Lipid metabolism of minke whale and pacific white-sided dolphin in Korean waters and implications for feeding ecology

Abstract

In order to understand the lipid metabolism of minke whale (Balaenoptera acutorostrata) and pacific white-sided dolphin (Lagenorhynchus obiquidens), lipid content, composition, and compound-specific stable isotope content were examined in their blubber. Mean lipid content of the two species ranged from 54 to 92% of wet weight, with dominance of triacylglycerols (94 to 99% of total lipids). Although lipid content and composition in the blubber were similar between two species, the relative abundance of some fatty acids (e.g. 14:1, 16:0, 18:1n-7, 18:0, 20:1n-11 and 20:2) were significantly different. These differences might be related to their diets because bulk stable isotope ratios (δ13C, δ15N) in the skin indicated the minke whale mainly feeds on krill and anchovy but pacific white-sided dolphin mainly fed on fishes. However, we found a significant shift of FA composition within blubber layers for both species. While monounsaturated FAs (MUFAs) gradually increased from the inner (near muscle) to the outer layer (near skin), polyunsaturated FAs (PUFAs) decreased from the inner to outer layer. These compositional shifts in the blubber could be related to their physiological needs (i.e. thermoregulation, streaming, buoyancy and energy storage). With the addition of compound-specific stable isotope analysis, detailed information on lipid metabolism and the diet history of these marine mammals would be disclosed.