Reproductive And Physiological Responses Of A Biocontrol Agent Of Common Ragweed, Ophraella Communa Lesage(Coleoptera:Chrysomelidae) To Abnormal High Temperature

Ophraella communa, a ragweed leaf beetle, is the host-specific natural enemy of the invasive ragweed, Ambrosia artemisiifolia. Previous study showed that laboratory rearing temperature of36℃affected adversely its development and reproduction. Based on abnormal high temperature changes in summer months in Hunan provinces, the3hours-heat-shock treatements of different stages of O. communa at temperature of40,42,44℃for continuous3-5days and were conducted, and the continuous high temperature treatments of a complete generation of of O. communa were also run at the above temperatures in order to test the heat-tolerance of the beetle,the reproduction, physiological metabolites and protective enzymes activity. The results as follows:1The effect of abnormal high temperature stresses on the development and reproduction of O. communaThe survival rates of O. communa decreased with the increasing temperature when the different stages of O. communa were stressed by abnormal high temperatures. Egg and larva can suffer the high temperature stress of40℃, and the survival rates of pupae and adult were higher at all temperatures. Capability of tolerance to high temperature was adults> pupae> larvae> eggs. The survival of O. communa was significantly affected by continuous high temperature stress of a generation. Female ratio was significantly higher under high temperature stress. Except for40℃, abnormal high temperature stress was significantly lower female fecundity, and high temperature stress had a significant cumulative effect. The adult longevity was significantly extended when the different stages were stressed by abnormal high temperatures. The adult longevity would be extended when the generations were stressed by abnormal constant high temperatures, but when the temperature reached44℃, the adult longevity would be shorten.2The effect of abnormal high temperature stresses on the body characteristic parameters of O. communaThe growth of the adult O. communa body length could be significantly inhibited by segmental (different stages) and continuous (a generation) abnormal high temperature stresses, and the effect of continuous (a generation) abnormal high temperature stress was more significant. The lost adult weight was not obvious when the different stages were stressed by abnormal high temperatures. When the generation were stressed by abnormal high temperatures the lost adult weight was significant. It showed that the cumulative effect of high temperature stress had a significant impact on adult body length and weight.3Physiological metabolic mechanisms of O. communa to abnormal high temperature stressesThe water, total sugar, glycogen, fat, glycerin and hydroxyl proline content of O. communa were significantly affected by abnormal high temperature stress. When the different stages of O. communa were stressed by abnormal high temperatures, the adult water content of all treated stages of O. communa was the highest at40℃, while when the eggs after being stressed, the adult water content was the highest. Generally, the female total sugar content had increased after different stages stressed by abnormal high temperatures, and which was higher than male. Male total sugar content would increase after egg and larva were stressed by high temperature, which would decrease when pupa and adult were stressed by high temperature. Both female and male total sugar content decreased as the temperature increasing, when the high temperatures continued to stress (a generation). The adult glycogen content was higher than the control, when the different stages were stressed by high temperature, and male glycogen content was higher than female. In addition to the stress of egg and larva at40℃, adult body fat content were significantly lower than the control after different stages stressed by different high temperatures. In addition to the stress of male at40℃, the adult body fat content decreased as temperature increasing after high temperature continues being stressed, and female body fat content was significantly higher than male. After the different stages of O. communa were stressed by abnormal high temperatures, the female hydroxyproline content decreased, while the male body hydroxyproline content showed an increasing trend. When the continued stressed high temperature was no less than40℃, male hydroxyproline content increased, which was significantly higher than female. The adult glycerol content was significantly increased, when different stages and a generation were stressed by abnormal high temperatures. These changes of adult physiological metabolites were a positive response of O. communa to high temperature stress.4The protective enzyme activities of O. communa changes under abnormal high temperature stressesThe adult protein content was significantly reduced after different stages of O. communa were stressed by abnormal high temperatures. After high temperature continues being stressed, the female protein content decreased, while the male protein content increased. After different stages of O. communa were stressed by abnormal high temperatures, adult body SOD activity increased, but the adult SOD activity was significantly decreased after high temperature continues being stressed. After different stages were stressed by abnormal high temperatures, adult CAT activity increased, and the adult CAT reached its peak after the larva was stressed. The female CAT activity raised at first, then decreased as the temperature increasing after high temperature continues being stressed, and reached its peak at42℃. The adult POD activity decreased after different stages of O. communa were stressed by abnormal high temperatures. After continues abnormal high temperature stressed, female POD activity decreased as the temperature increasing, and male POD activity was hardly affected. The order activity of the three enzymes was SOD> POD> CAT, the contribution rate of resistance to oxidative stress was SOD> CAT> POD, which showed that high temperature caused oxidative stress, and O. communa has the ability to resistant to oxidative stress impact caused by a temperature no more than42℃.