Kvadsheim P H, Folkow L P
Department of Arctic Biology, University of Tromsø, Norway.
Acta Physiol Scand. 1997 Nov;161(3):385-95. doi: 10.1046/j.1365-201X.1997.00235.x.
The trunk of marine mammals is encased in a blubber layer which provides thermal insulation that can be changed by circulatory adjustments. The extremities, on the other hand, are poorly insulated but have vascular arrangements constructed for prevention or promotion of heat loss depending on the thermal state of the animal. We have studied the importance of different body parts as sites for heat dissipation and also assessed the effect of circulatory adjustments on heat transfer through blubber, by combining direct measurements of heat flux from the flippers and trunk with simultaneous recordings of temperature gradients through the blubber and metabolic rates of harp seals (Phoca groenlandica) subjected to water temperatures between 1 and 24 degrees C. We also determined the thermal conductivity of blubber samples from the same animals after death, and compared this with the insulative properties of live blubber. At the lowest water temperatures, the insulative properties of live blubber were similar to those of dead blubber, and heat loss from the flippers only accounted for 2-6% of the metabolic heat production. As heat load increased with increasing water temperatures, the fraction of heat lost from the flippers increased, to 19-48% at 24 degrees C, while the fraction lost from the trunk decreased, despite an increase in the convective (circulatory) heat transfer through the blubber layer.
海洋哺乳动物的躯干被一层鲸脂包裹着，这层鲸脂提供了隔热功能，其隔热效果可通过循环调节来改变。另一方面，其四肢的隔热性较差，但具有根据动物的热状态来防止或促进热量散失的血管结构。我们通过将直接测量鳍状肢和躯干的热通量与同时记录通过鲸脂的温度梯度以及在水温为1至24摄氏度的格陵兰海豹（Phoca groenlandica）的代谢率相结合，研究了身体不同部位作为散热部位的重要性，并评估了循环调节对通过鲸脂的热传递的影响。我们还测定了同一动物死后鲸脂样本的热导率，并将其与活体鲸脂的隔热性能进行了比较。在最低水温下，活体鲸脂的隔热性能与死体鲸脂相似，鳍状肢的热量散失仅占代谢产热的2%至6%。随着水温升高热负荷增加，鳍状肢散失的热量比例增加，在24摄氏度时达到19%至48%，而躯干散失的热量比例下降，尽管通过鲸脂层的对流（循环）热传递有所增加。
