WA5 Wildlife Toxicology: Forensic Approaches
203 Oregon Ballroom
8:00 AM - 12:00 PM, Wednesday
() Chemical castration, feminization, immunosuppression, growth inhibition, and developmental retardation: Identifying the culprits in pesticide mixtures.
Hayes, T1, Haeffele, C1, Phong Mai, V1, Chung, D1, Marjoua, Y1, Case, P1, Tsui, M, 1 Dept of Integrative Biology, University of California, Berkeley, CA, USA
ABSTRACT- Recent studies in our laboratory showed that atrazine both demasculinized (chemically castrated) and feminized (produced hermaphrodites and induced testicular oogenesis) in exposed amphibians at ecologically relevant doses in both the laboratory and the field. Although atrazine is a ubiquitous contaminant of ground and surface water, our studies in the wild in Nebraska revealed that amphibians are rarely exposed to atrazine alone. Using pesticide application data and water contaminant analysis as a basis, we examined the effects of pesticide mixtures at ecologically relevant concentrations on amphibian growth and development in the laboratory. As many as 10 pesticides (herbicides, fungicides, and insecticides) may be applied to a single field each season. In combination, these pesticides inhibit growth and retard development. Furthermore, the magnitude of the growth inhibition and developmental retardation is correlated with the number of pesticides in the mixture, not the dose of any one pesticide. Exposed animals also suffered from thymic involution and immunosuppression resulting in increased disease susceptibility. The inhibition of growth and retardation of development associated with exposure to pesticide mixtures, appeared to enhance the effects of atrazine by increasing the exposure time to this feminizing agent/chemical castrant. Furthermore, one of the pesticides in the mixture (methoxyacetyl) appears to be responsible for the immunosuppression and similarly its effects were enhanced because of the increased exposure time associated with exposure to pesticide mixtures. Current studies seek to isolate individual chemicals in the mixtures responsible for the measured effects or to determine if the effects are due to an increase in stress hormones (corticoids) associated with exposure to pesticide mixtures. Further, analysis of field-collected animals correlates pesticide exposure with sexual abnormalities, growth, developmental malformations, and parasite loads.
Key words: pesticide, amphibian, malformation, mixture