Villosa umbrans

Villosa umbrans (I. Lea 1857)
Coosa Creekshell

Villosa umbrans, 5.26 cm shell length
Choccolocco Creek, Calhoun County, Alabama

Diagnosis

There has been considerable confusion surrounding the status of this species from its very inception.  Villosa umbrans was originally mis-named Villosa vanuxemensis in honor of a friend of Issac Lea (Hurd 1974).  More recently (i.e., in Turgeon et al. 1998 and Parmalee and Bogan 1998), 2 subspecies of Villosa vanuxemensis were recognized, Villosa vanuxemensis vanuxemensis in the headwaters of the Tennessee and Villosa vanuxemensis umbrans in the headwaters of the Coosa River.  However, phylogenetic analyses suggest that the 2 are distinct species (W. Haag, USFS pers. com.).
   
Villosa umbrans can be difficult to discern from Villosa lienosa but V. lienosa is rare in the Coosa Drainage.  Both are small, dimorphic, and have a light brown to black periostracum.  The nacre color is variable but is usually salmon or orange in V. umbrans and purple or white in V. lienosa.  The posterior shell margin in V. umbrans is sometimes accompanied by a slight protrusion, especially in females and the shell may often appear 'pinched'.

Ecology

Villosa umbrans is locally common in small to mid-sized streams in the headwaters of the Coosa Drainage.  Recent surveys in the Coosa River Drainage of Alabama found V. umbrans primarily in sand and gravel substrate near stream margins and at low flows (Gangloff 2003).  Villosa umbrans in Alabama are gravid from late fall through early spring; although some individuals collected from headwater streams showed evidence of reproductive activity (e.g., swollen marsupia, distended branchial papillae) through early July.  Fish hosts for Villosa umbrans are unknown but likely include bass and sunfish.

Distribution

Villosa umbrans is endemic to the Coosa Drainage in Alabama, Georgia, and Tennessee.  Extant populations appear restricted to isolated headwater systems (Evans 2001, Gangloff 2003).  

Status

In the Upper Alabama River Drainage of Alabama, the range of V. umbrans has declined moderately but populations remain at 20 or more sites in at least 8 sub-basins in Alabama (Gangloff 2003).  In the Conasauga River Drainage, V. umbrans is sporadically distributed but may be locally abundant (Evans 2001).  Villosa umbrans is not presently protected by any state or federal agencies although it may warrant consideration based on its restricted distribution and presence in isolated, headwater streams.  Based on its highly restricted endemic range, Williams et al. (1993) considered V. umbrans a species of special concern.

References

Evans, R. D.  2001.  Historical and contemporary distributions of aquatic mollusks in the Upper Conasauga 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.

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.

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

Turgeon, D. D., J. F. Quinn, A. E. Bogan, E. V. Coan, F. G. Hochenberg, W. G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams.  1998.  Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks, second edition.  American Fisheries Society, Special Publication 26 Bethesda, Maryland.

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.