Enantioselective effects of dinotefuran on physiological parameters in Rana nigromaculata tadpoles

Dinotefuran possesses promising prospects, but poses a threat to the health of organisms in aquatic environment. In this study, the enantioselective toxicity effects of dinotefuran on Rana nigromaculata tadpoles were investigated. Acute toxicity tests for 96 h showed that R-(−)-dinotefuran had a more significant toxic effect on tadpoles than Rac-dinotefuran, which was greater than that of S-(+)-dinotefuran. In the toxicity assays with 0.2 and 2 mg/L dinotefuran for 28 d, noticeable changes in oxidative stress induced by Rac-dinotefuran and the two enantiomers were observed. The results of the growth parameters indicated that the development of R. nigromaculata tadpoles was inhibited to a certain extent, and the order was R-(-)-dinotefuran > Rac-dinotefuran > S-(+)-dinotefuran. Furthermore, the determination of triiodothyronine (T3) and thyroxine (T4), and the expression levels of corresponding genes (dio2, dio3, trα and trβ), demonstrated that R-(-)-dinotefuran and Rac-dinotefuran caused endocrine disruption of the thyroid system and delayed the development and metamorphosis of tadpoles, but S-(+)-dinotefuran had little effect, which was basically consistent with the results of acute toxicity and growth parameter assays. The results provide a new theoretical basis for assessing the environmental risk posed by chiral pesticides to aquatic nontargeted organisms.