Preliminary Study On Toxicity Of Lead And Mercury On Bufo Raddei Tadpoles

As a common amphibians, Bufo raddei is a strong resistance of frogs,that is widely distributed.It has strong ability of environmental relevance and strong sensitivity of change in the environment. Previous studies indicate that it can be used as the evaluation of the merits of the aquatic environment quality indicator species and the content of MDA in tissue can be used as one of the more sensitive evaluation.To reveal the poisons effects of heavy metals and find out the indicating characteristics that reflect on environmental stress, this paper studied the acute and chronic toxicity test of Bufo raddei tadpoles exposed indoor dirt.To a certain extent,the results reflect that, lead,mercury and toxic have an effect on Bufo raddei tadpoles and biological monitoring system provides a scientific basis.In this study, the following is obtained:1. LC50 of lead and mercury exposuer on tadpoles of Bufo raddeistudy of concentration of Bufo raddei tadpoles' median lethal caused by lead,mercury 96 h toxicity test results show that,contamination of Bufo raddei tadpoles 26-30(BL19.0±0.024 mm,BW: 0.088±0.012g). Results of LC50 by lead in 24h?48h?72h?96h are 4.370?2.511?1.514?1.135mg/l, 0.841?0.607?0.474?0.361mg/l by mercury.Thus,the median lethal concentration of mercury is much higher than the median lethal concentration of lead in the same period, indicating that mercury on tadpoles of Bufo raddei toxicity greater than lead.In the study of lead, mercury toxicity joint: When the mercury ions and lead ions coexist on tadpoles for 24 h, 48 h, 72 h, 96 h joint toxicity are synergies, and its LC50 is smaller than when there is a presence of a single ion,this indicates that when the mercury and lead coexist,it has a stronger toxicity on tadpoles than they exist separately.2.Test of chronic toxicity of lead, mercury on Bufo raddei tadpolesTo understand the toxic effects of long-term contamination of lead, mercury on Bufo raddei tadpoles,on the basis of the LC50 of 96 h, I chose 26-28 period(BL:14.5 ±0.08, BW: 0.063 ± 0.022)as experimental subjects, and designed four groups: 0, 5, 10,20(ug / l)mercury solution and 0, 10, 50, 100(ug / l)lead group treated with different concentrations of lead, mercury pollution in 6d, 12 d, 18 d to find out the effect on the tadpoles' growth and development, related activity in vivo lipid peroxidation productMDA and microstructure of tadpole liver.The results showed that lead, mercury pollution from the beginning of the sixth hour, tadpole body length and weight of each treatment group were significantly lower than the control group, and in a certain processing time, the shorter the length of tadpoles exposed to the higher concentration, the more light weight, this shows that in the lead, mercury contamination, growth and development of tadpoles is suppressed.In the lead, mercury exposure in 6d, 12 d, 18 d, SOD, GSH-PX activity of each treatment group was significantly lower than the control group, and in the same process as the concentrations of exposure period increased,enzyme activity decreased indicating that SOD, GSH-PX activity was inhibited, showed continued low living state.In the pollution of lead and mercury, concentration of MDA increased with the increase of the exposure concentration and exposure time.At the same exposure time period, content of MDA in treated group were significantly higher and difference of MDA content between the treatment groups reached significant level; in the first 18 days exposure, the highest lead concentrations(100ug / l) and the highest mercury exposure group(20ug / l) MDA content appeared maximum was about four times the control group.After 18 d exposed to lead and mercury, the liver suffered serious damage, such as liver structure was not complete, the melanin increased, blood vessels were damaged and hepatolysis. And with exposed concentration increase, liver cytoplasm loose and tissue dissolved range increases.Throughout the experiment result shows the changes of the Bufo raddei tadpoles of various physiological indicators under the Duress by lead and mercury. It can be reflect the situation of an environment polluted areas vividly and intuitively. Playing a warning role to the polluted environment. It provides the valuable advice and data. It is important for the environmental pollution control in the future. So the Bufo raddei can become a biological indicator in the environmental monitoring. There are great reference value in environmental monitoring and control.