Effect Of Cadmium On Metamorphosis Of The Bufo Gargarizans

Cadmium is low in nature,widely distributed and often exists in the state of compounds,and has strong toxicity.However,with the rapid development of industrialization,human unreasonable activities such as smelting,sewage irrigation,pesticides and fertilizers lead to water and soil.The cadmium content is getting higher and higher,and it has become one of the main heavy metal pollutants.High concentration of cadmium can cause damage to living tissues and organs,and damage the various systems of the body.The bufo gargarizans tadpoles is an important biological monitoring species in the aquatic ecological environment.One of the larvae is sensitive to natural environment changes and chemical pollutants during development.Therefore,the toxicological effects of heavy metal cadmium on amphibians were investigated by the toxicity test of bufo gargarizans tadpoles under cadmium stress.In this study,the acute toxicity of Cd²⁺to bufo gargarizans tadpoles was studied.The tadpoles was exposed to different cadmium concentrations,and the deaths of tadpoles at 24h,48h,72h,and 96h were recorded.The LC₅₀,LC₁₀₀and Regression equation were calculated.Secondly,in order to explore the chronic toxicity of Cd²⁺tobufo gargarizans tadpoles,whether it affects the growth and development of tadpoles,we exposed tadpoles to 0.05mg/l,0.2mg/l,0.4mg/l,0.6mg/l,0.8mg/l,until complete metamorphosis,recording of tadpole development duration,and the overall length and weight measurement and antioxidant Enzymes of tadpole different developmental stages,results were as follows:1.Acute toxicity test of different concentrations of cadmium in bufo gargarizans tadpoles,24h,48h,72h,96h.The LC₅₀ concentrations were 4.684 mg/L,3.001 mg/L,2.528mg/L,2.210 mg/L,and LC₁₀₀ were 10.049 mg/L,5.413 mg/L,3.454 mg/L,and 1.969 mg/L,respectively.After 24 hours of cadmium exposure,we found that the larval mortality rate was as high as 100%when the cadmium concentration was 8 mg/L,and the tadpoles mortality increased with the increase of cadmium concentration and exposure time.2.The reaction of bufo gargarizans cadmium poisoning showed that the secretion of mucus in the body surface in the high concentration group was more and more.The more the yellow-brown secretions in the glass jar precipitated,the slower the tadpoles reaction,and when tadpoles swim,the body can't maintain balance,and there are phenomena such as suspension and side lying.After a period of time,most of the tadpoles remain at the bottom of the container,and the viscera is seriously poisoned.Overflow,the tail is curved when dead and the color of the corpse is gray and shiny,the entire body is covered by a layer of mucous membranes,the tail is stuck by secretions,and the caudal fin edges are transparent.3.The chronic toxicity test of bufo gargarizans tadpoles showed that the growth rate of cadmium treatment group decreased with the increase of cadmium concentration.There was no significant difference between the 0.05 mg/l and 0.2 mg/l treatment groups(p>0.05).The average full-length and average body weight growth rates of the 0.6 mg/l and 0.8 mg/l treatment groups were compared with the control group.The difference was significant(p<0.05).With the increase of cadmium concentration at the same exposure time,the growth rate of average full-length and the weight of bufo gargarizans tadpoles also decreased.It shows that the long-term exposure to cadmium safe concentration can still inhibit the growth and development of bufo gargarizans tadpoles.4.After 18 days of treatment with Cd²⁺,the average length and average body weight of the bufo gargarizans tadpoles in the treatment group were not significantly different from those in the normal group(p>0.05).When the tadpoles was exposed for 30 days,compared with the normal group,The total length and body weight of the cadmium-treated group at 0.6mg/L and 0.8 mg/L were significantly different(P<0.05),indicating that the long-term exposure to cadmium solution inhibited the growth and development of bufo gargarizans tadpoles.5.The effect of cadmium treatment on the development of bufo gargarizans tadpoles was studied.The results showed that the cadmium treatment group had a certain delay compared with the control group.Compared with the control group,the high concentration cadmium solution 0.8mg/l was significantly delayed(p<0.05),and with the increase of cadmium concentration,the time of metamorphosis of bufo gargarizans tadpoles was also prolonged,causing the growth and development of tadpoles to be inhibited.6.In the chronic cadmium stress test,the activity of ACh E in tadpoles was inhibited,and it showed a sustained low activity during cadmium exposure.Cadmium significantly induced SOD activity in tadpoles,0.6 mg/l,0.8 mg.The/l cadmium treatment group was significantly different from the control group(p<0.05).The activity of GSH-Px in the liver increased firstly with the increase of cadmium concentration,then decreased,showing a significant change trend.The changes of these indicators To some extent,the situation reflects the damage and toxicity of heavy metal cadmium to bufo gargarizans tadpoles.In summary,heavy metal cadmium has a serious harmful effect on the growth and development of bufo gargarizans.The main manifestation is that the survival rate of tadpoles is reduced,affecting the growth and development of larvae,delaying the metamorphosis,and causing certain damage to the antioxidant enzymes in the tadpoles.