小黄鱼(Larimichthys polyactis)胚胎发育及仔、稚鱼形态特征观察

OBSERVATION OF EMBRYONIC, LARVA AND JUVENILE DEVELOPMENT OF SMALL YELLOW CROAKER, LARIMICHTHYS POLYACTIS

采用干法授精方法获得受精卵,在人工培育条件下对小黄鱼的胚胎及仔稚鱼形态发育进行观察,描述了各发育时期的发育时序和形态特征。结果表明,小黄鱼受精卵呈圆球形,无色透明,单油球,浮性,卵径(1413±73)μm,油球径(465±23)μm。在水温(18±0.5)?C,盐度28下,历时50h40min完成孵化。初孵仔鱼全长(3256±112)μm,卵黄囊长径(1260±50)μm,短径(894±65)μm,肌节32对。在水温(19±1)?C下,仔、稚鱼发育历时35天,4日龄仔鱼开口摄食,6日龄卵黄囊消失,10日龄油球消失,15日龄尾椎骨向上弯曲,25日龄全长(7467±550)μm,各鳍发育基本完成,进入稚鱼期,35日龄全长(22158±420)μm,全身被鳞,进入幼鱼期。

Eggs from the brood stock of small yellow croaker（Larimichthys polyactis） were artificially fertilized using standard dry method and hatched in laboratory under close observation on all developmental stages from May to June 2015. The observation showed that each of the fertilized eggs（（1413±73）μm in diameter） had an oil globule（（465±23）μm in diameter） and was transparent and buoyant. The hatching of fertilized eggs took 50h40 min in sea water（salinity 28） at（18±0.5）？C. The total lengths of newly hatch-out larvae were（3256±112）μm with a yolk sac（length of（1260±50）μm and height of（894±65）μm）, and the hatchlings had 32 myotomes. With the yolk sac shrinking, the larvae was ingested and transform to the mixed feeding stage on 4 DAH（day after hatching） in（19±1）？C water temperature. The yolk sac was consumed completely on 6 DAH and the oil-globule disappeared at 10 DAH. Notochord flexion began on 15 DAH and most fin rays formed on 25 DAH with total length（7467±550）μm. On 35 DAH, juvenile fish（（22158±420）μm in total length） grew up similar to adult fish in body shape, indicating transformation from the ontogeny to fingerling stage.