Branchial Ionoregulatory Mechanisms of Sodium Regulation in Freshwater Salmonids with Conservational Implications for Arctic Grayling (Thymallus arcticus)

• Author / Creator

  Blair, Salvatore D

• This thesis on fish osmoregulation focuses particularly on the mechanisms utilized by freshwater salmonids to absorb Na+ ions from dilute hypotonic environments and at the same time, their capacity to make necessary changes in order to tolerate higher saline environments. In this thesis, I present data that indicate rainbow trout embryos/larvae reared in low Na+ soft water maintain homeostasis by way of an EIPA-sensitive Na+ uptake pathway. In addition rainbow trout showed significantly increased nhe3b expression at the embryo/larvae and juvenile life stages and overall, these data support a primary role for nhe3b at these life stages. Three nhe isoforms: nhe2, nhe3a, and nhe3b were cloned, from trout gill (2 and 3b) and kidney (3a), into pDisplay expression vectors for transfection into the AP – 1 cell line in an attempt to further characterize the pharmacological properties of these transporters. However, at this time stable transfections have not resulted in successful Nhe protein expression. From a conservation physiology perspective I have shown that the Arctic grayling (a threatened native salmonid) demonstrates a reduced salinity tolerance and develops a novel associated interlamellar cell mass, in response to hypersaline waters, which has strong implications for hypersaline spills from hydraulic fracturing and other oil and gas operations. I presented data indicating this interlamellar cell mass and osmotic stress can be reversed if the salinity exposure lasts 48 hrs or less and recovery in freshwater is achievable. In iii addition to salinity tolerance data and in order to have a comprehensive management plan for Arctic grayling, thermal tolerance data were collected indicating CTmax of 26.9°C and 27.8°C when acclimated to 13°C and 17°C water temperatures (see Appendix A). This work provides evidence of three nhe isoform expression patterns during development in rainbow trout despite thermodynamic constraints, demonstrates reduced salinity tolerance of a threatened native salmonid in Alberta, provides the first reported instance of a salinity-induced ILCM in salmonids, and provides necessary physiological data for conservation management strategies for Arctic grayling.

• Subjects / Keywords

  • Ionoregulation
  • Gills
  • Sodium
  • Arctic grayling
  • Nhe

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3542JD7X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.