Shifted levels of sleep and activity during the night as mechanisms underlying ectoparasite resistance

Parasites harm host fitness and are pervasive agents of natural selection capable of driving the evolution of host resistance traits. Previously we demonstrated evolutionary responses to artificial selection for increasing behavioral immunity to <i>Gamasodes queenslandicus</i> mites for <i>Drosophila melanogaster</i>. Here, we report transcriptional shifts in metabolic processes due to selection for mite resistance. We also show decreased starvation resistance and increased use of nutrient reserves in flies from mite-resistant lines. Resistant lines exhibited increased activity, reduced sleep, and elevated oxygen consumption during the night. Using a panel of <i>D. melanogaster</i> lines exhibiting variable sleep durations, we found a positive correlation between mite resistance and reduced sleep. Restraining the activity of artificially selected mite-resistant flies during exposure to parasites reduced their resistance advantage relative to control flies. The results suggest that ectoparasite resistance in this system involves increased activity during the scotophase and metabolic gene expression at the expense of starvation resistance.