Fahlman Andreas, Svärd Caroline, Rosen David A S, Jones David R, Trites Andrew W
Marine Mammal Research Unit, Fisheries Centre, Room 247, Aquatic Ecosystems Research Laboratory, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada.
J Exp Biol. 2008 Nov;211(Pt 22):3573-80. doi: 10.1242/jeb.023655.
The metabolic costs of foraging and the management of O2 and CO2 stores during breath-hold diving was investigated in three female Steller sea lions (Eumetopias jubatus) trained to dive between 10 and 50 m (N=1142 dives). Each trial consisted of two to eight dives separated by surface intervals that were determined by the sea lion (spontaneous trials) or by the researcher (conditioned trials). During conditioned trials, surface intervals were long enough for O2 to return to pre-dive levels between each dive. The metabolic cost of each dive event (dive+surface interval; DMR) was measured using flow-through respirometry. The respiratory exchange ratio (VO2/VCO2) was significantly lower during spontaneous trials compared with conditioned trials. DMR was significantly higher during spontaneous trials and decreased exponentially with dive duration. A similar decrease in DMR was not as evident during conditioned trials. DMR could not be accurately estimated from the surface interval (SI) following individual dives that had short SIs (<50 s), but could be estimated on a dive by dive basis for longer SIs (>50 s). DMR decreased by 15%, but did not differ significantly from surface metabolic rates (MRS) when dive duration increased from 1 to 7 min. Overall, these data suggest that DMR is almost the same as MRS, and that Steller sea lions incur an O2 debt during spontaneous diving that is not repaid until the end of the dive bout. This has important consequences in differentiating between the actual and 'apparent' metabolic rate during diving, and may explain some of the differences in metabolic rates reported in pinniped species.
研究了三只雌性北海狗（Eumetopias jubatus）在进行10至50米深度潜水时觅食的代谢成本以及屏气潜水期间氧气和二氧化碳储备的管理情况（共1142次潜水）。每次试验包括两到八次潜水，潜水之间的水面间隔由海狗自行决定（自发试验）或由研究人员决定（条件试验）。在条件试验中，水面间隔足够长，以便每次潜水之间氧气能恢复到潜水前的水平。使用流通式呼吸测定法测量每次潜水事件（潜水+水面间隔；DMR）的代谢成本。与条件试验相比，自发试验期间的呼吸交换率（VO2/VCO2）显著更低。自发试验期间DMR显著更高，并且随潜水持续时间呈指数下降。在条件试验期间，DMR的类似下降并不那么明显。对于水面间隔短（<50秒）的单次潜水，无法根据水面间隔（SI）准确估计DMR，但对于较长的水面间隔（>50秒），可以逐次潜水进行估计。当潜水持续时间从1分钟增加到7分钟时，DMR下降了15%，但与水面代谢率（MRS）没有显著差异。总体而言，这些数据表明DMR与MRS几乎相同，并且北海狗在自发潜水期间会产生氧气债，直到潜水回合结束才会偿还。这对于区分潜水期间的实际代谢率和“表观”代谢率具有重要意义，并且可能解释了鳍足类物种报道的代谢率差异。
