Trans-generational medication in Drosophila sechellia. Balint Z. Kacsoh, Zachary R. Lynch, Nathan T. Mortimer, Todd A. Schlenke. Biology, Emory University, Atlanta, GA.

   Drosophila species are regularly infected by parasitoid wasps, which lay eggs in the hemocoels of fly larvae. Flies attempt to kill wasp eggs using an immune response termed melanotic encapsulation, whereby hemocytes migrate towards and adhere to the wasp egg, eventually resulting in a blackened capsule. Surprisingly, a sister species of D. melanogaster, D. sechellia, lacks the ability to melanotically encapsulate any of the 15 wasp species tested. D. sechellia has evolved numerous specializations to live on the fruit of Morinda citrifolia, which contain high levels of octanoic acid that are toxic to other flies. I hypothesized that D. sechellia might use octanoic acid as a medication to prevent or cure wasp infections in the absence of the canonical melanotic encapsulation response. I found that D. sechellia adults preferentially lay eggs on oviposition sites with higher levels of octanoic acid in the presence of wasps, and that eggs laid on octanoic acid food have significantly higher eclosion success in the presence of wasps. Adult flies sense the wasps by sight, increase their own octanoic acid resistance after seeing wasps, and remember having seen the wasps for the rest of their lives. D. sechellia alter their oviposition behavior in response to multiple larval parasitoid wasp species but not against a pupal parasitoid, and can also distinguish male and female wasps. Altogether, my data demonstrate a novel, trans-generational prophylactic medication behavior that D. sechellia use as one of their main defenses against parasitoid wasp infection.