The complete mitochondrial genome of Parachiloglanis hodgarti and its phylogenetic position within Sisoridae

The complete mitogenome of Parachiloglanis hodgarti was sequenced and characterized,which is the first mitogenome of the genus Parachiloglanis within Sisoridae.The mitogenome is 16511-bp long and included 13 protein-coding genes,22 transfer RNAs,two ribosomal RNAs,and one control region.The genome composition was A+T biased(58.64%)and exhibited a positive AT-skew(0.095)and a negative GC-skew(-0.283).Compared with other Sisoridae fishes,the characteristics of nucleotide skews,codon usage,and amino acid usage of the P.hodgarti mitogenome are more similar to those of non-Glyptosternoid fishes.Furthermore,the phylogenetic trees show that Sisoridae fishes fall into four major clades and P.hodgarti(CladeⅠ)is basal to the Sisoridae family,forming a sister clade to the Glyptosternoids(CladeⅣ).The topological structures constructed in this study raised doubts over the traditional classification system.These results will help better understand the feature s of the P.hodgarti mitogenome and provide a reference for further phylogenetic research on Sisoridae species.

Phylogenetic relationships and estimation of divergence times among Sisoridae catfishes

Nineteen taxa representing 10 genera of Sisoridae were subjected to phylogenetic analyses of sequence data for the nuclear genes Plagl2 and ADNP and the mitochondrial gene cytochrome b. The three data sets were analyzed separately and combined into a single data set to reconstruct phylogenetic relationships among Chinese sisorids. Both Chinese Sisoridae as a whole and the glyptosternoid taxa formed monophyletic groups. The genus Pseudecheneis is likely to be the earliest diverging extant genus among the Chinese Sisoridae. The four Pareuchiloglanis species included in the study formed a monophyletic group. Glaridoglanis was indicated to be earliest diverging glyptosternoid, followed by Glyptosternon maculatum and Exostoma labiatum. Our data supported the conclusion that Oreoglanis and Pseudexostoma both formed a monophyletic group. On the basis of the fossil record and the results of a molecular dating analysis, we estimated that the Sisoridae diverged in the late Miocene about 12.2 Mya. The glyptosternoid clade was indicated to have diverged, also in the late Miocene, about 10.7 Mya, and the more specialized glyptosternoid genera, such as Pareuchiloglanis, originated in the Pleistocene (within 1.9 Mya). The speciation of glyptosternoid fishes is hypothesized to be closely related with the uplift of the Qinghai-Tibet Plateau.

A new species of sisorid catfish of the genus Exostoma from the Salween drainage, Yunnan, China

A new species of the sisorid catfish genus Exostoma Blyth, 1860 was collected from two hill-stream tributaries of the Nujiang （Salween River） drainage in Gaoligong Mountain, south-western Yunnan Province, China from 2003 to 2006 and from two tributaries of the Salween River in Cangyuan County Lingcang Prefecture, Yunnan Province, China （in 2007） and in Yongde County, Lingcang Prefecture, Yunnan Province, China （in 2015）. Exostoma gaoligongense sp. nov. is the 10th species of the genus and is most similar to E. vinciguerrae in morphology but can be distinguished by pelvic fin reaching anus vs. not reaching; maxillary barbels just reaching or slightly surpassing pectoral-fin origin vs. surpassing pectoral-fin origin or even reaching posterior end of gill membrane; abdominal vertebrae 23-25 vs. 25-27; length of dorsal fin/dorsal to adipose distance 90.3%-287.0% vs. 59.2-85.7. A key to Exostoma spp. is provided.

Diversification of Sisorid catfishes(Teleostei: Siluriformes)in relation to the orogeny of the Himalayan Plateau

Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine systems. Given the diversity of the group and the above qualities of these catfishes, this lineage serves as an ideal group for inferring the geological history of this region based on their phylogenetic relationships reflecting evolu- tionary history. We sequenced the complete mitochondrial genome and four nuclear genes of representative sisorids distributed across river systems in China. Phylogenetic analyses strongly support the monophyly of the Sisoridae and the glyptosternoids. An analysis of the reconstructed ancestral states derived from inferred genealogical relationships suggests that the evolution of this lineage was accompanied by convergent evolution in morphological traits that were presumably in response to environmental pressure involving the rapid flowing river system that were generated during the uplift of the Tibetan Plateau （UTP）. Molecular dating indicates that the Chinese sisorids and the glyptosternoids originated at the later Miocene （~ 10.9-9.8 Mya）, and with further biogeographic analyses indicates that the species of Sisoridae likely originated from a widely distributed ancestor. Moreover, the divergence of the Sisoridae in China can be divided into two phases consis- tent with the UTP. All of these results indicate that the diversification and dispersal events in this lineage occurred as a result of drainage systems formed during and after the UTP in the late Miocene and Quaternary periods.