Varroa destructor parasitism reduces hemocyte concentrations and prophenol oxidase gene expression in bees from two populations

Gun Koleoglu,Ernesto Guzman-Novoa,Mariana Reyes-Quintana,Paul H Goodwin,Mollah Md Hamiduzzaman

doi:10.1007/s00436-018-5796-8

Gun Koleoglu, Ernesto Guzman-Novoa + Show 3 more

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https://doi.org/10.1007/s00436-018-5796-8

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Abstract

Circulating hemocytes are responsible for defensive and healing mechanisms in the honey bee, Apis mellifera. Parasitism by the mite Varroa destructor and injection of V. destructor homogenate in buffer, but not buffer injection, showed similar reductions in total hemocyte concentrations in both Africanized and European adult honey bees. This indicated that compounds in V. destructor homogenate can have similar effects as V. destructor parasitism and that the response is not solely due to wounding. Samples from honey bees with different hemocyte concentrations were compared for the expression patterns of hemolectin (AmHml), prophenol oxidase (AmPpo), and class C scavenger receptor (AmSRC-C). Of the genes tested, only the expression of AmPpo correlated well with hemocyte counts for all the treatments, indicating that melanization is associated with those responses. Thus, the expression of AmPpo might be a suitable biomarker for hemocyte counts as part of cellular defenses against injection of buffer or mite compounds and V. destructor parasitism and perhaps other conditions involving healing and immunity.

Highlights

Hemocytes in insects are blood cells that circulate in the plasma fluid inside the hemocele (Ribeiro and Brehelin 2006)
Hemocytes are produced during the larval stage of honey bees (Apis mellifera) in lymphatic glands located on either side of the aorta
Hemocyte concentration showed no significant changes over time for the European bee control (F (4, 111) = 0.36; p = 0.837)

Summary

Introduction

Hemocytes in insects are blood cells that circulate in the plasma fluid inside the hemocele (Ribeiro and Brehelin 2006). Cellular responses are part of the innate immune system of insects and involve hemocytes in processes such as phagocytosis, nodulation, and encapsulation (Lavine and Strand 2002). Hemocytes are produced during the larval stage of honey bees (Apis mellifera) in lymphatic glands located on either side of the aorta When honey bees mature and become adults, these glands disappear and hemocyte production stops. Hemocytes are stored under the cuticle or attached to the viscera until needed, at which point they are rapidly recruited to increase their density at the location where required (e.g., a site of wounding or ingress of a parasite) (Richards and Edwards 2002)

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