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 ,
(315) Gonadal responses of Xenopus laevis Larvae Exposed to Atrazine in Microcosms.
Du Preez, L1, Jooste, A1, Everson, G1, Giesy, G2, Solomon, K3, 1 Potchefstroom University, Potchefstroom, North West, South Africa2 Michigan State University, East Lansing, Michigan, USA3 University of Guelph, Guelph, Ontario, Canada
ABSTRACT- This study addressed whether exposure to atrazine had any effect on Xenopus laevis tadpoles in a semi-natural environment, particularly as related to gonadal development. Twelve microcosms were used during this study, with triplicates of each treatment and three microcosms with no atrazine as controls. The nominal concentrations of atrazine used in experimental microcosms were 1, 10, and 25 
g/L. Each microcosm was 2.25 m long, 1.2 m wide, and 0.4 m deep. Ponds were lined with polyethylene membrane and prepared with a sediment bottom and macrophytes introduced. Tadpoles were obtained via induced spawning. Eight hundred tadpoles (48 h post hatch were randomly selected and released into each of the ponds. Tadpole development, water level, temperature, pH, conductivity and dissolved oxygen were monitored on a weekly basis. Atrazine concentration was verified bi-weekly. Metamorphs were removed from ponds at developmental stage 66, anaesthetized with MS-222, measured, weighed, individually numbered and fixed in Bouin fixative. Gonads were examined for gross morphological abnormalities and digitally photographed. No concentration-response was observed for gross gonadal abnormalities which ranged from 0.7% to 4.0%. Histological examinations were performed on the gonads of 214 randomly selected specimens to check for abnormalities. Gonads were serially sectioned and each section examined. Testicular oocytes were measured and counted. Frogs at 56,5% in reference ponds had testicular oocytes compared to the 56,7% for 1 g/L ponds, 58,8% for 10 g/L ponds and 38,7% for 25 g/L ponds. The number of oocytes per specimen varied between 1 and 65 with the majority having < 10 oocytes per individual. No atrazine-related effects on frequency of occurrence or number of oocytes per animal were observed.
Key words: testicular oocyte, atrazine, microcosm, Xenopus