Effects Of Wolbachia On Superparasitism Behavior Of Trichogramma Dendrolimi Matsumura

Superparasitism is not only an important scientific question in the study of the behavior ecology of parasitic wasps,but also closely related to the biological pests control practices such as the mass-rearing of parasitoid wasps and the effect of field application.The symbiotic bacterias of the parasitic wasps can manipulate the superparasitism of host wasps,and the symbiotic bacterias can horizontal transmit from infected wasp to uninfected wasp in the host insect.Wolbachia widely exists in arthropods,Wolbachia is the most widely distributed and abundant cell symbiotic bacteria.Investigate the effects of Wolbachia on host wasps' superparasitism could contribute to a better understanding of the three nutritional levels and co-evolutionary relationship of host insect,parasitic wasps and symbiotic bacterias,which is also helpful for revealing the molecular mechanism of symbiotic bacterias regulating the behavior of host's wasps,and also providing a scientific basis for the application of parasitic wasps.As an egg parasitic wasps,Trichogramma species have been world widely used in the control of agricultural and forestrial pests for a long time.Trichogramma species can be divided into two groups according to their reproductive mode.The most common mode of reproduction is arrhenotoky,thelytoky is another mode of reproduction which Wolbachia-infected females produce females.In this study,Wolbachia-infected Trichogramma dendrolimi Matsumura(thelytokous strain;Td W)and Wolbachia-uninfected T.dendrolimi(bisexual strain;Td)were used as the research object.We invesitigated the influences of Wolbachia on the host's superparasitism behavior.The results would contribute to a new insight of the interaction between host and Wolbachia.The results showed:1.The effect of Wolbachia on host recognition ability of T.dendrolimi was investigated..Compared with the Td strain females,Td W strain females prefered to exhibit superparasitisim.In the different interval times(0-1 h,8 h,16 h,and 32 h),the frequency of inter-superparasitism and intra-superparasitism of the Td W strain females were significantly higher than those of the Td W strain females.And with the extension of interval times,the frequency of inter-superparasitism of both strains females significantly increased with interval times.2.The horizontal transmission of Wolbachia in the same host was detected.The results showed that when the Td and Td W strains coexisted in the same host egg,Wolbachia could horizontally transmit from infected offspring to uninfected offspring.The reproductive trait of some new infected offspring of Td strain were changed,where females could produce female offspring without mating.3.The effect of Wolbachia on the offspring competition of T.dendrolimi was investigated at different developmental stages.Regardless of different developmental stages(0-1 h,8 h,16 h and 32 h)and T.dendrolimi strains,the survival rate of offsprings emerged from superparsitic hosts were significantly lower than those emerged form single-parasitic hosts.In single-parasitic hosts,the survival rate of Td W strain offsprings were significantly lower than those of Td strain offsprings.The survival rate of the second deposited offspring significantly decreased with interval times.In the condition of superparasitism,the fecundity,body size,and life span of Td W strain offsprings were significantly lower than those of Td strain offsprings.The fitness parameters of the firstly deposited offspring increased with interval,where those of the second deposited offspring significantly decreased with interval time.4.The effect of Wolbachia on the competition of T.dendrolimi offspring was investigated at embryonic stage.The survival rates of two strains offsprings emerged from superparasitised host eggs were significantly lower than those emerged from single-parasitised host eggs,regardless of different embryonic stages(0-1 h,3 h,6 h and 9 h)and T.dendrolimi strains.The survival rate of Td W strain offsprings was significantly lower than that of Td strain of offsprings.In addition,under the condition of superparasitism,the fecundity,body size,and life span of Td W strain offsprings were significantly lower than those of Td strain offsprings.The fitness parameters of the first deposited offspring were not influenced by interval times,where those of the second deposited offspring significantly decreased with time interval.