Evolution of a Novel Larval Body Plan - the Nemertean Pilidium Larva (Phylum Nemertea)

纤毛是一种迷人的浮游幼虫，在一组海洋线虫中发现。在这群蠕虫中，发展是最大程度上间接的。这意味着浮游幼虫和底栖成虫这两个生命史阶段的构造和功能完全不同。幼虫在纤毛幼虫体内形成数周，然后在灾难性的变态过程中从幼虫中爆发出来，并迅速吞噬幼虫的身体。许多海洋无脊椎动物也有类似的间接发展。在许多情况下，这种发育被缩短或简化，导致直接发育，其中幼虫阶段，如果存在，类似于成虫阶段。然而，在nemerteans中，很明显，间接发展模式是从祖先的直接发展演变而来的。本项目旨在研究纤毛幼虫在发育过程中的变化对其进化的影响。一般的方法是比较同源胚胎细胞的命运和发育调控基因的表达，在有和没有毛的纳默特种。这一结果将阐明幼虫体和成虫纤毛内部不同部位的进化起源，并揭示在直接和间接发育的情况下，虫体平面的前后轴线是如何建立的。该项目有望对进化发育生物学的核心问题做出重大贡献，例如新的动物身体计划的起源。该项目为不同的本科生和研究生提供培训和研究机会，包括社区大学生，其中许多人来自代表性不足的群体。最后，该项目通过在海洋生物野外站维持分子实验室和先进的显微镜设备，扩大其研究和教学能力，并为其他机构的访问科学家提供服务。

The pilidium is a fascinating planktonic larva found in one group of marine nemertean worms. In this group of worms the development is maximally-indirect. This means that the two life history stages, the planktonic larva and the benthic adult worm, are built and function entirely differently. The young worm forms inside the pilidium larva over the course of many weeks, then erupts from the larva during catastrophic metamorphosis, and promptly devours the larval body. Many marine invertebrate animals have similarly indirect development. In many of those the development has been abbreviated or simplified, giving rise to direct development, in which the larval stage, if present, resembles the adult. In nemerteans, however, it is clear, that indirect developmental mode evolved from ancestral direct development. This project aims to investigate what changes in development contributed to the evolution of the pilidium larva. The general approach is to compare fates of homologous embryonic cells and expression of developmental regulatory genes in nemertean species with and without the pilidium. The results will clarify the evolutionary origin of the different domains of the larval body and the adult rudiments inside the pilidium, and shed light on how the antero-posterior axes of the body plan is established in nemerteans with direct and indirect development. This project is expected to contribute significantly to central issues in evolutionary developmental biology, such as the origin of novel animal body plans. This project provides training and research opportunities for diverse undergraduate and graduate students, including community college students, many of which are from underrepresented groups. Finally, this project, by maintaining a molecular lab and advanced microscopy facility at a marine biological field station, expands its research and teaching capacity and serves visiting scientists from other institutions.