Prolonged dehydration resistance by the northern house mosquito, Culex pipiens, during its overwintering diapause

Throughout the winter, the northern house mosquito, Culex pipiens, is continually exposed to desiccating conditions, and this water deficit is further exacerbated by long periods with no access to free water. In this study, we report that mosquitoes in diapause are more tolerant of xeric conditions than their nondiapausing counterparts. To counter water loss female mosquitoes reared under conditions that induce diapause have a lower percent water content that results from a higher dry mass which in turn decreases their surface area to volume ratio. Both diapausing and nondiapausing females can tolerate a loss of approximately 30%, but diapausing females conserve their water reserves more do not reach this limit as readily. This mosquito relies solely on drinking free water to replenish its water supply and has no ability to absorb water vapor from the atmosphere. Cuticular hydrocarbon content was nearly 3x higher in diapausing female mosquitoes than nondiapausing individuals, this enhancement impedes water loss through the cuticle. No differences were noted in sorbitol, trehalose, glycerol or the total sugar contents during diapause. Additionally, the utilization on internal lipids by diapausing C. pipiens was significantly lower than nondiapausing female. Thus, the increased dehydration resistance of diapausing females C. pipiens results from the combination of their larger size, accumulation of additional cuticular lipids, and a suppression of metabolism