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

University Of California-Riverside, Riverside CA

Investigators

Abstract

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.