Research On Biochemical And Metabolic Changes Of Embryonic And Larval Development Of Bastard Halibut(Paralichthys Olivaceus)and Large Yellow Croaker(Pseudosciaena Crocea)

Biochemical and morphological parameters of laboratory-reared developing eggs and larvae of bastard halibut (Paralichthys olivace us) and large yellow croaker (Pseudosciaena crocea) were measured for oxygen uptake ,ammonia excretion, contents of free amino acids(FAA), fatty acids(FA) and accumulated ammonium , and volume of yolk-sac and oil globule (FA are only measured for bastard halibut).They were acclimated to the filtered sea water at 17.4 0.3 for bastard halibut and 23.2 for large yellow croaker, respectively, but salinity kept at 31 The main results were summarized as following: 1. Both bastard halibut and large yellow croaker had an obvious ammonium cumulation during their egg developmental stage, one of which were excreted to the environment and the others were cumulated in the body. When hatching, the cumulated ammonia were released into the water body with the outburst of the egg membrane, resulted in a peak value in NH3 concentration excretion. 2. Soon after fertilization both bastard halibut and large yellow croaker consistently displayed a prodigious total free amino acids pool in their germ cell. Combined with the change of yolk volume, it could be concluded that these free amino acids mostly come from the yolk. Free amino acids was an important energy substrate during the early development, constituted 35% the energy metabolism of bastard halibut and 28% of large yellow croaker, respectively. Furthermore, during the egg developmental stage, free amino acids were also used to compound protein displayed an obvious increment. 3. Together with the fracture of the egg membrane and the loss of the egg circumambient fluid, both bastard halibut and large yellow croaker were obviously decreased in dry weight and protein. 4. During the early stage of the yolk-sac larval stage, both slightly increased in protein yielding some of FAA was transferred into protein as an energy substrate. 5. DHA (22:6n-3) and EPA (20:5n-3) were dominated in high-unsaturated fatty acids (HUFA) in the germ of bastard halibut, accounting for 86% of HUFA. Compared the volume of the oil globule with the total fat content, it has been found that fatty acids mostly lied in the oil globule. After hatching, it could be proved that fatty acids in the oil globule were the most important energy substrate. 6. Free amino acids (FAA) acted as the most important energy sources during the egg developmental stage, and after hatching fatty acids (FA) of neutral lipids in the oil globule was used as the main energy substrate. Before uncorking, protein began to supply energy base to some extent. 7. From post-fertilization (PF) to first feeding, bastard halibut conserved 59.7% of yolk enthalpy for growth, 43.6% was dissipation due to metabolism and only 0.3% was lost due to excretion(59.7+43 .6+0.3 103.6). 8. Bastard halibut is warm-temperate demermal fish, its egg is smaller, the developmental temperature is lower, its developmental speed is slower; large yellow croaker is warm-water fish, its egg is larger, the developmental temperature is higher, its developmental speed is faster, so they have different energy strategy. In Bastard halibut free amino acids (FAA) was accounted for 35% of the energy metabolism, but in large yellow croaker, free amino acids (FAA) only 28%. 9. Based on our results and accumulated information, it is concluded that the most important energy sources has species-specialty in fish developmental biology and its...