Wolbachia strain wMelM disrupts egg retention by Aedes aegypti females prevented from ovipositing

Aedes aegypti mosquitoes are well adapted to dry climates and can retain their eggs for extended periods in the absence of suitable habitat. Wolbachia strains transferred from other insects to mosquitoes can be released to combat dengue transmission by blocking virus replication and spreading through populations, but host fitness costs imposed by Wolbachia, particularly under some environments, can impede spread. We therefore assessed the impact of two Wolbachia strains being released for dengue control (wAlbB and wMelM) on fecundity and egg viability following extended egg retention (12 or 18 d) under laboratory conditions. Egg viability decreased to a greater extent in females carrying wMelM compared to uninfected or wAlbB females. Fertility fully recovered in uninfected females following a second blood meal after laying retained eggs, while wMelM females experienced only partial recovery. Effects of wMelM on egg retention were similar regardless of whether females were crossed to uninfected or wMelM males, suggesting that fitness costs were triggered by Wolbachia presence in females. The fecundity and hatch proportions of eggs of wMelM females declined with age, regardless of whether females used stored sperm or were recently inseminated. Costs of some Wolbachia strains during egg retention may affect the invasion and persistence of Wolbachia in release sites where larval habitats are scarce and/or intermittent.