Mitochondrial genome of ‘spotted numbfish’ Narcine timlei (Bloch & Schneider, 1801) and phylogenetic relationships among order Torpediniformes

Abstract

In this study, we report, for the first time, mitochondrial genome of Narcine timlei (Bloch & Schneider, 1801) and its phylogenetic relationships within the order Torpediniformes. Narcine timlei is a medium-sized ray that occurs in nearshore waters of the Indo-Pacific, classified as a ‘vulnerable’ category on the IUCN Red List. The mitogenome is assembled from short Illumina reads (150 bp paired-end reads). It is 17,964 bp long and includes 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The gene order, size, and nucleotide composition are largely consistent with mitogenomic characteristics of previously reported other Narcine spp. The slightly larger mitogenome length of N. timlei than other Narcine spp. may be due to the presence of a putative control region of 1,916 bp with three tandem repeats. Phylogenetic reconstruction using concatenated PCGs (n=13) of 9 Torpediniformes based on maximum likelihood and Bayesian inference analysis revealed identical topologies. The tree showed two main clades, one clade containing members of the family Narcinidae, and the second sister clade consisting of the families Narkidae and Torpedinidae. Our result supports the monophyletic nature of Narcinidae based on mtDNA. The information obtained in this study will contribute to a better understanding of the population genetics, phylogenetic analysis, conservation, and evolutionary biology research of N. timlei.