<i>Wolbachia</i> strain <i>w</i> MelM disrupts egg retention by <i>Aedes aegypti</i> females prevented from ovipositing

<i>Aedes aegypti</i> mosquitoes are well adapted to dry climates and can retain their eggs for extended periods in the absence of suitable habitat. <i>Wolbachia</i> 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 <i>Wolbachia</i>, particularly under some environments, can impede spread. We, therefore, assessed the impact of two <i>Wolbachia</i> strains being released for dengue control (<i>w</i>AlbB and <i>w</i>MelM) on fecundity and egg viability following extended egg retention (up to 24 days) under laboratory conditions. Egg viability following retention decreased to a greater extent in females carrying <i>w</i>MelM compared to uninfected or <i>w</i>AlbB females. Fertility fully recovered in uninfected females following a second blood meal after laying retained eggs, while <i>w</i>MelM females experienced only partial recovery. Effects of <i>w</i>MelM on egg retention were similar regardless of whether females were crossed to uninfected or <i>w</i>MelM males, suggesting that fitness costs were triggered by <i>Wolbachia</i> presence in females. The fecundity and hatch proportions of eggs of <i>w</i>MelM females declined with age, regardless of whether females used stored sperm or were recently inseminated. Costs of some <i>Wolbachia</i> strains during egg retention may affect the invasion and persistence of <i>Wolbachia</i> in release sites where larval habitats are scarce and/or intermittent.IMPORTANCE<i>Wolbachia</i> mosquito releases are expanding around the world with substantial impacts on dengue transmission. Releases have succeeded in many locations, but the establishment of <i>Wolbachia</i> has been challenging in some environments, and the factors contributing to this outcome remain unresolved. Here, we explore the effects of <i>Wolbachia</i> on a novel trait, egg retention, which is likely to be important for the persistence of mosquito populations in locations with intermittent rainfall. We find substantial impacts of the <i>Wolbachia</i> strain <i>w</i>MelM on the quality of retained eggs but not the <i>w</i>AlbB strain. This cost is driven by the <i>Wolbachia</i> infection status of the female and can partially recover following a second blood meal. The results of our study may help to explain the difficulty in establishing <i>Wolbachia</i> strains at some field release sites and emphasize the need to characterize <i>Wolbachia</i> phenotypes across a variety of traits and strains.