Fatty acid and lipid composition of fish egg and larvae

Maternal nutrition affect the egg lipid composition and freshwater and marine fish species. In some of these species essential fatty acid (EFA) deficiency influences their egg quality. The total lipid content of marine and freshwater species is highly variable among the species. Lipid content in fertilized and unfertilized are variable and generally dependent in their water content. Overripe eggs contain more lipids than ripe eggs. In plaice eggs the correlation between total lipids and egg size was positive correlation (r²=0.84) when total lipids were expressed in absolute terms (μg/egg) but negative (r²=-0.45) when expressed in relative terms (%). In some species total lipid content was expressed as egg quality indicator. Although the total lipid content in plaice eggs did give not any egg quality indication, the EFA deficiency index did. Lipid class composition was also variable among the species. Eicosapentanoic (EPA, 20:5 n-3) and docosahexanoic (DHA, 22:6 n-3) are rich in fish egg lipids, especially in the phospholipid fraction. The lipid metabolism during early embryonic development until to the stage prior to first feeding is also species dependent. However the utilization of DHA during early development and the conservation during starvation may be a common feature in several marine and freshwater species. During larval starvation triacylglycerols were preferently consumed whereas the phosholipids tended to be conserved. EPA was mainly catabolized and in addition to DHA also AA was conserved during starvation in several species. Conservation of DHA during the larvae starvation might be associated with the increasing content of phosphatidylethanolamine (PE) which may be related to the developing and conservation of neural tissues.