Life history and biochemical effects of chlorantraniliprole on Chironomus riparius

The need to overcome pesticide resistance has led to the development of novel insecticides such as chlorantraniliprole (CAP), an anthranilic diamide. CAP disrupts calcium homeostasis in nerve and muscle cells and is used in several agricultural crops due to its potency and selectivity. However, chronic toxicity data for aquatic invertebrates are limited. Our objective was to evaluate the toxicity of CAP at different levels of biological organization using Chironomus riparius. Organismal endpoints (survival, larval growth and emergence), and 5 biomarkers associated with important physiological functions (acetylcholinesterase - AChE; catalase - CAT; glutathione-S-transferase - GST; total glutathione - TG; and lipid peroxidation - LPO) were investigated. Effects of CAP on cellular energy allocation (CEA) were also assessed. Acute tests revealed a 48 h LC50 for C. riparius of 77.5 μg/L and life-cycle tests revealed a chronic LOEC of 3.1 μg/L based on effects on C. riparius larval growth and emergence. C. riparius females exposed as larvae to low concentrations of CAP emerged at a smaller size which might also translate into effects on reproduction. Chironomid larvae were not under oxidative stress, since short exposures to CAP did not affect LPO levels, despite the significant inhibition of GST (0.6-9.6 μg/L) and CAT (9.6 μg/L). It seems that detoxification of reactive intermediates and ROS is still achieved due to glutathione consumption, since TG levels were significantly decreased in organisms exposed to CAP (0.6-9.6 μg/L). Moreover, it was observed that CEA was disturbed due to increased activity of the electron transport system (ETS), suggesting extra energy expenditure in larvae. These results show that environmental concentrations of CAP can impair the fitness of C. riparius natural populations and at the same time that chironomids, as for most insecticides, are suitable test organisms to evaluate the organismal and biochemical effects of anthranilic diamides.