Parasitic manipulation of the neurogenomic state and caste-related traits of social wasps

While behavioral control of the host is well-understood in many host-parasite systems, we still know little about the mechanisms underlying parasitic manipulation. Here, we take advantage of the social wasp Polistes fuscatus which is exploited by the obligate parasite Xenos peckii (Strepsiptera). This parasitic insect induces castration, longevity, diapause and behavioral changes in female workers wasps, but not in male wasps. To determine which specific genes and/or neuromodulators alter different phenotypic traits in the host, we compared the gene expression among gynes, non-parasitized workers and parasitized workers. Our results show that the transcriptomic profiles of parasitized females shift towards the gyne phenotype; altering physiological, immune and metabolic responses, matching predictions based on the known manipulations. We also tested for transcriptomic profiles in the brains of non-parasitized and parasitized males and found no differences, as predicted by the lack of behavioral or physiological manipulation by the parasite. Finally, we used immunohistochemistry to visualize the effect of the parasite on biogenic amine distribution in the host brain. Together, our results provide novel insights to understand the mechanisms used by the parasite to manipulate the brain and plastic traits of the host.