwater streams will prevent excessive erosion, sedimentation, and runoff into streams, and will help water temperatures from becoming too warm.
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.
Anakela Escobar
8 November 2021