PALENSKE, N.M.*; DZIALOWSKI, E.M.; University of North Texas; University of North Texas: Effects of the Environmental Contaminant Triclosan on the Physiology of Developing Xenopus laevis Tadpoles

Amphibians lay eggs and develop in an aquatic habitat making their development and metamorphosis susceptible to environmental contaminants. The goal of this study was to determine the effects of triclosan, an antimicrobial used in consumer products, on the development and physiology of Xenopus laevis tadpoles. We investigated the LC50 for triclosan in stage 41 X. laevis tadpoles and the cardiovascular responses to chronic triclosan exposure. Larval X. laevis were chronically exposed to one of three concentrations of triclosan (0, 2.3, 230 µg L^-1), as well as a co-solvent control treatment of 230 µg L^-1 ethanol. Animals were reared in a density of 6 tadpoles L^-1 at each of the four concentrations. Heart rate was measured in each group on days 55 and 72 of chronic exposure. Stage 41 X. laevis tadpoles had a triclosan LC50 of 342.7 µg L^-1. On day 55 X. laevis had reached stages 47-54 of development and their survival appears to be more sensitive to acute triclosan exposure at these stages. There was a significant effect of triclosan exposure on heart rate after 55 days exposure (p<0.05). Individuals exposed to 2.3 µg L^-1 triclosan (104 ± 14 bpm) and 230 µg L^-1 triclosan (115 ± 12 bpm) had significantly lower heart rates than control tadpoles (control = 137 ± 12 bpm and ethanol control = 121 ± 17 bpm). Heart rate decreased from day 55 to day 72 of exposure. The heart rate of tadpoles exposed to 230 µg L^-1 triclosan (92 ± 6 bpm) remained significantly (p<0.05) lower than the control animals (108 ± 14 bpm). These results suggest that the environmental contaminant triclosan has a deleterious effect on the cardiovascular development of X. laevis tadpoles.