Abstract:

Avermectins is considered one of the most commonly used pesticides in China and probably the world. Studies on avermectins acute toxicity to Cyprinus carpio and effects of low level avermectins on serum estradiol contents in male Cyprinus carpio at different effecting time and exposure concentrations were done. Results of toxicity test showed that 24 h, 48 h ,72 h and 96 h LC50 values were 134.12μg?L-1，60.55μg?L-1 ,45.31μg?L-1and 33.50μg?L-1 respectively. The safety concentration of avermectin to Cyprinus carpio was 3.35μg?L-1, therefore it was virulent toxic to fish. Under effecting time of 20 days, the synthesis of serum estradiol in male C. carpio was inhibited by avermectin at the lower concentrations ranging from 3.2 to 5.6μg?L-1. The most strongest inhibiting effect happened when the avermectin concentration was 5.6μg?L-1, and the content of serum estradiol reduced by 28.8% compared to the control group. However, the synthesis of serum estradiol had no obvious difference at higher concentrations of 10.0μg?L-1and 18.0μg?L-1. The contents of serum estradiol in male C. carpio were lower than the control group at all effecting time at the concentration of 5.6μg?L-1, and on the 20th day the serum estradiol content showed the lowest value by induced 28.8% compared to the control one. And there was no significant time-response or dose-response relationships between serum estradiol contents in male C. carpio and the effecting time or exposure concentrations of averectin. It is suggested that low level avermectins could induce depressions of serum estradiol in fish,thus threatening reproduction of fish.