Delayed effects of pre- and early-life time exposure to polychlorinated biphenyls on tadpoles of two amphibian species (Xenopus laevis and Rana temporaria).

This study examined the effects of polychlorinated biphenyls (PCBs) on the development of amphibians using Xenopus laevis and Rana temporaria as experimental animals. Amphibians were exposed at different life stages and via different routes to the technical mixtures Clophen A50 and Aroclor 1254 or to a non-ortho PCB congener (PCB 126). The effects of PCB exposure in amphibians, such as mortality, number and pattern of malformations, or body weight at the end of successful metamorphosis of tadpoles, depends on the route, the point of time of exposure during the complex life cycle of amphibians, and the length of the observation period. Retinoid concentrations were significantly altered in PCB dosed embryos. Presently used early-life time test systems such as the FETAX assay may underestimate toxic effects of compounds with long term response such as PCBs on amphibians.