The Expression Pattern Of Opsin Genes In Early Development Of Two Snappers

Red emperor snapper （Lutjanus sebae） and crimson snapper （Lutjanuserythopterus）belong to genus Lutjanus，which widely distribute throughout thetropical and subtropical waters in the western Pacific and Indian oceans. They areboth important capture and aquaculture species in South China Sea. Embryos, larvae,and juveniles of red emperor snapper and crimson snapper are studied in this article，which employs early development and expression pattern of four opsin genes toanalyse the relationships between early development visual formation and externalenvironment in fishes of genus Lutjanus. The main results in the paper were presentedas follows:1. The morphological characteristics in early development of red emperorsnapper’s periods were observed preliminarily. Red emperor snapper’s embryodevelopment process undergoed6phases which included cleavage embryos stage,blastula stage, gastrulation stage, neurulation stage, organogenesis stage, hatchingstage. Fertilized eggs hatched in about24hours under the conditions of24.5℃. Thebody length of newly hatched larvae was about2mm. After3-5days,the larvaeopened its mouth for ingestion. After12-15days,the larvae developed intojuvenile.The body length of juvenile fish was about4.0-7.0mm, its pectoral fin, dorsalfin, anal anal fin were formed initially. After30-35days, the juvenile developed intoyoung fish. The body length of young fish was between25-40mm,with the finsdeveloped completely. Three spots were appeared distinctly in trunk. From themorphological features,the young fish was similar to the adult one..2. The expression of four opsin genes (LWS, SWS1, SWS2、RH) in earlydevelopment of red emperor snapper and crimson snapper were analysed by real-timequantitative PCR. The results showed that, in early development stages, includingMulti-cell stage、1/2epiboly stage、Closure of blastopore stage、Optic capsule stage、Eye lens formed stage、Heart-beating stage、Hatching stage、1day Larva afterhatching、5day Juvenile、10day Young fish,the expression pattern of four opsin geneswere similar of two snappers. Four genes of two sanappers all had significantexpression at1/2epiboly stage、closure of blastopore stage and optic capsule stage(P<0.05).Especially the mRNA levels of four genes were all highest expression at closure of blastopore stage. Remarkable decrease of expression levels were found at otherstages,and the expression of the Hatching stage was minimum. The relative expressionincreaed slightly in3larvae stages compared with the hatching stage. On the otherhand, the relative expression of four genes between the two snappers was analyzed inclosure of blastopore stage, RH gene was maximum,while,SWS2gene was minimumin two snappers.