Hepatic retinoids of bullfrogs in relation to agricultural pesticides.

Agricultural pesticides often have been cited as a factor affecting indigenous amphibian populations, but possible effects of pesticides and other factors associated with agricultural practices are understood poorly. Adult bullfrogs (Rana catesbeiana) were collected within the Yamaska River basin (Quebec, Canada) in subwatersheds representing low, medium, and high agricultural activities and 53 pesticides were analyzed in surface water. More pesticides were detected in subwatersheds associated with high agricultural activities like Rivière Noire and Rivière à la Barbue and pesticide concentrations were higher compared to the other study sites. Female and male body weights differed between sites. In the case of males, body weight was significantly less at Rivière à la Barbue. Liver retinol stores were decreased significantly in male bullfrogs from Rivière Noire, although total retinyl esters concentrations varied between sites having the highest concentration at Yamaska-Nord where the agricultural activity was considered low. The ratio of hepatic retinyl palmitate to retinol tended to be higher for male bullfrogs from Rivière Noire and Rivière à la Barbue. These results suggest that factors associated with intensive agricultural practices may affect the body weight and retinoid stores in male bullfrogs living in these agroecosystems.