Fish Physiology and Biochemistry最新文献

Taurine is considered a conditionally essential nutrient in several teleost fish; however, its metabolic role remains poorly understood in native South American species. In the present study, taurine metabolism was investigated in four aquaculture-relevant freshwater species: Pseudoplatystoma corruscans (spotted catfish), Piaractus mesopotamicus (pacu), Colossoma macropomum (tambaqui), and Arapaima gigas (pirarucu). Individuals were sampled from natural environments during spring and autumn, as well as from commercial aquaculture systems. The condition factor (K), gonadosomatic index (GSI), and hepatosomatic index (HSI) were calculated. Taurine concentrations were quantified in red muscle (RMtau), gonads (Gtau), and stomach contents (Dtau). Additionally, hepatic activities of cystathionine β-synthase (CBS) and cysteine sulphinic acid decarboxylase (CSD) were assessed. Path analysis revealed significant associations between dietary taurine intake, enzyme activity, and tissue taurine deposition. Principal component analysis showed that A. gigas exhibited distinct physiological and metabolic profiles compared to the other species. Taurine concentrations varied according to species, tissue, and origin (wild vs. farmed). Notably, higher taurine levels were detected in wild individuals of P. mesopotamicus and P. corruscans, while farmed C. macropomum and A. gigas exhibited elevated concentrations in specific tissues, such as stomach contents. These findings underscore the species-specific and environmentally modulated nature of taurine metabolism in Neotropical fishes and suggest potential conditional essentiality in A. gigas.

S100A10 protein, a member of S100 protein family, has been extensively studied in mammalian models. In fish species, evolution of S100 proteins including S100A10 has been clarified, revealing that two paralogous genes, S100A10a and S100A10b, arose in teleosts through the fish-specific whole-genome duplication event. However, the functional roles of fish S100A10 genes remain largely uncharacterized. In the present study, we identified two S100A10 homologs in grass carp, designated gcS100A10a and gcS100A10b, and demonstrated that their mRNA is highly expressed in grass carp skin and strongly upregulated after skin trauma by real-time quantitative PCR. Using the fish epithelial cell line, Epithelioma papulosum cyprini (EPC) cells, as a model, we showed that overexpression of gcS100A10a or gcS100A10b enhances cell viability, increases expression of proliferating cell nuclear antigen (PCNA), and promotes DNA synthesis, thereby demonstrating their capacity to stimulate cell proliferation. Flow cytometric analysis further uncovered that both proteins accelerate EPC cell cycle progression by promoting transition into the S and G2/M phases. Additionally, gcS100A10a and gcS100A10b significantly elevate EPC cell migration and this elevation is attenuated by a broad-spectrum matrix metalloproteinase (MMP) inhibitor, GM6001, suggesting involvement of MMP activity in this process. This suggestion is strongly supported by findings that overexpression of gcS100A10a or gcS100A10b increases extracellular MMP activity and decreases intracellular MMP accumulation although ‌MMP-2/MMP-9 mRNA levels remain unchanged. Collectively, these results demonstrate the positive regulation of gcS100A10a and gcS100A10b on fish epithelial cell proliferation and migration, together with their high and injury-inducible expression in grass carp skin, indicating their possible involvement in fish skin wound healing.

Myo-inositol oxygenase (MIOX) plays an essential role in metabolic pathways and cell processes, controls oxidative stress response mechanisms, and balances osmotic stress in aquatic organisms. Molecular docking and structural analysis of the MIOX gene have been accomplished in this work. The MIOX gene has a length of 3608 bp, which encodes 286 amino acids (AA). The secondary structure revealed α-helical and random coils containing 40.56% alpha helices, 38.81% random coils, 14.69% extended strands, and 5.94% beta turns. The subcellular localization results showed that 56% of the MIOX gene is found in cytoplasm and then 10% in lysosome. The Ramachandran plot analysis showed that 90.2% of residues fall in the most favored region and 9.8% in the additional allowed region. Virtual screening of ligands and molecular docking of inositol (CID-892) and D-glucuronic acid (CID-94715) showed the highest docking score values of - 4.015 and - 3.563, respectively. The Potential Energy OPLS3e was - 1632.608 and - 1545.687. Inositol and D-glucuronic acid interacted with different residues of MIOX protein. However, a greater binding affinity of MIOX was observed with inositol than with D-glucuronic acid. This signifies the biochemical role of inositol that helps in determining the enzymatic efficiency. So, this study offers insights into protein modeling, molecular docking, and virtual screening of ligands against the MIOX receptor, revealing aspects of drug design and preventive approaches for fish salinity tolerance.

Expanding our understanding of auditory sensitivity in fishes is essential not only for advancing sensory biology, but also for assessing the impact of underwater noise on marine life. However, knowledge remains limited for many ecologically and commercially relevant marine species, particularly auditory generalists like the European sea bass (Dicentrarchus labrax). In this study, we used auditory evoked potentials (AEPs) to measure hearing thresholds in 114 juvenile European sea bass across six frequencies (100-600 Hz), representing the largest dataset of its kind for this species. Our results revealed a U-shaped audiogram with highest sensitivity at 300 Hz (mean threshold: 116.8 ± 3.3 dB re 1 µPa), and thresholds up to 22 dB lower than previously reported. These findings suggest that D. labrax has higher auditory sensitivity than previously assumed. We also documented significant interindividual variability in hearing thresholds, particularly at lower frequencies, highlighting the importance of large sample sizes to capture natural variation. These baseline data provide a valuable reference for future studies on acoustic ecology, effects of noise exposure, and welfare optimization in aquaculture settings, and emphasize the need for further auditory research in marine fish species.

Understanding how fishes physiologically cope with contrasting environmental conditions is fundamental to linking trophic ecology with ecosystem function. This study compared erythropoietic and osmoregulatory strategies across fishes representing distinct feeding niches inhabiting two ecologically divergent tropical ecoregions-the freshwater hill streams of the Sub-Himalayan Terai-Dooars and the estuarine rivers of the Indian Sundarbans. Flow cytometric analyses revealed significantly higher Na⁺/K⁺-ATPase protein expression and chloride-cell abundance among carnivorous species of the Sundarbans, followed by omnivores and herbivores (Welch's ANOVA; t-tests). Conversely, hill-stream carnivores exhibited elevated erythropoietic activity and reactive oxygen species (ROS) generation, reflecting enhanced oxygen demand under hypoxic and fast-flowing conditions. Integrative modelling using Random Forest classification and quantile regression demonstrated that trophic guild identity, ecoregional attributes, and their interaction significantly influenced cellular-level variation, delineating distinct physiological traits across ecosystems. Collectively, the findings reveal ecoregion-specific physiological trait syndromes that align with trophic strategies, reflecting adaptive responses to local salinity, oxygen, and flow regimes. These results highlight how organismal physiology mechanistically links trophic ecology with environmental constraints across contrasting tropical ecosystems, offering predictive insight into species resilience and adaptive potential under changing climatic regimes.

Van fish live in Lake Van, which has different physicochemical properties from freshwater and seawater ecosystems. Every year, Van fish migrate from Lake Van, which has extreme physicochemical properties, to the freshwater flowing into the lake to reproduce. During this migration, they are exposed to stress due to the different properties of the aquatic habitats. In this study, changes in the kidney tissue of Van fish during the spawning migration downstream and in freshwater were examined morphometrically, histologically, biochemically, and immunohistochemically. It was observed that proximal tubule area and diameter, collecting duct area and diameter, glomerulus area, Bowman's capsule area, and glomerulus numbers changed in the kidneys of fish sampled from downstream and freshwater. Na + /K + ATPase transmembrane proteins (NKA) and apoptotic cells were immunohistochemically labeled in both aquatic areas in the kidney tissue. While relative cells containing NKA were determined to be dense in stream samples, apoptotic cells were determined to be more numerous in the kidney tissue sampled from the downstream environment. Plasma urea, uric acid, and sodium were high in downstream, while creatinine, chloride, magnesium, and potassium were also high in freshwater. As a result, it was determined that changes in the morphological structure and histology of the kidney tissue of Van fish were necessary for adaptation in different aquatic habitats.

This study aimed to evaluate the effects of dietary inclusion of Yucca schidigera extract and Bacillus subtilis on the growth performance, immune status, and water quality of Nile tilapia (Oreochromis niloticus) fingerlings. A total of 120 fish (13.54 ± 0.32 g) were randomly distributed into four groups (three replicates each). Each group fed one of the four experimental diets for 65 days: a control diet without additives (CON), a yucca-supplemented diet (0.2 g kg⁻¹; Y), a Bacillus-supplemented diet (1.0 g kg⁻¹; B), or a combined yucca and Bacillus diet (0.2 + 1.0 g kg⁻¹; YB). Water quality analysis indicated that unionized ammonia (NH₃) concentration was the highest in CON and the lowest in YB (p ≤ 0.05). B and YB exhibited superior growth performance and feed efficiency compared to Y and CON (p ≤ 0.05). The highest activities of protease, amylase, and lipase were recorded in YB, followed by B and then Y, while CON exhibited the poorest results. Phagocytic activity, respiratory burst, and complement activity were the greatest in YB, intermediate in B and Y, and the lowest in CON (p ≤ 0.05). Lysozyme activity was found to be significantly higher in B, followed by YB, with the lowest activity observed in CON (p ≤ 0.05). Antioxidant enzyme levels (superoxide dismutase, glutathione peroxidase, reduced glutathione, and total antioxidant capacity) were maximized in YB and minimized in CON with intermediate results in B (p ≤ 0.05), whereas malondialdehyde concentration showed the opposite trend. YB and B exhibited higher levels of interleukin-8 and tumor necrosis factor alpha compared to Y, while CON showed the lowest expression (p ≤ 0.05). Interleukin-1 beta expression was the highest in B, followed by YB, then Y, with the lowest levels observed in CON (p ≤ 0.05). Thus, dietary supplementation with Yucca schidigera extract and Bacillus subtilis, in combination, may represent an effective strategy to improve water quality, growth performance, and immune-antioxidant responses in Nile tilapia.

The present study evaluated the effects of dietary selenium (Se) supplementation on growth performance, physiological responses, tissue fatty acid profiles, and the expression of genes related to fatty acid metabolism in juvenile grouper (Epinephelus coioides). A control diet based on soy protein concentrate, replacing 40% of the fish meal protein, was supplemented with graded levels of Se at 0, 0.3, 0.6, and 1.0 mg Se kg^-1. A fish meal-based reference diet was also included for comparison. The five test feeds were assigned to three groups of fish with an average weight of 13.14 ± 0.03 g, and cultured in a recirculating aquaculture system for 56 days. No significant differences (p > 0.05) were observed among dietary treatments in terms of weight gain, feed efficiency, survival, and whole-body proximate composition of grouper. Tissue Se concentrations in whole body, liver, and muscle, hepatic glutathione peroxidase activity, and proportions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased proportionally with dietary Se levels. Whole-body EPA retention was highest in fish fed the reference diet and 1.0 mg Se kg^-1, intermediate in the 0.6 mg Se kg^-1 group, and lowest in the 0 and 0.3 mg Se kg^-1 groups. Similarly, DHA retention was elevated in fish fed the reference diet and 1.0 mg Se kg^-1 diet. Furthermore, hepatic mRNA expression levels of fatty acid desaturase 2 (FAD2), elongase 5 (FAD5), and peroxisome proliferator-activated receptor gamma (PPAR-γ) were upregulated in a dose-dependent manner in response to dietary Se. These findings demonstrate that Se supplementation can enhance antioxidant defense mechanisms, tissue Se deposition, and the hepatic accumulation of EPA and DHA.

Atlantic cod (Gadus morhua) larvae begin exogenous feeding while organ systems are still immature. Although the liver is morphologically differentiated at hatching, its functional development remains poorly understood. This study characterized histomorphological liver development in cod larvae using (1) monoclonal antibodies C219 and C494 to assess biliary secretory capacity across the hepatocyte canalicular membrane via ATP-binding cassette transporters, and (2) hepatic vacuolization as an indicator of energy storage maturation. Larvae were fed four formulated diets in a 2 × 2 factorial design from 17-61 days post-hatching (dph) to test effects of phospholipid level (~ 7 vs. 6 % dry matter) and bile salt supplementation (0 vs. 0.04 % dry matter). Only C219 labeled bile canaliculi, evident before first-feeding (2 dph) and peaking at 30 dph (9.2 mm standard length), suggesting enhanced capacity for phosphatidylcholine (Abcb4) and/or bile salt (Abcb11) efflux prior to metamorphic climax. Hepatic vacuolization remained low (2.3 %) until late metamorphosis, then increased 14-fold (35.9 %) in a sigmoid pattern with larval size. The steepest rise occurred at 17.7 mm standard length, marking the onset of hepatic lipid storage as larvae transition to juveniles. Dietary treatments did not significantly affect C219 labeling, vacuolization or histological biomarkers of nutritional status. These results indicate that cod liver functionality develops progressively during the larval stage and is largely unaffected by dietary phospholipid level and bile salt supplementation under the tested conditions.

Low dissolved oxygen (DO), or hypoxia, has a profound impact on the physiological and neurological health of aquatic organisms, particularly oxygen-sensitive organs such as the brain. The aim was to investigate the effects of pyrimidine and its derivative, arylvinylpyrimidine (AVP), on neuronal health in the brain of the lesser studied Heteropneustes fossilis under hypoxic conditions. Laboratory-acclimatized fish were exposed to critical threshold hypoxia (2 mg/L DO for 8 h) based on behavioural and brain histopathology observations. For remediation by pyrimidine and AVP in the hypoxic brain, fish were divided into eight experimental groups; four groups maintained for five days as control [without treatment, with 8 h hypoxia, and only drug effect (pyrimidine, 10 pg/mL or AVP, 0.1 µg/mL)] and four groups were maintained as pre- (drug for five days followed by hypoxia for 8 h) and post- (8 h hypoxia followed by drug for five days) treatment with pyrimidine (10 pg/mL) and AVP (0.1 µg/mL) separately. The results showed that air breather H. fossilis exhibited severe hypoxic effects on neuronal health. Hypoxia significantly elevated antioxidant enzyme activity, and lipid peroxidation (LPO), reduced carbohydrate concentration, and increased total lipid content without affecting total protein level in the brain. The hypoxic brain showed a clear stress effect on cellular and neuronal texture. Hypoxia also significantly influenced neurotransmitter synthesis enzymes [acetylcholinesterase (AChE), tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DBH), and tryptophan hydroxylase-2 (TPH2)]. Hypoxia induced brain alteration was effectively reversed by pyrimidine and AVP treatment. Among different experimental sets, post-treatment being more effective than pre-treatment, and AVP showed greater effectiveness than pyrimidine. These findings demonstrate pyrimidine and AVP as neuroprotective agents against hypoxia-induced damage in the H. fossilis brain and suggest their potential therapeutic utility in managing hypoxia induced neuronal damage in aquatic animals.