Joint toxicity effects of azoxystrobin and three kinds of exogenous selenium on zebrafish during different life stages

In this work, the single acute toxicity of azoxystrobin and three kinds of exogenous selenium (sodium selenite, selenomethionine and nano-selenium), and joint acute toxicity of binary mixtures in equitoxicity ratios on zebrafish (Danio rerio) during different life stages were determined, and additive index (AI) method, toxicity unit (TU) method, and mixture toxicity index (MTI) method were adopted to evaluate the joint toxicity effects, respectively. These results showed that the sensitivity of three life stages to sodium selenite (expressed as 96 h-LC₅₀ (lethal concentration) mg/L, mg is the mass of selenium) were as followed: larvae (1.11 mg/L)>embryo (1.48 mg/L)>adult zabrafish (13.05 mg/L); the sensitivity to selenomethionine were as followed: larvae (0.80 mg/L)>embryo (1.03 mg/L)>adult zabrafish (9.36 mg/L); the sensitivity to nano-selenium were as followed: adult zabrafish (0.48 mg/L)>larvae (1.67 mg/L)>embryo (4.32 mg/L). The consistent conclusion that could be drawn from three methods (AI, TU and MTI) was that the joint toxicity effects of azoxystrobin and three kinds of exogenous selenium (sodium selenite, selenomethionine and nano-selenium) on zebrafish during different life stages (embryo, larvae and adult zabrafish) were antagonistic, except for, the joint toxicity effects of azoxystrobin and selenomethionine on adult zebrafish were partially additive by MTI method.