Tropilaelaps mercedesae parasitism changes behavior and gene expression in honey bee workers.

Jing Gao,Pingli Dai,Qiang Wang,Yang Yang,Xinling Wang,Qihua Luo,Qingyun Diao,Xing Wang,Shilong Ma,Zhongmin Fu,Feng Liu,Adam G Dolezal

doi:10.1371/journal.ppat.1009684

Abstract

Tropilaelaps mercedesae is one of the most problematic honey bee parasites and has become more threatening to the beekeeping industry. Tropilaelaps can easily parasitize immature honey bees (larvae and pupae) and have both lethal and sublethal effects on the individual worker bees. Our study for the first time experimentally assessed the effects of T. mercedesae on olfactory learning, flight ability, homing ability as well as transcriptional changes in parasitized adult honey bees. T. mercedesae infestation had negative impacts on olfactory associated function, flight ability, and homing rate. The volume of the mushroom body significantly increased in infested honey bees, which may be correlated to the lower sucrose responsiveness as well as lower learning ability in the infested bees. The gene expression involved in immune systems and carbohydrate transport and metabolism were significantly different between infested bees and non-infested bees. Moreover, genes function in cell adhesion play an essential role in olfactory sensory in honey bees. Our findings provide a comprehensive understanding of European honey bees in response to T. mercedesae infestation, and could be used to further investigate the complex molecular mechanisms in honey bees under parasitic stress.

Highlights

Pollinators, especially genus Apis, are critical for the production of agricultural crops and maintaining ecosystems
This work aimed to investigate the influence of T. mercedesae infestation on behavior and gene expression in A. mellifera
We comprehensively investigated the effects of T. mercedesae infestation on a series of behaviors performance, including sucrose responsiveness, olfactory learning, flight and homing ability

Summary

Introduction

Pollinators, especially genus Apis, are critical for the production of agricultural crops and maintaining ecosystems. One of the most critical factors contributing to bee population declines is parasite infestation, which has caused thousands of colony losses worldwide [2]. Previous studies have demonstrated that parasitic mites in the genus Varroa and Tropilaelaps are the major factors causing the collapse of European honey bee (Apis mellifera) in Asian area [3,4,5,6]. Compared with Varroa, Tropilaelaps mites have smaller size, shorter phoretic phase, more rapid locomotion, as well as faster reproductive rate [8,9,10]. With these characteristics, Tropilaelaps mites present a greater threat than the infamous Varroa destructor to A. mellifera. With the frequent transfer of commercial bee colonies, the bee trade globalization, the natural proliferation of bees, and the gradual warming of the global climate, it may be only a matter of time until Tropilaelaps spread outside of Asia to cause devastating effects on apiculture industry in Europe and North America [6]

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