Incorporation of different fatty acids, supplied as emulsions or liposomes, in the polar and neutral lipids of Crassostrea gigas spat

Ž . Ž . Pacific oysters spat Crassostrea gigas were fed an algal diet Tetraselmis suecica whether or not supplemented with emulsions or liposomes rich in 18:1ny9, 18:2ny6 and 22:6ny3. The preferential accumulation and partitioning of the latter fatty acids between the polar and neutral lipids of C. gigas spat were followed. Additionally, the efficiency of emulsions and liposomes as fatty acid carriers for C. gigas spat were compared. The incorporation of dietary fatty acids was Ž . found to vary substantially according to the fatty acid carrier emulsions vs. liposomes , the Ž . Ž particular fatty acid 18:1ny9, 18:2ny6 or 22:6ny3 , and the lipid fraction neutral vs. polar . Ž . Ž lipids . A comparison of the percentage % of the total fatty acids and absolute concentration mg y1 . g dry weight of 18:1ny9, 18:2ny6 and 22:6ny3 in the total lipids of C. gigas fed solely T. suecica or lipid-supplemented diets, suggest the following order of preferential accumulation: 22:6ny3)18:1ny9)18:2ny6. Unlike 22:6ny3 which was accumulated in both the neutral and polar lipid fraction of C. gigas, 18:2ny6 and 18:1ny9 were mainly deposited in the neutral lipids. High dietary supplies of ny6 andror ny3 PUFA seriously altered the ny3rny6 PUFA ratio in the neutral as well as polar lipids of spat. The fatty acid profile of emulsion-fed spat indicated a rather limited ability to elongate 18:2ny6 to 20:2ny6 whereas no clear evidence for desaturation to 20:4ny6 was observed. Irrespective of the diet, nonmethylene-interrupted-dienes Ž . and plasmalogens detected as dimethylacetals were abundant and located nearly exclusively in Ž . the polar lipids. The ash free dry weight AFDW of emulsion-fed spat was significantly higher than the AFDW of liposomes-fed spat which was in turn significantly higher than the AFDW of oysters fed solely algae. The growth and fatty acid composition of liposomes-fed oysters illustrated their inferior efficiency as compared with emulsions to supplement algal diets with fatty ) Corresponding author. Tel.: q32-9-2643754; fax: q32-9-2644193. Ž . E-mail address: [email protected] M. Caers . 0044-8486r00r$ see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 99 00364-6 ( ) M. Caers et al.rAquaculture 186 2000 157–171 158 acids. This could have been related to the small size of the liposomes vs. an emulsion. q 2000 Elsevier Science B.V. All rights reserved.