Neuronal Mechanisms Mediating Prey Pursuit Behaviour in Predatory Flying Insects

掠食性飞虫进化出了不同的神经元专一化，以解决有效捕获快速飞行猎物的任务。蜻蜓的视叶中有一个小目标运动探测器系统，其功能是将猎物与视觉环境区分开来（Nordstrom, 2012）。这些神经元被认为将猎物的位置和速度信息传递给腹侧索中的一小群目标选择性下降神经元（tsdn），以引导蜻蜓沿着拦截飞行（Olberg, 1986； Gonzalez-Bellido等人，2013）。然而，tsdn在大脑中接收的输入和触发追求启动的机制仍未被探索。与蜻蜓类似的神经系统被假设存在于其他掠食性昆虫中，它们执行类似的捕获猎物的任务。例如，进化上距离较远的双翅目杀人蝇（Coenosia attenuata）采用的空中狩猎策略与蜻蜓有许多相似之处，尽管受到不同的生理和生态限制（Gonzalez-Bellido et al., 2011; Wardill et al., 2015）。另一方面，蜻蜓的姐妹类豆娘经常从悬停的位置抓取静止的猎物，这种行为被称为拾取（Yee et al., 2012）。这两个群体是否使用与蜻蜓相似的感觉运动控制系统尚不清楚。通过比较这三个分类群在下行神经元水平上的行为和神经元特化，我们将研究蜻蜓TSDN系统的收敛（杀蝇）和/或保守（豆豆蝇）特征是否存在于其他掠食性空中无脊椎动物中。这些发现将有助于阐明与控制拦截行为有关的一般设计原则；此外，任何特殊的属性都可能突出特定生态位的特征。总的来说，本博士的重点是从三个方面扩展对捕食性飞行昆虫在tsdn水平上的感觉运动转换的理解：1。识别具有不同生理和行为生态位的三种不同物种的目标选择性下行神经元系统的一般和/或特殊特征2。利用蜻蜓tsdn的既定知识以及双翅目物种的神经解剖学数据，描述中枢大脑对tsdn的输入。研究关于猎物的感官信息与发起攻击的决定相结合的机制，利用在实验室中控制杀人蝇的狩猎历史的能力作为一种行为关联。

Various neuronal specialisations have evolved in predatory flying insects to solve the task of efficiently capturing fast flying prey. In dragonflies, a system of small target movement detectors in the optic lobes function to discriminate prey items from the visual surroundings (Nordstrom, 2012). These neurons are thought to transduce information about prey position and velocity to a small population of target selective descending neurons (TSDNs) in the ventral cord to steer the dragonfly along an intercepting flight (Olberg, 1986; Gonzalez-Bellido et al., 2013). However, the input received by TSDNs in the brain and the mechanism triggering the initiation of pursuit has remained unexplored. Analogous neuronal systems to those in dragonflies are hypothesised to exist in other predatory insects which perform the similar task of catching prey. For example the evolutionarily distant dipteran killer fly (Coenosia attenuata) employs an aerial hunting strategy that shares many parallels with that of dragonflies, albeit under different physiological and ecological constraints (Gonzalez-Bellido et al., 2011; Wardill et al., 2015). Damselflies on the other hand, a sister group to dragonflies, often snatch stationary prey from a hovering position, a behaviour termed gleaning (Yee et al., 2012). Whether these two groups employ similar sensorimotor control systems to those identified in dragonflies is unknown. By comparing the behaviour and neuronal specialisations at the level of descending neurons in these three taxa, we will investigate if convergent (killer fly) and/or conserved (damselfly) features of the dragonfly TSDN system are present in other predatory aerial invertebrates. Such findings will serve to elucidate general design principles relevant for controlling intercepting behaviour; in addition, any idiosyncratic properties may highlight features specialised for a given ecological niche. Overall, the focus of this PhD is to extend understanding of the sensorimotor conversion at the level of TSDNs in predatory flying insects in three ways: 1. Identify generalised and/or idiosyncratic features of target selective descending neuron systems across three different species with varying physiology and behavioural niches2. Characterise the input to TSDNs in the central brain, making use of the established knowledge for dragonfly TSDNs in addition to the neuroanatomical data available for dipteran species3. Investigate mechanisms in which sensory information about prey is integrated with a decision to initiate an attack, making use of the ability to control the killer fly's hunting history in the laboratory as a behavioural correlate.