Biochemical changes during embryogenesis of the Pacific halibut, Hippoglossus stenolepis (Schmidt)

Abstract

Abstract Eggs of Pacific halibut held in a conical incubator at 6deg;C hatched 422 h post-fertilization. Levels of moisture, monosaccharides and total carbohydrates in the embryos demonstrated significant linear increases during this period of development. Significant linear declines in levels of total lipid and ash occurred, but polysaccharide and protein contents were virtually unchanged. The ratio of RNA:DNA, signifying rate of protein synthesis, declined during embryogenesis from 9·74 in the egg to 4·49 in the larvae. The slight increase in relative proportions of the essential eicosapentaenoic and docosahexaenoic acids was offset by a decline in palmitic add and indicated catabolism of only the saturated acid as a source of energy. Energy derived from carbohydrate, protein and lipid in the eggs increased, remained constant and decreased, respectively, with embryonic development. Total accountable energy expended during embryogenesis, principally by lipid catabolism, was 88·11 J/g wet weight or a decline of 6·96% of the original energy in the fertilized egg. However, non-protein nitrogenous constituents may also have contributed considerably to the total energy expended during embryogenesis.