Metabolic aspects of free amino acids in developing marine fish eggs and larvae

Abstract

Abstract Investigations during the last decade have shown that free amino acids (FAA) abound in marine pelagic fish eggs. The concentration in the egg (about 150 mM) is well above what is typically found in adult teleostean tissues. FAA in fish eggs were initially studied in order to evaluate their role as osmolytes. More recently, however, FAA have been implicated as a fuel in the energy metabolism of developing marine fish eggs and larvae. Further aggregation of data verifies that pelagic eggs of marine teleosts generally have a high content of FAA. The large pool of FAA is almost exclusively contained within the yolk‐sac compartment. The relative composition of the FAA pool shows little interspecific variation. The FAA pool is depleted during development and reaches low levels at first feeding. The observed decline in the FAA content during development is not due to a loss of FAA to the ambient water, but rather results from endogenous metabolic turnover. FAA seem to be utilized to varying extents for body protein synthesis, but are more often used as substrates in energy metabolism.