Elucidating the regulation of reproduction in Varroa mites: uncovering potential control strategies.

农作物的昆虫授粉对粮食生产绝对至关重要，据估计全球每年的价值为3610亿美元。蜜蜂（Apis mellifera）正在经历严重的蜜蜂健康危机，威胁着全球粮食安全。美国蜂群每年的巨大损失（2012/13、2013/14和2015/16年分别为45%、34%和40%）现在与欧洲类似的损失相当。蜜蜂健康状况被认为是蜜蜂不可持续损失的关键。虽然蜜蜂健康危机的原因是多因素的，但人们普遍认为，外部寄生虫瓦螨（瓦螨破坏者）及其病毒病原体的传播是蜜蜂群体损失的主要原因之一，如果不是的话。由于对全球粮食生产的影响，瓦氏病可以说是任何物种中最严重的牲畜疾病。尽管瓦罗亚的重要性毋庸置疑，但相对于它的重要性，我们对其生理学的了解可能被认为是初级的。由于缺乏人工饲养和饲养系统，瓦罗阿虫研究的进展受到严重阻碍，该系统将为研究人员提供足够数量的常年一致的瓦罗阿虫，并为研究瓦罗阿虫的生理、繁殖、疾病传播以及开发和测试新的控制策略提供理想的实验系统。我们最近为瓦罗亚开发了一种人工喂养系统，远远超过了现有的任何一种。随后，我们成功地在人工喂养系统中诱导瓦氏小蜂产卵，方法是将它们暴露在蜜蜂幼虫或激素处理过的蛹的气味线索中，而不是暴露在标准蛹的气味线索中。这些卵孵化并发育成成虫。我们现在需要利用这些初步发现，更好地了解varroa繁殖的基本原理，使我们的人工饲养系统完全演变为人工饲养系统。为此目的，该项目的总体目标是了解瓦罗阿的繁殖控制，并评估这些信息是否可以用作控制措施。通过分析幼虫、蛹和经激素处理的幼虫蛹散发的挥发性化合物，并应用差分化学计量学方法，我们将化学表征“产卵激素”（OK）的成分。采用生物测定和化学分析相结合的方法研究幼虫挥发物或OK对varroa诱导产卵、卵的性别和停止产卵的影响。幼激素在蜜蜂幼虫产生这些生物活性挥发物或OK中的作用将被阐明。我们将研究varroa是否用它的腿探测到这种来自蜜蜂幼虫的气味线索，以及这种信号是否通过神经内分泌因子诱导性激素的产生（外体类固醇）在varroa中产卵。通过化学分析和生物试验确定人工饲养系统中诱导varroa产卵所需的幼虫挥发物或OK的最佳浓度，并在此浓度范围内制定合适的输送方法。法国、瑞典和德国的一些蜜蜂品种表现出一种被称为“抑制螨虫繁殖”的特征，通过这种特征，瓦螨减少了繁殖。通过进行产卵生物测定和化学分析，我们将验证幼虫挥发物或OK水平的改变是这些蜜蜂品系上瓦螨繁殖减少的基础的假设。最后，我们将评估幼虫挥发物或OK是否能在不适当的情况下（如在成年蜜蜂身上）诱导瓦roa产卵。

Insect pollination of crops is absolutely critical to food production with an estimated annual global value of $361 billion. Honey bees (Apis mellifera) are undergoing a serious bee health crisis threatening global food security. Huge annual losses of bee colonies in the US (45%, 34%, 40% in 2012/13, 2013/14 and 2015/16) are now being matched by similar losses in Europe. The status of bee health is recognised as critical with unsustainable losses of bees. Though the cause of the bee health crisis is multifactorial, it is generally accepted that the external parasite varroa mite (Varroa destructor) and its transmission of viral pathogens is one of, if not the, major cause of honey bee colony loss. Because of the impact on global food production, varroosis is arguably the most serious disease of livestock in any species.Despite varroa's unquestionable significance, our understanding of its physiology could be considered rudimentary relative to its importance. Progress in varroa research is substantially hampered by the lack an artificial feeding and rearing system which would supply researchers with adequate numbers of consistent varroa year round and provide an ideal experimental system for studying varroa physiology, reproduction, disease transmission and the development and testing of new control strategies. We have recently developed an artificial feeding system for varroa that far exceeds any currently available. Subsequently, we succeeded in inducing varroa in the artificial feeding system to lay eggs by exposing them to the odour cues from either bee larvae or hormone-treated pupae, but not from standard pupae. These eggs hatched and developed through to adult varroa. We now need to capitalize on these initial findings and better understand the fundamentals of varroa reproduction to allow our artificial feeding system to fully evolve into an artificial rearing system.To this end, the overall aim of the project is to understand the control of reproduction in varroa and assess if this information could be utilised as a control measure. By analysing the volatile compounds emanating from cohorts of larvae, pupae and juvenile hormone-treated pupae and applying a differential chemometrics approach, we will chemically characterize components(s) of the "Oviposition Kairomone" (OK). The effect of the larval volatiles or OK on induction of oviposition, the gender of the egg and cessation of egg laying in varroa will be studied by a combination of bioassay and chemical analysis. The role of juvenile hormone in the production of these bioactive volatiles or OK by bee larvae will be elucidated. We will investigate if the varroa detects this odour cue from the bee larvae with its legs and if this signal causes egg laying in varroa through induced sex hormone production (ecdysteroids) via a neuroendocrine factor. The optimum concentration of larval volatiles or OK required to induce varroa egg laying in the artificial rearing system will be determined by chemical analysis and bioassay and then a suitable method for delivery of that concentration range developed.There are strains of bees in France, Sweden and Germany exhibiting a trait termed "Suppressed Mite Reproduction" by which varroa have reduced reproduction. By performing the oviposition bioassay and chemical analysis, we will test the hypothesis that altered levels of larval volatiles or OK are the basis for the reduced varroa reproduction on these bee strains. Finally, we will assess if larval volatiles or OK can induce varroa to lay eggs even when in an inappropriate scenario such as while on adult bees.