Distinct physiological, biochemical and morphometric adjustments in the malaria vectors Anopheles gambiae and An. coluzzii as means to survive to dry season conditions in Burkina Faso

Abstract

Aestivation and dispersive migration are the two strategies evoked in literature to explain the way by which malaria vectors, Anopheles coluzzii and An. gambiae, survive the harsh climatic conditions of the dry season in sub-Saharan Africa. However, the physiological mechanisms regulating these two strategies are unknown. Here, mosquito species were submitted to controlled environmental parameters mimicking the rainy and dry seasons conditions of south-western Burkina Faso. Survival strategies were studied through morphometric (wing length), ecophysiological (respiratory gas exchanges), biochemical (cuticular hydrocarbons composition) and molecular (AKH mRNA expression levels) parameters of which variations are classically considered as hallmarks of aestivation and dispersion mechanisms in various insects. Our results showed that ecophysiological and morphometric adjustments are put in place in both species to prevent water losses during the dry season. However, the classical metabolic rate modifications expected as signatures of aestivation and migration were not evidenced here, highlighting specific and original physiological mechanisms sustaining survival in malaria mosquitoes during the dry season. Differences in epicuticular hydrocarbons composition and AKH levels of expression were found between the permanent and temporary An. coluzzii populations, illustrating the great phenotypic plasticity of this mosquito species. Altogether, our work underlines the diverse and complex pattern of changes occurring in the two mosquito species and at the population level to cope with the dry season and highlights potential targets of future control tools.