Surviving in the fast lane: No increased mortality, but faster growth for pathogen-exposed larvae of a family living beetle

Animal taxa exhibiting post-hatching care can be found throughout the
animal kingdom. During this period, parents aggregate with their offspring
and allow them to invest their resources into growth and development as
parents take over energy consuming tasks. For instance, studies show that
food provisioning and social immunity by parents can alleviate the costs
of an offspring’s immune response to pathogen exposure. However, this
issue has rarely been explored in offspring of species showing plasticity
in their dependency on parental care. Here, we raise the question of how
offspring are affected by pathogen exposure if they have access to social
immunity through a caring parent. Parents of Nicrophorus vespilloides, a
species exhibiting facultative post-hatching care, control the carcass
microbiome by coating it with their antimicrobial exudates, stopping
further decay and protecting their offspring from potential pathogens. We
exposed N. vespilloides offspring to a generalist entomopathogenic fungus,
Beauveria bassiana, while manipulating presence or absence of
post-hatching parental care. We monitored offspring performance parameters
throughout their development and found, curiously, larvae showed an
increase in mean weight and growth rate after being exposed to the
pathogen, while their survival and adult immunity were unaffected. These
effects of pathogen exposure occurred regardless of parental care.
Simultaneously, our results indicate that females invest fewer resources
into their offspring if they have been exposed to the pathogen. Overall,
we show that offspring of facultative subsocial species may not respond
differently to pathogen exposure depending on their parents’ aid.
Additionally, our results indicate that offspring of facultatively
subsocial species may adjust their growth rate in response to pathogen
exposure in the nest.