TP9 Ecotoxicology of Atrazine in Amphibians
Room 12A/B, Level 4
2:10 PM - 5:30 PM, Tuesday, 11 November 2003
Chair: Solomon, Keith ,
Co-chair: Smith, Ernest ,
(319) Effects of Atrazine on Gonadal Development of the African Clawed Frog, Xenopus laevis .
Cox, C.1, Brown Sullivan, K.1, 1 Department of Biological Sciences, Wichita State University, Wichita, KS, USA
ABSTRACT- Atrazine, a triazine herbicide used to control broadleaf weeds, is used extensively in agricultural regions of the United States. In surface waters, concentrations of 20 
g/L are typical; in temporary pools adjacent to fields atrazine may exceed 275 g/L. National attention has been given to recent reports that low-level exposure to atrazine during amphibian development demasculinizes Xenopus laevis and reduces testosterone levels in adult males (e.g., Hayes). Additionally, snall numbers of hermaphrodites have been noted among individuals exposed to low atrazine concentrations in this species. While gonadal abnormalities have been reported under laboratory conditions, field exposure to atrazine in South Africa is not associated with gonadal malformations (Carr, JA, Giesy JP and associates). The purpose of this study was to examine gonadal differentiation in preserved specimens of X. laevis that had been exposed to atrazine (0, 40 and 320 g/L)during larval development. These tadpoles have been reported to exhibit delayed time to metamorphosis and decreased size in the 320 g/L atrazine treatment. Specimens preserved in 70% ethanol were dissected and the gonadal-kidney complex was removed and placed in Bouin fixative for 48 hours, followed with final fixation in 70% ethanol. Individuals were examined without knowledge of atrazine treatment. Results indicate that atrazine did have effects on gonadal development and the ratio of males to females in the different treatment groups. Xenopus exposed to 320 g/L exhibited 54.2% females, 41.7% normal males and 4.2% hermaphrodites. Three percent of males exhibited multiple testes. Individuals exposed to 40 g/L atrazine comprised 1.8% hermaphrodites and 2.6% of males with multiple testes. The control group exhibited 51.2% and 48.8% males and females, respectively, and no abnormalities. Other authors have proposed that atrazine, acting as an endocrine disruptor, induces synthesis of aromatase, which, in turn, converts testosterone to estrogen.
Key words: Xenopus laevis, Atrazine, Hermaphrotidism