Quadrula cylindrica cylindrica
Life History and Biology
DESCRIPTION: The rabbitsfoot is a medium-sized to large mussel that reaches about six inches in length. Key characters useful for distinguishing it from other mussels include its elongated shape, shell sculpture of large, rounded, low bumps, and the color pattern that is generally smooth and yellowish to greenish usually with dark green or nearly black chevrons and triangles pointed ventrally. Growth rest periods (age rings) appear as grooves in the shell. Internally, the shell is white and iridescent.
RANGE: The rabbitsfoot was an exceptionally wide-ranging species, known from 139 streams in 15 states. Populations persist in 49 streams in 13 states, however, thousands of miles of the species’ historically available habitat no longer supports rabbitsfoot and the total range reduction and overall population loss likely exceeds 90%. Of the remaining populations only 10 are considered to be large enough to remain viable in the long-term.
In Pennsylvania, the rabbitsfoot still occurs in the French Creek and tributaries (Muddy Creek, LeBoeuf Creek, Conneautee Creek), and in limited areas of the Allegheny and Shenango Rivers.
HABITAT: The rabbitsfoot occurs in a variety of flowing water habitats including small to medium-sized streams and some larger navigable rivers. It usually occurs in shallow areas along the bank and adjacent runs and shoals where the water velocity is reduced, although specimens have been reported in 9-12 feet of water. Bottom substrates generally include sand and gravel. This species seldom burrows, but lies on its side.
Rabbitsfoot are sedentary filter feeders, obtaining oxygen and food directly from the water column or from water flowing through the substrate. Reproduction requires stable, undisturbed habitat and a sufficient population of host fish (likely hosts include shiners of the genera Cyprinella, Luxilus, Notropis), to complete larval development. Rabbitsfoot are relatively long-lived (20 to 60 years).
REASONS FOR CURRENT STATUS:Significant habitat loss, range restriction, and population fragmentation and size reduction have rendered the rabbitsfoot vulnerable to extinction. Threats include exotic species, sedimentation; small population sizes; isolation of populations; livestock grazing; wastewater effluents; mine runoff; unstable and coldwater flows downstream of dams; gravel mining; and channel dredging. Many of the remaining populations are isolated and may be eliminated by single catastrophic events, such as toxic spills. Natural repopulation is impossible without human intervention.
Conservation actions that may benefit rabbitsfoot are programs that support life history research and surveys and those that contribute to public understanding of the functions that rabbitsfoot and other mussels play in the environment. Ensuring that regulations designed to protect water quality and aquatic habitats are fully implemented is vital to maintaining or enhancing remaining rabbitsfoot populations.