Research Objectives:
Nototheniid fishes inhabiting the near-freezing (–2ºC) waters of McMurdo Sound have some of the highest serum and cellular sodium concentrations and the lowest gill sodium/potassium-ATPase (Na/K-ATPase, the sodium/potassium pump) activities of any marine teleost. The enzyme Na/K-ATPase regulates the sodium concentration in the cells of many organisms. Maintaining a high salt content in the cells of these fish lowers the freezing point to allow them to inhabit cold antarctic waters and reduces the salt gradient between them and the sea water.
On the basis of previous studies of temperature effects, we hypothesize that compared with New Zealand nototheniids that inhabit warmer waters, antarctic nototheniids have lower drinking rates, lower salt excretion rates, and a higher proportion of the low intracellular sodium affinity for a specific subunit of the Na/K-ATPase (a3-isoform). These unique osmoregulatory properties explain the high serum and cellular sodium concentrations found in nototheniids south of the antarctic Polar Front. We will compare and contrast the unique osmoregulatory mechanisms of antarctic and New Zealand nototheniids with respect to
+ Sea water drinking rates and the serum and cellular chemical composition of the fish,
+ Enzymatic properties and the expression pattern of mRNA and protein, and
+ Temporal and spatial localization of the Na/K-ATPase a3-isoform subunit in the gills.
To accomplish these objectives, we will study four species of nototheniids, representing ecologically diverse habits above and below the Polar Front.
The information we gain will increase our knowledge about the role of Na/K-ATPase in the cellular function in many organisms, strengthen our understanding of the biochemical and physiological adaptations that allow antarctic nototheniids to survive and thrive in the ice-laden waters south of the antarctic Polar Front, provide field and laboratory research experience for graduate and undergraduate students, and contribute to significant outreach activities in science education for elementary and high school students and teachers.
