Social Immunity in a Sub-social Insect: Influence of Parental Care and Exposure to Microbes During Development

Exposure to microbes during development can have long-lasting impacts into adulthood. Positive effects include ontogenetic priming (i.e., enhanced immune response due to prior exposure), while negative effects include reduced growth resulting in smaller adults with reduced reproductive performance. Mitigating factors like parental care can reduce or even eliminate any fitness costs. The aim of this study was to determine i) whether exposure to microbes during development causes ontogenetic priming and ii) whether parental care mitigates long-term costs associated with exposure to microbes during development. As study organism, we used the burying beetle Nicrophorus marginatus which provide parental care to its offspring and is regularly exposed to microbes. Burying beetles reproduce on small carrion and feed larvae with regurgitated carrion. Larvae can self-feed, but develop faster and get larger when they receive parental care. To address our questions, we reared offspring in the presence or absence of additional microbes and with and without parental care. Once mature, these females were mated and reared their own offspring in the presence or absence of additional microbes. Antimicrobial potency of anal secretions was not influenced by the microbial exposure during development indicating that no ontogenetic priming has occurred. Similarly, the lack of an effect of exposure to parental care during development on antimicrobial potency of secretion and reproductive success indicates that parental care exerts no modifying effects. These results corroborate findings by other researchers and provide additional evidence that competition with bacteria over carrion is not as important as originally proposed