Study of Total Lipidome of the Sinularia siaesensis Soft Coral

The rapid development of lipidomics of human and higher animals stimulated the study of the lipidome of certain groups of marine organisms. Soft corals are an integral part of the tropical and cold-water ecosystems of the World Ocean, but there is almost no data on the lipidome of these animals. The total lipidome of a tropical soft coral Sinularia siaesensis (Cnidaria: Anthozoa: Octocorallia: Alcionacea) containing intracellular symbiotic microalgae (zooxanthellae) was studied by gas and liquid chromatography-mass spectrometry. The structure and content of 144 molecular species of the main classes of acyl lipids of this alcyonaria were determined, including waxes, triglycerides (TG), monoalkyldiacylglycerides (MADAG), ethanolamine, choline, serine, and inositol glycerophospholipids (PE, PC, PS, and PI), ceramide aminoethylphosphonate (CAEP), sulfoquinovosyldiacylglyceride (SQDG), and mono- and digalactosyldiacylglycerides (MGDG and DGDG). The main components of S. siaesensis lipids were waxes 16:0/16:0, 16:0/18:0, and 18:0/16:0; TG 16:0/16:0/16:0 and 16:2/16:0/16:0; MADAG 18:0e/16:0/16:0, 16:0e/16:0/18:0, and 16:0e/16:0/16:0; and PS 18:0e/24:5, lyso-PC 18:0e, PE 18:1e/20:4, PC 18:0e/20:4, CAEP 18:2b/16:0, SQDG 14:0/16:0, and PI 18:0/24:5. The dominance of saturated waxes in reserve lipids is a species-specific feature of tropical alcyonarians. Waxes are synthesized in the host organism, and zooxanthellae can increase the proportion of saturated waxes by transferring saturated fatty acids (FA). The residues of polyunsaturated FA (PUFA) are found in the molecules of TG and MADAG, mainly in the sn-1 and sn-2 positions, respectively. Detection of MADAG with residues of marker FA of zooxanthellae (18:0e/18:3/16:0, 18:0e/18:4/16:0, and 16:0e/18:3/16:0) confirms the transfer of PUFA from the symbionts to the host. Tetracosapolyenoic FA, which is a chemotaxonomic markers of octocorals, are concentrated in molecular species of PS and PI. Most molecular species of PE, PC, and PS are in alkylacyl form, while for PI molecules, a diacyl form is characteristic. A significant proportion of MGDG, DGDG, and SQDG points to the importance of zooxanthellae in the formation of the lipid profile of symbiotic soft corals. Determination of the profile of lipid molecular species requires the development of a lipidomic approach in the study of biochemistry and ecology of corals and other cnidarians.