Fig 1.
Schematic representation of the experimental design applied to the three hives.
Mites experience a different phoretic phase and are then transferred onto spinning larvae to pursue their reproductive cycle in laboratory conditions. Numbers correspond to the moments when mites were sampled to conduct molecular analyses: (i) before the beginning of the phoretic phase; (ii) immediately after the phoretic phase; (iii) three days after the transfer on spinning larvae, at which point the bee is in the last stage of the pharate pupal (or prepupal) period (PP3); (iv) ten days after the transfer on spinning larvae corresponding to the medium pigmented body pupal stage (pbm) for the bees; (v) at the emergence of the bee.
Table 1.
Survival of the bees and reproductive parameters of the Varroa, and comparison with previous in vitro or in naturae studies.
Numbers correspond to frequencies of observation, with the exception of fully molted daughters.
Fig 2.
Reproductive parameters of mites in relation to the treatment and emergence success of the bee.
A) Oviposition proportion and percentage of cells with at least one mature daughter per foraging condition. Bars show the overall rate ± IC95 (not significant). B) Mean numbers of fully molted daughters in relation to the emergence success of the bee. Mean±SE Non molted (n = 11), imago stage (n = 113).
Fig 3.
Vitellogenin gene expression from mites in relation with the three treatments.
Within stage log-transformed normalized absolute expression of two vitellogenin transcripts of mites that experienced distinct phoretic conditions: mites that spent 3 days on forager bees, mites that stayed 3 days on nurse bees, mites that spent 7 days on nurse bees. The stages of the parasite cycle are: pre = prephoretic, mites randomly extracted from brood cells containing different stages of honey bee development and ready to be transferred onto adults; postphoretic, mites sampled right after their stay on adult bees in experimental cages; PP3, Prepupal stage mites; pbm, parasites sampled on brown eyed, medium pigmented thorax honey bee pupae; emerging, parasites on the day of honeybee emergence; daughter, newly fully molted Varroa distinguishable from the mothers. Only the statistical significance for phoretic condition is showed NS = non significant (ANOVA model and post hoc comparisons).
Fig 4.
Expression of two vitellogenin genes from mites at different times of the development.
A) Normalized absolute expression of the two vitellogenin transcripts at different stages of the parasite cycle, the labels are similar to Fig 3: prephoretic, before the transfer onto adults; postphoretic, after the stay on adult bees; PP3, on prepupal bees; pbm, on brown eyed, medium pigmented thorax honey bee pupae; emerging mites; daughter. Barplot of the mean ± standard error: capital letters indicate the significant differences in the VdVg1 expression, small letters the significance of statistical tests for the VdVg2 expression (ANOVA model and post hoc compaisons pBonferroni<0.003). B) Focus on the normalized absolute expression of the two VdVg transcripts of newly born Varroa females after division into two groups according to their age: older daughters (= dpd: darkly pigmented daughters) and younger daughters (= lpd: lightly pigmented daughters). Letters showed the significance of the Mann-Whitney-Wilcoxon test conducted on VdVg1 (capital letter) and VdVg2 (small letter) pBonferroni<0.0083.
Fig 5.
Malformation of bees in relation with the phoretic treatment.
A) Proportion of emerging bees with malformations in relation to the phoretic conditions of the Varroa they have been parasitized with. Mites that had longer phoretic phase lead to more deformations. Letters shows significant differences analyzed by a GLM model (p<0.001). B) Examples of the most common deformities observed in emerging honeybees: i) atrophy of wings pigmentation anomaly; ii) deformity of wings; iii) atrophy of wings, dark pigmentation.
Fig 6.
Log-transformed absolute quantification of Deformed Wing Virus (normalized by the expression of Actin).
A) In mites sampled on newborn bees in relation to the presence of malformation of the bee (p-value from a Mann Whitney-Wolcoxon test). B) In all mites in relation to the previous phoretic experience of these mites. Significant differences from the ANOVA models and post hoc comparisons are indicated with letters.