''Theliderma sparsa'', the Appalachian monkey-face pearly mussel or Appalachian monkeyface, 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

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 divers ...

, the river mussels. This species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to western

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

and eastern

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 ...

in the Appalachia region, in the

Southeastern United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...

. It is critically endangered due to pollution of the rivers in which it lives. Being a detritivore, the mussel absorbs the pollutants which contaminate the river as it feeds.

Distribution

There are two to three populations remaining. In the

Clinch River The Clinch River is a river that flows southwest for more than through the Great Appalachian Valley in the U.S. states of Virginia and Tennessee, gathering various tributaries, including the Powell River, before joining the Tennessee River in Ki ...

of Virginia there is a small, isolated population. A population in the upper Powell River in Tennessee is nearly gone. These occurrences may not be viable. All other occurrences have been

extirpated Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...

Reproduction

Like other unionid mussels, ''Theliderma sparsa'' uses fish as an intermediate host for its glonchidia larvae. Captive breeding experiments have demonstrated that the mussel larvae can develop on the gills of blotched chub (''Erimystax insignis'') and streamline chub (''Erimystax dissimilis''). Water temperature and vibration prompt release of glonchidia, according to

Virginia Department of Wildlife Resources The Virginia Department of Wildlife Resources is a department of the government of the U.S. state of Virginia that regulates wildlife conservation. History The Virginia Department of Game and Inland Fisheries was created on June 17, 1916, under the ...

Southwest Virginia Mussel Recovery Coordinator Tim Lane.

References

Molluscs of the United States Ecology of the Appalachian Mountains Endemic fauna of Tennessee Endemic fauna of Virginia Critically endangered fauna of the United States sparsa Bivalves described in 1841 Taxonomy articles created by Polbot {{Unionidae-stub