UTILIZATION OF FREE AMINO-ACIDS RELATED TO ENERGY-METABOLISM OF DEVELOPING EGGS AND LARVAE OF LEMON SOLE MICROSTOMUS-KITT REARED IN THE LABORATORY

Eggs and larvae of lemon sole Microstomus kitt Walbaum were reared in the laboratory (7.2-degrees-C, 34 parts per thousand salinity, no supply of external food) and sampled regularly for measurement of oxygen uptake, ammonia excretion, contents of free amino acids (FAA), protein, total ammonia, and yolksac volumes. Newly spawned eggs contained about 135 nmol egg-1 FAA, 27 nmol egg-1 total ammonia and 32 mug egg-1 protein. Serine, leucine, alanine, lysine, valine and glutamic acid were most abundant in the egg FAA pool. No significant changes occurred in the pool size prior to epiboly, but about 75 nmol ind.-1 (56 %) disappeared prior to hatching and about 15 nmol remained at final yolk absorption (Days 22 to 23). The yolk volume was linearly correlated to content of FAA. The combined data suggest that, after epiboly, increasing amounts of FAA enter the embryo from the yolk and are utilized both for energy and protein synthesis. FAA account for 60 % of the aerobic energy dissipation 9 d after fertilization, increasing to about 100 % at the time of hatching. Amino acids from protein seem to be recruited f or energy dissipation after hatching. At the presumed time for first feeding lemon sole larvae derive about 20 % of aerobic energy dissipation from FAA, and another 35 % from protein amino acids.