The Effects Of Endosymbionts Wolbachia And Cardinium On The Predation Behavior Of Predatory Mites

Wolbachia and Cardinium are intracellular symbiotic bacteria that widely distributed in arthropods and can regulate various reproductive abnormalities in their hosts,including CI,parthenogenesis,feminizaton and male-killing.Although the distribution of Cardinium is not so widespread than Wolbachia and the study about the effect of Cardinium on the reproductive activities of their host are relatively small,Cardinium has been found to cause cytoplasmic incompatibility,parthenogenisis,feminization,and be associated with the fitness of their hosts.The generalist predatory mite Neoseiulus cucumeris(Oudemans)(Acari:Phytoseiidae)is a cosmopolitan species that is commonly used as a biological control agent for spider mites and other small pests worldwide.N.cucumeris is commercially available and easy to rear and establish on crops in the field and in greenhouses.The efficiency of the regulation of pests may be influenced by the intra-guild interactions between pathogens and natural enemies.Wolbachia and Cardinium are associated with the fitness of their hosts.Therefore,the combination of endosymbionts with predatory mite may suppress the population density of pests.The study assessed the effects of endosymbionts on the functional and numerical response,predation capacity,fitness of predatory mites when fed onWolbachia-infected and uninfected Tetranychus urticae and Cardinium-infected and uninfected Tetranychus cinnabarinus.We investigated the impacts of Wolbachia and Cardinium on the functional and numerical response of predatory mites.The results indicated that the preceding results indicate that the functional responses of N.cucumeris to infected and uninfected populations of T.urticae and T.cinnabarinus are all type ?,which means that predators increase their prey consumption with increasing prey availability to a maximum,after which prey consumption decreases.The eggs laid were highly correlated with prey density.The maximum amount of eggs when fed on Wolbachia-infected and uninfected prey was respectively 2.894±0.075/day and 2.617±0.065/day,and Cardinium-infected and unifected prey was 3.172±0.132/day and 3.09±0.152/day.Wolbachia and Cardinium did not affect the functional and numerical response.The results showed that the effects of Wolbachia and Cardinium on predation capacity were very similar.In the no-choice experiment,the number of prey consumed by N,cucumeris significantly decreased with increasing prey stage.When predator mites were offered infected prey,they consumed significantly more eggs than other stages but when they were offered uninfected prey,they consumed significantly more larvae.The consumption of uninfected larvae was significantly higher than that of infected larvae,but for other stages,consumption was not significantly different between uninfected and infected prey.When predators were given a choice between four different pairs of life stages,infection status had no effect on preference for life stage,as expressed by the preference index ?.N.cucumeris had a significant preference for eggs when the choices were between eggs and nymphs(protonymphs or deutonymphs).(In a given pair of life stages,the preference refers to the first life stage in the pair).However,they had a significant preference for larvae compared to eggs.Overall,the results of the no-choice indicate that N.cucumeris has no preference when feeding on uninfected and infected T.urticae.N.cucumeris has a preference for Wolbachia and Cardinium uninfected eggs.When N.cucumeris were allowed to choose between bean leaves that had or had not been pre-infested with prey,they significantly preferred the pre-infested leaves,regardless of whether the prey were infected.Significantly more N.cucumeris were found on leaf discs with mobile stages than on discs with eggs,regardless of whether the preys were infected.N.cucumeris preferred uninfected prey over infected prey for mobile stages and eggs in the presence of a plant leaf.We also assessed the effects of endosymbionts on the fitness.The results indicated that Wolbachia and Cardinium have no significant effect on the sex ratio,life span,fecundity,but have significant effect on the developmental time.Wolbachia shortened the developmental time of male mite and Cardinium shortened the the developmental time of female mite.