Effect Of High Temperature Stress On Ovary Development And Vitellogenin Genes Expression Of Agasicles Hygrophila

The Agasicles hygrophila is an important natural enemy for controlling the invasive alligatorweed Alternanthera philoxeroides,and the collapse of population in summer under high temperature stress has resulted in loss of biocontrol in the the thriving period of alligatorweed.This paper focuses on the influence of high temperature on the growth of the pupae and ovary development of A.hygrophila by analyzing the eclosion and fecundity of A.hygrophila under high temperature stress.The effects of high temperature stress on the ovary development of A.hygrophila were discussed by using high temperature exposure,ovarian dissection and microphotography.The expression of Vg genes in the ovary were detected by fluorescence quantitative PCR.Key findings are present as following :(1)Clarified the adverse effect of summer heat on the pupa of A.hygrophila.The pupa of A.hygrophila were processed under high temperature in 40 ? for 2 h,then the eclosion and the fecundity were observed.Comparing with the control group,the amount of eclosion and the females fecundity decreased significantly,and all eggs could not hatch.Therefore,we speculated that the high temperature significantly influenced the pupal stage of A.hygrophila,which may explain the reason of the population sharp decline in summer.(2)By using high temperature exposure,ovary dissection,microphotography and other techniques,the effect of periodic repeats of high temperature on ovary development and oviposition were determined for the first time.Under periodically repeats of 39 ?,the ovary development and yolk deposition rate of A.hygrophila were significantly decelerated.Compared with 36 ? and 25 ? treatments,the ovarian malformation rate of 39 ? treatment reached the highest number(43.8%).This result furthermore confirmed that the periodic repeats of high temperature significantly influenced the ovary development and was not suitable for the population growth of A.hygrophila.(3)The yolk protein gene clone analysis and the fluorescent quantitative PCR was applied to analyze the expression of Vg genes in ovaries of A.hygrophila.Under 30? and 36 ? temperature treatments,the expression pattern of Vg genes were different,the high temperature treatment showed the low expression level.Under the condition of summer heat,the ovaries of A.hygrophila were damaged and the expression of Vg genes were decreased significantly.Furthermore,it resulted in fecundity decreased and failed to control of the aligatorweed.This paper explained that the mechanism of population collapse in summer(July-September)by the biological phenomenon and molecular biology.This results provided the foundation of the heat domestication of A.hygrophila and the guidance for the control of A.philoxeroides.