LB 24-254 - Understanding how larval rearing temperature and nutrition intake affect the fitness and body size of adult Aedes togoi mosquitoes

Background/Question/Methods:

Body size is an informative life-history trait for entomologists, as it provides information about the physiology, behaviour, and ecology of insects. It is a plastic trait, influenced by genetic factors and environmental conditions, such as nutrition intake and temperature, during critical growth periods during the developmental phase. Interestingly, body size is generally positively correlated with fitness and the thermal performance curve of insects typically favour higher temperatures, but insects follow the temperature size rule where higher temperatures create smaller insects. To better understand this relationship and the advantages of different body sizes, we reared Aedes togoi mosquitoes in different environments to create multiple adult body sizes, then subjected the adults to various experimental environments to evaluate their relative fitness’s through longevity. Larvae were subject to one of five rearing treatments with varying temperatures and nutrition levels (18°C with medium nutrition - 18M, 24°C with low nutrition - 24L, 24°C with medium nutrition - 24M, 24°C with high nutrition - 24H, and 30°C with medium nutrition - 30M), and after metamorphosis were moved to one of six adult treatments where they were either fed or starved at one of the three temperatures from the larval rearing conditions.

Results/Conclusions:

The five larval treatments successfully produced four different sized mosquitoes, with the largest mosquitoes coming from 18M, then 24H, 24M, and finally 24L and 30M. Almost every starved mosquitoes died within 5 days, regardless of adult temperature. The mosquitoes from the 18M treatment had the highest survival rates in the 18°C fed adult treatment, and the mosquitoes from the 24H treatment had the highest survival rates in the 24°C and 30°C fed adult treatments. Across all adult environments, the 24H larval treatment out-performed the 24M and 24L treatments. Within each larval treatment and within each adult environment, there were no consistent distinguishable pattern between body size and survival past 1 typical gonotrophic cycle (6 days). These results suggest body size was not the sole best predictor of adult mosquito longevity in differing environments, but rather larval rearing temperature and the nutritional status of larvae. This helps us de-tangle the relationship between temperature, fitness, and body size, by highlighting the significant role nutrition, thermal acclimation during developmental periods can play alongside adult body size when evaluating the relative fitness of mosquitoes.