MEPS 409:65-75 (2010)  -  DOI: https://doi.org/10.3354/meps08622

ABSTRACT: The lipid class and fatty acid (FA) composition for 93 species of reef-building and soft corals from the South China Sea (Vietnam) were analyzed and statistically compared to study systematic patterns of the distribution of lipids in corals and the influence of zooxanthellae on the lipids of symbiont-host association. The lipid and FA compositions of hexacorals and octocorals significantly correlated with their taxonomic position, but the lipid features of species within each of these systematic groups mainly depended on the presence of zooxanthellae. The hexacorals had lower content of polar lipids (PL), sterols (ST), and monoalkyldiacylglycerols (MADAG), but higher content of triacylglycerols (TG) and wax esters (WE) than the octocorals. On average, zooxanthellate species contained less structural lipids (PL+ST), but more MADAG when compared to azooxanthellate species. Tetracosapolyenoic acids 24:5n-6 and 24:6n-3 were chemotaxonomic markers for octocorals, whereas 22:5n-6 was a marker for Milleporidae. A strong correlation was apparent between zooxanthellate coral family and/or genus and the content of the unsaturated FA; 12 FAs were significant for the separation of azooxanthellate and zooxanthellate specimens. The latter had lower concentrations of 7-Me-16:1n-10, 18:1n-7, and six C_20–24 polyunsaturated FA, but higher concentrations of 16:0, 16:2n-7, 18:3n-6, and 18:4n-3. The presence of >2% of 18:3n-6 and 18:4n-3 of total FA is characteristic of zooxanthellate corals. An inverse correlation was established between the content of 18:3n-6 and 16:2n-7 in zooxanthellate soft corals. The present study highlights the importance of zooxanthellae in coral lipid metabolism, especially when compared with symbiont-host exchanges in reef-building and soft corals.

KEY WORDS: Lipid classes · Fatty acids · Hexacorallia · Octocorallia · Zooxanthellae · Biomarkers · Chemotaxonomy · Coral reef ecology