Transgenerational immunity in an insect model organism

Parental investment theory predicts that parents exposed to pathogenic microbes may increase their own and their offspring’s fitness by provisioning their eggs in a manner that renders them less susceptible to disease.  Such non-genetic differential contributions can influence the size, weight and metabolite content of eggs and ultimately, their hatching success. This study tested the hypothesis that differential maternal provisioning exists in the Tobacco Hornworm moth, Manduca sexta and that progeny vary in their physical attributes and their metabolite composition depending on their mother’s pathogenic history.  Female pupae were weighed and randomly assigned to four different treatments: naïve (not injected), control (saline injected), immunized (injected with heat killed Serratia marcescens) and challenged (injected with a sublethal dose of active S. marcescens). Upon eclosion and copulation, the total number of eggs oviposited within the lifetime of the adult female was recorded. Additionally, various physical attributes of the embryos (volume, mass), developmental milestones (time to hatch) and immune function (antifungal and antibacterial properties) were compared across maternal treatments. Our results are consistent with maternal contributions to their progeny differing depending on the mother’s immunological state.  These differences my ultimately influence the offspring's survival in a microbial-rich environment.