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Species Description

Southern Creekmussel

Strophitus subvexus


Classification

Phylum: Mollusca
Subphylum:
Class: Bivalvia
Order: Unionoida
Family: Unionidae

Description

The Southern Creekmussel is a medium to large-sized freshwater mussel that can measure more than 6.0 inches (152 mm) in length, but usually measures less than 4.0 inches (100 mm). It has a smooth, thin shell that is nearly oval or elongate in shape. The posterior ridge is broadly rounded and the periostracum (outer shell surface) is greenish yellow to brown in color. The nacre (inner surface of the shell) is bluish white.

Life Cycle

Many of the specific details about the complex life cycle of this mussel are not currently known, but the life history of Strophitus subvexus is presumed to be similar to related species. Male Southern Creekmussels release sperm into slow flowing, small to large-sized creeks. Sperm enters females through siphon-like regions and fertilization of eggs occurs within female shells. These fertilized eggs develop into special larva called glochidia. Glochidia continue to develop and are released into the water column when fully matured. The parasitic glochidia must find and attach to the gills or fins of the appropriate host fish to complete development. Recent studies have identified several fish species as suitable hosts, including the Alabama Hogsucker (Hypentelium etowanum). The glochidia parasitize a fish host for a variable length of time, likely depending upon water temperature, fish species and other factors. Larvae metamorphose into juvenile mussels on the fish and then release from the host to find a suitable substrate, often the sand or mud bottom of a creek.

Natural History

Many of the details about the natural history of the Southern Creekmussel are not currently known, but they are believed to be similar to better known, related species. Larvae (glochidia) are parasitic upon tissue of fish hosts while completing the metamorphosis into juvenile mussels. Adult mussels are typically sessile and are found attached or buried within the mud or sand bottom of creeks. Adult mussels are filter feeders and usually feed upon plankton and detritus from their aquatic environment. Southern Creekmussels bring water from their habitat into their shells through specialized regions that are similar to the true siphons of clams. The water is then filtered over the gills and food particles are trapped and eventually digested.

Range

Historically, this freshwater mussel was distributed throughout river drainages of the Gulf Coast , from the Sabine River in Texas to the Appalachicola-Chattahoochee-Flint Basin in Georgia and Florida . However, today the distribution is rather sporadic and the species has been extirpated from portions of its range. Within western Georgia , it is found in portions of the Flint and Chattahoochee Rivers .

Conservation Status

The Southern Creekmussel is listed as Imperiled and Rare within Georgia . Due primarily to excess sedimentation, habitat degradation and pollution; this species has been extirpated from portions of its large historical range.

Similar Species

The Rayed Creekshell (Anodontoides radiatus) is the most similar freshwater mussel to the Southern Creekshell . The Rayed Creekshell is distinguished by the presence of prominent dark green rays over the surface of the entire shell.