The effect of season and location on phosphoadenylate concentrations and adenylate energy charge in two species of freshwater clams.

Concentrations of phosphoadenylate nucleotides and the adenylate energy charge ((ATP+1/2ADP)/(ATP+ADP+AMP)) have been suggested as sensitive integrating measures of the energy state of organisms. This synoptic study investigated the seasonal and spatial variation of phosphoadenylate concentrations and AEC in two freshwater bivalve molluscs, the paper-shell clam, Anodonta imbecillis and the asian clam, Corbicula fluminea. Concentrations of all three adenylates, as well as the total adenylate concentration and adenylate energy charge of both species varied seasonally. These fluctuations were closely related to reproductive periods in both species. Total adenylate concentrations and ATP concentrations were slightly negatively correlated with shell length in A. imbecillis but the ADP and AMP concentrations and AEC were not significantly correlated with shell length. In C. fluminea the AEC was negatively correlated were positively correlated with shell length. Neither species exhibited significant differences in AEC between two collection locations. When C. fluminea collected from the Savannah River were acclimated and fed in the laboratory their AEC increased significantly.

Tissue metal concentrations in two crayfish species cohabiting a tennessee cave stream.

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.