M9 AM Ecotoxicology of Reptiles
Monday, 14 November 2005: 8:00 AM - 11:40 AM in 339-340

(AAA-1117-220665) Effects of environmentally relevant concentrations of atrazine on gonadal development of snapping turtles.

de Solla, S¹, Martin, P¹, Fernie, K¹, Park, B², Mayne, G¹, ¹ Canadian Wildlife Service, Burlington, Ontario, Canada² Department of Fisheries and Oceans, Winnipeg, Manitoba, Canada

ABSTRACT- The herbicide atrazine has been suspected of affecting sexual development by inducing aromatase resulting in the increased conversion of androgens to estrogens. We used snapping turtles (Chelydra serpentina), a species whose sex is dependent on the production of estrogen through aromatase activity in a temperature-dependent manner, to investigate if environmentally relevant exposures to atrazine affected gonadal development. Eggs were incubated in soil to which atrazine was applied at a typical field application rate (3.1 L/ha atrazine), one tenth of this rate (0.31 L/ha atrazine) and a control rate (no atrazine) for the duration of embryonic development. The incubation temperature (25 °C) was selected to produce only males. Although some males with testicular oocytes and females were produced in the atrazine treated groups (3.3 to 3.7%) but not in the control group, there were no statistical differences among treatments. Furthermore, snapping turtle eggs collected from natural nests in a corn field were incubated at the pivotal temperature (27.5 °C) where both males and females would normally be produced, and there were some males with oocytes in the testes (15.4%). The presence of low numbers of males with oocytes may be a natural phenomenon, and we have limited evidence to suggest that the presence of normal males with oocytes may represent a feminizing effect of atrazine. Histological examination of the thyroid gland revealed no effect on thyroid morphology.

Key words: atrazine, snapping turtles, gonadal development, thyroid