The Olfactory Logic behind Fruit Odor Preferences in Larval and Adult Drosophila.

Despite the comprehensive knowledge on odor coding, our understanding of the relationship between sensory input and behavioral output in Drosophila remains weak. Here, we measure the behavioral responses generated by larval and adult flies in response to 34 fruit odors and find that larval preference for fruit odors differs from that of adult flies. Next, we provide a functional analysis of the full repertoire of the peripheral olfactory system using the same comprehensive stimulus spectrum. We find that 90% and 53% of larval and adult olfactory receptors tested here, respectively, are involved in evaluating these fruit odors. Finally, we find that the total amount of olfactory neuronal activity correlates strongly positively with behavioral output in larvae and correlates weakly negatively in adult flies. Our results suggest that larval and adult flies have evolved different mechanisms for detection and computation of fruit odors, mechanisms likely mirroring the different lifestyles of both developmental stages.