Symbionts in Nesidiocoris tenuis (Hemiptera: Miridae): association with the heat tolerance of the host?

In nature, some arthropods harbor intracellular bacterial symbionts that influence their hosts. Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is a zoophytophagous insect that is widely used as a biological control agent of whiteflies and other minute pests in greenhouses. In Israel, N. tenuis populations were highly infected by the endosymbiotic bacterium Rickettsia, although the role of the bacterium has not been clarified. Marina et al. (2011) reported that the presence of Rickettsia in Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) may contribute to the heat tolerance of the host. In this study, we aimed to clarify whether Rickettsia in N. tenuis is associated with the heat tolerance of the host.
To compare the regional differences in the rates of Rickettsia infection, we collected 20 populations of N. tenuis from Okinawa (southern part of the western district of Japan), Kagoshima, Miyazaki, Kumamoto, and Fukuoka (northern part of the western districts of Japan). Moreover, to compare seasonal differences, individuals from three N. tenuis populations each were collected in mid-summer and late summer from the same area. Twenty-four adult individuals from each population were extracted and the infection rate of Rickettsia was determined using PCR. The results showed that N. tenuis that occurred in warmer areas tended to have higher infection rates. Further, the infection rate significantly increased from mid-summer to late summer. These results indicate that Rickettsia in N. tenuis may be related to the heat tolerance of the host.