Preliminary Study On Toxicity Of Copper And Cadmium On Fejervaya Cancrivora Tadpoles

Our prior experiments had found that the Fejevarya cancrivora frog could be used asindicator species for mangrove habitat quality and MDA content in tissue could be used asindicators of sensitive index. To reveal the toxic effect of heavy metals and to determineindicator characteristics, the acute toxicity and chronic toxicity experiments of copper andcadmium exposure on Fejevarya cancrivora tadpoles were done in this paper. The results willprovide a scientific foundation for biological monitoring system of water environmentalindicators taking amphibiams as biological indicator.1. LC₅₀of copper and cadmium exposuer on tadpoles of Fejervarya cancrivoraThe result of acute toxicity to tadpoles at the period of27-28（BL23.33±1.41mm, BW0.134±0.022g） showed that the24h,48h,72h,96h-LC₅₀of copper were2.75,1.89,1.42,1.10mg/l respectively, and the24h,48h,72h,96h-LC₅₀of cadmium were28.90,23.05,19.19,16.19mg/l, respectively. For the tadpoles at the period of38-39, the24h,48h,72h,96h-LC₅₀of copper were5.69,3.37,1.34,0.95mg/l, and the24h,48h,72h,96h-LC₅₀of cadmium were53.96,43.24,38.63,25.89mg/l. LC₅₀of copper was greater than that of cadmium, whichsuggested that tadpoles were more sensitive to copper than cadmium. And the results showed96h-LC₅₀of cadmium to the period38-39tadpole （25.89mg/l） was higher than that of period27-28（16.19mg/l）, which illustrated that with the tadpole developed, the tolerance tocadmium also increased.2. Acute toxicity of copper, cadmium to the Fejervarya cancrivora tadpolesBased on the96h-LC₅₀, four treatments of copper （control,80,160,300ug/l） and fourtreatments of cadmium （control,5,7,13mg/l） were designed and sampled at24h,48h,72hand96h. And the effects of acute copper and cadmium exposure on the superoxide dismutase（SOD） activities, acetylcholinesterase（AChE） activities, MDA content and metallothioneincontent, nuclear anomalies rates and erythrocyte micronucleus rates in tadpoles werediscussed.The result showed that SOD and AChE activities could be induced after exposed on lowconcentration （5mg/l） of cadium, SOD activities reached the maximum value after24hexposure, AChE enzyme activity reached maximum after48h exposure. But with the exposure concentration increased and treatment time prolonged the enzyme activitiesdecreased, which suggested enzyme activity were inhibited after exposed in cadmium for longtime and high concentrations. SOD and AChE activities of treatment groups were lower thanthe control groups when expose on copper for24h, and the content of MDA increasedsignificantly. The higher the exposured concentration and the longer exposured time, the moreMDA content, which suggested that the lipid peroxidation increased under copper, cadmiumstress. And metallothionein （MT） content decreased and erythrocyte micronucleus rateincreased significantly with time elapsed and exposure concentration increased.3. Chronic toxicity of copper, cadmium to the Fejervarya cancrivora tadpolesBased on the96h-LC50, four threaments of copper （control,10,15,20ug/l） and fourthreaments of cadmium （control,450,560,630ug/l） were designed and sampled at7d,14d,21d. And the effects of copper and cadmium on the development of tadpoles, enzymes activity,MDA content and liver histological structure of tadpole were discussed.The results showed that, body length, body weight on treatment group were significantlylower than those in the control group. And in a certain time, the higher the exposureconcentration, the shorter the tadpole body length and the lighter the weight, which indicatedthat growth and development of tadpoles was inhibited after copper or cadmium exposure.SOD and AChE activities of treatment groups were lower than the control, suggested theactivities of SOD and AChE were inhibited. MDA content increased with the exposureconcentration and exposure time increasing. In the same exposure time, MDA content intreatment group were higher than the control. After21d exposure, MDA content reached themaximum value which about3times higer than control at the highest concentration （630ug/l）of cadmium and copper （20ug/l）.After21d exposed to copper and cadmium, the liver suffered serious damage, such asliver structure was not complete, the melanin increased, blood vessels were damaged andhepatolysis. And with exposed concentration increase, liver cytoplasm loose and tissuedissolved range increases.