Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Environmental Toxicology


Rice, Charles D


Little is known about the development of the immune system in estuarine teleosts. The aim of this study was to describe the disappearance of maternally-derived immune components of immunity and the development of the immune system in the estuarine killifish, Fundulus heteroclitus, also known as the mummichog. Maternal-derived IgM was measured by ELISA and whole body lysozyme levels were determined by both enzymatic and immunological methods. Recombination activation gene-1 (Rag-1) expression was quantified using real time quantitative PCR and organ development was monitored using histological techniques. Rag-1 was cloned from F.heteroclitus and a recombinant Rag-1 protein was expressed for the production of Rag-1 antibodies. Rag-1 was expressed most in the head kidney, followed by the heart and brain. Using a capture ELISA, IgM was first detected at 1 day post-fertilization (dpf), but decreased shortly after hatching and did not increase for the remainder of the study period. Lysozyme protein was first detected at 7 dpf by immunoblot and IHC using a monoclonal antibody (mAb M24-2) specific to mummichog lysozyme. Expression levels of Rag-1 increased rapidly at 2-wph reaching a peak at 3-wph. The head kidney was the first to appear at 7-dpf, followed by the spleen at 1-wph, and the thymus at 3-wph. These findings indicate that the mummichog has all lymphoid organs by 5-wph. However, they do not have aspects of humoral immunity until sometime after 5-wph, and thus probably rely on innate and passive immunity for at least 5-wph. To the author's knowledge, this study is the first to describe the ontogeny of the immune system in an estuarine teleost fish. This study will add to the growing body of information on the immuobiology of fishes. Morevover, this research provides baseline data for future studies on impacts of environmental stressors on developing fish immune systems.