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

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。

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

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 F1 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 min.There was no obvious difference in embryonic development between crossbreed F1 by E.moara×E.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.