NRES Departmental Seminar by Dr. Jason Bystriansky, DePaul University.

Title: Salinity Acclimation in Salmonid Fishes

I am an environmental physiologist who takes a comparative approach to understanding how animals are adapted to survive in harsh environments. My research program is mainly focused on what limits most fish species to live in either fresh or salt water, while others can tolerate a wide range of environmental salinities. To do so, I study the role and regulation of Na+,K+-ATPase (the sodium pump) in osmoregulation and how the expression of different isoforms of this protein may limit the salinity tolerance of fish. The sodium pump is found in the plasma membrane of virtually all animal cells and is largely responsible for maintaining low intracellular sodium concentrations. Despite decades of intensive research, the regulation of this vital protein is still poorly understood. The euryhaline fish gill is an excellent model system to examine sodium pump regulation as it plays a central role in both the active ion uptake model of freshwater fishes, and the active ion secretion model of marine fishes. During the transition from freshwater to seawater (and vice versa), the fish gill changes from a salt absorbing tissue to one that actively secretes sodium and chloride, with the sodium pump playing a central role in regulating ion flux, and therefore whole body osmoregulation. By changing the salinity that euryhaline fish are exposed to we can manipulate gill sodium pump expression and activity, thereby giving us a powerful tool and model to examine sodium pump regulation. My research focuses mainly on the salinity tolerance of Salmonid fishes, but also on several other euryhaline fish groups including, eels, stickleback, sturgeon and killifish.