Warmer temperature accelerates aging in mosquitoes: Linking changes in gene expression to decreased lifespans and worse infection outcomes

The body temperature of most insects is predicated by environmental temperature. Therefore, with climate change, insect body temperature is rising, quickening development, accelerating metabolism, and altering immune response strength. Insect age also affects physiology. With aging, insects senesce, where their body deteriorates, metabolism slows, and immune prowess weakens. The aging process can be conceptualized as a function of time (chronological age) or as a function of physiological efficiency (physiological age). In homeotherms, like mammals, these processes approximate each other. However, with poikilotherms, like most insects, we hypothesize that these processes can become unlinked, where warmer temperature ages insects faster physiologically than chronologically. So, we reared the African malaria mosquito, Anopheles gambiae, at 3 constant temperatures, 27ºC, 30ºC, and 32ºC, and measured (i) their survival, (ii) the intensity of a systemic infection, and (iii) changes in their gene expression at 1, 5, 10, and 15 days post-eclosion. We found that longevity declines with an active infection, warmer temperature shortens lifespans, older mosquitoes die rapidly, and warmer temperature marginally accelerates the aging-dependent decline in survival. Moreover, we discovered that within a mosquito, the intensity of an infection increases with warmer temperature and aging, and that the aging-dependent increase is accelerated when the temperature is warmer. Finally, using RNAseq, we identified how gene expression is directly affected by warmer temperature, aging, and their interaction, and linked these changes to survival and infection outcomes. Thus, warmer environmental temperature dynamically accelerates aging, which has implications for how mosquitoes acquire and transmit disease.