Carolina heelsplitter (Lasmigona decorata)
Federal Status: Endangered, June 30, 1993
Description: The Carolina heelsplitter was first described in 1852. It has an ovate, trapezoid-shaped shell. The outer surface of the shell 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 deepest part of the shell. However, in older specimens the entire nacre may be a mottled pale orange. The shell of the largest known specimen of the species measures 4.6 inches (xxx centimeters) in length. Like other freshwater mussels, the Carolina heelsplitter feeds by siphoning and filtering food particles from the water column.
The reproductive cycle of the species is similar to other native mussels. Males release sperm into the water, and the eggs are fertilized when the sperm are taken in by the females through their siphons during feeding and respiration. Females retain the fertilized eggs in their gills until the larvae (glochidia) fully develop. The glochidia are released into the water and must attach to the gills or fins of the appropriate fish species. They remain attached to their fish host for several weeks, drawing nourishment from the fish while they develop into juvenile mussels. They do not hurt their fish host. The juvenile mussels then detach from the fish host and drop to the bottom of the stream where they continue to develop, provided they land in a suitable place with good water conditions. This dependence on a certain species of fish increases the mussels’ vulnerability to habitat disturbances. If the fish host is driven off or eliminated because of habitat or water quality problems, the mussels can’t reproduce and will eventually die out.
Habitat: The Carolina heelsplitter requires cool, clean, well-oxygenated water. Stable, silt-free stream bottoms appear to be critical to the species. Typically stable areas occur where the stream banks are well-vegetated with trees and shrubs.
Distribution: Historically the Carolina heelsplitter occurred in several locations within the Catawba and Pee Dee River systems in North Carolina and the Catawba, Pee Dee, Saluda, and Savannah River systems in South Carolina. Today, only ten populations are known to survive. The species still occurs in two small streams in North Carolina – one in the Catawba River system and one in the Pee Dee River systems. In South Carolina, the Carolina heelsplitter remains in the Pee Dee, Catawba, and the Savannah River systems. Finally, one population exists on the North Carolina/South Carolina state line, in the Catawba River System.
Threats: Poor water quality and habitat conditions have led to the decline and loss of populations of the Carolina heelsplitter and threaten the remaining populations. Studies have shown that freshwater mussels, especially in their early life stages, are extremely sensitive to many of the pollutants (chlorine, ammonia, heavy metals, etc.) commonly found in municipal and industrial wastewater releases. Impoundments (dams), channelization projects, and in-stream dredging operations directly eliminate habitat. These activities also alter the quality and stability of remaining stream reaches by affecting the water flow, temperature, and chemistry. Agriculture (both crop and livestock) and forestry operations, roads, residential areas, golf courses, and other construction activities that do not adequately control soil erosion and water run-off contribute excessive amounts of silt, pesticides, fertilizers, heavy metals, and other pollutants that suffocate and poison freshwater mussels. The alteration of floodplains or the removal of forested stream buffers can be especially detrimental. Flood plains and forested stream buffers help maintain water quality and stream stability by absorbing, filtering, and slowly releasing rainwater. This also helps recharge groundwater levels and maintain flows during dry months.
Critical Habita: Critical Habitat for the Carolina heelsplitter was designated on September 2, 2002. For specific information on areas designated as Critical Habitat and the primary constituent elements defined for this species, please refer to the Federal Register notice (67 FR 44501 - 44522).
References:LeGrand, Jr., H.E., J.T. Finnegan, S.E. McRae, S.P. Hall. 2010. Natural Heritage Program List of the Rare Animal Species of North Carolina. N.C. Natural Heritage Program, Raleigh, NC.
- U.S. Fish and Wildlife Service Environmental Conservation Online System
- Carolina heelsplitter Recovery Plan
John Fridell, Fish and Wildlife Biologist, 828-258-3939 ext. 225
Species profile revised on October 4, 2011.