This study aimed to investigate the histological features of the intestine of Acipenser dabryanus from 1 to 15 months of age via HE staining, AB-PAS staining, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The intestine of A. dabryanus comprises the duodenum, spiral valve intestine, and rectum. With age, the duodenal diameter and mucosal/muscular layer thickness increased, the spiral valve intestine’s mucosa thickened and protrusions formed networks, and the rectal diameter enlarged. Abundant mucus cells, predominantly type IV, were found in the duodenum, spiral valve intestine, and rectum of A. dabryanus at different ages by AB-PAS staining. Our study confirmed the presence of ciliated columnar cells (with ‘9 + 2’ cilia structure) with orderly arranged cilia at their apices in the mucosal epithelium of A. dabryanus’s duodenum, spiral valve intestine, and rectum for the first time, as shown by SEM and TEM. The presence of spiral valves and ciliated columnar cells in the intestinal structure of A. dabryanus highlights its unique features and evolutionary significance. These findings highlight A. dabryanus’s unique intestinal features and evolutionary significance, providing a basis for scientific feed formulation and enhancing our understanding of the histological characteristics of the sturgeon intestine.

This study investigated muscle quality differences between wild-type (WT) and yellow-mutant (YM) Triplophysa siluroides. Texture analysis showed WT T. siluroides had significantly greater hardness, gumminess, and resilience than YM. Histological and biochemical analyses ruled out myofiber diameter/density as drivers, instead identifying reduced collagen in YM as key, as confirmed by Picrosirius red staining, collagen quantification, and transmission electron microscopy. Transcriptomic and proteomic analyses revealed that TGF-β/BMP pathway suppression in YM resulted in downregulation of core molecules (e.g., BMP2 and SMAD1), collagen-related genes (e.g., COL1A1a and COL1A1b), and ECM-related genes (e.g., TNC and FN1), potentially influencing collagen synthesis and ECM homeostasis. Notably, melanin gene TYRP1 was also downregulated in YM T. siluroides, suggesting a link between pathway suppression, muscle quality alteration, and body pigmentation. The potential role of the BMP2-SMAD1-TYRP1 axis in the association between muscle quality and body colour provides novel mechanistic insights, offering molecular targets for the breeding of T. siluroides with superior commercial traits.

The study aims to construct a single-cell atlas of the gill of yellow catfish Tachysurus vachellii (Richardson, 1846) and to explore the response patterns of gill cells under acute hypoxia stress. In this study, we performed single-cell sequencing and histological observations of T. vachellii, gills. A total of 37,090 cells and 33 cell clusters were collected, and 18 cell types were identified. We found that three clusters of NECs have different functions, and in the gene enrichment results of MC differential expression during hypoxia and reoxygenation, we observed that MC may be regulated by non-neuronal neurotransmitter signals during hypoxia stress. There are also differences in cellular communication and transcription factors between different NECs and MCs. After acute hypoxia, the expression of tjp2 and lima1 in PVC was significantly upregulated, and there was no significant change in the number of erythrocytes. Observation of the organizational structure revealed that muscle, skin, and gill tissues were affected after hypoxia, resulting in changes in the flattened epithelial cells and MRC ultrastructure of the gill. This study provides single-cell atlas and data support for the acute hypoxia and reoxygenation model of fish gill tissue.

Aeromonas veronii is a major pathogen threatening freshwater aquaculture, yet the molecular mechanisms of Pelteobagrus vachellii’s immune response to this infection remain unclear. This study integrated histopathology, mRNA-seq and small RNA-seq to investigate P. vachellii’s response to A. veronii at 48 h post-challenge. Histopathologically, infection induced gill epithelial detachment, hepatocyte swelling with cytoplasmic vacuolation, and melanomacrophage centers (MMCs) in the mid-kidney (histological assessment of the head kidney was not feasible due to sampling limitations associated with its small size). Transcriptomic analysis identified 1210 differentially expressed genes (DEGs) in the head kidney (819 downregulated, 391 upregulated), significantly enriched in 11 immune pathways (e.g., NF-κB, Th17 cell differentiation, Complement and coagulation cascades), with key immune genes (e.g., IL-1β, TCRα, CCL4) upregulated. Gene Set Enrichment Analysis (GSEA) revealed activation of the proteasome, ribosome and oxidative phosphorylation pathways, and suppression of the autophagy-animal, FoxO and AMPK pathways. Small RNA-seq identified 544 known and 958 novel miRNAs in the head kidney, with 42 downregulated and 36 upregulated differentially expressed miRNAs (DE miRNAs). The miRNA-mRNA network showed that DE miRNAs (e.g., miR-101-y/z, miR-132-z, miR-3167-y) negatively regulated immune-related target genes (IL-1R1, IRF4, IκBα) in core immune pathways. Collectively, this study clarifies the pathological and miRNA-mRNA regulatory modules of P. vachellii head kidney against A. veronii infection, providing valuable information that enables the further analyses of the defense mechanisms of P. vachellii against A. veronii infection.

Food scarcity is a major ecological challenge for cavefish; however, their coordinated physiological and molecular responses to prolonged starvation remain poorly understood. Here, we characterized the responses of Triplophysa rosa to 30, 60, and 90 days of food deprivation under controlled laboratory conditions by integrating growth measurements, histology, transcriptomics, quantitative reverse transcription PCR, and transmission electron microscopy. Starvation inhibited growth, reduced the condition factor and hepatosomatic index, and induced hepatocyte shrinkage, consistent with mobilization of hepatic energy reserves. Liver genes with declining temporal expression were enriched mainly in lipid biosynthesis, cholesterol metabolism, ribosomal function, and cell-cycle pathways, consistent with reduced biosynthetic activity. In the spleen, immune-related transcription increased during early starvation and declined at later stages, while the greater prominence of melano-macrophage centers was consistent with greater involvement of cellular clearance and tissue maintenance during prolonged starvation. Prolonged starvation also increased the expression of autophagy-related genes in the liver and spleen, and autophagy-related structures became more prominent in representative transmission electron microscopy images, consistent with increased involvement of intracellular recycling. Together, these findings reveal a coordinated temporal response involving metabolic adjustment, stage-dependent reorganization of splenic immune-related processes, and autophagy-associated cellular maintenance in T. rosa. This integrated approach improves our understanding of physiological maintenance during sustained nutrient limitation in cave-restricted fish.

Percocypris pingi is an endangered protected fish species in China. Its albino variants exhibit growth retardation and physiological abnormalities. Understanding its albinism mechanism holds significant scientific importance for molecular breeding programs and disease model development. This study integrated transcriptomic and proteomic analyses, combined with histopathological and molecular biological techniques, to systematically compare molecular differences in skin tissues between albino and wild-type P. pingi, with a focus on elucidating the multidimensional regulatory mechanisms underlying skin albinism. Our findings suggest that albinism in P. pingi is synergistically driven by hyperactivation of ubiquitin-mediated proteolysis (which suppressed TYR/TYRP1 enzymatic activity and disrupted the pH homeostasis of melanosomes), and inhibition of calcium signaling (which impeded melanin transport). This discovery provides novel insights into the mechanisms of pigment loss in fish species and offers a valuable reference for molecular breeding of endangered species as well as research on pigmentation-related disorders.