BayCEER Workshop 2024

Larve in the fast lane: faster growth, not higher mortality, in fungus-exposed offspring of a family living beetle

Family life is an essential stepping stone towards obligate sociality, its emergence and consolidation are key to understanding the mechanisms that drive social evolution and the transitions from solitary life to complex societies. While often greatly beneficial in terms of food acquisition or predator defence, living in groups is also costly. For instance, being in proximity of conspecifics can enable pathogens and parasites to quickly find new hosts and spread through the group. As a result, social living animals have evolved strategies to combat the spread of pathogens and alleviate the costs of infection referred to as social immunity. Social immunity is well-studied in relatively advanced social species like eusocial insects but also occurs in facultative family systems such as Nicrophorus burying beetles. Nicrophorus form temporary family units with their offspring while they breed on vertebrate carcasses, a coveted, ephemeral resource. To combat the potentially harmful microbiome of the carcass and reduce the emission of conspicuous volatiles, Nicrophorus parents coat the carcass with their antimicrobial exudates while they care for their offspring. This behaviour is regarded as an effective social immunity mechanism, but its effectiveness against actual entomopathogens remains surprisingly understudied. We set out to investigate the harmful effects of exposure to the entomopathogenic fungus Beauveria bassiana on Nicrophorus adults and offspring, and to what degree these effects can be alleviated by post-hatching care. We found that, curiously, pathogen exposure increased the growth rate of the larvae during the first 48 hours on the carcass, while survival and immune parameters of the adult offspring were not affected by the treatment.