Toxicity assessments with Daphnia magna of Guadipyr, a new neonicotinoid insecticide and studies of its effect on acetylcholinesterase (AChE), glutathione S-transferase (GST), catalase (CAT) and chitobiase activities

• Acute and chronic toxicity of guadipyr, a novel neonicotinoid insecticide, on Daphnia magna was studied.
• Activities of AChE and GST, but not CAT can used as early, sensitive biomarker for guadipyr exposure.
• Chitobiase activity in test media can potentially predict the effects of toxins on D. magna.

Guadipyr is a novel neonicotinoid insecticide, developed by the China Agricultural University. This work investigated its aquatic toxicity on Daphnia magna. The acute immobilization test showed that guadipyr was slightly toxic to daphnids, with a 48 h EC50 of 13.01 mg/L. In addition, guadipyr significantly enhanced the acetylcholinesterase (AChE) and glutathione S-transferase (GST) activity (per gram of protein), but had no obvious impact on catalase (CAT) activity within 48 h. The 21 d chronic exposure of D. magna to guadipyr induced a significant decrease in body growth and reproduction; both share the same lowest observed effect concentration (LOEC) at 0.10 mg/L. In the 14 d chronic test, a significant increase in chitobiase activity in test media was observed at day 8 (days to the first breeding), while a significant decrease was observed from days 10 to 14, which might be due to the endocrine imbalance resulting from guadipyr stress. These results demonstrated that guadipyr can induce notable negative ecotoxicological impacts on the aquatic system in long-term exposure at a sub-lethal dose. Further research in environmental behaviors is needed to regulate guadipyr use in the future.