A Lipidomics Study of Malaysian Sea Urchin Gonads: Species Influence on Lipid Composition

Sea urchin is always touted as a promising alternative marine source for dietary essential fatty acids. Often overlooked is that their lipid composition can vary significantly depending on the species and their feeding preferences. Understanding that every sea urchin species, together with their feeding behaviour, may offer unique nutritional benefits helps to optimise the utilisation of sea urchin as a reliable source of marine fatty acids. This study aimed to measure the gonad index, lipid content, and composition in the gonads of two sea urchin species live in coral reef and seagrass habitats in Malaysia. The gonad’s lipid was extracted using the Folch extraction method, followed by the esterification process before being analysed using GC-FID. The gonad index was calculated based on the percentage of gonads relative weight as a proportion of total body weight. The gonad indexes of both Diadema setosum (Leske, 1778) 6.74 ± 2.49% and Salmacis sphaeroides (Linnaeus, 1758) 6.68 ± 2.30% were found to be statistically indifferent (p>0.05). Both D. setosum and S. sphaeroides had a negative allometric growth (b < 3). The major saturated fatty acids found in both species were C16:0 and C14:0 while the major unsaturated fatty acids (UFAs) were C16:1 and C18:3. In the gonads of both species, n-6 UFAs were the most abundant, followed by n-9 and n-3 UFAs. In D. setosum, n-6 UFAs comprised 74.77%, n-9 UFAs 21.76%, and n-3 UFAs 3.47%. In contrast, S. sphaeroides had 52.13% n-6, 22.48% n-9, and a notably higher proportion of n-3 UFAs at 25.39%. S. sphaeroides lacked two types of fatty acids that were present in D. setosum, specifically C17:1 (heptadecenoic acid) and C20:1n-9 (gondoic acid). This study reveals the different composition of fatty acids in the gonads of D. setosum collected from coral reef areas and S. sphaeroides collected from seagrass areas of Malaysian water. Recognising these differences is crucial when evaluating sea urchins as a promising alternative source of healthy dietary fats.