拟赤梢鱼的胚胎发育和仔稚鱼生长特性观察拟赤梢鱼的胚胎发育和仔稚鱼生长特性观察

EMBRYONIC AND LARVAL-JUVENILE DEVELOPMENTAL CHARACTERISTICS OF PSEUDASPIUS LEPTOCEPHALUS

为阐明拟赤梢鱼(Pseudaspius leptocephalus)胚胎发育和仔稚鱼发育特点,采用人工催产的方式获得受精卵,观察分析了拟赤梢鱼胚胎发育和仔稚发育的时序特征。结果表明:拟赤梢鱼成熟卵粒为黄色圆球形,平均卵径为(1.77±0.20) mm,遇水具微黏性;在水温23℃条件下,胚胎发育经历合子期、卵裂期、囊胚期、原肠胚期、神经胚期、器官形成期和孵化出膜期7个阶段26个时期,共历时47h 55min完成孵化过程。初孵仔鱼在(23±1)℃水温条件下,经历卵黄囊期仔鱼(0—7d)、晚期仔鱼(8—26d)和稚鱼期(27—31d),进入幼鱼期;卵黄囊期仔鱼游泳能力差,随着卵黄囊逐渐消耗,体表色素斑、胸鳍和尾鳍等逐渐形成,消化道贯通,鳔充气;晚期仔鱼卵黄囊完全消失,仔鱼游泳能力增强,开口摄食,腹鳍形成,皮肤透明;稚鱼期鳞片形成并覆盖全身,鱼体形态已逐渐与成鱼无异。拟赤梢鱼仔稚鱼阶段全长生长特性公式为TL=0.0125x~2+0.3579x+6.2058 (R~2=0.9953),出膜15d内,仔鱼生长速度缓慢,全长日生长率仅为(0.38±0.02) mm/d, 15d后,仔鱼生长速度变快,全长日生长率可达(1.24±0.09) mm/d。研究初步阐明了拟赤梢鱼的胚胎发育和仔稚鱼发育的时序特征,为拟赤梢鱼的苗种规模化繁育提供了理论基础。

In order to verify the embryonic and larval-juvenile development characteristics of Pseudaspius leptocephalus,we continuously observed and analyzed the developmental process of the fertilized eggs obtained through artificial propagation of the parent fish.The results indicated that the mature eggs of Pseudaspius leptocephalus were yellow,and the mean diameters of the eggs were about(1.77±0.20)mm;moreover,the eggs were slightly sticky in the presence of water.At 23℃,the embryonic development of Pseudaspius leptocephalus lasted for 47h55min,and experienced ygophase,cleavage stage,blastula stage,gastrula stage,neurula stage,organogenesis stage and hatching stage were subdivided into 26 periods.At(23±1)℃,the newly-hatched larvae experienced the yolk-sac larvae(0—7d),the(8—26d),and post-larval stage(27—31d),and then entered the juvenile stage.The larvae had lower swimming capability at yolk-sac larvae stage;with the decrease of yolk-sac,the pigment spots on the body surface,the pectoral fin,tail fin and digestive tube were fully developed gradually,and the swim bladder inflation were also accomplished.Late stage larvae had better swim and feed abilities and the yolk-sac vanished;in addition,the ventral fin formation of late stage larvae completed and the skin were still transparent at this stage.Until the end of post-larval stage,there is no difference between the individuals and the adult fish in scale formation.The relationship between the total length of Pseudaspius leptocephalus with days post hatch were in accord with equation TL=0.0125x2+0.3579x+6.2058(R2=0.9953),indicating that the larvae grow slowly within 15 days post hatch with only(0.38±0.02)mm per day,and larvae grow very fast and reached(1.24±0.09)mm per day after 15 days.In this study,we illuminated the embryonic and larval-juvenile development characteristic,and provided theoretical basis to large-scale propagation and breeding of Pseudaspius leptocephalus.