RESUMEN
Opsarius siangi sp. nov., a previously undocumented species, has been identified from Siang River, Pasighat, Arunachal Pradesh, India. This newly described species is distinguished by a suite of unique morphological characteristics, notably including a complete lateral line, consisting of 65-77 scales, 32-39 pre-dorsal scales, 12-15 scales positioned between dorsal fin origin and lateral line, presence of two pairs of barbels, body depth ranging from 18.80% to 27.42% of standard length and a distinct pattern of 8-15 vertical bars adorning the body. A comprehensive genetic analysis was conducted by scrutinizing 78 Cytochrome oxidase I (COI) sequences extracted from Chedrinae fishes, with particular focus on Opsarius and Barilius genera. Phylogenetic analysis revealed that O. siangi sp. nov. occupies a distinctive clade, displaying close affinity with O. shacra. Intraspecific K2P genetic divergence, assessed at 0.02, falls well within established species delineation thresholds, while interspecific divergence in comparison to O. shacra was recorded at 0.112. Complementary species delimitation methodologies, including BIN and bPTP, further underscore taxonomic uniqueness of O. siangi sp. nov., within Chedrinae family. This description enriches our understanding of biodiversity within Siang River ecosystem and underscores the merit of employing multi-pronged approaches in taxonomic investigations.
RESUMEN
BACKGROUND: The taxonomic status and geographical distribution of M. tengara are vague. No genetic diversity and phylogenetic study have been done till now to resolve its identity and distribution. In the present study, an integrated taxonomic approach has been applied to clarify the taxonomic status, identity, and distribution of bagrid catfish, Mystus tengara. METHODS AND RESULTS: Comparative morphometric evaluation of M. tengara identified in the present study from distant geographical locations revealed variations of the traits in response to body length and environment, without significant genetic distance. The observed morphometric traits of M. tengara were found to be overlapping with available morphometric traits of M. tengara, M. carcio and M. vittatus. Maximum likelihood and Bayesian phylogenetic analysis based on mitochondrial cytochrome c oxidase (COI) gene also could not resolve their identity, and five paraphyletic clades comprising of M. tengara, M. vittatus, and M. carcio from India, Nepal, and Bangladesh were observed. Morphological and genetic evidence along with comparative evaluation of M. tengara, from its type locality, we consider M. tengara identified in the present study to be true, with its distribution extending from North East India to West Bengal, North India, Central India, Northern peninsular India, and Bangladesh. CONCLUSION: The observation of paraphyletic subclades and evaluation of genetic distance between subclades reveals the presence of four cryptic species. Further confirmation on the identity of M. vittatus and M. carcio, by an integrated taxonomic approach based on fresh specimens collected from the type locality, is required.
