Two pathogens change cuticular hydrocarbon profiles but neither elicit a social behavioural change in infected honey bees, Apis mellifera (Apidae: Hymenoptera)

Abstract

AbstractSocial immunity is the cooperation of individual group members towards the control of disease transmission arising from social living. It has been identified as an important mechanism of natural disease control in honey bees, Apis mellifera Linnaeus, which can exhibit hygienic behaviours such as evicting pathogen‐infected or parasitised nest mates. Here, we examine if these bees exhibit a change in behaviour towards nest mates infected by the microsporidian pathogens Nosema apis and N. ceranae. We observed no significant change in the frequency of interactive and non‐interactive behaviours of bees towards Nosema‐infected nest mates, for both N. apis and N. ceranae. Thus, uninfected bees interacted and were exposed to pathogen‐infected bees equally often compared with uninfected bees. This lack of any behavioural modification suggests that bees are unable to recognise Nosema‐infected nest mates. These results were surprising given our analysis indicated that Nosema infection changes the hydrocarbon profiles of the bees, enabling the statistical discrimination of uninfected, N. apis and N. ceranae infected bees. The hydrocarbons we analysed were 16 straight‐chain alkanes ranging from heptadecane (C17H36) to tritriacontane (C33H68). Our results and those of others suggest that hygienic behaviour is currently unlikely to provide resistance towards Nosema pathogens in honey bees. The lack of social immunity was unexpected given the co‐evolution of one of the pathogens and honey bees. However, the modification of cuticular hydrocarbons by these pathogens provides a specific cue that may enable future selection and rearing of bees for Nosema‐related social immunity.