Characterization of RAG1 and IgM (mu chain) marking development of the immune system in red-spotted grouper (Epinephelus akaara)

► RAG1 and IgM cDNA sequences were sequenced and analyzed in Epinephelus akaara. ► Tissue distribution of RAG1 and IgM mRNA transcripts was determined. ► Expression pattern of RAG1 and IgM gene during development was examined. ► General morphology of thymus in E. akaara was characterized.