Molecular systematics of the Labeonini inhabiting the karst regions in southwest China (Teleostei, Cypriniformes)

Complete mitochondrial genome of Guigarracailaoensis Wang, Chen & Zheng, 2022 (Cypriniformes, Cyprinidae) and its phylogenetic implications

Guigarracailaoensis is a member of family Cyprinidae, subfamily Labeoninae (Cypriniformes) which was recently discovered in southwestern China. Following its initial description, additional information on this species has remained notably scarce. In the current study, we assemble the complete mitochondrial genome (mitogenome) of G.cailaoensis using the Illumina sequencing platform. The mitogenome is identified as a circular, double-stranded DNA sequence of 16,593 base pairs, encompassing 13 protein-coding genes (PCGs), 22 transfer RNA genes, two ribosomal RNA genes, and a putative control region. Maximum-likelihood and Bayesian-inference approaches were used to construct phylogenetic trees for three datasets: (i) PCG sequences of the complete mitogenome (dataset 1); (ii) PCG sequences of the complete mitogenome combined with nuclear DNA (ncDNA) (Rag1) sequence (dataset 2); and (iii) ncDNA (Rag1) sequences (dataset 3). Phylogenetic analyses position G.cailaoensis as a sister taxon to the lineage consisting of Paraqianlabeolineatus Zhao, Sullivan, Zhang & Peng, 2014 and Pseudogyrinocheilusprochilus Fang, 1933 in dataset 1, and to Pseudogyrinocheilusprochilus in dataset 2, species lacking an oral disc on the lower lip. However, G.cailaoensis showed a close relationship to the lineage consisting of Discogobio and Discocheilus in dataset 3, species possessing an oral disc on the lower lip. Nonetheless, a variety of species with an oral disc on the lower lip are clustered into different lineages across the three datasets that may indicate that the development of the oral disc is homoplastic within the subfamily Labeoninae. The outcomes of this study have the potential to support conservation efforts for this species and to enrich our understanding of genetic resources in the area.

Complete mitochondrial genome of Rectorisluxiensis (Teleostei, Cyprinidae): characterisation and phylogenetic implications

Mitochondrial genomes (mitogenomes) are widely used in scientific studies on phylogenetic relationships, molecular evolution and population genetics. Here, we sequenced and analysed the mitogenome of Rectorisluxiensis, a Yangtze River drainage endemic, but threatened cyprinid fish of Labeoninae. The complete mitogenome of R.luxiensis was 16,592 bp in length, encoding 13 protein coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs) and a control region. The mitogenome showed a high A+T content (58.2%) and a positive AT-skew (0.10) and negative GC-skew (-0.25) base composition pattern. All the 13 PCGs were found to start with ATG codons, except for the COXI, in which GTG was the start codon. The ratio of non-synonymous and synonymous substitutions (Ka/Ks) of all the 13 PCGs were less than 1, indicating negative or purifying selection evolved in these genes. Comparatively speaking, the evolutionary rate of ATP8 was the fastest and ND4L was the slowest. All tRNAs could fold into a typical cloverleaf secondary structure, except tRNA^Ser1 that lacked a dihydrouridine arm. Phylogenetic relationships, based on the PCGs dataset of 91 mitogenomes of Labeoninae, showed that R.luxiensis grouped with Rectorisposehensis and they formed a monophyletic Rectoris. However, many non-monophyletic genera were revealed in labeoninae fishes, such as Cirrhinus, Decorus, Garra, Labeo and Pseudocrossocheilus, which indicated that the validities of some traditional genera required a further check. This study reported the complete mitogenome of R.luxiensis for the first time, which provided valuable data for future molecular evolution and conservation related studies of Rectoris and other species in Labeoninae.

The complete mitochondrial genome of Paraqianlabeo lineatus (Cyprinidae: Labeoninae)

Paraqianlabeo lineatus is a small-sized fish which is endemic to Guizhou province, China. The complete mitochondrial genome of P. lineatus is 16,598 bp in total length, with 37 genes, including 13 PCGs, 22 tRNA genes, two rRNA genes (16S and 12S) and a non-coding region (D-loop). The positions and sequences of genes were consistent with congeners of Labeoninae. The nucleotide composition of the mitogenome was A (31.5%), T (26.7%), G (15.9%), C (25.8%) and was slightly A + T biased. Phylogenetic analysis conducted using Bayesian Inference method showed that P. lineatus clustered with Pseudogyrincheilus procheilus within the subfamily Labeoninae. The results may provide helpful data for further studies of the evolutionary history of Labeoninae.

‘Henicorhynchus’ thaitui, a new species of cavefish from Central Vietnam (Teleostei, Cyprinidae)

‘Henicorhynchus’thaituisp. nov. is described from a subterranean stream in a karst cave in Phong Nha Ke Bang National Park, Quang Binh Province, Central Vietnam. It differs from all congeners in having a pale pink body in life, smaller eyes with diameter less than the maxillary barbel length, and two pairs of barbels, the maxillary barbel being much longer than the rostral barbel.

A new genus and species of Labeonini (Teleostei: Cyprinidae) from the Pearl River in China

Zuojiangia jingxiensis, both a new genus and species, is described from the Pearl River in China. It is distinguished from all other genera and species of Labeonini by the unique combination of modified oromandibular structures and head skeleton: a well-developed, pendulous, and conspicuously arched rostral fold, with an entirely crenulated margin; prominent papillae densely covering the margin of the rostral fold and anterior part of the lower lip; long postlabial grooves, partitioning the lower lip into three parts; transverse branch of dentary longer than half the length of the longitudinal branch; stubby lateral process present at the anterolateral margin of the longitudinal branch of the dentary, close to the corner; in the upper jaw, the premaxilla bears a triangular ascending process tapering to a point; maxilla exhibits a pair of articular heads at the anterodorsal margin, and a distinct fingerlike descending process posterior to the medial articular head embracing the ascending process of the premaxilla.

Complete mitochondrial genome of two endemic species to China: Discocheilus wui and Discocheilus wuluoheensis (Cypriniformes, cyprinidae)

The genus Discocheilus is endemic to China and only distributed in the Pearl River. The complete mitochondrial genome of Discocheilus wui and Discocheilus wuluoheensis were successfully sequenced in this study. The complete mitochondrial genomes of these two species are 16,589 bp and 16,587 bp in length, respectively. They both consist of 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and a control region. The gene compositions and genome organizations of the two species are similar to other fish. The complete mitochondrial genome sequence of these two species will contribute to reveal the genetic backgrounds for their conservation.