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Species Description

Shiny-rayed Pocketbook

Lampsilis subangulata


Classification

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

Description

The Shiny-rayed Pocketbook is a medium-sized freshwater mussel that usually reaches 3.3 inches (85 mm) in length. Its shell is nearly elliptical in shape, with a rounded posterior ridge. The smooth, light yellowish-brown outer surface is shiny and decorated with bright emerald green rays. Its nacre (inner shell surface) is white in appearance.

Life Cycle

Unlike several freshwater mussels, many of the details about the complex life cycle of the Shiny-rayed Pocketbook have recently been determined through scientific experimentation and observation. Male Shiny-rayed Pocketbook mussels release sperm into rivers with slight to moderate currents. 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. Recent studies have found that female Shiny-rayed Pocketbooks release glochidia from late May through mid July, which corresponds to water temperatures of 68-74.3 F (20-23.5 C). The parasitic glochidia must find and attach to the gills or fins of the appropriate host fish to complete development. To attract fish and to improve the likelihood of the glochidia attaching to the required host fish females release their glochidia in a special manner. Female Shiny-rayed Pocketbooks release superconglutinate, a large packet of glochidia that resembles a long, transparent rope that ends with a concentrated, fish-like mass of glochidia. When the conglutinate mass of glochidia is eaten by a fish, the mass ruptures and glochidia attach to the gills of the fish. The primary fish hosts have recently been determined to be the Largemouth Bass (Micropterus salmoides) and Spotted Bass (Micropterus punctulatus). 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 or sandy bottoms of rivers with slow to moderate currents.

Natural History

Many of the specific details about the natural history of the Shiny-rayed Pocketbook are not currently known, but they are believed to be similar to better known, related species. Larvae (glochidia) are parasitic upon the tissue of fish hosts while completing the metamorphosis into juvenile mussels. Adult mussels are typically sessile and are often found attached or buried within the muddy or sandy bottom of slight to moderately flowing rivers. Adults are filter feeders and usually feed upon plankton and detritus from their aquatic environment. Shiny-rayed Pocketbook 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, Lampsilis subangulata was found throughout the Appalachicola-Chattahoochee-Flint (ACF) and Ochlockonee Rivers of Georgia, Alabama and Florida . However, today it is greatly reduced throughout its historical range and within Georgia it is only found in portions of the Chattahoochee , Flint and Ochlockonee Rivers .

Conservation Status

he declining numbers of Shiny-rayed Pocketbooks are sedimentation, over collection, pollution and construction of impoundments.

Similar Species

There are no species within the range of the Shiny-rayed Pocketbook that have a light yellowish brown shell marked with bright emerald green rays.