As compound bacteria fermented mackerel processing by-products mixed with soybean meal (FMPBS) has been reported to be a promising alternative to fish meal (FM) in aquafeeds, we hypothesized that replacing FM protein with FMPBS would support growth, feed utilization, and health performance of juvenile black rockfish (Sebastes schlegelii). Therefore, this study was conducted to evaluate the effects of replacing FM protein with FMPBS on growth, feed utilization, antioxidant activity, intestinal and liver morphology of black rockfish. Six isolipidic and isonitrogenous diets were formulated to replace FM protein by FMPBS at 0% (FMPBS0, control group), 20% (FMPBS20), 40% (FMPBS40), 60% (FMPBS60), 80% (FMPBS80) and 100% (FMPBS100), respectively. Fish (initial body weight, 10.36 ± 0.31 g) were randomly allotted to triplicate groups of 30 each and fed diets for 70 days. No significant differences were found in growth, feed intake and feed utilization of fish fed diets replacing up to 60% FM protein with FMPBS, while fish fed diets FMPBS80 and FMPBS100 had lower growth compared with the control group (P < 0.05). Fish fed diets FMPBS80 and FMPBS100 had significantly lower serum alkaline phosphatase activity than that fed diet FMPBS0, and fish fed diet FMPBS100 had lower total protein content than those fed diets FMPBS0 and FMPBS20 (P < 0.05). Fish fed diets FMPBS40 and FMPBS60 had significantly higher liver total superoxide dismutase activities than those fed diets FMPBS0 and FMPBS100 (P < 0.05). Fish fed diet FMPBS40 had higher catalase activity than those fed diets FMPBS80 and FMPBS100 (P < 0.05). The fish fed diet FMPBS100 had higher malondialdehyde content than those fed diets that replaced FM with FMPBS up to 60% (P < 0.05). Intestinal muscular layer thickness and villus length decreased with increasing FMPBS levels, and fish fed diets FMPBS80 and FMPBS100 had lower values (P < 0.05). Fish fed diets FMPBS80 and FMPBS100 resulted in hepatic steatosis and produced lesions. Overall, the findings suggest that FM protein could be replaced by 60% FMPBS without adverse effects on growth performance, feed efficiency and health of juvenile black rockfish, but replacing 80% and 100% FM protein with FMPBS had a negative impact on growth and health status.
Zebrafish (Danio rerio) is used as a model to study adrenergic signaling and pigment cell development because their genetic structure matches human genetics and enables advanced scientific research methods. Researchers use zebrafish to conduct their studies in three different research areas which include cellular signaling studies and toxicology research and pharmacology investigations and translational scientific work. Hormonal processes through alpha-MSH MCH and melatonin interact with each other to regulate pigment distribution. The GPCR-mediated pathways initiate melanosome aggregation and dispersion processes through catecholamine binding which leads to cyclic AMP (cAMP) and calcium (Ca2+) pathway activation. The adrenergic signaling system adjusts to different environmental factors and endocrine disruptors which then creates changes to both pigmentation and behavioral patterns. The review examines how adrenergic receptor signaling works in the body and demonstrates its role in controlling melanophore functions. This review underscores the importance of adrenergic signaling in zebrafish as a model system that bridges fundamental cellular biology with translational applications in human health, drug development, and environmental toxicology, offering valuable perspectives for future interdisciplinary research.
Intensive farming of Nile tilapia (Oreochromis niloticus) heightens susceptibility to infectious diseases, including motile aeromonad septicemia caused by Aeromonas hydrophila, thereby necessitating sustainable alternatives to antibiotics. This study investigated the effects of dietary supplementation with Ocimum basilicum (sweet basil) essential oil (1% w/w) and Thymus vulgaris (thyme) essential oil (0.5% w/w) on growth performance, hematological parameters, serum biochemistry, innate immune responses, cytokine profiles, and resistance to experimental A. hydrophila challenge. A total of 180 juvenile Nile tilapia (initial weight 13.21 ± 0.16 g) were randomly assigned to three dietary treatment groups (three replicates of 20 fish per treatment) and fed for 60 days: (1) basal control diet, (2) basal diet supplemented with 1% O. basilicum essential oil, and (3) basal diet supplemented with 0.5% T. vulgaris essential oil. Fish then received intraperitoneal A. hydrophila challenge (0.1 mL of 1.5 × 108 CFU mL⁻1). Growth, hematological, serum biochemical, and innate immune parameters (lysozyme, nitric oxide, phagocytic index) were assessed at days 30, 60, and 75 (15 days post-challenge). Differential leukocyte counts and cytokine concentrations (TNF-α, IL-1β, IL-6, IL-2, IL-10) were assessed at day 75, and histopathological analysis of hepatic and cephalic kidney tissues was performed to evaluate the protective effects of dietary supplementation against A. hydrophila-induced tissue damage. Both essential oil supplements significantly enhanced growth performance (final body weight and weight gain), hematological indices (hemoglobin concentration and erythrocyte and total leukocyte counts), serum protein profiles (total protein, albumin, and globulin), and innate immune function (lysozyme activity, nitric oxide production, and phagocytic index) compared to the control group (P ≤ 0.05). Notably, the diet supplemented with 1% O. basilicum essential oil produced substantial responses than the diet supplemented with 0.5% T. vulgaris essential oil across several assessed parameters (P ≤ 0.05). Fish fed the O. basilicum-supplemented diet had the highest levels of both pro-inflammatory (TNF-α, IL-1β, IL-6) and anti-inflammatory (IL-10) cytokines, and the lowest overall mortality rate (2.2 ± 2.2%; relative percent survival [RPS] = 96.7 ± 3.3%). The T. vulgaris group had a mortality rate of 13.3 ± 3.9%; RPS = 82.1 ± 6.4%, and the non-supplemented control group had a mortality rate of 77.8 ± 5.9%. Histopathology confirmed markedly diminished renal and hepatic lesions, coupled with increased activation of melanomacrophage centers in both essential oil-supplemented groups. These results suggest that adding 1% O. basilicum essential oil to the diet of Nile tilapia promotes growth, boosts the immune system, and provides greater protection against A. hydrophila infection than adding 0.5% T. vulgaris essential oil. The findings support the potential use of these phytogenic additives as components of health-management strategies in Nile tilapia culture. However, additional studies under commercial production conditions, including dose-optimization, long-term safety assessments, and economic evaluations, are required before practical application can be recommended.
The search for welfare-improving anaesthetic alternatives to MS-222 has highlighted monoterpenes. However, their long-term behavioural consequences remain unclear. This study evaluated the 24-h post-anaesthetic behavioural effects of menthol and thymol compared to MS-222 and eugenol in adult zebrafish. Fish were randomly assigned to six groups. Individual fish (n = 10/group) were maintained for 10 min in MS-222 (150 mg/L), eugenol (80 mg/L), menthol (50 mg/L) and thymol (25 mg/L) or a control (water and ethanol (EtOH) 0.1%) after Stage 3 anaesthesia was reached. Twenty-four hours post-exposure, fish were tested in comprehensive behavioural approach, assessing exploratory and locomotor activity, anxiety-related responses, aggression, shoaling, social preference, and learning and memory, complemented by principal components analysis and hierarchical clustering to characterise treatment-specific behavioural phenotypes. The results revealed compound-specific behavioural profiles 24 h after anaesthesia. MS-222 and eugenol were primarily associated with alterations in anxiety-related and exploratory endpoints, whereas menthol and thymol were mainly associated with consistent modulations of social-related behaviours. Behavioural phenomics further indicated clustering between MS-222 and menthol, while thymol displayed a distinct behavioural profile and eugenol clustered closer to control groups. Overall, the findings highlight that anaesthetic agents are associated with distinct and lasting behavioural profiles in fish, underscoring the importance of considering post-anaesthetic behavioural outcomes when selecting anaesthesia protocols. Further studies are warranted to refine the application of monoterpene-based anaesthetics across different experimental and applied contexts.
Microalgae offer a nutritionally robust alternative to fishmeal and fish oil, helping reduce pressure on wild stocks and supporting more sustainable aquafeed production. This study explored the potential of replacing fish oil with Tetraselmis (Tetraselmis chui) microalgae biomass in the diet of juvenile rainbow trout (89.0 ± 1.10 g) (Oncorhynchus mykiss), assessing its effects on the fish's health. A control diet containing 53% crude protein and fish oil (FO) was modified by replacing FO with Tetraselmis at three graded inclusion levels: 33% (Tetra33), 66% (Tetra66), and 100% (Tetra100). The 84-day feeding trial evaluated key growth parameters, biochemistry, liver and intestinal histo-architectures, and immune-antioxidant gene expression profiles of the experimental fish. Time-series analyses of growth performance revealed no significant treatment effects from day 14 to day 70, except at the 84-day biomass sampling. The FO (7321.65 ± 60.03g) attained a significantly greater final weight (FW) than Tetra33 (6984.70 ± 86.15g) and Tetra100 (6823.93 ± 160.42g), while remaining statistically similar to Tetra66 (7051.77 ± 107.30g). Likewise, weight gain (WG) of the FO group (5519.65 ± 57.16g) exceeded that of the Tetra100 group (5043.93 ± 142.09g) but did not differ significantly from the Tetra33 (5220.70 ± 73.95g) and Tetra66 (5281.77 ± 110.86g). The feed conversion ratios (FCRs) and specific growth rates (SGRs) of the Tetra groups were comparable to the FO control. Dietary variation did not elicit significant changes in leukocyte distribution, biochemical indices, or gene expression patterns across Tetra groups relative to the FO. Similarly, the histological analysis revealed that Tetraselmis dietary inclusions did not trigger inflammatory reactions in hepatic or intestinal tissues in the Tetra groups compared to the FO. Minor but inconsequential histological modifications were noted, such as moderated sinusoid dilation in the liver and slight changes in intestinal villi of Tetra33 fish. Health biomarker analyses indicated that replacing fish oil with Tetraselmis preserved physiological homeostasis, whereas 66% replacement (Tetra66) yielded the best growth performance compared to FO. However, longer feeding trials are necessary to confirm long-term health and nutritional outcomes.
Insulin-like growth factor 1 (IGF1) is a key somatotropic hormone that controls growth and metabolism, thereby conveying growth status to the reproductive endocrine system. The regulation of gonadotropin-releasing hormone (GnRH) to synthesize and release both the gonadotropin hormones (FSH and LH) is well documented. Numerous attempts have been made to understand the interaction of gonadotropic (reproductive) and somatotropic (growth) axis, but the dynamics of their interaction are still not clear at the pituitary level among teleost. The present study bioinformatically demonstrated protein-protein interaction of IGF1 with the proteins of both somatotropic and gonadotropic axes suggesting a cross-talk between them. In vitro, the effects of IGF1 alone or in combination with GnRH on pituitary transcripts for follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were examined. Experiments were conducted with dispersed pituitary cells of the catfish, Heteropneustes fossilis, to determine the time- and dose-dependent response of IGF1 and GnRH alone or in combination to assess fshβ and lhβ. The results showed a time-dependent effect with maximum transcripts level at 1 h of exposure. IGF1 and GnRH showed dose-dependent effects on differential expression of both transcripts when administered alone, with maximum fshβ and minimal lhβ levels at the higher dose. A synergistic impact on both the transcripts was observed in the presence of IGF1 and GnRH. Collectively, the study suggests that IGF1 plays a crucial role in regulating the synthesis of hormones in the catfish by interacting between the gonadotrophs and somatotrophs at the pituitary level.
A cell line from Korean rockfish, Sebastes schlegelii muscle was successfully established and characterized. Primary cultures were initiated by enzymatic digestion and maintained in Leibovitz-15 (L-15) medium supplemented with 20% fetal bovine serum (FBS). The cells were continuously sub-cultured and maintained in L-15 with 10% FBS, 10 ng/mL fibroblast growth factor-2 (bFGF), and 1% antibiotics (penicillin/streptomycin and antibiotic/antimycotic solution) for more than 60 passages over 10 months, and named Korean rockfish muscle Sebastes schlegelii-1 (KRMSS-1) cell line. Under experimental conditions, best growth was achieved at 24 °C with 20% FBS concentration and 10 ng/mL bFGF addition. Cryopreservation using 5% dimethyl sulfoxide (DMSO) resulted in an 85-90% recovery rate after three months of freezing. Amplification of a CO1 fragment of the expected size provided supporting evidence for the rockfish origin of the KRMSS-1 cell line. Myogenic capacity was checked following serum reduction to 2% horse serum, resulting in myocyte alignment and cell fusion. During progression of the differentiation process, myosin heavy chain (MyHC) immunofluorescence staining revealed positive fluorescence distributed along elongated and enlarged cytoplasmic regions, indicating myogenic capacity. Differentiation success was further confirmed by increased protein expression of myogenin, desmin, and MyHC. Activation of intracellular PI3K/Akt/mTor and MEK/ERK pathways suggest a potential association between pathway activation and the differentiation process. Lastly, an increased proportion of cells in the G0/G1 phase at day 3 post-induction confirmed cell-cycle withdrawal. Collectively, this study established a new teleost muscle cell line with myogenic potential, providing a new model for muscle cell physiology research and for future aquaculture biotechnology applications.
Zebrafish are an effective animal model widely utilized in biomedical research. They are known for their rapid reproduction and substantial genetic similarity to humans. Their transparent embryos directly enable the visualization of developmental processes and disease progression. This makes zebrafish invaluable for studying a broad range of human diseases, including cancer, cardiovascular disorders, and neurodegenerative conditions. Compared with other vertebrate models, zebrafish offer several advantages, including ease of genome editing, cost-effective maintenance, and suitability for high-throughput drug screening. Recent advancements have expanded the use of zebrafish in disease modeling and regenerative medicine, providing deeper insights into the genetic and cellular mechanisms underlying human pathologies. Zebrafish provide a robust platform for evaluating the safety, efficacy, and regenerative potential of both natural and synthetic biomaterials, including hydroxyapatite, bioactive glass nanoparticles, and bioceramics. This capability facilitates the creation of artificial tissues that closely resemble native structures. Additionally, integrating artificial intelligence technologies has improved automated data analysis and phenotyping in zebrafish studies, enhancing both accuracy and throughput. This review highlights current applications of zebrafish in disease modeling, drug discovery, regenerative medicine, and biomaterial assessment, emphasizing their evolving role as a versatile preclinical platform supported by advanced genetic and computational tools.
The current study aimed to assess the potential biological and cellular impacts of dietary supplementation with chitosan-flaxseed oil nanocomposite (CFN) in boosting the growth performance indices, digestive enzyme activity, innate immune capacity, economic significance, gene expression, and histopathological alterations in the Nile tilapia exposed to chronic cold stress. Nile tilapia were distributed into six experimental groups, the first three groups were reared under optimum water temperature (25 °C) and fed 0 mg/kg CFN (control), 20 mg/kg CFN or 40 mg/kg -incorporated diets, respectively. However, the other three groups were reared under cold stress conditions (18 °C), and received the same previously mentioned diets, respectively. Growth performance and economic significance analysis were monitored throughout the experiment. Serum and tissue samples were collected after 60 days to evaluate immune indices (lysozyme, nitric oxide, and IgM), glucose, growth hormone (GH), digestive enzymes (amylase and lipase), gene expression (interleukin-8, tumor necrosis factor-alpha, interleukin-1ß, lysozyme-G, lysozyme-C, transforming growth factor-beta, nuclear factor kappa β, myeloperoxidase, and Toll-like receptor-5, and glutathione perioxidase-1), and histopathological changes. A subsequent bacterial challenge with Pseudomonas aeruginosa was carried out, where the clinical disorders and mortalities were monitored. The outcomes showed remarkable declines in various growth metrics, immune variables with dysregulation in the immune-linked genes in fish exposed to chronic cold stress circumstances, compared to fish reared at optimum temperature. Nonetheless, dietary intervention with CFN mitigated the negative impacts induced by cold stress exposure, where the growth, immune indices, and digestive enzymes were notably enhanced in the supplemented groups in relation to the non-supplemented group. The histopathological alterations in the intestine and spleen were also markedly alleviated. Additionally, the expression profiles of both inflammatory cytokines and apoptosis were positively modified. Furthermore, fish resilience to P. aeruginosa infection was triggered, which was evident by the amelioration of the clinical signs and declining mortality rates in CFN-enriched groups. Taken together, CFN is a promising antibacterial dietary additive which promotes the growth, health, and performance of the Nile tilapia.
Steroid hormones play a pivotal role in fish sex differentiation, yet the dynamic expression patterns of key steroidogenic enzymes during this process remain incompletely characterized. Here, we combined genome-wide identification, time series transcriptomes spanning gonadal development (5-360 days post-hatch), and multiple hormone treatment experiments (17α-methyltestosterone, estrone, and etonogestrel) to investigate the Cyp11, Cyp17, Cyp19, and Cyp21 subfamilies in mandarin fish (Siniperca chuatsi). Seven steroidogenic Cyp genes were identified, showing teleost-specific expansion, with one duplicated pair (cyp17a2 and cyp2u1) exhibiting strong purifying selection. Expression profiling revealed pronounced sexually dimorphic and stage-specific patterns: During female differentiation (20-30 days), cyp19a1a and associated genes were highly expressed, coinciding with ovarian differentiation; during male differentiation (30-60 days), cyp17a2 and related genes were upregulated, aligning with testicular development. Exogenous hormone treatments further demonstrated that these genes are dynamically responsive: cyp19a1a and cyp17a2 were highly responsive to androgenic and progestogenic treatments, and their expression changes correlated closely with gonadal sex reversal phenotypes observed histologically. Collectively, this study provides a comprehensive expression atlas of steroidogenic Cyp genes during gonadal differentiation and identifies key hormonally responsive candidates for sex control in aquaculture.
Nicotine induces pronounced neural and behavioral activation through dopaminergic signaling. However, the underlying molecular mechanisms that regulate nicotine sensitivity remain poorly understood. Here, we investigated the roles of lysosomal sialidase Neu1 and neural glycan polysialic acid (PSA) in nicotine-induced responses in zebrafish, a vertebrate model. Western blot analyses revealed reduced PSA levels and significantly upregulated neu1 expression in the zebrafish brain following acute nicotine exposure. Behavioral assays revealed increased tolerance to nicotine-induced lethality and attenuated nicotine-evoked swimming excitation in neu1-knockout (neu1-KO) zebrafish compared with those in wild-type fish. Nicotine-induced neuronal activation, assessed based on c-Fos expression, was markedly reduced in neu1-KO zebrafish. Gene expression analyses revealed altered dopaminergic signaling, including reduced drd3 expression, in neu1-KO zebrafish. Pharmacological experiments demonstrated that blocking dopamine D2/D3 receptors suppressed nicotine-induced swimming excitation in wild-type zebrafish, whereas treatment with a selective dopamine D3 receptor agonist partially rescued the attenuated nicotine responsiveness observed in neu1-KO zebrafish. Nicotine-induced c-Fos activation occurred predominantly in PSA-positive neurons within the hypothalamus, a brain region implicated in dopaminergic signaling. These findings suggest that Neu1-mediated PSA degradation may modulate dopamine D3 receptor-dependent nicotine sensitivity. We propose a conceptual model wherein nicotine-induced Neu1 activation may contribute to reduced PSA levels and altered dopamine D3 receptor-related signaling, thereby influencing the threshold for nicotine-induced neural and behavioral activation.
This study represents a pioneering investigation into the protective role of dietary grape seed oil nanoemulsion (GON) against acrylamide (AC)-induced growth impairment, oxidative stress, immunosuppression, gene expression dysregulation, and histopathological damage in Nile tilapia (Oreochromis niloticus). A total of 240 fish were randomly allocated into six experimental groups (four replicates each). The control, GON20, and GON40 groups received basal, 20 and 40 mg/kg GON-supplemented diets, respectively, without AC exposure. The AC, AC + GON20, and AC + GON40 groups were exposed to waterborne AC at 1/8 of the 96-h median lethal concentration (4.33 mg/L) for 45 days while receiving the corresponding diets. Growth performance, immune and oxidative stress biomarkers were assessed, alongside splenic cytokine expression and histopathological alterations. AC exposure significantly reduced growth parameters (p < 0.0001), including weight gain and specific growth rate, and induced pronounced immunosuppression and oxidative stress, evidenced by decreased lysozyme activity, complement 3, total protein, catalase, superoxide dismutase, and glutathione peroxidase activities, concomitant with elevated malondialdehyde levels. Severe inflammatory and necrotic lesions were observed in intestinal and splenic tissues. Furthermore, AC significantly downregulated (p < 0.0001), the expression of interleukin-6, interleukin-8, cathepsin-B, and nuclear factor erythroid 2-related factor 2, increasing cellular susceptibility to toxic and oxidative insults. Conversely, GON supplementation significantly improved growth performance, immune competence, and antioxidant capacity in a dose-dependent manner, accompanied by marked upregulation (p < 0.0001), of IL-6, IL-8, cathepsin-B, and NRF2 expression. These molecular modulations were associated with substantial histological recovery of intestinal and splenic architecture, with near-complete restoration observed in the AC + GON40 group. Collectively, these findings highlight GON as a promising multifunctional dietary additive capable of mitigating acrylamide-induced toxicity and enhancing physiological resilience in Nile tilapia as a valuable fish in aquaculture practice.
This study investigated the effects of dietary sodium butyrate supplementation on Nile tilapia, with emphasis on growth performance, biochemical alterations, histological characteristics, and gene expression patterns under both normal conditions and glyphosate exposure. A total of 90 Nile tilapia with an initial mean body weight of 7.93 ± 0.026 g were randomly allocated into two experimental groups, with each group comprising three replicate units. The control group was fed a basal diet, while the second group received 1.5 g/kg of sodium butyrate mixed into their food for 8 weeks. Afterward, each group was further divided into two: one without any challenge and the other exposed to 0.6 mg/L GLY. The findings indicated that fish fed with SB exhibited a significant improvement (p < 0.05) in final body weight (FBW), weight gain percentage (WG %), specific growth rate (SGR), protein efficiency ratio (PER), and survival rate, along with a reduction in feed conversion ratio (FCR) compared to the control group. Additionally, there was an enhancement in hepatic antioxidant capacity, along with a downregulation of hepatic ilgf1bp and myostatin. Fish subjected to GLY displayed the highest activities of ALT and AST, elevated levels of BUN and creatinine, and a decrease in lysozyme activity. Sodium butyrate supplementation mitigated glyphosate-induced hepatic and renal impairment and regulated the mRNA expression of intestinal tight junction-associated and apoptosis-related genes. These findings suggest that dietary sodium butyrate may be used as a promising alternative feed additive in sustainable Nile tilapia aquaculture. Its inclusion could help protect fish against glyphosate-associated stress, improve growth performance, enhance antioxidant and immune-related biochemical responses, and provide anti-inflammatory and anti-apoptotic benefits under both basal conditions and following glyphosate exposure.
Bacteria and viruses engage in complex synergistic and antagonistic interactions with profound implications for host health, particularly through functional modulation by intestinal and other mucosal (e.g., skin, gill) microbiota. In teleost models, intestinal microbiota demonstrates dual regulatory capacities-either potentiating or suppressing viral infections. However, the mechanistic underpinnings of these interactions remain inadequately explored in aquatic species. This review systematically delineates the dual regulatory pathways (facilitative vs. inhibitory) through which the gut microbiota modulates viral infections in fish. Based on these mechanisms, we propose a novel microbiota-gut-immunity axis framework-defined as the bidirectional communication network linking gut microbial communities, intestinal barrier function, and host systemic immunity-for the development of integrated antiviral interventions. Furthermore, we critically evaluate emerging strategies-including probiotics, prebiotics, postbiotics, synbiotics, fecal microbiota transplantation (FMT), microalgae, seaweed, and phytoactive compounds-to develop preventive and therapeutic countermeasures. Based on mechanistic insights, probiotics and prebiotics emerge as the most promising candidates for large-scale application, as they directly reshape gut microbial composition and enhance host immunity along the microbiota-gut-immunity axis. In contrast, FMT and herbal medicines, while acting on multiple nodes of the axis, currently face safety and standardization challenges, positioning them as adjunctive therapies. Importantly, these mechanistic insights reveal evolutionarily conserved immune pathways with significant translational potential for human virology.
A 28-day study was conducted to examine the effects of photoperiods with multiple light/dark cycles on growth performance and oxidative stress for largemouth bass (Micropterus salmoides) larvae in recirculating aquaculture systems (RAS). Larvae fish were exposed to four different photoperiods [light/dark (L:D), h] as follows: 6L:18D; 12L:12D; 18L:6D and 24L:0D. The feeding number was 8 times a day. The light duration of each treatment was 45 min, 90 min, 135 min and 180 min respectively in one light/dark cycle (feeding interval) of 180 min. A total of six thousand fish (0.5229 ± 0.0180 cm, 0.0021 ± 0.0002 g) were randomly kept in the 12 cages (4 treatments × 3 replicates × 500 individuals). The results showed that the body weight, weight gain rate (WGR), specific growth rate (SGR), thermal growth coefficient (TGC), Fulton's condition factor (K) and mRNA expressions of growth hormone (gh) and insulin-like growth factor 1 (igf-1) generally increased with the extension of photoperiods, and they were highest in the 24L:0D treatment and were second in the 18L:6D treatment. The variation coefficients for body length (CVfl) and body weight (CVfw) were lowest in 18L:6D treatment. There was no significant difference in survival rate (SR) among four treatments. The levels of Malonaldehyde (MDA), total antioxidant capacity (T-AOC) and mRNA expressions of heat shock protein 70 (hsp70), corticotropin-releasing factor receptor 1 (crfr1) and caspase-3 (cas-3) were all significantly higher in 6L:18D and 24L:0D treatments than those of 18L:6D and 12L:12D treatments. This indicated the photoperiods of 6L:18D and 24L:0D regimes induced an oxidative stress response in the larvae when the photoperiods were excessively compressed and extended. Overall, 18L:6D treatment is the optimal light regime for largemouth bass larvae culture in RAS. However, experimental comparisons between cyclic light/dark and continuous regimes are warranted to further evaluate animal welfare implications and inform aquaculture practice.
A serious mortality epizootic affected the populations of common carp (Cyprinus carpio L.) in several fish farms that are located at Al-jadeda-Diyala province, Iraq, during the autumn 2022. The diseased fish were showing clinical signs associated with a viral cause. To conduct molecular detection using polymerase chain reaction (PCR) to examine the carp interstitial nephritis and gill necrosis virus (CNGV) outbreak, and characterize histopathological changes in major organs, as well as serum liver enzyme profile and kidney function profile. A total of 50 live common carp (Cyprinus carpio L.) with weight of 128 to 2,300 g that showed clinical signs such as necrosis on the gills, overproduction of mucus, or pallor in the skin were randomly sampled from five positive farms. Blood samples were obtained from the caudal vein for measurement of the level of biochemical liver enzymes (alanine transaminase and aspartate amino transferase) markers for kidney function (creatinine). At 15 d postimmunization, fish (n = 3) from each group were euthanized, and tissues (gill, liver, spleen, kidney, and intestine) were aseptically removed. Hematoxylin/eosin-stained histopathology tissues were processed by routine methods after fixation with 10% neutral buffered formaldehyde. Gill tissue was maintained in phosphate-buffered saline for DNA extraction and PCR amplification to a region of the conserved genome between CNGVs for molecular analysis. The positive presence of CNGV in the fish samples was confirmed by PCR. Histopathological analysis showed extensive lesions in all the analyzed organs, such as severe gill necrosis, hepatitis, splenitis, extensive interstitial nephritis, and enteritis. They were associated with marked increases in serum liver enzyme activities and alterations of renal end-points. This is the first molecular confirmation of CNGV infection as the cause of an outbreak of disease in common carp in Iraq. The virus caused severe systemic lesions with characteristic histopathological alterations in major organs and remarkable hepatic and renal function impairment. These results bring CNGV as a serious new threat to carp farming in the region.
The photoperiod, an essential environmental factor influencing the growth, reproduction, and physiological functions of teleosts, exhibits effects that are highly species-specific. This study investigates the impact of five distinct photoperiod treatments on the growth performance, gonadal development, and hypothalamic-pituitary-gonadal (HPG) axis regulation in Phoxinus lagowskii, a high-latitude cold-water fish with significant aquaculture potential. Through comprehensive analyses of growth indices, serum sex hormone levels, gonadal histology, and gene expression, we demonstrate that photoperiod significantly affects the physiology of P. lagowskii. Females exhibited optimal growth and gonadal development under a 16L:8D photoperiod, with increased expression of key genes (gnrh2, gnrh3, kiss1, kiss2, cyp19a1, and foxl2) and elevated levels of gonadotropins (Fsh, Lh) and estradiol (E2). In contrast, males showed enhanced reproductive performance under an 8L:16D photoperiod, characterized by higher testosterone (T) levels and upregulated expression of dmrt1 and sox9a. The inverse relationship between the hepatosomatic index (HSI) and gonadosomatic index (GSI) suggests an energy trade-off between hepatic energy reserves and reproductive investment. Moreover, melatonin further regulates the HPG axis by affecting the synthesis and release of GnRH and kisspeptins, highlighting its role in mediating photoperiodic effects on reproduction. These findings underscore the sex-specific responses of P. lagowskii to photoperiod and provide critical insights into the physiological mechanisms underlying photoperiod regulation in cold-water fish. This study offers practical strategies for optimizing aquaculture practices to enhance growth and reproductive efficiency.
The rapid expansion of global aquaculture has increased fish exposure to multiple xenobiotics, including agricultural chemicals, industrial pollutants, and emerging contaminants such as microplastics. Although numerous studies have examined individual toxicants, a critical knowledge gap remains regarding integrative, nutrition-based detoxification strategies that simultaneously mitigate oxidative stress, enhance endogenous detoxification pathways, and reduce dependence on chemical therapeutics. This review addresses the question of how bioactive feed additives can be strategically used to support physiological detoxification mechanisms in fish exposed to complex xenobiotic mixtures. The review synthesizes current evidence on phytogenic compounds, functional amino acids, trace elements, and advanced delivery systems that activate antioxidant defense systems, phase I and phase II detoxification enzymes, and cellular repair processes. Particular emphasis is placed on molecular pathways such as nuclear factor erythroid 2-related factor 2 signaling, species-specific detoxification capacity, and the interaction between nutrition, gut microbiota, and immune function. Comparative evidence across major aquaculture species demonstrates that nutritional detoxification strategies can improve resilience to oxidative damage while contributing to reduced antibiotic use and improved product safety. By integrating mechanistic insights with One Health and sustainability perspectives, this review highlights nutritional detoxification as a scalable and environmentally responsible approach for managing xenobiotic stress in modern aquaculture systems.
Dietary curcumin supplementation has been shown to improve growth, antioxidative and anti-inflammatory status in different fish species. Yet, studies focusing on its effect during the early developmental stages of fish remains limited. The recent study aimed at assessing the effect of dietary curcumin supplementation at different levels on the growth performance, antioxidant enzymes and immune response of seabass larvae (Dicentrarchus labrax). To this end, seabass larvae were reared from 21 to 60 days after hatching, feeding on a standard feeding regime (CONTROL) and diets where LOW, medium (MED) and HIGH curcumin levels were supplemented. Fish were analyzed at the end of the experimental period for biometrical parameters, immune-related genes and activity of antioxidant-related parameters. At the end of the trial, fish from the HIGH treatment had a significantly higher dry weight than fish from the CONTROL, although no significant differences were observed for fish survival. Curcumin supplementation did not affect isolated antioxidant parameters, such as catalase activity, superoxide dismutase, and lipid peroxidation, glutathione peroxidase, but a multivariate analysis where these parameters were included unraveled a significant difference between treatments CONTROL and HIGH in the overall growth, antioxidant and immune response. Furthermore, a significant reduction of Immunoglobulin M (IgM) was found in treatments MED and HIGH in comparison to CONTROL, indicating the modulation of this parameter in seabass larvae may be dosage dependent. In conclusion, dietary curcumin supplementation at HIGH level was able to improve seabass weight and increase its overall health status during the early developmental stages.
Triclosan (TCS), an antimicrobial agent widely incorporated in personal care products, has become a persistent aquatic contaminant, posing potential risks to freshwater organisms. This study examined sub-lethal TCS toxicity in Labeo rohita, demonstrating its capacity to disrupt oxidative balance, hematology, antioxidant defenses, and induce multi-organ damage. Fish were exposed for 6 weeks to two concentrations of TCS: 0.0742 mg/L (T1) and 0.148 mg/L (T2), representing one-tenth and one-fifth of the 96-h LC₅₀, respectively, under semi-static conditions. At each sampling interval, one fish from each replicate tank was sampled for biochemical, histopathological, and qRT-PCR analyses (n = 3 biological replicates per treatment group). TCS exposure induced significant (p < 0.05), dose- and time-dependent oxidative stress, evidenced by increased reactive oxygen species (ROS), reduced hemoglobin (Hb) and red blood cells (RBCs), and elevated white blood cells (WBCs). Antioxidant responses showed increased superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (LPO) and decreased reduced glutathione (GSH), following the organ-specific severity order: gill > kidney > muscle. Gene expression analysis via qRT-PCR indicated a clear shift in autophagy-related markers, showing elevated levels of atg5, beclin1, lc3, and ulk1b, along with reduced mTOR expression, suggesting enhanced autophagic activity under TCS-induced oxidative stress. The response displayed tissue-specific variation, with gill showing the greatest sensitivity, followed by kidney and muscle. Histopathological damage increased dose-dependently: T1 showed mild gill, kidney, and muscle lesions, whereas T2 exhibited severe gill oedema and aneurysm, marked renal degeneration, and extensive muscle fiber disruption. Pearson correlation analysis showed strong links among oxidative stress, hematological alterations, antioxidant responses, and alterations in gene expression. Altogether, TCS induced clear dose-dependent toxicity in L. rohita, highlighting its significant chronic ecological risk to freshwater systems even at low concentrations.