Toxic Effects Of Ammonia On Embryonic And Yolk-sac Stage Larvae Of Rare Minnow

Ammonia occurs naturally in unpolluted water bodies at low concentrations. However, high ammonia levels could be an indication of organic pollution such as from domestic sewage, industrial waste and fertilizer run-off.Ammonia pollution in China is very serious. Ammonia pollution in China water is very serious. It is a threat to fisheries and people's life. Meanwhile, ammonia in water bodies partly exceed the China national water standard for fisheries. The effect of ammonia to fish has been widely investigated.However,the effects of embryonic and yolk-sac stage larvae is relatively poor reported. The study choose rare minnow which is endemic to China for experimental subject. Compare to sensibility of embryos, juveniles, embryonic and yolk-sac stage larvaes to ammonia.The toxic effects of ammonia to rare minnow embryonic and yolk-sac stage larvae. The Rhbg gene expression is also investigate during embryo stages. The results are as follows:1. In semi-static toxicity bioassays, rare minnow embryos, juveniles, embryonic and yolk-sac stage larvaes were tested at 25±0.5℃. Embryos and juveniles were exposed to seven different concentration group and a control group. Embryonic and yolk-sac stage larvaes were exposed to five different concentration group and a control group. The result show that,96 h median lethal concentration(LC50) to embryo and juvenile was 103.053 mg/L and 38.779mg/L, respectively.168h median lethal concentration(LC50) to embryonic and yolk-sac stage larvae was 88.601 mg/L. The larvae is most sensitive, the embryonic and yolk-sac stage larvae was second sensitive.2. The rare minnow embryos were exposed tofive different concentrations that less than 96h median lethal concentration(LC50) until 168h. According to pre-experiment results, we choose several endpints to observe and analyze. The result show that the low doses can also lead to death, slow heart rate, arrhythmia, no functional swim bladder, body lenth and weight loss, pericardial and yolk sac edema etc. Meanwhile, we choose Rhbg gene, an ammonium transporter gene, for toxicity parameter. The aim is to investigate the Rhbg gene's expression change during embryo stages. The results of quantitative real time polymerase chain reaction (Q RT-PCR) show that the expressions of Rhbg gene which embryos exposed to 75mg/L ammonia sustained 96 h as follows:It can be detected the expression of Rhbg after hatching 24 h; At 24hpf and 48hpf, the treatment group Rhbg gene expression is higher than the control group, but there is no significant difference. However, as the embryo developing, the Rhbg gene expression effected by ammonia is significant at 72hpf. Taken together, the data suggests that Rhbg may have important functions to facilitate ammonia transport during rare minnow embryo stages.