The gulf moccasinshell (Medionidus penicillatus) 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...

, the river mussels. 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 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...

, Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

, and Georgia

Georgia (U.S. state)

Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

 in the United States, where it is in decline and 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 most of the rivers it once inhabited. 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 up to 5.5 centimeters long. The shell is yellowish or greenish brown with green rays. 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....

 of the shell is purplish or greenish with some iridescence

Iridescence

Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...

.

This mussel is native to the ACF River Basin

ACF River Basin

The ACF River Basin is the watershed of the Apalachicola/Chattahoochee/Flint River Basin, in the United States, that begins in northern Georgia and flows into the Gulf of Mexico at Apalachicola Bay, near Apalachicola, Florida...

, the watershed

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 of the Apalachicola

Apalachicola River

The Apalachicola River is a river, approximately 112 mi long in the State of Florida. This river's large watershed, known as the ACF River Basin for short, drains an area of approximately into the Gulf of Mexico. The distance to its farthest headstream in northeast Georgia is approximately 500...

, Chattahoochee

Chattahoochee River

The Chattahoochee River flows through or along the borders of the U.S. states of Georgia, Alabama, and Florida. It is a tributary of the Apalachicola River, a relatively short river formed by the confluence of the Chattahoochee and Flint Rivers and emptying into Apalachicola Bay in the Gulf of...

 and Flint Rivers

Flint River (Georgia)

The Flint River is a river in the U.S. state of Georgia. The river drains of western Georgia, flowing south from the upper Piedmont region south of Atlanta to the wetlands of the Gulf Coastal Plain in the southwestern corner of the state. Along with the Apalachicola and the Chattahoochee rivers,...

 around the intersection of the states of Alabama, Georgia, and Florida. Its range has declined 80% from the known previous distribution. There are fewer than 20 occurrences and it is uncommon at most sites. It is now found in the Flint and Chattahoochee Rivers and four tributaries, and Econfina Creek

Econfina Creek

Econfina Creek is a small river in the middle Florida Panhandle. It flows through hilly country, and has sections of whitewater rapids. Much of its flow comes from springs...

. It is nearly 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 state of Alabama.

Like other mussels, this species releases 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....

 that lodge in the gills of fish to develop into juvenile mussels. The host fish for this species include Etheostoma edwini (brown darter), Percina nigrofasciata

Percina nigrofasciata

The common name of Percina nigrofasciata is the blackbanded darter. It is one of the 324 fish species found in Tennessee....

(blackbanded darter), Gambusia holbrooki (eastern mosquitofish), and Poecilia reticulata (guppy).

External links

• Bogan, A.E. 2000. Medionidus penicillatus. 2011 IUCN Red List of Threatened Species. Downloaded on 23 September 2011.