| The network of interconnected neurons, the nervous system, is observed in bilaterians, cnidarians and ctenophores in Metazoa. Studies of development revealed a high degree of similarity in developmental genetics of nervous systems in Bilateria, suggesting common ancestry to bilaterian nervous system development. Phylogenetically, cnidarians are the most likely sister group to bilaterians, and cnidarian genomes contain gene sequences closely related to key regulatory genes involved in bilaterian neuronal development. However, functions of these cnidarian genes are poorly known, and thus the evolutionary relationship between the nervous systems of Cnidaria and Bilateria is unclear. My dissertation examines the development of the cnidarian nervous system using Aurelia (Cnidaria, Scyphozoa) as a model, and it consists of three chapters. Chapter one, "Early development, pattern and reorganization of the planula nervous system in Aurelia (Cnidaria, Scyphozoa)," examined nervous system development during embryogenesis and metamorphosis in Aurelia by using immunohistochemistry, confocal and transmission electron microscopy. Chapter two, "Development of the nervous system in medusa sensory structures rhopalia in Aurelia sp.1 (Cnidaria, Scyphozoa)," described spatial and temporal patterns of neuronal differentiation in the developing sensory structures, rhopalia, during medusa formation in Aurelia sp.1. Chapter three, "Distinct expression patterns of POUI/pit1, POUIV/brain3 and Otx in the developing medusa nervous system in Aurelia sp.1 (Cnidaria, Scyphozoa)," examined mRNA expression patterns of Aurelia sp.1 genes closely related to bilaterian neuronal developmental genes, namely, Otx, POUIV/Brain-3, and POUI/Pit-1, during medusa development in Aurelia sp.1 by fluorescent in situ hybridization, immunohistochemistry and confocal microscopy. The results suggest similarity in genetics of nervous system development in a cnidarian and Bilateria, and provide anatomical framework for gene expression and functional studies to deduce genetics of nervous system development in Aurelia sp.1. |
