Site-specific fatty acid composition in adipose tissues of several northern aquatic and terrestrial mammals

Abstract

Site-specific differences in fatty acid compositions (by gas-liquid chromatography) were compared in aquatic, semiaquatic and terrestrial mammals: the ringed seals ( Phoca hispida hispida and P. h. botnica), otter ( Lutra lutra), raccoon dog ( Nyctereutes procyonoides), brown bear ( Ursus arctos) and grey wolf ( Canis lupus). In addition, we briefly discuss our earlier results for the Canadian beaver ( Castor canadensis) and muskrat ( Ondatra zibethicus). In both aquatic and terrestrial species, large amounts of Δ9-monounsaturated fatty acids (MUFAs) and small amounts of saturated fatty acids and exogenous long-chain MUFAs were found in the cold tissues of the extremities. In seals, the poikilothermic outer blubber had these characteristics and differed from the inner blubber. On the other hand, the subcutaneous and inner fat depots of the coated semiaquatic and terrestrial mammals were uniform. In the bare extremities, however, these mammals also had an excess of A9-MUFAs. The degree of Δ9-desaturation in the outer blubber of the seals was significantly correlated with age. The excess of Δ9-MUFAs in the bare extremities of land mammals increased the overall double bond content of these tissues compared with the inner depots. In contrast, due to the large amounts of dietary polyunsaturated fatty acids, this was not found in the aquatic and semiaquatic species. The observed site-specific differences are discussed as possible inherited evolutionary adaptations to low temperature of the tissues.