Dissertation Research: Evolution and Development of Left-Right Asymmetry in Echinoderms

论文研究：棘皮动物左右不对称性的进化与发展进化生物学中最活跃的研究领域之一涉及不同动物门中独特形态特征的起源。棘皮动物门的成员（海胆、海星、海参和它们的亲戚）表现出许多特征，其进化起源在世纪以来一直是生物学家广泛猜测的话题。也许这些特征中最引人注目的是棘皮动物身体的对称性。棘皮动物的幼虫是两侧对称的，而成年人显示五倍径向对称。当成虫结构在幼虫的左侧发育时，这些非常不同的身体对称性之间发生了过渡，产生了左右不对称的中间阶段。已经提出了几种方案来解释棘皮动物生命周期中发生的从双侧对称到左右不对称再到五向对称的发育转变，但很少使用发育数据来测试这些理论的预测。本计画系系统研究棘皮动物成体结构之发育。本研究的目的是探讨1）棘皮动物左右不对称的进化; 2）棘皮动物左右不对称的发育机制及其进化起源。为了实现这些目标，将使用各种胚胎学技术，并将结果在不同的棘皮动物群体之间以及棘皮动物与其亲属之间进行比较。详细研究左右不对称的演化和发展，将有助于更好地理解棘皮动物形态的起源和演化。此外，这项研究将提供见解的进化和发展的左右不对称性在其他门的动物和变态的进化在其他海洋无脊椎动物。

Dissertation Research: Evolution and Development of Left-Right Asymmetry in EchinodermsGregory Wray and Margaret PizerOne of the most active areas of research in evolutionary biology today concerns the origin of the unique morphological features seen in the different animal phyla. The members of the phylum Echinodermata (sea urchins, sea stars, sea cucumbers and their relatives) exhibit a number of features whose evolutionary origin has been the topic of extensive speculation among biologists for over a century. Perhaps the most striking of these characteristics involve echinoderm body symmetry. Echinoderm larvae are bilaterally symmetrical, while the adults show five-fold radial symmetry. The transition between these very different body symmetries occurs when adult structures develop on the left side of the larva, producing a left-right asymmetrical intermediate stage. Several scenarios have been proposed to explain the developmental transitions from bilateral symmetry to left-right asymmetry to pentaradial symmetry that occur during the echinoderm life cycle, but little testing of the predictions of these theories has been done using developmental data. This project involves a systematic study of the development of adult structures in echinoderms. The goals of this study are to investigate 1) the evolution of left-right asymmetry within echinoderms and 2) the developmental mechanism of left-right asymmetry in echinoderms and the evolutionary origin of this mechanism. To achieve these goals a variety of embryological techniques will be used, and results will be compared between different groups of echinoderms and between echinoderms and their relatives. A detailed study of the evolution and development of left-right asymmetry will result in a better understanding of the origin and evolution of echinoderm morphology. In addition, this study will provide insights into the evolution and development of left-right asymmetry in other phyla of animals and the evolution of metamorphosis in other marine invertebrates.