Local host fish-Anisakis spp. parasite lipid interplay: A lipidomic characterization of Anisakis larvae and parasitized tissue of its host fish, the European hake (Merluccius merluccius)

Anisakid nematodes are widespread marine parasites with zoonotic potential and possible impact on fish nutritional quality. In this study, we investigated the lipid composition of L3 Anisakis larvae, the host fish tissue adjacent to the presence of parasites (belly flaps) and the tail (used as a control due to the absence of Anisakis larvae) of parasitized European hake ( Merluccius merluccius ), combining fatty acid profiling and advanced lipidomics. Fatty acid analysis revealed distinct profiles between the Anisakis spp. parasites and hake tissues, with Anisakis larvae showing higher levels of stearic acid (18:0), vaccenic acid (18:1 n -7), and linoleic acid (18:2 n -6), while hake tissues, namely the tail, contained more palmitic acid (16:0), palmitoleic acid (16:1 n -7), docosahexaenoic acid (22:6 n -3), and omega-3-rich polyunsaturated fatty acids in general. Principal component analysis positioned the parasitized tissue of the hake belly flaps as an intermediate group, suggesting possible local metabolic interference. Lipidomics identified a total of 477 different lipid species and highlighted the existence of the following differences: saturated triacylglycerols and ether-linked phosphatidylcholines, phosphatidylethanolamines, and sphingomyelins species were more prevalent in Anisakis larvae, while some highly unsaturated phosphatidylcholines and monounsaturated triglycerydes were more abundant in hake tissues; specific sphingomyelins and ether lipids were exclusive of the fish tissue adjacent to the parasites (belly flaps) and may represent potential biomarkers of Anisakis spp. infection. Together, these results suggest that Anisakis larvae may influence/modulate local lipid metabolism, with parasite influence being more pronounced in fish tissue closer to the infection site with regard to distant unparatized tissue. Ultimately, this work supports the use of lipid profiling for better understanding host-parasite interactions in marine fish and unveils applications for parasite infection detection. • Distinct lipid profiles found between Anisakis larvae and hake host tissues. • Larvae richer in saturated TAGs and ether-linked phospholipids. • Hake tissues richer in omega-3 and highly unsaturated phospholipids. • Local metabolic interference suggested in parasitized belly tissues. • Lipid profiling reveals biomarkers of Anisakis infection in European hake.