Impact of starvation and of feeding algal and artificial diets on the lipid content and composition of juvenile oysters (Crassostrea gigas) and clams(Tapes philippinarum)

The present study evaluated the effect of starvation and of feeding various algal and lipid-supplemented diets on the lipid content and lipid class di stribution in the polar and neutral lipids of early juvenile oysters (Crass ostrea gigas) and clams (Tapes philippinarum L.). T. philippinarum was star ved, fed a mixed algal diet [Tetraselmis suecica and Isochrysis galbana (cl one T-Iso)] or solely T. suecica at three different feeding rations, either supplemented or not supplemented with lipid emulsions. C. gigas was fed T. suecica with and without the supplementation of lipid emulsions or liposom es. When T. philippinarum and C. gigas were fed solely T. suecica, no quali tative and only minor quantitative differences were observed between the li pid class profile of both species. The major neutral lipids were triglyceri des (TAG) and free sterols plus diglycerides (FS + DAG), whereas the polar lipids were dominated by phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol plus ceramideaminoethanol phosphonate (PI CAEP). An increase of the algal feeding ration resulted in an increase of t he lipid content of spat which was associated with a significant augmentati on of the TAG level (as percentage of the total lipids and as percentage of the neutral lipids). Lipid supplementation evoked a similar though more pr onounced effect. Starvation resulted in a significant decline of the lipid content and a complete depletion of the TAG reserve. Contrary to the neutra l lipids (NL), the relative proportion (percentage of total polar lipids, F L) of the individual PL classes was hardly affected by the diet. The import ance of lipid and TAG reserves in early juveniles is discussed.