title: Gas exchange and heart rate in the harbour porpoise, Phocoena phocoena.
abstract: The respiratory physiology, heart rates and metabolic rates of two captive juvenile male harbour porpoises (both 28 kg) were measured using a rapid-response respiratory gas analysis system in the laboratory. Breath-hold durations in the laboratory (12 +/- 0.3 s, mean +/- SEM) were shorter than field observations, although a few breath-holds of over 40 s were recorded. The mean percentage time spent submerged was 89 +/- 0.4%. Relative to similarly-sized terrestrial mammals, the respiratory frequency was low (4.9 +/- 0.19 breaths.min-1) but with high tidal volumes (1.1 +/- 0.011), enabling a comparatively high minute rate of gas exchange. Oxygen consumption under these experimental conditions (247 +/- 13.8 ml O2.min-1) was 1.9-fold higher than predicted by standard scaling relations. These data together with an estimate of the total oxygen stores predicted an aerobic dive limit of 5.4 min. The peak end-tidal O2 values were related to the length of the previous breath-hold, demonstrating the increased oxygen uptake from the lung for the longer dives. Blood oxygen capacity was 23.5 +/- 1.0 ml.100 ml-1, and the oxygen affinity was high, enabling rapid oxygen loading during ventilation.
authors.affiliation: Department of Zoology, University of Cambridge, UK. jane.reed@incyte.com
authors.forename: J Z
authors.initials: JZ
authors.lastname: Reed
authors.forename: C
authors.initials: C
authors.lastname: Chambers
authors.forename: C J
authors.initials: CJ
authors.lastname: Hunter
authors.forename: C
authors.initials: C
authors.lastname: Lockyer
authors.forename: R
authors.initials: R
authors.lastname: Kastelein
authors.forename: M A
authors.initials: MA
authors.lastname: Fedak
authors.forename: R G
authors.initials: RG
authors.lastname: Boutilier
mesh_terms: D000818:Animals; D004242:Diving; D006339:Heart Rate / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology; D019576:Porpoises / Q000097:blood / Q000502:physiology*; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012129:Respiratory Function Tests
chemical_list: D010100:Oxygen