Can Heart Tissue Fatty Acid Profile be Used as a Tool to Discriminate Sea Lamprey Populations in Several Portuguese River Basins?

This study proposes to evaluate the use of heart tissue fatty acid signature as a possible discriminating tool for sea lamprey Petromyzon marinus (L.) populations sampled in Portuguese river basins. Adult sea lampreys were collected near the river mouth of eight Portuguese river basins (i.e. Minho, Lima, Cávado, Douro, Vouga, Mondego, Tagus and Guadiana) at the beginning of their spawning migration. Heart total lipid extraction was obtained by accelerated solvent extraction (ASE) and FAME were prepared by transesterification with methanol-boron trifluoride and analysed by GC. FAME were identified by comparison of their retention times with known standards chromatographed in identical gas chromatography conditions. The fatty acid profile of the heart tissue varied among individuals of the different river basins. A Multiple Discriminant Analysis (MDA) was employed to identify which fatty acid contributed most to these differences. The MDA proved to be statistically significant and the overall corrected classification rate estimated from cross-validation procedure was 86.2%. Although in Tagus and Guadiana most of the individuals were correctly classified (100% and 94.7%, respectively), there are a few individuals of the other 5 watersheds that have profiles identical to those observed in these two river basins. The results are discussed in terms of fatty acid origin and hypothesis concerning the migratory behavior that could lead to these results. The fatty acid profile of heart is considered more stable than other organs, but it still exhibits some variability. This study seems to point out the potential for fatty acid compositions to discriminate sea lampreys from Portuguese river basins. Detected differences are probably related with environmental variables that they may have been exposed during early stages of their life cycle.