''Lampsilis powellii'' is a rare species of

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

known by the common name Arkansas fatmucket. It 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 elsew ...

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...

in the United States, where it occurs in the Ouachita, Saline, and

Caddo River The Caddo River is a tributary of the Ouachita River in the U.S. state of Arkansas. The river is about long.Calculated in Google Maps and Google Earth Course The Caddo River flows out of the Ouachita Mountains through Montgomery, Pike, and Clark ...

systems.USFWS
''Lampsilis powellii'' Recovery Plan.
February 10, 1992. It is one of two mussels endemic to Arksansas, the other being speckled pocketbook (''Lampsilis streckeri'').Posey, B
Stay at home mollusks.
''Life in the Rocks'' Jan-Mar 2011. It is a federally listed threatened species of the United States. This mussel, a bivalve mollusc in 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 diverse ...

, is oblong oval in shape and can reach over 10 centimeters in length. The shell is brownish to

olive green Olive is a dark yellowish-green color, like that of unripe or green olives. As a color word in the English language, it appears in late Middle English. Shaded toward gray, it becomes olive drab. Variations Olivine Olivine is the typical ...

to tawny in color on the outside and

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...

bluish white on the inner surface. The back end of the shell of the male is pointed and that of the female is rounded. The mussel occurs in deep pools with enough water flow to remove debris, but it does not occur in

riffle A riffle is a shallow landform in a flowing channel. Colloquially, it is a shallow place in a river where water flows quickly past rocks. However, in geology a riffle has specific characteristics. Topographic, sedimentary and hydraulic indica ...

s or impounded pools that lack water flow. The substrate is sand, sometimes with rocks and gravel. It often lives next to river islands with stands of water willow (''Justicia americana'') in water about a meter deep. During breeding the male releases sperm and the female siphons it from the water. The fertilized eggs remain in the gills of the female. The

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 ...

, the larvae of the mussel, are released into the water and attach to a host, which is a fish. The flap of the adult's mantle resembles a small fish and apparently attracts larger fish close enough for the glochidia to reach them. In a cyst on the fish they undergo metamorphosis to become juvenile mussels and then drop to the substrate to develop further. This mussel is threatened by a number of processes. The rivers it inhabits have been impounded by dams at a number of locations, forming lakes and reservoirs including

Lake Ouachita Lake Ouachita (''Pronounced WAH-shi-tah'') is a reservoir created by the damming of the Ouachita River by Blakely Mountain Dam (). Blakely Mountain Dam was built by the United States Army Corps of Engineers from 1948 to 1953 for hydroelectric p ...

Lake Hamilton and Lake Catherine Lake Hamilton and Lake Catherine are a pair of man-made lakes located in Hot Springs, Arkansas, serving as a tourist attraction for the area. Both Lakes were developed by Arkansas Power & Light. History Lake Hamilton Lake Hamilton is a res ...

. The rivers have been channelized and

dredged Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...

. They have undergone increased

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

and the flow rates have decreased enough that the sediment is not removed. Water quality has decreased because of runoff from

barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate ( Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

mining on the Caddo River and

bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO(O ...

mining on the Saline, and wastewater on a tributary of the Ouachita. Other sources of runoff include timber operations, roads, and

feedlot A feedlot or feed yard is a type of animal feeding operation (AFO) which is used in intensive animal farming, notably beef cattle, but also swine, horses, sheep, turkeys, chickens or ducks, prior to slaughter. Large beef feedlots are called conc ...

s. Most of the land in these river basins is used for

silviculture Silviculture is the practice of controlling the growth, composition/structure, and quality of forests to meet values and needs, specifically timber production. The name comes from the Latin ('forest') and ('growing'). The study of forests and wo ...

.USFWS
Threatened Status Determined for the ''Lampsilis powelli'' (Arkansas fatmucket).
''Federal Register'' April 5, 1990.

References

{{Taxonbar, from=Q3017558 powellii Endemic fauna of Arkansas Molluscs of the United States Endangered fauna of the United States Bivalves described in 1852 ESA threatened species Taxonomy articles created by Polbot