Alasmidonta atropurpurea
Encyclopedia
Alasmidonta atropurpurea, common name Cumberland elktoe, is a species
of freshwater mussel, an aquatic
bivalve mollusk in the family Unionidae
, the river mussels.
. The outside surface of the shell (periostracum
) is smooth, somewhat shiny, and covered with greenish rays. Young specimens have a yellowish brown periostracum, while specimens of adults are generally much darker. The inside surface of the shell (nacre
) is shiny, with the color being white, bluish white, or sometimes peach or salmon.
system, and it still exists in 12 mostly small tributaries in southeast Kentucky
and north-central Tennessee
.
The Cumberland elktoe is limited in distribution to the upper Cumberland River system in southeast Kentucky and north-central Tennessee, occupying streams both above and below Cumberland Falls
. This species appears to have occurred only in the main stem of the Cumberland River and primarily its southern tributaries upstream from the hypothesized original location of Cumberland Falls near Burnside
, Pulaski County, Kentucky. The original type locality was simply “river Cumberland,” according to Clarke, who, upon ascertaining that the type specimen was lost, designated a neotype from the Clear Fork, a tributary to the Big South Fork
, in Fentress County, Tennessee. All verified sites of occurrence are in the Cumberland Plateau
Physiographic Province, giving it one of the most restricted ranges of any Cumberlandian species.
There has been confusion about the historical distribution of this species because of its similarity to a congener - the elktoe (Alasmidonta marginata). Museum and literature records of Alasmidonta marginata from the Cumberland River drainage on the Cumberland Plateau should be verified because they may actually represent the Cumberland elktoe. Cicerello and Laudermilk maintains that these two species occur sympatrically in the Rockcastle River
, contrary to the assertion by Gordon and Layzer that they are allopatric.
The Cumberland elktoe has apparently been extirpated from the main stem of the Cumberland River and Laurel River and its tributary, Lynn Camp Creek. The status of the Cumberland elktoe from the heavily coal-mined New River
watershed, where there is a single known record, is unknown. Based on recent records, populations of the Cumberland elktoe persist in 12 tributaries:
The latter nine streams, which comprise the Big South Fork system, may represent a single metapopulation of the Cumberland elktoe; there may be suitable habitat for the species and/or its fish host
s in intervening stream reaches, potentially allowing for natural genetic interchange to occur.
Considered a “rare species”, few sites continue to harbor the Cumberland elktoe. Marsh Creek harbors the largest population known in Kentucky, and the population in Rock Creek is also sizable. In both streams the Cumberland elktoe represented the second most abundant unionid species. The Marsh Creek population, with at least three year classes present, is viable, but the viability of the Rock Creek population is questionable. The largest population in Tennessee is in the Big South Fork system in the headwaters of the Clear Fork system, where several hundred specimens were found in muskrat
middens in the late 1980s. Several age classes of the Cumberland elktoe were represented in samples taken from throughout the larger tributaries of the Big South Fork system in Tennessee during a 1985-86 survey.
until March. They found Cumberland elktoe glochidia to develop equally well on both fin
and gill
surfaces.
Five native fish species were parasitized
by Cumberland elktoe glochidia:
However, under laboratory conditions, juvenile specimens transformed only on the northern hogsucker. The period of glochidial encystment (i.e., until transformation into free-living juveniles) took 24 days, at 66.2° ± 5.4°F.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of freshwater mussel, an aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
bivalve mollusk in the family Unionidae
Unionidae
Unionidae is a family of freshwater mussels, the largest in the order Unionoida, the bivalve mollusks sometimes known as river mussels, naiads, or simply as unionids.The range of distribution for this family is world-wide...
, the river mussels.
Description
The Cumberland elktoe has a thin, but not fragile, shellBivalve shell
A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two parts, two valves which are hinged together...
. The outside surface of the shell (periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
) is smooth, somewhat shiny, and covered with greenish rays. Young specimens have a yellowish brown periostracum, while specimens of adults are generally much darker. The inside surface of the shell (nacre
Nacre
Nacre , also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent....
) is shiny, with the color being white, bluish white, or sometimes peach or salmon.
Distribution
The Cumberland elktoe is endemic to the upper Cumberland RiverCumberland River
The Cumberland River is a waterway in the Southern United States. It is long. It starts in Harlan County in far southeastern Kentucky between Pine and Cumberland mountains, flows through southern Kentucky, crosses into northern Tennessee, and then curves back up into western Kentucky before...
system, and it still exists in 12 mostly small tributaries in southeast Kentucky
Kentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
and north-central Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
.
The Cumberland elktoe is limited in distribution to the upper Cumberland River system in southeast Kentucky and north-central Tennessee, occupying streams both above and below Cumberland Falls
Cumberland Falls
Cumberland Falls, sometimes called the Little Niagara, the Niagara of the South, or the Great Falls, is a large waterfall on the Cumberland River in southeastern Kentucky...
. This species appears to have occurred only in the main stem of the Cumberland River and primarily its southern tributaries upstream from the hypothesized original location of Cumberland Falls near Burnside
Burnside, Kentucky
Burnside is a city in Pulaski County, Kentucky, United States. The population was 637 at the 2000 census. In 2005, Burnside became the only town in Pulaski County or any adjoining county to allow the sale of alcoholic beverages in qualified establishments...
, Pulaski County, Kentucky. The original type locality was simply “river Cumberland,” according to Clarke, who, upon ascertaining that the type specimen was lost, designated a neotype from the Clear Fork, a tributary to the Big South Fork
Big South Fork of the Cumberland River
The Big South Fork of the Cumberland River is a river in Tennessee and Kentucky. It is a major drainage feature of the Cumberland Plateau, a major tributary of the Cumberland River system, a world-class whitewater canoeing and kayaking stream, and the major feature of the Big South Fork National...
, in Fentress County, Tennessee. All verified sites of occurrence are in the Cumberland Plateau
Cumberland Plateau
The Cumberland Plateau is the southern part of the Appalachian Plateau. It includes much of eastern Kentucky and western West Virginia, part of Tennessee, and a small portion of northern Alabama and northwest Georgia . The terms "Allegheny Plateau" and the "Cumberland Plateau" both refer to the...
Physiographic Province, giving it one of the most restricted ranges of any Cumberlandian species.
There has been confusion about the historical distribution of this species because of its similarity to a congener - the elktoe (Alasmidonta marginata). Museum and literature records of Alasmidonta marginata from the Cumberland River drainage on the Cumberland Plateau should be verified because they may actually represent the Cumberland elktoe. Cicerello and Laudermilk maintains that these two species occur sympatrically in the Rockcastle River
Rockcastle River
The Rockcastle River is a river primarily in Rockcastle County, Kentucky. It is a tributary of the Cumberland River and therefore, via the Ohio River, part of the Mississippi River watershed. In 1750 it was discovered and named the Lawless River by Dr. Thomas Walker and his exploring party. It was...
, contrary to the assertion by Gordon and Layzer that they are allopatric.
The Cumberland elktoe has apparently been extirpated from the main stem of the Cumberland River and Laurel River and its tributary, Lynn Camp Creek. The status of the Cumberland elktoe from the heavily coal-mined New River
New River (Tennessee)
The New River is a tributary of the Big South Fork of the Cumberland River in the U.S. state of Tennessee. Via the Big South Fork and the Cumberland and Ohio rivers, it is part of the Mississippi River watershed....
watershed, where there is a single known record, is unknown. Based on recent records, populations of the Cumberland elktoe persist in 12 tributaries:
- Laurel Fork, Claiborne County, Tennessee and Whitley County, Kentucky and Marsh Creek, McCreary County, Kentucky
- Sinking Creek, Laurel County, Kentucky
- Big South Fork, Scott County, Tennessee, and McCreary County, Kentucky
- Rock Creek, McCreary County, Kentucky
- North White Oak Creek, Fentress County, Tennessee
- Clear Fork, Fentress, Morgan, and Scott counties, Tennessee
- North Prong Clear Fork and Crooked Creek, Fentress County, Tennessee
- White Oak Creek, Scott County, Tennessee
- Bone Camp Creek, Morgan County, Tennessee
- New River, Scott County, Tennessee
The latter nine streams, which comprise the Big South Fork system, may represent a single metapopulation of the Cumberland elktoe; there may be suitable habitat for the species and/or its fish host
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
s in intervening stream reaches, potentially allowing for natural genetic interchange to occur.
Considered a “rare species”, few sites continue to harbor the Cumberland elktoe. Marsh Creek harbors the largest population known in Kentucky, and the population in Rock Creek is also sizable. In both streams the Cumberland elktoe represented the second most abundant unionid species. The Marsh Creek population, with at least three year classes present, is viable, but the viability of the Rock Creek population is questionable. The largest population in Tennessee is in the Big South Fork system in the headwaters of the Clear Fork system, where several hundred specimens were found in muskrat
Muskrat
The muskrat , the only species in genus Ondatra, is a medium-sized semi-aquatic rodent native to North America, and introduced in parts of Europe, Asia, and South America. The muskrat is found in wetlands and is a very successful animal over a wide range of climates and habitats...
middens in the late 1980s. Several age classes of the Cumberland elktoe were represented in samples taken from throughout the larger tributaries of the Big South Fork system in Tennessee during a 1985-86 survey.
Habitat
This species inhabits medium-sized rivers and may extend into headwater streams where it is often the only mussel present. Gordon and Layzer reported that the species appears to be most abundant in flats, which were described by Gordon as shallow pool areas lacking the bottom contour development of typical pools, with sand and scattered cobble/boulder material, relatively shallow depths, and slow (almost imperceptible) currents. They also report the species from swifter currents and in areas with mud, sand, and gravel substrates.Hosts
Gordon and Layzer summarized the reproductive biology and identified fish hosts of the Cumberland elktoe. This anodontine species was found gravid from October through May, but they observed no fish infested with its glochidiaGlochidium
The glochidium is a special microscopic larval stage of larger freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels....
until March. They found Cumberland elktoe glochidia to develop equally well on both fin
Fin
A fin is a surface used for stability and/or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, . The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices...
and gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
surfaces.
Five native fish species were parasitized
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
by Cumberland elktoe glochidia:
- whitetail shiner (Cyprinella galacturaCyprinella galacturaThe common name of Cyprinella galactura is the Whitetail shiner. It is one of the 324 fish species found in Tennessee.-External links:FishBase:...
) - northern hogsucker (Hypentelium nigricans)
- rock bass (Ambloplites rupestris)
- longear sunfish (Lepomis megalotis)
- rainbow darter (Etheostoma caeruleum).
However, under laboratory conditions, juvenile specimens transformed only on the northern hogsucker. The period of glochidial encystment (i.e., until transformation into free-living juveniles) took 24 days, at 66.2° ± 5.4°F.