Abstract
Feeding behaviors and biomechanics of female Varroa destructor mites are revealed from AC-DC electropenetrography (EPG) recordings of mites feeding from Apis mellifera honey bee pupae and histology of mite internal ingestion apparatus. EPG signals characteristic of arthropod suction feeding (ingestion) were identified for mites that fed on pupae during overnight recordings. Ingestion by these mites was confirmed afterwards by observing internally fluorescent microbeads previously injected into their hosts. Micrographs of internal ingestion apparatus illustrate the connection between a gnathosomal tube and a pharyngeal lumen, which is surrounded by alternating dilator and constrictor muscles. Inspection of EPG signals showed the muscularized mite pharyngeal pump operates at a mean repetition rate of 4.5 cycles/s to ingest host fluids. Separate feeding events observed for mites numbered between 23 and 33 over approximately 16 h of recording, with each event lasting ~10 s. Feeding events were each separated by ~2 min. Consecutive feeding events separated by either locomotion or prolonged periods of quiescence were grouped into feeding bouts, which ranged in number from one to six. Statistical analyses of EPG data revealed that feeding events were prolonged for mites having lower pharyngeal pump frequencies, and mites having prolonged feeding events went unfed for significantly more time between feeding events. These results suggest that mites may adjust behaviors to meet limitations of their feeding apparatus to acquire similar amounts of food. Data reported here help to provide a more robust view of Varroa mite feeding than those previously reported and are both reminiscent of, as well as distinct from, some other acarines and fluid-feeding insects.
Highlights
The parasitiform mite Varroa destructor, hereafter Varroa mite, is an obligate ectoparasite of both Apis cerana Fabricius and A. mellifera Linnaeus honey bees
Evidence of mite locomotion or periods of quiescence greater or equal to 300 s were metrics used for grouping feeding events into separate feeding bouts
In this study the feeding behaviors and biomechanics of fluid ingestion were described for Varroa mites on honey bee host pupae
Summary
The parasitiform mite Varroa destructor, hereafter Varroa mite, is an obligate ectoparasite of both Apis cerana Fabricius and A. mellifera Linnaeus honey bees. Fluids are accessed through a hole made by mites in soft portions of the host’s integument using paired, movable toothed digits of chelicerae, together with paired elongated corniculi having sharpened, serrated ventral edges, suitable for slicing though soft bee cuticle (De Lillo et al, 2001). The shapes of both the paired structures form internal concavities that, when pressed together, form a channel suitable for transferring host fluids internally (Ramsey et al, 2018).
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