PARENT SESSION
PS1 - Wildlife Toxicology
Sunday, 17 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P001) Exposure characterization and responses to field exposures of Xenopus laevis to atrazine and related triazines in South African corn growing regions.
Du Preez, L*,1, Solomon, K2, Jooste, A1, Jasen van Rensburg, P1, Smith, E3, Carr, J3, Kendall, R3, Giesy, J4, Gross, T5, Van Der Kraak, G2, 1 Potchefstroom University, Potchefstroom 2520, SOUTH AFRICA2 University of Guelph, Guelph, Ontario, CANADA3 Texas Tech University, Lubbock, TX, USA4 Michigan State University, East Lansing, MI, USA5 Florida Caribbean Science Center-USGS-BRD, Gainesville, FL, USA
ABSTRACT- Recent studies in mammals and reptiles suggest that atrazine may interfere with the endocrine regulation of reproduction, possibly via effects on gonadal aromatase activity. A recent study by Hayes reported that atrazine exposures (1-200 
g/L) decreased laryngeal size in male, but not female Xenopus laevis, relative to unexposed controls. In addition, it has been reported that exposure of Xenopus to atrazine in laboratory studies increased the incidence of intersex gonads. and induced changes in plasma testosterone concentrations. However, the responses to atrazine observed in laboratory tests with X. laevis have yet to be observed in exposed field populations. The aim of this study was to ascertain whether exposure to atrazine and related triazines has caused endocrine responses in X. laevis under field conditions in South Africa (SA). Corn is grown intensively in the northern and central parts of SA. Because of limited surface water and lack of irrigation water sources, most farms have natural or constructed ponds where Xenopus are found. Concentrations of atrazine in experimental sites ranged from 0.1 to 1.2 g/L prior to the field use season and increased to concentrations ranging from 1.5 - 11.6 g/L during the field use season. Reference sites had concentrations < 0.1 g/L prior to the field use season and increased to concentrations ranging from < 0.1 - 0.3 g/L during the field use season. Starting in November 2001, weekly and later on two-weekly samples of water were taken to characterize exposures of Xenopus populations to atrazine, related triazines and metabolites, and other pesticides. During the period March - May 2002 metamorphs, and adult X. laevis as well as adult Afrana angolensis were collected and examined. Blood samples were taken for atrazine and hormonal analyses while larynxes and gonads were inspected and collected for morphological abnormalities, histology and aromatase activity. No abnormalities were observed in females. In male frogs a few frogs with only one testis were observed but no correlation was found between abnormalities and atrazine exposure. No indication of intersex was not observed in any of the examined specimens. Results of hormone analyses will be presented.
Key words: Triazine, Atrazine, Xenopus, Endocrine