Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, 95064, USA,
J Comp Physiol B. 2013 Dec;183(8):1065-74. doi: 10.1007/s00360-013-0773-0. Epub 2013 Aug 8.
Phocids routinely fast for extended periods. During these fasts, energetic requirements are met primarily through the catabolism of blubber lipid. To assess whether fatty acid (FA) composition changes during the postweaning fast in northern elephant seals, blubber biopsies were acquired longitudinally from 43 pups at 2.3 ± 1.5 and 55.2 ± 3.7 days postweaning in 1999 and 2000. At weaning, short-chain monounsaturated FA (SC-MUFA, ≤18 carbons) dominated the blubber while saturated FA (SFA) were found in the next highest proportion. The major FA (all ≥1 % by mass) comprised approximately 91 % of total blubber FA. In both years, 18:1n-9 and 16:0 were the most prevalent FA. Major FA mobilized during the fast consisted of polyunsaturated FA (PUFA), SFA, and SC-MUFA. Long-chain MUFA (>18 carbons) tended to be conserved. The fractional mobilization value of 20:5n-3 was the highest, resulting in significant reductions of this PUFA. Although concentrations of some blubber FA changed significantly during the postweaning fast, the general FA signature of blubber was similar at weaning and near the end of the fast. Changes in some FA differed across years. For example, the concentration of 20:4n-6, a minor PUFA, was significantly reduced in 1999 but not in 2000. FA mobilization patterns in northern elephant seal pups are somewhat similar to those reported previously for other fasting phocids and terrestrial mammals, though there are some notable differences. Differences in FA mobilization patterns across mammalian species may be related to differences in diets, geographical distribution, environmental factors, physiological adaptations, and life history stage.
豹形海豹通常会长时间禁食。在这些禁食期间，能量需求主要通过分解鲸脂中的脂质来满足。为了评估在新生幼仔的禁食期间，北象海豹的脂肪酸（FA）组成是否会发生变化，我们在 1999 年和 2000 年，从 43 只 2.3±1.5 日龄和 55.2±3.7 日龄的幼仔身上，纵向采集了鲸脂活检。在断奶时，短链单不饱和脂肪酸（SC-MUFA，≤18 个碳原子）在鲸脂中占主导地位，而饱和脂肪酸（SFA）的比例次之。主要 FA（所有 FA 的质量百分比均≥1%）约占鲸脂总 FA 的 91%。在这两年中，18:1n-9 和 16:0 是最普遍的 FA。在禁食期间，主要动员的 FA 包括多不饱和脂肪酸（PUFA）、SFA 和 SC-MUFA。长链 MUFA（>18 个碳原子）趋于被保留。20:5n-3 的动员分数最高，导致这种 PUFA 的显著减少。尽管在新生幼仔的禁食期间，一些鲸脂 FA 的浓度发生了显著变化，但在断奶时和禁食接近尾声时，鲸脂的一般 FA 特征相似。在某些 FA 方面，不同年份的变化也有所不同。例如，1999 年，一种次要的 PUFA-20:4n-6 的浓度显著降低，但 2000 年并非如此。北象海豹幼仔的 FA 动员模式与先前报道的其他禁食海豹和陆地哺乳动物的模式有些相似，但也存在一些显著差异。不同哺乳动物物种的 FA 动员模式的差异可能与饮食、地理分布、环境因素、生理适应和生活史阶段的差异有关。
