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Species Description

Chipola Slabshell

Elliptio chipolaensis


Classification

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

Description

The Chipola Slabshell is a medium-sized freshwater mussel that measures less than 3.3 inches (85 mm) in length. It is oval in shape and somewhat inflated (thick or deep in appearance). The periostracum (outer shell surface) is chestnut colored and may have alternating dark and light-colored bands. The nacre (inner shell surface) color is salmon.

Life Cycle

Many of the specific details about the complex life cycle of this threatened mussel are not currently known, but the life history of Elliptio chipolaensis is presumed to be similar to related species. Male Chipola Slabshell mussels release sperm into slow or moderately-flowing 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. The parasitic glochidia must find and attach to the gills or fins of the appropriate host fish to complete development. The required fish hosts are not currently known 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 metamorphose into juvenile mussels on the fish and then release from the host to find a suitable substrate, often the muddy sand or silty sand bottom of a river.

Natural History

Many of the details about the natural history of the Chipola Slabshell 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 in the muddy or silty bottom of rivers. Adult mussels are filter feeders and usually feed upon plankton and detritus from their aquatic environment. Chipola Slabshell 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 the gills and food particles are trapped and eventually digested.

Range

Historically, the Chipola Slabshell was found in the Chipola River of Florida and a tributary of the Chattahoochee River in Alabama . It was once found in a portion of the Chattahoochee River in Early and Seminole counties of Georgia . However, it has apparently been extirpated from its historic Georgia and Alabama range.

Conservation Status

The Chipola Slabshell is listed as threatened by the United States Fish and Wildlife Service (USFWS). Within Georgia , it is presumed to be extirpated or extinct. This mussel was once found at 17 different sites, but today it is restricted to only four sites within the Chipola River of Florida. The population is apparently declining and the dwindling population size is primarily contributed to habitat loss due to the construction of impoundments, pollution and sedimentation. Increased sedimentation greatly interferes with effective filter feeding and can cause suffocation of freshwater mussels.

Similar Species

There are no species within the very limited range of the Chipola Slabshell that possess the same combination of a salmon nacre, chestnut outer shell and occasional light and dark bands on the periostracum.