Nousek-McGregor Anna E, Miller Carolyn A, Moore Michael J, Nowacek Douglas P
Nicholas School for the Environment and Earth Sciences, Duke University Marine Laboratory, Beaufort, North Carolina 28516; 2Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543; 3Department of Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina 27708.
Physiol Biochem Zool. 2014 Jan-Feb;87(1):160-71. doi: 10.1086/671811. Epub 2013 Sep 20.
Buoyancy is an important consideration for diving marine animals, resulting in specific ecologically relevant adaptations. Marine mammals use blubber as an energy reserve, but because this tissue is also positively buoyant, nutritional demands have the potential to cause considerable variation in buoyancy. North Atlantic right whales Eubalaena glacialis are known to be positively buoyant as a result of their blubber, and the thickness of this layer varies considerably, but the effect of this variation on buoyancy has not been explored. This study compared the duration and rate of ascending and descending glides, recorded with an archival tag, with blubber thickness, measured with an ultrasound device, in free-swimming right whales. Ascending whales with thicker blubber had shorter portions of active propulsion and longer passive glides than whales with thinner blubber, suggesting that blubber thickness influences buoyancy because the buoyant force is acting in the same direction as the animal's movement during this phase. Whales with thinner layers also used similar body angles and velocities when traveling to and from depth, while those with thicker layers used shallower ascent angles but achieved higher ascent velocities. Such alterations in body angle may help to reduce the cost of transport when swimming against the force of buoyancy in a state of augmented positive buoyancy, which represents a dynamic response to reduce the energetic consequences of physiological changes. These results have considerable implications for any diving marine animal during periods of nutritional stress, such as during seasonal migrations and annual variations in prey availability.
浮力是潜水海洋动物需要重点考虑的因素，这导致了特定的与生态相关的适应性变化。海洋哺乳动物利用鲸脂作为能量储备，但由于这种组织也具有正浮力，营养需求有可能导致浮力产生相当大的变化。已知北大西洋露脊鲸由于其鲸脂而具有正浮力，并且这一层的厚度变化很大，但这种变化对浮力的影响尚未得到研究。本研究将用存档标签记录的自由游动的露脊鲸上升和下降滑行的持续时间和速率，与用超声设备测量的鲸脂厚度进行了比较。鲸脂较厚的上升中的鲸鱼与鲸脂较薄的鲸鱼相比，主动推进的部分更短，被动滑行的时间更长，这表明鲸脂厚度会影响浮力，因为在这个阶段浮力的方向与动物的运动方向相同。鲸脂层较薄的鲸鱼在往返深度时也使用相似的身体角度和速度，而鲸脂层较厚的鲸鱼上升角度较浅，但上升速度更高。在正浮力增强的状态下，当逆着浮力游动时，身体角度的这种改变可能有助于降低运输成本，这代表了一种动态反应，以减少生理变化带来的能量消耗。这些结果对于任何处于营养压力时期的潜水海洋动物都具有重要意义，比如在季节性迁徙和猎物可获得性的年度变化期间。
