Effects of Wolbachia on fitness of Culex quinquefasciatus (Diptera; Culicidae).

Wolbachia are α-proteobacteria that were first reported in Culex pipiens mosquitoes early in the twentieth century. Since then, the effect of Wolbachia on their host's reproduction has drawn attention and has been increasingly investigated. Given the extreme complexity of this interaction, new study cases are welcomed to enhance its understanding. The present work addressed the influence of Wolbachia on Cx. quinquefasciatus, the cosmopolitan member of the Cx. pipiens complex. Samples of a Cx. quinquefasciatus colony (wPip(+)) originated from individuals naturally infected by Wolbachiapipientis B strain, were cured with tetracycline, yielding a Wolbachia-free colony (wPip(-)). Both the presence of bacteria and the efficiency of bacterial elimination were checked by PCR of the wsp gene. Total reproductive unidirectional incompatibility occurred when wPip(-) females were crossed with wPip(+) males, whereas the other three types of reciprocal crosses were viable. Reproductive aspects were also comparatively evaluated between colonies. Concerning oviposition time during the first gonotrophic cycle, wPip(+) females developed and laid eggs earlier than did wPip(-) females. Reproductive fitness was higher among wPip(-) than wPip(+) females regarding the following parameters: fertility: egg rafts/fed females; fecundity: eggs/raft, and viability: larvae/eggs. Conversely, longevity of wPip(-) females was lower. Summarising, although the infected mosquitoes have the advantage of a higher longevity, they have lower reproductive fitness. Our results are partly distinct from all other reports on Aedes and Culex mosquitoes previously published.