Two PBDEs exposure inducing feeding depression and disorder of digestive and antioxidative system of Daphnia magna.

2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) are two typical polybrominated diphenyl ethers (PBDEs), and studies have proven that these PBDs can disrupt the behaviors and physical function of aquatic organisms. However, little is known about the compositional impacts of BDE-47/BDE-99 compound pollution on the feeding behavior of Daphnia magna. In this study, a response surface methodology (RSM) was introduced into the combined toxicity assessment of BDE-47 and BDE-99 on the feeding depression of D. magna. Low concentrations of BDE-47 (9.2 μg/L) and BDE-99 (5.4 μg/L) had no effect on the feeding behavior of D. magna; nevertheless, the feeding depression was strengthened, and a concentration-dependent effect was observed with increasing concentrations of BDE-47 and BDE-99. The results of RSM indicated that the mixture of BDE-47 and BDE-99 can enhance their toxicity on the feeding behavior of D. magna. Moreover, real-time PCR (qPCR) analysis showed that the down-regulation of α-amylase (AMS) appeared in most of the exposed D. magna. However, there were significant different in the gene expression of trypsin, superoxide dismutase (SOD) and catalase (CAT) between the exposure and control groups. The change in the enzyme activity of AMS, trypsin, SOD and CAT implied that BDE-47 and BDE-99 cause damage to the digestive and antioxidative systems of D. magna. Correlation analysis indicated that a significant positive correlation existed between the gene expression and enzyme activity of SOD and CAT. Our results contribute to the understanding of toxicity caused by BDE-47/BDE-99 compound pollution in D. magna and help to improve traditional toxicity assessment methods for aquatic environments.