REVIEW ON THE DIETARY-EFFECTS OF PHOSPHOLIPIDS IN FISH AND CRUSTACEANLARVICULTURE

A beneficial effect of dietary phospholipid (PL) supplementation in pu rified diets in terms of survival, growth, resistance to stress tests, and occurrence of deformities has been demonstrated in larval and juv enile stages of various species of fish and crustaceans. The exact det ermination of PL requirements in larvae is complicated due to the diff iculty to bio-encapsulate PL in live prey, Furthermore, the great vari ety in purity and composition of the PL sources, and the experimental conditions (such as diet formulation and extent of co/prefeeding with live food) makes it difficult to compare requirements determined with artificial diets. Larval stages are extremely sensitive to a dietary P L deficiency and require higher levels of dietary PL than juveniles, F or most of the fish and crustacean species examined, the estimated PL requirement of larvae are in the range of 1-3% phosphatidylcholine + p hosphatidylinositol (PC + PI) of diet dry weight. The absence of a PLr equirement in the freshwater prawn Macrobrachium rosenbergii exemplifi es the important species differences. The few studies evaluating singl e PL demonstrate that PC and PT are the most efficient in most species . The presence of an unsaturated fatty acid in sn - 2 position of the PL molecule seems to be essential for the functionality of FL. Some st udies in crustaceans reported a relation between PL requirements and t he protein source in the diet. Various hypotheses have been formulated to explain the effect of FL. The PL effect is not related to the prov ision of choline, inositol or essential fatty acids (EFA). However, PL may be superior to neutral lipids for larvae as a source of EFA and e nergy due to their better digestibility. PL may improve the performanc e of the diet by improving the water stability of food particles, or b y their action as antioxidant or feed attractant. The effect of dietar y PL appears not to be explained by their emulsifying ability. However , there are proofs that dietary PL interfere with lipid transport, esp ecially cholesterol transport in crustaceans, and with retention of fa tty acids provided by dietary triacylglycerol. Although the origin of the requirement is still unclear, dietary PL supplementation has poten tial importance for the formulation of practical larval diets. (C) 199 7 Elsevier Science B.V.