Influences of atrazine on gonadal differentiation in Xenopus laevis tadpoles during metamorphosis

Xenopus laevis tadpoles were exposed for 48, 96 and 144 h during sexual differentiation to 1.8, 19 and 48 og/L atrazine. Following the exposure, tadpoles were microdissected for histological examination of the gonadal-kidney complex. The experimental tadpoles showed no significant difference in body weight, body length and in their development among the treatments. However, quantitative histological analysis of the gonads revealed a significant reduction of testicular volume, primary spermatogonial cell nests, and nursing cells in males as atrazine concentration and length of exposure increased. Females showed significant declines in primary oogonia cells and a significantly higher frequency of atresia with increasing atrazine concentration and length of exposure. The presence of a Wilms-like tumour was reported for the first time in tadpoles following exposure to atrazine. Qualitative histological analysis of the kidney showed a significant increase in the incidence of Renal Embryonal Adenosarcoma in all atrazine treated tadpoles. Females showed a significantly higher risk from developing tumours and tumour incidence as compared to males. These results suggests that the present non observable effect level (NOEL) for aquatic ecosystem of 20og/L atrazine should be reconsidered