The Effect Of Several Heavy Metals On The Toxicity Of Bursaphelenchus Xylophilus

Nematodes have been demonstrated very sensitive to heavy metals, therefore, they can be used as biological indicators. In the present study, the effects of three heavy metals (Cu, Pb, Cr) on toxicity of pine wood nematode, Bursaphelenchus xylophilus, were observed and analyzed. The main results are as follows.1. The effects of several heavy metals on the mortality of B. xylophilusThe mortality of B. xylophilus were observed and analyzed after exposed on three heavy metals for different metal concentrations and different times at 40C, respectively.The result showed highest mortality was observed after nematodes exposed on Cu. 90% of nematodes died after treatment for 108 h at different concentrations of copper solution. More mortality were recorded following the increasing the concentrations of metal and extending the time of treatment, indicating the Cu has strong toxicity to B. xylophilus. However, the mortality of nematodes was not very high after treated by Cu for 1 h, and no significance were observed for the groups with treatment of 0.40 mg/L and 0.50 mg/L copper solution comparing to the control(p>0.05). The mortality of B. xylophilus treated by Pb significant lower than that of copper, but higher mortality of nematodes treated by Pb for 1 h was observed, more than 6% mortality were recorded for all treated group, and mortality of all treated group are very significant (P<0.01) comparing the control group. The mortality increasing slowly from 1 hour to 4 days, then increasing distinctly from 5 to 10 days only in the groups treated by 0.83mg/L,1.66mg/L and 3.31mg/L Pb solution, but highest mortality is lower than 20%. This indicating the toxicity of Pb is lower than that of Cu, but the sensitivity of Pb is higher than that of Cu. The lowest mortality of B. xylophilus were recorded after treated by Cr, the mortality of nematodes treated by Cr for 1 day is not significant comparing to the control,indicating the sensitivity of nematodes to Cr is lowest. Moreover, no distinct increase of mortality was recorded treated by Cr from 1 to 10 days. The highest mortality of nematodes treated by largest solution (26 mg/L) of Cr is lower than 7%, and the significance of mortality only found in part of treatment group comparing to the control, which indicated Cr has lowest toxicity to the nematodes.As mentioned above, the toxicity of three heavy metals to the nematodes are Cu>Pb> Cr, but Pb is more sensitive than the others. The result of the present study is different from the report previously which used C. elegans as research animal. The reasons are possibly because different species of nematodes have different sensitivity to heavy metals or different conditions were used in the experiments.2. The soluble protein analysis of B. xylophilus after treated by heavy metals by SDS-PAGEThe soluble proteins of B. xylophilus were analyzed by SDS-PAGE after treated by different solution of three heavy metals for different times (12 h, 24 h, 36 h and 48 h for Cu whereas 12 h, 24 h, 36 h, 48 h and 60 h for Pb and Cr).The result showed no distinct difference was observed in all treated groups. The protein bands of SDS-PAGE of treated groups are consistent to that of the control group, illustrating sensitivity of SDS-PAGE is not good enough. The more sensitive methods will be selected in the further research.