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 Unlo 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 South Carolina, a population of the
Carolina heelsplitter was discovered in
the spring of 1995 in the Savannah River system (Stevens Creek
watershed) (Alderman 1995).
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) 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 four populations of the
species are presently known to exist.
One small remnant population occurs in the Catawba River system
in Waxhaw Creek, a tributary to
the Catawba River, in Union County, North Carolina; 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; a third, slightly larger population, survives in
the Lynches River, part of the Pee Dee
River system, in Chesterfield, Lancaster, and Kershaw Counties,
South Carolina, and extends into
Flat Creek, a tributary to the Lynches River in Lancaster County,
South Carolina. In the Savannah
River system the species is known only from Turkey Creek and two
of its tributaries, Mountain Creek
and Beaverdam Creek, in Edgefleld County, South Carolina. No
evidence of a surviving population
has been found in recent years in the Saluda River system (Keferl
1991).
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.
Clarke,	A. H. 1985. The Tribe Alasmidontini (Unionidae:
Anodontinae), Part II: Lasmigona and
Simpsonaias. Smithsonian Contributions to Zoology, (399): 57-60.
Smithsonian Institution
Press, 75 pp., 22 figures, 14 tables.
Conrad, T. A. 1835. Appendix (to: New Fresh Water Shells of the
United States with colored
illustrations, and a monograph of the genus Anculotus of Say;
also a synopsis of the American
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, p1. 9, fig. 1.
Keferl,	E. P. 1991. A Status Survey for the Carolina heelsplitter
(Lasmigona decorata), a
Freshwater 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:	(704) 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