Search

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Brachymystax tsinlingensis Li is a threatened fish species endemic to China. With the problems of environmental factors and seeding breeding diseases, it is important to further improve the efficiency of seeding breeding and the basis of resource protection. This study investigated the acute toxicity of copper, zinc and methylene blue (MB) on hatching, survival, morphology, heart rate (HR) and stress behaviour of B. tsinlingensis. Eggs (diameter: 3.86 ± 0.07 mm, weight: 0.032 ± 0.004 g) of B. tsinlingensis were selected randomly from artificial propagation and developed from eye‐pigmentation‐stage embryos to yolk‐sac stage larvae (length: 12.40 ± 0.02 mm, weight: 0.03 ± 0.001 g) and exposed to different concentrations of Cu, Zn and MB for 144 h in a series of semi‐static toxicity tests. The acute toxicity tests indicated that the 96‐h median lethal concentration (LC50) values of the embryos and larvae were 1.71 and 0.22 mg l−1 for copper and 2.57 and 2.72 mg l−1 for zinc, respectively, whereas the MB LC50 after 144‐h exposure for embryos and larvae were 67.88 and 17.81 mg l−1, respectively. The safe concentrations of copper, zinc and MB were 0.17, 0.77 and 6.79 mg l−1 for embryos and 0.03, 0.03 and 1.78 mg l−1 for larvae, respectively. Copper, zinc and MB treatments with concentrations greater than 1.60, 2.00 and 60.00 mg l−1, respectively, led to a significantly low hatching rate and significantly high embryo mortality (P < 0.05), and copper and MB treatments with concentrations greater than 0.2 and 20 mg l−1 led to significantly high larvae mortality (P < 0.05). Exposure to copper, zinc and MB resulted in developmental defects, including spinal curvature, tail deformity, vascular system anomalies and discolouration. Moreover, copper exposure significantly reduced the HR of larvae (P < 0.05). The embryos exhibited an obvious change in behaviour, converting from the normal behaviour of emerging from the membrane head first to emerging tail first, with probabilities of 34.82%, 14.81% and 49.07% under copper, zinc and MB treatments, respectively. The results demonstrated that the sensitivity of yolk‐sac larvae to copper and MB was significantly higher than that of embryos (P < 0.05) and that B. tsinlingensis embryos or larvae might be more resistant to copper, zinc and MB than other members of the Salmonidae family, which benefits their resource protection and restoration. [ABSTRACT FROM AUTHOR]

Brachymystax tsinlingensis is a unique cold water fish locally distributed in China, belonging to Salmoniformes, Salmonidae and Brachymystax. It is mainly distributed in the mountain streams of the Qinling mountain range, including the Shitouhe River in the northern foothills, the Heihe River in the eastern foothills and the Taibaihe and Xushuihe rivers in the southern foothills. B. tsinlingensis has high sensitivity owing to demanding natural habitat conditions and special biological properties. In the past few decades, environmental pollution, a variety of human-caused threats, and reduced resources has caused drastic declines in the wild populations of B. tsinlingensis. In 1998, the species was listed as a second-class state-protected wild animal in the China Red Data Book of Endangered Animals. Due to environmental disruption and human impacts, wild numbers of this species have declined quickly. In China, researchers have focused on B. tsinlingensis conservation. Artificial propagation is one of the most effective methods to restore the natural populations of B. tsinlingensis. In recent years, initial breakthroughs in artificial propagation techniques have aided this species, but the fry survival rate remains relatively low. During artificial breeding experiments, we identified the light environment and substrate conditions that are important factors affecting the survival rate of fry. Fry behavioral selection of light and substrate characteristics was highly significant. The aim of this study was to identify the habitat preferences and associated behavior of B. tsinlingensis. Behavioral experiments were conducted on the progeny of B. tsinlingensis in response to the light environment and substrate color. In this study, we randomly selected healthy juveniles from the same offspring batch obtained through artificial propagation as the experimental fish. The fry total length ranged from 2.23–4.57 cm, with an average of (3.31±0.67) cm. Fry weight ranged from 0.21–0.77 g, with an average weight of (0.42±0.18) g. The experimental fish were not fed 2 h before initiating the experiment. We undertook a combination of individual tests and population tests to investigate three different behavioral selection experiments on juveniles: substrate color preference with the substrate colors of black, white, and blue; light intensity preference with the light intensity of dark (from 1 lx to 5 lx), transition area (from 5 lx to 10 lx), and illuminated area (from 10 lx to 25 lx); light color preference with the light colors of yellow, red, green, or blue. The statistical analysis of the percentage of residence time and the distribution number of experimental fish in each area, enabled analysis using a selective index for the different light intensities, different light colors, and different substrate colors. All analyses used Excel 2016 and SPSS (V 25.0) software, and the statistical values were expressed as the mean ± standard deviation. The results showed that the percentage of time the individuals resided in the black substrate area was significantly higher than that in the white or blue area (P < 0.05). The percentage of the population distributed in the black substrate area was also significantly higher than that in the white or blue area (P < 0.05). Therefore, the majority of the fish preferred the black substrate. The fish swam slowly through the black substrate area in the substrate color experiments. Secondly, in the phototropism experiment, there was no significant variation in the duration of each individual in the three light intensity areas (P > 0.05), and the percentage of the population in the illuminated area was significantly lower than that in the dark area and the transition area (P < 0.05). There was no significant difference between the dark area and the transition area. The population had a negative tendency to the illuminated area, and fish were observed clustering in the dark area and the transition area. Moreover, individuals did not differ significantly in the percent of time they resided in the four light color areas (P > 0.05). However, the percentage of individuals in the green light area was significantly lower than that in other areas (P < 0.05). The population had a negative tendency towards the green light, and fish displayed sudden acceleration when swimming through the green area in the light color selection experiment. Consequently, the population had a more pronounced avoidance than the individual experiments, this might be related to the mutual transmission of information when residing in clusters, and the speed of information transmission in groups encouraging individuals to avoid the adverse environment. Juvenile B. tsinlingensis preferred a black substrate, avoided green light, and their optimum illumination range was 1–10 lx. The results provide scientific guidance for environmental fry rearing and releasing of B. tsinlingensis.

Brachymystax tsinlingensis Li, 1966 is an endangered freshwater fish with economic, ecological, and scientific values. Study of the genome of B. tsinlingensis might be particularly insightful given that this is the only Brachymystax species with genome. We present a high-quality chromosome-level genome assembly and protein-coding gene annotation for B. tsinlingensis with Illumina short reads, Nanopore long reads, Hi-C sequencing reads, and RNA-seq reads from 5 tissues/organs. The final chromosome-level genome size is 2,031,709,341 bp with 40 chromosomes. We found that the salmonids have a unique GC content and codon usage, have a slower evolutionary rate, and possess specific positively selected genes. We also confirmed the salmonids have undergone a whole-genome duplication event and a burst of transposon-mediated repeat expansion, and lost HoxAbb Hox cluster, highly expressed genes in muscle may partially explain the migratory habits of B. tsinlingensis. The high-quality B. tsinlingensis assembled genome could provide a valuable reference for the study of other salmonids as well as aid the conservation of this endangered species. [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 tsinlingensis Li, 1966 is an endangered freshwater fish with economic, ecological, and scientific values. Study of the genome of B. tsinlingensis might be particularly insightful given that this is the only Brachymystax species with genome. We present a high-quality chromosome-level genome assembly and protein-coding gene annotation for B. tsinlingensis with Illumina short reads, Nanopore long reads, Hi-C sequencing reads, and RNA-seq reads from 5 tissues/organs. The final chromosome-level genome size is 2,031,709,341 bp with 40 chromosomes. We found that the salmonids have a unique GC content and codon usage, have a slower evolutionary rate, and possess specific positively selected genes. We also confirmed the salmonids have undergone a whole-genome duplication event and a burst of transposon-mediated repeat expansion, and lost HoxAbβ Hox cluster, highly expressed genes in muscle may partially explain the migratory habits of B. tsinlingensis. The high-quality B. tsinlingensis assembled genome could provide a valuable reference for the study of other salmonids as well as aid the conservation of this endangered species., (© Crown copyright 2022.)