Fish Physiology and Biochemistry最新文献

As polychaete meal (PM) from Hediste diversicolor has been reported to be a promising alternative to fish meal (FM) and fish oil (FO) in aquafeeds, we hypothesized that replacing FM with PM would support growth performance, feed utilization, and flesh fatty acid profile of European seabass (Dicentrarchus labrax). Therefore, this study was planned to investigate graded PM inclusion levels (0% [control], 5% [PM5], 10% [PM10], 15% [PM15] and 20% [PM20]), selected based on feasible incorporation limits for juvenile European seabass, as a partial substitute for FM (reduced from 29.45% in the control to 14.55 in PM20) in isonitrogenous (48% protein) and isolipidic (14% lipid) diets. A seven-week trial with a total of 150 fish (initial average weight of 14.56 ± 0.01 g) in triplicate tanks assessed growth performance, feed utilization, nutrient digestibility, body composition, fatty acid profiles, and fish-in-fish-out (FIFO) ratio. Growth performance, feed utilization, and organo-somatic indices of experimental fish remained unaffected by dietary PM levels (P > 0.05). A significant linear increase in apparent digestibility coefficients (ADCs) of protein, energy, and organic matter was observed with increasing PM inclusion (P < 0.05), while lipid ADCs remained unaffected P > 0.05). Whole-body protein and lipid content increased, with a corresponding decrease in moisture as dietary PM levels increased (P < 0.05). Fatty acid profiles and lipid quality indices of the liver and fillet were variably affected, liver PUFA levels declined with higher PM, whereas fillet long-chain PUFAs (Lc-PUFAs) such as arachidonic acid (ARA) and eicosapentaenoic acid (EPA) linearly increased. The FIFO ratio fell below 1 at a 20% PM inclusion. The findings suggest that PM can replace up to 50% of dietary FM and partly FO in seabass diets without compromising growth, nutrient utilization, or fillet quality while enhancing sustainability metrics.

The weatherfish Misgurnus fossilis is a freshwater species that adapts to hypoxic conditions during its developmental stage through the presence of external filamentous gills, which serve as primary respiratory organs. Our experimental study aimed to investigate biochemical changes occurring in weatherfish during its development, from ovulated oocytes to larvae with external gills. The concentrations of thyroid hormones were low and relatively stable up to the larval stage at hatching, provided by maternal reserves. However, levels of free triiodothyronine and total thyroxine increased during the larval stage when external gills were present, likely reflecting preparation for their reduction. This indicates that the function of the endogenous self-synthesis thyroid axis begins in weatherfish at a developmental stage preceding larval metamorphosis. Our results indicate that the free fraction of triiodothyronine is more important during fish metamorphosis than its total content, which generally exhibits limited biological activity within the organism. The increase of thyroid levels coincides with an increase in lipid levels; the rise in cholesterol and triglycerides suggests an elevated energy demand essential for metamorphosis. Consequently, thyroid hormone synthesis coupled with lipid mobilization is likely a key predictor of imminent metamorphosis in fish.

Progranulin (PGRN) is a cysteine-rich secreted protein that is expressed in epithelial cells, immune cells, neurons, and adipocytes. It was first identified for its growth factor-like properties and is involved in early embryogenesis and tissue remodelling, acting as an anti-inflammatory molecule. Recently, PGRN was recognized as an adipokine related to obesity and insulin resistance, revealing its metabolic function. In zebrafish, the homologous gene most similar to the human PGRN gene is grna (granulin a). In this study, we used previously obtained grna knockout (KO) zebrafish to investigate the role of grna in obesity resistance and liver development. To explore the role of grna in obesity, grna^-/- zebrafish and wild-type (WT) zebrafish were fed a high-fat diet (HFD) for 2 months. These results indicated that grna^-/- zebrafish were more resistant to HFD-induced obesity than were WT zebrafish. Compared with WT zebrafish, grna^-/- zebrafish presented less visceral fat, abdominal fat, and hepatic fat. In addition, grna^-/- HFD-fed zebrafish presented more severe hepatic vascular fibrosis than WT HFD-fed zebrafish did. During the development of juvenile zebrafish, grna^-/- zebrafish have smaller livers than WT zebrafish do. In conclusion, our findings suggest that grna plays an important role in regulating obesity susceptibility and liver development in zebrafish.

The present study evaluated the pathophysiological and tissue alterations induced by dietary oxytetracycline (OTC) in rainbow trout (Oncorhynchus mykiss). Fish were exposed to three different doses (T₁ = 40 mg OTC/kg body weight, T₂ = 80 mg OTC/kg body weight, T₃ = 120 mg OTC/kg body weight) alongside a control group (T₀) for a period of 30 days. Hematological, immunological, and biochemical parameters were monitored on days 0, 15, and 30 days of OTC exposure. Higher OTC doses caused a significant reduction in total erythrocyte count (TEC), total leucocyte count (TLC), hemoglobin, packed cell volume (PCV), and mean corpuscular hemoglobin concentration (MCHC) while mean corpuscular volume (MCV) levels increased. Dose-dependent reduction was also observed in immune and biochemical markers such as phagocytic activity, NBT, total Ig, protein, albumin, and globulin, but an increase was noticed in the glucose levels in OTC-fed groups. Histological examination revealed liver alterations including sinusoidal dilation, hepatocyte hypertrophy, pyknosis, and congestion, whereas gills showed lamellar fusion, epithelial lifting, and necrosis, with the most severe changes in the T₃ group. SEM analysis confirmed mucus cell proliferation, secondary lamellar thickening, fusion and degeneration. In liver, micro- and macro-steatosis were also evident in OTC-fed groups. Overall, prolonged exposure to high OTC doses markedly compromised physiological integrity, tissue architecture, and immune function, highlighting potential risks to fish health and welfare.

Recent advances in molecular phenotyping have driven the rapid growth of untargeted, multi-dimensional approaches such as epigenomics, transcriptomics, proteomics, and metabolomics. When applied to ecology, these high-throughput omics tools offer powerful new molecular trait descriptors for investigating biological and environmental processes. Using UHPLC-HRMS/MS, we analyzed metabolome variations in gut, liver, and muscle tissues of chubs and gudgeons collected in summer 2019 from French rivers affected by benthic cyanobacterial blooms. Tissue-specific metabolomic profiles were evident, with muscle metabolomes showing the most distinct species differentiation. The different tissue metabolomes of both fish species also varied by sampling location, indicating local environmental influences. Notably, fish from the Vienne site exhibited molecular signatures of metabolic stress, including elevated oxidized glutathione and bile acids, and decreased purines, amino acids, peptides, and lipids-potentially linked to anatoxin-a-producing cyanobacterial mats. These findings underscore the potential of environmental metabolomics as a sensitive tool for assessing ecological stress and support its integration into routine environmental bio-indicator programs.

This study aimed to explore the effect of paeonol (PAE) on growth performance and liver health in largemouth bass (Micropterus salmoides) exposed to cadmium (Cd). Five experimental groups were designed: one control group reared in clean water and fed a basal diet (CONT), alongside four cadmium-exposed groups maintained in 2.75 mg/kg Cd-containing water and fed the basal diet supplemented with 0 mg/kg (Cd), 100 mg/kg (PAE100-Cd), 200 mg/kg (PAE200-Cd), and 400 mg/kg PAE (PAE400-Cd), respectively. The experiment lasted for 56 days. The results showed that Cd exposure significantly inhibited the growth performance of largemouth bass, caused liver dysfunction and pathological tissue damage, led to oxidative stress, inflammatory response, and apoptosis, and induced the expression of the epidermal growth factor receptor (ErbB1)-extracellular signal-regulated kinase (ERK) pathway genes. However, PAE supplementation (200-400 mg/kg) significantly improved the growth performance of largemouth bass. In addition, 200-400 mg/kg PAE reduced the serum levels of hepatic injury biomarkers (AKP, ALT, LDH, and AST) and alleviated histopathological lesions. Furthermore, PAE200-Cd increased the activities of superoxide dismutase (SOD) and catalase (CAT) and reduced malondialdehyde (MDA) levels in the liver. Moreover, PAE200-Cd and PAE400-Cd down-regulated the expression of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), nuclear factor kappa-B p65 (NF-κB p65), ErbB1, and cellular FBJ osteosarcoma oncogene (C-fos) in the liver. PAE200-Cd significantly increased the expression of cytochrome P450 family 1 subfamily A (CYP1A1) and downregulated the expression of metallothionein (MT) and cysteine-aspartic proteases-9 (Caspase-9). The optimal PAE dose for counteracting waterborne Cd-induced growth impairment and hepatic oxidative stress was 173.37-173.90 mg/kg for largemouth bass.

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.