College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 2150 Koyukuk Dr., Fairbanks, AK, 99775, USA.
Department of Biological Sciences, California Polytechnic State University, 1 Grand Ave., San Luis Obispo, CA, 93407, USA.
J Comp Physiol B. 2019 Aug;189(3-4):501-511. doi: 10.1007/s00360-019-01214-y. Epub 2019 Mar 28.
Many animals exhibit ontogenetic changes associated with adaptations for survival. Harp seals (Pagophilus groenlandicus) live in the Arctic and rely on thick insulation to maintain thermal homeostasis. Adult harp seals primarily use blubber for insulation, but newborn harp seals rely on a lanugo pelt while nursing, as their blubber layer develops and their first-year pelage grows. This study compared ontogenetic changes in the thermal properties of harp seal pelts in water and in air. Thermal conductivity, pelt thickness, and thermal resistance were measured in water for pelts of harp seal neonates (1 day old), thin whitecoats (4 day old), fat whitecoats (9 day old), ragged jackets (2 week old), beaters (3 week old), and adults and compared to previously published measurements made on the same pelts in air. Pelt conductivity was significantly higher in water than air for pre-molt and molting pups (P ≤ 0.031). Unlike adult pelage, which flattened underwater, lanugo hairs lifted underwater, a phenomenon that has not been reported previously. Thermal resistance of the pelt was significantly reduced in water compared to air for neonates and thin whitecoats (P ≤ 0.0001). A mathematical model of conductive heat transfer for an ellipsoid body showed volume-specific heat loss in water decreased and then stabilized as harp seals aged (P = 0.0321) and was significantly higher for neonates, thin whitecoats, and ragged jackets in water than in air (P ≤ 0.0089). Overall, pelt function is reduced in water for harp seal pups with lanugo, and this renders neonates and thin whitecoats particularly vulnerable to heat loss if submerged.
许多动物表现出与生存适应相关的个体发育变化。格陵兰海豹（Pagophilus groenlandicus）生活在北极地区，依靠厚厚的绝缘材料来维持体温平衡。成年格陵兰海豹主要使用鲸脂作为绝缘材料，但新生的格陵兰海豹在哺乳期间依赖于一层胎毛，因为它们的鲸脂层正在发育，它们的第一年皮毛也在生长。本研究比较了格陵兰海豹在水中和空气中的皮毛热特性的个体发育变化。在水中测量了格陵兰海豹幼崽（1 天大）、白色薄外套（4 天大）、脂肪白色外套（9 天大）、破旧夹克（2 周大）、打手（3 周大）和成年海豹的皮毛的热导率、皮毛厚度和热阻，并与之前在空气中对同一皮毛进行的测量进行了比较。在蜕皮前和蜕皮期的幼崽（P≤0.031）中，皮毛的导电性在水中比空气中显著更高。与成年海豹的皮毛不同，胎毛在水下会竖起，这是以前没有报道过的现象。与空气相比，幼崽和白色薄外套的皮毛在水中的热阻显著降低（P≤0.0001）。对于一个椭球体的传导传热的数学模型表明，随着格陵兰海豹的年龄增长（P=0.0321），水中的体积比热损失减少，然后稳定下来，并且水中的幼崽、白色薄外套和破旧夹克的热损失比空气显著更高（P≤0.0089）。总的来说，对于有胎毛的格陵兰海豹幼崽来说，皮毛在水中的功能降低，如果它们被淹没，这会使幼崽和白色薄外套特别容易失去热量。
