Lipid Composition of Tropical and Subtropical Copepod Species of the Genus \u3cem\u3eRhincalanus\u3c/em\u3e (Copepoda: Eucalanidae): A Novel Fatty Acid and Alcohol Signature

Rhincalanus nasutus, R. rostrifrons, and R. cornutus are primarily found in subtropical and tropical waters and accumulate large lipid stores, an uncommon feature in low-latitude copepods. While R. nasutus fatty acid and alcohol profiles have been examined previously, little is known about lipids in R. rostrifrons or R. cornutus. Lipid profiles for wax ester, triacylglycerol, phospholipid, free fatty acid, sterol, and free fatty alcohol fractions were determined for these 3 species collected from the eastern tropical north Pacific, Gulf of California, and Gulf of Mexico. Storage lipids, primarily wax esters, were the dominant component (\u3e88%) of total lipid in all 3 Rhincalanus species. R. nasutus, however, had distinctly different storage lipid fatty acid and alcohol profiles, with primarily 16:1(n-7)/18:1(n-9) fatty acids and 14:0/16:0 fatty alcohols, while R. cornutus and R. rostrifrons accumulated 14:0/16:0 fatty acids and 16:1/18:1 fatty alcohols. Species differences also were observed in sterol profiles, with R. rostrifrons having a cholesterol content of 75 to 76% versus 85 to 90% in R. nasutus and R. cornutus. The remainder of the sterol fraction was largely composed of 22-dehydrocholesterol in all species. In all 3 species, phospholipid fractions were dominated by 22:6(n-3), 16:0, 18:0, 20:5(n-3), and 18:1(n-9) fatty acids. The results of the present study suggest that genetic predisposition significantly governs lipid profiles, particularly storage lipids, within this genus. The storage lipid profiles observed in R. cornutus and R. rostrifrons were unique from their congeners and have not been reported previously for other copepod species