Endangered Species
Midwest Region



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Curtis' Pearlymussel (Epioblasma florentina curtisi)

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photo of Curtis' pearlymussel


This mussel requires clear, fast-flowing waters.


Status: Endangered


Habitat: This mussel prefers riffles within transitional zones of clean streams and rivers, between the swift-flowing headwaters and more leisurely, meandering currents farther downstream. It buries itself in sand or gravel in shallow water less than 30 inches deep.


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 to fertilize their eggs, which they store in their gill pouches until the larvae hatch. The females then expel the larvae. Those that manage to find a fish host to clamp onto by means of tiny clasping valves, 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: The Curtis' pearlymussel has suffered from habitat alteration due to gravel dredging and impoundments. Dams and reservoirs have flooded much of this mussel's habitat, reducing its gravel and sand habitat, its food supply and probably affecting the distribution of the fish hosts necessary for reproduction. Impoundments are fatal to most riverine mussels; one researcher counted 45 mussel species in a river before the construction of a dam. Four months after the dam was completed, he could find none.


The Curtis' pearlymussel has also been exported to the shelling industry for use as buttons and pins. Other threats include pollution from agricultural and industrial runoff. These chemicals and toxic metals become concentrated in the body tissues of such filter-feeding mussels as the Curtis' pearlymussel, eventually poisoning it to death.

Created November 1997





Last updated: September 21, 2016