(PT192) Impacts of row crop agriculture on sexual development of anurans.
McDaniel, T.1, Martin, P.1, Marvin, C.2, McMaster, M.2, Sherry, J.2, 1 Canadian Wildlife Service, Environment Canada, Burlington, Ontario, Canada2 National Water Research Institute, Burlington, Ontario, Canada
ABSTRACT- Intensive row crop agriculture featuring corn and soybean production, is predominant in southwestern Ontario where the two crops account for over 50% of the total acreage of crops grown. This form of agriculture relies heavily on pesticide and nutrient inputs for continued success under conventional systems. The corn herbicides atrazine and metolachlor, are the two most heavily applied pesticides in Ontario and are routinely detected in tributaries draining agricultural watersheds. Field and laboratory studies have indicated exposure to atrazine may disrupt normal sexual development in male anurans, causing reductions in testosterone levels, laryngeal muscle diameter, and abnormal testes development. In addition, male cane toads exposed to field levels of atrazine expressed levels of vitellogenin equivalent to those found in female toads. Pesticide levels and water quality data was collected from farm ponds and agricultural drains in southwestern Ontario, as well as three non-agricultural reference sites in August and September, 2003 and monthly from April through August in 2004. In late summer, 2003, atrazine and metolachlor were detectable in most samples, exceeding 1 ug/L at some sites. Water quality at many agricultural sites was potentially compromised for amphibian survivorship and development due to high nutrient and metal concentrations. Blood samples were obtained from leopard and green frogs for analysis of sex hormones, vitellogenin and thyroid hormones. Gonads were excised for histomorphological assessment. Analysis of frogs from late summer 2003, revealed that circulating testosterone levels were negatively correlated with atrazine concentrations in pond water in juvenile male leopard frogs (r = 0.74; p = 0.014) and adult female leopard frogs (r = 0.59; p < 0.008). No relationships were found with metolachlor.
Key words: atrazine, amphibians, agriculture, sex hormones