Larval growth and settlement of the European oyster (Ostrea edulis) as a function of food duality measured as fatty acid composition

Larval growth rate and settlement of the European flat oyster Ostrea edulis were experimentally studied as a function of the composition of dietary fa tty acids. Diets differing in fatty acid composition were composed by mixtu res of the microalgae Isochrysis galbana, Pavlova lutheri and Chaetoceros c alcitrans. Fatty acid content in the tissue of the feeding larvae, analyzed by gas chromatography and mass spectrometry, reflected the composition in the diet. Larval growth rate was significantly correlated to the three omeg a-3 polyunsaturated fatty acids (PUFA) C18:3, C18:4 and C22:6, with minor d ifferences for neutral and polar lipids. No relation between growth rate an d the omega-3 PUFA C20:5 was detected, a PUFA often implied as essential fo r bivalves. It is suggested that naturally occurring variability in fatty a cid composition may constrain larval growth. In settlement experiments in b oth still water and flume flow little substrate selectivity was found for s ome contrasting substrates. It is concluded that differences in dietary fat ty acids may explain as much of settlement success as the variability of su bstrates.