The Effect Of Artemisia Argyi Essential Oil To Aedes Albopictus And Its Vitellogenesis

The mosquito,Aedes albopictus Skuse（Diptera:Culicidae） is one of the important intermediary agents who spreads various infectious diseases such as dengue fever and dengue haemorrhagic fever.Artemisia argyi Levl.et Vant（Compositae:Artemisia） is one kind of perennial herb,the essential oil of A.argyi has strong bactericidal and insecticidal effect to insect,but low toxicity to human and livestock,so it is one kind of cheap natural insecticidal plant.In this study,the repellent activity and toxicity of A.argyi oil to A. albopictus,Tribolium castaneum and Sitophilus zeamaisewere studied.Also,its effect on egg laying,ovary development,vitellogenesis and enzymes of adults of A.albopictus were analysed,for the purpose of providing theoretical principle and basis for pest controlling and exploring the mechanism of A.argyi oil on vitellogenesis of A.albopictus. The results were as follows:1.The effect of A.argyi to insects such as A.albopictusThe action modes of A.argyi oil to insect were fumigant,contact toxicity,repellent and ovicidal activity,and the action is selective to different kinds of insect.A.argyi oil expressed high fumigant toxicity to many kinds of insects.The LC₅₀ values（0.5h,1h and 4h） to adult of A.albopictus were 0.69,0.59 and 0.47μL/L;the lethality rates（96h） of adults of T.castaneum and S.zeamaise treated with 40μL were 100%and 76.3%.Also,the LD₅₀ values of A.argyi oil against adults and larvae of A.albopictus were 67.6 and 45.4μg/mL;the LD₅₀ values were 24.1 and 39.8μg/mL to adults of T.castaneum and S.zeamaise.It was also repellent to the adults of A.albopictus,the longest protection time was 5.2h;T.castaneum was more susceptible than S.zeamaise based on the repellency effect.A.argyi oil had the strong ovicidal activity;all the treatments were significantly different compared with the control.The number of egg laying by A.albopictus was reduced treated with LC₁₀ and LC₁₅,and the hatchability was inhibited treated with LC₁₅ significantly different compared with that of the control.2.The effect of A.argyi essential oil to the ovary development of A.albopictusA.argyi oil treatment had no obvious effect on eggs and oocytes development;Both the control group and treatment group experienced a steady growth in earlier stage and a rapid growth in later stage until stability,there was no significant difference between control groups and treated groups on the lengths of the egg and oocyte in each developmental stage.The yolk protein in the oocytes in controls and treatments experienced a rapid growth in earlier stage and a steady growth in later stage until stability,what is the difference is the proportion of yolk protein in the oocytes in treatments was significantly lower than that of the control during 3h to 33 h period ot time after blood-sucking;there was no significant difference in other developmental stages. Compared the microstructure of ovarian development characteristics of A.albopictus of control group with that of treated group,we found that there has large lipid droplets in the oocytes in treatments in earlier developmental stage where the control did not exist;we also found in the control group,the deposition of yolk protein began at 6h after blood meal,whereas the treatment group began at 12h;in the control group,the vitelline membrane formed at 36h after blood meal,whereas at 48h in the treatment group;we also found in the control,the chorion was formed at 72h after blood-sucking,whereas it was not observed in the treatment.The effect on the ultrastructure of A.albopictus ovarian eggs after treated with A.argyi oil was:the heterochromatin in the oocyte nucleus was in irregular shape;follicular cell arranged loose and the opening space increased abnormally; the yolk granules lost its original circle shaped or oval,was in irregular shape in the oocytes;the vitelline membrane was formed by muti-layer of granules,which arranged not closely;there were nurse cells in the egg,which characterized by losing the original form,losing materials and cytoplasm dissolution and so on.3.The purification of yolk protein of A.albopictus and analysis of tissue localizationGel filtration chromatography and ion-exchange chromatography were used to purify the vitellin of A.albopictus.SDS-PAGE analysis showed that the vitellin was composed of two subsuits,the large one 220 KDa and the small one 66 KDa.Western-blotting results showed that both of these two subunits acted specific reaction with polyclonal antibody,however,has no action with the homogenate of male.SDS-PAGE and corresponding Western-blotting anasysis showed the two subsuits existed in the fat body and hemolymph of female that has sucked blood for 48 h and its egg extract,but not in hemolymph of male of A.albopictus. 4.The effect of A.argyi essential oil to the vitellogenesisA polyclonal antiserum against vitellin of A.albopictus was prepared in male rabbits, and the titer reached 1:12 800.We found the heavy chain and light chain of the polyclonal antibody were 67.9KDa and 43.5KDa,respectively.Detected through ELISA, we found that the Vg/Vt development trend in fat body,hemolymph and ovarian in treatment had not been impact when compared with the control.The results showed that in the control group,the Vg content in the fat body achieved peak at 24h after blood-sucking,while the peak appeared at 36h in the treatment group,whereas the two peaks content were significantly defferent;the Vg content peak appeared at 24h after blood-sucking in the control while at 36h in the treatment,and there was no significant difference between them;in the control group,the peak of Vt content was occurred at 24h after blood-sucking while the time was postponed until 48h in the treated group,but no difference between them.5.The effect of A.argyi essential oil to the enzyme system of A.albopictusThe results showed that after treated with the A.argyi oil,the activity of GST was significantly activated;the activity of GST increased 91%、87%and 44%at 36h,48h and 72h respectively more than that of control,while there was no significant difference at the earlier stage（12h and 24h）.A.argyi oil treatment had a strong inhibitory effect on the activities of ACP and Na⁺-K⁺-ATP,while there were significant differences between all the treatments and that of the related control.The activity of AKP reduced on the first （12h and 24h）,then enhanced（36h and 48h）,and then inhibited at 72h after blood feeding after treated with A.argyi oil.