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Species Description

Pod Lance

Elliptio folliculata


Classification

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

Description

The Pod Lance is a medium-sized freshwater mussel. It has a distinctive, elongated shell that is rather compressed, which gives its shell a long and slender appearance. The periostracum (outer shell surface) is dark brown to black. The nacre (inner shell surface) is quite variable in appearance. It may be purple, pink or bluish-white.

Life Cycle

Some of the details about the complex life cycle of this mussel are not currently known, but the life history of Elliptio folliculata is presumed to be similar to related species. Male Pod Lance mussels release sperm into creeks and rivers. 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. This species is believed to be tachytictic (a short-term brooder). Tachytictic species generally spawn during early summer or late spring and mature glochidia are released from females near the end of summer. Parasitic glochidia must find and attach to the gills or fins of the appropriate host fish to complete development. The required host fish have not yet been identified for this species. The glochidia parasitize a fish host for a variable length of time, likely depending upon water temperature, fish species and other factors. Larvae transform into juvenile mussels on the fish and then release from the host to find a suitable substrate, often the clay, sand or gravel bottom of a creek or river.

Natural History

Pod Lance 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 in the clay, sand or gravel bottoms of creeks and rivers. This species has also been found in shallow portions of Lake Waccamaw in North Carolina, where it is usually associated with aquatic plants. Adult mussels are filter feeders and usually feed upon plankton and detritus from their aquatic environment. Pod Lance mussels 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 its gills and food particles are trapped and eventually digested.

Range

This species is found in the Savannah River drainage of Georgia and South Carolina, the Waccamaw River drainage of South Carolina and North Carolina and the Cape Fear River of North Carolina. Distribution within these Rivers and drainages is rather patchy, but large populations are believed to exist in Brier Creek and within the Savannah River near Augusta , Georgia .

Conservation Status

The status of the Pod Lance is undetermined in Georgia . It is believed that fairly large populations exist in portions of the Savannah River and its drainages within the state. However, the distribution of large populations of Pod Lance mussels is rather sporadic throughout its range. Like many freshwater mussels, this species has likely been adversely affected by pollution, habitat degradation and excess sedimentation.

Similar Species

Accurate identification of Elliptio species can be quite difficult. However, within the Savannah River and its drainages near the Georgia/South Carolina border, the Pod Lance is fairly distinctive. Its very elongated and compressed shell distinguishes it from most other freshwater mussels within its range in Georgia .