卵形鲳鲹早期发育的研究

Early development of Trachinotus ovatus

观察了卵形鲳鲹(Trachinotus ovatus)人工繁殖和育苗过程的早期特征,结果表明:卵形鲳鲹早期发育可以分为仔鱼期、稚鱼期和幼鱼期3个阶段。受精卵在水温(24.73±2.11)℃,盐度20～24,pH8.0～8.2条件下,经过36～48h孵出仔鱼。初孵仔鱼全长(2.025±0.367)mm,肌节数23,出现胸鳍芽;2d时鳔出现一个室,且开始充气;4d时卵黄囊吸收完毕,此时仔鱼进入混和营养阶段;5d时背鳍、臀鳍原基出现,尾鳍出现,脊索周围出现3～4条黑色素带;6d时油球消失,仔鱼尾索弯曲,仔鱼饱食后体色变为银色,进入后期仔鱼阶段;12d时第二鳔室出现;14d时腹鳍开始形成;18d时各鳍基本发育完成,尾部出现鳞片,进入稚鱼期;22d时稚鱼布满鳞片,体色为银色,形态上已和成鱼相似,进入幼鱼期。全长、体长、肛前长、体重、体高、眼径与日龄呈明显的指数函数关系,体高与全长的比逐渐变大,至24d保持稳定。

The morphological characteristics of early development of Trachinotus ovatus were observed and described in March and May 2008, The fertilized eggs were hatched out about 36 - 48 h in conditions of water temperature （24.73 ± 2.11 ） ℃, salinity 20 - 24, pH8.0 - 8.2. Due to developmental process of T. ovatus, early development could be divided into three periods, namely larva, juvenile and young fish. The body of the newly-hatched larva was covered with fine melanin, lying at the bottom quietly, with 23 pairs of muscle nodes completely since yolk was exhausted. Five days after hatching, caudal tip lifting stage begins, and primordium of dorsal fin, anal fin appeared, the three or four black pigment strips of body surface were formed around the notochord. Six days after hatching, oil globule was exhausted, the larvae tail notochord become askew up, the body color changed into silver after engorgement. Twelve days after hatching, the second chamber air bladder is formed. Fourteen days after hatching, pelvic fin stage was formed. Eighteen days after hatching, all fins had completely developed; it means the beginning of juvenile stage. Twenty-two days after hatching, juveniles have scales, body color of juvenile was silvery, at which time the juveniles resembled adults in appearance, it means the beginning of young fish stage. Highly significant exponential function correlated between days after hatching and total length, body height, pre-anal length, weight, body height, eye diameter. The ratio of body length to body height increased, and twenty-four days after hatching the ratio begins to keep stable.