Antennae hold a key to Varroa-sensitive hygiene behaviour in honey bees.

Fanny Mondet,Dany Severac,Marine Rohmer,Cédric Alaux,Yves Le Conte,Alison R Mercer

doi:10.1038/srep10454

Abstract

In honey bees, Varroa sensitive hygiene (VSH) behaviour, which involves the detection and removal of brood parasitised by the mite Varroa destructor, can actively participate in the survival of colonies facing Varroa outbreaks. This study investigated the mechanisms of VSH behaviour, by comparing the antennal transcriptomes of bees that do and do not perform VSH behaviour. Results indicate that antennae likely play a key role in the expression of VSH behaviour. Comparisons with the antennal transcriptome of nurse and forager bees suggest that VSH profile is more similar to that of nurse bees than foragers. Enhanced detection of certain odorants in VSH bees may be predicted from transcriptional patterns, as well as a higher metabolism and antennal motor activity. Interestingly, Deformed wing virus/Varroa destructor virus infections were detected in the antennae, with higher level in non-VSH bees; a putative negative impact of viral infection on bees’ ability to display VSH behaviour is proposed. These results bring new perspectives to the understanding of VSH behaviour and the evolution of collective defence by focusing attention on the importance of the peripheral nervous system. In addition, such data might be useful for promoting marker-assisted selection of honey bees that can survive Varroa infestations.

Highlights

The honey bee parasite Varroa destructor is currently considered to represent the greatest threat to the beekeeping industry worldwide[1]
In honey bee colonies that survive the mite, Varroa sensitive hygiene (VSH) behaviour has been shown to participate actively in limiting outbreaks of Varroa parasitisation. This form of hygienic behaviour involves the detection and removal of brood parasitised by Varroa[10] and it contributes to a social immunity repertoire[11]; a new immune repertoire level that evolved with sociality and that includes the use of antimicrobial materials for nest construction[12], social fever[13] and nest hygiene and grooming[14,15]
Using a bioassay performed in an observation hive, a total of 44 VSH bees of known age, and for which the VSH behaviour was described in detail, were collected (Fig. 1)

Summary

Introduction

The honey bee parasite Varroa destructor is currently considered to represent the greatest threat to the beekeeping industry worldwide[1]. This parasite infests honey bee colonies and reproduces within capped brood cells containing developing bees. Despite the profound impact of Varroa parasitism on honey bee populations, honey bees in several parts of the world have been shown to successfully survive the pathogen[7,8,9]. This strongly suggests that some bees are able to utilise defence mechanisms to fight successfully against mite infestation. This form of hygienic behaviour involves the detection and removal of brood parasitised by Varroa[10] and it contributes to a social immunity repertoire[11]; a new immune repertoire level that evolved with sociality and that includes the use of antimicrobial materials for nest construction[12], social fever[13] and nest hygiene and grooming[14,15]

Methods

Results

Conclusion