Fatty acid composition of tissue samples from Arctic walruses (Odobenus rosmarus rosmarus) and their prey

Blubber biopsies were collected from 18 adult male walruses from Svalbard, Norway. The biopsies were taken vertically through the skin and the entire blubber layer down to, but not including, the muscle layer. Fatty acid (FA) compositions of inner blubber, outer blubber and dermis of the walruses and of potential prey organisms were determined. The three layers differed significantly from one another in FA composition. Generally, the inner blubber contained more long-chained monounsaturated, saturated and polyunsaturated FAs, while the outer blubber and dermis contained more short-chained monounsaturated FAs. This stratification is similar to what has been observed in other marine mammal species. However, differences between layers were less pronounced than in most other species, possibly because the extremely thick overlying dermis of walruses provides an insulating shield, which affects the FA composition of the outer blubber. The FA composition of the potential prey organisms was different from that of the blubber of the walruses, although more similar to the inner blubber than to the outer blubber or dermis. FA composition in the inner blubber was not significantly correlated with age (assessed by tusk volume), while the FA composition of the outer blubber and dermis were significantly correlated with age.本研究从挪威斯瓦尔巴群岛的18头成年雄性海象身上采集了鲸脂活检样本。该活检采用垂直取样方式，穿透皮肤及全层鲸脂，直至肌肉层上方（不包含肌肉层）。研究测定了海象的内层鲸脂、外层鲸脂及真皮组织，以及潜在猎物生物的脂肪酸（Fatty acid, FA）组成。结果显示，这三层组织的脂肪酸组成存在显著差异：整体而言，内层鲸脂的长链单不饱和脂肪酸、饱和脂肪酸及多不饱和脂肪酸含量更高，而外层鲸脂与真皮组织的短链单不饱和脂肪酸占比更高。这种分层特征与其他海洋哺乳动物中观测到的结果类似。不过，各层间的差异相较于多数其他物种而言并不显著，这可能是因为海象极厚的表层真皮构成了隔热屏障，进而影响了外层鲸脂的脂肪酸组成。潜在猎物生物的脂肪酸组成与海象鲸脂的脂肪酸组成存在差异，但其与内层鲸脂的相似性高于与外层鲸脂或真皮组织的相似性。内层鲸脂的脂肪酸组成与年龄（通过獠牙体积评估）无显著相关性，而外层鲸脂与真皮组织的脂肪酸组成则与年龄存在显著相关性。