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

## TL;DR

This study compares the lipid profiles of two farmed seahorse species, revealing differences in fatty acid distribution that could aid in developing targeted nutritional supplements.

## Contribution

The study provides the first comprehensive lipidomic comparison of farmed Hippocampus abdominalis and H. erectus using untargeted lipidomics and enzymatic hydrolysis.

## Key findings

- Triglycerides were the dominant lipid class in both seahorse species.
- H. abdominalis had higher phospholipid levels and more unsaturated fatty acids in its triglyceride fraction.
- DHA was evenly distributed in H. abdominalis but concentrated at sn-1,3 in H. erectus.

## Abstract

Seahorses, such as commercially farmed Hippocampus abdominalis and H. erectus, possess notable nutritional properties including antioxidant and anti-tumor activities. Lipids are key bioactive components distinguishing marine organisms from terrestrial counterparts, yet the lipidomic profiles of cultured seahorses remain poorly characterized, limiting their targeted nutritional application. Here, we employed untargeted lipidomics combined with enzymatic hydrolysis to comprehensively compare the lipid profiles of these two species. Triglycerides (TG) were the dominant lipid class in both seahorses. H. abdominalis exhibited higher total phospholipids, as well as more unsaturated fatty acids in its TG fraction. Docosahexaenoic acid (DHA) was evenly distributed across sn-positions in H. abdominalis but concentrated at sn-1,3 in H. erectus, while EPA was localized at sn-1,3 in both. These findings support the health food industry in developing targeted nutritional supplements from sustainably farmed seahorses, and further tap into the health value of seahorses for human wellness.

Seahorses exhibit significant nutritional functions, including antioxidant and anti-tumor properties, with species like Hippocampus abdominalis and Hippocampus erectus 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 H. abdominalis with the currently farmed H. erectus. 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, H. abdominalis 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 sn-1,3 and sn-2 positions in H. abdominalis, but concentrated at the sn-1,3 positions in H. erectus, whereas EPA was primarily localized at sn-1,3 in both species. Furthermore, H. abdominalis contained higher DHA levels in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) (predominantly at the sn-1 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.