title: The effect of sustained hypoxia on the cardio-respiratory response of bowfin Amia calva: implications for changes in the oxygen transport system.
abstract: This study examined mechanisms underlying cardio-respiratory acclimation to moderate sustained hypoxia (6.0 kPa for 7 days at 22° C) in the bowfin Amia calva, a facultative air-breathing fish. This level of hypoxia is slightly below the critical oxygen tension (pcrit ) of A. calva denied access to air (mean ± s.e. = 9.3 ± 1.0 kPa). Before exposure to sustained hypoxia, A. calva with access to air increased air-breathing frequency on exposure to acute progressive hypoxia while A. calva without access to air increased gill-breathing frequency. Exposure to sustained hypoxia increased the gill ventilation response to acute progressive hypoxia in A. calva without access to air, regardless of whether they had access to air or not during the sustained hypoxia. Additionally, there was a decrease in Hb-O2 binding affinity in these fish. This suggests that, in A. calva, acclimation to hypoxia elicits changes that increase oxygen delivery to the gas exchange surface for oxygen uptake and reduce haemoglobin affinity to enhance oxygen delivery to the tissues.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: C S
authors.initials: CS
authors.lastname: Porteus
authors.forename: P A
authors.initials: PA
authors.lastname: Wright
authors.forename: W K
authors.initials: WK
authors.lastname: Milsom
mesh_terms: D000064:Acclimatization; D000388:Air; D000818:Animals; D005399:Fishes / Q000378:metabolism / Q000502:physiology*; D005880:Gills / Q000502:physiology; D006454:Hemoglobins / Q000378:metabolism; D000860:Hypoxia; D010100:Oxygen / Q000378:metabolism*; D012119:Respiration
chemical_list: D006454:Hemoglobins; D010100:Oxygen
keywords: Hb-O2 binding affinity; critical oxygen tension; facultative air breather; metabolic rate