抄録
Feeding experiments were conducted to examine the effects of algal diets, Chaetoceros gracilis or Chlorella saccharophila, on the sterol and fatty acid compositions of the pearl oyster Pinctada fucata. The pearl oysters were starved or fed with the algal diets for 30 days. Chaetoceros and Chlorella supported the growth of the pearl oyster during the period of 1 to 10 days to some extent, the former having a superior food quality to the latter. However, the pearl oysters seemed not toconsume algal diets substantially during the period of 10 to 30 days. Compared with the specimens at the start of the feeding trials, the pearl oysters receiving either Chaetoceros or Chlorella for 10 days contained low proportion of cholesterol and slightly high proportions of 24-ethyl-cholesterol and isofucosterol. However, the starved pearl oysters showed similarities to those receiving the algal diets in sterol compositions. These results indicate that the sterol composition of this bivalve is scarcely affected by the algal diets, suggesting that the sterol biosynthesis and turnover of dietary sterols proceed at a very slow rate. The 10-day feeding of Chaetoceros rich in 16:1 resulted in an increase in proportion of 16:1 in the pearl oysters. Chlorella contained large quantities of ω3-highly unsaturated farty acids (HUFA) such as 20:5ω3, The proportions of ω3-HUFA of the pearl oysters receiving Chlorella for 10 and 30 days were slightly higher than those of starved and Chaetoceros-fed groups but not so high as those of the specimens at the start of the feeding trials.
