Assessing the impact of nutrition availability, competition and predation threat on survival and fitness of Aedes aegypti

Predation is regarded as a strong selective force acting on organisms in the wild. Organisms facing frequent threats of predation are expected to show adaptations that could minimize their risk of predation, but these adaptations come at a cost, usually reduced foraging success. Predators may thus impact prey populations and communities both lethally (direct) or non-lethally (indirect) and these two impacts are crucial for understanding any predator-prey interaction.

This study focusses on understanding how nutrition availability and intraspecific competition interact with risk of predation to induce non-lethal effects on prey life histories. Mosquitoes are an ideal model system for this study, given their complex life history and co-existence with diverse predatory arthropods and fishes in natural habitats. We report results of a factorial experiment involving three levels of nutrition and two larval densities in the presence and absence of non-lethal predation threat from Toxorhynchites rutilus larvae. Effects of different treatment combinations on survival, growth, and development of Aedes aegypti larvae through eclosion, and subsequent adult longevity and reproduction were recorded in a controlled laboratory environment. 

The results of preliminary analyses suggest that larval development rate is sensitive to varying levels of nutrition and competition but not to predation threat. However, when competition for resources is low, nutrition did not impact larval development rates and adult survival. In contrast, when exposed to high levels of intraspecific competition, fewer individuals managed to eclose in low nutrition conditions than in medium and high nutrition treatments. In particular, competition for resources impacted development rate, body mass, and survival of females more severely than male individuals. Further analyses of stored energy reserves (glycogen, protein, and lipids) using biochemical assays, behavior of larvae, and experiments assessing fecundity of adult mosquitoes across treatments are presently underway. Results from these analyses will be crucial to studying how different ecological factors in larval environment shape adult survival and reproduction.