title: The effects of temperature on the physiological response to low oxygen in Atlantic sturgeon.
abstract: Atlantic sturgeon (Acipenser oxyrhynchus), which are bottom dwelling and migratory fish, experience environmental hypoxia in their natural environment. Atlantic sturgeon, acclimated to either 5 or 15°C, were subjected to a 1 h severe (<10 mm Hg) hypoxia challenge in order to document their physiological responses. We measured hematological parameters, including O(2) transport (hemoglobin, hematocrit), ionic (chloride, osmolality), and metabolic (glucose, lactate) variables under normoxic conditions (~160 mm Hg), immediately following a 1 h exposure to hypoxic water, and following a further 2 h of recovery from this challenge in normoxic water. In a second experiment, we assessed the opercular beat frequency before, during, and after hypoxic exposure. Hemoglobin concentrations and hematocrit were significantly different between fish held at 5°C vs. 15°C and also significantly different between normoxia prior to hypoxia and following recovery. Plasma lactate concentrations increased following hypoxia at both temperatures, indicative of an increase in anaerobic metabolism. In contrast, a significant increase in plasma glucose concentrations in response to hypoxia only occurred at 5°C, suggesting different fuel demands under different temperatures. Changes in opercular beat frequency (OBF) were dependent on temperature. At 5°C, OBF increased upon exposure to hypoxia, but returned to pre-exposure levels within 35 min for the remainder of the experiment. During hypoxia at 15°C, OBF increased very briefly, but then rapidly (within 20 min) decreased to levels below control values. Following a return to normoxia, OBF quickly increased to control levels. Overall, these findings suggest that Atlantic sturgeons are relatively tolerant to short-term and severe hypoxic stress, and the strategies for hypoxia tolerance may be temperature dependent.
authors.affiliation: Department of Biology, University of New Brunswick, Saint John, NB, Canada. jkieffer@unb.ca
authors.forename: James D
authors.initials: JD
authors.lastname: Kieffer
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Baker
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Wood
authors.forename: Christos N
authors.initials: CN
authors.lastname: Papadopoulos
mesh_terms: D000064:Acclimatization; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D005399:Fishes / Q000502:physiology*; D000860:Hypoxia / Q000503:physiopathology*; D019344:Lactic Acid / Q000378:metabolism; D009994:Osmolar Concentration; D010100:Oxygen / Q000502:physiology*; D013696:Temperature
chemical_list: D001786:Blood Glucose; D002712:Chlorides; D019344:Lactic Acid; D010100:Oxygen