RESUMO
Concentrations of Cd, Cr, Cu, Fe, Mg, Mn, Pb, Zn, Ca and K were examined in tissues of the troglobitic (obligatory cave-dwelling) crayfish Orconectes australis australis and troglophilic (facultative cave-dwelling) species Cambarus tenebrosus. These two species cohabit a stream in Merrybranch Cave, located in rural White Co., Tennessee. Tissue concentrations of essential metals did not exhibit any trends between species. In contrast, Cd and Pb concentrations were found to be significantly greater in O. a. australis for almost all of the tissues analyzed. The higher Cd and Pb concentrations in O. a. australis are thought to be due to the increased longevity of this troglobitic species. Because of the toxicity of Cd and Pb, chronic exposure to relatively low concentrations of these metals could cause changes in mortality, fecundity or behavior in aquatic organisms possessing long life spans. The bioaccumulation of metals from low level, non-point sources is discussed in relation to life history strategies.