黄条鰤早期生长发育特征

Morphometric characteristics of the embryonic and postembryonic development of yellowtail kingfish, Seriola aureovittata

观察和记录了黄条鰤(Seriolaaureovittata)早期生活史阶段生长发育的形态与数量特征,描述了胚胎和仔稚幼鱼各发育阶段的表观特征与生长特性。黄条鰤成熟卵子为透明的圆球形浮性卵,卵径(1.48±0.04)mm,单油球,油球径(0.37±0.02) mm。在水温(21.5±0.5)℃,盐度32, pH 8.0～8.2条件下,受精卵历经73 h 40 min破膜孵化。初孵仔鱼全长(4.23±0.39) mm,卵黄囊长椭圆形,长度约为全长的1/3。3日龄仔鱼全长(4.61±0.43) mm,开口,卵黄囊消耗95%,眼睛变为黑色,鳔原基形成。4日龄仔鱼全长(4.57±0.88) mm,肛门与外界联通,开始摄食轮虫。5日龄仔鱼全长(4.68±0.25) mm,卵黄囊耗尽,鳔开始充气。油球在8日龄消耗完毕,仔鱼全长(5.14±0.36) mm,完全进入外源性营养阶段。7日龄仔鱼全长(4.79±0.36) mm,鳔充气变为亮泡状。初孵仔鱼消化道细而直,随着仔鱼发育,消化道变得粗大,肠道内褶回增多,在10日龄仔鱼全长(5.19±0.37)mm,形成第一个肠道生理弯曲,15日龄仔鱼全长(5.71±0.50)mm,形成第二个肠道生理弯曲,消化能力不断增强。脊椎末端弯曲在15日龄开始,至25日龄全长(8.66±1.06)mm,弯曲过程完成。35日龄稚鱼全长(20.04±1.56)mm,各鳍条数与成鱼一致。60日龄幼鱼全长(65.06±1.94) mm,鳞片形成。80日龄幼鱼全长(134.05±3.25) mm,体表出现一条纵向横贯眼睛和尾椎末端的浅黄色色素带,在体态上与成体无明显区别。

The yellowtail kingfish,Seriola aureovittata,is a globally distributed marine economic pelagic fish species.It is a popular table fish all over the world for its tasty flesh and high nutritional content.As the consumption demand has increased and natural resources have declined in recent years,an increasing number of countries including China have begun to artificially culture this species due to its fast growth and market value.It is particularly suitable for the deep sea net cage culture method and is thus a promising candidate for the deep sea farming industry in China.Studying the morphometrics and physiology of embryos,larvae,juveniles,and young fish to obtain information about their early life history is the first step and key to the successful aquaculture of a fish species.Thus,we observed,recorded,and described the morphometric characteristics of the embryonic and postembryonic development of S.aureovittata in order to provide basic knowledge for the artificial breeding and seedling production of this species.The fertilized eggs obtained by natural spawning were spherically shaped and buoyant.The fertilized eggs were transparent and had one oil globule in the yolk,with an egg diameter of (1.48±0.04) mm and an oil globule diameter of (0.37±0.02) mm.The fertilized eggs hatched 73 h 40 min after fertilization in (21.5±0.5)℃ water with a salinity of 32 and a pH of 8.0-8.2.The total length (TL) of the newly hatched larva was (4.23±0.39) mm and consisted of a long oval yolk sac,which accounted for one third of the TL.The larvae opened their mouths and exhibited blackened eyes at 3 days after hatching (DAH) with a TL of (4.61±0.43) mm.At this time,the yolk sac decreased in volume by approximately 95%,and the swim bladder primordium formed.Larvae at 4 DAH were (4.57±0.88) mm in TL and began to feed on rotifers,thus entering the mixed feeding stage.Five DAH,the larvae with a TL of (4.68±0.25) mm exhausted the yolk sac and the swim bladder began to inflate with air.The oil globule was absorbed at 8 DAH,and the larvae (TL 5.14 mm±0.358 mm) completely entered the exogenous nutritional stage.The swim bladder of the larvae at 7 DAH (TL of 4.79± 0.36 mm) became a bright vesicle after inflation with air,which exists through their life history.The intestine of the newly hatched larvae was thin,short,and straight,but became long,curled,and complicated with development.The first intestinal physiological curve formed at 10 DAH when the larvae were (5.19±0.37) mm in TL and the second formed at 15 DAH when the larvae reached (5.71±0.50) mm in TL.Flexion of the notochord started at 15 DAH and was completed at 25 DAH when the larvae were (8.66±1.06) mm in TL.The development of the dorsal fin,pectoral fin,anal fin,and caudal fin was completed by the time the juveniles were (20.04± 1.56) mm in TL.At 60 DAH (TL 65.06 mm±1.94 mm),the scales on the body surface formed.At 80 DAH,when the young fish achieved (134.05±3.25) mm in TL,their appearance was similar to that of the adults.