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Title: How Varroa parasitism affects the immunological and nutritional status of the honey bee, Apis mellifera

Author
item Aronstein, Katherine
item Saldivar, Eduardo
item VEGA, RODRIGO - Cornell University
item WESTMILLER, STEPHANIE - Cornell University
item DOUGLAS, ANGELA - Cornell University

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2012
Publication Date: 6/1/2012
Citation: Aronstein, K.A., Saldivar, E., Vega, R., Westmiller, S., Douglas, A.E. 2012. How Varroa parasitism affects the immunological and nutritional status of the honey bee, Apis mellifera. Insects. 3(3):601-615.

Interpretive Summary: The main goal of this study is to determine how Varroa mite infestation affects the nutritional and immune status of managed honey bees. Pupae, newly-emerged adults and foraging adults were sampled from field colonies in Texas. Varroa infested bees displayed, first, reduced melanization response to septic injury with the pathogenic fungus and bacterium, and, second, elevated titer of DVW virus, indicative of depressed capacity to limit viral replication. Expression of genes coding three honey bee anti-microbial peptides either did not differ significantly 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. The 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.

Technical Abstract: We investigated the effect of the parasitic mite Varroa destructor 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 up to 10 colonies at one site in S. Texas, USA. Varroa infested bees displayed, first, reduced melanization response to septic injury with the pathogenic fungus and bacterium, and, second, elevated titer of DVW virus, indicative of depressed capacity to limit viral replication. Expression of genes coding three anti-microbial peptides (defensin1, abaecin, hymenoptaecin) either did not differ significantly 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.