Chemical ecology of ticks: olfaction, behaviour, chemistry and control

扁虱是所有食血节肢动物中最广泛的致病生物，其传播对人类和兽医健康具有重要意义的病原体的能力仅次于蚊子。扁虱几乎完全失明，它依靠化学感觉来识别和定位成功的血餐的宿主，与昆虫相比，它的化学感觉系统代表了一个新的前沿。缺乏触角，嗅觉感受器非常少，用于挥发性检测的独特器官(Haller‘s)的发展，位于口腔部位的感受器的多模式作用，使扁虱成为了解粉虱如何检测化学物质的理想系统。主要的化学感受器是位于第一对腿的前额肌上的哈勒氏器。除了检测寄主凯洛酮外，Haller的器官化学感受器被认为参与了信息素、聚集化学物质和环境线索的检测。尽管霍勒氏器官在扁虱的外周感觉系统中起着关键作用，但人们对其在化学感觉中的作用知之甚少。以前的研究证实了它在嗅觉中的作用，但不是味觉，直到最近才有报道称足掌也参与了挥发性物质的检测。这一点很有意义，因为大多数针对扁虱的驱避性测试不区分嗅觉驱避性和触觉化学感受/味觉驱避性。嗅觉感受器能够检测到挥发性分子，有证据表明，嗅觉至少部分参与了扁虱对驱避剂的反应。我的研究计划的长期目标是解决我们对扁虱宿主选择/接受的理解中的关键差距，揭示化学线索感知背后的机制，提供防止扁虱叮咬从而在人和动物中感染的方法。我们将通过研究扁虱嗅觉的神经感觉生理学和化学生态学来实现这一点，以此作为阐明宿主接受/拒绝的化学基础。我的研究计划将通过将气味和化学线索引发的神经生理反应与相应的诱发和观察到的行为联系起来，揭示人/动物-壁虱相互作用背后的动力学。刺激物将包括寄主的挥发物和包括精油在内的天然驱避产品，以及其他具有行为活性的化合物，以确定与寄主附着和驱蚊的相关性。我的研究计划将提供有关壁虱嗅觉敏感度的关键信息，它们对气味的敏感程度，以及对特定天然化合物的驱避活性的行为调查。了解蜱类化学传感的基本生物学对加拿大和全球都很重要，因为它构成了最终设计机制以避免病原体传播的必要平台，这些病原体传播的媒介是疾病，如莱姆病。

Ticks vector the widest array of disease-causing organisms of all hematophagous arthropods and are second only to mosquitoes in their capacity to transmit disease agents of importance to human and veterinary health. Being almost totally blind, ticks rely on chemosensation to identify and locate hosts for a successful blood meal, and the tick chemosensory system represents a new frontier compared with that of insects. The lack of antennae, the presence of very few olfactory sensilla, the development of a distinctive organ (Haller's) used for volatile detection, the multimodal role of sensilla located on mouth parts, make ticks an ideal system for understanding how acarines detect chemicals. The main chemosensory organ is represented by the Haller's organ, located on the foretarsus of the first pair of legs. Other than detecting host kairomones, Haller's organ chemoreceptors are suggested to be involved in the detection of pheromones, aggregation chemicals, and environmental cues. Despite the pivotal role of the Haller's organ in the tick peripheral sensory system, little is known about its function in chemosensation. Previous studies confirmed its role in olfaction but not gustation, and only recently pedipalps have been reported to be involved in volatile detection as well. This is significant because most repellency assays for ticks do not discriminate between repellency due to olfaction versus that from tactile chemoreception/gustation. Olfactory sensilla are able to detect volatile molecules, and evidence suggests that olfaction is involved at least, in part, in tick responses to repellents. The long-term objective of my research program is to address critical gaps in our understanding of tick host selection/acceptance, unveiling the mechanisms behind chemical cue perception, providing means to prevent tick bites and thus infections in humans and animals. We will achieve this by studying the neuro-sensory physiology and chemical ecology of tick olfaction as a basis for elucidating the chemistry of host acceptance/rejection. My research program will unveil the dynamics behind human/animal-tick interactions by linking the neurophysiological response elicited by odorants and chemical cues with the corresponding induced and observed behaviour in ticks. Stimuli will include volatiles of hosts and natural repellent products including essential oils, and other behaviourally-active compounds, to determine relevance in host attachment and tick repellency. My research program will provide critical information regarding olfactory sensitivity in ticks, the odorant repertoire to which they are sensitive, and behavioural investigations of the repellent activity of specific natural compounds. Understanding the fundamental biology of tick chemosensation is important to Canada and globally as it forms the necessary platform to ultimately devise mechanisms to avoid the transmission of pathogens that vector diseases, like Lyme disease.