Development and evolution of the nematode male tail fan will be studied. The long term objective is to reconstruct the evolutionary pathway that has historically been followed to lead to diverse nematode forms. The aim is to identify and describe in molecular terms the genetic events that underlie the evolution of developmental programs. Evolution of the tail fan developmental program will be studied by comparing the cellular mechanisms of fan development in C. elegans with that in four other free living nematode species. The fan is chosen for these studies because its morphology varies widely among nematode species. Cells responsible for making the fan will be identified by cell ablation experiments in C. elegans. Development of the fan will be studied by tracing cell lineages, defining the positions of epidermal cells by indirect immunofluorescence staining with a monoclonal antibody to a cell junctional antigen, and by direct light microscopic observation. Points of evolutionary divergence will be identified in the various stages of fan differentiation. A phylogenetic tree indicating the evolutionary relationships of the nematode species studies will be constructed from sequences of the small ribosomal subunit genes. In order to identify genes that may have played a role in evolution of the fan, mutants of C. elegans with abnormal fans will be analyzed. Existing mutations will be genetically mapped to place them into genes. Phenotypes of the mutations will be described following the same criteria used to compare the different species. In this way, it is hoped to identify genes acting at the same developmental stages where evolutionary divergence has occurred.
