Fish Physiology and Biochemistry最新文献

Addressing the adverse effects of high-carbohydrate diets (HCD) on fish growth and health has been a critical area of aquaculture research, as it remains a key factor limiting the broader application of HCD in the industry. Recent studies have focused on the liver mechanisms involved in HCD-induced challenges, while limited attention has been given to adipose tissue. This study investigated the impact of enhancing adipocyte hyperplasia on growth performance, immunity, antioxidative capacity, inflammation, and metabolism in grass carp (Ctenopharyngodon idellus) subjected to an HCD. Rosiglitazone (R), a peroxisome proliferator-activated γ agonist, was used to promote adipocyte hyperplasia. A total of 225 grass carp (initial body weight, 19.05 ± 0.06 g) were divided into three groups (control, HCD, and HCD + R) and fed for 8 weeks, with three replicates per group. The findings indicated that HCD induced inflammation, fibrosis, and metabolic disorders in adipose tissue, which were significantly alleviated following the promotion of adipocyte hyperplasia (P < 0.05). Improvement in the health status of adipose tissue resulted in a significant reduction in the pro-inflammatory cytokine interleukin-1β (IL-1β) produced and secreted by adipose tissue. In contrast, IL-1 receptors and downstream related genes in the liver and muscle were significantly downregulated (P < 0.05). Furthermore, promoting adipocyte hyperplasia alleviated hepatic steatosis and enhanced muscle protein synthesis. Serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglycerides (TG), glucose (GLU), and lactate dehydrogenase (LDH) returned to normal after promoting adipocyte hyperplasia. Notably, promoting adipocyte hyperplasia enhanced anti-oxidant enzyme activities in the serum and significantly improved immune function in the grass carp (P < 0.05). These enhancements contributed to improved growth performance and feed efficiency. Conclusively, modifying the pattern of adipose tissue expansion by promoting adipocyte hyperplasia mitigated the adverse effects of HCD on health and growth performance while enhancing both anti-oxidant and immune capacities in grass carp.

This study investigated the effects of salinity, ammonia, and stocking density on Nile tilapia (Oreochromis niloticus) fingerlings over a 74-days. In three separate experiments, fingerlings (initial weight 25 ± 2.4 g) were exposed to salinity levels (5, 10, 15, and 20 ppt), ammonia concentrations (0.01, 0.02, 0.1, and 0.2 mg/L), and stocking densities (10, 15, 20, and 25 fish per 96 L aquarium). Survival, growth performance, biochemical parameters, and gene expression changes were assessed. Salinity ≥ 15 ppt and ammonia ≥ 0.1 mg/L significantly impaired growth (final weight, weight gain, specific growth rate, and feed efficiency) and increased mortality rates, reaching 37% and 56% at 20 ppt salinity and 0.2 mg/L ammonia, respectively. Elevated salinity and ammonia also caused significant increases in the activities of ALT, AST, LDH enzymes, along with higher serum glucose levels, while disrupting serum protein and ion concentrations, indicating considerable metabolic and osmoregulatory disturbances. At the molecular level, the expression of the growth-promoting IGF-I gene was down-regulated, while inflammatory marker TNFα was up-regulated, suggesting compromised health. Stocking density had less pronounced effects, though densities ≥ 20 fish/aquarium led to reduced growth, altered biochemical markers, and gene expression changes compared to 10-15 fish/aquarium. These findings establish salinity and ammonia tolerance thresholds for tilapia fingerlings, emphasize optimal stocking density, and provide insights into the physiological and molecular responses to multifactorial stressors. The study contributes to sustainable management strategies for tilapia aquaculture under variable environmental conditions.

The yellow drum (Nibea albiflora), a pivotal species within the Sciaenidae family, is economically important in the mariculture along the coastal regions of China. A comprehensive understanding gonadal maturation and spawning processes is crucial for seed production in the artificial propagation of yellow drum. This study investigates serum hormonal fluctuations, gonadal histological features, sex hormone receptor gene expression, and intestinal microbiota composition in both male and female yellow drum during the reproductive season. Twenty individuals were sampled from reproductive stages IV, V, and VI, respectively. During the spawning season, no significant differences were observed in the levels of PROG, E2, and 11-KT across different stages, in both males and females, with no significant sex-based differences. Subsequent analysis indicated a significant upregulation of fshr, lhcgr, and esr expression in the ovary during spawning stages. In contrast, within the testis, the expression levels of fshr, ar, and esr remained relatively constant across different stages, whereas lhcgr expression was markedly higher during the spawning stages compared with prespawning and post-spawning stages. Analysis of intestinal microbiota revealed a predominance of Bacteroidota, Firmicutes, and Proteobacteria, with no significant sex differences. At the class level, the abundances of Alphaproteobacteria, Gammaproteobacteria, and Bacilli exhibited significant fluctuations during the spawning and post-spawning stages in both sexes. At the genus level, g_Muribaculaceae and g_Bacteroides were abundant during spawning stages in both sexes. A Mantel test showed significant positive correlations between PROG levels and the abundances of g_Bacteroides in males. In females, PROG levels were positively correlated with the abundance of g_Prevotella. These findings enhance our understanding of the interplay between reproductive biology and the biological functions of intestinal microbiota in yellow drum broodstock during the reproductive season, thereby laying a foundation for the development of artificial propagation technology in this species.

The circadian system plays a crucial role in most physiological processes. The molecular clock is linked to epigenetic mechanisms, both of which are influenced by nutrient status and, consequently, to feeding. This research investigated how feeding times (mid-light, ML, vs. mid-dark, MD) synchronize daily rhythms of behavior, clock genes, and epigenetic mechanisms in the European sea bass (Dicentrarchus labrax), focusing on hypothalamus and liver to assess the impact on central and peripheral pacemakers. Feeding at MD influenced the molecular clock of the hypothalamus, causing shifts in acrophases (peaks) for genes of the negative loop (per1b, per2, cry1a). In the liver, the ML fed group showed rhythmic expression for all clock genes, whereas only per2 maintained the rhythms in the MD group. Epigenetic genes related to methylation (dnmt1, dnmt3a) and demethylation (tet2, gadd45aa, mbd4) in the liver displayed rhythmic expression in the ML group, but only dnmt3a maintained the rhythm in the MD group. Nutrient-related factors (SAM and SAH) showed differences between day and night, suggesting a different utilization based on feeding times. Finally, sirt1, a gene involved in deacetylation, displayed a clear daily rhythm in the ML group. All epigenetic genes peaked during the night (resting phase). Overall, these findings indicated feeding time serves as a potent zeitgeber, synchronizing circadian clock and epigenetic rhythms in the liver, with peaks during the resting phase, suggesting this phase represents the adequate time for epigenetic modifications.

Aquaculture industry frequently encounters disease outbreaks, high mortalities, as well as emergence of new pathogens due to its intensification. Streptococcus agalactiae (Lancefield's group B Streptococcus) is an important pathogen extensively causing infectious disease in tilapia resulting in huge economic loss and mortality. To date, vaccination has proved to be successful in defending against infectious diseases prevailing among farmed fish species. This study aimed to develop an S. agalactiae inactivated vaccine (SAIV) using molecular adjuvants, flagellin and tilapia interferon gamma (IFN-γ), and to assess the generated immune response and protective efficacy of the adjuvant incorporated vaccine against S. agalactiae infection in Nile tilapia. The fish were vaccinated with SAIV together with either flagellin or IFN-γ and both together by intraperitoneal injection. The vaccinated fish were challenged with a virulent strain of S. agalactiae on day 36 and monitored for 3 weeks to assess cumulative mortality. The results showed that the vaccine offered significant protection with relative percentage survival (RPS) of 59.37%, 71.87%, and 81.25% observed for bacterin vaccine adjuvanted with flagellin, IFN-γ and both, respectively, with an RPS of 15.62% for the unadjuvanted bacterin control group after challenge with S. agalactiae. The vaccine induced specific IgM antibodies against S. agalactiae in the vaccinated groups, and the antibody response was significantly increased following booster vaccination in the fishes administered with vaccine adjuvanted with flagellin, IFN-γ and both. Furthermore, after vaccination, MHC-II and IgM gene expression was found significantly upregulated in head kidney and spleen, in line with an elevated specific IgM titer. Innate immune parameters including catalase, lysozyme, superoxide dismutase, myeloperoxidase, and bactericidal activities were significantly increased in fishes immunized when compared with the unvaccinated controls (P < 0.05). Histopathological examinations of tissue sections of the head kidney, spleen, liver, kidney, gills, and brain were performed on vaccinated and non-vaccinated fish which showed mild infiltrations. In conclusion, flagellin and IFN-γ have shown potential for use as molecular adjuvants to enhance the efficacy of fish vaccines against S. agalactiae infections.

Aquaculture fish face stresses include temperature, ammonia levels, water salinity, and dissolved oxygen. In order to sustain finfish output, it is necessary to assess the impact of unexpected weather on their performance. Thus, this study examined whether Nile tilapia's vitamin E intake reduces heat and salinity stress. After 56 days of feeding a diet enriched with vitamin E at 0, 150, 300, 600, and 1200 mg/kg, Nile tilapia were split into two groups: one was given a 28 g/L salinity increase, and the other to a temperature increase of 36 °C. Heat and salinity stress increased cortisol, glycose AST, ALT, triglycerides, and total cholesterol while decreasing albumin, globulin, and protein. Fish diets with vitamin E significantly improved the parameters above before and after heat and salinity stress. However, heat and salinity stress inhibited superoxide dismutase, catalase, glutathione peroxidase, nitrous oxide, lysozyme, phagocytosis, and immunoglobulin, reducing antioxidant activity and immunological responses. The Nile tilapia diet's vitamin E content increased antioxidant activity and immunological response before and after stress. Heat and salinity stress increased lipid peroxidation (malondialdehyde), but vitamin E-fed fish had lower values than controls. In addition to mild hepatocyte degeneration, pyknosis, and hepatic central vein congestion, heat and salinity stress cause severe vascular congestion with gill lamellar epithelium degeneration, sloughing, and primary filament congestion. In Vit E-treated groups, histomorphology returned to normal. Results showed that vitamin E at 1200 mg/kg in the Nile tilapia diet may be an effective antioxidant immunostimulant against environmental stressors like heat and salinity.

Non-steroidal aromatase inhibitors like tamoxifen citrate are commonly used in aquaculture for sex reversal, yet their broader impacts on fish growth, body composition, serum biochemistry, and gut histomorphology remain underexplored. This study evaluated the effects of tamoxifen citrate on hybrid red tilapia fry growth, reproductive traits, haematological parameters, biochemical profiles, and reproductive hormone levels.A total of 260 swim-up fry (mean weight 0.06 ± 0.04 g) were randomly assigned to four dietary treatments: TA0 (0 mg/kg), TA1 (200 mg/kg), TA2 (400 mg/kg), and TA3 (600 mg/kg), with three replicates of 25 fish each. Fish were fed these diets for 60 days, followed by a 90-day recovery phase in outdoor hapas. The results showed that the male percentage increased significantly with tamoxifen inclusion, reaching 96.83% at 600 mg/kg (P < 0.05). Oestrogen levels decreased, while 11-ketotestosterone increased proportionally with tamoxifen dosage (P < 0.05). Higher tamoxifen inclusion (600 mg/kg) worsened feed conversion ratio (FCR), feed conversion efficiency (FCE), and protein efficiency ratio (PER) during the treatment phase but improved these parameters during recovery, alongside enhanced weight gain and specific growth rate (SGR) (P < 0.05). Higher tamoxifen doses increased hepatosomatic (HSI), viscerosomatic (VSI), and stomach indices while reducing gonadosomatic index (GSI) (P < 0.05). Elevated dosages reduced protein and lipid content but increased moisture levels (P < 0.05). Haemoglobin, MCV, MCH, and MCHC were higher at 200-400 mg tamoxifen/kg, while haematocrit declined with higher dosages (P < 0.05). Elevated tamoxifen levels increased AST, ALT, and globulin but decreased ALP, albumin, and cholesterol (P < 0.05). Moderate tamoxifen dosages (200-400 mg/kg) are recommended for sustainable sex reversal in hybrid red tilapia, minimising physiological and histological disruptions. High dosages (> 400 mg/kg) should be avoided due to haematological stress and immune suppression. Further studies are necessary to assess long-term ecological impacts and aquatic biodiversity.

In aquaculture, phytobiotics are used as growth promoters, immunomodulators, antioxidants, and stress mitigators in several fish species. Herein, we assess the impact of Moringa oleifera seeds petroleum ether extracts (MSE) on growth, hematological, and biochemical responses in whisker catfish (Mystus gulio). A total of 120 M. gulio fingerlings (mean weight 2.09 ± 0.16 g) were randomly distributed in four different experimental groups. Fish were fed to satiation with the experimental diets [T1 (control, 0% MSE), T2 (0.05% MSE), T3 (0.10% MSE), and T4 (0.15% MSE)] for 60 days. Results demonstrated that fingerlings fed with 0.05 and 0.10% MSE-supplemented diet significantly enhanced weight gain, specific growth rate, protein efficiency ratio, hemato-immunological indices (erythrocyte count, leucocyte count, hemoglobin, globulin, serum protein, and respiratory burst activity) and survival compared to other groups (P < 0.05). However, at the higher dose of MSE (0.15%), a significant reduction in the above parameters was observed (P < 0.05). Feeding MSE at 0.05 and 0.10% significantly minimizes the stress responses (blood glucose, cortisol, and catalase). Dose-dependent reduction in serum cholesterol and high-density lipid and an increase in triglyceride were recorded (P < 0.05). Histopathological observation of liver tissue showed congestion of hepatic vein at 0.15% MSE supplementation. Overall, the study suggests that the dietary supplementation of MSE up to 0.10% improves growth, biochemical, and innate immune response in M. gulio fingerlings.

An eight-week feeding trial was conducted to examine the impact of dietary supplementation with lauric acid (LA) on juvenile black sea bream. A basal diet was formulated containing 19.9% fish meal, while five additional diets were prepared, each supplemented with varying levels of LA: LA1 (0.01%), LA2 (0.02%), LA3 (0.04%), LA4 (0.08%), and LA5 (0.16%), denoted as LA1 through LA5, respectively. Triplicate tanks were randomly allocated to each diet, each containing 20 fish with an initial weight of 1.55 ± 0.02 g. At the conclusion of the trial, the LA3 group exhibited significantly greater final body weight (FBW), weight gain (WG), specific growth rate (SGR), and protein efficiency ratio (PER) compared to the other groups (P < 0.05), while the feed conversion ratio (FCR) was markedly higher in the control group. No significant differences were detected among the groups in terms of initial body weight (IBW), muscle fiber index (MFI), protein productive value (PPV), condition factor (CF), hepatosomatic index (HSI), intraperitoneal fat (IPF), viscerosomatic index (VSI), and survival rate (SR) (P > 0.05). No significant variations were observed among the groups in the proximate compositions of the dorsal muscle and whole body (p > 0.05). Furthermore, no significant differences were observed in serum immune and antioxidant parameters in the midgut and hindgut and digestive enzyme activity (P > 0.05) among the treatment groups. However, the LA3 group demonstrated significantly higher levels of serum immune response markers IgM, C3, and C4 compared to the other groups, while malondialdehyde (MDA) levels were significantly elevated in the control group relative to the others. The LA3 group demonstrated significantly increased fore-intestinal villus height, crypt depth, villus height-to-crypt depth ratio, and goblet cell count per villus compared to the other groups (P < 0.05).

Fish sperm cryopreservation is an important technique for optimizing juvenile production in aquaculture stations and laboratories and contributing to the conservation of endangered species. Despite its benefits, the cryopreservation process can cause cellular damage, affecting spermatozoa quality and offspring viability. This study aimed to evaluate the larval development of jundiá Rhamdia quelen originating from cryopreserved sperm. Larvae were obtained from artificial reproduction using oocyte samples from four females combined with fresh (Control) or cryopreserved/thawed sperm. The semen was diluted in the cryoprotective solution (1:3 ratio) consisting of skimmed milk powder (5%), methanol (10%), and fructose (5%), and was packaged into 0.25 mL straws. The straws were then stored and cooled in liquid nitrogen vapor for 18 h. The straws were individually warmed in a water bath at 25 °C for 10 s to thaw the samples. The experiments were performed in triplicates. Sperm quality, fertilization, hatching, and larval development were evaluated. After larval hatching, six larval collections were performed (5, 10, 15, 20, and 25 days after hatching), and 15 larvae were sampled per collection per treatment. Cryopreservation reduced sperm motility (70.48 ± 7.70 fresh to 41.36 ± 4.80 cryopreserved semen), progressivity (3874 fresh to 2505 cryopreserved semen), and beat cross frequency (55.83 ± 155 fresh to 50.22 ± 190 cryopreserved semen). Increased the percentage of sperm with abnormal morphology and increased most sperm pathologies. Furthermore, the fertilization rate was lower in the cryopreserved group (63.1 ± 18, and 83.72 ± 7.59 for fresh semen), while hatching was not different between groups (65.3 ± 18.05 fresh, 48.89 ± 21.77 cryopreserved semen) Otherwise, the initial larval development morphology showed no difference in the appearance of structures such as the presence of the vitelline structure, pigmentation pattern, development of the anal pore, embryonic membrane, eye, barbells, notochord flexion, and fin rays, for both treatments. There was no significant difference in the frequency of structures between larvae from fresh and cryopreserved/thawed sperm, revealing a similar developmental pattern in both treatments. In conclusion, the cryopreservation protocol affects sperm quality; however, those sperm able to fertilize the oocytes originate normal larvae with regular larval development of R. quelen up to 25 days old.