In the three stages of development of the rainbow trout, the lipid composition of the oil globule and of the lipoprotein of the yolk globule was investigated.
1) A variation of the lipid class composition in the oil globule was not observed in the course of the development, while the fatty acid composition was slightly altered.
2) In a later developmental stage, lysolecithin and NEFA appeared with the degradation of lecithin bound to the lipoprotein.
3) On analyses of the fatty acid, it was shown that polyunsaturated acid spreads in triglyceride more than in phospholipid. In NEFA, palmitic, palmitoleic and oleic acids were rich in the latter developmental stage, while docosahexaenoic and eicosapentaenoic acids were poor. A selective consumption of the polyunsaturated fatty acid was also observed.
4) A certain enzymatic action seemed to affect a transesterification between triglyceride and phospholipid within lipoprotein.