欧洲舌齿鲈胚胎发育及仔鱼生长观察

Observation of embryonic and larval development of sea bass Dicentrarchus labrax

为了解欧洲舌齿鲈Dicentrarchus labrax胚胎及仔鱼发育特点,采用人工催产获得受精卵,在人工孵化条件下观察了欧洲舌齿鲈胚胎发育及仔鱼的形态变化与生长特征。结果表明:欧洲舌齿鲈受精卵呈圆形,浮性,卵径为(1.287±0.025)mm;在(13.0±0.5)℃水温条件下,胚胎发育分别历经了受精卵(0 h)、2细胞期(1.5 h)、4细胞期(2.0 h)、8胚叶期(2.5 h)、多细胞期(4.0 h)、桑椹胚期(4.5 h)、囊胚期(9.0 h)、原肠胚期(22 h)、胚胎轴出现期(37 h)、肌节及视囊出现期(48 h)、脑泡形成期(56 h)、心脏形成期(62 h)、尾芽期(68 h)、心脏跳动期(70 h)和孵出期(71 h)等阶段,历时72 h完成孵化过程;初孵仔鱼全长为(3.98±0.02)mm,在(13.0±0.5)℃水温下,0～9 d处于早期仔鱼阶段,孵化0～5 d的仔鱼游泳能力差,心脏、肠道、鳍等各器官继续发育,卵黄囊占身体较大比例;孵化5 d后的仔鱼,眼囊内晶体颜色变黑,体表黑色素聚集,卵黄囊明显变小;孵化后7 d的仔鱼,口裂和胸鳍鳍条形成,少数仔鱼开始平游,但无法摄食,仍靠卵黄囊提供营养;9 d后进入后期仔鱼阶段,孵化9 d的仔鱼几乎全部进入平游状态,肠道内可见食物,卵黄囊未完全消失,属混合营养期;孵化11 d的仔鱼卵黄囊彻底消失,营外源性营养;孵化13～17 d的仔鱼游泳能力增强,肠道充满食物,进入快速生长期;孵化17～19 d的仔鱼个体开始出现明显的大小差异;孵化19 d后鱼体变黑,各鳍基本形成,继续发育将进入稚鱼期;欧洲舌齿鲈仔鱼的混合营养期短,具有异速生长特性。本研究初步阐述了欧洲舌齿鲈的早期生活史特征,为欧洲舌齿鲈在中国的人工苗种繁育工作提供了理论参考。

The embryonic and larval development was observed in fertilized eggs of sea bass Dicentrarchus labrax with body weight of 3.3-3.4 kg induced by artificial hormone injection to spawn at water temperature of(13±0.5)℃ in order to reveal the developmental morphology and growth characteristics of embryo and larvae of sea bass. It was found that sea bass had pelagic and spherical fertilized eggs with diameter of(1.28±0.025)mm. At water temperature of(13.0±0.5)℃, embryonic development took 72 h and was divided into following stages: fertilized eggs(0 h), 2 cell stage(1.5 h), 4 cell stage(2.0 h), 8 cell stage(2.5 h), multi-cell stage(4.0 h), morula stage(4.5 h), blastula stage(9.0 h), gastrula stage(22 h), embryonic axis appearance(37 h), myomere and optic sac(48 h), period of blister formation(56 h), cardiac formation(62 h), tail bud period(68 h), heart beating period(70 h) and hatching period(71 h). The newly hatched larvae had total length of(3.98±0.02)mm and was in early larval stage 0-9 post hatching days(PHD). The larvae had poor swimming ability, and the organs such as heart, intestine and fins continued to be developing, with yolk sac accounting for a large proportion of the body 3-5 PHD. After 5 PHD, the crystals in the eye capsules turned into black in color, the melanin gathered on the body surface, and the yolk sac became significantly smaller. The 7 day old larvae had mouth cracks and pectoral fins, and a few larvae began to swim, and cannot feed, still being dependent on yolk sac for nutrition. After 9 PHD, the larvae developed into postlarval stage when almost all of the larvae normally swam, fed(food being visible in the intestines), with completely exhausted yolk sac, which was in transition period in endogenous and exogenous nutrition by 11 PHD. The 13-17 day old larvae had enhanced swimming ability, and the intestines filled with food in the rapid growth period. There was significant difference in size in the 17-19 day old larvae, with black skin and fins in 19 day old juveniles. The growth equation indicated that sea bass larvae had allometric growth and short period of transition period from endogenous to exogenous nutrition. This findings provided theoretical basis for further artificial reproduction and fry culture of sea bass.