Department of Ornithology, Max Planck Institute for Biological Intelligence, Seewiesen 82319, Germany.
Edward Grey Institute, Department of Biology, University of Oxford, Oxford, UK.
Biol Lett. 2023 Nov;19(11):20230391. doi: 10.1098/rsbl.2023.0391. Epub 2023 Nov 22.
In many animals, males compete for access to fertile females. The resulting sexual selection leads to sex differences in morphology and behaviour, but may also have consequences for physiology. Pectoral sandpipers are an arctic-breeding polygynous shorebird in which males perform elaborate displays around-the-clock and move over long distances to sample potential breeding sites, implying the need for physiological adaptations to cope with extreme endurance. We examined the oxygen carrying capacity of pectoral sandpipers, measured as the volume percentage of red blood cells in blood (haematocrit, Hct). We found a remarkable sex difference in Hct levels, with males having much higher values (58.9 ± 3.8 s.d.) than females (49.8 ± 5.3 s.d.). While Hct values of male pectoral sandpipers are notable for being among the highest recorded in birds, the sex difference we report is unprecedented and more than double that of any previously described. We also show that Hct values declined after arrival to the breeding grounds in females, but not in males, suggesting that males maintain an aerobic capacity during the mating period equivalent to that sustained during trans-hemispheric migration. We conclude that sexual selection for extreme physical performance in male pectoral sandpipers has led to exceptional sex differences in oxygen carrying capacity.
在许多动物中，雄性为了获得可育的雌性而竞争。由此产生的性选择导致了形态和行为上的性别差异，但也可能对生理产生影响。斑胸滨鹬是一种北极繁殖的多配偶性涉禽，雄性会全天候进行精心的表演，并长途跋涉寻找潜在的繁殖地，这意味着它们需要生理适应来应对极端耐力。我们研究了斑胸滨鹬的携氧能力，以血液中红细胞的体积百分比（血细胞比容，Hct）来衡量。我们发现 Hct 水平存在显著的性别差异，雄性的 Hct 值（58.9±3.8 s.d.）远高于雌性（49.8±5.3 s.d.）。虽然雄性斑胸滨鹬的 Hct 值是鸟类中记录的最高值之一，但我们报告的性别差异是前所未有的，超过了以前描述的任何性别差异的两倍。我们还表明，雌性到达繁殖地后 Hct 值下降，但雄性没有，这表明雄性在交配期维持的有氧能力与跨半球迁徙时相同。我们的结论是，雄性斑胸滨鹬对极端身体表现的性选择导致了其携氧能力的显著性别差异。
