Ompok

Abstract: Ompok argestes, a new species of silurid catfish, is described from the southwestern lowlands of Sri Lanka. The new species is distinguished from all other species of Ompok in the Indian subcontinent by a combination of the following characters: body color pattern mottled; predorsal profile uniformly convex; maxillary barbels reach or extend slightly beyond base of dorsal fin; eye diameter 14.2–17.1% head length (HL); body depth at anus 19.8–22.3% standard length (SL); head width 14.3–16.8% SL; caudal peduncle depth 5.6–6.5% SL. Callichrous ceylonensis Gunther is shown to be a valid species that is apparently restricted to Sri Lanka, distinguished by a combination of the following characters: distinct concavity in predorsal profile; origin of pelvic fin beneath or slightly posterior to the origin of the dorsal fin; maxillary barbels 108–166 % HL; mandibular barbels 16.1–33.7 % HL; and 58–66 anal-fin rays.

Abstract: The identities of the nominal species in the Ompok hypophthalmus group of silurid catfishes, namely Ompok hypophthalmus, O. macronema and O. urbaini are verified in this study. Ompok macronema is hypothesized to be a junior synonym of O. hypophthalmus, and O. urbaini (previously considered a junior synonym of O. hypophthalmus) is hypothesized to be valid, distinct species. Ompok hypophthalmus is restricted to Java and the Barito River drainage in southern Borneo, and the material previously identified as O. hypophthalmus from Sumatra, the Malay Peninsula and Borneo represents O. rhadinurus, a new species.

Abstract: A DNA-based barcode identification system that is applicable to all animal species will provide a simple, universal tool for the identification of fish species. The barcode system is based on sequence diversity in subunit 1 cytochrome c oxidase (COI) gene. Identification and characterization of fish species based on morphological characters are sometimes found to be erroneous and environmentally affected. There are no studies on the genus Ompok in India at molecular level and species identification of the Ompok is usually carried out through morphological features. A total of 106 samples from three species Ompok pabda, O. pabo and O. bimaculatus were collected from eight sampling sites of seven Indian rivers. One hundred and six sequences were generated from COI region of three Ompok species and 21 haplotypes were observed. The sequence analysis of COI gene revealed three genetically distinct Ompok species and exhibited identical phylogenetic resolution among them. The partial COI gene sequence can be used as a diagnostic molecular marker for identification and resolution of taxonomic ambiguity of Ompok species.