Incorporation of microalgae sterols by scallop Pecten maximus (L.) larvae.

Changes in sterol composition of Pecten maximus larvae during the larval development stage with standard algal mixtures and unialgal diets were analysed. The sterol composition of four microalgae currently used in mollusc hatchery were also examined. Under standard algal conditions, the larvae quickly use the steryl ester from larvae reserves during the endotrophic and the mixotrophe phases. The preferential incorporation of Pavlova lutheri and T-Isochrysis sterols, rather than Skeletonema costatum sterols, during the larval development stage would indicate that S. costatum cells were poorly ingested and digested by larvae. Among the ingested sterols, cholesterol and stigmasterol were preferentially incorporated by the larvae. Conversely, the larvae appeared able to limit the incorporation of methylpavlovol, ethylpavlovol, and 4alpha-methylporiferasterol. In the unialgal experiment, the best growths were obtained with the diet richest in cholesterol (Chaetoceros calcitrans) and the best compromise of good growth and settlement rate was observed with the diet richest in C24 ethyl sterol. The selective incorporation of the cholesterol was confirmed by the larval rearing with C. calcitrans. The strong sterol dietary imprint in larvae corroborated the absence of an important capacity in P. maximus larvae to convert or biosynthesise sterol.