Mechanosensory interactions drive collective behaviour in Drosophila

摘要

成群的鱼、成群的鸟和成群的人都能增强群体内个体的感知和决策能力，但其中所涉及的神经机制却一直难以确定。Richard Benton及同事采用一个更容易操作的模型来研究群体行为：他们发现，单个果蝇的弱气味躲避行为在果蝇群中可以得到增强，这是由于成对果蝇之间存在着由"附器碰触"相互作用构成的级联。通过识别其中所涉及的机械传导神经元和离子通道，作者为对动物群体中的集体行为进行神经回路解析研究打开了大门。%Collective behaviour enhances environmental sensing and decisionmaking in groups of animals. Experimental and theoretical investigations of schooling fish, flocking birds and human crowds have demonstrated that simple interactions between individuals can explain emergent group dynamics. These findings indicate the existence of neural circuits that support distributed behaviours, but the molecular and cellular identities of relevant sensory pathways are unknown. Here we show that Drosophila melanogaster exhibits collective responses to an aversive odour: individual flies weakly avoid the stimulus, but groups show enhanced escape reactions. Using high-resolution behavioural tracking, computational simulations, genetic perturbations, neural silencing and optogenetic activation we demonstrate that this collective odour avoidance arises from cascades of appendage touch interactions between pairs of flies. Inter-fly touch sensing and collective behaviour require the activity of distal leg mechanosensory sensilla neurons and the mechanosensory channel NOMPC. Remarkably, through these inter-fly encounters, wild-type flies can elicit avoidance behaviour in mutant animals that cannot sense the odour-a basic form of communication. Our data highlight the unexpected importance of social context in the sensory responses of a solitary species and open the door to a neural-circuit-level understanding of collective behaviour in animal groups.