How Varroa Parasitism Affects the Immunological and Nutritional Status of the Honey Bee, Apis mellifera.

Katherine A Aronstein,Stephanie Westmiller,Angela E Douglas,Eduardo Saldivar,Rodrigo Vega

doi:10.3390/insects3030601

Katherine A Aronstein, Stephanie Westmiller + Show 3 more

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https://doi.org/10.3390/insects3030601

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Abstract

We investigated the effect of the parasitic mite Varroadestructor on the immunological and nutritional condition of honey bees, Apis mellifera, from the perspective of the individual bee and the colony. Pupae, newly-emerged adults and foraging adults were sampled from honey bee colonies at one site in S. Texas, USA. Varroa‑infested bees displayed elevated titer of Deformed Wing Virus (DWV), suggestive of depressed capacity to limit viral replication. Expression of genes coding three anti-microbial peptides (defensin1, abaecin, hymenoptaecin) was either not significantly different between Varroa-infested and uninfested bees or was significantly elevated in Varroa-infested bees, varying with sampling date and bee developmental age. The effect of Varroa on nutritional indices of the bees was complex, with protein, triglyceride, glycogen and sugar levels strongly influenced by life-stage of the bee and individual colony. Protein content was depressed and free amino acid content elevated in Varroa-infested pupae, suggesting that protein synthesis, and consequently growth, may be limited in these insects. No simple relationship between the values of nutritional and immune-related indices was observed, and colony-scale effects were indicated by the reduced weight of pupae in colonies with high Varroa abundance, irrespective of whether the individual pupa bore Varroa.

Highlights

It is widely accepted that the nutritional and immunological responses of animals to parasitization are not independent [1,2]
The focus of this study is the interaction between the honey bee, Apis mellifera, and the mite Varroa destructor [7], an ectoparasite that feeds on the hemolymph of larvae, pupae and adult bees [8,9]
The titer of Deformed Wing Virus (DWV) in pupae and newly-emerged bees was quantified in August and September, when there were sufficient Varroa-infested insects for analysis

Summary

Introduction

It is widely accepted that the nutritional and immunological responses of animals to parasitization are not independent [1,2]. Both responses are demanding on nutritional reserves, such that an animal’s capacity to mount an immunological response can be critically dependent on its nutritional status [3,4], and parasite-mediated immunosuppression can have complex effects on the nutritional condition of its host [5]. The focus of this study is the interaction between the honey bee, Apis mellifera, and the mite Varroa destructor [7], an ectoparasite that feeds on the hemolymph of larvae, pupae and adult bees [8,9]. Varroa infestation is recognized as one of the most urgent problems facing the beekeeping industry [10,11,12]

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