Comprehensive mitogenomic insights into Hemibagrus velox endemic to Sumatra, Indonesia and its phylogenetic relationships within the Bagridae lineage

The Bagridae (Actinopteri: Siluriformes) catfish Hemibagrus velox, endemic to Sumatra, Indonesia, raises critical taxonomic concerns due to limited molecular evidence. Recent advances in mitogenomic approaches offer a robust framework for resolving such ambiguities. Accordingly, the present study aims to characterize the complete mitogenome of H. velox and to conduct a comprehensive comparative analysis of gene structure and variation among its congeners, as well as to evaluate its phylogenetic position within the broader bagrid lineage. The current investigation reveals the mitogenome of H. velox (16,512 bp), comprising 37 genes, a non-coding control region (CR), an overall A + T bias of 58.09%, eleven intergenic spacers, and six overlapping regions. Most protein-coding genes (PCGs) in Hemibagrus species initiated translation with the standard ATG start codon, except for the COI gene (GTG). The amino acid composition analysis exhibited a high frequency of leucine, serine, and arginine residues, whereas methionine and tryptophan were the least abundant. The ratio of nonsynonymous to synonymous substitutions indicated strong purifying selection acting on the PCGs across Hemibagrus species. The secondary structure of 21 transfer RNAs showed the typical cloverleaf structure, except for tRNA-Ser (S1). The comparative analysis of conserved sequence blocks within the CR among eight Hemibagrus species established variation in length and nucleotide composition, with tandem repeats exclusively found in H. guttatus within the extended termination-associated sequence region. The phylogenetic analyses employing Bayesian inference, Maximum-likelihood, and Neighbor-joining methods demonstrated that Hemibagrus is a non-monophyletic group within the family Bagridae. Collectively, this study provides a detailed genetic characterization of H. velox and its seven congeners. The inferred matrilineal evolutionary pattern further strengthens earlier hypotheses regarding the delineation of genera within the broader Bagridae lineage. Furthermore, the findings underscore the urgent need to expand mitogenomic datasets for other bagrid catfishes to enhance the resolution of their systematics, evolutionary relationships, and biogeographic interpretations, thereby facilitating evidence-based conservation efforts and effective fisheries management.