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Species Description

Wavyrayed Lampmussel

Lampsilis fasciola


Classification

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

Description

Lampsilis fasciola is a medium-sized freshwater mussel that usually measures less than 4.0 inches (102 mm) in length. The Wavyrayed Lampmussel is sexually dimorphic. Male specimens have shells that are rounded or nearly circular, whereas females have an oval-shaped shell that is usually moderately inflated or swollen in appearance. The shiny periostracum (outer shell surface) is light yellow to yellow green and decorated with a numerous, distinctive "wavy" green rays of varying widths. The nacre (inner surface of the shell) is white to bluish white.

Life Cycle

Some of the details about the complex life cycle of this mussel are not currently known, but several laboratory studies have recently been conducted to better understand the life history of Lampsilis fasciola. Male Wavyrayed Lampmussels release sperm into the moderate current of small to medium-sized 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 bradytictic (a long-term brooder). Bradytictic species usually spawn during the summer and release mature glochidia during the following spring. Parasitic glochidia must find and attach to the gills or fins of the appropriate host fish to complete development. In order to increase the probability that fish and glochidia will come in contact, the Wavyrayed Lampmussel displays a pigmented mantle flap that acts as a "lure" to attract fish. This lure mimics small fish and is often minnow-shaped to attract fish to the mussel and its mature glochidia (larvae). Recent laboratory studies have determined that the Largemouth Bass (Micropterus salmoides) and Smallmouth Bass (Micropterus dolomieu) are suitable hosts. 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 mud, sand or gravel bottoms of small to medium-sized rivers.

Natural History

Wavyrayed Lampmussel l arvae (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 mud, sand or gravel bottoms of rivers. This species is often found in moderately flowing water that is less than 3 feet in depth. Adult mussels are filter feeders and usually feed upon plankton and detritus from their aquatic environment. Wavyrayed 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

The Wavyrayed Lampmussel was historically found in several drainages of the Great Lakes . It is also found in Ohio River , Mississippi River and Tennessee River drainages. It has been found in extreme northwestern Georgia , within drainages of the Tennessee River system.

Conservation Status

This species is believed to be Rare within its narrow range in Georgia , but further studies and surveys should be conducted to verify its status. The Wavyrayed Lampmussel is widely distributed, but is declining in portions of its range. Pollution, introduction of the Zebra Mussel (Dreissena polymorpha) and construction of impoundments are believed to be the primary factors for the decline of this species.

Similar Species

Within its very small range in northwestern Georgia , this species is rather distinct. The characteristic "wavy" rays that decorate its shiny surface usually distinguish it from other freshwater mussels.