Fish Physiology and Biochemistry最新文献

Anaesthesia is a cornerstone of modern aquaculture practice playing a crucial role in routine fish husbandry procedures and research activities. The present review discusses about anaesthetic use in fish, including commonly used synthetic agents such as MS-222, benzocaine, metomidate, quinaldine, 2-phenoxyethanol, and propofol, together with emerging plant-derived anaesthetics, especially clove oil and other essential oils that have reduced environmental impact. Attention is drawn to the physiological basis of anaesthesia in relation to fish welfare, inclusive of both sedation and general anaesthesia, emphasizing their role in mitigating stress. The review outlines the classical stages of anaesthesia in fish and summarizes important physiological and biochemical responses associated with the use of various anaesthetics. Pharmacokinetic processes, including absorption, primarily across the gills, tissue distribution, metabolism, and excretion are also discussed. Regulatory regimes governing approved anaesthetics are summarized to highlight compliance requirements in aquaculture settings. Particular attention is paid to the use of anaesthetics during transport, where light sedation is shown to effectively decrease metabolic rate thereby significantly improving fish welfare. Finally, the review points towards emerging future directions including the development of eco-friendly plant-based anaesthetics and nanotechnology-enhanced formulations aimed at improving solubility, stability, and efficacy of anaesthetic agents.

Global warming and aquaculture expansion are raising water temperatures and decreasing dissolved oxygen (DO) in freshwater environments, threatening fish survival. Revealing the molecular mechanisms of fish response to heat and/or hypoxia is vital for the development of sustainable aquaculture and genetic breeding strategies. This study examined the molecular adaptations of Megalobrama amblycephala, an important economic fish in China, to environmental stresses. Liver samples from fish subjected to hypoxia (LO), heat (HT), and their combination (HL) were analyzed using transcriptome and whole-genome methylation sequencing. Results indicated that environmental stresses significantly altered gene expression and DNA methylation levels in M. amblycephala, suggesting a molecular basis for enhanced environmental adaptability through metabolic regulation. Comparative analysis showed distinct differences in differentially expressed genes (DEGs) across the three stress groups, with the highest number occurring in the NC vs HL group, indicating a stronger transcriptional response. PPI analysis revealed significant alterations in metabolic pathway gene expression. Examination of the PPI network constructed from DEGs common to all stress groups pinpointed core metabolic regulators, such as the upregulated hk1 and aldoaa and the downregulated gck and fasn, highlighting a coordinated cellular metabolic adaptation to environmental stresses. DNA methylation analysis revealed CG-type methylation as the predominant pattern. The HL group exhibited elevated CHH and CHG methylation compared to other groups. Integration of DMR-promoter genes and DEGs yielded 12, 8, and 29 overlapping genes in the NC vs LO, NC vs HT, and NC vs HL groups, respectively. KEGG analysis of negatively regulated overlapping genes showed significantly enriched pathways: TGF-beta signaling pathway and endocytosis in the NC vs LO group; galactose metabolism and amino sugar and nucleotide sugar metabolism in the NC vs HT group; and other glycan degradation and various types of N-glycan biosynthesis in the NC vs HL group. These findings indicated that the adaptation of M. amblycephala to environmental changes is driven by coordinated changes in specific gene methylation and transcription levels, thereby fine-tuning physiological processes including intracellular signaling, glucose and glycoconjugate metabolism. These findings provide theoretical support for optimizing cultivation strategies of M. amblycephala.

In recent years, there has been growing interest in investigating hydropeaking's impact on rivers. In the case of fish, literature documents stranding, loss of spawning beds, and behavioural changes, while the physiological stress response is less understood. In this study, a natural flow scenario and five hydropeaking scenarios were simulated in a fluvial mesocosm named Greenchannel. Scenarios were characterised through hydraulic/hydrological (water velocity and level, water level fall rate, and frequency and number of inundations) and water quality (temperature, dissolved oxygen levels, turbidity) variables. Different test groups of 15 rainbow trout (Oncorhynchus mykiss) (n = 90) were subjected to these scenarios for 24 h each. Cortisol, creatine phosphokinase (CPK), lactate dehydrogenase (LDH), triglycerides (TGC), lactate, non-esterified fatty acids (NEFA), and histological pigmentation were measured at the end of the tests. The variation in physiological variables in response to the environmental variables characterising each scenario was assessed. The levels of cortisol, lactate, TGC, a pigmentation parameter (i.e. lightness), and water turbidity varied significantly with increasing intensities of hydropeaking, mainly velocity and rate of change of water levels. The mobilisation of metabolites suggests a prolonged stress response extending beyond the acute phase as a result of hydropeaking. Developed environment-physiology models pointed to specific environmental thresholds for rainbow trout (for instance, 0.1 m·s^-1 (velocity) and 0.13 m·h^-1 (rate of change (fall))) above which physiological impacts would lead to irreversible welfare problems. This study provides information on how and to what extent hydropeaking impacts fish communities, guiding the sustainable management of large hydropower plants and the restoration of affected rivers.

The production of monosex male populations is a cornerstone for the efficient aquaculture of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). The industry standard, methyltestosterone (MT), raises environmental concerns, necessitating alternative, targeted strategies. Aromatase inhibitors (AIs) offer a physiological approach by blocking estrogen synthesis, which is crucial for ovarian development. This study evaluated the efficacy of dietary administration of the potent non-steroidal AI, anastrozole, for inducing masculinization in Nile tilapia, assessing its effects on sex ratio, survival, gonadal histology, and key sex hormones. The post-yolk sac absorption fry were fed diets supplemented with anastrozole at 0 (control), 25, 50, 75, or 100 mg/kg for 30 days, followed by a 120-day grow-out phase. Phenotypic sex was determined, and gonadal histology was conducted for confirmation. Plasma levels of cortisol, testosterone, and estradiol (E2) were quantified using an ELISA kit. A dose-dependent increase in the proportion of males was observed, culminating in 100% phenotypic and histological males at the 100 mg/kg dose. Survival rates were significantly reduced at the 75 and 100 mg/kg doses. Hormonal analysis confirmed the mechanism of action: a dramatic, dose-dependent suppression of plasma E2 and a significant accumulation of testosterone in both sexes. Treatment also induced a significant stress response, as indicated by elevated cortisol levels. Dietary anastrozole is a highly effective alternative for producing 100% male Nile tilapia populations through targeted aromatase inhibition. The 75 mg/kg dose, yielding 91.43% males, is proposed as an optimal compromise for commercial application, balancing high masculinization efficiency with acceptable survival rates. The induced stress response warrants further investigation to optimize welfare protocols.

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.