Abstract:Frozen sperm from Epinephelus lanceolatus and eggs from E. bruneus and E. moara were used for artificial insemination. The metamorphosis development and growth of larval juvenile of the two hybrid offspring, Helong grouper (E. bruneus♀×♂E. lanceolatus) and Yunlong grouper (E. moara♀×♂E. lanceolatus), were observed and compared. The results showed that the rates of fertilization of the two hybrids were similar, but the malformation rate in the Helong grouper was higher than that of Yunlong grouper, while the hatching rate was lower than that of the Yunlong grouper. The post embryonic development of hybrid offspring was divided into larval stage, juvenile stage and young fish stage based on the features of the yolk-sac, the second dorsal fin spine and the first pelvic fin spine, scale and body color. At temperature of 24~26℃ and salinity of 29~31, DO≥10 mg/L, the yolk sac of Helong grouper and Yunlong grouper disappeared 5 days after hatching (dah). At 41 dah, these two species of fish transited to the juvenile stage at the same time, and the lengths of the second dorsal fin spine and the pelvic fin spine were (9.74±0.42) mm and (7.79±0.39) mm, and (9.59±0.46) mm and (5.81±0.09) mm, respectively, reaching the longest value, and then began to shorten. At 51 dah, Helong grouper juvenile fish completed metamorphosis and transited to the young stage with a total length of (25.46±1.16) mm. The time of Yunlong grouper transited to the young stage was later than Helong grouper (56 dah), with the total length of (23.24±1.21) mm. At 62 dah, there were four brown patches on the body surface of the Helong grouper, and six brown patches on the body surface of the Yunlong grouper. The growth rate of the Helong grouper was greater than that of the Yunlong grouper, and the whole length of the Helong grouper was 1.04 times as long as that of the Yunlong grouper at 70 dah; the Helong grouper showed a faster growing heterosis than the Yunlong grouper. The daily growth formula of the full length of the Helong grouper was L=2.6208e0.0465x, R²=0.9603 and that of the Yunlong grouper was L=2.7158e0.0453x, R²= 0.9451. The relationship between preanal distance and days for the Helong grouper was P=1.3371e0.0483x, R²=0.9643 and that of the Yunlong grouper was P=1.4017e0.0467x, R²=0.944. At 1 dah, the daily growth rates of the full length Helong groupers and Yunlong groupers reached the maximum, were 27.89% and 30.03%, respectively. At 13 dah, the daily growth rate of preanal distance of the brown Helong grouper was the maximum (25.21%), and that of Yunlong grouper reached a maximum (27.01%) at 12 dah. The results of this study showed that the Helong grouper expressed faster heterosis than the Yunlong grouper, and provided abundant biological data for the growth and breeding of crossbred offspring from the same father but a different mother grouper.
