Wolbachia inhibits ovarian formation and increases blood avidity in female Aedes aegypti

Abstract

Wolbachia, a gram-negative endosymbiotic bacterium widespread in arthropods, is well-known for changing the reproduction of its host in ways that increase its rate of spread, but there are also costs to hosts that can reduce this. Here we investigated a novel reproductive alteration of Wolbachia wAlbB on its mosquito host Aedes aegypti, based on studies of mosquito life history traits, ovarian dissections and gene expression assays. We found that an extended period of the larval stage as well as the egg stage, as previously shown, can increase the proportion of Wolbachia-infected females that become infertile; the impact of Wolbachia on infertility therefore accumulated before pupation. We found that ovarian formation was blocked in infertile females, even though infected females had relatively lower Wolbachia densities than fertile infected females. Infertile females also showed a higher frequency of blood feeding following a prior blood meal, indicating that they do not enter a complete gonotrophic cycle. Treatments leading to infertility decreased expression of genes related to reproduction. Our results demonstrate effects related to the causes and consequences of infertile wAlbB-infected Ae. aegypti females with implications for Wolbachia releases and have evolutionary implications for Wolbachia infections in novel hosts.