Freshwater Fish - Species

Eastern pondmussel (Ligumia nasuta)

Description: (Anatomy of a Shellfish)
Shell shape elongated, subelliptical, thin to subsolid and more or less compressed, shell length 102 mm. Sexual dimorphism in the shells is well marked. The posterior margin of the male shell tapers evenly to a blunt point. The ventral margin of the female shell is expanded in the postbasal region, becoming a broad rounded projection. The posterior ridge is well developed, distinct and angled near the umbo, becoming rounded posteriorly. Periostracum is dark olive green to brownish and often with faint dark green, straight and narrow rays present, especially in juvenile specimens. The rays may be completely absent. Nacre is bluish-white, some with salmon in the umbo area, iridescent posteriorly.

Range: This species is known historically from the Savannah, Pee-Dee, and Cooper-Santee River basins.

Average Length:  102 mm

Life Expectancy:  Approximately 1-7 years

Preferred Habitat

Mussels were historically abundant in most permanent rivers and streams in North America. Sometimes, mussels can be found in temporary bodies of water such as sloughs and oxbow lakes, that occasionally receive water from rivers during flood events. Mussels are not usually found in streams that experience frequent drying or dry periods of long duration. 

Food Habits

  • Eastern pondmussel are filter feeders that remove particles from the water. 
  • They feed primarily on phytoplankton (algae), which they filter from the sandy or muddy bottom of streams, lakes, or canals.
  • Several studies have shown that they can improve water quality by reducing quantities of excessive algae and nutrients.

Reproduction

  • In most species of freshwater mussels, the sexes are separate. Males release sperm into the water column, and females take in the sperm when filtering the water.
  • Fertilization occurs internally, and the female mussel remains gravid, anywhere from several weeks to several months.
  • Most species of larval mussels, called glochidia, must undergo a parasitic stage in which they attach to the gills or fins of a fish in order to complete development. Some mussel species can use a variety of different fish species as hosts, while others are limited to one or very few fish species.
  • In order to increase their chances of finding a suitable host, many female mussels grow an extension of the mantle flap that looks like a small fish, crayfish, insect, or worm to attract a predatory fish host. When the fish attacks, the female releases her glochidia at just the right time.

Literature Cited

US Geological Survey. NAS Nonindigenous Aquatic Species
http://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=92

Bogan, A. E., J. Alderman, and J. Price. 2008. Field guide to the freshwater mussels of South Carolina. (Adobe PDF - 2MB) South Carolina Department of Natural Resources, Columbia. 43 pages