Differentiation of fin during early developmental stages of the rock bream Oplegnathus fasciatus

The ontogeny of the fin on larvae of Oplegnathus fasciatus during early developmental stages was observed.Larvae were nursed in outdoor cement tanks at 24-28 ℃,salinity 28-32,and pH 7.6-8.4.The median fin-fold of 0-day-old larvae fish,which originated from the head to the tail,ended at the anus.Pectoral fin appeared in the 3 days after hatch(DAH) larvae fish.When the larvae fish was 8 DAH,the underside of the end of vertebra thickened.The end of vertebra warped up and the base of ventral fin began to develop on the 12 DAH.On the 15 DAH,the fin ray was found at pectoral fin,and the other fin rays were formed at the pterygiophore of dorsal fin and anal fin.Meanwhile,the rounded caudal fin became truncatus,and 2 sloft rays appeared at ventral fin.In the 20 DAH,the dorsal,anal and caudal fins commenced segmenting,and 4 transparent and non-pigmented fin rays were formed at the ventral fin.The caudal fin was long truncatus and slight concave.When the fish was 30 DAH,each fin ray was fully developed,and the fin rays of anal fin branched.The ventral pectoral and caudal soft rays were not pigmented yet,but the fin spines of dorsal and anal were already pigmented.The fin rays and ventral fins were partly and fully pigmented respectively.With all fin rays completely developed,the fish was turned into young fish in the 40th day,and shape was similar as adult fish.Relationship between length of the pectoral fin and total length was linear regression of O.fasciatus.Growth increased with the day.Pectoral fin of O.fasciatus formed the earliest,and then caudal fin,dorsal fin,anal fin,ventral fin.