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

论文研究：棘皮中左右不对称的进化和发展格雷戈里·雷和玛格丽特·皮泽是当今进化生物学中最活跃的研究领域之一，涉及不同动物门独特形态特征的起源。棘皮动物门的成员(海胆、海星、海参及其近亲)表现出许多特征，其进化起源一个多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的身体对称性。棘皮动物幼虫两侧对称，成虫呈五重径向对称。当幼虫左侧的成体结构发育时，这些非常不同的身体对称性之间的转变发生，产生一个左右不对称的中间期。已经提出了几种情景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叉对称的发育转变，但几乎没有使用发育数据来检验这些理论的预测。这个项目涉及对棘皮动物成体结构发育的系统研究。本研究的目的是：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，并将在不同类别的棘皮动物之间以及棘皮动物与其近亲之间的结果进行比较。对左右不对称的演化和发展进行详细的研究将有助于更好地理解棘皮动物形态的起源和进化。此外，本研究还将为其他动物门的左右不对称的进化和发展以及其他海洋无脊椎动物的变态进化提供见解。

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.