Master of Science (MSc)
Faculty of Science
Michael P. Wilkie
Jonathan M. Wilson
Ionoregulation and nitrogenous waste (N-waste) metabolism in fishes has been extensively documented in teleosts and elasmobranchs, but less so in lampreys (Petromizontiformes). All lamprey species undergo metamorphosis which drastically changes their physiology and modes of feeding. However, differences in ionoregulatory mechanisms due to anadromous versus non anadromous life history strategies emerge following metamorphosis in different lamprey species. Furthermore, some species, such as anadromous juvenile sea lamprey (Petromyzon marinus), are parasitic and migrate to seawater (SW) to ingest blood protein from host fishes, while juveniles of freshwater (FW), non-parasitic species, such as the American brook lamprey (Lethenteron appendix), cease feeding following metamorphosis. Hence, differences in anadromy and protein consumption between different lamprey species may require different mechanisms for ion, ammonia, and urea excretion. The objective of this thesis was to determine how variation in anadromy and dietary protein consumption between parasitic and non-parasitic lamprey species affects expression of ion, ammonia, and urea transporters in various excretory tissues. The distribution and abundance of key transport proteins such as Na+/K+-ATPase (NKA), ammonia transporting Rhesus glycoprotein, and urea transport protein were investigated using immunohistochemical staining, Western Blot analysis, and enzyme activity assays. The present study demonstrated that SW ionoregulatory machinery was retained in landlocked sea lamprey and FW resident American brook lamprey. Furthermore, ammonia transporting Rhcg-like protein was expressed differently in sea lamprey and American brook lamprey following metamorphosis. Finally, ion, ammonia, and urea transport mechanisms were documented in the kidney of both lamprey species with little differences in localization of each protein observed in sea lamprey versus American brook lamprey. Thus, the present study has helped to shed light on current mechanisms of ionoregulation and N-waste excretion in lampreys with markedly different life history strategies.
Davidson, Shannon, "Comparing Ionoregulation and Modes of Nitrogen Excretion Across the Life Cycle of Parasitic and Non-parasitic Lamprey Species" (2024). Theses and Dissertations (Comprehensive). 2637.