Comparison of the fatty acid profile of muscle neutral lipids and phospholipids of up-river anadromous sea lamprey (Petromyzon marinus L.) from three Portuguese river basins

Composition of fatty acid profile of muscle neutral lipids (NL) and phospholipids (PL) of sea lamprey that enter the Portuguese rivers Minho, Tagus and Guadiana during their non-trophic spawning migration was analysed. The fatty acid profile exhibited differences in the percentage among NL and PL and between river basins. Similarities were found in the fatty acid profile of NL. Monounsaturated fatty acids (MUFA) were the most representative, followed by saturated fatty acids (SFA) and finally by polyunsaturated fatty acids (PUFA). Monoenic 16:1 and 18:1ω9 formed a considerable percentage of total fatty acids, followed by SFA 14:0 and 16:0. EPA and DHA were the dominant PUFA fatty acids. In terms of NL, the fatty acid that contributed for the discrimination between the three river basins was 18:1ω7. Individuals from the Minho river basin exhibited a different fatty acid profile of PL characterised by a low PUFA percentage when compared with lampreys from the Tagus and Guadiana river basins. Muscle PL fraction showed that the two monoenes, 16:1 and 18:1ω9, occurred at high percentage, followed by 16:0 and 14:0 (SFA). Among PUFA, DHA was the most representative fatty acid. The fatty acids that contributed to the separation between the three river basins were 16:0, 18:4ω3 and 24:1ω9. Although the results point in the direction of a possible difference between the fatty acid composition of the NL and PL fractions in the muscle samples from the three river basins, further studies, especially in tissues where fatty acid composition will be less sensitive to diet and environmental factors, are necessary to confirm this hypothesis.