Triazophos exposure on maternal Daphnia magna at environmental-related concentrations revealed toxic effects to its offspring

Due to chemical and photochemical stability, triazophos has been frequently detected in rivers and oceans over the years with extensive use for pest control in agriculture, and it has become a worldwide ecological concern to the aquatic environment. Until now, fewer data are available regarding the potential long-term adverse effects of triazophos on aquatic invertebrates, which plays an essential role in aquatic food webs, as a key group for water ecosystems. In this experiment, the F1- and F2 progenies of Daphnia magna were recovered when daphnias (F0) exposure to triazophos at environmental-related concentrations (0.1 and 1.0 μg/L) for 21 d; and the indexes related to phenotypic traits, reproduction and gene expression were measured in tested animals. The results showed that heart rate and total number of neonates in exposed F0-daphnias were significantly lower than those of control group, and the detoxification genes (HR96 and P-gp) were up-regulated while genes related reproduction (Vtg) and molting (Nvd and Shd) were significantly down-regulated. The heart rate and individual size of F1-daphnias (<24 h) were significantly reduced in the treatment group. After 21-d recovery, the heart rate and expression of HR96, P-gp, Vtg, Nvd and Shd were declined in F1-daphnias. There was no obvious difference of morphological traits and heart rate between treatment and control in F2-daphnias (<24 h). In summary, daphnias (F0) exposure to triazophos with environmental dose could raise toxic effects on its offspring (F1), which is mainly manifested by reduced heart rate, the accumulated number and individual size of offspring and decreased expression of genes related to molting and reproduction.