黄海大头鳕胚胎发育过程

The Embryonic Development of Gadus macrocephalus Tilesius

驯化野生大头鳕（Gadus macrocephalus Tilesius）作为亲鱼,通过自然受精和人工授精两种方法获得受精卵,自然受精卵通过虹吸法收集。受精卵孵化条件为水温6~8℃,盐度32~33,pH7.8~8.2,微充气。在奥林巴斯SZ61解剖镜下对大头鳕的胚胎发育进行了观察,并使用CCD图像传感器拍照,描述了各发育时期的发育时序和形态特征。大头鳕受精卵为圆球形端黄卵,弱黏性,无油球,卵膜上具龟裂结构,卵子直径0.95~1.12mm,n=30,卵黄均匀透明。类似于大部分硬骨鱼类,其胚胎发育可分为胚盘形成期、卵裂期、桑椹期、囊胚期、原肠期、神经胚期、器官发生期、尾芽期、肌肉效应期。在水温6~8℃,盐度32~33的条件下,受精卵历时约336h完成胚胎发育过程,孵化出膜。在大头鳕胚胎发育过程中,具有4个不同于其他硬骨鱼类的地方：（1）发现早期分裂球具有不规则现象;（2）很多胚胎发育过程不出现柯氏囊,有柯氏囊的胚胎仅占10%左右,且出现晚,消失快;（3）胚胎孵化为仔鱼与发育进程关联性不大,孵化的仔鱼有3种主要形态;（4）胚胎各个时期都有较高死亡率,以原肠期最为严重。

The fertilized eggs of wild broodstock, Gadus macrocephalus Tilesius wereacquired through two methods, natural fertilization and artificial insemination. The naturallyfertilized eggs collected by flooding assay. The fertilized eggs were incubated in filtered sea water at 6~8℃, salinity 32~33, pH7.8~8.2, with subtle aerated. The ontogenetic embryos were observed using a Olympus SZ-61 microscope.The total development time of every stage was noted and calculated and the characteristic images were taken using a charge-coupled device（CCD）. The fertilized eggs were globular, single oil globule and the egg diameter was 0.95~1.12mm（n=30）. The embryonic developmentexperienced 336h including blastodisc stage, cleavage stage, blastula stage, gastrula stage, neurula stage, organogenesis stage, tail bud stage, heart beating stage and hatching stage.We found there were significant differences between Gadus macrocephalus Tilesiusand other teleost in some stages：1） unregular blastomeres in early cleavage; 2） devoid of Kupffer’s vesicle in most embryos during development, only 10% embryos could be observed and occurred later and disappeared earlier than other teleost; 3） the newly-hatched larvae were not related with certain developing stage, and there were three major ontogenetic patterns when the larvae hatched; 4） it has a high death rate during all the development stages, especially in gastrula stage.