Biochemical And Energy Changes During The Early Embryonic Development Of The Pacific Oyster (Crassostrea Gigas)

The composition and content of carbohydrate, lipid and fatty acids, protein and amino acids, energy changes during the early embryonic development of the Pacific oyster (Crassostrea gigas) were measured and analyzed by biochemical methods. Embryos or larvae sampled at 0h, 6h, 12h, 24h post-fertilization (PF) were taken and measured. The results were as follows: (1) during the early embryonic development of the Pacific oyster (C. gigas), the dry weights were 25.14±0.44ng, 25.35±0.83ng, 25.26±1.00ng, 51.01±4.22ng at the four different times post-fertilization; the contents of carbohydrate(% dry weight)firstly increased from 5.25±0.50% at 0h post-fertilization to the highest 7.39±0.49% at 6h post-fertilization, and then decreased to 6.09±0.30% and 3.17±0.20% at 12h and 24h post-fertilization respectively. (2) the contents of lipid (% dry weight) decreased gradually with the embryonic development, yet the decrease was obvious only at 24h post-fertilization (p<0.05); there were 27 kinds of fatty acids detected in the zygotes (0h post-fertilization) and the contents of myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), EPA (20:5ω3)and DHA(22:6ω3)were relatively high during 0-24 h PF; the proportion of the saturated fatty acids and also the monounsaturated fatty acids to the total fatty acids increased with the embryonic development while the poly-unsaturated fatty acids decreased gradually. (3) the contents of protein (% dry weight) which were 55.94±0.82%, 55.12±0.47%, 54.86±0.37%, 26.02±3.68% during the four developmental periods respectively, had a downtrend; 16 kinds of amino acids were detected, including 7 kinds of the essential amino acids, 7 kinds of the non-essential amino acids and 2 kinds of the semi-essential amino acids; the total amino acids decreased with development. (4) energy consumed in each embryo from 0h PF to 24h PF was 63.50μj, derived 79% and 21% from lipid and protein respectively; the lipid was the main energy source in the early embryonic development.