Please use this identifier to cite or link to this item: https://hdl.handle.net/20.500.14279/3415
Title: Monitoring the gravitational reflex of the ectoparasitic mite Varroa destructor: A novel bioassay for assessing toxic effects of acaricides
Authors: Papachristoforou, Alexandros 
Papaefthimiou, Chrisovalantis 
Zafeiridou, Georgia 
Goundy, Vasiliki 
Watkins, Max 
Theophilidis, George 
Major Field of Science: Agricultural Sciences
Field Category: AGRICULTURAL SCIENCES
Keywords: Acaricides;Gravitational reflex;Leg flexion;Mortality assessment;Sternum expansion;Varroa destructor
Issue Date: Oct-2011
Source: Pesticide Biochemistry and Physiology, 201, vol. 101, no. 2, pp. 109-117
Volume: 101
Issue: 2
Start page: 109
End page: 117
Journal: Pesticide Biochemistry and Physiology 
Abstract: We investigated the effect of several acaricides on Varroa destructor by monitoring the rhythmic expansion of the sternum, followed by a strong flexion of the legs, initiated when the mite was placed in a dorsal side-down position, as an indication of a mite's vitality. The pulses generated by the force of the rhythmic expansions had an average duration of 3.11 s, force (amplitude) of 73 mu N, and frequency of 0.228 Hz. These parameters remained constant for the first 10 h of recording, whilst significant changes occurred after 15 h. The rhythmic sternal expansion is an indication of a Varroa mite's gravitational reflex, or attempt to return to an upright position, this reflex is observed in all invertebrates and vertebrates. The sternal expansion can be recorded for over 20 h, or for as long as the Varroa mite remains alive, and the expansion stops as soon as the mite is placed in a normal, upright position. Proper function of the chain of proprioceptors, interneurons, motorneurons, neuromuscular junctions, and muscles of Varroa is required for the initiation and maintenance of such a behavioural motor pattern. Any deleterious effect of synthetic chemicals or natural compounds (acaricides) may have a direct effect on one or more of these links, thereby disturbing or even inhibiting the reflex. Topical application of 1.81 x 10(-3) mg/mite of amitraz completely inhibited the gravitational reflex within 60-70 min for all mites tested. The volatile acaricides formic acid (13.83 mg), thymol crystals (250 mg), and Apiguard (R) (1000 mg) eliminated the reflex within 10-35 min. This bioassay, based on the gravitational reflex, could be a useful tool for accurate assessment of the acaricidal action of numerous compounds under laboratory conditions, saving money and time necessary to conduct field trials. (C) 2011 Elsevier Inc. All rights reserved.
URI: https://hdl.handle.net/20.500.14279/3415
ISSN: 10959939
Other Identifiers: ISSN : 0048-3575
DOI: 10.1016/j.pestbp.2011.08.008
Rights: © Elsevier
Type: Article
Affiliation : Aristotle University of Thessaloniki 
Avenue de la Terrasse 
Cyprus University of Technology 
Vita (Europe) Limited 
Publication Type: Peer Reviewed
Appears in Collections:Άρθρα/Articles

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