Karyotypic and Morphometric Analyses of Dawkinsia Rohani (Cyprinidae), An Endemic Barb from The Western Ghats, India

The current study provides the first karyotypic and morphometric characterisation of Dawkinsia rohani, an endemic ornamental cyprinid fish species from the Western Ghats, India. Specimens obtained from the local aquarium trade sources were subjected to standard cytogenetic protocols involving colchicine treatment, hypotonic treatment in KCl solution, and fixation in Carnoy's fixative. Chromosomes prepared from kidney and gill tissues were stained conventionally with Giemsa solution. Karyotypes constructed from about 200 well-spread metaphase plates revealed a diploid chromosome number (2n) of 50 and a fundamental number (NF) of 74 in both sexes. The karyotype formula was determined as 2 m + 22 sm + 14 st + 12 t, with chromosome lengths ranging from 5.64 μm (largest submetacentric) to 2.48 μm (smallest subtelocentric) in the karyotypes. The ideogram showed a gradual decrease in chromosome size across pairs, consistent with the typical cyprinid karyotypic pattern. Morphometric analysis indicated an elongated and laterally compressed body with distinctive colouration: greenish dorsally and cream- white ventrally, with black and reddish fin markings. The results confirm that D. rohani conforms to the modal karyotype of Cyprinidae (2n = 50) and provide the first cytogenetic reference for this vulnerable, endemic species, which is invaluable for future taxonomy, evolutionary, and conservation genetics studies.