Clark Timothy Darren, Hinch S G, Taylor B D, Frappell P B, Farrell A P
Faculty of Land and Food Systems, University of British Columbia, Vancouver V6T1Z4, Canada.
J Comp Physiol B. 2009 Jul;179(5):663-71. doi: 10.1007/s00360-009-0349-1. Epub 2009 Feb 28.
Upon reaching sexual maturity, several species of male salmonids possess a relative ventricular mass (rM(V)) that may be up to 90% larger than females. This can increase maximum cardiac stroke volume and power output, which may be beneficial to increasing the oxygen transport capacity of male salmonids during the spawning period. It may be further hypothesized, therefore, that other variables within the circulatory oxygen transport cascade, such as blood oxygen-carrying capacity and heart rate, are similarly enhanced in reproductively mature male salmonids. To test this idea, the present study measured a range of circulatory oxygen transport variables in wild male and female sockeye salmon (Oncorhynchus nerka) during their spawning period, following a 150 km migration from the ocean. The rM(V) of male fish was 13% greater than females. Conversely, the haemoglobin concentration ([Hb]) of female fish was 19% higher than males, indicative of a greater blood oxygen-carrying capacity (138 vs. 116 ml O2 l(-1), respectively). Surgically implanted physiological data loggers revealed a similar range in heart rate for both sexes on the spawning ground (20-80 beats min(-1) at 10 degrees C), with a tendency for male fish to spend a greater percentage of time (64%) than females (49%) at heart rates above 50 beats min(-1). Male fish on average consumed significantly more oxygen than females during a 13-h respirometry period. However, routine oxygen consumption rates (.)MO2 ranged between 1.5 and 8.5 mg min(-1) kg(-1) for both sexes, which implies that males did not inherently possess markedly higher routine aerobic energy demands, and suggests that the higher [Hb] of female fish may compensate for the smaller rM(V). These findings reject the hypothesis that all aspects of the circulatory oxygen transport cascade are inherently superior in male sockeye salmon. Instead, it is suggested that any differences in (.)MO2 between sexually mature male and female sockeye salmon can likely be attributed to activity levels.
达到性成熟时，几种雄性鲑科鱼类的相对心室质量（rM(V)）可能比雌性大90%。这会增加最大心搏量和功率输出，这可能有利于在产卵期提高雄性鲑科鱼类的氧气运输能力。因此，可能进一步推测，循环氧气运输级联中的其他变量，如血液携氧能力和心率，在生殖成熟的雄性鲑科鱼类中也会有类似增强。为了验证这一想法，本研究在野生雄性和雌性红大马哈鱼（Oncorhynchus nerka）从海洋洄游150公里后的产卵期，测量了一系列循环氧气运输变量。雄鱼的rM(V)比雌鱼大13%。相反，雌鱼的血红蛋白浓度（[Hb]）比雄鱼高19%，这表明其血液携氧能力更强（分别为138和116 ml O2 l(-1)）。手术植入的生理数据记录器显示，在产卵地两性的心率范围相似（10摄氏度时为20 - 80次/分钟），雄鱼心率高于50次/分钟的时间百分比（64%）往往比雌鱼（49%）更高。在13小时的呼吸测量期内，雄鱼平均消耗的氧气明显多于雌鱼。然而，两性的常规耗氧率（.)MO2在1.5至8.5 mg min(-1) kg(-1)之间，这意味着雄鱼并非天生具有明显更高的常规有氧能量需求，这表明雌鱼较高的[Hb]可能弥补了较小的rM(V)。这些发现否定了雄性红大马哈鱼循环氧气运输级联的所有方面天生更优越的假设。相反，表明性成熟的雄性和雌性红大马哈鱼之间（.)MO2的任何差异可能都归因于活动水平。
