Dynamics and origins of socially induced plasticity of behaviour

沙漠蝗虫是臭名昭著的害虫，周期性地破坏庄稼和牧场，造成相当大的人力和经济代价。与其他蝗虫不同，蝗虫可以在两种截然不同的形式之间可逆地变化，其中一种形式被配置为迁徙群体中的生活。这种转变，或称相变，是由人口密度的巨大波动驱动的。在种群密度较低的情况下，蝗虫发生在独居阶段，在这一阶段，它们的外表和行为都很隐晦，最重要的是，它们积极地避开其他蝗虫。当蝗虫被迫聚集在一起时，它们就会转变为群居阶段。群居的蝗虫看起来非常不同，而且非常活跃，但至关重要的是，它们会被其他蝗虫吸引，这样它们最终就可以聚集成群。从独处行为转变为合群行为只需要几个小时，而身体上的变化需要几代人的时间。我们之前已经证明，在拥挤的早期阶段，大脑化学物质5-羟色胺的激增会触发这种行为的快速变化，尽管它是如何做到的还不清楚。5-羟色胺在包括人类在内的许多其他动物中也扮演着类似的重要角色，它参与了情绪和攻击性的调节。我们现在试图了解5-羟色胺是如何设定相变的，以及相变是否源于行为特征，如大胆/害羞或活动/安静，这些特征定义了其他动物的“个性”差异。我们希望确定这些基本特征在进化过程中是否被加入到相变过程中，从而解释它们通过5-羟色胺的共同调节。我们将通过对比表现出不同转变阶段倾向的蝗虫品系，以及对比根本不成群的密切相关物种来检验这一点。我们的研究利用复杂的自动运动跟踪系统来测试蝗虫面临不同问题的行为，例如在开阔的空间移动到食物或对一群其他蝗虫做出反应。我们将这些分析与生化技术结合起来，在相同的动物中测量5-羟色胺和其他神经化学物质，这样我们就可以开始确定是什么控制了不同和不断变化的行为表达。我们将使用药物(包括一些用于人类的药物)来操纵5-羟色胺途径，并使用电生理学方法从特定的含有5-羟色胺的神经细胞中记录我们怀疑对相变至关重要的信息。我们的研究将使用一种名为快速扫描循环伏安法的技术来测量5-羟色胺的释放，这种方法以前在昆虫中是不可能的，我们将与一家新的统计软件公司合作，开发和使用对行为的创新分析。我们工作的一个核心部分是在一些国际合作的基础上再接再厉，包括最近与毛里塔尼亚蝗虫控制中心达成的一项合作。通过这些伙伴关系，我们将获得野生蝗虫，这与我们已经拥有的实验室菌株形成了重要的对比。实验室和现场站之间的研究访问将为两个工作团队提供新的见解。莱斯特大学最近在世界领先的蝗虫研究设施上投资了超过100k GB来支持我们的工作。我们的工作的主要成果将是：(1)增加对导致蝗群形成和消散的过程的理解，并潜在地应用于蝗群控制；(2)对相变的演变及其与基本行为特征的关系的新见解；(3)增加对5-羟色胺起作用的生化途径的理解，以及这些途径如何被吸收到新的行为中；以及(4)新的国际和商业合作。

Desert locusts are notorious insect pests that periodically devastate crops and pastures at considerable human and economic cost. Unlike other grasshoppers, locusts can reversibly change between two dramatically different forms, one of which is configured for a life in migratory swarms. This transformation, or Phase Change, is driven by large fluctuations in population density. At low population densities locusts occur in the Solitarious Phase, where they are cryptic in appearance and behaviour, and most importantly, actively avoid other locusts. When locusts are forced together, they transform into the Gregarious Phase. Gregarious locusts look very different and are highly active, but crucially are attracted towards other locusts so that they can eventually aggregate into swarms. The change from solitarious to gregarious behaviour takes just a few hours whereas physical changes take several generations. We have previously demonstrated that a surge in the brain chemical serotonin during the early stages of crowding triggers this rapid change in behaviour, although how it does so is unknown. Serotonin has similarly important roles in many other animals, including humans, where it is involved in the regulation of mood and aggression. We now seek to understand how serotonin sets phase change in train, and whether phase change has arisen from behavioural traits such boldness/shyness or activity/quiescence that define 'personality' differences in other animals. We wish to determine whether such basic traits have been co-opted during evolution into the process of phase change, thus explaining their common regulation through serotonin. We will examine this by contrasting locust strains that show differing propensity to change phase, and by contrasting closely related species that do not swarm at all.Our research makes use of sophisticated automatic movement tracking systems to test the behaviours of locusts faced with different 'problems' such as moving to food across an open space or responding to a crowd of other locusts. We couple these analyses with biochemical techniques for measuring serotonin and other neurochemicals in the same animals, so we can begin to determine what governs the different and changing expressions of behaviour. We will use drugs (including some that are used in humans) to manipulate the serotonin pathway, and electrophysiological methods to record from particular serotonin-containing nerve cells that we suspect are critical to phase change. Our research will use a technique called fast scan cyclic voltammetry to measure the release of serotonin in ways that have not previously been possible in insects, and we will work with a new statistical software company to develop and use innovative analyses of behaviour. A core part of our work is to build on a number of international collaborations including one recently agreed with the Centre for Locust Control in Mauritania. Through these partnership we will gain access to wild locusts that provide an important contrast to the lab strains we already have. Research visits between the labs and field station will permit new insights for both teams of workers. The University of Leicester has recently invested more than £100k in a world-leading locust research facility to support our work.The key outcomes of our work will be: (1) an increased understanding of the processes leading to the formation and dissipation of locust swarms, with potential applications to swarm control; (2) new insights into the evolution of phase change and its relationship to fundamental behavioural characteristics; (3) increased understanding of the biochemical pathways through which serotonin works, and of how these pathways can be co-opted into new behaviours; and (4) new international and commercial collaborations.