The dromedary naiad or dromedary pearly mussel (Dromus dromas) is a rare 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 freshwater mussel 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 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 is native to the Cumberland

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 in the United States, where it has experienced a large population decline. 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 mussel is yellow-green in color with interrupted green rays on the shell. The nacre

Nacre

Nacre , also known as mother of pearl, is an organic-inorganic composite material produced by some mollusks as an inner shell layer; it is also what makes up pearls. It is very strong, resilient, and iridescent....

 is white, pink, or reddish. The species got its name from the distinctive hump on the shell of larger individuals.

This species lives in clear, clean, fast-flowing water. It cannot tolerate water of poor quality, for example, water with silt

Silt

Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...

.

Like other freshwater mussels, this species reproduces by releasing larvae called glochidia

Glochidium

The glochidium is a special microscopic larval stage of larger freshwater mussels, aquatic bivalve mollusks in the families Unionidae and Margaritiferidae, the river mussels and European freshwater pearl mussels....

 into the water. The glochidia are eaten by fish and lodge in the fish's gills, where they develop into juvenile mussels. Fish hosts for this mussel species include black sculpin (Cottus baileyi), greenside darter (Etheostoma blennioides), fantail darter (Etheostoma flabellare), snubnose darter

Etheostoma simoterum

The common name of Etheostoma simoterum is the snubnose darter. It is one of the 324 fish species found in Tennessee.- Introduction :The following is a proposed conservation management plan for the snubnose darter Etheostoma simoterum...

 (Etheostoma simoterum), tangerine darter (Percina aurantiaca), blotchside logperch (Percina burtoni), logperch

Percina caprodes

Percina caprodes, the logperch or common logperch, is a fish species of the family Percidae. Like other logperches, it has the typical vertical barring along the flank and a subterminal mouth....

 (Percina caprodes), channel darter (Percina copelandi), gilt darter

Percina evides

The common name of Percina evides is the gilt darter. It is one of the 324 fish species found in Tennessee.-Introduction:This is a description of a monitoring plan for the Gilt darter , a native fish of Tennessee. The Gilt darter is one of 47 species of fish in the family Percina...

 (Percina evides), and Roanoke darter (Percina roanoka).

This species was historically one of the most common mussels in the Tennessee River. Now only old individuals can be found there. The species has been reduced to no more than 4 populations. It has been extirpated

Local extinction

Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...

 from the wild in the state of Alabama

Alabama

Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...

, but it has been reintroduced there. The only remaining reproducing populations occur in the Clinch

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:...

 and Powell Rivers. Reproducing populations remain in under 10% of the mussel's historical range, and the populations are disjunct.

Factors contributing to its decline include the impoundment

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...

 of waterways, increased silt, and pollution from sewage

Sewage

Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...

, coal mining

Coal mining

The goal of coal mining is to obtain coal from the ground. Coal is valued for its energy content, and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production. In the United States,...

, and oil and gas drilling.