Feeding strategy assessment through fatty acid profiles in muscles of adult sea lampreys from the western Iberian coast

The fatty acid signature of sea lamprey Petromyzon marinus (L.) muscle was used as a tool to detect feeding strategies used during the parasitic marine trophic phase of the species. Adult sea lampreys were collected near the mouth of six Portuguese rivers (Minho, Lima, Douro, Vouga, Mondego and Tagus) and muscle fatty acid profile was characterized. The analysis of fatty acid composition of muscle neutral lipids showed the formation of two groups, indicating that two feeding strategies may have been used by sea lampreys during the parasitic phase, based on the availability of omega-3 and omega-6 PUFA and on evidence of phytoplankton/zooplankton and bacterial detritus contribution in the sea lamprey host preferences. Two distinct lipid profiles were observed, probably related to two different trophic approaches, one typical of a top predator of a marine food web with a planktonic support, and the other much more diverse, including the same planktonic markers, together with biochemical clues that probably resulted from a parasitic phase that directly targeted fish that consumed detritus and benthic algae and/or fish from a food web with a detritivorous base.