Endangered Species
Midwest Region



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White Wartyback (Plethobasus cicatricosus)


photo of white wartyback pearlymussel

No young or juvenile white wartyback mussels have been found since dam construction drastically altered their habitat.


Status: Endangered


Habitat: This mussel is found in clean, fast-flowing water in silt-free rubble, gravel and sand bottoms of large and rivers. It buries itself in sand or gravel between bedrock ledges with only the edge of its sell and its feeding siphons exposed.


Behavior: Reproduction requires a stable, undisturbed habitat and a sufficient population of fish hosts to complete the mussel's larval development. When the male discharges sperm into the current, females downstream siphon in the sperm in order to fertilize their eggs, which they store in their gill pouches until the larvae hatch. The females then expel the larvae. Those larvae that manage to attach themselves to the gills of a host fish grow into juveniles with shells of their own. At that point they detach from the host fish and settle into the streambed, ready for a long (possibly up to 50 years) life as an adult mussel.


Why It's Endangered: Dams and reservoirs have flooded most of this mussel's habitat, reducing its gravel and sand habitat and probably affecting the distribution of its fish hosts. Also, erosion caused by strip mining, logging and farming adds silt to many rivers, which can clog the mussel's feeding siphons and even bury it completely. Other threats include pollution from agricultural and industrial runoff. These chemicals and toxic metals become concentrated in the body tissues of filter-feeding mussels such as the white wartyback, eventually poisoning it to death.


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Last updated: October 10, 2018