Fatty acid composition in blubber, heart and brain from phocid seals

Abstract

The fatty acid composition of phocid seals was investigated in order to map the possible stratification of fatty acids in the depot fat and to detect possible differences between different tissues and between the four species grey seal (Halichoerus grypus), harbour seal (Phoca vitulina), ringed seal (Phoca hispida) and harp seal (Phoca groenlandica). We used a chemometric method in this analysis: the fatty acids were determined by gas chromatography, and the relative amounts of fatty acids were treated by principal component analysis. Analysis of the depot fat in the four species indicates that the fatty acid composition of the blubber varies along a gradient from the epidermis. We are able to distinguish between three distinct vertical layers. With increasing depth from the epidermis, the amount of saturated and long-chained monounsaturated fatty acids in the blubber fat increased, while the amount of short-chained monounsaturated fatty acids decreased. The four seal species exhibited differences in fatty acid composition in the outermost layer of the blubber. In contrast, the middle and inner layers did not show differences between species. We also analysed the fatty acid composition of heart and brain tissue from harp seals. The three tissues had distinctly different profiles.