To clarify the growth-promoting effects of phospholipids, the prawn, Penaeus Japonicus, was maintained on various test diets containing a 7% level of pollack liver oil (PLO) and a 1% level of one of the following lipids: total lipids, acetone-soluble lipids (or neutral lipids), acetoneinsoluble lipids (or polar lipids), lecithin fraction, cephalin fraction, sphingomyelin-glycolipids (1:1), fatty acids of lecithin isolated from the short-necked clam, Tapes philipprnarum, commercial

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... animal cephalin, egg lecithin, and soybean lecithin. The highest weight gain was attained on the diet containing 7% PLO and 1% Tapes lecithin fraction. However, the fatty acids of Tapes lecithin did not exert such a growth-promoting effect. Also, soybean lecithin and egg lecithin had no effect. Tapes cephalin and animal cephalin were effective for the improvement of weight gain to some extent, but the growth-promoting effect of the two types of cephalin was not so as high as that of Tapes lecithin. These results suggest that the growth-promoting effect of Tapes lecithin is probably due to certain effects of the molecular form of Tapes lecithin itself.