The fanshell (''Cyprogenia stegaria'') 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 ...

of 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 ...

. This

clam Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two shel ...

is native to the United States, where breeding populations remain in only three rivers. It is a federally listed endangered species of the United States. This clam is known to be reproducing 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 ...

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 ...

and

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 the

Green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combi ...

and Licking Rivers in

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 ...

. There may be a small reproducing population in the

Tennessee River The Tennessee River is the largest tributary of the Ohio River. It is approximately long and is located in the southeastern United States in the Tennessee Valley. The river was once popularly known as the Cherokee River, among other name ...

. There also may be some small populations remaining in several states, but these are not reproducing.Jones, J. W. and R. J. Neves. (2002)
Life history and propagation of the endangered fanshell pearlymussel, ''Cyprogenia stegaria'' Rafinesque (Bivalvia:Unionidae).
''Journal of the North American Benthological Society'' 21(1) 76. This species is threatened by the loss and degradation of its habitat.USFWS
Designation of the freshwater mussel, the fanshell as an endangered species.
''Federal Register'' June 21, 1990.

Reproduction

All Unionidae are known to use the gills, fins, or skin of a host fish for nutrients during the larval

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 t ...

stage. ''Cyprogenia stegaria'' release into the water a conglutinate mimicking an

Oligochaeta Oligochaeta () is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadrile earthworm ...

worm which contains the mussel's young. When a fish bites into the conglutinate lure, the young glochida are released and latch onto the fish's gills for nutrients.

References

Unionidae Fauna of the United States Bivalves described in 1820 Taxa named by Constantine Samuel Rafinesque Taxonomy articles created by Polbot ESA endangered species {{Unionidae-stub