Biochemical phases in embryonic red sea bream development

Changes in chemical constituents and enzyme activities were assayed in red sea bream Pagrus major through embryonic development from eggs immediately after fertilization to larvae just before feeding. No significant changes were found in protein, total nitrogen, and phospholipid contents with proceeding development stages. Although free amino acid (FAA) and triacylglycerol (TAG) contents continuously fell, DNA and RNA contents reversely increased through the development. Ammonia, free glucose, and glycogen contents were maintained at markedly low levels. Aspartate aminotransferase, alanine aminotransferase, creatine kinase, and alkaline phosphatase activities showed a similar change through the development, decreasing or remaining constant at low levels up to the stage of Kupffer's vesicle appearance and increasing steeply thereafter. These results suggest that endogenous TAG and FAA are preferentially expended as energy reserves under the embryonic development of red sea bream. The rapid increases of the enzyme activities after the stage of Kupffer's vesicle appearance might correspond to their organ differentiation and function.