Carolina
Heelsplitter in North Carolina
CAROLINA HEELSPLITTER
Lasmigona decorata
FAMILY: Unionidae
STATUS: Endangered, Federal Register, June 30, 1993
DESCRIPTION:
The Carolina heelsplitter was originally described as Unio decoratus by
Lea (1852). In 1970, this species was synonymized with Lasmigona subviridis
(Conrad 1835) by Johnson (1970). Clarke (1985) recognized the Carolina
heelsplitter as a distinct species, Lasmigona decorata, and synonymized
Unio charlottensis (Lea 1863) and Unio insolidus (Lea 1872)
with Lasmigona decorata.
The Carolina heelsplitter has an ovate, trapezoid-shaped, unsculptured shell. The shell of the largest known specimen of the species measures 114.8 millimeters (mm [4.6 inches]) in length, 39.0 mm (1.56 inches) in width, and 68.0 mm (2.7 inches) in height (Keferl 1991). 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 (Keferl 1991). However, in older specimens the entire nacre may be a mottled pale orange (Keferl 1991).
RANGE:
The Carolina heelsplitter currently has a very fragmented, relict distribution
but historically was known from several locations within the Catawba and Pee Dee
River systems in North Carolina and the Pee Dee and Savannah River systems, and
possibly the Saluda River system, in South Carolina. Historically, the species
was collected from the Catawba River, Mecklenburg County, North Carolina;
several streams and ponds in the Catawba River system around the Charlotte area
of Mecklenburg County, North Carolina; one small stream in the Pee Dee River
system in Cabarrus County, North Carolina; one pond in the Pee Dee River system
in Union County, North Carolina; and an area in South Carolina referred to only
as the Abbeville District, a terminology no longer employed (Clarke 1985, Keferl
and Shelly 1988, Keferl 1991). The records from the Abbeville District, South
Carolina, were previously believed to have been from the Saluda River system
(Clarke 1985, Keferl and Shelly 1988, Keferl 1991). However, as a result of
surveys funded by the U.S. Forest Service and the South Carolina Department of
Natural Resources, a population of the Carolina heelsplitter was discovered in
the spring of 1995 in the Savannah River system (Stevens Creek watershed)
(Alderman 1995 and 1998). Therefore, the historic records from the Abbeville
District may have been from either the Saluda River system or the Savannah River
system or both.
Recent collection records (Keferl and Shelly 1988, Keferl 1991, Alderman 1995 and 1998) indicate that the Carolina heelsplitter has been eliminated from all but one of the streams from which it was known to have been originally collected. Only six populations of the species are presently known to exist. In North Carolina one small remnant population occurs in the Catawba River system in Waxhaw Creek, a tributary to the Catawba River, in Union County, North Carolina, and another small population occurs in a short stretch of Goose Creek, a tributary to the Rocky River in the Pee Dee River system, in Union County, North Carolina. In South Carolina, there are four surviving populations - one each in the Pee Dee and Catawba River systems and two in Savannah River system (Alderman 1998). The population in the Pee Dee River system occurs in a relatively short reach of the Lynches River in Chesterfield, Lancaster, and Kershaw Counties and extends into Flat Creek, a tributary to the Lynches River in Lancaster County (Keferl 1991). In the Catawba River system, South Carolina the species still survives only in a short reach of Gills Creek in Lancaster County (Alderman 1998). In the Savannah River system, one population is found in Turkey Creek and two of its tributaries, Mountain Creek and Beaverdam Creek, in Edgefield County, South Carolina; and, another smaller population still survives in Cuffytown Creek, in Greenwood County, South Carolina (Alderman 1998). No evidence of a surviving population has been found in recent years in the Saluda River system (Keferl 1991, Alderman 1998).
The species has been reduced to a few short reaches of each of these streams, primarily as a result of impoundments and channelization projects and the general deterioration of water quality resulting from siltation and other pollutants contributed as a result of poor land use practices.
HABITAT:
Historically, the species was reported 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 within the species' historic
range (Keferl 1991). Presently, the species is known to occur in only six small
streams and one small river and is usually found in mud, muddy sand, or muddy
gravel substrates along stable, well-shaded stream banks (Keferl and Shelly
1988, Keferl 1991). However, in Mountain Creek in Edgefleld County, South
Carolina, two live individuals were found near the center of the stream channel
in a relatively silt-free substrate comprised primarily of a mixture of sand,
gravel, and cobble (personal observation, 1995). It is conceivable that this is
the preferred habitat type for the species and that in other areas degradation
of the gravelly substrates has restricted the species to less suitable habitats.
The stability of stream banks appears to be very important to the species
(Keferl 1991).
Like other freshwater mussels, the Carolina heelsplitter feeds by filtering food particles from the water column. The specific food habits of the species are unknown, but other freshwater mussels have been documented to feed on detritus, diatoms, phytoplankton, and zooplankton. The reproductive cycle of the Carolina heelsplitter is likely similar to that of other native freshwater mussels. Males release sperm into the water column; the sperm are then taken in by the females through their siphons during feeding and respiration. The females retain the fertilized eggs in their gills until the larvae (glochidia) fully develop. The mussel glochidia are released into the water, and within a few days they must attach to the appropriate species of fish, which are then parasitized for a short time while the glochidia develop into juvenile mussels. They then detach from their "fish host" and sink to the stream bottom where they continue to develop, provided they land in a suitable substrate with the correct water conditions. The Carolina heelsplitter' s life span, the fish host species, and many other aspects of its life history are unknown.
REASONS FOR CURRENT STATUS:
The decline in the species throughout its range has been attributed to several
factors, including siltation resulting from poorly implemented agricultural,
forestry, and development activities; golf course construction; road
construction and maintenance; runoff and discharge of municipal, industrial, and
agricultural pollutants; habitat alterations associated with impoundments,
channelization, dredging, and sand mining operations; and other natural and
human-related factors that adversely modify the aquatic environment. Many of
these same factors threaten the remaining populations of the species.
Waxhaw Creek and Goose Creek are small streams containing a limited amount of suitable habitat for the Carolina heelsplitter. The two populations within Waxhaw and Goose Creeks appear to be extremely small and declining, and restricted to a few scattered sites within short reaches of each of these creeks. The Lynches River/Flat Creek population also appears to be relatively small and is restricted to a few scattered sites along short reaches of these streams (Keferi, personal communication, 1991). The Turkey Creek/Mountain Creek/Beaverdam Creek population was only recently discovered (Alderman 1995), and little is presently known about the status and abundance of the species in these three streams. The low numbers of individuals and the restricted range of each of the surviving populations makes them extremely vulnerable to extirpation from a single catastrophic event or activity, such as a toxic chemical spill, temporary failure of a waste treatment facility, channel alteration, etc. Also, the existing and potential future land uses of the surrounding area threaten the habitat and water quality of all four populations with increased discharge or runoff of silt, sediments, and organic and chemical pollutants.
MANAGEMENT AND PROTECTION:
Assuring the long-term survival of the Carolina heelsplitter will require, at a
minimum: (1) protecting the existing water and habitat quality of the streams
where the Carolina heelsplitter is still surviving; and, (2) improving degraded
portions of the species habitat and, reestablishing and protecting additional
populations of the species within portions of its historic range from which it
has extirpated. This will require compliance with existing State and Federal
regulations and assistance from the public and local governments and industries
in implementing recovery actions. Also, additional research on the threats to
the species, the environmental requirements of the heelsplitter and fish host(s),
and propagation and reintroduction techniques for freshwater mussels is needed.
REFERENCES
Alderman, J. M. 1995. Freshwater mussel inventory of the Stevens Creek Subbasin, Long Creek Ranger District, Sumter National Forest, South Carolina. Unpublished report to the U.S. Forest Service. 38 pp.
Alderman, J.M. 1998. Survey for the Endangered Carolina Heelsplitter (Lasmigona decorata)in South Carolina. Final Report to the South Carolina Department of Natural Resources.
Clarke, A. H. 1985. The Tribe Alasmidontini (Unionidae: Anodontinae), Part II: Lasmigonaand Simpsonaias. Smithsonian Contributions to Zoology, (399):57-60. SmithsonianInstitution Press, 75 pp., 22 figures, 14 tables.
Conrad, T. A. 1835. Appendix (to: New Fresh Water Shells of the United States with coloredillustrations, and a monograph of the genus Anculotus of Say; also a synopsis of theAmerican naiades. 76 pp.) Additions to, and corrections of, the catalogue of species of American naiades, with descriptions of new species and varieties of fresh water shells. Judah Dobson, Philadelphia, PA. P. 4, pl. 9, fig. 1.
Keferl, E. P. 1991. A Status Survey for the Carolina heelsplitter (Lasmigona decorata), aFreshwater Mussel Endemic to the Carolinas. Unpublished report to the U.S. Department of the Interior, Fish and Wildlife Service. 51 pp.
Keferl, E. P., and R. M. Shelly. 1988. The Final Report on a Status Survey of the Carolina Heelsplitter, Lasmigona decorata, and the Carolina elktoe, Alasmidonta robusta. Unpublished report to the U.S. Department of the Interior, Fish and Wildlife Service. 47 pp.
Lea, I. 1852. Description of New Species of the family Unionidae. Transactions of the American Philosophical Society, 10:253-294. (Reprinted in 1852 in Observations on the Genus Unio, 5:9-50.)
------. 1863. Description of twenty-four New Species of Unionidae of the United States. Proceeding of the Academy of Natural Sciences of Philadelphia, 15:191-194.
------. 1872. Description of twenty-nine New Species of Unionidae of the United States. Proceeding of the Academy of Natural Sciences of Philadelphia, 24:155-161.
AUTHOR: John A. Fridell (see address below)For more information please contact:
Mr. John A. Fridell
U.S. Fish and Wildlife Service
160 Zillicoa Str.
Asheville, North Carolina 28801
Telephone: (828) 258-3939 ext. 225
Mr John M. Alderman
North Carolina Wildlife Resources Commission
244 Red Gate Road
Pittsboro, North Carolina 27321
Telephone: (919) 542 5331
Dr. Eugene Keferl
Department of Natural Science
Brunswick Junior College
Brunswick, Georgia 31523
Telephone: (912) 264 7233
Species Distribution from known occurrences. Species may occur in similar habitats in other counties.Green counties indicate observed within 20 years. Yellow counties indicate an obscure data reference to the species in the county. Red counties indicate observed more than 20 years ago.
For additional information regarding this Web page, contact John Fridell, in Asheville, NC, at john_fridell@fws.gov
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