Aeromonas veronii is widespread in aquatic environments and is capable of infecting various aquatic organisms. A. veronii infection is lethal for Chinese soft-shelled turtles (Trionyx sinensis, CSST). We isolated a gram-negative bacterium from the liver of diseased CSSTs, which was named XC-1908. This isolate was identified as A. veronii based on its morphological and biochemical characteristics, and 16S rRNA gene sequence analysis. A. veronii was pathogenic for CSSTs with an LD₅₀ of 4.17 × 10⁵ CFU/g. The symptoms of CSSTs artificially infected with isolate XC-1908 were consistent with those of the naturally infected CSSTs. The levels of total protein, albumin, and white globule in the serum samples of the diseased turtles were decreased, whereas those of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase were elevated. Moreover, the diseased CSSTs exhibited the following histopathological changes: the liver contained numerous melanomacrophage centers, renal glomerulus were edematous, intestinal villi were shed, and in oocytes, the number of vacuoles increased and red-rounded particles were observed. Antibiotic sensitivity tests revealed that the bacterium was sensitive to ceftriaxone, doxycycline, florfenicol, cefradine, and gentamicin, and resistant to sulfanilamide, carbenicillin, benzathine, clindamycin, erythromycin, and streptomycin. This study provides control strategies to prevent outbreaks of A. veronii infection in CSSTs.

In recent years, the potent influence of tocotrienol (T3) on diminishing blood glucose and lipid concentrations in both Mus musculus (rats) and Homo sapiens (humans) has been established. However, the comprehensive exploration of tocotrienol’s hypolipidemic impact and the corresponding mechanisms in aquatic species remains inadequate. In this study, we established a zebrafish model of a type 2 diabetes mellitus (T2DM) model through high-fat diet administration to zebrafish. In the T2DM zebrafish, the thickness of ocular vascular walls significantly increased compared to the control group, which was mitigated after treatment with T3. Additionally, our findings demonstrate the regulatory effect of T3 on lipid metabolism, leading to the reduced synthesis and storage of adipose tissue in zebrafish. We validated the expression patterns of genes relevant to these processes using RT-qPCR. In the T2DM model, there was an almost two-fold upregulation in pparγ and cyp7a1 mRNA levels, coupled with a significant downregulation in cpt1a mRNA (p < 0.01) compared to the control group. The ELISA revealed that the protein expression levels of Pparγ and Rxrα exhibited a two-fold elevation in the T2DM group relative to the control. In the T3-treated group, Pparγ and Rxrα protein expression levels consistently exhibited a two-fold decrease compared to the model group. Lipid metabolomics showed that T3 could affect the metabolic pathways of zebrafish lipid regulation, including lipid synthesis and decomposition. We provided experimental evidence that T3 could mitigate lipid accumulation in our zebrafish T2DM model. Elucidating the lipid-lowering effects of T3 could help to minimize the detrimental impacts of overfeeding in aquaculture.

Water alkalinization is a critical global stressor for freshwater fish, yet the systemic patterns of multi-organ responses and injury remain insufficiently understood. This study integrates histopathology, biochemistry, and multi-organ transcriptomics to provide an integrated, time-resolved assessment of stress responses in European perch (Perca fluviatilis) exposed to acute alkaline stress (20 mmol/L). The analysis indicated that alkaline stress initially causes structural disturbance of gill tissue (lamellar fusion, necrosis) within 96 h, associated with impaired osmoregulatory functions. This primary dysfunction was followed by progressive hepatic impairment, characterized by uncontrolled oxidative stress (elevated levels in Malondialdehyde, MDA) and widespread hepatocyte necrosis. Transcriptomic analysis identified extensive transcriptional shifts associated with these alterations: large-scale differential expression in the liver (3629 Differentially Expressed Genes, DEGs) and kidney (478 DEGs). Notably, the liver exhibited a stress-responsive transcriptional profile involving activation of the HIF-1 signaling pathway and mobilizing protein quality control systems (e.g., ‘Proteasome,’ ‘Lysosome’) consistent with mitigation of proteotoxic stress. This compensatory response appeared insufficient to prevent severe metabolic disruption and cellular injury. This study presents a time-associated sequence of organ-specific stress responses under acute alkalinity, identifying candidate stress-associated genes (slc7a11, egln3, klhl38b) as potential targets for future functional studies and breeding alkali-tolerant strains.

The high mortality associated with largemouth bass ranavirus (LMBRaV) disease requires rapid and sensitive diagnosis methods to prevent virus spread and subsequent outbreak. The recombinase polymerase amplification combined with the CRISPR/Cas12a system (RPA-CRISPR/Cas12a) assay and RPA-CRISPR/Cas12a, coupled with lateral flow dipstick (RPA-CRISPR/Cas12a-LFD) assay for LMBRaV, were established in this study for low viral load surveillance. The major capsid protein (mcp) gene is highly conserved and is widely used as the target sequence in LMBRaV detection. First, based on the mcp gene sequence of LMBRaV, three candidate crRNAs were designed. Among them, the crRNA-2, which exhibited the highest cleavage activity, was selected through dual evaluation of fluorescence signal intensity and LFD color development. Then, the key reaction conditions for both assays were optimized as follows: LbCas12a protein concentration of 150 nM, crRNA-2 concentration of 200 nM, and ssDNA reporters’ concentration of 200 nM. Moreover, specificity evaluation showed that both combined assays specifically recognized LMBRaV, with no cross-reactivity detected against other aquatic pathogens, such as CyHV-2, GSIV, ISKNV, WSSV, GCRV II or CrERV. The detection limit was 1 copy/μL of DNA sample for both RPA-CRISPR/Cas12a and RPA-CRISPR/Cas12a-LFD assays. Finally, validation using 24 clinical samples (16 positive, eight negative) showed that both LMBRaV RPA-CRISPR/Cas12a assays achieved 100% detection rate, whereas conventional PCR detected 13 positive samples (detection rate 81.26%). ddPCR served as the reference method for clinical validation. Therefore, the LMBRaV RPA-CRISPR/Cas12a assay and the RPA-CRISPR/Cas12a-LFD assay provide sensitive, specific, and easy-to-operate methods for the rapid detection of LMBRaV.

To understand the adaptive evolution of endangered plateau freshwater fishes to environmental stress and to better explore the underlying mechanisms in Aspiorhynchus laticeps—a critically endangered fish endemic to the Tarim Basin, Xinjiang, China—a combination of ecological experiments and transcriptome sequencing (RNA-seq) technology was used to study the differences in gene expression patterns among individuals under different salinities and flow conditions. This experiment included four treatment groups (CON, H-SA-S, L-SA, L-SA-S). A. laticeps specimens with an average weight of 2.92 ± 0.62 g and a body length of 58.22 ± 5.10 mm were selected, with three biological replicates for a 96 h combined stress treatment. Moreover, the relationships between these differences and the aquatic environment were analyzed. A total of 1847 differentially expressed genes (DEGs), including 935 upregulated genes and 912 downregulated genes, were identified under different aquatic environment stress modes. GO and KEGG enrichment analyses revealed that TNF signal transduction, the NF-κB pathway, and metabolic regulation were significantly enriched among the DEGs (p < 0.05). High salinity–alkali stress significantly activates the TNF/NF-κB pathway, regulates MST1, LOC107702867, LOC113110979 and other genes to enhance the body’s resistance; water flow changes mainly regulate energy metabolism through genes such as NEHOM01_1600 and gptl. These findings provide an important scientific basis for the ecological adaptability, protection, and proliferation of endemic and endangered fish in China, as well as for germplasm innovation to address ecological deterioration in plateau fishes in alpine and arid areas. This study provides a molecular-level theoretical foundation for artificial habitat regulation and the conservation of endangered Aspiorhynchus laticeps populations in the Tarim River.