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Nanotechnology is an emerging avenue employed in disease prevention and treatment. This study evaluated the antimicrobial efficacy of chitosan nanoparticles (CSNPs) against major bacterial and oomycete fish pathogens in comparison with chitosan suspension. Initially, the minimum inhibitory concentrations (MIC, MIC90) were determined and the per cent inhibition of bacterial growth was calculated. Subsequently, the minimum bactericidal concentrations (MBCs) were determined. The time‐dependent disruptions of CSNP‐treated pathogens were observed via transmission electron microscopy (TEM), and the effect of CSNPs on the viability of two fish cell lines was assessed. No antimicrobial effect was observed with chitosan, while CSNPs (105 nm) exhibited a dose‐dependent and species‐specific antimicrobial properties. They were bactericidal against seven bacterial isolates recording MBC values from 1 to 7 mg/ml, bacteriostatic against four further isolates recording MIC values from 0.125 to 5 mg/ml and fungistatic against oomycetes recording MIC90 values of 3 and 4 mg/ml. TEM micrographs showed the attachment of CSNPs to the pathogenic cell membranes disrupting their integrity. No significant cytotoxicity was observed using 1 mg/ml CSNPs, while low dose‐dependent cytotoxicity was elicited by the higher doses. Therefore, it is anticipated that CSNPs are able to compete and reduce using antibiotics in aquaculture.

This study aims to assess the impact of microplastics (MPs) on erythrocytes using eryptosis (apoptosis) and an erythron profile (poikilocytosis and nuclear abnormalities), considered to be novel biomarkers in Nile tilapia (Oreochromis niloticus). In this study, four groups of fish were used: The first was the control group. In the second group, 1 mg/L of MPs was introduced to the samples. The third group was exposed to 10 mg/L of MPs. Finally, the fourth group was exposed to 100 mg/L of MPs for 15 days, following 15 days of recovery. The fish treated with MPs experienced an immense rise in the eryptosis percentage, poikilocytosis, and nuclear abnormalities of red blood cells (RBCs) compared with the control group in a concentration-dependent manner. Poikilocytosis of MP-exposed groups included sickle cell shape, schistocyte, elliptocyte, acanthocyte, and other shapes. Nuclear abnormalities of the MPs-exposed groups included micronuclei, binucleated erythrocytes, notched, lobed, blebbed, and hemolyzed nuclei. After the recovery period, a greater percentage of eryptosis, poikilocytotic cells, and nuclear abnormalities in RBCs were still evident in the groups exposed to MPs when crosschecked with the control group. The results show concerning facts regarding the toxicity of MPs in tilapia.

This study was conducted to determine for the first time the immunological, histopathological, histochemical, and ultrastructural changes; hematological and biochemical alterations; and poikilocytosis induced in Clarias gariepinus by Voliam flexi® 40% WG (thiamethoxam + chlorantraniliprole). Beside control fish, juvenile C. gariepinus were subjected to three sublethal concentrations of Voliam flexi® (43.5, 87.5, and 175 mg/L) for 15 days. Voliam flexi® induced immunotoxic impairments in C. gariepinus, such as a decrease in some immunity variables (lysozyme and phagocyte activity, immunoglobulin concentration, and nitro blue tetrazolium level). It also caused an extreme increase in the levels of primary cytokines (interleukin-1β and IL-6), compared with the control. The toxic effects of Voliam flexi® increased gradually with the increasing concentrations tested. Histological examination of the liver demonstrated necrosis, vacuolated hepatocytes (fatty deposition), melanomacrophage centers, foci of inflammatory cells, congested and dilated blood sinusoids, hepatic degeneration, fibrosis increment (Sirius Red stain), and glycogen depletion, as well as cytopathological alterations. We conclude that the toxic effects of Voliam flexi® must be restricted or prevented by using control mechanisms in aquatic systems.

Recently, research on the biological effects of microplastics (MPs) has grown exponentially. However, effects of MPs on freshwater fishes and the mechanisms of the biological effects of MPs were limited. So, the purpose of the current study was to clarify the effects of microplastics on oxidative stress response, DNA fragmentation, and proteinogram of the early juvenile stage of Nile Tilapia (Oreochromis niloticus). The fishes were assigned into four groups: one control, three MPs-exposed groups as 1 mg/L of MPs, 10 mg/L of MPs, and 100 mg/L of MPs respectively for 15 days and 15 days of recovery. The activities of superoxide dismutase, catalase, total peroxides, and oxidative stress index (OSI), as well as lipid peroxidation and DNA fragmentation, increased in groups exposed to MPs compared to the control group in a dose-dependent manner. In contrast, the activity of total antioxidant capacity decreased in groups exposed to MPs compared to the control group in a dose-dependent manner. The electrophoretic pattern of muscle proteins revealed alteration in the proteinogram in the MPs-exposed groups compared to control. After the recovery period, the activities of superoxide dismutase, catalase, total peroxides, total antioxidant capacity, lipid peroxidation, DNA fragmentation, and the electrophoretic pattern of muscle proteins returned to normal levels in 1 mg/L of MPs-exposed group. Combined with our previous work, these results suggest that MPs cause the overproduction of reactive oxygen species (ROS) and alters the antioxidants parameters, resulting in oxidative stress and DNA damage. The present study fosters a better understanding of the toxic effects of MPs on Tilapia as a freshwater model.

The present study was designed to investigate the protective role of dietary supplementation of Spirulina platensis (SP) against cytotoxic and genotoxic effects of lead nitrate in Clarias gariepinus. Four groups of fishes were used: first group as control which fed on basal diet, second group fed on basal diet and exposed to (1 mg/L of lead nitrate), third group fed on diet containing 0.25% SP and exposed to (1 mg/L of lead nitrate), and fourth group fed on diet containing 0.5%SP and exposed to (1 mg/L of lead nitrate). Fish samples were taken at 2nd and 4th week of exposure. The hematological indices of lead nitrate-exposed group were decreased significantly compared to the control group at 2nd and 4th week of exposure. Lead nitrate caused a significant increase in the percentage of poikilocytosis, micronuclei, and apoptotic cells as well as comet tail length and olive tail moment compared with the control group at 2nd and 4th week of exposure. The highest level of damage was found on 4th week of exposure with all parameters. Dietary inclusion of SP ameliorated these cytotoxic and genetic changes, as well as this amelioration was concentration and time dependent. Consequently, the present study proposed that the addition of SP to the fish diet can be used as a promising protective agent to oppose cytotoxic and genotoxic effects of lead nitrate in aquaculture. Graphical abstract.

The effects of Harness® toxicity on fish health are little known. So, current work aimed to study the impact of sub-lethal doses of Harness® (an acetochlor-based herbicide) on the African catfish, Clarias gariepinus, and also investigated the potential role of lycopene (LYCO) administration in alleviating Harness® negative effects. Fish were divided into five groups in triplicates as follows: group 1 (control) received no treatment, group 2 was exposed to 10 μm Harness®/L, group 3 was orally administered 10 mg LYCO/kg body weight and exposed to 10 μm Harness®/L, group 4 was exposed to 100 μm Harness®/L, and group 5 was orally administered 10 mg LYCO/kg body weight and exposed to 100 μm Harness®/L for 2 weeks. Some hemato-biochemical parameters, genotoxicity, and histopathological changes were assessed at the end of this period. Sub-lethal doses of Harness® altered the shape of erythrocytes in contrast to the control sample. Also, hematological parameters of exposed fish exhibited a significant (P0.05) reduction in the values of red blood cell count (RBCs), hemoglobin (Hb), hematocrit (HCT), and platelets (PL), as well as an insignificant (P0.05) drop in mean corpuscular volume (MCV). Harness® was also found to cause genotoxicity as well as histopathological alterations. LYCO administration decreased hemato-biochemical changes and returned them to near-normal levels. The findings showed that LYCO administration (10 mg LYCO/kg body weight) decreased Harness® toxicity in C. gariepinus and alleviated its destructive effects.

Pharmaceutical drugs in the aquatic environment can induce adverse effects on non-target organisms. The current study aims at evaluating the toxicity of hydroxychloroquine (HCQ) as pharmaceuticals residue in catfish (Clarias gariepinus) and the protective role of Spirulina platensis (SP). Four groups were used in this study:(1) a control group, (2) a group exposed to 3.16 mg/L of HCQ, (3) a group exposed to 3.16 mg/L of HCQ +10 mg/L of SP, and (4) a group exposed to 3.16 mg/L of HCQ +20 mg/L of SP for 15 days of exposure. The hydroxychloroquine-treated group showed a significant decline in the hematological indices, glucose, total protein, and antioxidants levels in relation to the control group, whereas the hydroxychloroquine-treated group showed a significant increase in the levels of creatinine, uric acid, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) as well as the percentage of poikilocytosis and nuclear abnormalities of RBCs in relation to the control group. The histopathological evaluation of the liver indicated dilation of central vein, vacuolization, degeneration of hepatocytes, and pyknotic nuclei as well as reduction of glomeruli, dilation of bowman's space, and degeneration of renal tubules in the kidney of the hydroxychloroquine-treated group. Spirulina platensis (SP) reduced the elevated levels of liver and kidney functions, poikilocytosis, and nuclear abnormalities of RBCs. Likewise, SP restored the depleted antioxidant defense system, the hematological indices, glucose, and total protein levels as well as rendered the histological architecture to normal status in a dose-dependent manner. Accordingly, the current study recommends the use of Spirulina platensis (SP) to remedy the toxic effects of hydroxychloroquine (HCQ).

This study records the extent of microplastics (MPs) in the surface water, sediments, and fishes of the Mediterranean and Red seas in Egypt. In sediment and water samples, the Ras Gharib station in the Red sea and Damietta and Port Said stations in the Mediterranean sea exhibited the highest microplastic abundance, while the lowest concentration was found in the Ain Sukhna station in the Red Sea and Marsa Matruh station in the Mediterranean sea. Rayon and polyethylene terephthalate were the most frequently found polymers in fishes. The results highlighted the abundant existence of microplastics in sediments, water, and fishes of the Mediterranean and Red seas, thereby improving our understanding of the environmental risks posed by microplastics to fisheries and marine ecosystems and the need for measures to diminish the flux of plastics to the marine settings.

Bio-nanotechnology employing bio-sourced nanomaterial is an emerging avenue serving the field of fish medicine. Marine-sourced chitosan nanoparticles (CSNPs) is a well-known antimicrobial and immunomodulatory reagent with low or no harm side effects on fish or their human consumers. In this study, in vitro skin mucus and serum antibacterial activity assays along with intestinal histology, histochemical, and gene expression analyses were performed to evaluate the impact of dietary CSNPs (5 g kg−1 dry feed) on rainbow trout resistance against ‘enteric redmouth’ disease. Two treatment conditions were included, short-term prophylactic-regimen for 21 days before the bacterial challenge, and long-term therapeutic-regimen for 21 days before the challenge and extended for 28 days after the challenge. Our results revealed higher antibacterial defense ability and positive intestinal histochemical and molecular traits of rainbow trout after dietary CSNPs. The prophylactic-regimen improved trout health while the therapeutic regimen improved their disease resistance and lowered their morbidity. Therefore, it is anticipated that CSNPs is an effective antibacterial and immunomodulatory fish feed supplement against the infectious threats. However, the CSNPs seem to be more effective in the therapeutic application rather than being used for short-term prophylactic applications.

Although microplastics (MPs) have received increasing focus and currently have become an emerging area of research, there is limited knowledge about their effect on whole body histology of fish. In this study, tilapia (Oreochromis niloticus) early juveniles were exposed to 1, 10, or 100 mg/L of MPs for 15 days and 15 days post-exposure, after which whole body histological examinations were performed. Histological analysis of kidney revealed congestion of blood capillaries, inflammatory cells, loss of basophilic cytoplasm in several tubules, vacuolated tubules, shrinking of convoluted tubules, widening of intertubular space, complete deformation, glomerular atrophy, vacuolated glomerular cells, and signs of fatty tubules. The liver tissue exhibited vacuoles, hydropic degeneration, necrotic area, severe deformation of hepatocytes, pyknotic nuclei, and dilation and congestion of blood sinusoids. The pancreatic tissue revealed shrunken and degenerated acini with pyknotic nuclei, hemorrhage, necrotic area, inflammatory cells, fatty cells, and congested blood capillaries. In the muscle tissue, fiber core dissociation, edema, necrosis, segmented fibers, and inflammatory cells were detected. The gill tissue demonstrated dilation and congestion of blood vessels, complete lamellar fusions, lifting of epithelium, shortening and degeneration of secondary lamellae, hyperplasia, and deposition of MPs between primary lamellae. In the spinal cord and notochord, the effects were degeneration and protrusion of meninges, deformation and deviation of notochord from its central axis, edema, degeneration of notochord (disappearance of vacuolar cells), deviation of spinal cord from the central axis, and loss of vacuolar cells in notochord. The intestinal tissue exhibited degeneration of basement membrane, inflammatory cells, goblet cells, atrophy of submucosa, pyknotic nuclei, hemorrhage, and vacuolization of mucosal cells. The histopathological changes in different organs were noticed even post-exposure in fish exposed to MPs compared to those in control fish and these changes were concentration dependent. In conclusion, these data together with our previous data suggest that MPs can cause different changes, ranging from biochemical alterations in single cells to lesions in the entire tissue, which can affect the vitality and life of fish.

Ultraviolet radiation-induced neurodegeneration has been studied in the early stages of development in fish, but not extensively in the adult stage. The present study aimed at investigating the effects of ultraviolet radiation-A (UVA) in adult Japanese medaka (Oryzias latipes). The brain, spinal cord, and retina were examined histopathologically as nervous system target organs. Japanese medaka fish were exposed to 15, 30, and 60 min day−1 UVA for 3 days, and samples were obtained 24 h and 14 days after UVA exposure. Neurohistopathological alterations in brain tissue included vacuoles, blood congestion, degeneration of neuropils, and pyknotic nuclei in neurons. Alterations in the spinal cord included neuronal cell degeneration, reduction in the spinal cord area, and degeneration of Mauthner cells. Retinal tissue showed vacuolation in the nerve fiber layer (NFL), pyknotic nuclei in the ganglion cell layer (GCL), and decreased cell populations particularly in the inner nuclear layer (INL) and GCL. The degree of degeneration was dependent on the duration of UVA exposure. The signs of degeneration decreased gradually and disappeared completely after the 14-day recovery period. In addition, p53-deficient medaka fish were more tolerant than were wild-type (Hd-rR) Japanese medaka. In conclusion, UV radiation induced neurodegeneration in the brain, spinal cord, and retina of adult Japanese medaka (Oryzias latipes) but their normal histological architecture reappeared in these tissues after 14 days.

The goal of present study is to determine whether metals or nanomaterials are transferred from exposed pregnant females of viviparous fishes to their developing offspring and the subsequent potential effects on the oxidative stress and histomorphological indicators. Gravid females of guppies (Poecilia reticulata) exposed to 1 mg/l copper sulfate (CuSO4) or copper oxide nanoparticles (CuO-NPs) for 17 to 25 days depending on giving birth. Once a female gave birth, the female and her newborn offspring were analyzed for copper concentrations while some oxidative stress parameters and histopathology were performed for the newborn offspring. There were no malformations or histopathological lesions observed in the newborn offspring of guppies exposed for either CuSO4 or CuO-NPs. Also, there was no maternal metal transfer for either CuSO4 or CuO-NPs while females exposed to copper sulfate only showed significantly higher concentrations of Cu compared to control group. In addition, there were non-significant changes in catalase compared to control group. While, glutathione decreased significantly in offspring their mothers exposed to CuO-NPs only compared to control group. In addition, superoxide radical and lipid peroxidation increased significantly in offspring their mothers exposed to CuSO4only compared to control group. The findings of the present study indicated that the offspring were more sensitive to CuSO4 than CuO-NPs. Although absence of metal Cu in the tissues of offspring as well as lack of morphological abnormalities and histopathology, maternal transfer of Cu metabolites may be suggested to be the causative factor for some oxidative stress.

In the present study, 120 fish specimens (64 male and 56 female) of the five-lined snapper, Lutjanus quinquelineatus of variable sizes were used for demonstration the morphometric and meristic characteristics of this species in the Egyptian Red Sea, Hurghada fishing area. The total length varied from 15.3 to 28.7 cm in males and from 16.0 to 31.7 cm in females while their weights ranged between 44 and 378 g in males and between 48 and 512 g in females. This fish species showed constant meristic characters. Statistical interpretation of morphometric data indicated that there is direct relationship between total body length with head length (HL), snout length (SnL), eye diameter (ED) and length of caudal peduncle (CPL). The meristic characters like dorsal fin rays, anal fin rays, lateral line scales, gill rakers on lower arm and scales in transversal line were counted. The results revealed that there is no sexual dimorphism in L. quinquelineatus from Hurghada fishing area.

Despite extensive research on the toxic effects of microplastics (MPs), there is no obtainable data on the use of phytobioremediation against MPs toxicity in fish. This study aimed to investigate the protective role of lycopene, citric acid, and chlorella against the toxic effects of MPs in African catfish (Clarias gariepinus) using hematology, biochemical, antioxidants, erythron profiles (poikilocytosis and nuclear abnormalities) and the accumulation of MPs in tissues as biomarkers. Five groups of fish received: normal diet (control); MPs (500 mg/kg diet) (Group 2); MPs (500 mg/kg diet) + lycopene (500 mg/kg diet) (Group 3); MPs (500 mg/kg diet) + citric acid (30 g/kg diet) (Group 4); and MPs (500 mg/kg diet) + chlorella (50 g/kg diet) (Group 5) for 15 days. Group 2 had significantly higher amounts of MPs in the stomach, gills, and feces, electrolyte imbalances (HCO3, Fe, Na+, K+, Ca+2, Cl−, and anion gap, hematobiochemical alterations, and decreases in the activities of superoxide dismutase, catalase, total antioxidant capacity, and glutathione S-transferases compared to the control group. Additionally, Group 2 had significant increase in the percentage of poikilocytosis, and nuclear abnormalities in RBC's compared to the control group. The co-treatment of MPs-exposed fish with lycopene, citric acid, and chlorella-supplemented diets ameliorated the hematological, biochemical, and erythron profile alterations, but only slightly enhanced the antioxidant activity. Overall, lycopene, citric acid, and chlorella can be recommended as a feed supplement to improve hematobiochemical alterations and oxidative damage induced by MPs toxicity in the African catfish (C. gariepinus).

There is a scarcity of knowledge about the impacts of microplastics (MPs) on the early juvenile stage of freshwater fish. The current study aims to inspect the exposure and post-exposure recovery of microplastics (MPs) on accumulation and blood biomarkers of Nile Tilapia (Oreochromis niloticus) early juvenile. Four groups of fishes were used; the first group was the control group, the second group was exposed to (1 mg/L of MPs), the third group was exposed to (10 mg/L of MPs), and the fourth group was exposed to (100 mg/L of MPs) for 15 days and 15 days of recovery. The results showed that significantly higher numbers of microplastics were observed in microplastics-exposed groups compared to control group. Biochemical parameters (creatinine, uric acid, AST, ALT, ALP, glucose, cholesterol, total protein, albumin, globulin, and A/G ratio) showed significant increment after exposure to microplastics for 15 days compared to control group in dose dependent manner. The hematological indices (RBC's count, Hb, Ht, MCHC, Platelets, WBC's count, and monocytes) showed a significant decline after exposure to microplastics for 15 days compared to control group, while MCV and MCH showed a significant increase after exposure to microplastics for 15 days. After the recovery period, microplastics accumulations, hemato-biochemical alterations were still detected in microplastics exposed groups compared to the control group except for WBC's count and MCV which return to normal levels. MPs caused anemia and perturbations in hemato-biochemical parameters which may cause mortality of tilapia early juvenile and should be considered in a program for monitoring hazard materials in the ecosystem.

The current work intended to inspect the hepato-nephrotoxicity of gibberellic acid (GA3) in juvenile of Oreochromis niloticus as well as the possibility of restoration after dietary addition of different concentrations of Spirulina platensis (SP). Fishes were evenly assorted into five groups: Group I assigned as control, Group II fed on basal diet and exposed to 150 mg/L gibberellic acid (GA3). The 3rd, 4th, and 5th groups exposed to150 mg/L gibberellic acid (GA3) and previously fed for two months on SP supplemented diets at levels of 5, 20, and 100 g/kg, respectively. Fish serum were utilized to check glucose, total protein, hepatic and renal functions, enzymatic and non-enzymatic antioxidants activities (superoxide dismautase; SOD, catalase; CAT, and total antioxidant capacity; TAC) as well as histopathological alterations in liver and kidney. The results showed that creatinine, uric acid, liver enzymes, glucose, total protein, SOD, and CAT were significantly elevated in GA3-treated group. Liver of GA3-treated fish manifested some histopathological changes (hypertrophy, cytoplasmic vacuolization, and apoptotic cells with pyknotic nuclei, necrosis, dilated blood sinusoids, and lymphocytic aggregation around the central veins). Kidney of GA3-exposed fish revealed edema of the epithelium lining of some renal tubules and some showed vacuolar degeneration and dissociation. Hypertrophy in the glomerulus was observed with dilated blood capillaries. SP supplementation restored these biochemical, antioxidants, and histological changes near to control levels. This improvement was higher with 100 g/kg SP showing concentration dependency. According to this study we can conclude that SP supplementation can improve the hepato- and nephrotoxicity caused by GA3 exposure indicating its role as potent antioxidant food additive.

Chitosan nanoparticles (CSNPs) are the nanostructures of chitosan biopolymer which is derived from chitin polysaccharide, the main component of crustacean shells. Chitosan is a biocompatible, nontoxic and biodegradable polymer soluble in acidic solutions and easily excreted from kidneys. It is widely used in medical and pharmaceutical applications including artificial matrices for tissue engineering, drug transport, targeted drug delivery and protein or gene delivery. The antimicrobial activities of chitosan and CSNPS against different bacterial, fungal and viral pathogens made them valuable for several biological applications including food preservation purposes. In addition, they have immunomodulatory effects on fish and crustaceans providing direct positive impact on aquaculture and fish farming industry. Sustained release of some bioactive ingredients such as hormones, vitamins, nutrients and antioxidants has improved the biological activities of fish. Furthermore, CSNPs have recently been employed to diagnose fish diseases. In this review, we present the medical and biological applications of chitosan and CSNPs on aquatics to provide an update on recent advances and the potential for further advanced applications for aquaculture in the future.

Pyrazole derivatives display diverse biological and pharmacological activities. The aim of this study is to investigate the antioxidant properties of a novel pyrazolecarboxamide derivative (4-amino-N-[(4-chlorophenyl)]-3-methyl-1-phenyl-1H-thieno [2, 3-c] pyrazole-5-carboxamide) in African catfish, Clarias gariepinus, exposed to 1 mg/L PbNO3. Fish were intramuscularly injected with pyrazole-5-carboxamidederivative according to the following groupings: Group 1 (control), Group 2 (1 mg/L lead nitrate), Group 3 (1 mg/L lead nitrate + 5 mg pyrazole derivative/kg body weight), and Group 4 (1 mg/L lead nitrate + 10 mg pyrazole derivative/kg body weight) for two weeks and four weeks. Lead nitrate (1 mg/L) caused significant elevation of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, uric acid, cholesterol, and glucose-6-phosphate dehydrogenase (G6PDH) compared to the control group after two and four weeks of exposure, while serum total lipids, alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) were significantly reduced compared to the control group. Furthermore, levels of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and total antioxidant capacity (TAC) were reduced in group 2 compared to the control group. However, in group 2, hepatic lipid peroxidation (LPO) and DNA fragmentation percentage were significantly increased compared to the control group. Histopathological changes in the liver of lead-exposed groups included marked disturbance of hepatic tissue organization, degeneration of hepatocytes, dilation of blood sinusoids and the central vein as well as necrosis. Injection of pyrazole derivative for two weeks and four weeks reversed alterations in biochemical parameters, antioxidant biomarkers, lipid peroxidation, hepatic DNA damage, and histopathological changes in liver tissue induced by 1 mg/L lead nitrate. This amelioration was higher in response to high-dose pyrazole derivative (10 mg) at the fourth week of exposure, showing concentration-and time-dependency. Overall, the sensitized derivative pyrazolecarboxamide is likely a useful tool to minimize the effects of lead toxicity due to its potent antioxidant activity.

This study investigates for the first time in vivo potential release of bound microcystins (MCs) from edible fish tissues. Bound MCs were released in the mouse digestive system and reached the liver (2.1–14.3 ng g−1) and blood (1–5 ng ml−1). The released MCs were active and negatively affected liver functions of treated mice. The estimated daily intake (EDI) for bound MCs (93.5 μg kg−1 day−1) is about 2300 times higher than the WHO safe EDI (0.04 μg kg−1 day−1), compared to lower EDI for free MCs (0.002 μg kg−1 day−1). Therefore, bound MCs in fish tissues should be considered when fish are monitored for human consumption.

The antioxidant role of the green tea (Camellia sinensis) extract (GTE) was examined to remedy the toxic effects of (0.2mgl-1) 4-nonylphenol(4-NP). Biochemical parameters, antioxidant enzymes, liver lipid peroxidation (LPO), DNA fragmentation, and apoptosis as well as histopathology of liver of African catfish Clarias gariepinus were considered. Catfishes were divided into four groups: first group (control), second group (0.2mgl-1 of 4-NP), third group (0.2mgl-1of 4-NP +100mg GTE l-1water), and fourth group (0.2mgl-1 of 4-NP +200mg GTE l-1water). The results showed that significant increments of serum glucose, AST, ALT, total protein, total lipids, cholesterol, G6PDH, and cortisol. Meanwhile, serum acetylcholinesterase, ALP, and LDH were significantly reduced. In addition, antioxidant enzymes (SOD, CAT, GST, and TAC) levels were reduced in 4-NP treated fish compared to control. Also, there were significant increments in hepatic LPO, DNA fragmentation, and apoptotic erythrocytes in 4-NP treated fish compared to control. Liver of 4-NP treated fish showed some histopathological alterations such as, vacuolization in hepatocytes, congestion in central vein, infiltration of mononuclear inflammatory cells, and necrosis as well as depletion of glycogen content of liver. Addition of green tea extract into the water restored the alterations in most of those biomarkers induced by 4-NP. We concluded that, GTE has a protective role against hepatic failure, depletion of antioxidant defense, and genotoxicity induced 4-NP in C. gariepinus.

Proteomic analyses techniques are considered strong tools for identifying and quantifying the protein contents in different organisms, organs and secretions. In fish biotechnology, the proteomic analyses have been used for wide range of applications such as identification of immune related proteins during infections and stresses. The proteomic approach has a significant role in understanding pathogen surviving strategies, host defence responses and subsequently, the fish pathogen interactions. Proteomic analyses were employed to highlight the virulence related proteins secreted by the pathogens to invade the fish host’s defence barriers and to monitor the kinetics of protein contents of different fish organs in response to infections. The immune related proteins of fish and the virulence related proteins of pathogens are up or down regulated according to their functions in defence or pathogenesis. Therefore, the proteomic analyses are useful in understanding the virulence mechanisms of microorganisms and the fish pathogen interactions thereby supporting the development of new effective therapies. In this review, we focus and summarise the recent proteomic profiling studies exploring pathogen virulence activities and fish immune responses to stressors and infections.

Although, silver nanoparticles (AgNPs) are used in many different products, little information is known about their toxicity in tropical fish embryos. Therefore, this study evaluated the developmental toxicity of waterborne silver nanoparticles in embryos of Clarias gariepinus. Embryos were treated with (0, 25, 50, 75ng/L silver nanoparticles) in water up to 144h postfertilization stage (PFS). Results revealed various morphological malformations including notochord curvature and edema. The mortality rate, malformations, and DNA fragmentation in embryos exposed to silver nanoparticles increased in a dose- and embryonic stage-dependent manner. The total antioxidant capacity and the activity of catalase in embryos exposed to 25ng/L silver nanoparticles were decreased significantly while the total antioxidant capacity and the activity of catalase were insignificantly increased with increasing concentrations in the embryos from 24 to 144 h-PFS exposed to 50 and 75ng/L silver nanoparticles. Lipid peroxidation values showed fluctuations with doses of silver nanoparticles. Histopathological lesions including severely distorted and wrinkled notochord were observed. The current data propose that the toxicity of silver nanoparticles in C. gariepinus embryos is caused by oxidative stress and genotoxicity.