Toluidine blue staining as a rapid measure for initiation of oocyte growth and fertility inVarroa jacobsoniOud

Abstract

-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

Biology and control of Varroa destructor

“…Approximately 5 h after cell capping the larvae has consumed the rest of the larval food (Ifantidis et al, 1988) and the mite sucks hemolymph from the larva. Within a few hours oogenesis starts, followed by vitellogenesis (Garrido et al, 2000;Steiner et al, 1994Steiner et al, , 1995 and approximately 70 h after the cell capping the first egg is laid (Ifantidis, 1983;Steiner et al, 1994).…”

“…During the phoretic phase the oocytes are arrested in a previtellogenic stage (Garrido et al, 2000). Immediately after the invasion of the brood cell the oogenesis is activated by volatiles of the host larva (Garrido and Rosenkranz, 2004;Milani and Chiesa, 1990;Trouiller and Milani, 1999).…”

Reproductive biology of Varroa destructor in Africanized honey bees (Apis mellifera)

“…However, many mites go through these cycles, feed on the pupae, but do not reproduce. It is not well known which components of the diet of the mites are responsible for inducing oogenesis (triggering the activation of oocyte maturation of the mite) (Garrido et al 2000). Oocyte growth in reproductive varroa females depends on the consumption of haemolymph from freshly sealed larvae (Donzé and Guerin 1994).…”

Visualisation by vital staining with trypan blue of wounds punctured by Varroa destructor mites in pupae of the honey bee (Apis mellifera)

“…Because of its ease in handling, fast results, and highly reliable detection of wounds used as feeding sites by haemolymphsucking mites in their reproductive phase, our new method can be recommended for various purposes. In particular, this low-cost technique could be established in all laboratories involved in varroosis research on parasite-host relationships (Garrido et al, 2000(Garrido et al, , 2001). An important advantage is that the vital staining seemed to cause no harm to the pupae as they survived and could develop into imagoes and, therefore, be used for subsequent experiments and analyses.…”

“…Oogenesis and subsequent oviposition depend on repeated haemolymph meals taken by female mites, beginning shortly after capping of the brood cell (Steiner et al, 1994;Garrido et al, 2000). For this purpose, the mites perforate the integument of the host bee.…”