Lipid Profiles and Fatty Acid Positional Distribution in Two Farmed Seahorse Species by Untargeted Lipidomics and Enzymatic Hydrolysis

Abstract

Seahorses exhibit significant nutritional functions, including antioxidant and anti-tumor properties, with species like <i>Hippocampus abdominalis</i> and <i>Hippocampus erectus</i> now commercially farmed on a large scale. Notably, lipids are the key bioactive components distinguishing marine from terrestrial organisms. However, the lipidomic profiles of these cultured species are rarely reported, limiting their targeted nutritional application. Therefore, this study aimed to characterize and compare the lipid profiles of the newly introduced <i>H. abdominalis</i> with the currently farmed <i>H. erectus</i>. Methodologically, we employed an integrated approach utilizing untargeted lipidomics coupled with enzymatic hydrolysis to evaluate the lipid content, composition, molecular species, and fatty acid positional distribution of both species. The results revealed that triglyceride (TG) was the dominant lipid class in both seahorses. Notably, <i>H. abdominalis</i> exhibited higher overall phospholipid (PL) levels, along with elevated docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in its TG fraction. Positional distribution analysis demonstrated that DHA was evenly distributed at the <i>sn-1,3</i> and <i>sn-2</i> positions in <i>H. abdominalis</i>, but concentrated at the <i>sn-1,3</i> positions in <i>H. erectus</i>, whereas EPA was primarily localized at <i>sn-1,3</i> in both species. Furthermore, <i>H. abdominalis</i> contained higher DHA levels in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) (predominantly at the <i>sn-1</i> position) and possessed abundant alkoxy ether PLs. Ultimately, this work fills crucial research gaps regarding the lipid characteristics of commercially cultured seahorses, providing a fundamental basis for species identification, nutritional evaluation, and the future development of seahorse-derived functional lipids.