Thometz Nicole M, Murray Michael J, Williams Terrie M
Department of Ecology and Evolutionary Biology, Long Marine Laboratory, University of California, 100 Shaffer Road, Santa Cruz, California 95060; 2Monterey Bay Aquarium, 886 Cannery Row, Monterey, California 93940.
Physiol Biochem Zool. 2015 May-Jun;88(3):311-27. doi: 10.1086/681019. Epub 2015 Mar 18.
Small body size, large lungs, and dense pelage contribute to the unique challenges faced by diving sea otters (Enhydra lutris) when compared to other marine mammals. Here we determine the consequences of large lungs on the development of diving ability in southern sea otters (Enhydra lutris nereis) by examining the ontogeny of blood, muscle, and lung oxygen stores and calculating aerobic dive limits (cADL) for immature and mature age classes. Total oxygen storage capacity matures rapidly in sea otters, reaching adult levels by 2 mo postpartum. But this result is driven by exceptional lung capacity at birth, followed by a decrease in mass-specific lung volume with age. Blood and muscle oxygen stores remain well below adult values before weaning, with large pups exhibiting 74% and 54% of adult values, respectively. Slow muscle development limits the capacity of immature sea otters to dive against high positive buoyancy due to comparatively large lungs. Immature sea otters diving with total lung capacity (TLC) experience up to twice the mass-specific positive buoyancy as adults diving with TLC but can reduce these forces to comparable adult levels by using a smaller diving lung volume (DLV). The cADL of a juvenile with DLV is 3.62 min, while the cADL of an adult with TLC is 4.82 min. We find that the magnitude of positive buoyancy experienced by sea otters changes markedly with age and strongly influences the ontogeny of diving ability in this species.
与其他海洋哺乳动物相比，体型小、肺部大以及毛发浓密给海獭（Enhydra lutris）潜水带来了独特挑战。在此，我们通过研究血液、肌肉和肺部氧气储备的个体发育情况，并计算未成熟和成熟年龄组的有氧潜水极限（cADL），来确定大肺部对南海獭（Enhydra lutris nereis）潜水能力发展的影响。海獭的总氧气储存能力迅速成熟，产后2个月时达到成年水平。但这一结果是由出生时超常的肺容量驱动的，随后随着年龄增长，单位质量肺容量下降。断奶前，血液和肌肉中的氧气储备远低于成年水平，大幼崽的这两项指标分别为成年值的74%和54%。由于肺部相对较大，肌肉发育缓慢限制了未成熟海獭对抗高正浮力的潜水能力。未成熟海獭以总肺容量（TLC）潜水时，单位质量的正浮力是成年海獭以TLC潜水时的两倍，但通过使用较小的潜水肺容量（DLV），它们可以将这些力降低到与成年海獭相当的水平。幼崽以DLV潜水时的cADL为3.62分钟，而成体以TLC潜水时的cADL为4.82分钟。我们发现，海獭所经历的正浮力大小随年龄显著变化，并强烈影响该物种潜水能力的个体发育。
