Assessing Toxicity of the Insecticide Thiacloprid on Chironomus riparius (Insecta: Diptera) Using Multiple End Points

Since data documentation on neonicotinic toxicity to nontarget organisms should be enhanced, we investigate the effects of thiacloprid, a novel neonicotinoid insecticide, on the sediment-dwelling nontarget insect Chironomus riparius. Further, we wanted to validate the sensitivity of end points on different biological levels and obtain the greatest amount of information regarding the effects of this compound by using a battery of several end points such as larval mortality, behavior, body weight gain, emergence rate, time of development, gender ratio, Hsp70 stress protein level, and larval mouthpart deformities after exposure at a concentration range of 0.1 to 1000 mu g/L thiacloprid. C. riparius was impacted starting at concentrations of 0.5 mu g/L, a concentration that can be considered environmentally relevant. Larval mortality, behavior, emergence, and Hsp70 protein level were sensitive indicators for the toxic effect of thiacloprid, whereas gender ratio and mouthpart morphology were not affected. In our case life-cycle end points like survival rate (LC50: 1.57 mu g/L) and emergence rate (EC50: 0.54 mu g/L) proved to be more sensitive than tested physiological end points for the neurotoxic insecticide.