Lasmigona holstonia

Lasmigona holstonia (Say 1831)
Tennessee Heelsplitter

 Lasmigona holstonia 4.16 cm shell length
Cane Creek, LaFayette County, GA

Diagnosis

Lasmigona holstonia is a small, cryptic species that is easily confused with other Mobile and Tennessee drainage headwater mussels, especially Strophitus connasaugaensis.  L. holstonia has more pronounced pseudocardinal teeth and beaks that protrude above the hinge line, whereas Strophitus typically shows neither of these characteristics (Clarke 1985).  Periostracum in L. holstonia is generally brown or dark yellow and rays are usually absent.  L. holstonia is not sexually dimorphic.  Clarke (1985) described glochidia of L. holstonia as ovate, hooked, and heavily pitted. 

Ecology

Lasmigona holstonia is often found in headwater streams and springs, and may be the only species present in 1st or 2nd order creeks (Hurd 1974, Clarke 1985).  Clarke (1985) noted that L. holstonia collected in late summer were gravid with immature glochidia and inferred that this species is a long term brooder with glochidia released the following spring.  Host fish of L. holstonia are unknown.  In the South Fork of Terrapin Creek, L. holstonia was found at high densities (> 100 mussels per 50 m stream) in clay banks and stable sand along stream margins (Gangloff 2003). 

Distribution

L. holstonia was historically found throughout the Upper Alabama Drainage in Alabama, Georgia and Tennessee and in the headwaters of the Tennessee River Drainage in Tennessee, Georgia, North Carolina and Virginia (Parmalee and Bogan 1998).  This disjunct distribution has been used as evidence to infer a stream capture mediated faunal exchange between the Upper Coosa and Tennessee drainages (e.g., Ortmann 1923, van der Schalie 1938, Hurd 1974).

In Alabama, Mobile Basin populations of L. holstonia are restricted to the South Fork of Terrapin Creek in the Upper Coosa Drainage and Spring Creek (Cherokee Co, Gangloff 2003, J. T. Garner ALDCNR pers. com.).  L. holstonia populations in the South Fork of Terrapin Creek appear stable; juvenile mussels were frequently found by recent surveys (Gangloff 2003).  Recent surveys in the Connasauga and Etowah drainages indicate that L. holstonia is still widespread in Mobile Basin headwater streams in Georgia and Tennessee (Evans 2001).

Status

L. holstonia appears to have been extirpated from much of the Mobile Basin in Alabama (Gangloff 2003).  The status of L. holstonia in the Alabama portions of the Tennessee drainage is unknown.  Hurd (1974) found no populations of L. holstonia in Alabama.  Because of this species' restricted range it is considered an endangered species by the State of Alabama (Harris 1990).  Both the USFWS and Williams et al. (1993) recognize L. holstonia as a species of concern. 

References

Clarke, A. H.  1985.  The tribe Alasmidontini (Unionidae: Anodontinae), Part II: Lasmigona and Simpsonaias.  Smithsonian Contributions to Zoology 399: 1-75.

Evans, R. D.  2001.  Historical and contemporary distributions of aquatic mollusks in the Upper Connasauga River system of Georgia and Tennessee.  M.S. Thesis, University of Tennessee Chattanooga, 277 p.

Gangloff, M. M.  2003.   The status, physical habitat associations, and parasites of freshwater mussels in the upper Alabama River Drainage, Alabama.  Ph.D. Dissertation, Auburn University.

Harris, S. C.  1990.  Preliminary considerations on rare and endangered invertebrates in Alabama.  Journal of the Alabama Academy of Science 61:64-92.

Hurd, J. C.  1974.  Systematics and zoogeography of the unionacean mollusks of the Coosa RIver Drainage of Alabama, Georgia and Tennessee.  Ph.D. Dissertation, Auburn University, 240 p.

Ortmann, A. E.  1923.  The anatomy and taxonomy of certain Unioninae and Anodontinae form the Gulf Drainage.  The Nautilus 26:73-144.

Parmalee, P. W. and A. E. Bogan.  1998.  The freshwater mussels of Tennessee, University of Tennessee Press, Knoxville. 328 p.

van der Schalie, H. 1938.  The naiades (fresh-water mussels) of the Cahaba River in Northern Alabama.  Occasional Papers of the Museum of Zoology - University of Michigan 392:1-29.

Williams, J. D.,  M. L. Warren, K. S. Cummings, J. L Harris, and R. J. Neves.  1993.  Conservation status of freshwater mussels of the United States and Canada.  Fisheries 18: 6-22.