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In the dam discharge season, the supersaturation of total dissolved gas (TDG) in the downstream channel can seriously affect the survival of aquatic organisms. However, few studies have revealed the mechanism by which TDG supersaturation affects the physiology of fish thus far. The present study was conducted to study the mechanism of the effect of TDG supersaturation on Schizothorax davidi, a species that is very sensitive to gas bubble disease. S. davidi was exposed to 116 % TDG supersaturation stress for 24 h. Serum biochemical tests showed that the aspartate aminotransferase and alanine aminotransferase levels after TDG supersaturation exposure were significantly decreased compared to those in the control group, while superoxide dismutase activity was significantly increased. RNA-Seq of gill tissues identified 1890 differentially expressed genes (DEGs), which consisted of 862 upregulated genes and 1028 downregulated genes, in the TDG supersaturation group vs. the control group. Pathway enrichment analysis revealed that the cell cycle, apoptosis and immune signaling pathways were affected by TDG stress. The results of this study may contribute to our understanding of the underlying molecular mechanism of environmental stress in fish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Garra kempi, a small-sized economic fish, is mainly distributed in Tibet of China. In this study, we successfully sequenced the first mitochondrial genome of G. kempi. The mitogenome is 17 104 bp in length, containing 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and 2 control regions (D-loop). Unlike the typical mitochondrial genome organization in vertebrate, the tRNA Pro gene of G. kempi is located between two control regions, and a 246 bp repeat unit is identified in the second control region. In this paper, we utilized 12 protein-coding genes of G. kempi and other 10 closely species to construct the species phylogenetic tree to verify the accuracy of G. kempi.

Hemiculterella sauvagei, a Chinese minnow endemic to the upper Yangtze River, is an important part of the aquatic ecosystem and plays a vital ecological role in maintaining aquatic biodiversity. In this study, we provide the first mitochondrial genome of H. sauvagei. The complete mitochondrial genome of H. sauvagei is 16618 bp in length, containing 13 protein-coding genes, two rRNA genes (12 S and 16 S rRNA), 22 tRNA genes and a non-coding control region (D-loop). The gene nucleotide composition of H. sauvagei is A = 29.9%, T = 27.0%, C = 17.4% and G = 25.6%, with a slight AT bias of 56.9%. The complete mitochondrial genome of H. sauvagei would be useful for further studies on genetic diversity and molecular phylogenetic relationship of the subfamily Cultrinae.

Schizopygopsis pylzovi, an endemic species in the Qinghai-Tibetan Plateau, has a unique ability to adapt to the extreme ecological condition of the plateau. In this study, we successfully sequenced the first mitochondrial genome of S. pylzovi. The mitogenome is 16,814 bp in length, containing 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a control region (D-loop). The overall base composition of the heavy strand (H-strand) is 28.3% A, 26.1% C, 18.6% G, and 27.0% T, with a slight AT bias of 55.3%. Most of the genes are encoded on H-strand, except for eight tRNAs (tRNA(Gln), tRNA(Ala), tRNA(Asn), tRNA(Cys), tRNA(Tyr), tRNA(Ser), tRNA(Glu) and tRNA(Pro)) and ND6 genes.

Schizopygopsis chengi baoxingensis is endemic to the Baoxing River in China and may become an endangered species due to its very narrow habitat and the construction of hydropower dams. In this study, we successfully sequenced the first mitochondrial genome of S. c. baoxingensis. The mitogenome is 16,787 bp in length, containing 13 protein-coding genes, two rRNA genes, 22 tRNA genes and a control region (D-loop). The overall base composition of the H-strand is 28.5% A, 26.2% T, 18.4% C, and 26.9% G, with a slight AT bias of 54.7%. The sequenced mtDNA genome of S. c. baoxingensis is similar in gene arrangement to that of other cyprinidaes except for a 191 bp non-coding region found between tRNA(Thr) and tRNA(Pro).

Xenophysogobio nudicorpa is one member of the genus containing two species only, which is a specialized lineage of gobiobotine fishes. In this study, we provide the first mitochondrial genome of X. nudicorpa. The complete mitochondrial genome of X. nudicorpa is 16,616 bp in length, containing 13 protein-coding genes, two rRNA genes (12 S and 16 S rRNA), 22 tRNA genes and a noncoding control region (D-loop). The gene nucleotide composition of X. nudicorpa is 30.5% A, 26.0% T, 16.8% C and 26.7% G, with a slight AT bias of 56.5%. The complete mitochondrial genome of X. nudicorpa would be useful for further studies on genetic diversity and molecular phylogenetic relationship of the subfamily Gobiobotinae.

The beardless sucking bard, Garra imberba, is an important economic freshwater fish with very limited yield. In this study, we successfully sequenced the first mitochondrial genome of G. imberba by PCR. The mitogenome is 16,600 bp in length, containing 13 protein-coding genes, two rRNA genes, 22 tRNA genes and a control region (D-loop). The overall base composition of the H-strand is 31.5% A, 26.7% T, 16.1% C, and 25.8% G, with a slight AT bias of 58.2%. Most of the genes are encoded on heavy strand, except for eight tRNAs (tRNA(Gln), tRNA(Ala), tRNA(Asn), tRNA(Cys), tRNA(Tyr), tRNA(Ser), tRNA(Glu) and tRNA(Pro)) and ND6 genes.