The Cracking Pearlymussel (Hemistena lata) is an 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 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...

.

This species is native to the United States, where it remains only 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...

. It was originally distributed in the Ohio River

Ohio River

The Ohio River is the largest tributary, by volume, of the Mississippi River. At the confluence, the Ohio is even bigger than the Mississippi and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream...

, Cumberland River

Cumberland 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...

 and 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...

 systems, but it has been extirpated from most of its previous range.

Parmalee and Bogan reported that there were still populations 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. Other populations that are known to survive are located in the Powell

Powell River (Virginia)

The Powell River in the United States rises in southwest Virginia and flows into East Tennessee.The river rises in rural Wise County, Virginia near the Laurel Grove community northwest of Norton and flows for several miles before the confluence with Roaring Fork in the Kent Junction community...

 and Elk

Elk River (North Carolina)

The Elk River is a large stream in the North Carolina High Country and East Tennessee. The headwaters begin from the Northwestern slopes of Peak Mountain in Avery County, North Carolina and end at the Watauga River in Carter County, Tennessee.-Hydrography:...

 Rivers.

Shell description

These mussels have thin, fairly weak, elongated shells

Mollusc shell

The mollusc shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes...

. The shells may reach up to 69 millimetres (2.7 in) in height The outer coloring of the shell varies from yellow to brown, while the interior of the shell is pale bluish white, with a purple beak cavity.

Ecology

This species spends its adult life buried under the sand or mud in the bottom of medium-sized, flowing rivers. The females capture sperm released into the water by males. They store the sperm until they need them to fertilize their eggs. After fertilization, the females release the larvae into the river where the larvae attach to fish. Once the larva mature into juveniles with shells, they leave their host fish and drop to the sediment where they bury themselves. This process, therefore, requires an environment with ample fish to act as hosts. They prefer relatively shallow (usually less than 2 ft deep) water with a moderate current.

Conservation

The main threats to the continued existence of this species are habitat changes due to dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

ming of rivers, silting of rivers due to erosion caused by construction, farming and logging, and poisioning due to agricultural and industrial pollution

Pollution

Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

. The U.S. Fish and Wildlife Service has created a recovery plan for this species.