Investigating the Assembly of an Animal Body Plan: The Early Evolution of Echinoderms

动物的起源是生命进化史上最重要的事件之一，但发生这种情况的机制尚不清楚。争论的焦点是，这一事件是大量小的进化变化的结果，还是相对较少的大规模变化的结果。从理论上讲，我们可以研究动物的化石遗骸来区分这些可能性，但不幸的是，大多数物种的早期化石记录显然相当不完整。棘皮动物(海胆、海星等)是一个例外，因为它们拥有坚硬的矿化骨架，因此，即使是它们最早的代表也被保存为化石。然而，要准确解读这一丰富的记录，我们还需要了解活着的动物的解剖、发育和遗传学。拟议研究的主要目的是重建棘皮动物的起源和早期进化；这将为更广泛地了解动物的出现提供重要的见解。我将通过：(1)重建棘皮动物的早期进化和(2)测试现有的主要理论在棘皮动物中的同源性(具有共同祖先的结构)来实现这一目标。这项研究将涉及古生物学、发育和分子技术的综合，这是破译动物进化的最有效手段。选定的棘皮动物化石将利用高分辨率的微型CT扫描和计算机软件进行研究，以生成3-D“虚拟化石”。结合扫描电子显微镜获得的图像，这种方法将使以前隐藏的化石细节得以研究和说明，为这些灭绝动物的关系和生活方式提供新的数据。将使用高倍显微镜和分析基因表达模式的分子技术来研究活的棘皮动物从胚胎到成年的发育。通过这种方式，将确定棘皮动物基本同源性的模型是否准确。这个项目很重要，因为它将帮助我们揭示灭绝的祖先动物的形态和关系，以及在它们进化为现代形式过程中出现的新奇事物。它还可能有助于推断动物进化史上深刻的、基本的事件的模式和过程。最终，这项研究的目的是证明，只有通过整合所有相关的调查途径和证据线，我们才能实现对生物进化的最佳理解。

The origin of animals was one of the most significant events in the evolutionary history of life, but the mechanism by which this occurred is unclear. Debate centres on whether this event was the result of numerous small evolutionary changes or relatively few large-scale ones. In theory we can study the fossilized remains of animals to discriminate between these possibilities, but unfortunately the early fossil records of most groups are apparently quite incomplete. The echinoderms (sea urchins, starfish and the like) are an exception to this because they possess a hard, mineralized skeleton and, hence, even their earliest representatives are preserved as fossils. However, to accurately interpret this rich record we also need to understand the anatomy, development and genetics of living animals. The principal aim of the proposed research is to reconstruct the origin and early evolution of echinoderms; this will provide important insights into the emergence of animals more generally. I will achieve this goal by: (1) reconstructing the early evolution of echinoderms and (2) testing the major existing theory for homologies (structures with a shared ancestry) in echinoderms. This research will involve a synthesis of palaeontological, developmental and molecular techniques, which is the most effective means of deciphering animal evolution. Selected fossil echinoderms will be studied using high-resolution micro-CT scanning and computer software to generate 3-D 'virtual fossils'. In combination with images obtained from scanning electron microscopy, this approach will allow previously hidden details of fossils to be studied and illustrated, providing new data on the relationships and mode of life of these extinct animals. The development of living echinoderms from embryo to adult will be studied using high-powered microscopes and a molecular technique for analyzing the expression patterns of genes. In this manner it will be established if the model for determining fundamental homologies in echinoderms is accurate. This project is important as it will help us uncover the morphology and relationships of extinct ancestral animals, and the novelties that arose during their evolution into modern forms. It may also help to infer the pattern and process of deep, fundamental events in animal evolutionary history. Ultimately, this research aims to demonstrate that only by integrating all relevant avenues of enquiry and lines of evidence can we achieve an optimal understanding of organismal evolution.