Characterization of wolbachia and cytoplasmic incompatibility in armigeres subalbatus

Abstract

Cytoplasmic incompatibility is the sterility phenomenon which is widely found in several insect species and known to be correlated with Wolbachia, the rickettsia-like bacterial endosymbionts. By using PCR technology, Armigeres subalbatus was found to be infected with this bacteria. In previous studies, Wolbachia infection was found in only gonad tissue. But in this research, it was also distributed in somatic tissues such as Malpighian tubules and midgut. From phylogenetic analysis we found that Wolbachia strain in Armigeres subalbatus is in the same clade as Aedes albopictus strain. This data suggests that one Wolbachia strain can infect many insect hosts which is one of the desirable attributes for a genetic control system. Armigeres subalbatus expresses partial cytoplasmic incompatibility phenotype when crossed Wolbachia-infected males with uninfected females, 57 % egg mortality (n = 10), while in the control cross, there is 9.53% egg mortality (n = 10 Mann-Whitney U test, P<0.0025). The loss of cytoplasmic incompatibility of this insect has been found as in other insect species, when crossed aged-infected males with uninfected females (25% egg mortality Mann-Whitney U test P<0.03). The percent egg mortality of the field caught infected and uninfected mother were determined and found that there is no significantly different percent egg mortality. From this result, we doubted that field male Armigeres subalbatus might mate when they are old. In order to check for the age of the flies in the swarm, the fluorescence pigment in mosquito's head capsule was determined. And from the spectrofluorometric results, we found that males Armigeres subalbatus in the field population mate when they are older than 11 days old. These data might be useful to explain the mechanism of spreading of Wolbachia and the co-existence of the uninfected and infected-Wolbachia in the host in nature.