Abstract: Partial sequences of mitochondrial 16S rRNA, Cytb and COⅠ genes were amplified and sequenced in Pacific pomfretBramajaponicaand pomfretTaractichthyssteindachneriin order to evaluate the genetic variance in the two species. Three homologous fragments of 491 bp for 16S rRNA, 478 bp for Cytb and 558 bp for COⅠ genes were obtained by sequences aligning, and two insertion or deletion of sites were found in the 16S rRNA gene fragment. The nucleotide composition analysis indicated that there was no significant difference in G+C content in the three fragments in the two species (47.27% in Pacific pomfret and 46.59% in pomfret), a strong bias against guanine(G), especially in the third codon positions of Cytb and COⅠ genes(9.80% in Pacific pomfret and 12.31% in pomfret). Significant difference in genetic variance between the two species was observed in the three mtDNA fragments in which 204 nucleotide substitutions were checked in the total 1529 bp nucleotides analyzed, and nucleotide substitutions in the two protein coding genes were mainly found at the third codon positions. The net genetic distances were 0.112 7 in 16S rRNA, 0.166 4 in Cytb, and 0.135 3 in COⅠ gene fragments between the two species, showing intergenus differentiation within family. NJ phylogenetic tree revealed that the relationship between pomfret andXenobramamicrolepiswas closer than that between pomfret and Pacific pomfret. It is speculated based on sequence analysis of partial Cytb gene that the divergence between Pacific pomfret and pomfret is derived about 8.32 million years ago, in Miocene.
2014, Vol. 29 
