Marine endotherms in the polar regions face a formidable thermal challenge when swimming in cold water. Hence, they use morphological (fat, blubber) adjustment and peripheral vasoconstriction to reduce demands for heat production in water. The animals then regain normothermia when resting ashore. In the king penguin (Aptenodytes patagonicus) metabolic rate is lower in fed than in fasted individuals during subsequent rewarming on land. This has been suggested to be a consequence of diversion of blood flow to the splanchnic region in fed birds, which reduces peripheral temperatures. However, peripheral temperatures during recovery have never been investigated in birds with different nutritional status. The aim of this study was, therefore, to measure subcutaneous and abdominal temperatures during the rewarming phase on land in fasted and fed king penguins, and investigate to which extent any different rewarming were reflected in recovery metabolic rate (MRR) after long term immersion in cold water. We hypothesized that fed individuals would have a slower increase of subcutaneous temperatures compared to fasted penguins, and a correspondingly lower MRR. Subcutaneous tissues reached normothermia after 24.15 (back) and 21.36 min (flank), which was twice as fast as in the abdomen (46.82 min). However, recovery time was not affected by nutritional condition. MRR during global rewarming (4.56 ± 0.42 W kg-1) was twice as high as resting metabolic rate (RMR; 2.16 ± 0.59 W kg-1). However, MRR was not dependent on feeding status and was significantly elevated above RMR only until subcutaneous temperature had recovered. Contrary to our prediction, fed individuals did not reduce the subcutaneous circulation compared to fasted penguins and did not show any changes in MRR during subsequent recovery. It seems likely that lower metabolic rate in fed king penguins on land reported in other studies might not have been caused primarily by increased circulation to the visceral organs.

中文翻译：

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王企鹅长期浸泡在冷水中后皮下和腹部复温的代谢成本

在极地地区的海洋恒温动物在冷水中游泳时面临着巨大的热挑战。因此，他们使用形态（脂肪、脂肪）调整和外周血管收缩来减少对水中产热的需求。当这些动物在岸上休息时，它们会恢复正常体温。在随后的陆地复温期间，王企鹅 (Aptenodytes patagonicus) 进食后的代谢率低于禁食个体。这被认为是被喂食的鸡的内脏区域的血流分流的结果，这降低了外周温度。然而，从未在不同营养状况的鸟类中研究恢复期间的外周温度。因此，本研究的目的是，测量陆地上禁食和喂食的帝企鹅在复温阶段的皮下和腹部温度，并研究长期浸泡在冷水中后，任何不同的复温在多大程度上反映在恢复代谢率 (MRR) 中。我们假设与禁食的企鹅相比，进食的个体皮下温度的升高速度较慢，并且相应的 MRR 较低。皮下组织在 24.15（背部）和 21.36 分钟（侧腹）后达到常温，这是腹部（46.82 分钟）的两倍。然而，恢复时间不受营养状况的影响。全球复温期间的 MRR (4.56 ± 0.42 W kg-1) 是静息代谢率 (RMR; 2.16 ± 0.59 W kg-1) 的两倍。然而，MRR 不依赖于喂养状态，并且仅在皮下温度恢复之前显着高于 RMR。与我们的预测相反，与禁食企鹅相比，进食的个体并没有减少皮下循环，并且在随后的恢复过程中没有显示 MRR 的任何变化。其他研究报告的陆上喂食帝企鹅的较低代谢率似乎不是主要由内脏器官循环增加引起的。