Fish Physiology and Biochemistry最新文献

Epigenetics has a profound impact on fish nutrition and aquaculture by regulating gene expression, physiological traits, and growth without altering the underlying DNA sequence. The changes, particularly DNA methylation, can be passed down through generations, enhancing productivity and disease resistance. External factors like temperature, stress, nutrition and illness exposure can also influence epigenetic changes, affecting protein, omega-3 fatty acids, and probiotics. DNA methylation and dietary factors also enhance resilience, promoting fish health and reducing antibiotic reliance. Unlocking innovative tactics that promote ecological sustainability, economic viability, and food security requires a deeper comprehension of the epigenetic landscape in aquatic species. Epigenetic insights represent a frontier for advancing precision aquaculture and ensuring the long-term resilience of fish production systems. Combining epigenetic knowledge with conventional breeding methods can lead to faster development of fish lines with improved growth rates, disease resistance, and optimal feed conversion. Understanding the epigenetic processes underlying fish nutrition can lead to sustainable aquaculture methods, increased productivity, and improved overall fish health. Dynamically shaped by environmental and nutritional factors, DNA methylation and histone modification improve performance and adaptability. Understanding and applying histone modifications can greatly enhance the resilience and sustainability of aquaculture practices.

Rainbow trout(Oncorhynchus mykiss) is a typical cold-water fish often threatened by high summer temperatures. Nano-selenium as a feed additive can improve the antioxidant capacity of the body and relieve stress. In this study, different levels of nano-selenium (0, 5 and 10 mg/kg) were added to the feed of rainbow trout to determine the changes in spleen structure and expression of related genes in rainbow trout at the proper temperature (18℃) and heat stress temperature (24℃). The results showed that the addition of 5 mg/kg nano-selenium had a more obvious protective effect on rainbow trout spleen. The addition of nano-selenium improved the antioxidant capacity and immunity of rainbow trout spleen at 18 °C. After heat stress, the addition of 5 mg/kg of nano-selenium significantly increased the expression levels of spleen heat shock protein genes, such as HSP10, HSP47, HSP70, HSP90, antioxidant-related genes, such as glutathione peroxidase (GPx), thioredoxin reductase (Trx), superoxide dismutase (SOD1), catalase (CAT) and immune-related genes, such as tumor necrosis factor-α (TNF-α), Interleukin-1β (IL-1β), Immunoglobulin M (IgM), Complement Component 3 (C3), resulting in the improvement of antioxidant capacity and immunity, and the protection of the spleen to alleviate the damages caused by heat stress. This study provides a theoretical basis for the development of anti-heat stress feeds for rainbow trout.

Early life stress is key in development and behaviour and may have long-term effects, as it represents a window of increased vulnerability. In our study we evaluated two stressors, temperature and photoperiod -alone and combined-, in zebrafish (Danio rerio) larvae up to 120 h post-fertilisation. The objective of this study was to investigate the effects of non-lethal environmental stressors and their potential synergistic effects until completion of organogenesis integrating molecular, cellular and behavioural analyses. Larvae were subjected to 4 experimental conditions: "control" (C) (14 h light: 10 h darkness; T = 27 ± 1 °C); "heat shock" (HS) (14 h light: 10 h darkness; T = 34 °C); "darkness" (D) (24 h darkness; T = 27 ± 1 °C) and "stressed" (S⁺) (24 h darkness; T = 34 °C). Our results confirmed phenotypic, behavioural and molecular alterations. The S⁺ larvae showed a lower survival curve, lower regeneration, a higher number of malformations, predominantly those related to the swim bladder, lower motor activity and a dysregulation of miR29a and clocka, hspa9, hspa5 and cxcr4b genes. The results revealed a similar number of Ddx4⁺ cells between groups but non-canonical migration patterns in the S⁺ group. This integrated approach offers new insights into the molecular mechanisms underlying the stress response during embryogenesis and provides a new perspective on the interaction between temperature and light on early-stage development.

The application of cyanobacteria as sustainable feed additives in aquaculture has gained increasing attention due to their nutritional and functional properties. In previous studies, we demonstrated that dietary supplementation with Synechococcus elongatus PCC 7942 improved hepatic homeostasis and modulated the intestinal microbiota of zebrafish (Danio rerio), without adverse effects on intestinal morphology. Building upon these findings, the present study aimed to expand our understanding of the transcriptomic responses in the zebrafish brain to dietary supplementation with S. elongatus. The cyanobacterial biomass presented a proximate composition of 45.19% protein, 21.34% lipids, 10.08% carbohydrates, and 8.01% ash, along with a fatty acid profile rich in palmitic acid (39.96%) and linoleic acid (12.25%). After 35 days of feeding, fish receiving the supplemented diet showed higher daily feed intake and condition factor, while other growth parameters did not differ significantly from the control group. Transcriptomic analysis of the brain revealed differential expression of 15 genes grouped into five functional categories: energy metabolism, calcium homeostasis, neuroplasticity, oxidative stress response, and metabolic regulation. Overexpression of genes such as ldhbb, gapdh, and tsc1a suggests that S. elongatus modulates brain metabolism through enhanced glycolysis and activation of protective cellular pathways. The findings indicate that S. elongatus PCC 7942 exerts neuroprotective and metabolic effects, supporting its potential as a novel dietary supplement in aquaculture.

The use of anaesthetics has become extremely important in promoting responsible welfare practices in aquaculture and research. However, adverse reactions and side effects have been described for commonly used anaesthetics such as MS-222 and eugenol. This study examined thymol as a new anaesthetic for adult zebrafish (Danio rerio), a species for which no previous thymol anaesthesia studies have been reported. Concentration-response tests (25-200 mg/L) were conducted using 10 individual animals per concentration, along with assessments of cardiorespiratory, locomotion, and aversive-related effects. Concentrations below 25 mg/L did not induce anaesthetic effects while 50 and 75 mg/L were most effective, inducing deep anaesthesia with average induction times of around 300 s and recovery times of between 400 and 500 s. Induction times at these concentrations were comparable to those observed with MS-222 and eugenol; however, recovery periods were longer. No mortality was observed at these concentrations, although transient cardiorespiratory depression was noted. Video tracking analyses revealed no significant behavioural changes at the lowest concentrations. In contrast, concentrations above 150 mg/L showed narrow behavioural safety margins and induced aversive responses, rendering them unsuitable for fish aesthesia. Based on these findings, a short 10-min exposure to 50 mg/L thymol resulted in cortisol levels comparable to eugenol and lower than in the control group. These findings support the use of 50 mg/L thymol as an effective and welfare-conscious anaesthetic for adult zebrafish. However, further research is recommended to elucidate thymol's physiological effects and its mechanism of action in this species.

Botia striata (Rao, 1920) is high valued ornamental fish, endemic to the Western ghats of India. This fish requires standardized maturation diet following a feeding regime for it to breed in captivity. Therefore, a study was conducted over a period of 90 days, employed a 2 × 3 factorial design involving six different feeding regimes: T1 (formulated feed, twice daily), T2 (formulated feed, four times daily), T3 (frozen tubifex, twice daily), T4 (frozen tubifex, four times daily), T5 (mixed diet, twice daily), and T6 (mixed diet, four times daily). The provision of selected feeding regimes for 90 days assisted with sand substratum induced the gonadal maturation in the treated fishes (n = 360) and allowed to achieve best final maturation with the success rate of 95% in the T2 experimental group and a lower success rate of 65% in the mixed diet group. Parameters such as hepato-somatic index, gonado-somatic index, histology, and reproductive hormones (11-ketotestosterone, 17β-estradiol, follicle-stimulating hormone (FSH), leutinizing hormone (LH), low-density lipoprotein (LDL), and high-density lipoprotein (HDL)) were analyzed to evaluate male and female gonadal maturation. The relative fecundity of the experimental fishes was studied and correlated with the findings of the experiment. The fish in the T2 had relative fecundity of 247 ± 8.00 no's compared to other treatments. The findings suggest that formulated feed administered four times daily significantly enhanced gonad weight, oocyte number and diameter, addressing the challenges faced in captive breeding of the zebra loach. This study provides valuable insights for optimizing captive maturation and breeding conditions for highly demanded indigenous ornamental fish facilitating its development on a commercial scale.

Germ cell transplantation plays an important role in the conservation of endangered fish species. As one of the most promising and valuable techniques, there are only few successful cases of cross-subfamily germ cell transplantation in fish. The purple loach Leptobotia taeniops, belonging to the subfamily Botiinae, genus Leptobotia, has been classified as "vulnerable" on the "China Biodiversity Red List." Due to the difficulty of artificial breeding of Botiinae fish, we chose hybrid triploid loach belonging to the subfamily Cobitinae as recipient fish for spermatogonia transplantation to obtain donor-derived spermatozoa. Upon their sexual maturity, with gonadosomatic index analysis and histological observation, we found significant differences between the recipient and the control hybrid triploid loach. The number of sperm produced by recipient fish was about 200 times higher than that of hybrid triploids. Combined with the results of sperm motility analysis and sperm DNA gel electrophoresis, recipient fish were able to produce motile donor-derived spermatozoa. Through further scanning electron microscopy observation, we speculated that structurally intact donor-derived spermatozoa had the potential to inseminate. Taken together, to our knowledge, this is the first successful attempt to conduct cross-subfamily germ cell transplantation in fish of the family Cobitidae. This study provides a way for the conservation of Leptobotia fish species, in which there are many endangered fish species.

In our previous study, we generated a membrane-type progesterone receptor γ (paqr5b) knockout zebrafish line. Knocking out paqr5b by genome editing resulted in the loss of neurons in the olfactory rosette (OR). These findings indicated that Paqr5b plays an essential role in the formation of olfactory neurons. In this study, we investigated the extent to which paqr5b^-/- fish lacking olfactory neurons retain their sense of smell. We used a reported tank for zebrafish olfactory analysis with a dividing plate in the middle. The tank was divided into three zones: the right zone, where test substances were added; the neutral zone; and the left zone. The fish were released into the neutral zone at the beginning of each test, the chemical was added to the corner of the right zone, and a 3-min video was taken to track the movements of the fish. The video was then played back, and the time spent in the three zones was counted manually. Both male and female paqr5b^+/+ and paqr5b^-/- zebrafish were separately analyzed for time spent in the three zones after exposure to ATP, cadaverine, and the pheromone 17α,20β-dihydroxy-4-pregnen-3-one (DHP). Both male and female paqr5b^+/+ zebrafish were strongly attracted to ATP and stayed in the right zone for approximately 2 min (67%). In addition, paqr5b^+/+ zebrafish avoided cadaverine and stayed longer in the left zone than in any other zone. In contrast, paqr5b^-/- zebrafish stayed in all three zones for approximately the same amount of time, even after exposure to ATP and cadaverine. The paqr5b^+/+ fish were attracted to DHP and stayed in the right zone longer. Paqr5b^-/- zebrafish of either sex were not reactive to DHP exposure. These results showed that paqr5b^-/- zebrafish lacking olfactory neurons lost responsiveness to odorants and pheromones.

Promoting swimming in aquaculture has been proposed to enhance fish welfare. This study investigated the effects of 6 h of swimming on stress, immune, metabolic, and antioxidant status of juvenile rainbow trout (Oncorhynchus mykiss). Fish (n = 8) were individually subjected to one of four experimental conditions: minimal water flow (control, < 0.1 body-lengths (BL)·s⁻¹); low-speed (L, 0.8 BL·s⁻¹); high-speed (H, 2.3 BL·s⁻¹); and oscillating speeds (O, 0.8/2.3 BL·s⁻¹). Plasma cortisol levels were lower in swimming groups (L, H, O) than that in the control group, indicating reduced stress. Lysozyme and peroxidase activities increased in skin mucus of fish from L and H groups, reflecting enhanced mucosal immunity. Expression of cytokines (tnfα, il1β), inflammation modulators (nfκb1), and immune-related (lyz, ctsd) genes in head-kidney, gills, and heart did not vary among groups. In red muscle, increased citrate synthase activity across swimming conditions reflected enhanced aerobic metabolism, while cytochrome c oxidase activity was higher in fish from H and O groups, indicating elevated mitochondrial oxidative capacity. Lactate dehydrogenase activity was higher in red muscle in the O group, reflecting greater reliance on anaerobic metabolism under oscillating swimming. Increased GSH/GSSG ratio in red and white muscle of L and H groups indicated improved antioxidant status. Nonetheless, higher lipid peroxidation levels in the liver suggest increased oxidative stress in the O group, indicating that oscillating swimming may impose metabolic and oxidative challenges. Results show that short-term induced steady swimming under L and H conditions could be used beforehand when applying procedures that decrease welfare in farmed rainbow trout, such as handling or transport, aiming to reduce stress, improving immune and antioxidant responses.

Pesticide pollution of waterways is a significant problem that compromises the sustainability of aquaculture and harms the health of wild fish. The restoration potential of dietary white poplar leaves (WPL) during long-term hexaflumuron (HEX) exposure in Nile tilapia (Oreochromis niloticus) was studied for 60 days on growth, physiological, behavioral, gene expression, and histopathology assays. Two hundred fish (36.37 ± 0.15 g) were split into four equal groups, each having five replicates. The CONT (control) and WPL groups received basal diets fortified with 0 and 6 g WPL/kg, respectively, and were not treated with HEX. In contrast, the HEX and WPL + HEX groups received the same feeding as the CONT and WPL groups, respectively, and were treated with 0.72 mg/L HEX. The results showed that HEX exposure inhibited growth, induced behavioral alterations, and increased brain 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. However, the activity of acetylcholine esterase (AChE) did not significantly differ due to HEX exposure. HEX toxicity induced histopathological changes in the brain tissue, including pyknotic neurons, satellitosis, and gliosis. Additionally, the shortening of numerous secondary gill filaments and congested gill capillaries within some primary filaments was observed due to HEX exposure. The brain expression of the target of rapamycin, phosphoinositide 3-kinase, and V-akt murine thymoma viral oncogene homolog genes was upregulated, and the microtubule-associated protein light chain kinase 3 gene was downregulated due to HEX exposure. Upregulation of the ubiquitin-binding protein gene and downregulation of Beclin-1 and autophagy-related gene-12 were detected in the gills of the HEX fish with a high mortality rate (24%). Feeding on the WPL diet improved growth and behaviors and reduced brain 8-OHdG levels and mortality (10%). Furthermore, the WPL diet restored the histological picture of the brain and gill tissues and improved the autophagy process of the HEX-exposed fish. Collectively, the WPL diet could be used for the mitigation of the hazardous impacts of HEX toxicity in Nile tilapia. This could enhance our insight into the HEX toxicity mechanism and the protection offered by WPL.