How <em>Varroa</em> Parasitism Affects the Immunological and Nutritional Status of the Honey Bee, <em>Apis mellifera</em>

Abstract

We investigated the effect of the parasitic mite <em>Varroa destructor</em> on the immunological and nutritional condition of honey bees, <em>Apis mellifera</em>, 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. <em>Varroa</em>‑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 (<em>defensin1, abaecin, hymenoptaecin</em>) was either not significantly different between <em>Varroa</em>-infested and uninfested bees or was significantly elevated in <em>Varroa</em>-infested bees, varying with sampling date and bee developmental age. The effect of <em>Varroa</em> 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 <em>Varroa</em>-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 <em>Varroa</em> abundance, irrespective of whether the individual pupa bore <em>Varroa</em>.

Keywords

• &lt;em&gt;Apis mellifera&lt;/em&gt;
• deformed wing virus
• honey bee
• nutritional response to parasite
• &lt;em&gt;Varroa&lt;/em&gt; mite