Fish Physiology and Biochemistry最新文献

Arsenic (As) is a widespread environmental pollutant that poses serious risks to aquatic organisms, particularly affecting neurological health through oxidative damage, endoplasmic reticulum (ER) stress, and apoptosis. Natural bioactive compounds such as genistein (GNT), a soy-derived isoflavone, have shown potential in counteracting heavy metal-induced toxicity due to their antioxidant and anti-apoptotic activities. This study evaluated the neuroprotective effects of dietary GNT (500 mg/kg) in Nile tilapia (Oreochromis niloticus) exposed to 10 µg/L As for 60 days. Arsenic exposure significantly impaired neurobehavioral performance, including reduced ingestive, swimming behaviors, and aggression. Dietary supplementation with GNT effectively ameliorated these behavioral disturbances. At the biochemical level, As exposure decreased the activities of key brain antioxidants, superoxide dismutase, catalase, and reduced glutathione, while increasing malondialdehyde (MDA). Genistein reversed these oxidative imbalances, restoring antioxidant enzyme activities and reducing MDA levels. Furthermore, GNT significantly upregulated brain acetylcholinesterase content and modulated the expression of genes associated with endoplasmic reticulum (ER) stress and apoptosis. Specifically, GNT reversed As-induced dysregulation in the expression of jnk, chop, eif-2a, xbp-1, ire-1a, atf-6, bip, perk, caspase-3, bax, and bcl-2, indicating its role in mitigating ER stress and apoptotic signaling. Histopathological examination confirmed the protective role of GNT against As-induced brain tissue damage. In conclusion, GNT supplementation offers promising neuroprotection against As-induced toxicity via the modulation of oxidative stress, ER stress, and apoptosis in Nile tilapia.

Climate change, including global warming, is associated with an increase in water temperature, which leads to increased water evaporation from water bodies, resulting in elevated salinity and decreased dissolved oxygen (DO₂) levels. This may deteriorate fish health and productivity, and threaten the sustainability of aquaculture. Hence, the current study was carried out to investigate the interactions between hypoxia and increased salinity, as well as their impact on growth parameters, digestive enzymes, serum biochemistry, antioxidative response, and histopathology in Nile tilapia (Oreochromis niloticus). A total of 270 juvenile fish were impartially allocated into 18 aquariums (six treatments with three replicates) in a 2 × 3 factorial design, which included two oxygen levels (normoxia = 5.5-6 mg/L DO₂ and hypoxia = 1-1.5 mg/L DO₂) and three salinity conditions (0, 7, and 14 g/L) over 56 days feeding on a commercial diet (32% protein). Salinity and hypoxia significantly reduced growth and feed utilization. The most declared weight gain and feed conversion ratios were obtained under normoxic and freshwater conditions, although the survival rate was not considerably altered. Hypoxia increased RBCs, hemoglobin, and hematocrit, while elevated salinity significantly reduced them. Hypoxia and elevated salinity impaired digestive enzymes (protease, lipase, α-amylase), increased plasma cortisol, glucose, and liver enzyme levels (aspartate aminotransferase and alanine aminotransferase), lipid profile levels (total cholesterol and triglycerides), while decreasing plasma total protein. The immunity response (lysozyme activity, respiratory burst, phagocytosis, and IgM) was markedly reduced under hypoxia and hypersalinity, while they were markedly enhanced under normoxia and freshwater conditions. Fish reared under hypoxia and higher salinity exhibited structural damage in gills, intestine, and liver tissues. Our findings show that environmental stressors (hypoxia and excessive salinity) harm Nile tilapia growth and well-being, emphasizing the need to improve aquaculture settings in response to climate change.

Preventive health management is central to modern aquaculture practices, within which functional feed additives are a key tool to optimising fish robustness and disease resilience. Despite being well documented, only few studies have assessed the dose-effect of graded levels of S. cerevisiae yeast cell wall (YCW) on fish performance and mucosal barrier immunity. A 9-week trial was conducted to assess the impact of graded levels of YCW on the performance and mucosal barriers of the European seabass under period: (1) non-challenge (43 days) then (2) with an applied husbandry stressors (20 days) in the form of high stocking density, low water oxygen level, and repetitive handling. The four experimental diets were produced by incorporating graded levels of YCW (0.0, control; 1.5; 3.0 or 4.5 kg/MT) which were top dressed on the basal diet prior extrusion. At the end of the period 1, fish supplemented with YCW at 4.5 kg/MT revealed a 5% increase in body-weight compared to the control. Likewise, throughout the experimental period SGR and FCR were also improved by YCW supplementation (+ 5.8% and + 8.3% with YCW4.5, respectively). Supplemented diets increased intraepithelial lymphocytes density and the highest level of intake was associated with increased skin mucus secretion (+ 31% with YCW 4.5 kg/MT). Finally, we observed a linear relationship between fecal calprotectin-like levels and the YCW gradient: a positive correlation during period 1 and a negative correlation during period 2. In contrast, YCW supplementation levels were characterized by a positive linear relationship with fecal mucins across both periods. These results provide novel insights on the benefits and associated mechanisms of YCW extracts and reveal an optimal dose response with inclusion levels between 3.0 and 4.5 kg/MT. This study demonstrates that YCW dietary inclusion enhances growth performance, feed utilization, and mucosal immune barrier function in European seabass, with improved stress resilience evidenced by biomarkers fecal calprotectin-like and fecal mucins.

This study investigated the effects of substituting Tenebrio molitor larvae meal (TM) for fishmeal at varying inclusion levels (0%-TM0, 50%-TM50, 75%-TM75 and 100%-TM100) on growth performance, digestive enzyme activities, and antioxidant responses in Nile tilapia (Oreochromis niloticus). Four different isonitrogenous and isolipidic experimental diets were formulated and fed to the fish for 12 weeks. The highest growth performance was observed in the TM75 group, while polynomial regression analysis indicated an optimal replacement level around 66%. TM inclusion significantly modulated the activities of digestive enzymes amylase, lipase, pepsin, and trypsin. Antioxidant enzymes including catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) showed increased activity in TM-fed groups, particularly at moderate inclusion levels. However, elevated levels of lipid peroxidation (LPO) in the TM75 and TM100 groups indicated a threshold beyond which oxidative stress may arise despite enhanced antioxidant defense. These results suggest that TM meal can be a promising alternative protein source in tilapia diets when used at optimized inclusion levels, supporting both physiological performance and oxidative balance. The findings contribute to sustainable aquafeed strategies by identifying the biological and functional limits of insect meal use in freshwater fish.

The binding of fatty acid (FA) to fatty acid translocase (FAT/CD36) and subsequent regulation of lipid metabolism transcription factors, such as peroxisome proliferator-activated receptors α (PPARα) and sterol regulatory element-binding protein-1c (SREBP-1c), is an important hypothalamic fatty acid-sensing mechanism in vertebrates. The hypothalamus exhibits responsiveness to specific fatty acids and is involved in reproductive regulation. However, the link between FA sensing and reproductive regulation in the hypothalamus remains poorly understood teleosts. Therefore, the expression of genes involved in the FA-sensing mechanism-such as fat/cd36, pparα, and srebp1c, as well as gonadotropin-releasing hormone (GnRH: cgnrh, sgnrh, sbgnrh) in the hypothalamus-was investigated after intracranial administration and hypothalamic incubation of polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA), eicosapentanoic acid (EPA), and linoleic acid (LA) for 4 h in the spotted scat (Scatophagus argus). Compared to the control, intracranial administration and hypothalamic incubation of DHA and LA, as well as hypothalamic incubation of EPA, increased the levels of fat/cd36, pparα, and srebp1c. However, the expression of fat/cd36 and pparα was significantly decreased, and the level of srebp1c showed a downward trend only in the EPA group when co-incubated with the FAT/CD36 inhibitor Sulfo-N-succinimidyl oleate sodium (SSO), compared to incubation with EPA alone. After the application of PPARα antagonist GW6471, the expression of pparα in the hypothalamus decreased significantly in the DHA, EPA, and LA treatment groups, compared to incubation with DHA, EPA, and LA alone. Levels of fsh and lh in the pituitary gland were changed significantly after the intracranial administration of DHA, EPA, and LA. Compared to the control, the levels of cgnrh, sgnrh, and sbgnrh increased in the hypothalamus after both hypothalamic incubation and intracranial administration of EPA and LA. Levels of cgnrh increased in the hypothalamus after incubation, but not after intracranial administration of DHA. However, compared to the control, levels of sgnrh and sbgnrh increased after hypothalamic incubation with DHA and EPA. Only sgnrh levels decreased after incubation with LA in the presence of SSO compared to the FA treatment group alone. In the presence of GW6471, only sgnrh levels decreased after incubation with LA in the presence of SSO compared to the FA treatment group alone; the levels of cgnrh, sgnrh, and sbgnrh after LA incubation, the levels of sbgnrh after EPA incubation, and the levels of sbgnrh after DHA incubation were all significantly decreased compared to the control. These results showed that DHA, EPA, and LA could activate fat/cd36 and pparα, which are involved in reproductive regulation in the hypothalamus of the spotted scat. These results provide evidence that hypothalamic FA sensing is involved in regulating reproduction in teleosts.

Environmental contamination with heavy metals increases the risk of copper (Cu²⁺) exposure in fish, animals, and humans, potentially leading to poisoning and even fatality. This study aimed to assess the alleviating effects of α-lipoic acid (α-LA), a potent antioxidant, on oxidative stress and lipid metabolism disorders elicited by Cu²⁺. Swamp eel (Monopterus albus) were randomly divided into four groups: control group (untreated), α-LA group (+ α-LA 1000 mg/kg), Cu²⁺ group (+ Cu²⁺ 500 mg/kg), and Cu²⁺ + α-LA (+ Cu²⁺ 500 mg/kg + α-LA 1000 mg/kg) group, and were fed for 56 days. Subsequently, the effects of α-LA on Cu²⁺-induced toxicity were investigated by analyzing histopathological alterations, biochemical indicators and gene expression profile alterations. Our findings demonstrated that α-LA administration significantly diminishes hepatic Cu²⁺ accumulation and mitigates hepatic histopathological lesions caused by Cu²⁺. Moreover, α-LA invigorated the potency of antioxidant enzymes, including POD, GPx, and GST, and diminished GSSG levels. Besides, α-LA alleviated Cu²⁺-induced oxidative stress via the Nrf2 signaling pathway by its fine-tuning towards various genes (up-regulation of nrf2, cat, and gclc, and down-regulation of ho-1, sod1, and nqo1). Meanwhile, α-LA also alleviated dyslipidemia by reducing Cu²⁺-induced steatosis and lowering serum levels of T-CHO, LDL-CHO, and TG, while increasing HDL-CHO and LPL + HL. Furthermore, α-LA relieved Cu²⁺-induced lipid metabolic disorders induced by upregulating the expression levels of genes related to the PPARα signaling pathway, encompassing pparα-like, rxrα, lpl-like, acsl4a, acox1, and me1, and promoted lipolysis and decreased lipid accumulation. In summary, α-LA possesses protective effects against Cu²⁺-induced oxidative stress and lipid metabolism disorders by activating the Nrf2/PPARα signaling pathway in swamp eel. This study provides insights into alleviating the toxicity of heavy metals in aquatic organisms.

Anaesthesia is a necessary step during fish manipulation. Tricaine methane-sulfonate (MS-222) is the most commonly used anaesthetic in experimental trials; however, its use in food fish production is strictly regulated. This study aimed to evaluate clove oil, less persistent and authorized in European countries, as an alternative to MS-222 for skin mucus analyses in aquaculture settings. For this purpose, rainbow trout individuals from a commercial factory were sedated with clove oil or MS-222. The concentration of protein, glucose, lactate, and cortisol and the antibacterial activity were measured in both skin mucus and plasma. Additionally, FRAP, total protease activity, and lysozyme activity were also analysed for mucus samples. Recovery times differed significantly between treatments, being approximately four times longer for clove oil (at the farm's standard dose) than for MS-222 (at the standard laboratory dose). However, none of the stress-related biomarkers in mucus were affected by the anaesthetic treatment, whereas plasma from clove oil-treated fish showed increased lactate and reduced cortisol levels. The in vitro bacterial growth inhibition assay using mucus and plasma provides a reliable and rapid method for assessing fish innate immunity. No significant differences were observed between treatments against any of the bacterial strains tested. Overall, the findings strongly endorse the use of skin mucus as an effective method for studying and monitoring trout in aquaculture settings.

The present research examined the use of a commercial acidifier blend (CAB) as a feed supplement on growth, digestive enzymes, antioxidant, immunological biomarkers, and defense of Nile tilapia (Oreochromis niloticus) against Aeromonas sobria disease. Fish (22.7 ± 0.76 g) were fed on 0.0 (the control), 1.0, 2.0, 4.0, or 8.0 g CAB/kg feed for 60 days. After that, fish were intraperitoneally injected with A. sobria, and their survival was monitored for a further 10 days. The fish group that received 4.0 g CAB/kg feed showed the highest growth rate. The improved growth in this group is correlated with the upregulation of mRNA expressions of growth-related genes (IGF-1 and GH). In addition, the highest activities of intestinal proteases, lipase, and α-amylase were observed in fish fed with 4.0 g CAB/kg feed. Compared to the control group, fish fed on CAB-containing diets showed significantly higher activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx). In a parallel way, the mRNA expression of SOD, CAT, and GPx genes were upregulated in CAB-fed groups, particularly at levels of 4.0-8.0 g CAB/kg feed. Conversely, malondialdehyde levels were maximized in the control group but were reduced in CAB-fed fish. Additionally, dietary CAB, especially at levels of 4-8 g/kg diet progressively enhanced the immune function and upregulated the expression of IL-1ß, IL-8, and IL-10 genes. The bactericidal and challenge tests against A. sobria evoked that CAB exhibited antibacterial properties; the maximum mortality rate following the bacterial infection was noted in the control group (90%); meanwhile, CAB-fed fish, especially at a rate of 4.0-8.0 g/kg feed exhibited lower mortality rates (40% and 45%, respectively). Overall, this study recommends incorporating 4.0 g CAB/kg feed to mitigate the negative impacts of dietary soybean and improve the growth, antioxidant, and immunological indices in Nile tilapia fingerlings.

Eugenol is a widely used plant-based anesthetic in aquaculture. However, its anticholinesterase activity may affect reproductive physiology, particularly in gravid females. This study examined the effects of eugenol on the anesthetic response, acetylcholinesterase (AChE) activity, and parasite abundance in wild-caught adult females of the Neotropical fish Cnesterodon decemmaculatus. Ninety females were exposed to five eugenol concentrations (10, 20, 30, 40, and 50 mgL⁻¹), and a control group without anesthetic. Anesthesia induction and recovery times were recorded, and AChE activity was estimated in gravid females. Induction time decreased with increasing eugenol concentration up to 40 mgL⁻¹, with no further reduction at 50 mgL⁻¹. Recovery times did not differ significantly among treatments. AChE activity was significantly inhibited, and both abortion and mortality were observed in gravid females exposed to 10 mgL^-1. Additionally, a reduction in the mean abundance of the Eschistostomatidae family was detected only after the 40 mgL⁻¹ treatment, in all treated specimens. These findings highlight the physiological vulnerability of gravid females to eugenol exposure and suggest a potential antiparasitic effect at specific concentrations. The results emphasise the importance of considering reproductive status when assessing anesthetic safety in ovoviviparous fish.