Search Results (4)

Temperature is a critical environmental factor that influences the growth, development, metabolism, and overall physiological performance of fish. Eleutheronema tetradactylum is an economically significant fish species; however, its molecular mechanism’s response to long-term cold stress is still unclear. In this study, we investigated the physiological responses of the liver in E. tetradactylum exposed to a constant temperature of 18 °C for durations of both 7 and 14 days, utilizing liquid chromatography–mass spectrometry (LC-MS), metabolomics, and conventional biochemical assays. The antioxidant status, liver histology, and metabolite profiles were examined at different time points. Our results revealed that, following sustained cold exposure, the activities of key antioxidant enzymes—superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)—initially increased and then decreased. Additionally, levels of malondialdehyde (MDA), a marker of oxidative damage, significantly elevated after 7 and 14 days of cold stress. Histopathological examination of liver tissues showed varying degrees of vacuolation and nuclear atrophy in hepatocytes, indicating oxidative damage. Metabolomic profiling identified 87 and 116 differentially expressed metabolites in the liver on days 7 and 14, respectively. Pathway enrichment analysis revealed significant alterations in pathways related to carbohydrate digestion and absorption, glutathione metabolism, and glycerolipid metabolism. These findings suggest that mechanisms regulating cell membrane fluidity, energy metabolism, autophagy, and antioxidant defense are crucial for the adaptation of E. tetradactylum to cold stress. Overall, this study provides valuable insights into the molecular and physiological adaptations of E. tetradactylum to low temperature, highlighting the activation of protective antioxidant responses and modifications of metabolic pathways in the liver. Full article

Migratory fish often encounter hypoxic zones during migration, which can lead to varying degrees of hypoxic stress. This issue has become increasingly severe due to human activities and climate change, which have resulted in the expansion of hypoxic zones in aquatic environments. However, there is limited research on how these species respond to hypoxic stress and subsequent recovery. In this study, we used Eleutheronema tetradactylum, a well-recognized migratory and economically valuable fish species, as a model organism. Histological analysis revealed extensive neuronal damage during hypoxia exposure, with limited recovery observed even after 12 h of reoxygenation. Differential gene expression analysis highlighted progressive alterations in genes associated with stress response, neuroactive ligand interactions, and cellular repair mechanisms. Time-series analysis of differentially expressed genes (DEGs) identified critical expression profiles throughout the hypoxia-recovery process and revealed hub genes for each stage. Furthermore, dynamic changes in miRNA expression and proteomic profiles indicated active regulation of several key biological pathways, including MAPK, HIF-1, and ECM-receptor interactions. Through miRNA-mRNA-protein correlation analysis, we propose a model that predicts key regulatory pathways and critical miRNA-mRNA-protein interactions across the various stages of hypoxia-recovery in the brain of E. tetradactylum. This study presents the first integrated analysis of miRNA, mRNA, and protein throughout the entire hypoxia-recovery process in fish brains. The molecular interactions and regulatory pathways identified in this model could serve as valuable biomarkers for future research on hypoxia-recovery mechanisms in fish. Full article

The effects of Bacillus coagulans (BC) T-21 on growth performance, intestinal digestive enzyme activity, intestinal morphology, and intestinal microbiota of juvenile fourfinger threadfin (Eleutheronema tetradactylum) were investigated in the present study. Healthy juvenile E. tetradactylum with an initial body weight of 4.2 ± 0.5 g were fed a basal diet sprayed with 1 × 10⁸ cfu/g B. coagulans for eight weeks, and the growth parameters, intestinal digestive enzyme activities, HE-stained intestinal sections, and intestinal microbiota of the juvenile fish were measured. The differences in the feed conversion ratio between the experimental and control groups (fed the basal diet) were extremely significant (p < 0.01), whereas the differences in weight gain rate, specific growth rate, survival rate, and condition factor were significant (p < 0.05). In the experimental group, trypsin and amylase activities decreased significantly, whereas there were no significant differences in lipase activity between the two groups. Compared to the control group, the height of the intestinal villi was greater. No significant differences were observed in the diversity of intestinal microbiota and microbial species at the genus level (p > 0.05). Based on the function prediction analysis, the count values for the glycan biosynthesis, metabolism, and digestive system pathways were significantly increased in the experimental group (p < 0.05). However, there were no significant differences in the counts of other functional pathways (p > 0.05). These results indicate that dietary B. coagulans supplementation is effective in promoting the growth performance and intestinal health of juvenile E. tetradactylum. Full article

Streptococcus iniae is a Gram-positive bacterium and is considered a harmful aquaculture pathogen worldwide. In this study, S. iniae strains were isolated from East Asian fourfinger threadfin fish (Eleutheronema tetradactylum) reared on a farm in Taiwan. A transcriptome analysis of the head kidney and spleen was performed in the fourfinger threadfin fish 1 day after infection using the Illumina HiSeq™ 4000 platform for RNA-seq to demonstrate the host immune mechanism against S. iniae. A total of 7333 genes based on the KEGG database were obtained after the de novo assembly of transcripts and functional annotations. Differentially expressed genes (DEGs) (2-fold difference) were calculated by comparing the S. iniae infection and phosphate-buffered saline control group gene expression levels in each tissue sample. We identified 1584 and 1981 differentially expressed genes in the head kidney and spleen, respectively. Based on Venn diagrams, 769 DEGs were commonly identified in both the head kidney and spleen, and 815 and 1212 DEGs were specific to the head kidney and spleen, respectively. The head-kidney-specific DEGs were enriched in ribosome biogenesis. The spleen-specific and common DEGs were found to be significantly enriched in immune-related pathways such as phagosome, Th1, and Th2 cell differentiation; complement and coagulation cascades; hematopoietic cell lineage; antigen processing and presentation; and cytokine–cytokine receptor interactions, based on the KEGG database. These pathways contribute to immune responses against S. iniae infection. Inflammatory cytokines (IL-1β, IL-6, IL-11, IL-12, IL-35, and TNF) and chemokines (CXCL8 and CXCL13) were upregulated in the head kidney and spleen. Neutrophil-related genes, including phagosomes, were upregulated post-infection in the spleen. Our results could offer a strategy for the treatment and prevention of S. iniae infection in fourfinger threadfin fish. Full article