Anopheline mosquito survival strategies during the dry period in western Kenya

The dry season survival mechanism of Anopheles gambiae Giles is one of the most vexing deficiencies in our understanding of the biology of the major m alaria vectors. In this study. we examined the dynamics of anopheline adult mosquitoes their larval habitats, and egg survival potential during the dr y season in the basin region of Lake Victoria western Kenya. Through field surveys, we demonstrated two survival strategies of An. gambiae sensu stric to during the dry season: continuous reproduction throughout the year and e mbryo dormancy in moist soil for at least several days. We further demonstr ated that An. gambiae shows a strong preference for moist soil as an ovipos ition substrate rather than dry soil substrate under the insectary conditio ns. The observation that anopheline eggs remain a dormant stage to resist d esiccation clearly contrasts the conventional wisdom that anopheline eggs h atch shortly after they are laid. Our results from western Kenya are consis tent with the suggestion that anopheline mosquitoes do not necessarily suff er a severe population bottleneck during the dry season and thus maintain a large effective population size.