Summary — The proportion of damaged Varroa mites within the debris of honey bee colonies is discussed as a possible tolerance factor of the host. We investigated the rate of damaged Varroa females in honey bee colonies with and without hatching brood. Additionally, in some colonies sealed brood combs were treated by the use of heat or formic acid to kill the mites within the brood cells to quantify the behaviour of the bees towards dead mites. In 17 experimental honey bee colonies (Apis mellifera) at two different study sites, the debris was checked at 12-h intervals. Nearly 5 000 mites were individually analyzed for three different types of damages. The percentage of damaged mites varied on average from 44 to 63% depending on experimental conditions. No significant differences in the damage rates of 'phoretic mites' and 'brood mites' could be found. Dead mites from the treated brood combs were damaged to a slightly lesser extent. The significance of these results for the use of the parameter 'damaged mites' in selection programs is discussed.
-A whole mount method was used to determine the moment of activation of oocyte growth in Varroa jacobsoni females. Ovaries of the mites were dissected and stained with toluidine blue. The coloration of the terminal oocyte indicates the uptake of euplasmatic and/or yolk material and, therefore, the initiation of the reproductive phase. In phoretic mites from adult bees, no staining of the ovary could be detected. V. jacobsoni females artificially introduced into freshly capped brood cells and removed for dissection 6 h later already showed clear blue staining of the terminal oocyte. The ovaries of V. jacobsoni females introduced 14 h after capping of the brood cell, however, remained uncolored after incubation in toluidine blue. We conclude that, in phoretic mites, oogenesis is arrested at a previtellogenic phase. Immediately after invasion of the brood cell, reproduction is activated by an as yet unknown host factor. This factor is present in freshly capped brood cells but not in brood cells 14 h after capping. Our new method offers new possibilities for the exact determination of oocyte growth and, therefore, for the study of V. jacobsoni fertility in different host and parasite populations. Varroa jacobsoni / host-parasite relationship / vitellogenesis / oogenesis / fertility / reproductionApidologie 31 (2000) 559-566 559
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