Observation of embryonic, larval and juvenile development in Pampus argenteus offspring

Abstract

The embryonic,larval and juvenile development of the offspring obtained from cultured silver pomfret (Pampus argenteus) was observed,which contributed to the study of larvae rearing and breeding biology of pomfret.The eggs of silver pomfret were telolecithal,and had only one oil globule.The diameter of egg and oil globule were (1.417 ± 0.063) mm and (0.575 ± 0.031) mm,respectively.The hatching time was about 36 h after fertilization when the first larva was hatched at (20.0 ± 0.5) ℃,salinity 24 ± 1 and pH 8.0 8.5.Juvenile stage occurred 60 d after hatching (DAH) at 19.0 24.0 ℃,salinity 23 ± 1,pH 8.0 8.5 and 2 000 3 000 lx.There were 4 consecutive periods:pre-larval,post-larval,juvenile and young stages,during the development of silver pomfret.The morphological feature of pre-larval was the utilization of yolk sac.The post-larval was known as the occurrence of some organs such as esophageal sac,esophagus,stomach,pyloric caeca and liver.And the external character of post-larval was as follows:there were visible star-shaped melanin and golden spots in the two sides of fish body.And the primordium of dorsal and ventral fins was also occurred in the post-larval stage.In the juvenile stage,the digestive organs had been further developed.At 13DAH,the body length and height were (5.586 ±0.479) mm and (1.068±0.087) mm;the tail end of dorsal chord curved upward slightly,and then the hypural occurred.In the beginning,the end of hypural and body axis inclined to one another.At 35 DAH,hypural was perpendicular to the body axis.At 45 DAH,the body height increased significantly,and total body length and body height were (25.560±3.870) mm and (11.157±1.266) mm,respectively.In the young stage,pectoral fin had a sharp-pointed front end;caudal fin grew fast and formed forked;all fish scales had been formed.At 60 DAH,the body length and height were (41.000±3.300) mm and (19.750 ±1.620) mm,respectively.And there was no difference in the morphological feature between young fish and adult fish.In addition,the paper makes an analysis of the division of larvae and juvenile stages,difference in the embryo,larvae and juvenile developments between main species of pomfret,and key stages of death during artificial breeding of silver pomfret.