Regular dorsal dimples on Varroa destructor – Damage symptoms or developmental origin?Arthur R. Davis
Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan, Canada S7N 5E2
Received 6 June 2008 – Revised 29 October 2008 – Accepted 18 November 2008 - Published online 13 February 2009
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 m (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.
Key words: developmental fault / idiosoma / regular dorsal dimple / scanning electron microscopy / Varroa destructor
© INRA, DIB-AGIB, EDP Sciences 2009