Cambrian Nervous Systems for Reconstructing the Arthropod Tree of Life

节肢动物是一种无脊椎动物，有外骨骼、分节的身体和关节的腿，如昆虫、螃蟹、蜘蛛和蜈蚣。节肢动物是迄今为止最大和最多样化的门，与两个较小的门，绒虫门和水熊门密切相关，共同构成了全节肢动物。它们首先出现在5.2亿年前的“寒武纪大爆发”中，以化石记录中大多数主要动物门的突然出现为标志。全节肢动物漫长的地质历史和独特的多样性使它们成为了解动物起源和早期进化的理想候选者，因此研究它们的寒武纪化石记录是至关重要的。全节肢动物外表上的巨大差异使人们很难理解它们之间的相互关系。相比之下，最近的研究表明，中枢神经系统（CNS）的进化非常保守，虽然物种之间的差异可以识别，但每个主要群体内的总体安排非常稳定。因此，中枢神经系统为理解主要全节肢动物类群之间的关系提供了一个主要的数据来源。不幸的是，现存的物种不能告诉我们最早的全节肢动物的大脑和神经系统，或者它们的早期进化史。只有记录节肢动物最早进化阶段的化石才能提供答案。动物的柔软部分往往在死后迅速腐烂，所以大多数节肢动物化石都是坚硬部分（如外骨骼）的遗骸，对它们的内部解剖结构知之甚少。然而，在特殊情况下，生物的未矿化软组织也可以保存得非常详细，例如在两个著名的寒武纪化石组合中：中国西南部的澄江生物群（约520亿年前）和加拿大的伯吉斯页岩（约505亿年前）。两者都有丰富的全节肢动物化石，保存完好的外部形态和内部解剖结构，提供了关于最早的全节肢动物的重要信息。与传统的神经组织不能经受石化的假设相反，应聘者和她的同事最近报道了成江节肢动物异常保存的大脑和神经系统，为了解节肢动物化石注入了新的数据，并建立了一个新的研究领域——“神经古生物学”。进一步的临时研究已经在更早的全节肢动物化石中发现了大脑和其他神经组织，为节肢动物大脑的起源提供了重要信息；以及新发现的保存异常完好的循环系统（以前在节肢动物化石记录中几乎一无所知）和寒武纪全节肢动物的感觉结构（例如眼睛和触角上的感觉器官）。连同它们的中枢神经系统，这些为早期全节肢动物的生态学和进化提供了独特的见解。本项目旨在准确记录成江页岩和伯吉斯页岩生物群中特别保存的寒武纪全节肢动物（如叶足类、异足类和节肢类）的中枢神经系统、感觉结构和其他内部器官系统，并将这些数据与现存类群进行比较，以增加我们对辐射和分化早期主要类群之间进化关系的认识。

Arthropods are invertebrate animals with an exoskeleton, a segmented body, and jointed legs, such as insects, crabs, spiders and centipedes. Arthropoda is by far the largest and most diverse phylum today and is closely related to two smaller phyla, Onychophora (velvet worms) and Tardigrada (water bears), together forming Panarthropoda. They first appear 520 million years ago (Mya) in the "Cambrian Explosion", marked by the sudden appearance of most major animal phyla in the fossil record. The long geological history and exceptional diversity of panarthropods make them ideal candidates for understanding the origin and early evolution of animals, and it is thus fundamental to investigate their Cambrian fossil record.The great diversity in the external appearance of panarthropods makes it difficult to understand their interrelationships. In contrast, recent studies show that the evolution of the central nervous system (CNS) has been remarkably conservative, and while variations between species can be recognised, the general arrangement within each major group has been very stable. Therefore, the CNS provides a primary source of data for understanding the relationships of major panarthropod groups. Unfortunately, extant species cannot inform us about the earliest panarthropod brains and nervous systems, or their early evolutionary history. Only fossils, which record the earliest stages in the evolution of arthropods, can provide the answers.Soft parts of animals tend to decay away quickly after death, so most arthropod fossils are the remains of hard parts (e.g. exoskeletons) and much less is known about their internal anatomy. However, under exceptional circumstances, the unmineralised soft tissue of organisms can also be preserved in exquisite detail, such as in two famous Cambrian fossil assemblages: the Chengjiang biota, southwest China (circa 520 Mya), and the Burgess Shale, Canada (circa 505 Mya). Both yield abundant panarthropod fossils with exceptionally preserved external morphology and internal anatomy, providing crucial information about the earliest panarthropods. Countering orthodox assumptions that neural tissue does not withstand fossilization, the applicant and her colleagues recently reported exceptionally preserved brains and nervous systems from Chengjiang arthropods, which added a fresh injection of data for understanding fossil arthropods and established a new research field, "neuropalaeontology". Further provisional studies have discovered the brain and other neural tissues in even earlier-derived fossil panarthropods, providing vital information regarding the origin of arthropod brains; as well as new discoveries of exceptionally preserved circulatory systems (previously all but unknown in the arthropod fossil record) and sensory structures (e.g. eyes and sense organs on the antennae) from Cambrian panarthropods. Together with their CNS, these provide unique insights into the ecology and evolution of early panarthropods.The aim of this project is to accurately document the CNS, sensory structures and other internal organ systems from exceptionally preserved Cambrian panarthropods (e.g. lobopodians, anomalocaridids and arthropods) of the Chengjiang and Burgess Shale biotas and compare the data with living groups, so as to increase our understanding of the evolutionary relationships between major groups during the early stages of radiation and divergence.