title: The effects of strain and ploidy on the physiological responses of rainbow trout (Oncorhynchus mykiss) to pH 9.5 exposure.
abstract: We characterized the physiological effects of exposure to pH9.5 on one domesticated and four wild strains of diploid and triploid juvenile rainbow trout (Oncorhynchus mykiss) over two consecutive years. In the first year, 35-70% of the individuals from the wild strains showed a loss of equilibrium (LOE) at 12 h exposure to pH9.5, with all fish from wild strains experiencing a LOE by 48 h. In contrast, <20% of the domesticated strain showed LOE over the 48 h exposure to pH9.5. In our second experiment, similar strain effects were observed, but far fewer fish showed LOE (≤50% in all strains) over 72 h at pH9.5. In both experiments, there was no effect of ploidy on time to LOE. In the fish that did not show LOE, high pH exposure resulted in significant increases in plasma, brain and muscle ammonia, with no effect of strain or ploidy on the extent of ammonia accumulation. Glutamine accumulated in the brain during high pH exposure, with a stoichiometric decrease in glutamate, but no differences were noted among strains or ploidies. Lactate also accumulated in the plasma to a similar extent in all trout strains and ploidies. Plasma chloride decreased at 24h exposure in all trout strains and ploidies, but recovered by 72 h. No change was observed in plasma sodium. Overall, our data suggest that the domesticated strain of trout is more tolerant of pH9.5 than the wild strains, but these differences in tolerance cannot be explained by our sub-lethal assessment of ammonia balance or ion regulation.
authors.affiliation: Department of Zoology, The University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada. Electronic address: wathompson29@gmail.com.
authors.forename: William A
authors.initials: WA
authors.lastname: Thompson
authors.affiliation: Department of Zoology, The University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada.
authors.forename: Tamara M
authors.initials: TM
authors.lastname: Rodela
authors.affiliation: Department of Zoology, The University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada.
authors.forename: Jeffrey G
authors.initials: JG
authors.lastname: Richards
mesh_terms: D000641:Ammonia / Q000097:blood; D000818:Animals; D001835:Body Weight; D001921:Brain / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009132:Muscles / Q000737:chemistry; D017686:Oncorhynchus mykiss / Q000145:classification / Q000235:genetics / Q000502:physiology*; D011003:Ploidies; D014508:Urea / Q000097:blood
chemical_list: D000641:Ammonia; D014508:Urea
keywords: Ammonia; High pH; Ion regulation; Strain; Triploid