Biochemical compositions and digestive enzyme activities during the embryonic development of prawn, Macrobrachium rosenbergii

Abstract

Biochemical composition and digestive enzyme activities of eggs during embryonic development were studied in the freshwater prawn, Macrobrachium rosenbergii. Proteins, lipids and carbohydrates were the main components in the embryos of M. rosenbergii. The proteins in yolk were used mainly as the structural substance, whereas the lipids and carbohydrates were used mainly as the energy sources. Protein content generally increased while lipid and carbohydrate contents decreased during the embryonic development. Seventeen amino acids, including eight essential amino acids, were found in every stage of embryonic development. The ratio of the contents of each essential amino acid (EAA) to total essential amino acid (TAA) remained unchanged during the different stages of embryonic development. The proportional content of glutamic acid was the highest among all the amino acids, and leucine content was the highest among the EAAs. The predominant fatty acids, in terms of relative proportion, were C16:0, C18:1n-9, C18:2n-6, C18:0 and C16:1 in each embryonic development stage. The monounsaturates (MUFA) were the preferentially utilized components of the unsaturates (UFA). C18:1n-9c was mainly used as an energy source during embryonic development, whereas C18:3n-3 and ARA mainly acted as the structural substances in embryos. SFA acted as the main energy source during early stages, from fertilized egg to gastrula stage, and MUFA acted as the main energy source from egg nauplius to egg metanauplius stage. HUFA were used mainly as energy sources during late stages. Of the five digestive enzymes assayed, activities of pepsin, trypsin and amylase were relatively high. Activities of pepsin, trypsin, amylase and cellulase increased during both the early and later embryonic stages, but decreased during the middle stages. The activity of lipase decreased after the gastrula stage. The gastrula stage was a special stage of embryonic development where organ anlage came into being. Activities of pepsin, trypsin, amylase and cellulase reached the highest level during the zoea stage. Variations of biochemical compositions and digestive enzyme activities were closely related to events in morphogenesis during the embryonic development of M. rosenbergii.