Dissertation Research: Comparative Anatomy and Morphogenesis in the Cephalobinae (Nematoda:Rhabditida)

加州大学河滨分校的James Baldwin博士和Daniel Bumbarger先生获得了一项拨款，用于研究头叶线虫(Cephalobinae)细胞外摄食附属物的结构和进化。该项目将描述这些结构的超微结构解剖，对负责它们组装的过程进行分类，并探索与理解异时性和新颖性进化相关的发育特征进化模式。由于这些结构在亚微米空间尺度上极其复杂，将利用电子断层扫描这一独特的三维电子显微镜方法来描述解剖结构。这些结构的形态发生将用更传统的光学显微镜来研究。比较工作主要基于成虫和幼虫形态的扫描电子显微镜，将与分子系统发生实验室合作进行。预计该项目将提供一个基础，在此基础上提出广泛感兴趣的分类学、发育和进化问题。该项目将通过提供强有力的特征同源性假设，以反映系统发育关系的方式重新定义分类分组，从而为已经在进行的专题工作做出贡献。这项拟议的研究代表了电子断层扫描的新应用，可能会被证明对评估其他小型无脊椎动物群体的同源性很有用。线虫是理解发育进化的很好的模型，特别是在必须理解基因和表型变化之间的联系的情况下。前部形态的复杂性和多样性的模式表明，发育模块的存在可以相对独立地进化。这些摄食附件中的许多突变可能是可行的，这将有助于识别负责进化变化的发育调控基因。

A grant has been awarded to Dr. James Baldwin and Mr. Daniel Bumbarger at University of California, Riverside to study the structure and evolution of extracellular feeding appendages in the Cephalobinae, a group of microbial feeding nematodes. The project will describe the ultrastructural anatomy of these structures, classify processes responsible for their assembly and explore patterns in developmental character evolution that are relevant to understanding heterochrony and the evolution of novelty. As these structures are extremely complex on a sub-micrometer spatial scale, a unique application of electron tomography, a three dimensional electron microscopy method, will be utilized to describe the anatomy. Morphogenesis of these structures will be studied with more traditional light microscopy. Comparative work, based primarily on scanning electron micrographs of adult and juvenile morphologies, will be done in collaboration with a molecular phylogenetic lab.It is expected that this project will provide a foundation upon which to ask taxonomic, developmental and evolutionary questions of broad interest. This project will contribute to monographic work already in progress by providing strong hypotheses of character homology with which to re-define taxonomic groupings in a manner that reflects phylogenetic relationships. The proposed research represents novel application of electron tomography that may prove useful for assessing homology in other groups of small invertebrates. Nematodes make excellent models for understanding the evolution of development, particularly where a link between genotypic and phenotypic changes must be understood. Patterns in the complexity and diversity of anterior morphology suggest the presence of developmental modules that could evolve relatively independently from one another. Many mutations in these feeding appendages will likely be viable, which will facilitate identification of developmental regulatory genes responsible for evolutionary changes.