Effects of 1,2-di-20:5–phosphatidylcholine (PC) and 1,2-di-22:6–PC on growth and stress tolerance of Japanese flounder ( Paralichthys olivaceus) larvae

Abstract

Phospholipids, such as soybean phosphatidylcholine (PC), in the diets have been shown to be indispensable for sustaining growth of certain larval fish. It has also been demonstrated that n−3 highly unsaturated fatty acids (HUFA), such as eicosapentaenoic acid (EPA, 20:5 n−3) and docosahexaenoic acid (DHA, 22:6 n−3), are essential for marine fish. These two nutrients, phospholipids and n−3 HUFA, are believed to be indispensable for normal growth and survival of marine fish larvae. The present research was conducted to determine the effect of 1,2-di-20:5–PC, 1,2-di-22:6–PC and 22:6–TG on growth and stress tolerance of larval Japanese flounder. Japanese flounder (20 days after hatching, mean total length of 9.6±1.0 mm) were fed microparticulate diets containing 1% phospholipids (purity 99%) for 30 days at 17.2–19.5°C. After the feeding trials, their tolerance in stress factors such as changes in water temperature and salinity, and exposure to low dissolved oxygen were determined. Results indicated that dietary 1,2-di-22:6–PC was more efficient than 1,2-di-20:5–PC and 22:6–TG for stress tolerance of Japanese flounder larvae towards increased water temperature and reduced DO.