Keicher Lara, O'Mara M Teague, Voigt Christian C, Dechmann Dina K N
Department of Migration and Immuno-ecology, Max Planck Institute for Ornithology, 78315 Radolfzell, Germany
Department of Biology, University of Konstanz, 78464 Konstanz, Germany.
J Exp Biol. 2017 Aug 1;220(Pt 15):2834-2841. doi: 10.1242/jeb.159947. Epub 2017 May 25.
Small non-migratory mammals with Northern distribution ranges apply a variety of behavioural and physiological wintering strategies. A rare energy-saving strategy is Dehnel's phenomenon, involving a reduction and later regrowth of the body size, several organs and parts of the skeleton in red-toothed shrews (Soricidae). The size extremes coincide with major life stages. However, the physiological consequences for the shrew's metabolism remain poorly understood. In keeping with the energetic limitations that may induce the size changes, we hypothesised that metabolic incorporation rates should remain the same across the shrews' lifetimes. In contrast, fat turnover rates should be faster in smaller subadults than in large juveniles and regrown adults, as the metabolic activity of fat tissue increases in winter individuals (subadults). Measuring the changes in the ratio of exhaled stable carbon isotopes, we found that the baseline diet of shrews changed across the season. A diet switch experiment showed that incorporation rates were consistently rapid (=38.2±21.1-69.3±53.5 min) and did not change between seasons. As predicted, fat turnover rates were faster in size-reduced subadults (=2.1±1.3 h) compared with larger juveniles (=5.5±1.7 h) and regrown adults (=5.0±4.4 h). In all three age/size classes, all body fat was turned over after 9-24 h. These results show that high levels of nutrient uptake are independent of body size, whereas fat turnover rates are negatively correlated with body size. Thus, the shrews might be under higher pressure to save energy in winter and this may have supported the evolution of Dehnel's phenomenon.
分布范围在北方的小型非迁徙性哺乳动物会采用多种行为和生理过冬策略。一种罕见的节能策略是德内尔现象，即红齿鼩鼱（鼩鼱科）的身体大小、几个器官和部分骨骼会缩小，之后再重新生长。大小极值与主要生命阶段相吻合。然而，鼩鼱新陈代谢的生理后果仍知之甚少。鉴于可能导致体型变化的能量限制，我们推测鼩鼱一生中的代谢掺入率应保持不变。相比之下，较小的亚成体的脂肪周转率应该比较大的幼体和重新生长后的成体更快，因为冬季个体（亚成体）的脂肪组织代谢活性会增加。通过测量呼出的稳定碳同位素比率的变化，我们发现鼩鼱的基础饮食在整个季节中会发生变化。一项饮食转换实验表明，掺入率一直很快（=38.2±21.1 - 69.3±53.5分钟），且在不同季节之间没有变化。正如预测的那样，体型缩小的亚成体（=2.1±1.3小时）的脂肪周转率比更大的幼体（=5.5±1.7小时）和重新生长后的成体（=5.0±4.4小时）更快。在所有三个年龄/体型类别中，所有身体脂肪在9 - 24小时后都会更新。这些结果表明，高营养摄取水平与体型无关，而脂肪周转率与体型呈负相关。因此，鼩鼱在冬季可能面临更大的节能压力，这可能支持了德内尔现象的进化。
