Impact on Anuran Metamorphosis of Neonicotinoid and Anthranilic Diamide Insecticides

FONSECA PEÑA, SHIRLEY VIVIAN DANIELA; NATALE, GUILLERMO SEBASTIÁN; BRODEUR, JULIE CÉLINE

Louisville

Congreso; SETAC North America 44th Annual Meeting; 2023

Society of Environmental Toxicology and Chemistry

In the agricultural region of the Argentine Pampa, the neonicotinoid (NEO) and anthranilic diamides (AD) families of insecticides are widely used on numerous crops, including soybean and corn. Both families of insecticides are persistent in the environment and can reach the aquatic environment by lixiviation and runoff. The objective of the present study was to analyze the impacts on amphibian species native to the Pampa region of the commercial formulations Actara and Confidor containing the NEOs, thiamethoxam (THIA) and imidacloprid (IMI), and the commercial formulations Coragen and Fortenza containing the ADs, chlorantraniliprole (CHLO) and cyantraniliprole (CYAN). Impacts on development were examined in tadpoles of the toads Rhinella arenarum at a range of concentrations. Overall, the effects occurred mainly between stages 39 and 42. In general, NEO and AD acted differently at environmentally-relevant concentrations. In the case of NEO, exposure to THIA caused a delay in the time to metamorphosis of R. arenarum starting from the lowest concentration tested (5 µg/L), while the percentage of animals completing metamorphosis was not affected. For its part, exposure to IMI had no major effects on the development at the concentrations tested. Exposure to AD, CHLO and CYAN, altered the time to metamorphosis in a non-monotonic manner (increased or decreased depending on the concentration) and significantly reduced the percentage of animals completing metamorphosis but, in this case, the effect exhibited a linear dose-response relationship. Because most effects were triggered after the tadpoles had reached Stage 39, when metamorphosis is strictly dependent on thyroid hormones, an effect of both families of insecticides on the hypothalamic-pituitary-thyroid axis is suggested. Overall, both anthranilic diamide and neonicotinoid insecticides may impair the metamorphosis success of wild amphibians as effects were observed at low, environmentally relevant concentrations.