大眼鳜胚胎发育的观察

OBSERVATION OF EMBRYONIC DEVELOPMENT OF SINIPERCA KNERI GARMAN

分别从嘉陵江采集到6批大眼鳜亲鱼进行人工催产,采用干法授精,在Nikon体视镜下对受精卵的发育过程进行观察,对不同发育时期进行显微照相。结果表明,大眼鳜成熟卵圆球形,微油黄色,无粘性。在水温13．9- 19．8℃条件下,受精卵历时183 h 18 min孵化出膜,初孵仔鱼全长4．6-5．2 mm,肌节数32-35对。同时,对大眼鳜、鳜鱼、斑鳜的胚胎发育进行了比较,在相同温度条件下,大眼鳜胚胎器官分化比斑鳜早,孵化时间比斑鳜短,且受精卵卵径小于斑鳜。斑鳜初孵仔鱼全长5．1-6．0 mm,肌节数42对。鳜初孵仔鱼全长3．6-3．9 mm,肌节数28对。嘉陵江大眼鳜视泡出现在胚孔封闭前,而鳜和斑鳜视泡出现在胚孔封闭后。油球的数量没有种的特异性,而与外力挤压等有关。

Six groups of the breeding fish of Siniperca kneri collected from the Jialing River were injected with hormones and artificially fertilized without water in April of 1997, 2000 and 2005, The developing fertilized eggs were examined continuously and photographed with a stereoscope. The mature fertilized eggs are spherical, non-viscous and slightly oleagigous yellowish. At 13.9 ～ 19.8℃, it takes 183.3 h for the fertilized eggs to hatch. Newly hatched larvae have a total length of 4.6 ～ 5. 2 mm with about 32 ～ 35 myomeres. Compared with the embryonic development of S. chuatsi Basilewsky and S. scherzeri Steindachner in the Jialing River, the fertilized eggs of S. kneri are smaller at the same temperature, has shorter time duration for hatching and earlier organ differentiation than those of S. scherzerL Newly hatched larvae of S, scherzeri have a total length of 5.1 ～ 6.0 mm with 42 myomeres while those of S.kneri are 3.6 ～ 3.9 mm long with 28 myomeres. The optic vesicle of S. kneri in the Jialing River appears before the closure of blastopore. In contrast, the optic vesicle of S. kneri in Xinfengjiang River Reservoir and S. scherzeri in the Jialing River appears after the closure of blastopore. The number of oil globular is not species-specific and appears to be related to the extrusion of outside forces.