Developmental toxicity of bifenthrin in embryo-larval stages of zebrafish

Bifenthrin (BF) is widely used as a miticide in orchards, nurseries and homes due to its great photostability and insecticidal activity. Recently, extensive research has been conducted on the toxicity of BF in in vitro and in vivo assays. However, no data is so far available regarding the developmental toxicity of BF to fish in early life stages. In this study, the developmental effects of BF were evaluated in embryo-larval zebrafish. At specified stages (24, 48, 72, and 96 hpf), spontaneous movement, survival and hatching as well as non-lethal malformation like curved body axis or edema were described in detail. No significant lethal effects of the treatment group compared to the control occurred except for the highest concentration group exposed for 96 h. The hatching process was accelerated by BF in a concentration-dependent way, correlated with increasing spontaneous movement. Developmental abnormalities were observed for the test compound with 96-h EC50 of 256 μg L−1 for pericardial edema, and 109 μg L−1 for curved body axis. Results from locomotor assays showed that zebrafish larvae of 96 hpf exhibited impaired swimming behaviour after exposure to 50, 100, and 200 μg L−1 from 3 to 84 hpf. After being cultured in the BF-free embryo medium for one more day till 120 hpf, larvae from the 50 μg L−1group seemed to have recovered and showed no difference in the swimming behaviour compared to the control while animals of the two higher concentration groups were exhausted and swam in significantly lower speed. Furthermore, reverse transcription real-time PCR results showed that vitellogenin I expressions were significantly induced in larval zebrafish exposed to 150 μg L−1 BF for 72 h, indicating the disruption of the endocrine level. In summary, our studies showed that BF was developmentally toxic to zebrafish in early life stage after short-term exposure to sublethal concentrations and had the ability to impair the individual behaviours which are of great importance in the assessment of their ecological fitness.