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AbstractThe study of the DNA damage response in erythrocytes after exposure to volatile organic compounds (VOCs) can present evidence for its potential effect as genotoxic- biomarkers for environmental pollution. Although VOCs are dangerous pollutants, still little is known about hemotoxic, cytotoxic, and genotoxic effects of such pollutants on fish. We optimized an assay method for apoptosis and DNA damage in erythrocytes of adult tilapia fish after 15 days exposure to benzene (0.762 ng/L), toluene (26.614 ng/L), and xylene (89.403 ng/L). The highest level of apoptosis and DNA damage were recorded in benzene-exposed fish, as was the highest level of histopathological alterations in gills, liver, and kidney. The imbalance of the antioxidants profile explained the stress-case reported in exposed fish. These results suggest that hemotoxic, cytotoxic, genotoxic, and tissue damage were recorded after exposure to BTX in Oreochromis niloticus.

The use of plant growth regulators has led to environmental contamination of water bodies that occur adjacent to agricultural areas. Some of these chemicals are bioactive, not only to plants, but also to non-target exposed biota, namely of the aquatic compartment. Previous work demonstrated the establishment of hepato- and nephrotoxic effects in juvenile tilapia (Oreochromis niloticus) exposed via aquatic media to gibberellic acid (GA3), which is among the most used plant growth regulators, in agricultural practices. Here, we investigated the effect of GA3 on hematological indices, poikilocytosis, nuclear abnormalities, and genotoxic indices measured in Nile tilapia (Oreochromis niloticus), as well as the putative protective effects of dietary supplementation of Spirulina (Arthrospira platensis). Fish were evenly assorted into 5 groups: group I served as a control, and groups II–V were fed diets supplemented with Spirulina at rates of 0 g/kg, 5 g/kg, 20 g/kg, and 100 g/kg, respectively, for 2 months before being exposed to 150 mg/L GA3. The results revealed that GA3 exposure decreased significantly all hematological indices (P P > 0.05). GA3 exposure increased significantly the percentage of nuclear abnormalities, altered erythrocytes and the percentages of tail DNA, compared to the control group (P 3 on O. niloticus and suggests that the addition of Spirulina to fish diet can mitigate the hemotoxic effects of GA3.

Microplastic particles (MPs) are a common environmental pollutant easily ingested by fish in aquaculture. The current study evaluated the protective efficacies of some antioxidant, e.g., lycopene, citric acid, and chlorella, against the toxic effects of MP ingestion by Clarias gariepinus using histopathological biomarkers. Five experimental groups were established, a control group receiving only a standard diet, a group exposed to 500 mg/kg MP concomitant with the standard diet, and three antioxidant groups exposed to MPs plus either lycopene (500 mg/kg), citric acid (30 g/kg), or chlorella (50 g/kg) in the standard diet. After 15 days, fish were sacrificed for histological and histochemical examinations. Histological analysis of the kidney for group 2 (fed 500 mg/kg MPs alone) revealed distributed tissue dissociation, regional glomerular hypertrophy or shrinkage, melanomacrophage accumulation, and expansion of Bowman’s space, while liver tissue exhibited dilation and rupture of the central vein wall, hemorrhage, cytoplasmic vacuolation, and cellular necrosis or apoptosis. Fish exposed to MPs also exhibited connective tissue fiber accumulation around renal blood vessels, renal tubules, the central hepatic vein, hepatic blood sinusoids, and serosal, muscle, and submucosal layers of the intestine. In addition, MP exposure reduced carbohydrate (mainly glycogen) contents in the brush borders and basement membranes of renal tubules, glomeruli, and intestinal tissues as well as in the cytoplasm of hepatocytes. These signs of renal, hepatic, and intestinal histopathology were fully or partially reversed by dietary lycopene, chlorella, or citric acid. Enhancing dietary antioxidants is an effective strategy for preventing MP toxicity in Clarias gariepinus in aquaculture.

This study’s goal was to assess the catfish’s response to exposure to monoaromatic petroleum hydrocarbons (benzene, toluene, and xylene) and its recovery after exposure using oxidative stress, histopathological, and immunological changes as biomarkers. Four groups: one as control and other three exposed to benzene (0.762 ng/L), toluene (26.614 ng/L), and xylene (89.403 ng/L), respectively, for 30 days and then recovery period for 30 days. The levels of the cortisol, lipid peroxidation, and cytokines (IL-1β, IL-6) increased significantly (p p xylene > toluene even though after recovery period.

Due to its prevalence in aquatic environments and potential cytotoxicity, 4-nonylphenol (4-NP) has garnered considerable attention. As a medicinal plant with numerous biological activities, Nigella sativa (black seed or black cumin) seed (NSS) is widely utilized throughout the world. Consequently, this study aimed to examine the potential protective effects of NSS against 4-NP-induced hepatotoxicity in African catfish (Clarias gariepinus). To achieve this objective, 18 fish (351 ± 3 g) were randomly divided into three equal groups for 21 days. The first group serves as a control which did not receive any treatment except the basal diet. The second and third groups were exposed to 4-NP at a dose of 0.1 mg L−1 of aquarium water and fed a basal diet only or supplemented with 2.5% NSS, respectively. The histological, histochemical, and ultrastructural features of the liver were subsequently evaluated as a damage biomarker of the hepatic tissue. Our results confirmed that 4-NP was a potent hepatotoxic agent, as 4-NP-intoxicated fish exhibited many lesions. Steatohepatitis, ballooning degeneration, sclerosing cholangitis, and coagulative necrosis of melanomacrophagecenters (MMCs) were observed. Hemosiderin, lipofuscin pigments, and proliferation of fibroblasts, kupffer cells, and telocytes were also demonstrated in the livers of 4-NP-intoxicated fish. In addition, decreased glycogen content and increased collagen deposition were observed in the hepatic tissue. Hepatocytes exhibited ultrastructural alterations in the chromatin, rough endoplasmic reticulum, smooth endoplasmic reticulum, mitochondria, lysosomes, and peroxisomes. Co-administration of 2.5% NSS to 4-NP-intoxicated fish significantly reduced these hepatotoxic effects. It nearly preserved the histological, histochemical, and ultrastructural integrity of hepatic tissue.

This study examines the potential defending effects of the diatom, Amphora coffeaeformis, as a feed additive versus the deleterious effects (mainly on gonads) caused by microplastics (MPs) in Nile tilapia, Oreochromes niloticus. Groups of male tilapia were pre-fed diets with four different supplementation levels of A. coffeaeformis (0%, 2.5%, 5%, and 7.5%) for 70 days, then exposed to 10 mg/L MPs for 15 days. Thereafter, samples were taken from the four experimental groups and the control fish group, for evaluating blood picture, erythrocytes alterations, biochemical parameters, catalase (CAT), superoxide dismutase (SDO), and total antioxidant capacity (TAC). In addition, male reproductive performance was assessed by quantifying the follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T), also testicular sections and GSI% were also assessed. The results showed that the number of leucocytes were significantly (p < 0.05) higher, but the number of red blood cells (RBCs), the level of Hemoglobin (Hb), the percentage of Hematocrit (Ht), the number of platelets, and the eosinophil percentages were significantly decreased (p < 0.05) when fish exposed to MPs. Biochemical parameters (ALP, glucose, uric acid, albumin, and A/G ratio) were significantly increased after MP exposure compared with the control group. Furthermore, MPs induced a significant decline in both serum LH and T levels. Testicular, histological, degenerative changes and testis-ova were found in the MP-exposed fish. Thus, A. coffeaeformis supplementation displayed ameliorative properties that detoxified the negative effects of MPs. This study provides a better understanding of the reproductive injuries caused by MPs exposure and evidence for the use of A. coffeaeformis as a natural remedy in freshwater tilapia.

Although few studies have been done to evaluate the neurotoxic effect of 4-nonylphenol on the aquatic fauna, there is a shortage in knowledge about the effect of the dose-dependent damage of 4-NP in juvenile of C. gariepinus. So, the present study aims to investigate the neurotoxic effects of 4-NP in juvenile of Clarias garepinus through evaluation of oxidative stress indices, neurotoxic biomarkers, enzymatic and non-enzymatic antioxidants, and histopathological alterations. To carry out this work, healthy juvenile fish were categorized into four groups (seven fish/group; three replicates). One as control and the other three groups were exposed for 15 days to 4-nonylphenol concentrations as 0.1, 0.2, and 0.3 mg/L, respectively, then 15 days as recovery period. The neurotoxiclogical biomarkers and antioxidant parameters after exposure to 4-NP showed significant differences between treatments and the control (P

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.

Ultraviolet radiation is an ecological factor that directly affects terrestrial organisms through suppression of immunity or damage to internal organs. The present study assessed the effects of ultraviolet A (UVA) radiation on the kidneys of both wild-type (WT) and p53-deficient medaka (Oryzias latipes) and evaluated which strain was more resistant to the effects of UVA. Fish were divided into four groups: control group 1 (Cwt and Cp53), kept for 3 days without UVA exposure; group 2 (1wt and 1p53), fish exposed daily to UVA for 1 h day-1 for 3 days; group 3 (2wt and 2p53), fish exposed daily to UVA for 2 h day-1 for 3 days; and group 4 (3wt and 3p53), fish exposed daily to UVA for 3 h day-1 for 3 days. Samples of tissues were obtained 24 h after UVA exposure. The most obvious histopathological changes induced by UVA radiation in kidney tissues of both strains of medaka (WT and p53-deficient) were high levels of vacuolation of tubular cells followed by necrosis. The tubular segments lost their normal shape which appeared like a network structure and their cells with clear cytoplasm. Necrosis of lymphoid tissues and spots of brown pigmentation (possibly melanomacrophages) were sporadically seen in interstitial lymphoid tissues, while shrinkage of glomeruli, diminution of periodic acid-Schiff staining, and increased amount of collagenous fibers were observed. Our results confirmed the harmful effects of UVA radiation on kidney tissues of both WT and p53-deficient medaka. However, WT medaka was affected more than p53-deficient medaka.

Recently, the residues of some common and widely used herbicides (acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, and quinclorac) were detected in the surface water, soil, sediments, and fish tissues as the agricultural drainage problems. In this study, juveniles of Nile tilapia Oreochromis niloticus were exposed to sub-lethal concentrations of these herbicides as 2.625, 0.800, 36.00, 2.50, 1.275, and 11.250 mg/l for acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, and quinclorac respectively for 96 h. Some hemato-biochemical parameters were evaluated. In comparison with the control group, sub-lethal concentrations of all tested herbicides induced alterations in the shape of erythrocytes. Also, in all tested herbicides, hematological parameters of exposed fish exhibited a significant decrease in red blood cell count except bentazon. However, all tested herbicides showed an insignificant reduction in mean corpuscular hemoglobin concentration and total white blood cells except bensulfuron-methyl. For biochemical parameters, most tested herbicides induced a significant increase in levels of cholesterol, albumin, globulin, albumin/globulin ratio, activity of alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total plasma protein (only with acetochlor), urea, and creatinine (except bentazon and halosulfuron-methyl that exhibited non-significant decrease in creatinine level) compared with the control. In conclusion, the fish blood profiles can be used as good biomarkers for laboratory study to assess the toxicity of the tested rice herbicides at a sub-acute level especially acetochlor on O. niloticus. Graphical Abstract.

The present study investigates the nephrotoxic effects of two acute doses of silver nanoparticles (AgNPs) and silver nitrate (AgNO3) on the African catfish, Clarias gariepinus, using biochemical, histochemical, and histopathological changes as biomarkers. AgNP-induced impacts were recorded in some of these characteristics on the bases of their size (20 and 40 nm) and concentration (10 and 100 μg/L) but no significant interaction between size and concentration. AgNO3 had low significant adverse effects on some parameters in comparison with those impacts of AgNPs. The concentrations of creatinine and uric acid exhibited different significant variations under stress in all exposed groups compared with those in the control group. On the tissue and cell levels, histopathological changes were observed. These changes include hypertrophies of glomeruli, proliferation in the haemopoietic tissue, dissociation in renal tubules, shrinkage of glomerulus, hydropic degeneration, dilatation of renal tubules, aggregation of melanomacrophages, rupture of Bowman’s capsule, and the glomerular tuft and dilatation of Bowman’s space. In more severe cases, the degenerative process leads to tissue necrosis in the kidney of AgNP-exposed fish as well as carbohydrate depletion; a faint coloration was also observed in the brush borders and basement membrane with a large amount of connective tissue fibers around the blood vessels and the renal tubules. Recovery period for 15 days led to improvement of most of the alterations in biochemical, histopathological, and histochemical parameters induced by AgNPs and AgNO3. In conclusion, one can postulate on the sensitivity of the kidney of C. gariepinus to AgNPs and recovery strategy is a must.

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.

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 present study aimed to investigate the genotoxicity in erythrocytes induced after exposure of medaka (Oryzias latipes) to 4-nonylphenol (4-NP). Adult female medaka fish were exposed to 4-NP at three sublethal concentrations for 15 days to compare their sensitivity with that of catfish as an aquatic model. Comet assay and γ-H2AX were used as biomarkers to detect DNA damage in erythrocytes. Exposure to 4-NP resulted in an increase in the tail moment in a dose-dependent manner. The highest level of DNA damage was recorded after exposure to 100 μg/l 4-NP. The number of foci was increased after exposure to 4-NP, indicating damage to DNA. The present results confirmed the high level of morphological alterations and apoptosis of erythrocytes detected in the first part of this study. 4-NP induced genotoxic effects in medaka, which were found to be more sensitive than catfish after exposure to 4-nonylphenol. Graphical abstract.

Many ultraviolet-A (UVA)-induced biochemical and physiological changes are valid as biomarkers using aquatic species for detection of the degree of stress. Changes in the concentration and activities of enzymes, such as glucose-6-phosphate dehyderogenase (G6PDH), lactate dehyderogenase (LDH), DNA damage and lipid peroxidation (LPO), can be used as biomarkers to identify possible environmental contamination in fish. This study aimed to investigate the impact of UVA on the activity of the selected enzymes, DNA damage and LPO during early developmental stages of the African catfish Clarias gariepinus. Embryo hemogenates were used for measurements of G6PDH, LDH, DNA damage and LPO concentrations and activities spectrophotometrically at 37 degrees C. The normal ontogenetic variations in enzyme activities, DNA damage and LPO of the early developmental stages (24-168 h-PFS; hours-post fertilization stage) were studied. There was a significant decrease in the activity of G6PDH till 120 h-PFS. Then after 120 h-PFS, the activity of such enzymes insignificantly increased toward higher stages. The LDH activity was recorded with a pattern of decrease till 96 h-PFS, followed by a significant increase toward 168 h-PFS. The polynomial pattern of variations in DNA damage and LPO was also evident. The patterns of the enzyme activities, corresponding DNA damage and LPO of the early ontogenetic stages under the influence of three different UVA doses (15, 30 and 60 min), were recorded. The pattern of variations in G6PDH activity in UVA-induced groups was similar to that of the control group with variation in the magnitude of such activity. In all treated groups, LDH activity decreased till 96 h-PFS, then increased till 168 h-PFS. Within each of the embryonic stages, the increase in UVA led to a significant increase in DNA damage. A significant increase in lipid peroxidation under UVA doses was recorded. The variability in number and molecular weight of proteins under exposure to UVA was evident, reflecting some of the genetic and transcriptional changes during exposure and development.