''Alasmidonta atropurpurea'', common name Cumberland elktoe, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs ...

, an aquatic

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Unionidae The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is at its most diverse ...

, the river mussels.

Description

The Cumberland elktoe has a thin, but not fragile,

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

. 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 Nacre ( , ), also known as mother of pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer; it is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is f ...

) is shiny, with the color being white, bluish white, or sometimes peach or salmon.

Distribution

The Cumberland elktoe is endemic to the upper

Cumberland River The Cumberland River is a major waterway of the Southern United States. The U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed June 8, 2011 river drains almost of southern Kentucky and ...

system, and it still exists in 12 mostly small tributaries in southeast

Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virginia to ...

and north-central

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

. 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, sometimes called the Little Niagara, the Niagara of the South, or the Great Falls, is a waterfall on the Cumberland River in southeastern Kentucky. Spanning the river at the border of McCreary and Whitley counties, the waterfal ...

. 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.Cicerello, R. R., and E. L. Laudermilk. 2001. ''Distribution and status of freshwater mussels (Bivalvia: Unionoidea) in the Cumberland River basin upstream from Cumberland Falls, Kentucky''. Journal of the Kentucky Academy of Science 62(1):26–34. The original type locality was simply "river Cumberland," according to Clarke,Clarke, A. H. 1981. ''The tribe Alasmidontini (Unionidae: Alasmidontinae), Part 1: Pegias, Alasmidonta, and Arcidens''. Smithsonian Contributions to Zoology 326:1-101. who, upon ascertaining that the

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was lost, designated a

neotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

from the Clear Fork, a tributary to the Big South Fork, in

Fentress County, Tennessee Fentress County is a county located in the U.S. state of Tennessee. As of the 2020 census, the population was 18,489. Its county seat is Jamestown. History Fentress County was formed on November 28, 1823, from portions of Morgan, Overton a ...

. All verified sites of occurrence are in the

Cumberland Plateau The Cumberland Plateau is the southern part of the Appalachian Plateau in the Appalachian Mountains of the United States. It includes much of eastern Kentucky and Tennessee, and portions of northern Alabama and northwest Georgia. The terms "Alle ...

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 The elktoe (''Alasmidonta marginata'') is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels. This species is found in southeastern Canada and the eastern United States. Like many mussels, it ...

''). 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

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...

ally in the

Rockcastle River The Rockcastle River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed June 8, 2011 river primarily in Rockcastle County, Kentucky, United States. It is a tributary of the Cumberland Ri ...

, contrary to the assertion by Gordon and Layzer that they are

allopatric Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

. The Cumberland elktoe has apparently been extirpated from the main stem of the Cumberland River and

Laurel River The Laurel River is a tributary of the Cumberland River in southeast Kentucky in the United States. The river drains a rural region in the foothills of the Appalachian Mountains, in parts of Whitley and Laurel Counties. The town of Corbin is l ...

and its tributary,

Lynn Camp Creek Lynn Camp Creek is a stream in Hart County, Kentucky, Hart and LaRue County, Kentucky, LaRue counties, Kentucky, in the United States. It is a tributary of the Green River (Kentucky), Green River. Lynn Camp Creek was named for Benjamin Lynn, an exp ...

. The status of the Cumberland elktoe from the heavily coal-mined New River watershed, where there is a single known record,Gordon, M. E. 1991. ''Species accounts for Cumberland elktoe (Alasmidonta atropurpurea), oyster mussel (Epioblasma capsaeformis), Cumberlandian combshell (Epioblasma brevidens), purple bean (Villosa perpurpurea), and rough rabbitsfoot (Quadrula cylindrica strigillata)''. Unpublished report,

The Nature Conservancy The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US. Founded in 1951, The Natu ...

, Boston. 75 pp. 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 A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel 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,Cicerello, R. R. 1995. ''A survey of the unionids (Bivalvia: Unionidae) of Marsh Creek, McCreary County, Kentucky''. Unpublished report to the

U.S. Department of Agriculture The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of com ...

, Forest Service. Kentucky State Nature Preserves Commission, Frankfort. 21 pp. and the population in Rock Creek is also sizable.Cicerello, R. R. 1996. ''A survey of the unionids (Bivalvia: Unionidae) of Rock Creek, McCreary County, Kentucky''. Unpublished report to the U.S. Department of Agriculture, Forest Service. Kentucky State Nature Preserves Commission, Frankfort. 11 pp. 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 The muskrat (''Ondatra zibethicus'') is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitat ...

middens in the late 1980s.Bakaletz, S. 1991. ''Mussel survey of the Big South Fork National River and Recreation Area''. Unpublished M.S. Thesis,

Tennessee Technological University Tennessee Technological University, commonly referred to as Tennessee Tech, is a public research university in Cookeville, Tennessee, United States. It was formerly known as Tennessee Polytechnic Institute, and before that as University of Dixie ...

, Cookeville. 62 pp.Layzer, pers. comm., 1998. In: U.S. Fish and Wildlife Service. 2003
Agency Draft Recovery Plan for Cumberland Elktoe, Oyster Mussel, Cumberlandian Combshell, Purple Bean, and Rough Rabbitsfoot
Atlanta, Georgia. 176 pp. 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.

Ecology

Habitat

This species inhabits medium-sized rivers and may extend into headwater streams where it is often the only mussel present.Gordon, M. E., and J. B. Layzer. 1989. ''Mussels (Bivalvia: Unionoidea) of the Cumberland River: review of life histories and ecological relationships''. U.S. Department of the Interior, Fish and Wildlife Service Biological Report 89(15). 99 pp. 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 LayzerGordon, M. E., and J. B. Layzer. 1993. ''Glochidial host of Alasmidonta atropurpurea (Bivalvia: Unionidae)''. Transactions of the American Microscopical Society 112:145-150. 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

glochidia The glochidium (plural glochidia) is a microscopic larval stage of some freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels. These larvae are ...

until March. They found Cumberland elktoe glochidia to develop equally well on both

fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...

and

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

surfaces. Five native fish species were parasitized by Cumberland elktoe glochidia: * whitetail shiner ('' Cyprinella galactura'') * northern hogsucker (''

Hypentelium nigricans The northern hogsucker (''Hypentelium nigricans'') is a freshwater ray-finned fish belonging to the family Catostomidae, the suckers. It is native to the United States and Canada where it is found in streams and rivers. It prefers clear, fast-fl ...

'') * rock bass (''

Ambloplites rupestris The rock bass (''Ambloplites rupestris''), also known as the rock perch, goggle-eye, red eye, and black perch, is a freshwater fish native to east-central North America. This red eyed creature is a species of freshwater fish in the sunfish fa ...

'') * 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° ± .

References

This article incorporates public domain text (a

public domain The public domain (PD) consists of all the creative work A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...

work of the United States Government A work of the United States government, is defined by the United States copyright law, as "a work prepared by an officer or employee of the United States Government as part of that person's official duties." "A 'work of the United States Governmen ...

) from: * U.S. Fish and Wildlife Service. 2003
Agency Draft Recovery Plan for Cumberland Elktoe, Oyster Mussel, Cumberlandian Combshell, Purple Bean, and Rough Rabbitsfoot
Atlanta, Georgia. 176 pp. (captions description and distribution). * U.S. Fish and Wildlife Service. 2004
Recovery Plan for Cumberland Elktoe, Oyster Mussel, Cumberlandian Combshell, Purple Bean, and Rough Rabbitsfoot
Atlanta, Georgia. 168 pp. (caption ecology).

External links

{{Taxonbar, from=Q3017536 atropurpurea Bivalves described in 1831 Taxa named by Constantine Samuel Rafinesque ESA endangered species