Carolina Heelsplitter

Lasmigona decorata

Description

The Carolina heelsplitter has an ovate, trapezoid-shaped, unsculptured shell. The shell of the largest specimen ever collected measured 4.6 in (118 mm) in length, 1.6 in (40 mm) in width, and 2.5 in (63.5 mm) in height. The shell's outer surface varies from greenish-brown to dark brown in color, and shells from younger specimens have faint greenish-brown or black rays. The nacre (inside surface) is often pearly-white to bluish white, grading to orange in the area of the umbo (knob at the hinge). However, in older specimens the entire nacre may be a mottled pale orange.

Behavior

Reproductive characteristics for this species are probably similar to other freshwater mussels. Males release sperm into the water column. Females then take in the sperm through their siphons during feeding and respiration. The fertilized eggs are retained in the gills until the larvae fully develop. Gravid females have been observed during mid-May. Glochidia (larvae) attach themselves to the gills or fins of their fish hosts following their release from the females' gills. Fish host species are unknown.

Habitat

The Carolina heelsplitter has been recorded from small to large streams and rivers, as well as ponds. The ponds referred to in historic records are believed to have been mill ponds on some of the smaller streams. The species is now known to occur in only three small streams and one small river and is usually found in mud, muddy sand, or muddy gravel substrates along stable, well-shaped stream banks. The stability of the streambanks appears to be very important to this species.

Distribution

The historical distribution of this species included the Catawba River, Mecklenburg County, North Carolina; several streams and ponds in the Catawba River system around the Charlotte areas of Mecklenburg County, North Carolina; one small stream in the Pee Dee River system in Cabarrus County, North Carolina; and an area in South Carolina referred to as the Abbeville District (possibly the Saluda River system). An additional record in the Oconee River in Georgia is believed to be a misidentification.

Between 1987 and 1990, surveys funded by the U.S. Fish and Wildlife Service were conducted. A total of 687 sites in 356 different streams, rivers, and impoundments within the historic range and potential habitat of the Carolina heelsplitter were surveyed including the Saluda, Catawba, Pee Dee, Broad, Rocky, and Lynches River systems. Only three populations were located: one in a Catawba River tributary in Union County, North Carolina; the second in a tributary of the Rocky River (Pee Dee River system), Union County, North Carolina; and the third in the Lynches River drainage (Pee Dee River system) in Chesterfield, Lancaster, and Kershaw Counties, South Carolina (this was the largest population).

Threats

Habitat loss/degradation and increases in water pollution caused by impoundments, stream channelization, dredging, sand mining, sewage effluents, and poorly implemented agricultural, forestry, and commercial/residential development practices are believed to be the primary factors leading to the decline and extirpation of this species from large sections of its historic range.

All three known populations are bordered by private lands except for small sections of road rights-of-ways and a state bridge.

The Lynches River sites receive heavy nutrient and pollutant loads from wastewater treatment plants and other point and nonpoint sources.

In some areas, vegetation has been cleared right up to the stream banks which increases the siltation of the streams, eliminates shading, and destabilizes the streambanks (a key habitat component for this species).

Conservation and Recovery

Actions needed to protect the Carolina heelsplitter include: (1) pursuing legal protection for the species and its habitat; (2) conducting population and habitat surveys to determine the status and range of the species, if feasible; (3) testing the potential for reintroducing the species into its historic range; and (4) determining life history and ecological requirements for Lasmigona decorata.

Population sizes may be too low to allow intensive research and population manipulation.

Contacts

U.S. Fish and Wildlife Service
Regional Office of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

Asheville Ecological Services Field Office
160 Zillicoa St.
Asheville, North Carolina 28801-1082
Telephone: (828) 258-3939
Fax: (828) 258-5330

References

Thorp, J. H., and A. P. Covich. 1991. Ecology and Classification of North American Freshwater Invertebrates. Academic Press, San Diego. 911 pp.

U.S. Fish and Wildlife Service. 1993. "Endangered and Threatened Wildlife and Plants; Lasmigona decorata (Carolina Heelsplitter) Determined to be Endangered." Federal Register 58(124): 34926-34931.