| Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and some filamentous nematodes. They are associated with various reproductive abnormalities in their hosts, such as cytoplasmic incompatibility(CI), parthenogenesis inducing(PI), feminization and male killing. They can also influence the fitness and even speciation of their hosts.Nasonia vitripennis(Hymenoptera: Pteromalidae) is an important hymenopteran parasitic wasp of diptera flies pupae. Because of its wide distribution, short generation cycle,large population, easy sex distinguishment, easy breeding, and moreover its genome sequencing has been completed, it has gradually become one kind of experimental insects in laboratory, especially as a potential model organism in hymenoptera.This experiment aims at exploring the deep effect of Wolbachia on N. vitripennis fitness ibased on predecessor’s research. Firstly, we verified that the reproductive regulation of Wolbachia in N. vitripennis we raised is cytoplasmic incompatibility; Secondly, we counted the offspring number and calculated the sex ratios of N. vitripennis of two kinds, rifampicin concentrations(0.1 mg/ml, 0.3 mg/ml, 0.5 mg/ml, 3 mg/ml, 10 mg/ml) treatment and control(natural infection of Wolbachia), in the different amount of fly pupae(1, 3, 5) everyday.Finally, we studied the effect of Wolbachia on longevity of N. vitripennis. The main results were as follows:(1) The effect of Wolbachia on N. vitripennis is cytoplasmic incompatibility. Targeting different Wolbachia infection status of male and female N. vitripennis, we designed four groups of cross mating experiments: the infected female and the infected male(♀ B× ♂ B),the infected female and the uninfected male( ♀ B × ♂ D), the uninfected female and uninfected male(♀ D× ♂ D), the uninfected female and the infected male(♀ D× ♂ B), and we counted the offspring numbers and calculated the sex ratios respectively. The sex ratios of the former three groups were 0.83, 0.83 and 0.71 respectively, while the fourth(♀ D× ♂ B)group was only 0.11, which were significantly lower than the other three kinds of hybrid combinations. Above results showed Wolbachia had strong cytoplasmic incompatibility effect on N. vitripennis.(2) In this study, when we replaced one fly pupae every day, the offspring number ofWolbachia-infected Nasonia vitripennis was about 219, while the offspring number of Wolbachia-uninfected N. vitripennis was less than 200; when we replaced three fly pupae every day, the offspring number of Wolbachia-infected N. vitripennis was about 392, while the offspring number of Wolbachia-uninfected N. vitripennis was about 305; when we replaced five fly pupae every day, the offspring number of Wolbachia-infected N. vitripennis was about 444, while the offspring number of Wolbachia- uninfected N. vitripennis was about407. In a word, not only Wolbachia increase the offspring number of N. vitripennis, but also the increased fly pupae can increase the offspring number of N. vitripennis.(3) In this study, the sex ratio of Wolbachia-infected N. vitripennis were over 0.83, while the sex ratio of Wolbachia-uninfected N. vitripennis were below 0.80. So, Wolbachia can increase the sex ratio of N. vitripennis. When we replaced one, three and five fly pupae every day, the sex ratio of N. vitripennis was about 0.80, 0.82 and 0.83 respectively. The number of fly pupae had no significant influence on offspring sex ratio of N. vitripennis.(4) Influence of Wolbachia on longevity of N. vitripennis. In this study, the Wolbachia-infected and Wolbachia-uninfected N. vitripennis were both tested. There were some influences of Wolbachia on longevity of N. vitripennis, but the influences were not significant.Wolbachia and increased fly pupae have positive effects on fecundity of N. vitripennis,and Wolbachia can increase the sex ratio of N. vitripennis. So we can use Wolbachia and more fly pupae to increase the population number of N. vitripennis in the future, which will make more convenient for indoor research and biological control. |
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