Regular dorsal dimples onVarroa destructor– Damage symptoms or developmental origin?

Abstract

-Adult females (n = 518) of Varroa destructor from Apis mellifera prepupae were examined by scanning electron microscopy without prior fluid fixation, dehydration and critical-point drying. Fifty-five (10.6%) mites had one (8.1%) or two (2.5%) diagonal dimples positioned symmetrically on the idiosoma's dorsum. Where one such regular dorsal dimple existed per mite body, it occurred on the left or right side, equally. Mites with at least one regular dorsal dimple were 3.4% longer, but neither idiosomal width nor elliptical area differed significantly from mites lacking dimples. Dimple length was normally distributed in the population, and averaged 462 ± 9.2 μm (s.e.; n = 68 dimples). Internally, each regular dorsal dimple aligns with a series of obliquely-situated, dorso-ventral muscles in the opisthosoma. It is concluded that regular dorsal dimples are faults originating during mite ontogeny and should be considered separately from damage to Varroa destructor inflicted by honeybees or predatory arthropods.developmental fault / idiosoma / regular dorsal dimple / scanning electron microscopy / Varroa destructor

A scientific note on a new assay to measure honeybee mite-grooming behavior

“…Mites were considered to be chewed if they were missing legs or parts of legs, or if they had a part of the outer edge of the idiosoma missing. These mutilations are easy to differentiate from the "dorsal dimples" that were described by Davis (2009). These counts were done approximately 1 month after the lab assay.…”

Adaptation in Honey Bee (Apis mellifera) Colonies Exhibiting Tolerance to Varroa destructor in Ireland

“…Damage to mites may be contributing to this tolerance. Also, it has been shown that one or two regular dorsal dimples can occur on the mite's idiosoma that can be considered as "defects" rather than "damage" caused by the bees (Davis, 2009). A study by Lodesani, Vecchi, Tommasini, and Bigliardi (1996) showed that the presence of these regular dorsal dimples in the mother mite resulted in a 35.5% absence of first daughters compared with a 14.5% absence when no dimple defect was present.…”

“…The mites were listed as live or dead, and condition was listed as intact, damaged idiosoma or damaged legs. Mites with one or two regular dorsal dimples are not considered as damaged (Davis, 2009). The majority of the mites in the natural mite-fall were dead and damage was observed on 44% of them.…”

The effect of the ‘Bee Gym™’ grooming device on Varroa destructor mite fall from honey bee (Apis mellifera) colonies

“…Mites were classed as damaged if they had missing legs or mouthparts or if there were sections of the dorsal shield (idiosoma) or ventral shield missing. Mites with a dented idiosoma were not included as damaged as this has been shown to be ontological (Davis, 2009). All living mites were included in the undamaged category.…”