Systematic status of Systomus rubrotinctus Jerdon (Teleostei: Cyprinidae) with notes on the Puntius arulius group of fishes

Abstract

Systomus rubrotinctus Jerdon has long been considered a synonym of Puntius arulius. Examination of ‘P. arulius’ collected from various parts of the Western Ghats revealed the presence of two distinct species: and the fish considered by Day as ‘P. arulius’ from Wayanad is in fact P. rubrotinctus. Based on the colour pattern, morphometrics and meristics, P. rubrotinctus is retrieved from the synonymy of P. arulius and redescribed. Puntius rubrotinctus can be distinguished from P. arulius by the unique colour pattern consisting of three well-defined black blotches on the body, two scales high and three scales wide, as distinct from the diffused blotches in P. arulius. It further differs from P. arulius in having a shorter dorsal-to-hypural distance (49.8-54.6 % SL, vs. 57.3-57.6 % SL), a smaller interorbital width (28.4-35.6 % HL, vs. 39.1-39.7 % HL) and a higher number of gill rakers (10-11 in the first gill arch, vs. 8). Puntius rubrotinctus is wide distributed in the Cauvery River and its tributaries in the Western Ghats region across the states of Kerala, Karnataka and Tamil Nadu. The results revalidate the identity of the ‘Puntius filamentosus group’ of previous authors drawing attention to the presence of intermediate forms among this group, in which natural hybrids appear to occur, of which P. exclamatio may be one.