Effects of polychlorinated biphenyl 126 on green frog (Rana clamitans) andleopard frog (Rana pipiens) hatching success, development, and metamorphosis

Although increasing evidence links planar chlorinated hydrocarbons, such as polychlorinated biphenyls (PCBs), to decreases in survival and reproductio n of fish, mammals, and birds near Green Bay, Wisconsin, and the Great Lake s, USA, relatively little is known of their bioaccumulation or of their pos sible effects in amphibians. We exposed embryos and larvae of two ranid spe cies commonly occurring in the Green Bay ecosystem, the green frog (Rana cl amitans) and the leopard frog (Rana pipiens), to PCB 126, a model coplanar PCB compound. Nominal concentrations ranged from 0.005 to 50 mu g/L, and ex posure lasted through metamorphosis. Tissue concentrations of PCB 126 in ta dpoles that did not metamorphose by the end of the experiment ranged from 1 .2 to 9,600 ng/g wet mass. No significant mortality of embryos occurred bef ore hatching; however, survival of larvae was significantly reduced at the highest concentration for both species. Few deformities were observed, bur the incidence of edema was significantly higher in tadpoles exposed to 50 m u g/L. Swimming speed and growth of tadpoles was also significantly reduced in this treatment. The percent of tadpoles that reached metamorphosis was significantly lower in green frogs at the highest concentration, and no leo pard frogs survived past day 47 of the experiment in this treatment. At hig h concentrations, PCB 126 affected both ranid species; however, sublethal e ffects were not apparent for the parameters we measured at concentrations t hat occur in water in the Green Bay ecosystem.