Mitochondrial DNA Analysis for the Cytochrome b Gene and D-loop Region from the Bull Shark Carcharhinus leucas

Abstract

Six marine and four freshwater specimens of the bull shark Charcarhinus leucas were collected from different areas in Latin America and Australia, and subjected to analysis for mitochondrial DNA sequences in the cytochrome b gene and D-loop region. The bull shark collected during our field survey contained two regions, D-loop and highly conserved cytochrome b region. There was no variation in the cytochrome b gene segment (405 bp) among seven specimens collected from the Atlantic Ocean and related river systems in Mexico and Nicaragua. However, there was one polymorphic site in the Australian shark compared with these sharks, while the 366th thymine was specific to Mexican marine sharks collected from the Pacific Ocean. Analysis of the D-loop region (484 bp) revealed 17 polymorphic sites among all samples examined. In contrast to the cytochrome b gene, two sequence patterns having one gap and four variable sites were recognized in the D-loop region among seven specimens collected from the Atlantic sites. However, the Australian freshwater shark and Mexican marine specimens from the Pacific Ocean showed their respective area-specific sequence patterns as in the case of the cytochrome b gene.