Complete mitochondrial genome of Labeo fimbriatus (fringe-lipped carp) and insights into its evolutionary relationships within the genus Labeo.

BACKGROUND

Labeo fimbriatus (Bloch, 1795) is a medium-sized South Asian minor carp with ecological significance and emerging aquaculture potential, particularly in polyculture systems with Indian major carps. Despite its wide distribution, it remains underrepresented in phylogenetic studies, and limited genomic resources are available. Here, we report the complete mitochondrial genome sequence of L. fimbriatus, contributing to improved phylogenetic resolution and understanding of its evolutionary history.

METHODS AND RESULTS

The complete mitogenome of L. fimbriatus is 16,603 bp in length and comprises 13 protein-coding genes, 22 tRNA genes, and two ribosomal RNA (rRNA) genes, displaying the typical vertebrate mitochondrial gene order and strand asymmetry. Comparative mitogenomic analysis with 20 other Labeo species revealed codon usage bias, nucleotide composition skew, and gene-specific substitution rates. Specifically, atp6 and nad3 exhibited high genetic distances, indicating their potential as informative molecular markers for phylogenetic studies within the subfamily Labeoninae. The control region contains conserved elements, including the termination-associated sequence (TAS), conserved sequence blocks (CSBs), and a (TA) dinucleotide repeat. Phylogenetic analyses using Maximum Likelihood, Maximum Parsimony, and Bayesian Inference methods positioned L. fimbriatus as a sister species to L. rohita and L. catla, distinct from African congeners. Molecular clock estimation dated the origin of the Labeo genus to ~ 23.8 million years ago (MYA), with L. fimbriatus diverging from the common ancestor of L. rohita and L. catla ~ 13.04 MYA during the Middle Miocene.

CONCLUSIONS

This study presents the complete mitochondrial genome of L. fimbriatus and provides valuable insights into the molecular evolution, taxonomic relationships, and biogeographic history of Labeo species. The identification of rapidly evolving mitochondrial genes offers promising molecular markers for future genetic management and phylogenetic investigations of this underutilized species.