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Silurus lanzhouensis is a large endemic fish exclusively found in the middle and upper reaches of China's Yellow River, with a restricted distribution range and a small population size and is listed as an endangered species. To investigate the potential genetic factors contributing to the observed decrease in the population of S. lanzhouensis, we have successfully assembled the first chromosome-level genome of S. lanzhouensis. This genome comprises a total of 30 chromosomes, with a size of 794.43 Mb, and 23,093 protein-coding genes. Comparative genomics analysis reveals that the genetic relationship between S. lanzhouensis and S. meridionalis Chen is the closest, and their common ancestor experienced two rounds of whole genome duplication (WGD) before diverging. Notably, amino acid metabolism-related pathways are enriched in the unique S. lanzhouensis gene family. In addition, we observed that the chemokine receptor and scavenger receptor gene families contracted in S. lanzhouensis, which may be associated with its diminished immune response. Our research findings provide valuable insights into the endangered mechanism of S. lanzhouensis and enhance our understanding of the evolution of Siluriformes fish. [ABSTRACT FROM AUTHOR]

Brachymystax tsinlingensis Li, distributed scatteredly in Qinling Mountains of China, is an ideal material for studies of conservation and phylogeography. In the present study, the genetic variations and phylogeographical patterns of B. tsinlingensis collecting from the Yangtze River (n = 30) and the Yellow River (n = 70) were compared based on 1082-1163 bp control region with partial tRNA and 912 bp cyt b partial sequence of mtDNA. Analysis of variance indicated that a high proportion of the total genetic variance (96.03%) was distributed among populations, supporting strong geographic structuring of mtDNA polymorphism. Ten haplotypes were assigned to two clades that were related to geographic regions. No haplotype shared between geographic populations from the Yangtze River and the Yellow River, and two clades related to geographic regions can be clearly found from phylogenetic analysis by Bayesian approach, one from individuals in the Yangtze River and the other from individuals in the Yellow River, which probably indicated artificial carrying not happened historically. The mitochondrial results revealed an obvious differentiation of genetic structure of B. tsinlingensis between populations of Yellow River and Yangtze River, and the estimated diverge time around 0.20 MY. It was suggested that each of the two evolutionarily distinct groups of B. tsinlingensis should be protected and crossing individuals between two river systems should be avoided for conservation purpose. [ABSTRACT FROM AUTHOR]

Brachymystax lenok tsinlingensis is an endangered freshwater fish which is endemic to part of China. To investigate its genetic diversity and population structure, mitochondrial cytochrome b gene and D-loop control region were used to analyze samples from five different locations. Fifteen haplotypes were identified; however, no shared haplotypes were observed among different streams. The analysis of molecular variance (AMOVA) results indicated that 77.38% of total variation was attributed to differentiation between populations, whereas 22.62% from variation within populations. The high genetic differentiation among the populations would provide useful information for building natural reserves and artificially releasing cultured juveniles in the future. [ABSTRACT FROM AUTHOR]

Brachymystax lenok tsinlingensis is an endangered freshwater fish which is endemic to part of China. To investigate its genetic diversity and population structure, mitochondrial cytochrome b gene and D-loop control region were used to analyze samples from five different locations. Fifteen haplotypes were identified; however, no shared haplotypes were observed among different streams. The analysis of molecular variance (AMOVA) results indicated that 77.38% of total variation was attributed to differentiation between populations, whereas 22.62% from variation within populations. The high genetic differentiation among the populations would provide useful information for building natural reserves and artificially releasing cultured juveniles in the future., Competing Interests: The authors report no conflict of interest., (© 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)