The proximate bases of resistance against ectoparasitism in Drosophila melanogaster

Parasites have been shown to drive rapid host evolution, act as vectors for disease, and cause direct fitness costs to their hosts. While considerable research has been directed toward understanding the mechanisms of insect host defense against endoparasites, such studies focusing on ectoparasites of insects are not well represented in the literature. In our previous studies, Drosophila melanogaster and D. nigrospiracula (Diptera: Drosophilidae) have been successfully artificially selected for increased resistance to ectoparasitic mites, Macrocheles subbadius (Mesostigmata: Macrochelidae). However, the specific behavioral mechanisms employed by Drosophila to defend themselves against ectoparasitic attack remain unknown. To elucidate defensive behaviors against mites in Drosophila, I am studying six mutant lines of the host D. melanogaster that have been shown to exhibit altered locomotor performance. Resistance assay data indicate significant differences in parasite resistance among lines; two of the mutant lines exhibit significantly and consistently greater ability to resist ectoparasitism compared to susceptible genotypes. I am testing the hypothesis that resistant lines are better able to defend themselves because they can perform energetically expensive behaviors for relatively longer durations of time when interacting with mites. The results will provide insights into how insect hosts defend against a widespread class of ectoparasitic organisms.