论文标题：Collective behaviour in 480-million-year-old trilobite arthropods from Morocco

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作者：Jean Vannier, Muriel Vidal et.al

发表时间：2019/10/17

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古节肢动物化石被发现呈线状队列形态，这或许标志着一种响应环境的集体行为或季节性生殖迁徙。这一发现意味着堪比现代动物的集体行为可能早在4.8亿年前就已存在。相关研究成果Collective behaviour in 480-millionyear-old trilobite arthropods from Morocco 发表在本周的上。

图1：Ampyx priscus线形群 Thoral, 1935, 摩洛哥早奥陶世(Zagora 区域). 图源：Vannier等

已知集体社会行为通过自然选择演化了数百万年，从现代节肢动物中可以看到无数的例子，比如毛毛虫、蚂蚁或大龙虾的迁徙链。但是，集体行为的起源和早期历史一直不甚明了。

法国里昂大学的Jean Vannier及同事描述了来自摩洛哥早奥陶世（大约4.8亿年前）的若干Ampyx priscus的线型群，这些三叶虫长约16-22毫米，身体前部有一根结实的刺，而背部有一对非常长的刺。

在作者所检查的每一个三叶虫化石群中，各三叶虫均排列成线状，身体前部均朝向同一个方向，这些刺相互连在一起。作者认为考虑到所见排列模式的规模，这种协调一致的线性和方向性不太可能是被动输运或水流积聚的结果，而更可能是因为它们在行动的过程中突然死亡，比如在风暴中被水底沉积物迅速掩埋。

作者认为这些三叶虫可能在集体迁徙，它们沿着海底移动的时候，利用突出的长刺相互接触，保持一种单排队列。这可能是对风暴造成的环境扰动（通过运动和触觉感测器检测）的一种应激反应，三叶虫受激而向更加安静、更深的水域迁移。在现代的大龙虾中可以看到类似的行为。或者，这种运动模式可能是季节性生殖行为引起的，即性成熟个体向产卵地迁徙。

已知这些三叶虫是无视觉的，作者假定它们可能通过刺和明升手机物质产生感觉刺激，从而协调各自的运动。

以上发现表明4.8亿年前的一种节肢动物可能已经能利用自身的神经复杂性，形成临时性的集体行为。

摘要：Interactions and coordination between conspecific individuals have produced a remarkable variety of collective behaviours. This co-operation occurs in vertebrate and invertebrate animals and is well expressed in the group flight of birds, fish shoals and highly organized activities of social insects. How individuals interact and why they co-operate to constitute group-level patterns has been extensively studied in extant animals through a variety mechanistic, functional and theoretical approaches. Although collective and social behaviour evolved through natural selection over millions of years, its origin and early history has remained largely unknown. In-situ monospecific linear clusters of trilobite arthropods from the lower Ordovician (ca 480 Ma) of Morocco are interpreted here as resulting either from a collective behaviour triggered by hydrodynamic cues in which mechanical stimulation detected by motion and touch sensors may have played a major role, or from a possible seasonal reproduction behaviour leading to the migration of sexually mature conspecifics to spawning grounds, possibly driven by chemical attraction (e.g. pheromones). This study confirms that collective behaviour has a very ancient origin and probably developed throughout the Cambrian-Ordovician interval, at the same time as the first animal radiation events.

（来源：明升手机版(明升中国)）