Transgenerational immunity and the fitness costs of infection during colony foundation of Zootermopsis angusticollis

As predicted by life history theory, immunocompetence, the ability to mount an immune response, is commonly traded-off with reproduction. Parental investment theory predicts that parents who anticipate the future needs of their progeny may provision their unborn offspring with resources that increase their probability of survival. Transgenerational immunity (TGI), the augmentation of offspring immunocompetence by a pathogen-exposed parent, is one such strategy, however, it may be costly to employ. In order for TGI to be evolutionarily viable, offspring must be likely to encounter the same pathogens as their parents. The eusocial, monogamous, biparental termite Zootermopsis angusticollis lives under significant pathogenic constraints, and satisfy the requirements for TGI. I hypothesize that kings and queens will differentially provision their offspring according to their immunological state and that such provisioning will result in trade-offs. The separate and combined maternal and paternal effects were investigated with respect to four treatments: naïve, control, heat-killed cells and challenge with the pathogen Serratia marcescens. Survival, fecundity, embryo morphometrics, embryo immunocompetence, and reproductives’ immunocompetence were quantified. E. coli expressing mCherry was then used to investigate transovarian variolation as a possible mechanism for TGI. These data support the prediction of trade-offs between immune activation and fecundity in challenged queens, and suggests that there are differences between the embryos of immune-challenged parents and control parents. This is the first study to investigate TGI in a non-hymenopteran eusocial insect and lays the necessary groundwork to investigate the mechanism of TGI in future studies.