Description of a new Pangasius (Valenciennes, 1840) species, from the Cauvery River extends distribution range of the genus up to South Western Ghats in peninsular India

Abstract

A new species of the genus Pangasius, is described based on 17 specimens collected fromthe Cauvery River, India. It can be distinguished from its sister species from Southand Southeast Asia, by its widely placed, small and rounded vomerine and palatinetooth plates, longer maxillary and mandibular barbels, greater vertebrae count 50 (vs.44–48), and smaller caudal peduncle depth (6.5–8.2% SL vs. 9.89–13.09% SL). Thetooth plates of the new species closely resembles that of Pangasius macronema but canbe clearly distinguished from the latter by having lesser gill rakers (16–19 vs. 36–45);a smaller eye (2.4–4.4% SL vs. 5.2–9.6% SL); and larger adipose-fin base (1.5–2.9%SL vs. 0.1–1.2% SL). The mitochondrial cytochrome c oxidase (COI) gene sequenceof the new species shows the genetic divergence of 3.5% and 5.1% from P. pangasiusand P. silasi respectively, the two sister species found in South Asia and India. Thespecies delimitation approaches, Poisson Tree Processes (PTP) and assemble speciesby automatic partitioning (ASAP) clearly resolved that the P.icaria is distinct from itssister species. Phylogenetic position of the species with its sister species was evaluatedusing maximum likelihood and Bayesian analysis. The discovery of this previouslyunknown species of genus Pangasius from the Cauvery River of peninsular Indiaindicates important biogeographical insight that this genus migrated till the southerndivision of Western Ghats