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Preliminary study – stratification and inter– specific differences in fatty acid composition of dolphin’s blubber

Cetaceans have been shown to exhibit three layers within the blubber with each layer performing a different function ; for example, stable outer layer used for structural support, more variable inner layer for energy storage. The aim was to determine fatty acid (FA) composition of blubber in two dolphin species found in the Adriatic Sea. The study was conducted on 8 animals, bottlenose dolphin (Tursiops truncatus ; 2 females, F and 4 males, M) and striped dolphin (Stenella coeruleoalba ; 1 F, 1 M) sampled during 2018. Blubber was divided horizontally into outer (OL), middle (ML) and inner layer (IL). Tissue samples were homogenized, total lipids extracted than composition of FA was determined by gas chromatography. Blubber OL and ML of striped dolphin was dominated by monounsaturated FA (MUFA, 55.2±8.2% ; 49.1±2.8%) while in IL by polyunsaturated FA (PUFA, 41.7±2.6%). In contrast, all three blubber layers of bottlenose dolphin were dominated by MUFA (OL, 63.1±6.6% ; ML, 55.1±6.8% ; IL, 49.0±5.7%). Regarding blubber FA composition in striped dolphin most differences were between ML vs. IL (very long n-3 PUFA, 14.1±4.8% vs. 36.8±3.4% ; n-3, 15.2±4.2% vs. 37.5±3.6%, all at p<0.05). In bottlenose dolphin most differences were between OL vs. IL (C18:0, 1.5±0.2% vs. 3.8±1.5% ; MUFA, 63.1±6.6% vs. 49.0±5.7% ; p<0.05). When testing differences in blubber FA composition for striped vs. bottlenose dolphin, most differences were in ML (C18:2n-6, 5.3±3.1% vs. 1.9±0.5% ; C20:4n-3, 0.1±0.1% vs. 0.6±0.2% ; n-6, 6.6±3.2% vs. 3.4±0.8% ; p<0.05) and in IL (C22:6n-3, 27.2±13.8% vs. 10.5±2.3% ; PUFA, 41.7±2.6% vs. 22.1±2.9% ; n-3, 37.5±3.6% vs. 18.2±2.6% ; very long n- 3 PUFA, 36.8±3.7% vs. 17.0±2.3% ; p<0.05). Although more samples are required, this stratification can be attributed to different levels of metabolic activity within layers. Differences in FA composition within and between species could be due to diet, since many long-chain PUFAs can be traced back to a specific organism and geographic location in the food chain

fatty acid ; blubber ; Cetaceans

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