Pest and Environmental Adaptation Research Group, Bio21 Institute and the School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.
PLoS Negl Trop Dis. 2021 Feb 16;15(2):e0009179. doi: 10.1371/journal.pntd.0009179. eCollection 2021 Feb.
The endosymbiotic bacterium Wolbachia shows viral blocking in its mosquito host, leading to its use in arboviral disease control. Releases with Wolbachia strains wMel and wAlbB infecting Aedes aegypti have taken place in several countries. Mosquito egg survival is a key factor influencing population persistence and this trait is also important when eggs are stored prior to releases. We therefore tested the viability of mosquitoes derived from Wolbachia wMel and wAlbB-infected as well as uninfected eggs after long-term storage under diurnal temperature cycles of 11-19°C and 22-30°C. Eggs stored at 11-19°C had higher hatch proportions than those stored at 22-30°C. Adult Wolbachia density declined when they emerged from eggs stored for longer, which was associated with incomplete cytoplasmic incompatibility (CI) when wMel-infected males were crossed with uninfected females. Females from stored eggs at both temperatures continued to show perfect maternal transmission of Wolbachia, but storage reduced the fecundity of both wMel and wAlbB-infected females relative to uninfected mosquitoes. Furthermore, we found a very strong negative impact of the wAlbB infection on the fertility of females stored at 22-30°C, with almost 80% of females hatching after 11 weeks of storage being infertile. Our findings provide guidance for storing Wolbachia-infected A. aegypti eggs to ensure high fitness adult mosquitoes for release. Importantly, they also highlight the likely impact of egg quiescence on the population dynamics of Wolbachia-infected populations in the field, and the potential for Wolbachia to suppress mosquito populations through cumulative fitness costs across warm and dry periods, with expected effects on dengue transmission.
内共生细菌沃尔巴克氏体在其蚊宿主中表现出病毒阻断作用，从而被用于控制虫媒病毒病。携带沃尔巴克氏体菌株 wMel 和 wAlbB 的埃及伊蚊释放已经在几个国家进行。蚊子卵的存活率是影响种群持续存在的关键因素，而在释放前储存卵时，这一特性也很重要。因此，我们测试了在 11-19°C 和 22-30°C 的日温度循环下长期储存的感染和未感染沃尔巴克氏体 wMel 和 wAlbB 的蚊子的卵的生存能力。在 11-19°C 下储存的卵的孵化比例高于在 22-30°C 下储存的卵。当它们从储存时间较长的卵中孵化出来时，成虫沃尔巴克氏体的密度下降，这与 wMel 感染的雄性与未感染的雌性交配时不完全细胞质不相容（CI）有关。在这两种温度下储存的卵的雌性继续表现出完美的母体传递沃尔巴克氏体，但储存会降低感染 wMel 和 wAlbB 的雌性的繁殖力，而相对于未感染的蚊子。此外，我们发现 wAlbB 感染对在 22-30°C 下储存的雌性的生育力有很强的负面影响，在储存 11 周后，几乎 80%的雌性孵化后无法生育。我们的研究结果为储存感染沃尔巴克氏体的埃及伊蚊卵以确保释放后具有高适应性的成虫蚊子提供了指导。重要的是，它们还强调了卵休眠对野外感染沃尔巴克氏体种群动态的可能影响，以及沃尔巴克氏体通过在温暖和干燥时期累积适应成本来抑制蚊子种群的潜力，这可能对登革热传播产生影响。
