Impact of the phoretic phase on reproduction and damage caused by Varroa destructor to the European Honey Bee. raw_data.xlsx

We investigated if the type of bees on which Varroa stays during the phoretic phase and if the duration of this stay influenced the reproductive success of the parasite and the damage caused to bees. For that purpose, we used an in vitro rearing method developed in our laboratory to assess egg laying rate and the presence and number of fully molted daughters. The expression level of two Varroa vitellogenin genes (VdVg1 and VdVg2), known to vary throughout reproduction, was also quantified. Results showed that the status of the bees or time spent during the phoretic phase impacts neither reproduction parameters nor the Varroa vitellogenin genes levels of expression. However, we correlated these parameters to the gene expression and demonstrated that daughters expressed the vitellogenin genes at lower levels than their mother. Regarding the damage to bees, the data indicated that a longer stay on adult bees during the phoretic phase resulted in more frequent physical deformity in newborn bees. We showed that those mites carry more viral loads of the Deformed Wing Virus and hence trigger more frequently overt infections. This study provides new perspectives towards a better understanding of the Varroa-honeybee interactions.

本研究旨在探究瓦螨（Varroa）在携播期（phoretic phase）所寄生的蜜蜂种类，以及该阶段的停留时长，是否会影响该寄生生物的繁殖成功率及其对蜜蜂造成的危害。为此，我们采用实验室自主开发的体外饲养法，对瓦螨的产卵率以及完全蜕皮子代瓦螨的存在情况与数量进行了评估。此外，我们还定量检测了两个已知会随繁殖过程动态变化的瓦螨卵黄蛋白原基因（VdVg1和VdVg2）的表达水平。研究结果显示，蜜蜂的状态或瓦螨在携播期的停留时长，既不会影响该寄生生物的繁殖参数，也不会改变其卵黄蛋白原基因的表达水平。不过，我们将上述参数与基因表达量进行关联分析后证实，子代瓦螨的卵黄蛋白原基因表达水平显著低于其母代。针对蜜蜂所受危害的分析结果表明，瓦螨在成年蜜蜂体内的携播停留时长越长，新生蜜蜂出现身体畸形的概率越高。我们进一步发现，此类瓦螨携带的畸形翅病毒（Deformed Wing Virus）载量更高，因此更易引发宿主出现显性感染。本研究为深入解析瓦螨与蜜蜂的互作关系提供了全新的视角。