Desiccation tolerance and its effect on egg viability and hatch rates in container-inhabiting mosquitoes

Desiccation tolerance has been considered an important factor of life history evolution and community organization in container mosquitoes. In addition, adaptive responses such as egg diapause and quiescence likely incur fitness costs, reflected in lower post-hatching survival, reduced fecundity, and lower fitness. We investigated the desiccation tolerance at the egg stage and its impact on egg viability and hatch rates of two container mosquitoes: the Asian tiger mosquito Aedes albopictus and the eastern tree-hole mosquito Aedes triseriatus. Batches of about 200 eggs and batches of about 50 eggs (both F₂ generation) were collected respectively for both species and stored separately in each of 3 relative humidities (RH): 40%, 65% and 85%. All 200 egg batches were hatched after 6 weeks whereas after weeks 1, 2, 3, 4 and 6 weeks the additional batches of 50 eggs were hatched. All unhatched eggs were bleached to check for viability. Among the 200 egg batches, total hatch rate increased significantly with RH’s; Aedes albopictus had a higher percentage hatch across RH’s compared to A. triseriatus. Among the weekly hatches, percentage hatch decreased with weekly storage period across all relative humidities for A. albopictus. There were no hatches observed at 40% and 65% RH’s for A. triseriatus even though most eggs were viable as confirmed from egg bleaching. However, there was a significant increase in A. triseriatus hatch rate with storage period at 85% RH. Thus, Aedes albopictus could be more desiccation tolerant across wide humidity ranges compared to Aedes triseriatus, whereas the latter species is desiccation tolerant for longer periods, especially at high humidities. This study lends support to current knowledge of range expansion in container mosquitoes. Future studies aim to access the presence and levels of carry-over effects of egg-stage desiccation tolerance and larval and adult performance.