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Species Description

Yellow Lampmussel

Lampsilis cariosa


Classification

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

Description

The Yellow Lampmussel is a medium to large sized freshwater mussel that can measure up to 5.1 inches (130 mm) in length. The periostracum (outer shell surface) is smooth and has a shiny, yellowish appearance that darkens with age. The nacre (interior surface of shell) is white to bluish white in appearance. This species is sexually dimorphic and females are identified by the development of a large mantle tissue flap that is displayed externally. Male specimens are more elongate in shape and do not display a mantle flap.

Life Cycle

Many of the specific details about the complex life cycle of this rare and imperiled mussel are not currently known, but the life history of Lampsilis cariosa is presumed to be similar to related species. Male Yellow Lampmussels release sperm into swiftly-flowing rivers and 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. This species has been found to be bradytictic. This means that it is a long-term brooder and usually spawns during the summer, releasing glochidia the following spring. When released, the parasitic glochidia must find and attach to the gills or fins of the appropriate host fish to complete development. Female Yellow Lampmussels have a well-developed mantle that is modified to a flap that holds glochidia and is presumed to be used as a "lure" to attract fish. This "lure" of glochidia increases the probability that a fish will come in contact with the mantle flap and release the glochidia when it approaches or attacks the lure. 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 sand or gravel bottom of a fast-flowing creek or river.

Natural History

Many of the details about the natural history of the Yellow Lampmussel 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 Yellow Lampmussels are primarily sessile and are often found nearly completely buried within the sand or gravel sediments of rivers and creeks. Adult mussels are filter feeders and usually feed upon plankton and detritus from their aquatic environment. Yellow Lampmussels 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 was historically found throughout most Atlantic Slope drainages, from the Ogeechee River drainage in Georgia north to the Sydney River in Canada . However; the range has declined and constricted, especially in the southern portion of its broad range where its distribution is rather patchy. Within Georgia , it is found in portions of the Ogeechee River drainage.

Conservation Status

This species is listed as Rare and Imperiled within Georgia . Unlike many rare freshwater mussels, the Yellow Lampmussel is believed to have some tolerance of mild changes within its environment. However; it is apparently rather susceptible to pollution, sedimentation and may be negatively impacted by the introduction of the Zebra Mussel (Dreissena polymorpha). Due primarily to these factors, the range and abundance of the Yellow Lampmussel has declined in recent years, especially in the southern portion of its range.

Similar Species

The most similar species to the Yellow Lampmussel is the Tidewater Mucket (Leptodea ochracea). The Tidewater Mucket is distinguished by the presence of rays that cover the entire surface of its thin shell. However, Leptodea ochracea has not been found in Georgia during recent surveys and has possibly been extirpated from the state.