The amino acid profiles of estuary perch, Macquaria colonorum, during early development at different salinities

Estuary perch, Macquaria colonorum, is a truly estuarine species and spawns naturally in salt-wedged estuaries in salinities of 20-30. In this study, results on the changes in the total amino acids (TAA) (protein bound + free ) and free amino acid (FAA) pools of developing eggs and newly hatched larv ae until yolk-sac resorption were evaluated at four incubation salinities ( 15, 20, 25 and 30). The TAA in 1-h post-fertilised eggs ranged from 207.4 /- 2.2 to 231 +/- 10 nmol.egg(-1), at salinities of 20 and 15, respectively . The TAA content decreased significantly (P < 0.05) as development progres sed. The FAA in eggs of estuary perch ranged from 35.5 +/- 0.5 to 41.0 +/- 0.9 nmol.egg(-1) at salinities of 30 and 15, respectively, and accounted fo r 15.7-28.0 % of the TAA. In newly hatched larvae the TEAA accounted for be tween 42.0 and 43.2 % of the TAA. The FAA decreased significantly with deve lopment, it being reduced in yolk-sac resorbed larvae to 19, 16.2, 22.8 and 28.7 % of that of the original amount in fertilised eggs in salinities of 15, 20, 25 and 30, respectively. The FEAA in the FAA poor also decreased si gnificantly with development, to approximately 33.7-35.3 % in yolk sac reso rbed larvae from that in fertilised eggs. The data suggest that estuary per ch uses its FAA for energy dissipation during early ontogeny rather than fo r body protein synthesis. Overall, the amino acid profiles of estuary perch were close to that of pelagic eggs of marine fish, and there were no major influences of salinity on the amino acid profiles as development progresse d. (C) 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medica les Elsevier SAS.