The Study Of Toxic Effect Of Dichlorvos And Butachlor On Polypedates Megacephalus Tadpoles

the tadpoles which were at Gosner-stage 37-38 was 11.6304 mg/l, the 96-h LC50 for Butachlor to the tadpoles which were at Gosner-stage 28-29 was 102.847×10-2 mg/l, the 96-h LC₅0 for Butachlor to the tadpoles which were at Gosner-stage 37-38 was 1.689 mg/1.2.In the subacute toxicity experiment, control group and five DDVP treated groups (0.52×10^-4 mg/l,1.04×10^-4 mg/l,5.2×10^-4 mg/l,10.4×10^-4 mg/l, 52×10^-4 mg/l) were set to treat the tadpoles which were at Gosner-stage 28-29, after 30d exposure the results showed that: (1) The gonadic histology structure and hepatic ultrastructure of the tadpoles appeared significant transformation. Applying the light microscope, immature epithelium proliferation was observed in ovary and there were many degenerative auxocytes and oogoniums. It may be the primary stage of intersex.Applying the electron microscope , the phenomena of mitochondria decreasing, glycogen and lipid drops accumulating in hepatocytes were observed when tadpoles exposed to 52×10^-4 mg/l DDVP.(2) Compared with the control group, the gonadic and renal volume shrunk obviously, the gonadic and renal volume decreased 25.85% and 33.01% respectively when tadpoles exposed to 5.2×10^-4 mg/l DDVP.(3) Daily increase rate was affected. Compared with the control group, the daily increase rate body length and weight decreased 42.63 % and 63.64% when exposed to 0.52×10^-4 mg/l DDVP from 20d to 30d.3. In the physiology toxicity experiment, control group, five DDVP treated groups (2.08 mg/l, 4.16mg/l, 6.24 mg/l, 8.32 mg/l, 10.40 mg/l) and five Butachlor treated groups (0.1025mg/K 0.205 mg/K 0.410 mg/K 0.820 mg/K 1.230 mg/1) were set to treat the tadpoles at Gosner-stage 37-38. Then the activities of SOD and AChE of the tadpoles at 24h, 48h, 72h and 96h were measured. Iso-enzymes were analyzed by means of PAGE. The results showed that: (1) in lower concentration treatment, the activities of SOD did not change significantly in a short time, but along with the time the activities of SOD increased, in higher concentration treatment the activities of SOD were inhibited, the inhibition would increase with the time protracting and the concentration increasing.(2) The detected activities of AChE indicated that: the activities of AChE decreased with the concentration increasing in the same time, the inhibition rate increased gradually.(3) The results of PAGE indicated that: DDVP and Butachlor could affect the iso-enzymes of EST> LDH and SOD, it appeared in the decreasing of enzyme activity and the disappearing of enzyme bands.4. In the genetic toxicity experiment, the same concentrations in the physiology toxicity experiment were used to detect the DNA damage and induce micronucleus. The results indicated that: exposure to different concentrations of DDVP for 24h, an increased incidence of cells with increased DNA damage was observed in the tadpoles exposed to increasing concentrations of the solution. Similarly, tadpoles exposed to the positive control (MMS) also exhibited a significant increase (P0.05) in the mean DNA length-to-width ratio relative to that of the negative control. Tadpoles exposed to higher concentrations (0.82 mg/k 1.23 mg/1) of herbicide Butachlor and positive control (MMS), however, showed a highly significant increase (PO.01) in DNA damage compared with that of the negative control.(2) The results of inducing micronucleus indicated that: the appearance of micronuclei frequencies and irregular nucleus frequencies peak value did not positively correlated with treated concentrations. When it reached peak value, with the concentration increasing, micronuclei frequencies and irregular nucleus frequencies didn't increase, even decreased.DDVP and Butachlor poisoning the tadpoles in different ways, such as acute toxicity, sub-acute toxicity, physiology toxicity and genetic toxicity. In agriculture, there should avoid using these pesticides to protect amphibian. Amphibian itself has many advantages, those made it suitable for monitoring water pollution as bio-indicator.