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Title: Using an in vitro system for maintaining Varroa destructor mites on Apis mellifera hosts: Studies of mite longevity and feeding behavior

item Egekwu, Noble
item SONENSHINE, DANIEL - Volunteer
item POSADA, FRANCISCO - Oak Ridge Institute For Science And Education (ORISE)
item Cook, Steven

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2018
Publication Date: 3/6/2018
Citation: Egekwu, N.I., Sonenshine, D.E., Posada, F., Cook, S.C. 2018. Using an in vitro system for maintaining Varroa destructor mites on Apis mellifera hosts: Studies of mite longevity and feeding behavior. Experimental and Applied Acarology. 74:301-315.

Interpretive Summary: Varroa destructor is a harmful ectoparasitic mite of Apis mellifera honey bees. The damage they inflict is believed by many to be a major cause of the ongoing decline in the health of honey bee colonies. Honey bees, and the pollination services they provide, are essential for maintaining food security in the U.S and rest of the world. Much research has been dedicated to eradicating Varroa mites, but is hindered by the peculiar requirements of mites that make it difficult to study the biology of these mites in the laboratory. Mites only live hours without access to their host, typically a honey bee pupa, and methods are lacking for maintaining mites on natural hosts in the lab for research purposes. In this study, we describe a device and protocol (i.e., system) for maintaining Varroa mites on live honey bee pupae to study mite biology, and interactions between mites and their honey bee hosts. Additionally, we report results from experiments using this system to study mite longevity and feeding behavior. Using the system, that used this system to Using the system to study mite longevity and feeding behavior. Mites lived two weeks on average, significantly longer than any previous in vitro study of Varroa mites. Mites preferred to feed from the pupa's abdomen and thorax, but could feed from many different body parts, including from the host's eye. Feeding site preference may indicate the dietary needs of the mites, but also illustrates the flexibility of mites in where from host's body they may garner necessary nutrients for survival. This flexibility may be adaptive for when mites are in crowded and cramped pupal cells inside honey bee hives. We believe this system will be adopted for Varroa mite research in a number of different laboratories.

Technical Abstract: Varroa destructor mites (Vd) are ectoparasites of Apis mellifera honey bees, and the damage they inflict on hosts is a likely causative factor of recent poor honey bee colony performance. Much research has produced an arsenal of control agents against Vd, which have become resistant to many chemical means of their control, and other means have uncertain efficacy. Novel means of control will result from a thorough understanding of Vd physiology and behavior. However, robust knowledge of Vd biology is lacking; mites have very low survivability and reproduction away from their natural environment and host, and few tested protocols of maintaining mites in vitro are available as standardized methods to researchers for in vitro Vd research. Here, we describe the ‘Varroa Feeding System’ (VFS), a tool for maintaining populations of Vd on its natural host in vitro, and present best practices for its use in Vd and host research. Additionally, we present results using the VFS from research of Vd and host longevity, Vd feeding behavior, and instances of reproduction. Under these conditions, mites had high survivability, living 14 days on average. For feeding, female mites inflicted wounds on a wide range of sites on the host’s integument, but preferred to feed from areas of the host’s abdomen and thorax. Originally phoretic-phase, female mites in VFS had limited reproduction, but positive instances give insights into cues necessary for reproduction. The VFS could be a useful tool for laboratory studies requiring long-term survival of mites, for example.