Wolbachiainhibits ovarian formation and increases blood feeding rate in femaleAedes 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 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.

Fitness costs ofWolbachiashift in locally‐adaptedAedes aegyptimosquitoes

“…This effect was Wolbachia-specific because uninfected females stored for the same amount of time never became infertile. The effects of egg storage on infertility are similar to those described previously for the wAlbB infection (Lau et al, 2021a(Lau et al, , 2022 but substantially weaker, with 50% infertility observed after only 9 weeks for wAlbB. The weakening of cytoplasmic incompatibility is likely due to partial or complete loss of Wolbachia during egg quiescence as demonstrated previously for wMel (Lau et al, 2021a).…”

“…We showed previously that the wAlbB Wolbachia strain causes female mosquitoes to become infertile if they hatch from stored eggs (Lau et al, 2021a(Lau et al, , 2022. We scored the proportion of females used in crosses in Figure 4 that laid eggs as a measure of infertility, although we note that the storage period to induce this effect is much longer than described previously for wAlbB (Lau et al, 2021a).…”

“…How to cite this article: Ross, P.A. & Hoffmann, A.A. (2022) Fitness costs of Wolbachia shift in locally-adapted Aedes aegypti mosquitoes. Environmental Microbiology, 24(12), 5749-5759.…”

Local adaptation ofAedes aegyptimosquitoes toWolbachia-induced fitness costs

“…This effect was Wolbachia-specific because uninfected females stored for the same amount of time never became infertile. The effects of egg storage on infertility are similar to those described previously for the wAlbB infection [13,35] but substantially weaker, with ~50% infertility observed after only nine weeks for wAlbB. While the additional costs of wMel infection were only apparent after long-term storage, interactions with other environmental factors such as high temperatures, which also reduce cytoplasmic incompatibility by wMel [44], could exacerbate these costs.…”

“…We showed previously that the w AlbB Wolbachia strain causes female mosquitoes to become infertile if they hatch from stored eggs [13, 35]. We scored the proportion of females used in crosses in Figure 4 that laid eggs as a measure of infertility, although we note that the storage period to induce this effect is much longer than described previously for wA lbB [13].…”