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The James’s spinymussel is slightly less than three inches in length. Adults have a dark brown shell with prominent growth rings and occasionally, short spines on each valve. Young mussels have a shiny yellow shell with or without spines.
The species has declined rapidly during the past two decades and now only exists in small, headwater tributaries of the upper James River basin in Virginia, the Dan River basin in Virginia and North Carolina and in only one county in West Virginia. The habitat for this spinymussel includes slow, free-flowing streams that are relatively free of sediment. A filter feeder, the James spinymussel feeds on plankton collected from water that passes over its gills. Too much silt or sediment in the water can clog the mussel’s siphon or feeding tube resulting in death.
Clean water is essential for the spinymussel throughout the stages of its life because the larvae, called glochidia, rely on a healthy population of native fish to survive. The larvae are released into the water and must attach to a fish host to survive. Once they grow out of the larval stage, the juvenile mussel releases itself from the fish host and settles in on the stream or river bottom.
Water pollutants, such as excess sediment and agricultural runoff, disrupt the natural flow regime and is a major factor in the reduction of the James spinymussel population. Another threat to this species is the invasion of the non-native Asiatic clam (Corbicula fluminea). Attempts are being made to reintroduce the endangered spinymussel back into its native waters.
References:
http://ecos.fws.gov/speciesProfile/profile/speciesProfile.action?spcode=F025
http://www.mendeley.com/research/life-history-endangered-james-spinymussel-pleurobema-collina-conrad-1837mollusca-unionidae/
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