The complete mitochondrial genome of the grey bamboo shark (Chiloscyllium griseum) (Orectolobiformes: Hemiscylliidae): genomic characterization and phylogenetic application

The complete mitochondrial genome of the grey bamboo shark, Chiloscyllium griseum (Orectolobiformes: Hemiscylliidae) was obtained, with a total of 16 755 base pairs (bp). The mitogenome encoded 13 protein-coding genes, two ribosomal RNAs, 22 transfer RNAs and a noncoding control region, a gene arrangement identical to the most common type found in vertebrates. All tRNA sequences were folded into typical cloverleaf secondary structure with the exception of tRNA-Ser2, in which the DHU arm stem was replaced with 12 unpaired nucleotides and formed a simple loop. In the control region, the putative termination-associated sequences (TAS) with hairpin-loop structure and the conserved sequence blocks (CSB) I-III were identified and considered to be associated with the replication and transcription of mtDNA. No repeat motifs were found in the mitogenome of C. griseum. On the basis of the mitogenomic data available in the Class Chondrichthyes from both Genbank and this study, and the phylogenetic analyses using maximum likelihood (ML) and Bayesian inference (BI) methods, the results strongly support the basal division between batoids and sharks and the monophyly of the Superorder Galeomorphii, and confirm the phylogenetic position of C. griseum in the Subclass Elasmobranchii. This study suggests that the mitogenomic data are more robust for reconstructing phylogenetic relationships than individual genes in the Elasmobranchii.