Insights into the metabolism and behavior of the honey bee ectoparasitic mite, varroa destructor, from quantitation and chemical analysis of their waste excretions

Authors: POSADA-FLOREZ, FRANCISCO - Non ARS Employee; SONENSHINE, DANIEL - Non ARS Employee; Egekwu, Noble; Rice, Clifford; LUPITSKYY, ROBERT - University Of Maryland; Cook, Steven

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2018
Publication Date: 11/9/2018
Citation: Posada-Florez, F., Sonenshine, D.E., Egekwu, N.I., Rice, C., Lupitskyy, R., Cook, S.C. 2018. Insights into the metabolism and behavior of the honey bee ectoparasitic mite, varroa destructor, from quantitation and chemical analysis of their waste excretions. International Journal for Parasitology. 146(4):527-532. https://doi.org/10.1017/S0031182018001762.
DOI: https://doi.org/10.1017/S0031182018001762

Interpretive Summary: Varroa destructor mites are harmful ectoparasites of Apis mellifera honey bees. Female mites feed on host fluids from relatively large, open wounds on host’s body surface. Details of V. destructor mite nutrient metabolism are scant, and little is known about the potential physical effects on hosts from mite feeding. Additionally, behaviors of mites are hard to characterize in their natural environment inside wax-capped pupal cells of honey bee colonies. Chemical analysis of animals’ waste excretions can infer details of their nutrition and metabolism; for example, blood-feeding acarines excrete nitrogen-rich and water-saving guanine as metabolic waste. Here, using high performance liquid chromatography coupled mass spectrometry we identified that V. destructor waste excretions consist largely of guanine with smaller amounts of the purine hypoxanthine. Traces of uric acid and caffeine were also detected. Excretions collected from senescing mites did not contain detectable guanine. Individual female mites maintained in vitro, housed in gelatin capsules and provided a honey bee pupa, deposited an average of nearly 18 excretions each day; these were deposited on host’s integument nearly four times as often as on the capsule wall. The volume of total excretions suggest a daily average of nearly one microliter of host tissues consumed per day. Our study indicates that Varroa mite metabolism proceeds at an unexpectedly high rate. Compounded over ten days, this together with open wounds, could amount to a great deal of water loss and stress to developing pupae.

Technical Abstract: Varroa destructor mites (Acari:Varroidae) are harmful ectoparasites of Apis mellifera honey bees. Female foundresses of wax-capped pupal host cells and their daughters feed on host fluids from relatively large, open wounds on host’s integument. Details of V. destructor mite nutrition are elusive, and little is known about the potential physical effects on hosts from mite feeding. Chemical analysis of animals’ waste excretions can infer details of their nutrition; for example, blood-feeding acarines excrete nitrogen-rich and water-saving guanine as metabolic waste. Here, using high performance liquid chromatography coupled mass spectrometry we report that V. destructor waste excretions consist largely of guanine with smaller amounts of the purine hypoxanthine. Traces of uric acid and caffeine were also detected. Excretions collected from senescing mites did not contain detectable guanine. Non-reproducing individual female mites maintained in vitro, housed in gelatin capsules and provided a honey bee pupa, deposited an average of nearly 18 excretions each day; these were deposited on host’s integument nearly four times as often as on the capsule wall. The volume of total excretions suggest a daily average of nearly one microliter of host tissues consumed per day. Compounded over ten days, this together with open wounds, could amount to a great deal of water loss and stress to developing pupae.