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An experiment was conducted to mitigate mercury and ammonia toxicity (Hg + NH₃) in Oreochromis niloticus (GIFT strain) using selenium nanoparticles (Se-NPs). The Se-NPs were synthesized using green methods, employing fish waste as the substrate. Experimental diets were prepared by supplementing Se-NPs at 0, 0.3, and 0.6 mg kg⁻¹. The oxidative stress enzymes, including catalase (CAT) and glutathione peroxidase (GPx), in the liver and kidney tissues were significantly reduced by Se-NPs at 0.3 and 0.6 mg kg⁻¹ under Hg + NH₃ stress compared to the control and stressor in 20 and 40 day periods. Additionally, superoxide dismutase (SOD) activity in the kidney at 20 days and in the liver at 40 days was significantly reduced by supplementation of Se-NPs under similar conditions. The activity of acetylcholine esterase (AChE), was significantly inhibited by Hg + NH₃ toxicity. Whereas, AChE activity was enhanced by Se-NPs supplementation at 0.3 and 0.6 mg kg⁻¹ during 20 and 40 day intervals. The gene expression of HSP70, iNOS, CYP450, Caspase-3a, and TNFα in liver tissue, and MYST in muscle tissue was upregulated by Hg+NH₃ toxicity. However, this upregulation was significantly downregulated by supplementation of Se-NPs at 0.3 and 0.6 mg kg⁻¹ under Hg + NH₃ stress. Moreover, immunoglobulin (Ig) and growth hormone (GH) levels were noticeably upregulated with Se-NPs compared to the control and Hg+NH₃ stress. The activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) in liver and gill tissues, were significantly elevated by Hg+NH₃ toxicity, were reduced by Se-NPs diet. Conversely, digestive enzyme activities, including protease, amylase, and lipase, were significantly enhanced by Se-NPs under stress conditions. Dietary supplementation with Se-NPs at 0.3 and 0.6 mg kg⁻¹ improved growth performance parameters such as final weight gain percentage, feed conversion ratio, protein conversion ratio, specific growth rate, daily growth index, and relative feed intake compared to the control and other groups. DNA damage, assessed in terms of tail DNA percentage, was significantly reduced with Se-NPs supplementation. Additionally, mercury detoxification was significantly enhanced with Se-NPs-supplemented diets. In conclusion, this study demonstrates that dietary Se-NPs effectively alleviate the adverse effects of mercury and ammonia toxicity by modulating antioxidant status, enhancing immunomodulation, and mitigating stress biomarker impacts through changes in gene expression in fish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

Warming events are becoming more frequent and extreme in aquatic environments worldwide. Concurrently, many environments are polluted with biologically active compounds such as pharmaceuticals. Understanding how these challenges interact is critical for understanding the climate crisis, as contaminants may modulate how ectotherms respond to heat stress or vice versa. One potential site for these heat × contaminant interactions is the mitochondrion, which is central to metabolism, implicated in thermal tolerance, and evolutionarily conserved. Using high-resolution respirometry, we investigated how acute warming (to 35 °C, 40 °C, or 45 °C from 25 °C) impacted the respiration, coupling, and metabolic capacity of liver mitochondria isolated from Nile tilapia, and how exposure to environmentally relevant levels of the ubiquitous antidepressant venlafaxine modulated those effects. Mitochondria exposed to hotter temperatures had higher respiration rates and decreased respiratory control ratio compared to mitochondria exposed to cooler temperatures. The depressive effects of venlafaxine on respiration rates through complex I and II or complex II only (State 3 and State 4), as well as complex IV-linked respiration, were mild except in mitochondria exposed to high temperatures, suggesting an interactive effect of warming and contaminant exposure. Finally, we found that the maximal enzyme activity of intact mitochondria (represented by mitochondrial respiration) showed a different pattern of response to warming and venlafaxine compared to its underlying components (as reflected by the activity of succinate dehydrogenase [complex II] and cytochrome c oxidase [complex IV]), demonstrating the value of incorporating both interactive and reductive approaches in understanding how mitochondria cope with anthropogenic changes in the environment., (© The Author(s) 2025. Published by Oxford University Press on behalf of the Society of Environmental Toxicology and Chemistry.)

The pace of research efforts has been extraordinarily accelerated across the globe to address the contamination issues caused by pesticides, and fertilizers, especially in the aquatic ecosystem. The sole aim of this study was to assess the effect of urea on Nile tilapia (Oreochromis niloticus). For this purpose, the fish fingerlings were exposed to increasing concentrations of urea such as 0, 1, 2.5, 5, 10, 20, and 40 g/l for 72 h. Survival analysis suggested a strong correlation between the increasing doses of urea and the mortality rate among tested fingerlings. This study reported remarkable morphological, and behavioural alternation such as increased operculum movement, bottom-dwelling, lethargy, secretion of mucus, reduction in food intake, and bleeding in the fin and around the mouth in the treated group. Haematological analysis revealed that a significant reduction in RBC count and Hb along with an increase in WBC number is associated with urea toxicity. Our study showed a significant rise in glucose concentration upon urea toxicity in Nile tilapia fingerlings for the first time, emphasizing the adverse effect of fertilizers on carbohydrate metabolism. Significant rises in the enzymatic activity such as alanine aminotransferase (ALT), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) upon urea treatment emphasize the possibilities of liver damage, biliary obstruction, and abnormal glucose metabolism. Histological analysis of urea-treated fish compared to normal fish revealed that urea toxicity drastically altered the tissue architecture of fish's gills, eyes, intestine, and stomach. As the visual systems of mammals and fish resemble in more aspects, our findings may be useful in understanding the impact of pollutants on sensory organs concerning humans. We conclude that our findings highlight the importance of urea toxicity on Nile tilapia fingerlings and invite multidisciplinary research to uncover molecular mechanisms underlying urea toxicity., Competing Interests: Declaration of competing interest I have nothing to declare., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

Hexavalent chromium (Cr (VI)), a toxicant of environmental concern, frequently enters into water bodies and produces oxidative stress in fish. The antioxidant enzymes, Superoxide dismutase (SOD), Catalase (CAT), and Glutathion S-transferase (GST) are activated to counteract the oxidative stress in fish. This study explores the pattern of activation of these enzymes in gill, muscle, liver, and kidney tissues of Nile tilapia Oreochromis niloticus exposed to 9.35 mg/L and 18.70 mg/L of Cr (VI) for 96 h. The optimal hour of activity of these enzymes was revealed through extensive regression analysis. The results indicate a bell-shaped time response curve in the activity of the enzymes in both the treatments, except CAT in the gill of fish exposed to 18.70 mg/L Cr (VI) and GST in the gill, liver, and kidney of fish exposed to 18.70 mg/L Cr (VI). The results indicate that the optimal hour of activity of SOD changes in tandem with CAT, SOD responding first followed by CAT, both diminishing within 96 h. However, deviating from the bell-shaped pattern, the activity of CAT in gill and GST in gill, liver, and kidney in fish exposed to 18.70 mg/L Cr (VI) continued to rise even at 96 h, indicating that these antioxidant enzymes could not diminish the oxidative stress produced by the higher dose of Cr (VI). It was concluded that the activity of SOD, CAT, and GST between 30 and 70 h in the gill, liver, and kidney of Nile tilapia could serve as excellent biomarkers of oxidative stress under low doses of Cr (VI)., Competing Interests: Compliance with ethical standards. Conflict of interest: The authors declare no competing interests. Ethical approval: All authors have read, understood, and have complied as applicable with the statement on “Ethical responsibilities of Authors” as found in the Instructions for Authors. The authors declare that fish samples were handled as per the animal care protocol of the West Bengal State University, and the methods used to analyze Cr concentration in fish tissues were carried out in accordance with relevant national and international guidelines and regulations., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Genetically improved farmed tilapia (GIFT) is a strain of Nile tilapia (Oreochromis niloticus) developed for improved production and commercial parameters. Skin color, one of the characteristics distinguishing tilapia varieties, is an important phenotypic trait associated with qualitative and productive performance. This study aimed to assess fillet and skin characteristics in GIFT Nile tilapia with black and red skin phenotypes. For this, 24 GIFT Nile tilapia from the same spawning stock were divided into two groups based on skin color, namely a black variety (dark skin) and a red variety (reddish skin). There were no significant differences in biometric parameters between varieties. Fish of the red variety had higher 2 h post-slaughter pH and muscle antioxidant capacity and lower yellow-blue axis value (b*), luminosity (L*), thawing loss, cooking loss, and conjugated diene content (P < 0.05). The skin of black tilapia exhibited higher force in the progressive tear test tear, and higher strength, tensile strength, deformation, and elongation in the traction and stretching test than that of red tilapia. Black tilapia skin had higher collagen and hydroxyproline contents. The skin of the red variety exhibited higher expression levels of alpha 1, 2, and 3 type I collagen genes, lower expression levels of the vimentin gene, and higher antioxidant capacity. The results suggest that skin color phenotype may be linked to important metabolic pathways influencing fish fillet and skin traits. These findings can support future research aimed at identifying optimal varieties of Nile tilapia for specific purposes and optimizing the utilization of filleting waste., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2025 Campos et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Nile tilapia has become one the most significant species in global aquaculture due to its exceptional adaptability, rapid growth and high reproductive capacity. Role of Sox genes in reproduction and development made attention to further investigate the role of these genes. Based on N. tilapia importance in aquaculture industry and role of Sox genes in the development of tissues and organs during embryogenesis, this study systematically analyzed Sox genes functionality in N. tilapia by using computational tools. In our study, phylogenetic analysis revealed that N. tilapia is most closely related to blue tilapia compared to other species. Sox genes are conserved in nature and share both acidic and basic properties as well as thermostable and hydrophobic in nature. The subcellular localization in N. tilapia indicated that majority of the Sox proteins are expressed in the Nucleus and Cytoplasm. Enrichment analysis explains the Sox genes' role in cell differentiation, and biosynthesis process and acts as a molecular functional regulator. Significant differences in transcription binding sites were observed, highlighting the potential role of these regulatory regions in the regulation of Sox genes in N. tilapia. First time it is reported that Sox genes in N. tilapia have four major recombinant breakpoints that revealed phylogenetic segregation across several recombination fragments. In this primer, we aim to provide the reader with a comprehensive overview of Sox gene family in N. tilapia and to provide the functional properties of Sox genes for better follow-up in upcoming experiments for futuristic research.

This study evaluated the effects of Biocide, containing silicon tetrahedrons and organic acids, on growth performance, feed utilization, immune response, and oxidative status in Nile tilapia (Oreochromis niloticus). A total of 300 Nile tilapia fingerlings (initial weight: 3.55 ± 0.01 g) were distributed across 15 tanks and fed diets containing 0.0 (control), 0.25, 0.5, 1, and 2 g kg⁻¹ Biocide for 90 days, with three replicate tanks per treatment. Biocide is enriched with organic acids (fumaric acid and citric acid) and amino acids (glutamine, tyrosine, methionine, serine, and threonine). Fish fed Biocide-supplemented diets demonstrated significantly improved growth performance, with the highest weight gain, feed conversion ratio, and protein efficiency ratio observed in the 1 g kg⁻¹ group. Survival rates did not differ significantly among treatments. Whole-body crude protein content peaked in the 1 g kg⁻¹ group, while moisture, lipid, and ash contents remained unchanged. Hematological parameters, including red blood cell count, hemoglobin concentration, and packed cell volume, improved significantly. Serum lipid profiles showed reduced cholesterol, triglycerides, low-density lipoprotein, and very-low-density lipoprotein levels, alongside increased high-density lipoprotein levels, particularly in the 1 g kg⁻¹ group. Antioxidant enzyme activities (catalase, glutathione peroxidase) and total antioxidant capacity were significantly elevated in the liver and intestine, while malondialdehyde levels decreased. Digestive enzyme activities (amylase, lipase, and protease) were markedly enhanced. Histopathological analysis revealed improved liver, stomach, and intestinal morphology, including increased mucous secretion and enhanced intestinal villi structure, in fish fed 1 g kg⁻¹ Biocide. In conclusion, Biocide supplementation, particularly at 1 g kg⁻¹, significantly improved growth performance, feed utilization, immune function, and antioxidant capacity in Nile tilapia. Notably, the findings highlight Biocide's primary mode of action on gut health, underscoring its potential as a dietary additive for improving aquaculture productivity., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethical approval: The study was approved and performed in accordance with the guidelines and regulations set by Agriculture Research Center, Egypt (Approval No. ARC/CLAR/89/24). The animal experiments adhered to the regulations and guidelines of ARRIVE ( https://arriveguidelines.org/ ). Consent for publication: Not applicable., (© 2025. The Author(s).)

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., Competing Interests: Declarations. Conflict of interest: The authors declare no competing interests., (© 2025. The Author(s).)

A feeding trial for 8 weeks was performed to explore whether nutritional supplementation of L-carnitine may minimize the adverse effects of high-fat diet (HFD) on tilapia growth performance, antioxidant, immune parameters, inflammatory response, histopathology of liver, kidney, and intestine, as well as hepatic lipid metabolism aiming to reveal the mechanism and providing a shred of molecular evidence in Nile tilapia (Oreochromis niloticous). Six groups of the Nile tilapia (17.13 ± 0.49 g) in triplicate were fed for 60 days. Six experimental diets were formulated, incorporating different concentrations of L-carnitine. The first three groups were administered a diet comprising 6% fat, with L-carnitine concentrations of 0, 0.5, and 1 g/kg diet was designated as F6Car0, F6Car0.5, and F6Car1, respectively. Moreover, the fourth, fifth, and sixth groups were fed on a diet containing 12% fat, with L-carnitine concentrations of 0, 0.5, and 1 g/kg diet, respectively termed F12Car0, F12Car0.5, and F12Car1. The main results were as follows: compared to the control group HFD caused a significant reduction in BWG and PER (P > 0.05), but significantly increased the feed conversion rate (FCR), hepatosomatic index (HSI), intraperitoneal fat (IPF), as well as increased visceral fat deposits and liver fat accumulation with higher activities of serum aminotransferases, glucose, triglycerides, and cholesterol. HFD exacerbates hepatic lipid accumulation by enhancing lipogenic gene expression. HFD-fed fish exhibited the lowest crude protein and highest crude fat levels. This study demonstrates that dietary supplementation with L-carnitine significantly boosts growth, improves hemato-biochemical parameters, decreases lipogenesis, elevates lipolysis pathway genes, and lowers lipid levels, thereby rebalancing lipid metabolism and lessening hepatic steatosis. It also mitigates inflammation by downregulating pro-inflammatory genes, upregulating immune genes, and positively affecting Nile tilapia's histopathology., Competing Interests: Declarations. Consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2025. The Author(s), under exclusive licence to Springer Nature B.V.)

Plastic pollution and global warming are widespread issues that lead to several impacts on aquatic organisms. Despite harmful studies on both subjects, there are few studies on how temperature increases plastics' adverse effects on aquatic animals, mainly freshwater species. So, this study aims to clarify the potential impact of temperature increases on the toxicological properties of polyvinyl chloride nano-plastics (PVC-NPs) in Nile tilapia (Oreochromis niloticus) by measuring biochemical and oxidative biomarkers. The fish groups were subjected to three distinct temperatures (30, 32, and 34 °C) and subsequently separated into two groups: 0 and 10 mg/L of PVC-NPs, as it is expected that these temperatures may modify their chemical properties, which can influence their absorption and toxicity in fish. After 4 days, the biochemical response of fish exposed to PVC-NPs and elevated temperatures showed a significant increase in the levels of plasma total proteins, albumin, globulin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatinine, and uric acid. Additionally, the level of oxidative stress biomarkers in the liver, gills, and brain was found to have a significant increase in malondialdehyde (MDA) concentration and a decrease in glutathione reduced (GSH) concentration and catalase (CAT) activity in all studied groups. Finally, the current findings revealed a synergistic cytotoxic effect of PVC-NPs and temperatures on the metabolic and oxidative stress indices of O. niloticus., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Oxytetracycline (OTC), an approved antibiotic for aquaculture, is under strict control and regulatory endeavour. This study compared the effects of oral administration of graded doses of OTC comprising the therapeutic (80 mg/kg biomass/day), subtherapeutic (40 mg) and overdoses (240, 400 and 800 mg) in male Nile tilapia Oreochromis niloticus fries (0.64 ± 0.02 g) when fed for 10 consecutive days and observed for 22 days post-OTC-dosing (POD) period. A dose-dependent reduction in food intake, survival and muscle calcium, chloride, malondialdehyde and superoxide dismutase was observed, while the muscle glucose significantly increased. However, the changes were reversible with dose cessation. The fries of the therapeutic dose group recorded the maximum biomass, while the overdosed groups recorded a significant decline in weight gain. On day 10 of dosing, all groups' muscle OTC residues peaked. The residues in the subtherapeutic and therapeutic dose groups were lowered below the maximum residue limit (MRL) of 100 ng/g on day 10 POD. The residues were further reduced close to the MRL in the overdosed groups on day 22 POD. The fries tolerated the therapeutic dose well and showed effective adaptive responses. Considering muscle residue accretion and physiological responses, OTC can be endorsed as a safe drug for in-feed administration to tilapia fries. However, the sensible use of this approved drug is essential for sustainable aquaculture., Competing Interests: Declarations. Ethics approval: The experimental protocols were approved by the Indian Council of Agricultural Research, Government of India, under the All-India Network Project on Fish Health and fulfilled the ethical guidelines including adherence to the regulatory requirement. Consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2025. The Author(s), under exclusive licence to Springer Nature B.V.)

Selective breeding is a potent method for developing strains with enhanced traits. This study compared the growth performance and stress responses of the genetically improved Abbassa Nile tilapia strain (G9; GIANT-G9) with a local commercial strain over 12 weeks, followed by exposure to stressors including high ammonia (10 mg TAN/L), elevated temperature (37 °C), and both for three days. The GIANT-G9 showed superior growth, including greater weight gain, final weight, length gain, specific growth rate, and protein efficiency ratio, as well as a lower feed conversion ratio and condition factor compared to the commercial strain. The expression of growth hormone in the brain of the GIANT-G9 increased significantly after 6 weeks, although it slightly decreased after 12 weeks. Growth hormone receptor 1 expression also increased significantly after 6 weeks. Muscle insulin-like growth factors (igf1 and igf2) levels up-regulated significantly only after 12 weeks in the GIANT-G9. Under stress, serum enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase (ALP)) were significantly higher in the GIANT-G9, while the commercial strain had lower levels. No significant changes were observed in liver ALP activity among stressed strains. Under stress, the GIANT-G9 exhibited marked upregulation of splenic Toll-like receptors (tlr2, tlr9, tlr21), myeloid differentiation primary response protein 88 (myd88), nuclear factor kappa B (nf-κB), interleukin (il) 1β, and il6. Notably, il6 expression was higher than il1β in the spleen, with the opposite pattern in the head kidney. In response to immune stimulation, globulin levels significantly increased in the GIANT-G9 but with similar values to the stressed commercial strain. Myostatin expression increased in the spleen of the stressed GIANT-G9. The commercial strain exhibited the best liver catalase and superoxide dismutase activities under stress, while the GIANT-G9 showed increased liver glutathione-S-transferase (GST) activity after exposure to ammonia and temperature stress. Serum lysozyme activity increased in the stressed commercial strain and under temperature stress in the GIANT-G9 but decreased under other stress conditions. Overall, the stressed commercial strain demonstrated higher survivability than the stressed GIANT-G9. The study revealed significant interactions between strains and stress factors. The GIANT-G9 exhibited higher growth rates but lower antioxidant and immune capacities compared to the commercial strain at the juvenile stage of life and production cycle., Competing Interests: Declarations. Ethics approval: The experiment and animal management protocols were approved by the Faculty of Fish Resources at Suez University, Suez, Egypt (Approval number 07/05/2024/10). The study was conducted in accordance with national and international regulations and guidelines, including the ARRIVE guidelines ( https://arriveguidelines.org/ ). Consent for publication: Not applicable. Competing interests: The authors declare no competing interests, except that Dr. Ahmed Nasr-Allah is the Country Director of WorldFish– Egypt. We affirm that this competing interest does not compromise the integrity of the research findings presented in the manuscript., (© 2025. The Author(s).)

High cadmium (Cd) concentrations pose a threat to aquatic life globally. This study examined the efficiency of adding purslane (Portulaca oleracea L.) leaf powder (PLP) to Oreochromis niloticus diets on Cd's negative effects. PLP was analyzed using high-performance liquid chromatography, and its main constituents were gallic acid, chlorogenic acid, and pyrocatechol. Nile tilapia (180 fish, 34.5 ± 0.5 g) were divided into four groups in triplicate. A basal diet was given to the control group. The PLP group received a basal diet containing 10 g PLP/kg diet. The Cd group was exposed to 50 µg/L water. The Cd + PLP group was exposed to Cd and fed diets containing PLP. Results showed that PLP significantly rescued Cd-induced effects. PLP improved fish survival, feed conversion ratio, and growth retardation caused by Cd. PLP also restored decreased activities of lipase, trypsin, and amylase in the intestine. Furthermore, PLP corrected disturbances in leptin and growth hormone levels induced by Cd. PLP mitigated pathological alterations, replenished antioxidants (SOD, CAT, and GSH), and reduced lipid peroxidation in the intestinal tissues. PLP supplementation depleted significant Cd accumulation in the intestine and muscles. Additionally, PLP corrected altered expressions of tight junction proteins (zo-1, zo-2, and claudin-4) and nutrient transporters (glut-1, slc15a2, slc26a6, and slc4a4) in Cd-exposed fish. Conclusively, PLP shows promise as a dietary supplement to mitigate Cd's harmful impacts on fish growth. Its antioxidant activity and regulation of intestinal tight junction proteins and nutrient transporters contribute to its effectiveness. PLP supplementation holds the potential for reducing the detrimental effects of Cd in aquaculture., Competing Interests: Declarations. Ethical approval: The experiment was conducted per the ethical recommendations for the Use and Care of Laboratory Animals in scientific investigations set by the National Institutes of Health (NIH), and it was supervised by the Animal Use in Research Committee (IACUC) of Zagazig University (Approval no. ZU-IACUC/2/F/392/2023). Consent to participate: All authors have participated in this work. Consent for publication: All authors review and approve the manuscript for publication. Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

This study was performed to reveal the metabolic effects and molecular mechanisms that govern the dietary incorporation of clenbuterol on growth performance, haemato-biochemical changes, histological alteration, and gene expression regulating glucose and lipid metabolism in normal and high-fat diets fed in Nile tilapia (Oreochromis niloticus). Six experimental diets were formulated, incorporating different concentrations of clenbuterol. The 1st three groups were supplemented with a diet comprising 6% fat, with clenbuterol of 0, 5, and 10 g/kg diet was designated as F6 clenb0, F6clenb5, and F6clenb10, respectively. The other treatment groups were fed a diet of 12% fat, with clenbuterol 0, 5, and 10 g/kg diet, respectively termed F12 clenb0, F12 clenb5, and F12 clenb10. The results revealed that compared to the control group, HFD exhibited a marked reduction in FBW, BWG, PER, and body protein percent but significantly increased the FCR, IPF, liver fat percent, and body ash percent with altered hematological parameters, raised serum biomarkers of hepatic and renal injury. HFD signally raised mRNA expression of pro-inflammatory cytokines, and declined nrf2 and antioxidative function-related genes. Also increased mRNA expression of lipogenic genes as FAS and SREBP-1c and gluconeogenic genes as pepck and g6pc while downregulated, pparα, cpt1, acox1. Nevertheless, clenbuterol supplementation significantly reversed the aforementioned findings induced by HFD. Clenbuterol inclusion significantly improves growth performance and antioxidant defenses by modulating nrf2 signaling and reducing inflammatory response, reduces fatty acid synthesis, and enhances mitochondrial β-oxidation not only functioning as a lipid regulator and effectively alleviating fat accumulation in the liver but playing an essential role in the control of glucose metabolism by reducing hepatic glucose production in high-fat diet-fed Nile tilapias well., Competing Interests: Declarations. Competing interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Ethical approval: All methods were carried out in accordance with relevant guidelines and regulations of Kafrelsheikh University ethical committee (IAACUC-KSU-028-2022). All methods are reported in accordance with ARRIVE guidelines ( https://arriveguidelines.org )., (© 2024. The Author(s).)

Increasing aquaculture production requires high-density farming, which induces stress, necessitating supplements to mitigate its effects and ensure fish health. The aim of this study was to examine how CaNa2EDTA (EDTA) affects the growth, immune response and antioxidant activity in Nile tilapia (Oreochromis niloticus). The fish were raised at three different stocking densities: low (LD = 2.00 kg/m3), medium (MD = 3.50 kg/m3), and high (HD = 5.00 kg/m3). Each density group was fed with one of four levels of EDTA supplementation (E0 = 0 g/kg, E1 = 5 g/kg, E2 = 10 g/kg, and E3 = 15 g/kg) for 60 days. Each diet was tested in triplicate (n = 66 fish per replicate in LD, 116 per replicate in MD, and 166 per replicate in HD). After 60 days, the results of this study declared that LD group showed better growth than the MD and HD groups, and among all groups, those fed the E1 diet grew better than those on other diets. The study found significant changes in the chemical composition of the fish and the activity of digestive enzymes across all treatments. Antioxidant enzyme levels and cortisol were higher in the HD group compared to the LD and MD groups. However, fish in the HD group fed the E1 diet had the lowest levels of antioxidant enzymes and cortisol. Malondialdehyde levels were higher in the HD group compared to the LD and MD groups, with the lowest levels seen in fish on the E1 diet in the HD group. The expression of Somatostatin-1 did not increase in the MD group compared to the LD and HD groups. The gene expression levels of pro-opiomelanocortin-α and Interleukin 1-β were not significantly affected by either stocking density or EDTA supplementation. In conclusion, EDTA supplementation improved growth and antioxidant response in tilapia, with the best results seen at a dose of 5 g/kg in the high-density group, suggesting that this approach could be beneficial in intensive tilapia farming., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2025 Komal et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Low temperatures significantly impact growth in ectothermic vertebrates, though the underlying mechanisms remain poorly understood. This study investigates the role of transient receptor potential ankyrin 1 (TRPA1) channels in mediating low-temperature effects on growth performance and GH resistance in Nile tilapia (Oreochromis niloticus). Prolonged exposure to low temperature (16 °C for 35 days) impaired growth performance and induced GH resistance, characterized by elevated serum GH levels and decreased IGF-1 levels. Molecular analysis revealed tissue-specific upregulation of TRPA1 expression in the pituitary and liver under low-temperature conditions, concurrent with alterations in GH/IGF-1 axis-related gene expression. Pharmacological modulation of TRPA1 using an agonist mimicked low-temperature effects on the GH/IGF-1 axis, while an antagonist reversed cold-induced hormonal changes. In vitro experiments with tilapia hepatocytes demonstrated that TRPA1 activation decreased IGF-1 expression through calcium ion/calmodulin-dependent pathways and disrupted GH-induced JAK2/STAT5 signaling. Additionally, TRPA1 activation induced GH receptor degradation primarily through lysosomal pathways, with partial involvement of proteasomal mechanisms. This study is the first to reveal that TRPA1 channels play a crucial role in mediating the effects of low temperature on GH resistance in fish, providing new insights into temperature regulation of endocrine function. The evolutionary conservation of TRPA1 and the GH/IGF-1 axis suggests potential relevance to stress-induced endocrine dysfunction in other vertebrates, including mammals., (© The Author(s) 2025. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com. See the journal About page for additional terms.)

Aggression is ubiquitous among social species and can function to maintain social dominance hierarchies. The African cichlid fish Astatotilapia burtoni is an ideal study species for studying aggression due to their dominance hierarchy and robust behavioral repertoire. To further understand the potential sex differences in aggression in this species, we characterized aggression in male and female A. burtoni in a mirror assay. We then quantified neural activation patterns in brain regions of the social behavior network (SBN) to investigate if differences in behavior are reflected in the brain with immunohistochemistry by detecting the phosphorylated ribosome marker phospho-S6 ribosomal protein (pS6), a marker for neural activation. We found that A. burtoni perform both identical and sex-specific aggressive behaviors in response to a mirror assay. Females had greater pS6 immunoreactivity than males in the Vv (ventral part of the ventral telencephalon), a homolog of the lateral septum in mammals. Males but not females had higher pS6 immunoreactivity in the ATn after the aggression assay. The ATn (anterior tuberal nucleus) is a homolog of the ventromedial hypothalamus in mammals, which is strongly implicated in the regulation of aggression in males. Several regions also have higher pS6 immunoreactivity in negative controls than fish exposed to a mirror, implicating a role for inhibitory neural processes in suppressing aggression until a relevant stimulus is present. Male and female A. burtoni display both similar and different behavioral patterns in aggression in response to a mirror assay. There are also sex differences in the corresponding neural activation patterns in the SBN. In mirror males but not females, the ATn clusters with the POA, revealing a functional connectivity of these regions that is triggered in an aggressive context in males. These findings suggest that distinct neural circuitry underlie aggressive behavior in male and female A. burtoni, serving as a foundation for future work investigating the molecular and neural underpinnings of sex differences in behavior in this species to reveal fundamental insights into understanding aggression., Competing Interests: Declarations. Ethics approval and consent to participate: Experimental procedures were conducted according to the ethical guidelines for the care and use of laboratory animals. Experiments were approved by the University of Houston Institutional Animal Care and Use Committee (Protocol #202000001). Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

The point of our study was to examine the interaction of ammonia-N poisoning and salinity on serum enzymes and oxidative stress factors of blood and liver in Nile tilapia (Oreochromis niloticus). The 50% lethal concentration (LC 50 ) in 96 h was 0.86 mg/L of ammonia-N. A random allocation was used to divide the fish into 12 treatments. These treatments encompassed various combinations of acute ammonia-N levels (0 and 50% of LC 50 -96 h), sub-acute ammonia-N levels (30% of LC 50 -96 h), and salinity levels (0, 4, 8, and 12 ppt). The experimental design employed a factorial arrangement of 3 × 4.The findings revealed that the amounts of aspartate transferase (AST) and alanine transaminase (ALT) in treatments 3 and 4 increased significantly compared to the treatment 2 (4 ppt) and control. Salinity levels did not affect serum glutathione levels (GSH), nevertheless the reduction of serum GSH and levels of total antioxidant capacity (TAC) and superoxide dismutase (SOD) and catalase activities (CAT) in ammonia poisoning treatments, 5 and 9, compared to the control, states ammonia can stimulate oxidative stress in fish. Similar to the serum measurements, increasing salinity in acute ammonia poisoning treatments (5, 6, 7 and 8) caused an increasing effect on the liver TAC value, which was presumably due to the improving effect of salinity in reducing ambient ammonia. The findings indicate that while elevated salinity levels can be beneficial in mitigating the effects of ammonia toxicity in water, the combined presence of salinity, ammonia, and their interaction had detrimental impacts on the physiological well-being of fish over a 96-hour testing period., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethics approval: This research was carried out according to the standards of the animal protection and ethics committee of Shahid Chamran University, Ahvaz, Iran., (© 2024. The Author(s).)

Environmental safety has become a major concern in recent years due to the global increase in microplastic pollution. These ubiquitous, tiny, and potentially toxic plastic particles enter aquatic environments through weathering of larger plastics and the release of microbeads. Although numerous studies have focused on microplastic pollution in developed regions, information from developing countries remains limited. This study assessed the presence of MPs and associated oxidative stress responses in two commercial fish species, Clarias gariepinus (Catfish) and Oreochromis niloticus (Nile Tilapia), from Kubanni reservoir, Zaria, Nigeria, over six months spanning both the dry and rainy seasons. Fibers were identified as the most abundant MP particles, followed by fragments, films, and beads, in the order of fibers > fragments > films > beads. The highest fiber concentrations were recorded in the gills, with Clarias garipinus showing 11.5 MP items/individual and Oreochromis niloticus showing 22.5 MP items/individual. Black microplastics were predominant, and the most common ingested MP ranged from 1.0 to 2.0 mm. The primary polymers identified were polypropylene and polyethylene terephthalate. Evidence of oxidative stress and cellular damage was observed in the gills, liver, and dorsal muscles of both fish species, which correlated with MPs ingestion. According to recommendations from the European Food Safety Authority regarding fish consumption by children and adults, individuals consuming Clarias gariepinus and Oreochromis niloticus from the Kubanni reservoir may be exposed to between 70 and 700 MP items/organ. The risk associated with consuming MPs found in fish gills and guts was notably higher, posing significant concerns for human health. This study provides insights into microplastic contamination in commercially important fish from the Kubanni Reservoir and highlights the environmental and public health risks associated with consuming contaminated fish from this ecosystem., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Acute hypoxia is known to increase the generation of reactive oxygen species (ROS), leading to modulation in antioxidant defenses. Pollutant exposure can potentiate ROS generation during hypoxic events and impair antioxidant defenses, increasing the susceptibility of hypoxia-tolerant fishes, such as the Nile tilapia (Oreochromis niloticus), to oxidative stress. The purpose of this study was to evaluate oxidative stress responses of O. niloticus to acute (3 and 8 h) moderate hypoxia (dissolved oxygen ≤2 mg/L -1 ) and how these responses are affected by simultaneous exposure to the insecticide fipronil (0.1 and 0.5 µg L -1 ). Hypoxia exposure for 3 h caused an increase in glutathione peroxidase (GPx) activity in the gill and also increased catalase (CAT) and glutathione S-transferase (GST) activities in the liver. After 8 h of hypoxia, glutathione reductase (GR) activity increased. DNA damage (comet assay) in erythrocytes was reduced by hypoxia after 3 and 8 h. Fipronil exposure for 3 h decreased CAT activity in the gill, both under normoxia and hypoxia. After 8 h, the combination of fipronil and hypoxia increased GR activity in the gill. In the liver, fipronil exposure under hypoxia for 3 h increased CAT and GR activities; after 8 h, CAT was decreased, and GST increased. GR was also increased by fipronil under normoxia for 8 h. All treatments reduced lipid peroxidation levels in the gills, but in the liver, lipid peroxidation was increased by fipronil after 3 h under normoxia. Moreover, fipronil exposure under hypoxia for 3 and 8 h increased DNA damage in erythrocytes, while 8 h of fipronil exposure under normoxia decreased it, suggesting the activation of DNA repair mechanisms. Results show that both fipronil and hypoxia exposure significantly modulate the oxidative stress parameters of O. niloticus and that the combination of these factors produces more pronounced effects., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The present experiment evaluated whether dietary protein (P) or lipid (L) is preferred as an energy source by genetically improved farmed tilapia (GIFT) reared at high temperatures. A 60-day feeding trial was conducted at 28.3 °C and 33.3 °C, testing five diets with varying protein (34,36,38 %) and lipid (8,10,12 %) levels, viz., P 38 L 8 , P 36 L 8 , P 34 L 8 , P 34 L 10 , P 34 L 12 . Parameters assessed included growth, body composition, serum lipids, enzyme activities, fatty acid profiles, and PPAR-α mRNA expression. Results indicated that the fish fed optimum protein and highest lipid level (P 34 L 12 ) showed significantly higher (P < 0.05) weight gain percent and thermal growth coefficient. Increasing dietary lipid content reduced whole-body lipid deposition and mobilised serum triglycerides and cholesterol at higher temperatures (HT). Hepatic malic enzyme activity decreased with rising temperature and lipid content, while lipoprotein lipase activity in muscle increased. The fatty acid composition altered substantially with the changes in rearing temperature and diets. Unsaturated fats were preferred as direct fuels for β-oxidation, wherein the P 34 L 12 groups preserved body (area %) EPA, DHA, and linolenic acid, especially at HT. The expression of PPAR-α, a lipolytic marker, was upregulated with increasing temperature and high dietary lipid content, peaking in P 34 L 12 groups. The study concludes that high-lipid diets (12 %) are metabolically superior to high-protein diets for GIFT tilapia at elevated temperatures, optimising growth, enhancing metabolic efficiency, and maintaining essential fatty acid profiles under hyperthermal stress., Competing Interests: Declaration of competing interest The authors declare no competing interests for this manuscript., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The wide-ranging use of heavy metals and pesticides worldwide and their irreversible accumulation in aquatic ecosystems is a major concern. As the range of household and agricultural chemicals increases, water pollution is trending from the toxic effects of a single agent to complex agent pollution that threatens aquatic ecosystems. The aim of this study was to investigate the effects of pesticides (imidacloprid, IMI) and metals (copper sulfate, CuSO 4 ) on oxidative stress biomarkers, antioxidant enzymes, and biomolecular parameters. The present study on the individual and combined effects of Oreochromis niloticus copper sulfate (CuSO 4 ; 1 ppm), imidacloprid (IMI; 10 and 50 ppm), and IMI + CuSO 4 (IMI10 + CuSO 4 , IMI50 + CuSO 4 ) groups for 14 days. In this context, oxidative stress/antioxidant markers (SOD, CAT, GST, and GSH) and biomolecular markers including HSP70, 8-OHdG, PC, and TBARS levels were examined in fish liver and kidney tissues, which are detoxification organs. The results indicated that IMI and CuSO 4 toxicity alone and in combination altered oxidative stress/antioxidant markers and biomolecular parameters; moreover, 14 days of exposure to the combination of CuSO 4 and imidacloprid in particular exhibited a synergistic effect and caused oxidative toxicity. These findings highlighted the importance of evaluating mixtures of pesticides and metals and that the results show a remarkably synergistic effect. It can be concluded that these biomarkers are important indicators of physiological changes in living organisms., Competing Interests: Declarations. Ethics Approval: Ethics committee permission for the study was approved by the Health Sciences Experimental Application and Research Center affiliated with Çukurova University (numbered 8–5/2023). Competing Interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

This study evaluated the efficacy of integrating artichoke (Cynara scolymus) leaf extract (CSLE) into the Nile tilapia (Oreochromis niloticus) diet to mitigate fluoride (FLR) adverse effects on growth, immune components, renal and hepatic function, and the regulation of oxidative stress, inflammation, and apoptosis-related genes. A 60-day feeding experiment was conducted with 240 O. niloticus fish separated into four groups as follows: a control group (CON) fed on a basic diet, a CSLE group receiving 300 mg CSLE/kg via the diet, a FLR group exposed to 6.1 mg/L waterborne FLR, and a group receiving both CSLE and FLR. Fish exposed to FLR exhibited slower growth rates and poorer feed conversion compared to the control group. They also displayed signs of anemia, leukopenia, and elevated serum levels of renal injury indicators and liver enzymes. Consistent with a decrease in both non-enzymatic and enzymatic antioxidants, higher levels of hepatic lipid peroxidation products were observed. Exposure to FLR resulted in decreased serum lysozyme activity, nitric oxide, complement 3, IgM, total protein, globulin, and albumin levels. FLR induced multiple pathological perturbations in the spleen, liver, and kidneys, and increased the mRNA expression of splenic tumor necrosis factor-alpha, heat shock protein 70, interleukin-1 beta, tumor protein p53, and cysteine-aspartic acid protease 3 while reducing superoxide dismutase and catalase gene expression. However, the majority of FLR adverse effects were significantly reduced by adding 300 mg CSLE/ kg diet. Adding CSLE to O. niloticus' diet may reduce FLR's negative effects, making it a beneficial aquafeed., Competing Interests: Declaration of competing interest The authors have no relevant financial or non-financial interests to disclose., (Copyright © 2024. Published by Elsevier Inc.)

This work aimed to investigate the response of cholecystokinin (CCK) to starvation and its impact on food intake and the reproductive axis of the tilapia Oreochromis mossambicus. The fish subjected to 21 days of starvation showed a significant decrease in CCK immunoreactivity in the hypothalamus, pituitary gland, and intestine. The administration of injections of 0.5 and 5 μg of sulfated CCK-8 (CCK-8S) over 21 days resulted in a significant, dose-dependent decrease in food consumption. Administration of a high dose of CCK-8S (5 μg) caused a substantial decrease in the number of various spermatogenic cells, the intensity of androgen receptor immunoreactivity in the testis, and the percentage area of GnRH-immunoreactive fibres in the pars distalis of the pituitary gland (PPD), concurrent with a significant decline in serum levels of luteinizing hormone (LH) and 11-ketotestosterone (11-KT). Moreover, CCK-8S treatment markedly reduced the in vitro testicular 11-KT level. The findings indicate for the first time that CCK influences hypothalamic GnRH release into the pituitary gland, resulting in the inhibition of LH release from the pituitary and affecting testicular spermatogenesis, androgen receptor protein expression, and steroidogenesis in teleosts. In addition, CCK may also directly affect testicular steroidogenesis., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest related to this manuscript., (Copyright © 2025 Elsevier Inc. All rights reserved.)

Alkaline stress impairs fish productivity and performance and, therefore, is considered one of the major challenges facing aquaculture. In this work, the effects of supplementing diets with camel whey protein hydrolysates (WPH) on growth, digestion, antioxidant capacity, and gene expression were investigated in Nile tilapia (Oreochromis niloticus) under alkaline stress. A total of 160 fish (16.17 ± 0.29 g) were equally assigned into four treatments, with 10 fish in each replicate. The control (C) and WPH groups received the basal diet supplemented with 0 and 75 g/kg WPH, respectively, and were reared in freshwater with an alkalinity of 1.4 mmol NaHCO 3 /L. The alkaline-exposed (AK) and AK + WPH groups were subjected to alkaline water (alkalinity = 23.8 mmol NaHCO 3 /L) and fed basal and WPH diet, respectively. Alkaline stress depressed the growth performance, digestive enzyme activity, intestinal Lactobacillus count, intestinal morphometrics, growth hormone level, and antioxidant enzyme activity but enhanced leptin hormone level and malondialdehyde (MDA) concentrations in Nile tilapia. Alkaline stress also downregulated the transcription of key intestinal transporter genes. Dietary supplementation with WPH significantly improved growth, digestive enzyme activity, antioxidant capacity, and the gene expression profile of Nile tilapia under alkaline stress. Based on the current results, it was concluded that WPH diet could mitigate negative effects caused by alkaline stress in Nile tilapia, which might support its application as an effective functional protein replacement candidate in aquaculture., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2025 Elsevier Inc. All rights reserved.)

Settleable atmospheric particulate matter (SePM), from steelmaking processes, contains a complex mixture of metals, metalloids, and metallic nanoparticles. The SePM is released airborne and disperses in water, representing a significant threat to aquatic life, particularly fish. This study investigated the effects of a sublethal and environmentally relevant concentration of SePM (1 g·L -1 ) for 96 h in the gill, liver, kidney, and white muscle of Nile tilapia (Oreochromis niloticus), employing exposure and effect biomarkers to test causality between metal accumulation and biochemical responses. The gills and liver showed the highest bioaccumulation of metals and integrated response index value, indicating susceptibility to metal accumulation. However, the gills produce a protective mucus layer that may mitigate metal toxicity. The kidneys and muscle tissue also showed bioaccumulation of metals, although to a lesser extent. The liver and kidneys experienced oxidative stress, characterized by reduced metallothionein and glutathione levels, as well as damage to lipids, proteins, and DNA. The accumulation of less-studied metals, particularly Rare Earth Elements (REEs), compromised the integrity of biomolecules in these tissues. In conclusion, the complex dynamics of metal bioaccumulation in Nile tilapia exposed to SePM reveal varied tissue responses and primary effects like oxidative damage. They also highlight the need for further research and regulation of other metals and their potential impacts on aquatic ecosystems and human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The discus fish, Symphysodon spp., a South American cichlid, has a unique parental care behavior where fry bite on parental skin mucus after hatching. In this study, we used LC-MS/MS technique to compare the skin mucus proteome composition of male or female discus fish during parental and non-parental care periods. By multivariate statistical analysis, we found clear separations between different periods and between different sexes of mucus proteome. Compared with non-parental female fish, parental female fish had 283 up-regulated and 235 down-regulated expressed proteins. Compared with non-parental male fish, parental male fish had 169 up-regulated and 120 down-regulated expressed proteins. The differentially expressed proteins for male fish were enriched in sulfur relay system, mucin type O-glycan biosynthesis and antigen processing and presentation pathways, while those for female fish were enriched in sulfur relay system, steroid biosynthesis and complement and coagulation cascades pathways. During the parental care, both male and female discus showed an enhanced lipid metabolism, producing more phospholipids and cholesterol. The difference is that male discus had increased tricarboxylic acid cycle producing more energy during the parental care, while females produced more nucleotides especially guanylic acid. Our study could provide new insights into the understanding of the unique mucus supply behavior of discus fish based on proteomic change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The present study evaluated the effects of curcumin on growth, immune and antioxidant response in tilapia (Oreochromis niloticus). An optimum dose of curcumin was investigated by feeding four different levels of this compound in combination with three different regimes of stocking density (12 treatments). Fish were reared at three densities; low density (LD = 1.50 kg/m3), medium density (MD = 3.00 kg/m3), and high density (HD = 4.50 kg/m3). Each treatment was fed with four different levels of dietary supplementation of curcumin (C0 = 0 mg/kg, C1 = 50 mg/kg, C2 = 100 mg/kg, and C3 = 150 mg/kg) for 60 days. Each treatment has three replicates (n = 50/replicate in LD, 100/replicate in MD, 150/ replicate in HD). Although better growth was observed in MD, however treatments at all densities fed with C1 diet showed improved growth as compared to other diets. Chemical composition of fish and activity of amylase, lipase and protease in all treatments were noted to be similar. Levels of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and cortisol in MD and HD treatments were similar to those in LD treatment. However, fish fed with C1 diet in each density treatment showed the lowest values of antioxidant enzymes. Similarly, the levels of malondialdehyde were noted to be similar in MD and HD treatments as compared to that in LD. Its levels were lower in fish fed with C1 and C3 diets in all density treatments. Expression of pro-opiomelanocortin-α (POMC-α), Somatostatins-1 (SST-1) and Interleukin 1-β (IL-1β) did not increase in MD and HD treatments in response to high stocking density when compared with LD treatment. The lowest levels of these genes were noted in fish fed with C2 and C3 diets in all treatments. In conclusion, supplementation of curcumin in diet of tilapia improved growth and antioxidant response in tilapia. optimum dose of curcumin for tilapia culture is 50 mg/kg at the density of 3.00 kg/m3which might be further investigated for intensive culture., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Komal et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Previous research has highlighted the significant role of progestins and glucocorticoids in fish oocyte maturation and ovulation. To clarify the molecular mechanisms underlying these processes, comprehensive investigations were conducted using a cyp17a2 mutant Nile tilapia ( Oreochromis niloticus ) model. Analysis revealed pronounced Cyp17a2 expression in ovarian somatic cells of the tilapia. Female cyp17a2 -deficient mutants exhibited markedly reduced levels of 17,20β-dihydroxy-4-pregnen-3-one (DHP) and cortisol/cortisone, leading to delayed meiotic initiation and impaired oocyte maturation and spawning. Notably, supplementation with human chorionic gonadotrophin (hCG), DHP, and cortisol effectively induced germinal vesicle breakdown (GVBD) and facilitated oocyte release with follicular cell layers in cyp17a2 -/- females. Additionally, cyp17a2 -/- and rescued cyp17a2 -/- females showed elevated transcription of steroidogenic enzymes involved in 17β-estradiol (E2) production compared to spawning wild-type females. Moreover, the reduction in Akt phosphorylation observed in cyp17a2 -deficient females and upon inhibitor treatment impaired hCG-induced oocyte maturation. Conversely, activation of the phosphoinositide 3-kinase/protein kinase B (PI3K-Akt) signaling pathway partially rescued the oocyte maturation impairment caused by cyp17a2 mutation. Overall, these findings provide functional evidence supporting the critical role of Cyp17a2 in DHP and cortisol biosynthesis, which, in turn, facilitates oocyte maturation and ovulation through activation of the PI3K-Akt signaling pathway in fish.

Background: Zophobas atratus larval meal (ZLM) is a high-quality feed supplement with potential activities that can improve fish growth performance and promote meat quality. However, there have been limited recent studies investigating the metabolic effects of ZLM. Therefore, this study aims to uncover the metabolomic mechanism through which ZLM improves tilapia meat flavor using metabolomic strategies., Method: In this study, soybean meal in the basal diets was replaced with 15%, 30%, or 60% ZLM, where anti-nutrient factors were destroyed by high temperature treatment. After being fed these ZLM supplements for 30 days, dorsal muscles were collected from tilapia for meat sensory evaluation tests. Liver samples were also collected for metabolomic analysis using the gas chromatography-mass spectrometry (GC-MS) platform and combined with biochemical assays to verify metabolism-related enzyme activities and reveal crucial metabolic pathways and critical biomarkers associated with ZLM's ability to improve meat flavor., Results: In tilapia livers, ZLM enhanced the activity of enzymes involved in energy metabolism including succinate dehydrogenase (SDH), pyruvate dehydrogenase (PDH), α-ketoglutarate dehydrogenase (α-KGDH), NADP-malate dehydrogenase (NAD-MDH) and mitochondrial isocitrate dehydrogenase (ICDHm). This resulted in increased levels of reduced nicotinamide adenine dinucleotide (NADH), acetyl CoA and ATP which led to accumulation of flavor fatty acids such as arachidonic acid, linoleic acid (9,12-Octadecadienoic acid), linolenic acid (9,12,15-Octadecatrienoic acid) and oleic acid (9-Octadecenoic acid). Additionally, there was an increase in flavor nucleotides like guanosine adenosine-5'-monophosphate and uridine-5'-monophosphate while off-flavor metabolites like inosine and hypoxanthine decreased. Furthermore, beneficial metabolomic responses led to a decrease in off-flavor metabolites such as 2-methylisoborneol trimethylamine and geosmin while increasing umami metabolites like 2-methyl-3-furanthiol and nonanal., Conclusions: This metabolomic study demonstrates that inclusion of ZLM diets enhances the flavor profile of tilapia dorsal muscle. The accumulation of flavor compounds, coupled with a reduction in earthy taste and off-flavor metabolites, contributes to an improved meat flavor and freshness. Additionally, there is an increase in the levels of flavor-related amino acids and nucleotides. These previously unidentified metabolic effects highlight the potential significance of ZLM as a dietary supplement for enhancing the biosynthesis of flavor metabolites in tilapia., (© 2024 The Author(s). Published by IMR Press.)

Temperature is a preeminent factor in the regulation of fish reproduction and hinders gonadal development beyond a specific threshold. To comprehend the molecular mechanism responsible for reproductive suppression at different temperature, expression of the genes encoding kisspeptin (kiss2), gonadotropin-releasing hormone (gnrh1) and their receptors (gpr54, gnrh1r) in the brain, and the gonadotropin (GTH) subunits (fshb and lhb) in the pituitary were studied in juvenile Nile tilapia (Oreochromis niloticus) along with gonadal histology. Fish were acclimatized to three distinct temperatures, including 31 °C, 34 °C and 37 °C for 14 days. The mRNA levels of kiss2, gpr54, gnrh1, and gnrh1r were significantly decreased at 37 °C compared to 31 °C and 34 °C in the both sexes. In parallel, the expression level of fshb in the both sexes and lhb in the female were significantly lower at 37 °C in the pituitary. Histologically, the gonads of both sexes had normal growth of gametes at control temperature (31 °C), whereas the spermatogenesis and oocyte maturation were slowed down and atretic oocytes were found in the ovary at 37 °C acclimation temperature. Taken together, the results imply that elevated temperature beyond the specific threshold may have a negative impact on reproduction by suppressing the gene expressions of kisspeptin/GnRH1/GTH system and eventually restrains normal growth and maturation of gametes in the both sexes of Nile tilapia., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Generally, energy expenditure and compensation according to food deprivation and refeeding often occur along the life cycle of farmed-raised fish. Fasting and refeeding are also hypothesised to modulate carbohydrate metabolism particularly for herbivorous and/or omnivorous. This study aims to investigate the effects of short-term fasting and subsequent refeeding with high or low-carbohydrate diets on the intermediary carbohydrate metabolism of juvenile and adult Nile tilapia (Oreochromis niloticus) which is known to be a good user of carbohydrate as an energy source. Fish were fasted for 4 days and subsequently refed with either a low carbohydrate and high protein (LC/HP) or high carbohydrate and low protein (HC/LP) diet for 4 days. Our results showed that 4 days of refeeding with either one of the diets could compensate for weight loss due to fasting. Thus, we investigated the effects of a 4-day-refeeding strategy and different carbohydrate-refeeding diets on plasma metabolites, nutrient composition, and glucose and its related metabolism in the liver and muscle of adult fish. Refeeding had similar effects in adults and juveniles and induced modulations to the intermediary metabolism: (1) refeeding with the HC/LP diet elevated plasma glucose levels; (2) refeeding with both diets increased triglyceride levels in the plasma, liver, and muscle, but the effect of the HC/LP diet was superior; (3) refeeding elevated plasma cholesterol levels in adults, irrespective of diet; (4) refeeding with both diets increased hepatic lipid levels in juveniles, with stronger effects observed in those fed the HC/LP diet, and refeeding with the HC/LP diet elevated hepatic lipid levels in adults; (5) refeeding with both diets increased the plasma protein content, but the effect of the LC/HP diet was superior; (6) refeeding with the LC/HP diet increased hepatic protein content in adults; and (7) refeeding with both diets increased hepatic glycogen levels, but the effect of the HC/LP diet was superior. Additionally, in juveniles and adults, refeeding with the HC/LP diet upregulated the expression of glycolytic genes in the liver and muscle, lipogenic genes in the liver, and glucose transport genes. Moreover, refeeding with the HC/LP diet downregulated the expression of gluconeogenic and amino acid catabolism genes in the liver and amino acid catabolism genes in the muscle. Collectively, the effect of short-term refeeding with a high carbohydrate diet on intermediary metabolism resembled that of long-term feeding, supporting the hypothesis that Nile tilapia, an omnivorous fish, is highly responsive to dietary carbohydrates., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

In teleosts, GnRH1 neurons stand at the apex of the Hypothalamo-Pituitary-Gonadal (HPG) axis, which is responsible for the production of sex steroids by the gonads (notably, androgens). To exert their actions, androgens need to bind to their specific receptors, called androgen receptors (ARs). Due to a teleost-specific whole genome duplication, A. burtoni possess two AR paralogs (ARα and ARβ) that are encoded by two different genes, ar1 and ar2, respectively. In A. burtoni, males stratify along dominance hierarchies, in which an individuals' social status determines its physiology and behavior. GnRH1 neurons have been strongly linked with dominance and circulating androgen levels. Similarly, GnRH3 neurons are implicated in the display of male specific behaviors. Some studies have shown that these GnRH neurons are responsive to fluctuations in circulating androgens levels, suggesting a link between GnRH neurons and ARs. While female A. burtoni do not naturally form a social hierarchy, their reproductive state is positively correlated to androgen levels and GnRH1 neuron size. Although there are reports related to the expression of ar genes in GnRH neurons in cichlid species, the expression of each ar gene remains inconclusive due to technical limitations. Here, we used immunohistochemistry, in situ hybridization chain reaction (HCR), and spatial transcriptomics to investigate ar1 and ar2 expression specifically in GnRH neurons. We find that all GnRH1 neurons intensely express ar1 but only a few of them express ar2, suggesting the presence of genetically-distinct GnRH1 subtypes. Very few ar1 and ar2 transcripts were found in GnRH2 neurons. GnRH3 neurons were found to express both ar genes. The presence of distinct ar genes within GnRH neuron subtypes, most clearly observed for GnRH1 neurons, suggests differential control of these neurons by androgenic signaling. These findings provide valuable insight for future studies aimed at disentangling the androgenic control of GnRH neuron plasticity and reproductive plasticity across teleosts., (© 2024 British Society for Neuroendocrinology.)

This study aimed to assess the in vitro and in vivo disinfectant potential of peracetic acid (PAA) (1 mg/L) and hydrogen peroxide (H 2 O 2 ) (20 mg/L) on the physicochemical and microbiological water quality parameters of fish aquaria, the microbial density of Nile tilapia muscular tissue, fish hepatic cortisol levels, and antioxidant biomarkers. In vitro, PAA and H 2 O 2 reduced A. hydrophila colony viability by 5 log units after 30 and 5 min of contact time, respectively. PAA and H 2 O 2 were added to aquaria water twice a week for the three-week experiment. Increased fish escape reflexes were observed only in the PAA group, which returned to normal within 10 min. No mortalities were reported in either the PAA or H 2 O 2 groups. An in vivo experimental challenge with a pathogenic strain of A. hydrophila revealed a 20% reduction in mortality in the PAA group, with no mortalities in the H 2 O 2 group. Cortisol levels and antioxidant markers were measured to assess the impact of PAA and H 2 O 2 on fish health. Cortisol levels in the PAA and H 2 O 2 groups were significantly higher than in the control group after disinfectant exposure, but they progressively returned to normal. A significant reduction in superoxide dismutase (SOD) and catalase (CAT) activity, along with considerably higher glutathione peroxidase (GPx) and malondialdehyde (MDA) enzymatic activity, was observed in the PAA and H 2 O 2 groups compared to the control group. A substantial increase in total antioxidant capacity (TAC) was recorded in the PAA group. Physicochemical analyses revealed reduced pH and increased dissolved oxygen levels in the PAA and H 2 O 2 groups. Microbiological analyses showed a significant reduction in bacterial density in water by 64% and 76% after 30 min of exposure to PAA and H 2 O 2 , respectively, with a non-significant increase in microbial count after bacterial challenge. Additionally, aerobic bacterial count, Aeromonas spp., and psychotropic bacterial count in fish muscle showed a significant reduction in the H 2 O 2 group compared to the PAA and control groups before and after infection. The study concludes that regular application of PAA and H 2 O 2 can temporarily reduce bacterial load in aquaria and fish muscle, regulate stress responses, and improve fish health by reducing A. hydrophila-induced infections and improving survival., (© 2024. The Author(s).)

Background: Commensal bacteria in the intestine release enzymes to degrade and ferment dietary components, producing beneficial metabolites. However, the regulatory effects of microbial-derived enzymes on the intestinal microbiota composition and the influence on host health remain elusive. Xylanase can degrade xylan into oligosaccharides, showing wide application in feed industry., Results: To validate the immune-protective effects of xylanase, Nile tilapia was used as the model and fed with xylanase. The results showed that dietary xylanase improved the survival rate of Nile tilapia when they were challenged with Aeromonas hydrophila. The transcriptome analysis showed significant enrichment of genes related to interleukin-17d (il-17d) signaling pathway in the xylanase treatment group. High-throughput sequencing revealed that dietary xylanase altered the composition of the intestinal microbiota and directly promoted the proliferation of Allobaculum stercoricanis which could produce butyrate in vitro. Consequently, dietary xylanase supplementation increased the butyrate level in fish gut. Further experiment verified that butyrate supplementation enhanced the expression of il-17d and regenerating islet-derived 3 gamma (reg3g) in the gut. The knockdown experiment of il-17d confirmed that il-17d is necessary for butyrate to protect Nile tilapia from pathogen resistance. Flow cytometry analysis indicated that butyrate increased the abundance of IL-17D + intestinal epithelial cells in fish. Mechanistically, butyrate functions as an HDAC3 inhibitor, enhancing il-17d expression and playing a crucial role in pathogen resistance., Conclusion: Dietary xylanase significantly altered the composition of intestinal microbiota and increased the content of butyrate in the intestine. Butyrate activated the transcription of il-17d in intestinal epithelial cells by inhibiting histone deacetylase 3, thereby protecting the Nile tilapia from pathogen infection. This study elucidated how microbial-derived xylanase regulates host immune function, providing a theoretical basis for the development and application of functional enzymes. Video Abstract., (© 2024. The Author(s).)

This research evaluated the efficacy of mixed Bacillus strains probiotic supplements in mitigating acute thermal-induced stress in Nile tilapia (Oreochromis niloticus). Three experimental fish groups involved 135 Nile tilapia (49 ± 2 g); one control (no added probiotics), 0.5, and 1% of selected Bacillus strains (B. subtilis, B. licheniformis, and B. pumilus) for 58 days. After the feeding period, growth parameters, immunological parameters, stress biochemical markers, and antioxidant parameters in addition to genes related to stress and histopathological changes in fish, were assessed; subsequently subjected to heat shock at 36 ± 0.5 ◦C for 2 h. Before the heat challenge, our results exhibited a marked increase in the growth efficacy (P < 0.05), lower marked serum levels of triglycerides and cholesterol, and tissue malondialdehyde (MDA) levels along with significantly increased superoxide dismutase (SOD) and catalase (CAT) enzymes activity in fish-fed Bacillus probiotic at 0.5% concerning the control group (P < 0.05). There were no significant changes in the serum levels of glucose, cortisol, lactate, phagocytic activity, respiratory burst (ROS), total immunoglobulin Ig, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), total protein, albumin, globulin, uric acid, urea, creatinine, as well as HSP70, GST, and GPx mRNA expression in most of the probiotic groups compared to the control group (P > 0.05). When Nile tilapia was exposed to heat stress, supplementation with Bacillus probiotic in the diet significantly decreased most of the indices related to serum biochemical (ALT (P < 0.01; P < 0.001), AST (P < 0.01), LDH (P < 0.01), urea (P < 0.05), and creatinine (P < 0.01)), triglycerides (P < 0.001; (P < 0.01)), cholesterol (P < 0.01; (P < 0.05)), glucose (P < 0.001), and cortisol (P < 0.01; (P < 0.05)), with tissue oxidative stress MDA levels (P < 0.05), and HSP70 mRNA expression (P < 0.01; P < 0.001), aligned with the stressed control group. In addition, a notable upsurge in the total protein, albumin, globulin, phagocytic and ROS activities, and total Ig, as well as the enzymatic antioxidant ability (SOD, CAT) (P < 0.01), with GST and GPx mRNA expression (P < 0.05; P < 0.01), were shown in fish-fed Bacillus spp. post-exposure compared with the stressed control group. Besides, no histopathological alterations were revealed in the spleen and brain of fish pre- and post-heat exposure. According to our findings, diet supplementation of Bacillus species has the potential to combat the suppressive effects of heat shock in Nile tilapia., (© 2024. The Author(s).)

River pollution can harm human health through direct contact, drinking water, and the consumption of contaminated fish and irrigated agricultural products. Surface water and Nile tilapia (Oreochromis niloticus) samples were collected monthly from July 2022 to June 2023 at three sites (El-Rahawy, Sabal, and Tala) along the Rosetta Nile branch in Egypt to monitor the presence of eight trace elements. The potential human health risks from consuming contaminated fish were also assessed. Iron and manganese were consistently detected in all water samples across most seasons and locations, with concentrations generally below the WHO permissible levels. All 72 analyzed fish muscle samples were found to contain trace elements. The mean concentrations of metals in the fish muscle samples, in descending order, were: iron > zinc > copper > manganese > tin > antimony > lead > mercury. Significant spatial and seasonal variations were observed in both water and fish samples. El-Rahawy was identified as the most contaminated site, with summer exhibiting the highest contamination rate compared to other seasons. Fish samples collected from El-Rahawy demonstrated the highest bioconcentration factor (BCF) values for most elements, particularly mercury, lead, iron, manganese, and antimony. Target hazard quotient (THQ) calculations for the trace elements in Nile tilapia muscles revealed that all trace elements, except antimony, had THQ values below 1, suggesting that consuming Nile tilapia from these sites is unlikely to cause adverse health effects. However, THQ values for antimony exceeded the threshold of 1, indicating a potential health risk for consumers. Although the detected trace elements in the fish were below the permissible toxicity limits, some could pose a future threat to human health, necessitating further studies, ongoing monitoring, and preventive measures., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Lowering nanoparticles (NPs) toxicity before discharge into aquatic environments and employing agricultural waste materials for environmental sustainability are necessary nowadays. Since this has never been done, this work examines how green CuO NPs treated with rice husk (RH) as a bio-adsorbent may be safer for Nile tilapia (Oreochromis niloticus) than chemically manufactured ones. So, five groups of fish were randomly placed in glass aquaria. One group was a control, and four groups received 50 mg/L green and chemically produced CuO NPs (GS and CS) with and without RH for 24, 48, and 96 h. RH was collected from all groups, and the results showed GS-CuO NPs had a greater adsorptive capacity than CS-CuO NPs after all time intervals. After analyzing fish indicators in all groups compared to the control, higher Cu bioaccumulation was exhibited in the liver and gills. The liver and gills showed elevated levels of glutathione peroxidase (GPx), catalase (CAT), and thiobarbituric acid reactive substances (TBARS), while the levels of glutathione reduced (GSH) were significantly lower. In addition, Cu exposure impaired liver and gill histology. Finally, our results indicated that using RH as an adsorbent for CuO NPs after their green synthesis instead of chemical synthesis before they enter the aquatic environment can enhance the overall health of fish and environmental sustainability., (© 2024. The Author(s).)

Background: Hypoxia stress resulted in mortality during the fish aquaculture program, affecting the sustainable development of the aquaculture industry. The Egyptian strain of O. niloticus showed a strong ability to hypoxia. In this study, a Nile tilapia strain that was kept and selected for 45 years by the author's team was used to elucidate the mechanism of the hypoxia response in the liver, including the identification of metabolic pathways and genes, involved in the hypoxia response of this strain., Results: The effects of hypoxia stress were detected at 0-hour, 6-hour, and 72-hour time points (0 h, 6 h, 72 h) on tilapia liver at 1 mg/L dissolved oxygen conditions. The blood triglyceride, blood glucose and cholesterol values exhibited significantly different change trends, but the hemoglobin content showed no significant differences between 0 h, 6 h and 72 h (P > 0.05). The activities of catalase (CAT), glutathione peroxidase (GSH-PX), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), and acid phosphatase (ACP) in the liver tissue gradually increased at 0 h, 6 h and 72 h (P < 0.05). Histological analyses revealed structural changes in intracellular lipid droplets, nuclear migration and dissolution, and cell vacuolization in liver tissues. Six pathways were identified as the main enriched metabolic pathways according to the transcriptome profiling analysis, which were protein processing in endoplasmic reticulum, steroid biosynthesis, peroxisome, PPAR signaling pathway, glycolysis/gluconeogenesis and Insulin signaling pathway. The expressions of the important differentially expressed genes were verified by qPCR analysis, including erola, LOC100692144, sqle, cratb, pipox, cpt1a2b, hik and acss2l, ehhadh, prkcz, fasn and plaa, which showed the same expressions trends as those of RNA-Seq., Conclusions: The Nile tilapia strain improves the abilities of hypoxia response through energy metabolism. Antioxidant enzyme measurements in the liver indicate that these five antioxidant enzymes play important roles in protecting the body from hypoxic damage. The histological changes in liver cells indicate that the damage caused by hypoxia stress. The immune-related metabolic pathways and energy metabolism-related pathways were obtained by transcriptome profiling, and these metabolic pathways and the differentially expressed genes selected from these metabolic pathways may be involved in the mechanism of hypoxia tolerance in this strain. These findings provide a better understanding of the hypoxia response mechanism of fish, and represent a useful resource for the genetic breeding of O. niloticus., (© 2024. The Author(s).)

The mechanism by which an organism can adapt to subtle environmental changes is predicated on modifications to biochemical processes within the cellular metabolism in response to such changes. Changes in these processes have the potential to induce alterations in cellular structures and tissue organization, as well as establish a causal link between fluctuations in these parameters and stressors exposure. This investigation's main goal and innovation is to evaluate the environmental stress indicators in the aquatic ecosystem of Lake Qarun. Pesticide residues in freshwater fish should be the primary focus of evaluation of environmental stressor concentrations, since they serve as bioindicators at different times and places on a spatiotemporal scale. A thorough analysis of suggestive biochemical biomarker reactions should also be conducted. The effects of environmental stressors, specifically pesticide contamination in Qarun Lake, have been observed and investigated in relation to two fish species: Solea aejabtiaca and Oreochronis niloticus. The results of a hazard assessment conducted at six sampling sites using spatio-temporal data revealed elevated mean values for the pesticides, persistent organic pollutants (POPs), organochlorines, organophosphates, and pyrethroids that were detected. A multi biomarker approach facilitates a more comprehensive understanding of stress responses induced by exposure to pollutants. As a result, the activities of the biochemical biomarkers CYP-450, GST, GSH, and LDH in the blood and liver of fish samples were found to be notably elevated. The suitability of the identified variables for biomonitoring of aquatic pollution was validated, and the data unveiled variations in sensitivity among species, implying that Nile tilapia could potentially function as a bioindicator with high sensitivity. The findings were correlated with the concentrations of detrimental organochlorines, organophosphorus, and pyrethroids in the muscles and gills. The data indicates that pollutants linked to agricultural wastes, runoff, and municipal effluent may be discharged into the lake ecosystem. Consequently, to safeguard the environment, it is essential to enforce and implement policies, acts, and regulations that already exist. Assessing the effects of additional environmental stressors on aquatic ecosystems is another way in which biomarker screening with an integrative approach improves our comprehension of how toxicants impact various levels of biological organization and is particularly useful in realistic environmental exposure scenarios., (© 2024. The Author(s).)

MicroRNAs play crucial regulatory roles in various aspects of development and physiology, including environmental adaptation and stress responses in teleosts. RT-qPCR is the most commonly used method for studying microRNA expression, with the accuracy and reliability of results depending on the use of an appropriate reference gene for normalization. This study aimed to evaluate seven miRNAs (U6, Let-7a, miR-23a, miR-25-3, miR-103, miR-99-5, and miR-455) expression stability in different tissues of Nile tilapia subjected to osmotic stress. Fish were divided into two groups: a control and an experimental group, raised in 0 and 12 ppt salinity water respectively. After 21 days, brain, gills, liver, and posterior intestine were collected for analysis. Different mathematical algorithms (geNorm, NormFinder, BestKeeper, and the comparative ΔCt method) were employed to identify the most suitable reference miRNAs. The results indicate that the miR-455/miR-23a combination is a robust reference for normalizing miRNA expression levels in studies of osmotic stress responses in Nile tilapia. The stability of miRNA expression can vary depending on specific stress conditions and biological processes, underscoring the necessity of selecting appropriate normalizing miRNAs for each experimental context. This study identifies reliable reference genes for future RT-qPCR analyses of miRNA expression, thereby enhancing our understanding of molecular responses in fish to environmental challenges. These insights are fundamental to the development of new technologies for the improved management and sustainability of aquaculture practices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Endocrine synchronization is a biological process often associated with social bonding. The mechanisms that mediate this process have been well studied in many vertebrate clades with evolved complex social behaviors. However, studies focusing on such processes in the less neurologically complex teleost clade are surprisingly lacking. In this study, we investigated the hypothesis that mated pairs of convict cichlids (Amatitlania nigrofasciata) perform cortisol synchronization and that the disruption of this might accompany pair-bond instability. Mated pairs were subjected to both behavioral and non-invasive waterborne hormonal assays to better understand the biological complexity of endocrine synchrony and its role in pair-bonding. Baseline cortisol assays indicated a positive correlation between male and female cortisol levels. Individuals that were subjected to a prolonged separation from their mate exhibited a negative correlation in cortisol synchrony after being reunited with their mate. Cortisol synchrony was disrupted, but pairs did not show a significant variance of intrapair aggression after initial pair reunion. However, more than half of the pairs that received the stressor exhibited significantly higher levels of intrapair aggression than their time matched controls approximately 1-7 days following this reunion, indicating pair-dissolution. Concurrently, pairs who underwent the stressor but maintained their bonds did not display an increase in intrapair aggression and also re-synchronized their cortisol levels. Not only does this study provide crucial insights in regard to the role of cortisol synchrony in serially monogamous systems, but it also suggests that the mechanisms that mediate the synchronization of endocrine through the formation of social bonds are more evolutionarily conserved than originally thought., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The Nile Tilapia (Oreochromis niloticus), a gonochoristic teleost fish with a XX/XY sex-determination system, is an ideal model for investigating gonadal sex differentiation. During gonadal differentiation, the expression of cyp19a1a in XX gonads and dmrt1 in XY gonads are required for undifferentiated tissues to develop into ovary or testis. In this study, quantitative real-time RT-PCR assessed the expression of cyp19a1a and dmrt1 genes in gonads and tail fin tissues. Differences in gene expression mean among sexually differentiated fish were analyzed using two-way analysis of variance (ANOVA) and validation of mixed model using discriminant analysis (DA) for morphometric traits and the gene expression in gonads and tail fin tissues used to validate and utilize them in discriminating sexes in sex-differentiated Nile Tilapia fish. The results revealed that, cyp19a1a gene expression in female ovaries was more significant than dmrt1 in male testis. In the other hand, the dmrt1 gene expression in the tail fin was higher in males than females. Both, cyp19a1a and dmrt1 genes, can discriminate fish sexes by 100% by using their expression in tail fin tissues. In conclusion, the cyp19a1a and dmrt1 genes could be used as a genetic marker to discriminate between the Nile Tilapia sexes, whereas used as an indicator for ovarian or testis differentiation in sexually differentiated Nile Tilapia using tail fin tissues. It is worth mentioning that this is the first investigation for using cyp19a1a and dmrt1 genes from Nile Tilapia tail fin tissues in sex determination., (© 2024. The Author(s).)

Aflatoxin B1 (AFB1) is a plant-origin toxin that could induce oxidative stress in fish. The micromineral selenium (Se) possesses well-documented antioxidant properties. To assess the ameliorative effects of SeNPs (1 mg/kg fish feed) on oxidative stress induced by AFB1 (500 μg/kg fish feed), Nile tilapia (32.2±1.7 g body weight) were distributed randomly and even in six groups for 8-week feeding trial. Live enzymes, AST, ALT, and ALP levels were increased in the serum of fish fed AFB1-contaminated diet, and the addition of SeNPs could restore normal values compared to the control. The gene expression of antioxidant enzymes, superoxide dismutase (SOD) enzyme and catalase (CAT) enzyme, and DNA fragmentation were significantly increased in response to aflatoxin exposure, while dietary SeNPs could mitigate the generated oxidative stress. The innate immunity, serum antibacterial activity (SAA), oxidative burst activity (OBA), phagocytic activities (PA and PI), and gene expression of cytokines (interleukin (IL)-1β, heat shock protein70 (Hsp), and tumor necrosis factor (TNF)-α) revealed a status of immunosuppression in Nile tilapia fed on AFB1-contaminated diet. These findings showed that fish became more vulnerable to Streptococcus agalactiae infection with a high mortality rate while dietary SeNPs provided a high relative protection level (RPL). From the obtained findings, SeNPs could mitigate the oxidative stress induced by feeding the AFB1 diet and could boost the immunity of stressed Nile tilapia., (© 2023. The Author(s).)

This study concerns the synthesis of the florfenicol (FF) metabolites florfenicol amine (FFA), florfenicol alcohol (FFOH), and monochloroflorfenicol (FFCl), for their subsequent use as reference standards in On-line solid-phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry (SPE-UHPLC-MS/MS) analysis. The metabolites were characterized using 1 H and 13 C NMR, as well as HRMS, and their purities were confirmed by quantitative NMR to ensure analytical reliability. Validation of the developed analytical method showed that it presented acceptable performance, with linearity >0.99 for all the target analytes, accuracies within ±10 % of nominal concentrations, and intra- and inter-day precisions within 15 %. Application of this method to fillets from fish that had been treated with florfenicol (dose of 10 mg/kg bw daily) demonstrated its effectiveness in consistently detecting FF and its metabolites throughout the treatment. The results emphasized the utility of the method for enhancing pharmacokinetic and residue depletion research. The ability to precisely monitor the drug and its metabolites in treated fish provides important insights into florfenicol metabolism, laying the groundwork for further comprehensive profiling studies of metabolites in fish tissue., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Innate social behaviors like aggression are modulated by sex steroid hormones such as androgens and estrogens. However, we know little about how the same hormone regulates similar behaviors in both sexes. We investigated the role of androgenic signaling in the regulation of aggression in Astatotilapia burtoni, a social fish in which males and females perform similar aggressive behaviors. We used androgen receptor (AR) α knockout (KO) animals for this study since this gene was recently shown to be required for male-typical aggression and mating. Surprisingly, ARα KO females did not show deficits in aggression. We also determined that females lacking the other AR, ARβ, showed normal levels of aggression. Blocking both ARs pharmacologically confirmed that neither AR is necessary for aggression in females. However, ARα KO males showed clear deficits in attacks. Thus, in A. burtoni there appears to be a sexual dimorphism in the role of ARα in the control of aggression., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The daily variations of temperature are one of the main synchronizers of the circadian rhythms. In addition, water temperature influences the embryonic and larval development of fish and directly affects their metabolic processes. The application of thermocycles to fish larvae has been reported to improve growth and the maturation of the digestive system, but their effects on metabolism are poorly understood. The aim of the present study was to evaluate the effect of two different temperature regimes, cycling versus constant, on the daily rhythms of metabolic factors of Nile tilapia (Oreochromis niloticus) larvae. For this purpose, fertilized eggs were divided into two groups: one reared in a 31 °C:25 °C day:night thermocycle (TCY) and another group maintained in a constant 28 °C temperature (CTE). The photoperiod was set to a 12:12 h light/dark cycle. Samples were collected every 4 h during a 24-h cycle on days 4, 8 and 13 post fertilization (dpf). The expression levels of alanine aminotransferase (alt), aspartate aminotransferase (ast), malic enzyme, glucose-6-phosphate dehydrogenase (g6pd), phosphofructokinase (pfk) and pyruvate kinase (pk) were analyzed by qPCR. Results showed that, in 13 dpf animals, most of the genes analyzed (alt, ast, malic, g6pd and pfk) showed daily rhythms in TCY, but not in the group kept at constant temperature, with most acrophases detected during the feeding period. An increase in nutrient metabolism around feeding time can improve food utilization and thus increase larval performance. Therefore, the use of thermocycles is recommended for tilapia larviculture., Competing Interests: Declaration of competing interest The authors whose names are listed immediately below certify that they have NO affi liations with or involvement in any organization or entity with any fi nancial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-fi nancial interest (such as personal or professional relationships, affi liations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Low temperatures significantly influence feeding behavior in ectothermic vertebrates, but the underlying mechanisms remain elusive. This study investigated the role of transient receptor potential ankyrin 1 (TRPA1) channels in mediating the appetite-suppressing effects of low temperature in Nile tilapia. TRPA1 was found to be highly expressed in the hypothalamus and co-localized with neuropeptide Y (NPY) neurons. Exposure to low temperatures reduced feeding frequency and increased TRPA1 expression. In vitro experiments demonstrated that low temperature and TRPA1 agonists induced calcium influx, which was blocked by a TRPA1 inhibitor. TRPA1 expression exhibited post-prandial increases and was downregulated by fasting. TRPA1 activation dose-dependently inhibited food intake, while its inhibition restored feeding suppressed by low temperature. TRPA1 activation downregulated orexigenic factors and upregulated anorexigenic factors through Ca 2+ /calmodulin-dependent pathways. These findings suggest that TRPA1 plays a crucial role in sensing low temperatures and regulating feeding behavior in tilapia., Competing Interests: Declaration of competing interest No conflicts of interest, financial or otherwise, are declared by the authors., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In mammals, siglec7, an integral component of the siglecs, is principally found on the surface of natural killer (NK) cells, macrophages, and monocytes, where it interacts with various pathogens to perform immunological regulatory activities. Nonetheless, the immune defense and mechanism of siglec7 in early vertebrates remain unknown. In this study, we identified siglec7 from Oreochromis niloticus (OnSiglec7) and revealed its immune functions. Specifically, OnSiglec7 was abundantly expressed in immune-related tissues of healthy tilapia and its transcription level was strongly activated after being challenged with A. hydrophila, S. agalactiae, and Poly: IC. Meanwhile, OnSiglec7 protein was purified and analyzed, which could recognize multiple pathogens through binding and agglutinating activity. Moreover, OnSiglec7-positive cells were mainly distributed in non-specific cytotoxic cells (NCC) of tilapia HKLs and showed cell membrane localization. Furthermore, OnSiglec7 blockage affected multiple innate immune responses (inflammation, apoptosis, and pyroptosis process) by regulating the activation of MAPK, NF-κB, TLR, and JAK-STAT pathways. Finally, OnSiglec7 blockage also greatly enhanced the cytotoxic effect of tilapia NCC. Summarily, this study uncovers immune functions and mechanisms of siglec7 in primitive vertebrates, thereby enhancing our understanding of the systemic evolution and ancient functions of other siglecs within the host's innate immune system (to our knowledge)., Competing Interests: Declaration of competing interest The authors declare that there were no financial or commercial connections which could be perceived as a conflict of interest during the research., (Copyright © 2024. Published by Elsevier B.V.)

The study investigated the impact of N-acetyl cysteine on growth, immune response, and antioxidant activity in tilapia (Oreochromis niloticus). Fish were reared at three densities (1.50, 3.00, and 4.50 kg/m3) with four levels of N-acetyl cysteine supplementation (0, 2, 4, and 6 mg/kg) over 60 days. Better growth was observed at low density, but at all densities, fish fed the highest N-acetyl cysteine level (6 mg/kg) showed improved growth. Chemical composition of fish and activity of amylase, lipase and protease in all treatments were noted to be insignificant. The levels of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and cortisol in HD treatments were high as compared to LD and MD treatment. However, fish fed with N3 diet in each density treatment showed the lowest level of antioxidant enzymes as well as cortisol. Similarly, the levels of malondialdehyde were noted to be high at HD treatments as compared to that in LD and MD. Its levels were lower in fish fed with N3 diets in all density treatments. Expression of somatostatins-1 did not increase in MD and HD treatments in response to high stocking density when compared with LD treatment. However, pro-opiomelanocortin-α level was reduced after N3 diet in HD treatment and interleukin 1-β expression increased after N3 supplement in HD treatment. In conclusion, N-acetyl cysteine supplementation improved growth and antioxidant response in tilapia. The most optimum dose of N-acetyl cysteine was noted to be 6 mg/kg at high stocking, suggesting the potential role of this nutraceutical in tilapia intensive culture., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Komal et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)