Biomechanics and energetics in aquatic and semiaquatic mammals: Platypus to whale
Biomechanics and energetics in aquatic and semiaquatic mammals: Platypus to whale
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DOI：
10.1086/318108
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发表时间：
2000-11-01
影响因子：
1.6
通讯作者：
Fish, FE
中科院分区：
文献类型：
--
作者：
Fish, FE
各种哺乳动物的血统已经二次入侵了这片水域。为了在水介质中运动和调节体温，哺乳动物发展了一系列的形态、生理和行为适应。在影响能量的一系列适应上，半水栖和全水栖哺乳动物之间有明显的差异。半水栖哺乳动物通过划桨游泳，与使用水生哺乳动物的摆动水翼相比，这是低效的。与水下哺乳动物相比，半水栖哺乳动物在水面上游泳，并经历更大的阻力，通过波浪阻力增加。一种致密的、不可弄湿的皮毛将半水栖哺乳动物隔绝，而水生哺乳动物则使用一层鲸脂。毛皮在提供隔热和正浮力的同时，需要很高的能量来进行维护，并限制了潜水深度。鲸脂塑造了身体的轮廓以减少阻力，是一种能量储备，浮力随着深度的增加而不会损失。尽管半水生动物的能量成本很高，但这些动物代表了祖先陆地哺乳动物和它们的完全水生后代之间进化中间的现代类似物。正是这些中间动物表明了哪些潜在的选择因素和机械约束可能指导了更多衍生水生生物的进化。
A variety of mammalian lineages have secondarily invaded the water. To locomote and thermoregulate in the aqueous medium, mammals developed a range of morphological, physiological, and behavioral adaptations. A distinct difference in the suite of adaptations, which affects energetics, is apparent between semiaquatic and fully aquatic mammals. Semiaquatic mammals swim by paddling, which is inefficient compared to the use of oscillating hydrofoils of aquatic mammals. Semiaquatic mammals swim at the water surface and experience a greater resistive force augmented by wave drag than submerged aquatic mammals. A dense, nonwettable fur insulates semiaquatic mammals, whereas aquatic mammals use a layer of blubber. The fur, while providing insulation and positive buoyancy, incurs a high energy demand for maintenance and limits diving depth. Blubber contours the body to reduce drag, is an energy reserve, and suffers no loss in buoyancy with depth. Despite the high energetic costs of a semiaquatic existence, these animals represent modern analogs of evolutionary intermediates between ancestral terrestrial mammals and their fully aquatic descendants. It is these intermediate animals that indicate which potential selection factors and mechanical constraints may have directed the evolution of more derived aquatic forms.