Influence of diet on fatty acids of three subtropical fish, subfamily Caesioninae (Caesio diagramma and C-tile) and family Siganidae (Siganus canaliculatus)

The total lipid and fatty acid compositions of tissues and the stomach cont ents of three subtropical marine fish species, subfamily Caesioninae, Caesi o diagramma and C. tile, and family Siganidae Siganus canaliculatus, were i nvestigated to clarify the differences between these species. Triacylglycer ols (TAG) were the dominant depot lipids of the three species, whereas wax esters were found as a minor component. In particular, muscle lipids were f ound to contain mainly glycerol derivatives such as TAG and phospholipids. The major fatty acids identified in the three species were 16:0, 18:0, 18:1 n-9, and 22:6n-3 (docosahexaenoic acid, DHA). In addition, noticeable level s of 16:1n-7, 18:1n-7, 20:4n-6 (arachidonic acid, AA), and 20:5n-3 (eicosap entaenoic acid) were found. DHA was the most abundant polyunsaturated fatty acid (PUFA) in the muscle and viscera lipids of the three species. The hig h DHA levels in the lipids of all the organs were found to be higher than t hose of the lipid extracted from the stomach contents of the three fishes. In addition the specimens of S. canaliculatus contained significantly highe r levels of AA in its tissues than did the other two species. A high AA con tent is unusual since such high levels of n-6 PUFA are rarely found in high er marine organisms. These levels may be due to its characteristic feeding pattern, because S. canaliculatus prefer and mainly feed on seaweed, which often contains high amounts of n-6 PUFA, such as linoleic acid (18:2n-6) an d AA.