Mystus (Scopoli, 1777) is a genus of small to medium-sized edible riverine catfish found across South Asia. 18 species are present in Indian water bodies, out of 44 species worldwide. Traditionally, Mystus species are identified using morphological traits, but significant ambiguity exists due to morphological similarity Mystus and overlapping meristic counts. Especially the morphometric character of the three species Mystus gulio (Hamilton), Mystus montanus (Jerdon), Mystus cavasius (Hamilton) are similar and it leads to further study in DNA barcodes for resolving their taxonomic ambiguity. The cytochrome c oxidase I (COI) gene was used to assess the levels of genetic diversity among those three species. The sequence patterns were different among the three species.  The Total genomic DNA was isolated using phenol chloroform method. Amplification and sequencing of COI gene was done.  Phylogenetic tree was constructed for Mystus species using COI gene sequence to check whether DNA barcoding can be used to discriminate Mystus species (Lashari Punhal et al., 2018; Achom Dharshan et al., 2019). The sequence data was aligned and Neighbour joining (NJ) analysis was implemented, to build tree-type representations of the molecular divergences of COI utilizing CLUSTALX and MEGA 3 softwares. The sequence patterns clearly indicate that the three species slightly vary from each other species, Mystus gulio and Mystus cavasius are similar in sequence pattern and in their morphometric characters also and Mystus montanus slightly differ from other two species.

Keywords: cytochrome c oxidase I (COI) gene, DNA barcoding, Mitochondrial DNA, Mystus species