Multiple bouts of dehydration impact the physiology of the northern house mosquito, Culex pipiens

Many studies have focused on the response of insects to dehydration, but few have assessed physiological changes that result from multiple dehydration exposures. In this study, we examine changes in physiology of Culex pipiens during multiple stints of dehydration and rehydration; particularly we determine if these chronic bouts of dehydration stress reduce the prolonged survival of diapausing C. pipiens. After five dehydration/rehydration bouts, mosquitoes provided access to sugar during the rehydration period had considerably higher survival than those only allowed to rehydrate, and were comparable to mosquitoes of the same age that were not dehydrated. After each bout, there was a reduction in the total dry mass of the mosquitoes that were not provided sugar during the rehydration periods between the bouts of dehydration. This dry mass reduction is likely due to utilization of lipid and sugar reserves, and these reductions in metabolic reserves lead to decreased survival after multiple bouts of dehydration/rehydration. Based on our results, diapausing mosquitoes experience a continual decline in lipid reserves with each bout of dehydration. These reduced metabolic reserves correlate with reduced survival time, indicating that diapausing females may not have adequate fat reserves for overwintering if exposed to multiple bouts of dehydration. Overall, multiple dehydration bouts reduce the metabolic reserves of mosquitoes, likely due to the cost of responding to dehydration stress. This reduced survival can be alleviated by providing mosquitoes access to sugar during rehydration between dehydration bouts.