Dynamics and origins of socially induced plasticity of behaviour

沙漠蝗虫是一种臭名昭著的害虫，定期破坏庄稼和牧场，造成巨大的人力和经济损失。与其他蚱蜢不同，蝗虫可以在两种截然不同的形式之间可逆地变化，其中一种是为迁徙群体的生活而配置的。这种转变或相变是由人口密度的大幅波动驱动的。在低种群密度时，蝗虫发生在孤立期，在这个阶段，它们的外表和行为都是隐蔽的，最重要的是，它们会主动避开其他蝗虫。当蝗虫被迫聚集在一起时，它们会转变为群居阶段。群居的蝗虫看起来非常不同，而且非常活跃，但关键是它们会被其他蝗虫吸引，这样它们最终就能聚集成一群。从孤僻行为到群居行为的转变只需要几个小时，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，大脑化学物质血清素的激增引发了这种行为的快速变化，尽管它是如何发生的尚不清楚。血清素在包括人类在内的许多其他动物身上也有类似的重要作用，它参与调节情绪和攻击性。我们现在试图了解血清素是如何在训练中设定阶段变化的，以及阶段变化是否源于行为特征，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是否在进化过程中被增选为相变过程，从而解释它们通过血清素的共同调节。我们将通过对比表现出不同改变阶段倾向的蝗虫品系，以及对比根本不聚集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对不同“问题”的行为，例如在开放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，测量同一动物的血清素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的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）来操纵血清素通路，并使用电生理学方法来记录我们怀疑对相变至关重要的特定含血清素的神经细胞。我们的研究将使用一种称为快速扫描循环伏安法的技术来测量血清素的释放，这种方法以前在昆虫身上是不可能的，我们将与一家新的统计软件公司合作，开发和使用创新的行为分析。我们工作的一个核心部分是在若干国际合作的基础上开展工作，包括最近与毛里塔尼亚蝗虫防治中心商定的合作。通过这些伙伴关系，我们将获得与我们已有的实验室菌株形成重要对比的野生蝗虫。实验室和实地站之间的研究访问将为两组工作人员提供新的见解。莱斯特大学最近向世界领先的蝗虫研究机构投资了10多万英镑，以支持我们的工作。我们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，并具有蝗群控制的潜在应用；(2)对相变演化及其与基本行为特征关系的新认识；(3)提高了对血清素作用的生化途径的理解，以及这些途径如何被纳入新的行为；(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.