云纹石斑鱼(♀)×七带石斑鱼(♂)杂交子一代胚胎发育及仔稚幼鱼形态学观察

Embryonic and morphological development in larva,juvenile,and young stages of F1 by Epinephelus moara(♀)×E.septemfasciatus(♂)

以云纹石斑鱼(Epinephelus moara)♀为母本,七带石斑鱼(E.septemfasciatus)♂为父本进行种间远缘杂交,系统观察了杂交子一代胚胎及仔稚幼鱼的生长发育及形态特征。对杂交子一代的胚胎发育按卵裂期、囊胚期、原肠胚期、神经胚期和器官形成期各阶段进行观察,在水温21～22.5℃、盐度29、pH 8～8.1的海水中,整个胚胎发育过程经35 h 20min完成。根据在卵黄囊期、第二背鳍棘和腹鳍棘生长消退过程、鳞片生长、体表色素变化的不同,观察比较了胚后发育的仔鱼期、稚鱼期、幼鱼期形态特征。鱼苗培育至58 d后完成了稚鱼至幼鱼的变态:初孵仔鱼4 d以前为内源性营养(卵黄囊仔鱼);4 d后开口摄食,为外源性营养;(42±2)d基本完成变态进入稚鱼阶段,(58±4)d全身被鳞,进入幼鱼期。同时,用同一母本(云纹石斑鱼)同批卵与同种雄鱼采集的精子授精后获得的受精卵作为对照组,进行孵化和仔稚幼鱼培育,与杂交子一代进行比较,结果发现杂交子一代在仔稚幼鱼阶段生长速度快于云纹石斑鱼,与七带石斑鱼相近。

Hybridization is the most widely used and effective method of artificial breeding in aquaculture. To de- velop grouper species that were fast growing and tolerant of low temperatures, we conducted hybridization be- tween Epinephelus moara （♀） and E. septemfasciatus （♂） by artificial methods. We documented embryonic de- velopment and the growth and morphological characteristics of larva, juveniles, and young fish in the hybrid F1. The embryonic development of the hybrid F1 was divided into cleavage stage, blastula stage, gastrula stage, neu- rula stage, and organogenesis stage. In sea-water （21-22.5 ℃, salinity 29, pH 8-8.1）, 35 h 20 min was required for hybrid F 1 embryonic development. The 2-cell stage occurred 1 h post fertilization （pf）; the 16-cell stage at 2 h 25 min pf; the multi-cell stage at 3 h 50 min pf; the high blastula stage at 5 h 10 min pf; the middle gastrula stage at 12 h 40 min pf; the embryo body stage at 16 h pf; the closure of blastopore stage at 17 h 50 min pf; the muscle burl stage at 20 h 50 min pf; the brain vesicle stage at 24 h 50 min pf; the crystal stage at 31 h 05 min pf; the heart-beating stage at 32 h 40 min pf; the hatching stage at 35 h 10 min pf; and the newly hatched larvae stage at 35 h 20 rain. There was no obvious difference in embryonic development between crossbreed F1 by E. moaraxE.septemfasciatus and E. moara, except the time of the heart-beating stage. Based on the features of the yolk sac, second dorsal fin spine, pelvic fin spine, scales, and body color, the post-embryonic development of the hybrid F1 was divided into larval, juvenile, and young fish stages. The larvae relied on their yolk for nourishment up to 4 d after hatching, at which time the mouth opened. Metamorphosis was completed -42±2 d after hatching at which time the fish were classified as juveniles. The juvenile stage lasted for -58±4 d, after which the juveniles became young fish. Our results suggest that the hybrid F1 grows more rapidly than either parent species.