clubshell

Pleurobema clava, the clubshell, is a federally endangered freshwater mussel in the family Unionidae native to river systems in the eastern United States, particularly in the upper Ohio River drainage, including rivers in Ohio, Pennsylvania, Indiana, Illinois, and historically Michigan. Like all North American unionid mussels, the clubshell has a complex life cycle requiring a specific fish host for its larval stage (glochidia). Juvenile glochidia must parasitize the gills or fins of a suitable host fish—in the case of P. clava, primarily darters and other small stream fish—before metamorphosing and dropping off as juvenile mussels. The shell is oval to elongated, brown to yellowish-brown, with a slightly inflated form. Clubshells inhabit clean, well-oxygenated streams with sand and gravel substrates and good water quality. The species has experienced dramatic population declines due to water quality degradation, impoundment, sedimentation from agriculture and development, and disruption of fish host populations. It is listed as Critically Endangered by the IUCN and as Endangered under the U.S. Endangered Species Act. Recovery efforts involve captive propagation and host fish identification.