INCORPORATION OF MICROALGAE STEROLS BY SCALLOP PECTEN-MAXIMUS (L.) LARVAE

Changes in sterol composition of Pecten maximus larvae during the larv al development stage with standard algal mixtures and unialgal diets w ere analysed. The sterol composition of four microalgae currently used in mollusc hatchery were also examined. Under standard algal conditio ns, the larvae quickly use the steryl ester from larvae reserves durin g the endotrophic and the mixotrophe phases. The preferential incorpor ation of Pavlova lutheri and T-lsochysis sterols, rather than Skeleton ema costatum sterols, during the larval development stage would indica te that S. costatum cells were poorly ingested and digested by larvae. Among the ingested sterols, cholesterol and stigmasterol were prefere ntially incorporated by the larvae. Conversely, the larvae appeared ab le to Limit the incorporation of methylpavlovol, ethylpavlovol, and 4 alpha-methylporiferasterol. In the unialgal experiment, the best growt hs were obtained with the diet richest in cholesterol (Chaetoceros cal citrans) and the best compromise of good growth and settlement rate wa s observed with the diet richest in C24 ethyl sterol. The selective in corporation of the cholesterol was confirmed by the larval rearing wit h C. calcitrans. The strong sterol dietary imprint in larvae corrobora ted the absence of an important capacity in P. maximus larvae to conve rt or biosynthesise sterol. (C) 1998 Elsevier Science Inc.