Neuronal Mechanisms Mediating Prey Pursuit Behaviour in Predatory Flying Insects

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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.