Investigating Asian longhorned beetle immunity following maternal immunepriming with a fungal pathogen

Insects have an innate immune system that, although having the ability to respond quickly and efficiently to many types of microbial and parasitic attacks, is thought to lack the ability to acquire immunity through memory. It has been demonstrated that in several insect species, including Tenebrio molitor and Tribolium castaneum, parental exposure to a bacterial pathogen increased offspring immunity.  Little work has been done however to determine whether parental priming with a fungal pathogen increases offspring immunity or if trans-generational immune priming occurs in other beetle taxa. Asian longhorned beetles (ALB), Anoplophora glabripennis, from China are invasive woodborers in the eastern United States with the potential to negatively impact economic and environmental interests in US hardwood forests. The entomopathogenic fungus Metarhizium brunneum has been shown to be effective in killing ALB but it is unknown whether exposing beetles to a sub-lethal fungal dose will affect offspring immunity. Adult female beetles were primed with one of the following treatments: live Metarhizium brunneum, heat-killed M. brunneum, live M. anisopliae, heat-killed Serratia marcescens, control treatments. One-week post priming, beetles were allowed to mate and lay eggs. The adult offspring of primed beetles were then challenged with a lethal dose of M. brunneum. Bioassays were conducted to determine the impact of immune priming on beetle longevity and the cellular immune response was quantified 14-16 days post inoculation. To determine whether there was a fitness cost associated with maternal priming successful survival to pupation and adult weight of offspring from primed females were quantified.