汉江中游银鮈的胚胎发育

The embryonic development of Squalidus argentatus in the middle reaches of Hanjiang River

于2004年5～8月对在汉江鱼类资源调查中采集的银鮈Squalidus argentatus卵的胚胎发育过程进行了观察.结果表明,受精卵吸水膨胀后具双层卵膜,内、外膜均吸水膨胀呈半透明状,外膜具微粘性.卵外膜直径为(3.60±0.42)mm,内膜直径为(1.88±0.12)mm;胚胎发育分为4个阶段、50个发育期.汉江中游银鮈与四大家鱼的胚胎发育趋势相似,但胚胎大小仅相当于家鱼的1/2～2/3,原肠期胚层下包较少,尾泡在听囊之前出现,尾鳍出现后至孵出前,胚体受内膜影响尾部向头部弯曲,胸鳍原基期在孵出前出现,胚前发育时间在相同温度条件下比家鱼少3～5 h;口裂在鳃弧出现后出现,没有明显的眼黄色素期,肠管形成后出现鳔的雏形,稚鱼阶段肌节有37对.

We have observed the embryonic development of Squalidus argentatus collected in Hanjiang River in May to August, 2004. The results show that the egg has 2 layers after having absorbed water. The outer layer is lightly glutinous with （3.60±0.42）mm, and the inner layer is （1.88±0.12） mm in diameter. The embryonic development may be classified into 4 phases and into 50 developmental stages. The embryo development trend of Squalidus argentatus in the middle reaches of Hanjiang River is similar to Chinese carps, but its size is only 1/2-2/3 of Chinese carps, and the process of the embryonic development is apparently different. Gastrulae embryo warps yolk sac less partly. The tail occurs earlier than the otolith. Between the tail fin appearance and the hatching, the fry bends toward the front, because of being effected by the inner layer. Rudiment of pectoral fin occurs before the hatching. In the same temperature, the whole embryonic development stage of Squalidus argentatus is 3-5 hours shorter than that of Chinese carps. The mouth appearance is later than that of the gill arch. There is no apparent xanthic eye stage. Emergence of air bladder occurs after the intestine formation stage, and the larvae have 37 pairs of myomeres.