The fanshell, scientific name Cyprogenia stegaria, is a species

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 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...

. This clam

Clam

The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...

 is native to the United States, where breeding populations remain in only three rivers. It is a federally listed endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 of the United States.

This clam is known to be reproducing in the Clinch River

Clinch River

The Clinch River rises in Southwest Virginia near Tazewell, Virginia and flows southwest through the Great Appalachian Valley, gathering various tributaries including the Powell River before joining the Tennessee River in East Tennessee.-Course:...

 in 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...

 and Virginia

Virginia

The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...

, and the Green

Green River (Kentucky)

The Green River is a tributary of the Ohio River that rises in Lincoln County in south-central Kentucky. Tributaries of the Green River include the Barren River, the Nolin River, the Pond River and the Rough River...

 and Licking Rivers

Licking River (Kentucky)

The Licking River is a tributary of the Ohio River in northeastern Kentucky in the United States. The river and its tributaries drain much of the region of northeastern Kentucky between the watersheds of the Kentucky River to the west and the Big Sandy River to the east.-Origin of name:The Native...

 in 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...

. There may be a small reproducing population in the Tennessee River

Tennessee River

The Tennessee River is the largest tributary of the Ohio River. It is approximately 652 miles 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 names...

. There also may be some small populations remaining in several states, but these are not reproducing.

This species is threatened by the loss and degradation of its habitat.

Reproduction

All Unionidae are known to use the gills, fins, or skin of a host fish for nutrients during the larval glochidia stage. Cyprogenia stegaria release into the water a conglutinate mimicking an Oligochaeta

Oligochaeta

Oligochaeta is a subclass of animals in the biological phylum Annelida, which is made up of many types of aquatic and terrestrial worms, and this includes all of the various earthworms...

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.