Abstract

The study of blubber fatty acids (FAs) has attracted increasing scientific interest due mainly to its potential use as trophic markers. This is possible because most FAs are transferred unmodified from the prey to the blubber of the predator. Additionally, FAs have also been used to understand other aspects of the biology of marine mammals, including thermoregulation and reproductive stage. The aim of this study is to determine the FA composition of the blubber of the crabeater seal, which has not been reported before, and identify stratification of FAs across the blubber layer. Seals were captured in the western Antarctic Peninsula during the austral summer of 2015 and a whole blubber core (down to the muscle layer) sample was collected. The blubber core was sub-sectioned into inner and outer layers and analysed for FAs. The FA composition of crabeater seals was similar to other marine mammals, with high proportions of 18:1 omega 9, 16:1 omega 7, and 16:0. These FAs are endogenous, that is, they can be readily synthesised by mammals. However, the high proportions of 22:6 omega 3 and 20:5 omega 3 are unusual among other marine mammals. These FAs are potentially reflecting the diet of crabeater seals, as they have a dietary origin and are known to be abundant in krill, the main prey item of this predator. Inner and outer layers were significantly different indicating a stratification of blubber FAs. The pattern of stratification is ubiquitous in marine mammals, with monounsaturated FAs increasing towards the outer layer, and saturated and polyunsaturated FAs increasing towards the inner layer. This difference between inner and outer layers may indicate that they have different metabolic roles. Because most dietary FAs were more abundant in the inner layer, this is likely to be the section where the dietary process takes place. The higher proportions of monounsaturated FAs in the outer layer suggest that this section of the blubber plays a more functional role, probably related to thermoregulation, as these FAs prevent rigidity and improve fluidity, which is particularly important in cold environments. (C) 2017 The Authors. Published by Elsevier B.V.