Electrical stimulation-induced mucus secretion and skin transcriptome responses in Amur catfish (Silurus asotus).

Integrated Analysis of Physiological, Histological, and Transcriptomic Responses to Transport Density in Schizothorax nukiangensis

Integrative study of acute ammonia exposure on the skin of the Striped catfish (Pangasianodon hypophthalmus).

Ammonia can rapidly accumulate in a water body and pose a serious threat to fish health. Striped catfish is a key species in Southeast Asia. Climate change and intensive farming waste pose significant risks of ammonia stress to this species in both natural habitats and farming ponds. As a vital immune-related organ and a significant surface barrier, the fish skin plays a crucial role in defending against ammonia; however, little is known about skin response to acute ammonia exposure. In this study, Striped catfish were exposed to 40 mg L-1 concentration of total ammonia for 24 hr to evaluate skin responses. In general, we found inflammation in the skin. However, the skin tissue showed subtle to no signs of damage, with tissue ammonia concentration accumulating and then decreasing over the challenge duration. Subsequent transcriptomic analysis of skin gene functions suggests that overall ammonia regulation may occur along with specific cellular components. Transmission electron microscopy then revealed accumulated exosome-like vesicles near the epithelial surface of the skin's superficial layer during challenge. Using the established Striped catfish skin epithelial cell line along with an exosome inhibitor, we confirmed the presence of exosomal vesicles and their role in ammonia excretion. In conclusion, while acute ammonia exposure induces inflammation in the Striped catfish skin, active ammonia excretion along with exosomes may alleviate accumulation, thereby maintaining skin tissue integrity. This study explores the Striped catfish skin responses to acute ammonia exposure and highlights the ammonia regulation system that maintains skin integrity.

Integrated Histological and Transcriptomic Characterization of Prolonged Starvation Responses in the Cavefish Triplophysa rosa

Simple Summary Caves are dark, isolated, and food-poor habitats. Animals living in caves must therefore make careful use of limited energy to survive. The cavefish Triplophysa rosa lives in such an environment, but little is known about how it copes when food is unavailable for a long time. In this study, we combined growth measurements, liver and spleen histology, transcriptomic analysis, quantitative reverse transcription PCR, and transmission electron microscopy to examine T. rosa responses to 30, 60, and 90 days of starvation. Prolonged starvation reduced growth and liver reserve indicators and was accompanied by coordinated changes in metabolic gene expression. In the spleen, early immune-related transcriptional changes were followed by greater prominence of melano-macrophage centers, suggesting increasing involvement of cellular clearance and tissue maintenance during prolonged starvation. Autophagy-related gene expression and ultrastructural observations were consistent with increased involvement of intracellular recycling, which may support basic cellular maintenance during prolonged food deprivation. In summary, prolonged starvation in T. rosa involved coordinated temporal changes in metabolism, splenic function, and cellular maintenance. By providing an integrated characterization of prolonged starvation responses in a cave-restricted fish, this study may provide useful physiological information for future conservation and management studies of cave-dwelling species. Abstract 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.

Temporal transcriptomic profiling of channel catfish (Ictalurus punctatus) gills after acute copper exposure reveals suppressed immune gene responsiveness to Flavobacterium covae infection

Copper sulfate pentahydrate (CuSO4·5H2O) is widely used as a chemical prophylactic in aquaculture, yet its immunomodulatory effects in fish remain poorly understood. Here, we investigated how the timing of CuSO4 exposure shapes early immune responses and survival outcomes in channel catfish (Ictalurus punctatus) challenged with Flavobacterium covae. Channel catfish fingerlings were exposed to 2.1 mg/L CuSO4 either immediately before F. covae infection or following a 24 h recovery period, and gill transcriptomes were profiled at 1, 4, and 24 h post-challenge. Infection alone induced strong, time-structured innate and adaptive immune activation, including robust cytokine, chemokine, and pattern-recognition receptor (PRR) signaling. In contrast, Cu exposure followed by immediate infection produced no differentially expressed genes at 1 h and only a minimal response at 4 h, indicating a profound early suppression of host immune activation and a shift toward cellular stress-mitigation pathways. Fish that were treated with Cu followed by a 24 h recovery and then infected with F. covae regained immune responsiveness, displaying coordinated innate and adaptive activation by 4–24 h, consistent with significantly improved survival relative to immediate Cu exposure. Together, these results demonstrate that Cu immunological impact is strongly time-dependent. Acute exposure suppresses early immune readiness and increases susceptibility, whereas a recovery interval restores immune competence and enhances resistance to F. covae. These findings provide mechanistic support for incorporating recovery periods into CuSO4 treatment protocols to avoid unintended immunosuppression in aquaculture.

Transcriptomics and Physiological Analysis Reveal Response Strategies of Sanghuangporus baumii to Aluminum Exposure

Sanghuangporus baumii, a medicinal macrofungus, remains unexplored in its response to aluminum stress, despite the widespread environmental relevance of this metal. This study investigated the dose-dependent effects of Al3+ on mycelial growth and metabolic regulation. Exposure to 1 mM Al3+ moderately stimulated growth (1.11-fold of control) and induced mild oxidative stress, which activated an effective antioxidant response—including increased SOD, CAT, and POD activities and elevated reduced glutathione content—thereby maintaining redox balance and increasing soluble sugar content. In contrast, 10 mM Al3+ led to pronounced intracellular Al3+ accumulation, severe growth inhibition, and marked oxidative damage, accompanied by impairment of the antioxidant system, yet a marked increase in total triterpenoid content (1.72-fold). Transcriptomic analysis identified 642 and 3019 differentially expressed genes (DEGs) in the 1 and 10 mM Al3+ treatments, respectively. KEGG enrichment analysis revealed concentration-dependent alterations in pathways related to peroxisome function, glutathione metabolism, starch and sucrose metabolism, and terpenoid backbone biosynthesis. Collectively, these findings suggest that Al3+ modulates S. baumii growth and metabolism in a dose-dependent manner, with redox remodeling as a potential mechanism, offering novel insights into fungal metal adaptation and the targeted modulation of medicinal metabolite production.

Gill epithelial responses of Cyprinus carpio Linnaeus, 1758 as sensitive histological biomarkers of sublethal anthropogenic stress in the Ile River (Kazakhstan)

Abstract The gills of teleost fish are multifunctional organs involved in respiration, osmoregulation, and immune defense, and are highly sensitive to environmental stressors. This study evaluated the histological and ultrastructural condition of the gill epithelium of common carp (Cyprinus carpio Linnaeus, 1758) inhabiting the middle reaches of the Ile River (Kazakhstan) under chronic anthropogenic pressure. Although hydrochemical parameters remained within permissible limits for fishery waters, all examined specimens (n = 10) exhibited pronounced structural alterations. Histological analysis revealed edema, epithelial hyperplasia, lamellar fusion, necrosis, and desquamation, indicating substantial impairment of gill integrity. Ultrastructural examination demonstrated advanced developmental stages of rodlet cells, mast cell degranulation, and increased activity of mucous and chloride cells, accompanied by mitochondrial alterations and autophagosome formation. Alongside destructive changes, moderate compensatory reactions were observed, reflecting tissue-level adaptation to prolonged environmental stress. These findings demonstrate that gill histopathology provides a sensitive tool for detecting sublethal effects of chronic anthropogenic impact, even when conventional hydrochemical indicators suggest acceptable water quality. The results support the use of cellular and tissue-level biomarkers in freshwater environmental monitoring programs.