Developmental toxicity of formulated insecticide mixture containing imidacloprid and beta-cyfluthrin in fish:...

Insecticides are critical in controlling pests and disease vectors. However, there is still a lack of ecotoxicological studies using commercial formulations of insecticides containing active ingredients. The study aimed to evaluate the developmental toxicity of a commercial insecticide mixture (imidacloprid [IMI] + beta-cyfluthrin [β-CYF]). Mortality, hatching rate, spontaneous contraction, heartbeat, morphological changes, reactive oxygen species (ROS), skeletal development, and locomotor behavior of zebrafish were analyzed. Embryos were exposed to imidacloprid (IMI) and β-cyfluthrin (β-CYF) in the following ratios: 0.001 mg IMI·L^-1 + 0.000125 mg β-CYF·L^-1 (C1); 0.01 mg IMI·L^-1 + 0.00125 mg β-CYF·L^-1 (C2); 0.1 mg IMI·L^-1 + 0.0125 mg β-CYF·L^-1 (C3); 1.0 mg IMI·L^-1 + 0.125 mg β-CYF·L^-1 (C4); 10.0 mg IMI·L^-1 + 1.25 mg β-CYF·L^-1 (C5) for 144 h. The results showed a mortality of 50 % of organisms in the C5 concentration. Embryos exposed to C1 and C3 showed tachycardia and hatched early compared to the negative control, indicating cardiotoxic and embryotoxic effects. The two highest concentrations tested (C4 and C5) induced evident morphological changes (yolk sac and pericardial edema, and spine alterations), and skeletal toxicity (absence of cartilage and bone formation), along with decreased larval swimming behavior. Also, the formulated insecticide (C1) increased ROS levels in zebrafish larvae. Results showed that the formulated insecticide containing IMI and β-CYF induces several toxic effects on developing zebrafish, indicating its environmental risk to aquatic organisms.