Mahseers genera Tor and Neolissochilus (Teleostei: Cyprinidae) from southern Vietnam 

Abstract

Two new species and two new basin records of mahseers in the genera Tor and Neolissochilus are described from the upper Krong No and middle Đồng Nai drainages of the Langbiang Plateau in southern Vietnam. These new species and new records are known from streams and rivers in montane mixed pine and evergreen forests between 140 and 1112 m. Their populations are isolated in the Sre Pok River of the Mekong basin, the middle of the Đồng Nai basin, and the An Lão River. Both new species are differentiated from their congeners by a combination of the following characters: 23-24 lateral scales, 9-10 predorsal scales, 2/7 or 1/8 pelvic-fin rays, mouth position, median lobe of lower lip, rostral hood, colour in life and by divergent mitochondrial DNA. Tor mekongensis sp. nov. is differentiated from Tor dongnaiensis sp. nov. by the number of transverse scale rows (3/1/2 vs. 4/1/2), number of pelvic-fin rays (2/7 vs. 1/8), a blunt rostral hood vs. pointed, caudal-fin lobes that are equal vs. unequal, and by mitochondrial DNA (0.7% sequence divergence). Molecular evidence identifies both species as members of the genus Tor and distinct from all congeners sampled (uncorrected sequence divergences >1.9% for all Tor species for which homologous COI sequences are available). Tor sinensis is recorded in the Krong No and the Sre Pok rivers, further south of its known distribution. Polymorphism is described in Neolissochilus stracheyi with a Tor-like morph and a Neolissochilus-like morph.

Disentangling the Taxonomy of the Mahseers (Tor spp.) of Malaysia: An Integrated Approach Using Morphology, Genetics and Historical Records

“…4). In addition, Yang et al (Hoàng et al, 2015) In addition to the biogeographical significance of the findings displayed in Fig. 4 …”

“…yingjiangensis are reported to occur in this region Hoàng et al, 2015) of which five 77 are assessed as "Data Deficient" on the IUCN Red List of Threatened Species™ (IUCN, 2015). The 78 confusing and contrasting evidence on species boundaries presented by different authors, and 79 exacerbated by the absence of voucher specimens for most records continues to constrain the validity 80 and value of any biological and demographic studies carried out on these fishes (Online Resource 1).…”

“…In his accompanying notes, he adds "it is variable with age" but does not 141 imply that T. tambroides has a larger lobe than T. tambra which is currently used as a diagnostic 142 feature (e.g. Mohsin and Ambak, 1983;Kottlelat, 2001;Hoàng et al, 2015). It is only in his later 143 descriptions (Bleeker, 1863, Online Resource 2) that the lobes are mentioned and used in the key to 144 distinguish the three species.…”

“…Tor species (Laskar et al, 2013) and Southeast Asian Tor species (Hoàng et al, 2015) previously, a 511 range of mitochondrial and nuclear genes e.g. COX1, COB, rag1 may be required to establish accurate 512 grouping when dealing with large phylogenies from the genus Tor, as they are known to hybridize (R.…”

Mahseer (Tor spp.) fishes of the world: status, challenges and opportunities for conservation

“…Two species, Tor dongnaiensis and T. mekongensis were recently described from the Upper Krong No and middle Dong Nai basins in Southern Vietnam (Hoang et al 2015). While T. dongnaiensis has been assessed as Near Threatened on the IUCN Red List (Version 2018-2) due to its apparent restricted distribution (Pinder and Harrison 2018) (Fig.…”