University of Hohenheim, Apicultural State Institute, 70593 Stuttgart, Germany.
J Invertebr Pathol. 2013 May;113(1):56-62. doi: 10.1016/j.jip.2013.01.007. Epub 2013 Jan 30.
The reproductive cycle of the parasitic mite Varroa destructor is closely linked to the development of the honey bee host larvae. Using a within colony approach we introduced phoretic Varroa females into brood cells of different age in order to analyze the capacity of certain stages of the honey bee larva to either activate or interrupt the reproduction of Varroa females. Only larvae within 18 h (worker) and 36 h (drones), respectively, after cell capping were able to stimulate the mite's oogenesis. Therewith we could specify for the first time the short time window where honey bee larvae provide the signals for the activation of the Varroa reproduction. Stage specific volatiles of the larval cuticle are at least part of these activation signals. This is confirmed by the successful stimulation of presumably non-reproducing mites to oviposition by the application of a larval extract into the sealed brood cells. According to preliminary quantitative GC-MS analysis we suggest certain fatty acid ethyl esters as candidate compounds. If Varroa females that have just started with egg formation are transferred to brood cells containing host larvae of an elder stage two-thirds of these mites stopped their oogenesis. This confirms the presence of an additional signal in the host larvae allowing the reproducing mites to adjust their own reproductive cycle to the ontogenetic development of the host. From an adaptive point of view that sort of a stop signal enables the female mite to save resources for a next reproductive cycle if the own egg development is not sufficiently synchronized with the development of the host. The results presented here offer the opportunity to analyze exactly those host stages that have the capacity to activate or interrupt the Varroa reproduction in order to identify the crucial host signals.
寄生螨瓦螨的生殖周期与蜜蜂幼虫的发育密切相关。我们采用巢内方法，将寄生的瓦螨雌螨引入不同日龄的幼虫巢房中，以分析特定龄期的蜜蜂幼虫是激活还是中断瓦螨雌螨的繁殖能力。只有在封盖后 18 小时（工蜂）和 36 小时（雄蜂）内的幼虫才能刺激螨虫的卵发生。由此，我们首次明确了蜜蜂幼虫提供激活瓦螨繁殖信号的短暂时间窗口。幼虫角质层的特定挥发物至少是这些激活信号的一部分。这一点通过将幼虫提取物应用于密封的巢房中成功刺激推测为非繁殖的螨虫产卵得到了证实。根据初步的定量 GC-MS 分析，我们提出了某些脂肪酸乙酯作为候选化合物。如果刚刚开始产卵的瓦螨雌螨被转移到含有龄期较大的幼虫的巢房中，其中三分之二的螨虫会停止产卵。这证实了在宿主幼虫中存在另一种信号，允许繁殖的螨虫根据宿主的个体发育来调整自身的生殖周期。从适应的角度来看，如果自身的卵发育与宿主的发育不同步，这种停止信号使雌螨能够为下一个生殖周期节省资源。这里提出的结果为分析那些具有激活或中断瓦螨繁殖能力的宿主阶段提供了机会，以确定关键的宿主信号。
