Incorporation of dietary sterols by the sea scallop Placopecten magellanicus (Gmelin) fed on microalgae

Abstract

The anatomical distributions of sterols and the incorporation of dietary phytosterols into different organs were studied in two populations of sea scallops, Placopecten magellanicus Gmelin, collected in 1989 from Georges Bank (Nova Scotia) and St. Pierre Bank (Newfoundland), respectively. In contrast to the well-established organ-specific lipid classes and fatty-acid compositions usually found in marine animals, the major organs of wild sea scallops (adductor muscle, digestive gland, gonads, gills and mantle) had the same sterol compositions. In order to know if anisomyarian bivalves require a uniform anatomical distribution of sterols, wild scallops were subjected to a microalgal diet containing high concentrations of brassicasterol, β-sitosterol and cholesterol. The sterol composition of the scallop adductor muscle was not changed by 6 wk of feeding on the experimental diet. In contrast, the proportions of brassicasterol, β-sitosterol and cholesterol in the digestive gland, and of brassicasterol and cholesterol in the male gonad, increased significantly (p<0.05). These results showed that the typical even anatomical distribution of sterols of bivalves can be disrupted by a drastic change in diet and is therefore not subject to strict internal regulation. Furthermore, the P. magellanicus results indicate that, although sea scallops may be capable of sterol biosynthesis, the incorporation of unmodified dietary phytosterols plays an influential role in establishing their sterol composition.