Temperature and aging, individually and interactively, shape the body size and composition of adult mosquitoes

Abiotic and biotic factors, including temperature and age, shape how insects survive, reproduce, and transmit disease. Most insects are poikilothermic ectotherms. This means that as global temperatures rise, insect metabolism and development quicken because their body temperature depends on and fluctuates with their environment. As insects age, their metabolism slows, immune response weakens, and body condition deteriorates due to senescence. Therefore, individually both temperature and age impact the physiological prowess of insects, but it is unknown whether or how these factors interact. Using the mosquito, Anopheles gambiae, we investigated how warmer temperature (27°C, 30°C and 32°C) and aging (1, 5, 10, and 15 days post-eclosion), individually and interactively, shape insect size and body composition. We found that warmer temperatures result in marginally smaller mosquitoes. Aging shapes both the dry weight and lipid content in a manner that correlates with the initial restoration of nutrients and tissue remodeling that occurs post-metamorphosis, followed by the senescence-based decline that ensues later. Carbohydrate content increases with aging, whereas protein content decreases with both rising temperature and aging. Furthermore, the aging-associated decline in protein content is accelerated in warmer temperatures. Altogether, we find that temperature, age, and their interaction shape the size and composition of adult mosquitoes, ultimately affecting their ability to survive and respond to infection.