LIPID CLASSES AND FATTY-ACID COMPOSITION OF ROTIFERS (BRACHIONUS-PLICATILIS) FED 2 ALGAL DIETS

Rotifers (Brachionus plicatilis), maintained on baker's yeast, were fe d for 24h upon two algal diets, Isochyrsis galbana (diet A) and Isochr ysis galbana + Nannochloropsis gaditana (diet B). (These algal diets w ere selected for their potential use as essential fatty acid (EFA) boo sters, taking into account the requirements of fish larvae). The effec t of these algal diets on total lipid content, lipid classes and fatty acid composition was studied. The total lipid content increased after feeding upon both diets but no significant differences were found bet ween the two types. Neutral lipid and polar lipid contents increased s ind a positive correlation was observed between the neutral lipids con tent of rotifers and that of the food supplied. However, the content o f polar lipids in rotifers did not depend upon that of the diet. The i ncrease in neutral lipid content was found to be higher in rotifers fe d upon diet B, compared to diet A which increased the phospholipid con tent. Non-enriched rotifers contained only small amounts of polyenoic fatty acids, i.e. 18:3n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3, the contents of which increased significantly by feeding both diets. The E FA composition (20:4n-6, 20:5n-3 and 22:6n-3) of neutral lipids and ph opholipids in rotifers reflected the EFA composition of each diet. Die t B-fed rotifers had the highest content in 20:4n-6 and 20:5n-3, where as rotifers fed diet A and the highest 22:6n-3 content. The mixed diet , I. galbana + N. gaditana enhanced substantially the composition of l ipid classes i.e. neutral lipids and of n-3 PUFA of rotifers in compar ison with Isochrysis or yeast diets.