Temperature induces trade-offs between development and starvation resistance in Aedes aegypti (L.) larvae

Heightened temperature increases the development rate of mosquitoes. However, in Aedes aegypti (Diptera: Culicidae), the larvae of which commonly experience limited access to food in urban habitats, temperature effects on adult production may also be influenced by changes in the capacity of larvae to survive without food. We carried out experiments to investigate the effects of temperatures increasing at intervals of 2 degrees C from 20 degrees C to 30 degrees C on the growth, maturation rate and longevity of optimally fed larvae placed in starvation. Overall, both growth rate and starvation resistance were lower in the first three larval instars (L1-L3) compared with L4, in which growth of >75% occurred. Although increasing the temperature reduced the duration of each instar, it had a U-shaped impact in terms of the effect of initial growth on starvation resistance, which increased from L1 to L2 at 20 degrees C and 30 degrees C, remained constant at 22 degrees C and 28 degrees C, and decreased at 24 degrees C and 26 degrees C. Growth from L2 to L3 significantly increased starvation resistance only from 26 degrees C to 30 degrees C. Increased temperature (> 22 degrees C) consistently reduced starvation resistance in L1. In L2-L4, increments of 2 degrees C decreased starvation resistance between 20 degrees C and 24 degrees C, but had weaker and instar-specific effects at > 24 degrees C. These data show that starvation resistance in Ae. aegypti depends on both instar and temperature, indicating a trade-off between increased development rate and reduced starvation survival of early-instar larvae, particularly in the lower and middle temperatures of the dengue-endemic range of 20-30 degrees C. We suggest that anabolic and catabolic processes in larvae have distinct temperature dependencies, which may ultimately cause temperature to modify the density regulation of Ae. aegypti populations.