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Ammonia is a respiratory gas that is produced during the process of protein deamination. In the unionised form (NH 3 ), it readily crosses biological membranes and is highly toxic to fish. In the present study we examined the effects of unionized ammonia (UIA), on the resting oxygen consumption (MO 2 ), ventilation frequency (f V ), heart rate (HR) and heart rate variability (HRV) in Nile tilapia (Oreochromis niloticus). Fish were either exposed to progressively increasing UIA concentrations, up to 97 µM over a 5 h period, or to a constant UIA level of 7 µM over a 24 h period. For both treatment groups resting MO 2 , HR and f V were recorded as physiological variables. Relative to the control group, the fish groups exposed to the incremental UIA levels did not exhibit significant changes in their MO 2 , HR and f V at UIA concentrations of 4, 10, 35, or 61 µM compared to control fish. Exposure to 97 µM UIA, however, elicited abrupt and significant downregulations (p < 0.05) in all three responses, as MO 2 , HR and fv decreased by 25, 54 and 76 % respectively, compared to control measurements. Heart rate became increasingly irregular with increasing UIA concentrations, and heart rate variability was significantly increased at 61 and 97 µM UIA. Prolonged exposure elicited significant changes at exposure 7 µM UIA. Standard (SMR) and maximum metabolic rate (MMR) were significantly reduced, as was the corresponding f V and HR. It is evident from this study that Nile tilapia is tolerant to short term exposure to UIA up to 61 µM but experience a significant metabolic change under conditions of prolonged UIA exposures even at low concentrations., 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 Author(s). Published by Elsevier B.V. All rights reserved.)

An acute exposure study of mancozeb (MAZ) fungicide was applied on Oreochromis niloticus for 96-h duration. Three hundred fish (20.50 ± 1.60 g) were assigned into six groups (50 fish/ group; 10 fish/replicate) and exposed to different six concentrations (0, 4, 8, 12, 16, and 20 mg L -1 ) of MAZ for 96-h. The Probit analysis program was used to compute the 96-h lethal concentration 50 (96-h LC 50 ) of MAZ. During the exposure duration, the fish's behavior, clinical symptoms, and mortalities were recorded daily. After the exposure period was ended, the hematological, biochemical, immunological, and oxidant/antioxidant parameters were evaluated. The results of this study recorded the 96-h LC 50 of MAZ for O. niloticus to be 11.49 mg L -1 . Acute MAZ exposure badly affected the fish's behavior in the form of increased the breath gasping and swimming activity with aggressive mode. The exposed fish showed excessive body hemorrhages and fin rot. The survival rate of the exposed fish to MAZ was 100, 80, 66, 50, 38, and 30% in 0, 4, 8, 12, 16, and 20 mg L -1 MAZ, respectively. The hematological indices (red blood cell count, hemoglobin, packed cell volume%, and white blood cell count) were significantly decreased by increasing the MAZ exposure concentration (8-20 mg L -1 ). The acetylcholine esterase activity and immune indices (lysozyme, nitric oxide, immunoglobulin M, complement 3) were decreased by MAZ exposure (4-20 mg L -1 ). Acute MAZ exposure induced hepato-renal dysfunction and elevated stress-related parameter (cortisol) by increasing the MAZ concentration. A significant reduction in the antioxidant parameters (total antioxidant activity, catalase, and superoxide dismutase) with increasing the lipid peroxidation marker (malondialdehyde) was noticed by acute MAZ exposure (4 -20 mg L -1 ) in O. niloticus. Based on these outcomes, the MAZ exposure induced toxicity to the fish evident in changes in fish behavior, neurological activity, hepato-renal functioning, and immune-antioxidant responses which suggest physiological disruption., Competing Interests: Declaration of Competing Interest The authors claim that there is no any conflict of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Triphenyltin (TPT), a synthetic chemical, is prevalent in complex salinity areas, including estuaries and coastal regions. However, current studies on the toxicological effects of TPT relevant to the environment at different salinities are limited. In the study, biochemical, histological, and transcriptional analyses of TPT and salinity alone, or in combination, was performed on the Nile tilapia (Oreochromis niloticus) liver. Nile tilapia exhibited weakened antioxidant defenses and liver damage. Transcriptomic analysis revealed that TPT exposure primarily affected lipid metabolism and immunity; salinity exposure alone particularly affected carbohydrate metabolism; combined exposure primarily immune- and metabolic-related signaling pathways. In addition, the single exposure to TPT or salinity induced inflammatory responses by up-regulating the expression of pro-inflammatory cytokines, whereas combined exposure suppressed inflammation by down-regulating pro-inflammatory cytokine levels. These findings are beneficial to understand the negative effects of TPT exposure in Nile tilapia in the broad salinity zones and its potential defense mechanisms., 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 © 2023 Elsevier B.V. All rights reserved.)

This study aimed to examine the side effects of selected neonicotinoids (Acetamiprid, Aceta, and Imidacloprid, Imid) on Oreochromis niloticus juveniles. The acute toxicity, Probit method, revealed an LC 50 of 195.81 and 150.76 ppm for Aceta/96 h and Imid/72 h respectively. The fish were divided into three groups that were exposed, for 21 days (n = 5/replicate), to 1/10 of the LC 50 of either neonicotinoids, however, the third was an unexposed control group. Results of erythrocytic micronucleus (MN), and nuclear abnormalities (NA) showed that Aceta and Imid exposure caused a significant (p < 0.05) increase in MN by ~ 2.2 and ~ 10 folds, respectively relative to control. NAs occurred at the order of kidney-shaped > budding > binucleated in Aceta, however, budding > binucleated > kidney-shaped was noticed in the Imid group. Histopathological changes in gills, liver, and muscles were observed significantly in both exposed groups with more severity in the Imid group. Collectively, Aceta and Imid have potential genotoxicity and histopathological alterations in O. niloticus., (© 2022. The Author(s).)

The aromatase inhibitor letrozole can be found in rivers, effluents, and even drinking water. Studies have demonstrated that letrozole affects various metabolic pathways and may cause reproductive toxicity, especially in fish exposed during development. However, studies on the effect of a low concentration of letrozole at the whole-gonad transcriptomic level in the early stage of fish sexual development have not been investigated. The aim of our study was to explore the potential effects of a low concentration of letrozole on the gonad transcriptome of Nile tilapia at an early stage of sexual development. In this study, 9 dpf (days postfertilization) Nile tilapia were exposed to trace letrozole for 12 days. Letrozole exposure from 9 dpf to 21 dpf persistently altered phenotypic sex development and induced the male-biased sex ratio. The transcriptome results showed that 1173 differentially expressed genes (DEGs) were present in the female control vs 1.5 μg/L letrozole-treated female comparison group and that 1576 DEGs were present in the 1.5 μg/L letrozole-treated female vs male control comparison group. Differentially expressed gene enrichment analysis revealed several crucial pathways, including the drug metabolism-cytochrome P450 pathway, the ErbB-PI3K/Akt/mTOR pathway, and the calcium signalling pathway. Further analysis of these identified DEGs indicated that some key genes correlated with metabolism and epigenetic regulation were significantly affected by letrozole, such as UDP-glucuronosyltransferase (Ugt), glutathione S-transferase omega-1 (Gsto1), lysine-specific demethylase 6bb (Kdm6bb, original name is Kdm6a), jumonji and AT-rich interaction domain containing 2 (Jarid2b, original name is Jarid2), growth arrest and DNA damage inducible gamma (Gadd45g), and chromobox protein 7 (Cbx7). The qRT-PCR validation results for twelve DEGs showed that the Pearson's correlation of the log 10 fold change values between the qPCR and RNA-Seq results was 0.90, indicating the accuracy and reliability of the RNA-Seq results. Our study is the first to report the effect of letrozole on the transcriptome of gonads from fish during early-stage sexual development. These findings will be useful for understanding the toxic effects and molecular mechanisms of letrozole exposure at the early stage of gonad development on the sexual development of aquatic organisms., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Organophosphate pesticides as diazinon disrupt the neuroimmune communication, affecting the innate and adaptive immune response of the exposed organisms. Since the target molecule of diazinon is typically the acetylcholinesterase enzyme (AChE), the existence of a non-neuronal cholinergic system in leukocytes makes them susceptible to alterations by diazinon. Therefore, the aim of this work was to evaluate the activity of AChE, acetylcholine (ACh) concentration, and the expression of nicotinic ACh receptors (nAChR) and muscarinic ACh receptors (mAChR) in spleen mononuclear cells (SMNC) of Nile tilapia (O. niloticus) exposed in vitro to diazoxon, a diazinon metabolite. SMNC were exposed in-vitro to 1 nM, 1 μM, and 10 μM diazoxon for 24 h. The enzyme activity of AChE was then evaluated by spectrophotometry, followed by ACh quantification by ultra-performance liquid chromatography. Finally, mAChR and nAChR expression was evaluated by RT-qPCR. The results indicate that AChE levels are significantly inhibited at 1 and 10 μM diazoxon, while the relative expression of (M3, M4, and M5) mAChR and (β2) nAChR is reduced significantly as compared against SMNC not exposed to diazoxon. However, ACh levels show no significant difference with respect to the control group. The data indicate that diazoxon directly alters elements in the cholinergic system of SMNC by AChE inhibition or indirectly through the interaction with AChR, which is likely related to the immunotoxic properties of diazinon and its metabolites., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Lambda-cyhalothrin is a synthetic pyrethroid that mimics the structure and insecticidal properties of pyrethrin, a natural insecticide derived from chrysanthemums. In fish, it disrupts the nervous system, causing motor paralysis and several other alterations associated with varying levels of mortality. This study aimed to evaluate osmoregulatory responses and histological changes in the gills of Oreochromis niloticus chronically exposed to a sublethal dosage (0.86 μg/L) of lambda-cyhalothrin. The mean serum values for Na 2+ , K + , Cl - , Ca 2+ , pH, lactate, H + , HCO 3, and glucose along to degree of tissue change (DTC) at 24, 96, 168, and 240 h post-exposure (hpe) were evaluated. Lambda-cyhalothrin affected the neuronal motor function at 24 hpe, followed by the increase of the K + , Ca 2+ , H + , and glucose levels in the exposed group, compared to the control group. Lactate and H + levels in the exposed group were higher than those in the control group at 168 and 240 hpe respectively. HCO 3 , and Cl- levels increased at 240 hpe, although there was no change in the pH values. DTC was higher in treated fish than in control fish, but there were no significant differences among time-exposure. The changes detected ranged from hyperemia of the branchial vasculature, eosinophilic granulocytic cell infiltration, mucous cell hyperplasia, and partial fusion of secondary lamellae at 24 hpe to vascular aneurysm formation, and necrosis of the lamellar epithelium at 240 hpe. Thus, a sublethal dosage of lambda-cyhalothrin in the long-term is toxic for Nile tilapia, characterized by hypokalemia, hypercalcemia, hyperglycemia, and respiratory alkalosis, followed by time-dependent histological changes., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The present study investigated the induction of immunological, hormonal and histological changes in the freshwater fish, Pseudetroplus maculatus after sublethal exposure of chlorpyrifos. Fish were exposed to chlorpyrifos at one-tenth (0.661μg/L) and one-fifth (1.32 μg/L) of LC 50 value, for 15 and 30 d, along with the respective control group. Innate and adaptive immune responses of the fish against the toxicant exposure were measured using lysozyme, complement (ACH 50 ) levels, phagocytic, nitroblue tetrazolium (NBT), myeloperoxidase (MPO), anti-protease and hemagglutination activities, and IgM concentration. The results revealed that sublethal exposure of chlorpyrifos caused significant (p < 0.05) reduction in lysozyme, ACH 50 , phagocytic, and anti-protease activities whereas there was significant (p < 0.05) increase in NBT, MPO and hemagglutination levels along with serum IgM concentration. Chlorpyrifos treatment showed significant (p < 0.05) decline in the serum levels of cortisol, thyroid, testosterone and estradiol hormones in duration- and concentration-dependent manner. The major histological lesions noted in liver includes necrosis, vacuolization, hepatocytic and cytoplasmic degeneration, while kidneys showed vacoules, necrosis and rupture in renal tubules and glomerulus, whereas spleen were found with melanomacrophage aggregation and necrosis. Similarly, testis showed remarkable changes like reduction in the number of spermatozoa and disintegrated seminiferous tubules while ovarian lesions include degenerated and empty follicles, few atretic oocytes, reduced size of follicles, and broken theca granulosa. The current findings revealed that the use of chlorpyrifos in domestic and agricultural purposes even at sublethal concentration could affect the non-target organisms including fish, and thereby alter the health status of aquatic ecosystems., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Black jaw tilapia (S. melanotheron) collected from Awba Dam (a watershed recipient of effluents from anthropogenic sources) was analysed for biological responses and trace metal burden with the aim of evaluating sex differences in these responses as a measure of environmental and biota health status. Concentration of heavy metals in fish muscle were analysed and showed values above WHO permissible limits for food. Physiological and biochemical responses (AST, ALT, ALP, total protein, albumin, globulin, BUN, Na + , K + and creatinine) showed apparent sex-related differences. Among antioxidant defence system, mt mRNA and proteins showed higher levels in male S. melanotheron. CAT and GPx activities were significantly higher in males than in female fish, while the corresponding mRNA showed an opposite trend with higher transcripts in females than males. Further, while GST activity was apparently higher in females, GR activity was significantly higher in males, compared to female fish. ZnCu-sod mRNA showed significantly higher transcript levels in males, than females. Overall, the trend in these biological responses showed direct relationship with heavy metal concentrations in fish muscle and sediment. These relationships were revealed using PCA that produced significant groupings between physiological, biochemical and oxidative stress variables and muscle/sediment trace element burden. Specifically, the PCA biplots showed that these biological variables were due to the presence of the heavy metals in the dam. Therefore, the sex differences in the measured cellular adaptations of S. melanotheron in relation to the toxic conditions at the dam may have significant consequences on osmotic balance and cellular processes that regulate biochemical/antioxidant responses towards metabolism, behaviour, growth, reproduction and survival of Awba dam resident fish species. Thus, these responses should be compared to a suitable reference site to discern the extent of effects of the Awba Dam biota for monitoring purposes., Competing Interests: Declaration of competing interest There are no conflicts of interest associated with our paper., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Melano-macrophage centers (MMCs) are nodular clusters of pigmented macrophages, implicated in homeostasis and destruction and recycling of endogenous and exogenous material. They can increase in size and/or frequency under environmental stress resulting in immunohistological biomarkers of water quality. Fluoxetine (FLX), a commonly prescribed antidepressant, can cause neuroendocrine, behavioral and reproductive alterations in teleost fish. In the present study, we analyzed the effects of a 2-week 50 µg/L FLX exposure on MMCs in histological sections of spleen and head-kidney (HK) of the cichlid fish Cichlasoma dimerus. In the spleen, FLX caused an increase in the area and a decrease in the number of MMCs. An increase in the proportion of the HK occupied by MMCs was observed in FLX-exposed fish, due to an increase in their number but not their area. The deposition rate of MMCs varies according to the hemolymphopoietic organ and would be the result of a differential response to FLX on homeostatic functions (elimination of cellular debris, iron processing and immune response).

The toxicity of zinc oxide nanoparticles (ZnO NPs) has been investigated in different animal models. However, concentrations tested in most studies are often much higher than the ones potentially identified in the environment. Therefore, such toxicity limits the application of these studies to evaluate ecotoxicological risks posed by these nanopollutants. Thus, the aim of the current study is to evaluate the impacts of ZnO NPs (at environmentally relevant concentrations - 760 μg/L and 76,000 μg/L, for 72 h) on the behavioral responses of Oreochromis niloticus (Nile tilapia) exposed to it. Results did not evidence harmful effects of NPs on animals' locomotor abilities (evaluated through open-field and light-dark transition tests), or anxiety-predictive behavior. On the other hand, Zn bioaccumulation in the body tissues of the analyzed tilapias was correlated to changes in eating behavior (motivated by ration pellets), as well as to deficits in antipredatory defensive behavior (under individual and collective conditions). Tilapia exposed to ZnO NPs recorded lower avoidance, flight and territorialist behavior rates when they were individually confronted with potential predators (Salminus brasiliensis). However, collectively exposed animals were unable to recognize their predators, as well as to differentiate them from artificial baits ("false predators"). The present study is the first to report biological impacts resulting from the short exposure of fish-group representatives to ZnO NPs. Thus, we believe that it may be relevant to improve the knowledge about ecotoxicological risks posed by these pollutants., (Copyright © 2019. Published by Elsevier B.V.)

This study aimed to investigate the impact of estrogenic endocrine disruptors in adult male Nile Tilapia (Oreochromis niloticus) from the Seven Lakes (Bunot, Calibato, Mohicap, Palakpakin, Pandin, Sampaloc and Yambo) of San Pablo City in Laguna, Philippines. Fish were collected from aquaculture operations in each lake from July to September 2017 and examined for plasma vitellogenin (VTG) levels, hepatosomatic index (HSI) and gonadosomatic index (GSI). In comparison to the reference group (Pandin Lake), fish from Mohicap, Sampaloc and Yambo had higher levels of plasma VTG. HSI was increased in fish from Bunot Lake while it was markedly reduced in fish from Sampaloc Lake. Comparable GSI were obtained in all samples. While most examined fish are in active spermatogenesis, fish from Sampaloc Lake had immature gonads with no spermatozoa, and with minimal to moderate Leydig cell vacuolation and hyperplasia. The results suggest that cultured Nile tilapia from Sampaloc Lake is most adversely affected by endocrine-active compounds. The identification and quantification of these chemicals are recommended in future studies.

Antibiotics and high fat diets are commonly used independently in global aquaculture production for fish health management and to spare the use of costly protein as energy sources, respectively, causing relatively similar metabolic effects and stresses. However, it is unknown whether dietary high fat worsens or attenuates the adverse effects caused by antibiotics in fish. We determined the ability of high fat diet to influence the adverse effects of oxytetracycline on Nile tilapia, Oreochromis niloticus. Thirty Nile tilapia weighing 8.45 ± 0.15 g were fed on medium fat (MF; 70 g/kg) and high fat (HF; 120 g/kg) diets and the same fat levels supplemented with 2.00 g/kg diet of OTC (80 mg/kg body weight/day) hereafter, MFO and HFO for 65 days. The general growth performance, feed efficiency and intestinal health of fish were evaluated. The Nile tilapia fed on HFO diet had significantly lower growth rate, body protein content and feed efficiency compared to those fed on MFO diet. Dietary HFO affected the intestine histomorphology, which decreased dramatically the tight junction proteins of Nile tilapia and induced microbiota dysbiosis compared to MFO diet. The Nile tilapia fed on HFO diet had increased oxidative stress, which stimulated drug detoxification response, caused endoplasmic reticulum stress and apoptosis compared to those fed on MFO diet. The new findings from our study demonstrate that, the adverse effects of antibiotics in fish are different at medium and high fat contents. Feeding fish with high fat diets with antibiotics worsen the adverse effects. This enlightens our understanding on the risks of antibiotics misuse and also suggests that antibiotics should be more strictly limited in aquaculture, in which high fat diets are currently widely used in fish production worldwide., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The occurrence of pharmaceuticals in the aquatic environment has increased considerably in the last decades, causing negative biochemical, physiological, and behavioral effects in aquatic organisms. In this study, we evaluated the effects of methylphenidate (MPH) on the aggressive behavior, dopamine-related gene transcript levels, monoamine levels, and carboxylesterase transcript levels and activity in the brain of male Nile tilapia (Oreochromis niloticus). Carboxylesterase activity was also measured in the liver and gills. Fish were exposed for 5 days to MPH at 20 and 100 ng L -1 . Fish exposed to 100 ng L -1 of MPH showed increased aggressiveness and decreased dopamine (DA) and serotonin (5-HT) levels. No changes were observed in plasma testosterone levels and in the transcript levels of D1 and D2 dopamine receptors, dopamine transporter (DAT), and carboxylesterase 2 (CES2). Exposure to 100 ng L -1 of MPH caused a decrease in the transcript levels of carboxylesterase 3 (CES3) and an increase in tyrosine hydroxylase (TH), while exposure to 20 ng L -1 of MPH increased the transcript levels of D5 dopamine receptor. Carboxylesterase activity was unchanged in the brain and liver and increased in the gills of fish exposed to 20 ng L -1 . These results indicate that MPH at 100 ng L -1 increases aggressiveness in Nile tilapia, possibly due to a decrease in 5-HT levels in the brain and alterations in dopamine levels and dopamine-related genes.

Removal of bio-accumulated pesticides in edible fish is a global problem. In this study, we tested protective capability of a phytochemical pelargonidin-loaded non-toxic, biodegradable poly-lactide-co-glycolide nano-particles (NPG) against toxicity induced by a pesticide cypermethrin (CM) in a fish model (Oreochromis mossambica) in vivo and also in L6 muscle cell line, in vitro. First we assessed potential sustainable release of nanoparticles following oral administration of NPG to fish, their ability to cross sub-cellular membranes in several tissues and efficacy to cross blood-brain-barrier. Next, protective ability of NPG, if any, against CM in fish was evaluated deploying parameters like % cell viability, DNA damage in muscle cells and modulation of anti-oxidative-enzymes like superoxide dismutase, catalase and lipid peroxidase. Modulation of reactive oxygen species generation, nuclear condensation and alteration in stress related protein signalling cascade were assessed in L6 cells. Results revealed that NPG had nano-size range (~10-12 nm) and negative zeta potential (-17 mV). Bioavailability and distribution of NPG could be followed by spectrophotometric absorbance of pelargonidin at 293 nm from 6 h onward till 24 h in all important tissues including the brain. Thus, 0.5 mg/g b.w. NPG could demonstrate protective ability in CM-intoxicated fish muscle cells in respect of % cell viability, DNA damage and stress related enzymes. Similar alterations could also be found in signalling protein cascade in L6 cells in response to treatment of 5 μg/ml NPG against CM-induced toxicity and depletion of overall ROS generation and nuclear condensation. Therefore, NPG could be used as a potential drug in management of pesticide toxicity in cultured edible fish., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Diazinon (DZN) is an organophosphate pesticide characterized by inhibiting the enzyme acetylcholinesterase (AChE) (E.C. 3.1.1.7), affecting the nervous system. There is currently enough evidence proving this pesticide also affects the immune response; however, the immunotoxicity mechanisms through which these substances exerts toxic effects remain unclear. For that reason, this work evaluated the effect of diazinon on the intracellular calcium flux, ERK1/2 phosphorylation (pERK1/2), apoptosis, senescence, and mitochondrial membrane potential (ΔΨm) in spleen mononuclear cells (SMNC) of Nile tilapia, a teleost fish of commercial and ecological relevance. The results obtained indicate that diazinon causes significant damage in all evaluated parameters, which play an essential role in intracytoplasmic signaling of immune cells, suggesting these signal pathways could be related with the immunotoxicity mechanism of these type of pesticides., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This study aimed to assess the water quality of the Perequê River, Porto Belo, Santa Catarina, Brazil, through a biomarker approach in the native fish species Geophagus brasiliensis, and the sediment chemical quantification of the herbicides glyphosate and bentazone used in irrigated rice plantations. This river is used for the public water supply of two municipalities. The first sampling (S1) was in November 2016, in the spring season and the second (S2), in March 2017, in the fall season. In each sampling, two points of the river were analyzed, one upstream of the accumulation dam and the water catchment point for water supply of the Porto Belo WTS (P1), and another downstream (P2) with water, sediment, and fish sampling. Biotransformation, oxidative stress, histopathological and genotoxic biomarkers were analyzed in different tissues. The presence of glyphosate was detected in the sediment (11.7 μg·kg -1 ) from the upstream point of the water catchment site (P1) in spring. The lower activity of the antioxidant enzyme superoxide dismutase (SOD), as well as the increased damage to renal DNA and hepatic tissue, coincided with the lower muscular and cerebral acetylcholinesterase activities (AChE) at P1, in relation to P2 in the spring season, with a lower rainfall index (81.8 mm 3 ). A seasonal variation was also observed between the spring and fall seasons, in fish responses to biomarkers. Reduction of muscle AChE activity and biotransformation enzymes ethoxyresorufin-O-deethylase and glutathione S-transferase and antioxidant enzymes such as, SOD and glutathione peroxidase, as well as increased brain DNA damage, coincided with the highest number of tissue lesions in the liver and gills in the spring, regardless of the sampling point. The results suggested that the Perequê River is contaminated by xenobiotics and probably herbicides from irrigated rice plantations, indicating damages to the biota and a potential public health risk., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The correlation between endocrine active contaminants in the environment and alterations in reproductive development of Sarotherodon melanotheron from Lagos lagoon has been investigated. Sediment and a total of 155 fish (74 males and 81 females) were collected between November 2014-March 2015 from selected contaminated sites (Ikorodu, Oworonshoki, Makoko and Idumota) and a putative control site (Igbore) along the lagoon. Sediment contaminant analysis revealed, significantly higher concentration of lindane, dieldrin, 4-iso-nonylphenol, 4-t-octylphenol and monobutyltin cation at the contaminated sites. Examination of gross morphological and histological changes of fish gonads showed a 27.4% prevalence of intersex in the sampled fish, of which 78% were males (testes-ova) and 22% were females (ovo-testis). Quantitative PCR (qPCR) of liver transcripts revealed the presence of vitellogenin (vtg) levels in male fish from contaminated sites. Zona radiata proteins (zrp) mRNA levels were significantly higher in females, compared to male fish. In general, significantly lower vtg and zrp transcripts levels were recorded at Igbore (control site), compared with contaminated sites. Principal component analysis (PCA) showed site and sex relationship in biological responses and contaminants, including trace metals, demonstrating that measured endocrine responses in fish were associated with contaminant burden in sediment. In addition, positive relationships were observed in male fish from Idumota, Oworonshoki and Ikorodu with vtg and dieldrin/4-iso-nonyphenol, with higher levels in male fish, compared to females. Further, contaminants from the Makoko, Oworonshoki and Ikorodu sites were positively associated with higher GSI and zrp in females. More importantly, the severity of intersex and changes in vtg transcripts imply a progressive feminization of male fish with concomitant alteration in the reproductive health of fish inhabiting the Lagos lagoon., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is the main active ingredient in an emerging water environment antifoulant, the toxicity and environmental impacts of which need to be further investigated. Thus, this study examined the toxicity of DCOIT on Nile tilapia (Oreochromis niloticus), including its effects on behavior, respiration and energy metabolism as well as the role of endoplasmic reticulum stress (ER stress) in mediating its toxicity and metabolic changes. The changes in fish behavior, respiration, neuronal signal transmission, energy metabolism, ER stress, and liver histology were examined via acute (4 days) and chronic (28 days) exposures to 0, 3, 15, 30 μg/L DCOIT in vivo. Additionally, ER stress levels were measured in 24-h periods of hepatocyte exposure to 0, 3, 15, 30 and 300 μg/L DCOIT in vitro. The hyper-locomotor activities decreased, but the respiration rate increased after a 4-day acute exposure period, indicating that DCOIT exposure altered fish energy metabolism. After acute exposure at a low DCOIT concentration, the activation of ER stress induced triglyceride accumulation in the liver. After chronic exposure for 28 days, the prolonged ER stress induced a series of pathological cellular changes. At the cellular level, exposure to a high DCOIT concentration induced ER stress in the hepatocytes. In addition, as a neurotoxin, DCOIT has the potential to disrupt the neurotransmission of the cholinergic system, resulting in motor behavior disruption. This study demonstrates that DCOIT plays a role in time- and concentration-dependent toxicity and that changes in lipid metabolism are directly related to endoplasmic reticulum function after exposure to an antifouling agent. This work advances the understanding of the toxic mechanism of DCOIT, which is necessary for its evaluation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Manganese and iron were found at high concentrations (3.61 mg/L and 19.8 mg/L, respectively) in the water of the Rio Doce after the dams of Fundão and Santarém broke in Mariana/MG (Brazil). These same metals were found in fish and crustacean muscle (15 mg/kg and 8 mg/kg wet weight, respectively) in the specimens collected near the Rio Doce's outfall. Due to the variation in Mn concentration found in the lower Rio Doce, this study aimed to determine the effects of Mn in Oreochromis niloticus, at the concentrations allowed by CONAMA, and in concentrations found in the Rio Doce after the dams broke. The animals were exposed to the following dissolved concentrations: control group (0.0 mg/L), 0.2; 1.5 and 2.9 mg/L manganese for 96 h. In addition, a positive control was conducted, injecting intraperitoneally with cyclophosphamide (at 25 mg/kg). These exposures caused significant erythrocyte micronucleus formation in the organisms exposed to the highest concentration, as well a significant increase in the DNA damage index of erythrocytes from organisms exposed to 1.5 mg/L and 2.9 mg/L treatments. The glutathione S-transferase enzyme activity also showed a significant increase in the liver of the organisms exposed to 2.9 mg/L. However, catalase activity increased significantly in the gills of the animals exposed to all concentrations of manganese that were tested. Manganese bioconcentrated in greater quantities in the liver than the gills. Thus, manganese causes significant damage to genetic material, generates nuclear abnormalities, activates the body's detoxification system and can accumulate in animal tissue.

Copper oxide nanoparticles (nCuO) are widely used in boat antifouling paints and are released into the environment, potentially inducing toxicity to aquatic organisms. The present study aimed to understand the effects of nCuO and dissolved copper (Cu) on two ornamental Amazon fish species: dwarf cichlid (Apistogramma agassizii) and cardinal tetra (Paracheirodon axelrodi). Fish were exposed to 50% of the LC 50 for nCuO (dwarf cichlid 58.31μgL -1 and cardinal tetra 69.6μgL -1 ) and Cu (dwarf cichlid 20μgL -1 and cardinal tetra 22.9μgL -1 ) for 24, 48, 72 and 96h. Following exposure, aerobic metabolic rate (ṀO 2 ), gill osmoregulatory physiology and mitochondrial function, oxidative stress markers, and morphological damage were evaluated. Our results revealed species specificity in metabolic stress responses. An increase of ṀO 2 was noted in cardinal tetra exposed to Cu, but not nCuO, whereas ṀO 2 in dwarf cichlid showed little change with either treatment. In contrast, mitochondria from dwarf cichlid exhibited increased proton leak and a resulting decrease in respiratory control ratios in response to nCuO and Cu exposure. This uncoupling was directly related to an increase in reactive oxygen species (ROS) levels. Our findings reveal different metabolic responses between these two species in response to nCuO and Cu, which are probably caused by the differences between species natural histories, indicating that different mechanisms of toxic action of the contaminants are associated to differential osmoregulatory strategies among species., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Tebuthiuron is a phenylurea herbicide widely used in agriculture that can reach the aquatic environments, possibly posing negative effects to the aquatic biota. Phenylurea herbicides, such as diuron, are known to cause estrogenic and anti-androgenic effects in fish, but no such effects were yet reported for tebuthiuron exposure. Thus, the aim of this study was to evaluate if tebuthiuron, at environmentally relevant concentrations (100 and 200ng/L) and after 25days of exposure have estrogenic and/or anti-androgenic effects on male of Nile tilapia (Oreochromis niloticus), through the evaluation of plasmatic testosterone (T) and estradiol (E 2 ) levels, brain aromatase (CYP19) levels (western-blot), and by evaluating the histology of the testicles. When compared to the control group, plasmatic T levels decreased about 76% in the animals exposed to 200ng/L of tebuthiuron, while E 2 levels increased about 94%, which could be related to a significant increase (77%) in CYP19A1 levels, an enzyme that catalyzes the conversion of androgens into estrogens. Histological analyses of the testicles also demonstrated that tebuthiuron at both tested concentrations caused a decrease in the diameter of the seminiferous tubules and in the diameter of the lumen. Therefore, the gonadosomatic index (GSI) was reduced by 36% % in the animals exposed 200ng/L to tebuthiuron. Indeed, the relative frequency of spermatocytes and spermatids increased respectively 73% (200ng/L) and 61% (100ng/L) in the tebuthiuron exposed animals, possibly due to the impairment of sperm release into the lumen, that was decreased 93% (200ng/L) in the treated animals compared to the control. These results confirm that tebuthiuron causes estrogenic and anti-androgenic effects in Nile tilapias at environmentally relevant concentrations., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The present study evaluated the water quality of a polluted pond through the analysis of in vitro mucociliary transport, hematological parameters, and biomarkers of cyto-genotoxicity in the Nile tilapia (Oreochromis niloticus). Blood and mucus samples were collected from ten specimens from the polluted pond and from ten specimens from a control area. The fish were anesthetized with 3% benzocaine, mucus was collected directly from the gills, and blood was drawn from the caudal artery. Blood smears were stained using the May-Grünwald Giemsa process for the differential leukocyte counts and to determine the frequency of leukocytes, thrombocytes, erythroblasts, micronuclei, and nuclear abnormalities. The results revealed low transportability in vitro, a high percentage of monocytes and eosinophils, and increased frequency of leukocytes and nuclear abnormalities in fish from the polluted pond. However, the frequency of thrombocytes and erythroblasts and the percentage of lymphocytes and neutrophils were significantly lower. It is possible to conclude that changes in fish are due to poor water quality and that these non-destructive biomarkers can be used for the biomonitoring of aquatic environments vulnerable to contamination.

Accumulation of copper oxide nanoparticles (CuO NPs) in gill, liver and muscle tissues of Oreochromis niloticus and its effects on superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities in gill and liver tissues were studied after exposing the fish to 20 µg/L Cu over 15 days. Copper levels and enzyme activities in tissues were determined using spectrophotometric (ICP-AES and UV) techniques respectively. No mortality was observed during the experiments. Copper levels increased in gill and liver tissues of O. niloticus compared to control when exposed to CuO NPs whereas exposure to metal had no effect on muscle level at the end of the exposure period. Highest accumulation of copper was observed in liver while no accumulation was detected in muscle tissue. SOD, CAT activities decreased and GPx activity increased in gill and liver tissues when exposed to CuO NPs.

The accumulation, elimination and effect of heavy metals on plasma cortisol levels in Oreochromis sp. were studied in the exposure and recovery phases. In the exposure phase, the mean rate of accumulation in the tissues was in the order gill > liver > muscle for Pb exposure and muscle > liver > gill for As exposure. In the recovery phase, the order of elimination in the tissues was gill > liver > muscle for Pb and liver > gill > muscle for As. The amount of cortisol secreted by the Oreochromis sp. after Pb or As treatment was lower compared to Oreochromis sp. in the control group during the exposure phase. In the recovery phase, plasma cortisol levels in Oreochromis sp. increased in all Pb treatment groups while it continuously decreased in all As treatment groups. A fish affected by As has obvious difficulty recovering from the stress response. It was concluded that exposure to the tested concentrations of Pb and As over 20 days could be a potent endocrine disruptor, which may lead to adverse impacts on the health of the Oreochromis sp.

Individual variation in sub-lethal sensitivity to the organophosphate pesticide trichlorfon was investigated in Nile tilapia, using critical swimming speed (U crit ) as an indicator. Tilapia exposed for 96h to 500μgl -1 trichlorfon at 26°C (Tcfn group, n=27) showed a significant decline in mean U crit , compared to their own control (pre-exposure) performance in clean water (-14.5±2.3%, mean±SEM), but also compared to a Sham group (n=10) maintained for 96h in clean water. Individuals varied in their relative sensitivity to the pesticide, with the decline in U crit after exposure varying from 1 to 41%. The U crit of the Tcfn group did not recover completely after 96h in clean water, remaining 9.4±3.2% below their own control performance. The decline in performance was associated with a significant increase in net cost of aerobic swimming, of +28.4±6.5% at a sustained speed of 2bodylengthss -1 , which translated into a significant decline in swimming efficiency (E swim ) of -17.6±4.0% at that speed. Within the Tcfn group, individual E swim was a strong positive determinant of individual U crit across all trials, and a strong negative determinant of individual% decline in U crit after pesticide exposure (P<0.001, linear mixed effect models). Trichlorfon had no effects on standard metabolic rate or active metabolic rate (AMR) but, nonetheless, individual U crit in all trials, and% decline in U crit after exposure, were strongly associated with individual AMR (positively and negatively, respectively, P<0.001). Individual U crit under control conditions was also a strong positive determinant of U crit after trichlorfon exposure (P<0.001), but not of the% decline in U crit performance. In conclusion, the OP pesticide impaired U crit performance by reducing E swim but individual tilapia varied widely in their relative sensitivity. Intrinsic individual physiology determined effects of the pesticide on performance and, in particular, good swimmers remained better swimmers after exposure., (Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.)

Pharmaceutical drugs and their metabolites are detected in aquatic ecosystems and have been reported to cause ecotoxicological consequences to resident aquatic organisms. The study investigated the effects of acute and long-term exposure to verapamil on activities of acetylcholinesterase and antioxidant enzymes as well as mRNA expression of stress-related genes in brain and muscle tissues of Nile tilapia, Oreochromis niloticus. The 96h LC 50 of verapamil to O. niloticus was 2.29mgL -1 . Exposure to sub-lethal concentrations of verapamil (0.14, 0.29 and 0.57mgL -1 ) for period of 15, 30, 45 and 60days, led to inhibition of acetylcholinesterase activities in the brain and muscle of the fish. The activities of the oxidative enzymes such as the catalase, superoxide dismutase and glutathione peroxidase were also inhibited in both the tissues while there was an increase in the activities of glutathione-S-transferase and reduced glutathione in the muscle after 15 days at 0.29mgL -1 . Lipid peroxidation and carbonyl protein showed elevated level, indicating a positive correlation with both time and concentration. The activities of energy-related biomarker (Na + -K + -ATPase) in both the tissues were significantly inhibited (p<0.05) compared with the control. Transcription of catalase (cat), superoxide dismutase (sod) and heat shock proteins 70 (hsp70) were up-regulated in both the tissues after the study period. Prolonged exposure to sub-lethal verapamil can result in oxidative stress, up-regulation of stress-related genes and neurotoxicity in O. niloticus., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Among the wide variety of pharmaceuticals released into the environment, Fluoxetine (FLX), a selective serotonin reuptake inhibitor, is one of the most prescribed for the treatment of major depression. It inhibits serotonin (5-HT) reuptake at the presinaptic membrane, increasing serotonergic activity. In vertebrates, including fish, the serotonergic system is closely related to the Hypothalamic Pituitary Gonadal (HPG) axis which regulates reproduction. As FLX can act as an endocrine disrupting compound (EDC) by affecting several reproductive parameters in fish, the aim of this study was to provide an integral assessment of the potential effect of FLX on the reproductive axis of the Neotropical freshwater fish Cichlasoma dimerus. Adult fish were intraperitoneally injected with 2 μg g -1 FLX or saline every third day for 15 days. No significant differences were found on serotonergic turnover (5-HIAA/5-HT ratio). Pituitary βLH content in FLX injected females was significantly higher than control females; no significant differences were seen for βFSH content. Sex steroids remained unaltered, both in males and females fish, after FLX treatment. No plasma vitellogenin was induced in treated males. Some alterations were seen in testes of FLX injected males, such as the presence of foam cells and an acidophilic PAS positive, Alcian-Blue negative secretion in the lobular lumen. Although there is no clear consensus about the effect of this drug on reproductive physiology, these results indicate that FLX is acting as a mild EDC in adults of C. dimerus., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Tilapia were exposed to sublethal methomyl concentrations of 0, 0.2, 2, 20 or 200 μg/L for 30 days, and then transferred to methomyl-free water for 18 days. The sexual steroid hormones 17β-estradiol (E2), testosterone (T), and 11-ketotestosterone (11-KT) in tilapia testes were examined at 0, 6, 12, 18, 24 and 30 days after methomyl exposure, and at 18 days after fish were transferred to methomyl-free water. There were no significant changes in the hormone parameters in testes of tilapia exposed to low concentration 0.2 and 2 μg/L methomyl compared with the controls. However, high concentration 20 and 200 μg/L methomyl had the potential to disrupt the endocrine system of male tilapia, as shown by an increase in E 2 and a decrease in T and 11-KT in the testes. Thus, it would appear that the 2 μg/L methomyl might be considered the no-observed-adverse-effect level. Recovery data showed that the effects produced by the lower concentration of 20 μg/L were reversible but the effects were not reversible at the higher concentration of 200 μg/L.

The relationship between condition factor (CF), peroxisome proliferator-activated receptors (PPARs), phase 1 biotransformation (CYP1A isoforms) and contaminant burden has been studied in Sarotherodon melanotheron from a contaminated tropical freshwater dam (Awba Dam) and compared to a reference site (Modete Dam) in Southwest, Nigeria. A total of 89 fish (57 males and 32 females) was collected from Awba Dam and 95 fish (48 males and 47 females) from the reference site. In general, fish sampled from Awba Dam were bigger than reference site. Sediment samples were also collected from both sites for contaminant analysis. Expression of ppar and cyp1 isoforms was analyzed using validated real-time PCR, while CYP1A and PPAR protein levels were analyzed using immunochemical method with specific antibodies. CYP-mediated catalytic responses (EROD, MROD and BROD) were performed by biochemical methods. We observed significant increases in ppar and cyp1 isoforms mRNA in both male and female fish from Awba Dam, compared to the reference site. Catalytic activities of EROD, MROD and BROD paralleled cyp1 transcript levels. Sex-related differences in PPAR and CYP1A protein levels were also observed, showing higher CYP1A proteins in males, compared with females, and higher PPAR proteins in females compared with males. Principal component analysis (PCA) biplot showed positive relationships between biological responses (ppar isoforms), condition factor (CF) and sediment PCBs, PAHs, OCPs and heavy metal concentrations. The present study shows that S. melanotheron inhabiting Awba Dam are severely affected by different classes of environmental contaminants that target metabolic processes (PPAR) and biotransformation pathways (CYP1A) in male and female fish, compared to a reference site. Interestingly, fish from Awba Dam were exhibiting good growth (evidence by high CF values) that paralleled increases in the transcriptional activation of ppar and cyp1 isoforms, despite the high contaminant burdens, suggesting a possible contaminant-induced obesogenic effects., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The present study was designed to assess the possible causes of the mass mortalities of Nile Tilapia Oreochromis niloticus at El-Behera Governorate, Egypt, in relationship to environmental and microbiotic factors. Water samples were collected from fish farms at different locations and from Lake Edku to analyze water temperature, water pH, salinity, biological oxygen demand, dissolved oxygen, total ammonia nitrogen, and un-ionized ammonia. A number of moribund and freshly dead fish were sampled and submitted to our laboratory for microbiological, molecular, and histopathological examination. Water analysis of the fish farms revealed noticeable increases in the previously mentioned physicochemical parameters. Clinical examinations of moribund fish showed severe gill rot and massive external and internal hemorrhages. Ordinary and molecular laboratory findings confirmed the presence of Branchiomyces sp. in gill tissue and mixed bacterial fish pathogens (Streptococcus agalactiae, Vibrio alginolyticus, V. parahaemolyticus, Pseudomonas anguilliseptica, and P. aeruginosa) in visceral organs. The histopathological and transmission electron microscopic examinations revealed severe necrosis of gill filaments and blockage of branchial blood vessels and lamellar capillaries with Branchiomyces sp. hyphae and spores mixed with different shapes of bacteria. Severe inflammations were detected in liver, kidney, heart, and brain tissues. Ultimately, we can conclude that the syndrome of mass fish kills in this area is a consequence of ecological damage to the aquatic environment, which is mainly related to natural and anthropogenic factors, as well as to the presence of infectious agents. Received September 30, 2015; accepted April 12, 2016.

The present study aims to investigate the effects of both garlic and curcumin through evaluating their therapeutic properties as antioxidants on liver and kidney functions, hepatic antioxidants and GPx gene expression against aflatoxicosis of O. niloticus. In total, 180 of tilapia were divided into ten groups; T1 represented the negative control fed on a basal diet, and T2 was injected with a single intraperitoneal (i.p.) dose of AFB1 (6 mg/kg b.w.). Fish in T3-T6 were fed on a basal diet supplemented with both garlic (T3 and T4) and curcumin (T5 and T6) at the two concentrations of 10 and 20 g/kg diet, respectively. Fish in T7-T10 groups were injected with AFB1 and fed on the garlic (T7 and T8) and curcumin (T9 and T10) dietaries. The results showed that AFB1 has significant potency for increasing the activity of plasma AST, ALT, creatinine and uric acid values, and hepatic MDA as well as for reducing the concentrations of plasma TP, AL, GL and hepatic activity of TAC, while AFB1 led to up-regulated GPx gene expression when compared to the control (T1). These harmful effects of AFB1 were alleviated due to the garlic and curcumin dietaries in some studied parameters. Garlic reflected the highest induction of gene expression (T7); however, curcumin showed significant down-regulated (T9). These results concluded that the effects of garlic were better than curcumin at the two concentrations and the low concentration of them is more beneficial than the high concentration when it used against AFB1 in O. niloticus.

Arsenic (As) is one of the most relevant environmental global single substance toxicants that have long been regarded as a carcinogenic and genotoxic potential. In this respect, we evaluated the cytogenetic effect of arsenic exposure in Nile tilapia (Oreochromis niloticus), in terms of erythrocyte alteration, apoptosis, and induction of micronuclei. Spirulina platensis (SP) is a filamentous cyanobacterium microalgae with potent dietary phytoantioxidant, anti-inflammatory, and anti-cancerous properties supplementation. The protective role of Spirulina as supplementary feeds was studied in Nile tilapia (O. niloticus) against arsenic-induced cytogenotoxicity. Four groups were assigned as control group (no SP or As), As group (exposed to water-born As in the form of NaAsO2 at 7 ppm), SP1 (SP at 7.5% + As at the same level of exposure), and SP2 (SP at 10% + As at the same level of exposure). As-treated group had a significant increase in all cytogenetic analyses including erythrocyte alteration, apoptosis, and induction of micronuclei after 2 weeks with continuous increase in response after 3 weeks. The combined treatment of Spirulina at two different concentrations of 7.5 and 10% had significantly declined the induction of erythrocyte alteration, apoptosis, and micronuclei formation induced by arsenic intoxication.

The contamination of aquatic ecosystems with copper (Cu) poses a serious threat to aquatic organisms. Although the histopathological changes caused by Cu in fish gills are well documented, knowledge about the impact of this metal in gill specific cell types, such as neuroendocrine cells (NECs) and eosinophilic granule cells (EGCs), is still limited. In the present work, Nile tilapia (Oreochromis niloticus) were exposed for 21 days to nominal concentrations of Cu (40 and 400 µg L(-1)). Stereological methods were used to estimate the volumetric density of both NECs and EGCs in fish gill filament after 3, 7, 14, and 21 days of exposure. The results showed that Cu significantly increased the relative volume of NECs, whereas the relative volume of EGCs decreased. NECs were more affected by Cu in the first 7 days of exposure, during which a greater increase in their relative volume was observed. The Cu exposure induced a progressive decrease in the relative volume of EGCs, which reached statistical significance after 14 days of exposure. An exception was observed in subepithelial EGCs with a slight increase in their relative volume after 3 days of exposure. Our findings confirm that Cu can modulate both neuroendocrine and immune systems and becomes immunotoxic after a prolonged exposure.

Endosulfan (ES) is an organochlorine pesticide widely used in agriculture despite its high toxicity towards non-target organisms such as fish. It has been demonstrated that ES can cause negative effects on aquatic animals, including disruption of hormonal systems. However, the alterations produced by this pesticide on the reproductive axis of fish prior to sexual maturity, as well as possible modes of action have hardly been studied. This study aimed at assessing the effect of waterborne exposure to the pesticide ES on the reproductive axis during sexual differentiation of juveniles of the South American freshwater cichlid fish Cichlasoma dimerus. No mortality was observed due to ES subchronic exposure (90 days post-fertilization). Exposure to ES did not affect body weight nor morphometric parameters, indicating that larvae nutritional state was not affected. Timing of sexual differentiation, gonadal morphology and sex ratio were likewise not altered by ES. However, ES acted as an endocrine disrupting chemical in this species as the morphometry of gonadotropin-releasing hormones (GnRH) producing cells was altered. Exposure to ES altered nuclear area, cell area and nucleus/cytoplasm ratio of GnRH II neurons, and cell and nuclear area and diameter of GnRH III neurons. Interestingly, in our previous study, exposure before sex differentiation (30 day exposure) caused no alteration to GnRH II and III, and did alter GnRH I and FSH cells. These alterations could lead to changes in circulating hormone levels, especially when fish are exposed for prolonged periods, ultimately impairing reproductive fitness. C. dimerus juveniles can be an interesting biological model to perform toxicological studies with the intent to assess early disruption endpoints in the reproductive axis during development., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The interactions of carbon nanotubes with pesticides, such as carbofuran, classical contaminants (e.g., pesticides, polyaromatic hydrocarbons, heavy metals, and dyes) and emerging contaminants, including endocrine disruptors, are critical components of the environmental risks of this important class of carbon-based nanomaterials. In this work, we studied the modulation of acute carbofuran toxicity to the freshwater fish Nile tilapia (Oreochromis niloticus) by nitric acid treated multiwalled carbon nanotubes, termed HNO3-MWCNT. Nitric acid oxidation is a common chemical method employed for the purification, functionalisation and aqueous dispersion of carbon nanotubes. HNO3-MWCNT were not toxic to Nile tilapia at concentrations ranging from 0.1 to 3.0 mg/L for exposure times of up to 96 h. After 24, 48, 72 and 96 h, the LC50 values of carbofuran were 4.0, 3.2, 3.0 and 2.4 mg/mL, respectively. To evaluate the influence of carbofuran-nanotube interactions on ecotoxicity, we exposed the Nile tilapia to different concentrations of carbofuran mixed together with a non-toxic concentration of HNO3-MWCNT (1.0 mg/L). After 24, 48, 72, and 96 h of exposure, the LC50 values of carbofuran plus nanotubes were 3.7, 1.6, 0.7 and 0.5 mg/L, respectively. These results demonstrate that HNO3-MWCNT potentiate the acute toxicity of carbofuran, leading to a more than five-fold increase in the LC50 values. Furthermore, the exposure of Nile tilapia to carbofuran plus nanotubes led to decreases in both oxygen consumption and swimming capacity compared to the control. These findings indicate that carbon nanotubes could act as pesticide carriers affecting fish survival, metabolism and behaviour., (Copyright © 2014 Elsevier Inc. All rights reserved.)

N-acetyl-β-D-glucosaminidase (EC 3.2.1.52, NAGase), hydrolyzes dimers or trimers of N-acetyl-β-D-glucosamine (NAG) into monomers and is shown to be important for the reproduction of male animals. NAGase is purified from the spermary of Nile tilapia, and its enzyme activity can be strongly inhibited by mercuric chloride (HgCl2). In this paper, we determined the kinetics of HgCl2-mediated inhibition of NAGase, and our results showed that it was irreversible inhibition with an IC50 value at 2.70±0.02 μM. Moreover, Hg(2+) reduced the thermal and pH stability of the enzyme. We determined the inhibition kinetics of Hg(2+) by using the kinetic method of substrate reaction. With this inhibition model, the microscopic rate constants for the reaction of Hg(2+) with free enzyme (k1) and the enzyme-substrate complex ( [Formula: see text] ) were determined to be 4.42×10(-4) mM(-1) s(-1) and 7.06×10(-5) mM(-1) s(-1), respectively, indicating that the presence of substrate can protect NAGase from Hg(2+) inhibition., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Tilapias (Oreochromis niloticus) were exposed to copper or chromium in soft water (SW) (~80 mg CaCO3/L, conductivity 1.77 mS/cm) or hard water (HW) (~320 mg CaCO3/L, conductivity 5.80 mS/cm) using 2 exposure protocols (20 μM for 48 h and 10 μM for 144 h). Following the exposures, antioxidant enzyme activities [superoxide dismutase (SOD); catalase (CAT); glutathione peroxidase; glutathione reductase; and glutathione S-transferase (GST)] and glutathione (GSH) levels were measured in the liver of fish. SOD and CAT activities of control fish kept in SW were significantly lower than control fish kept in HW. However, the other antioxidant indices (glutathione metabolism) of both control fish were unaffected from water hardness. Acute metal exposures did not alter the glutathione metabolism, whereas SOD activity in SW and CAT activity in both waters changed significantly. In subchronic duration, Cu exposure caused significant decreases in measured parameters, except for GST activity and GSH level. Similarly, GST activity and GSH level were unaffected from Cr exposure. This study showed that SOD and CAT were the most sensitive antioxidant indices, and that glutathione metabolism, in general, was not altered following metal exposures in different waters.

Cylindrospermopsin (CYN) is a cytotoxic polyketide-derived alkaloid produced by several freshwater cyanobacterial species. It is now considered the second most studied cyanotoxin worldwide. Among the toxic mechanisms suggested for CYN pathogenicity are inhibition of protein and glutathione synthesis, genotoxicity by DNA fragmentation, and oxidative stress. The study of depuration of cyanobacterial toxins by aquatic organisms, particularly by fish, is important for fish economy and public health, but in the case of CYN is practically nonexistent. In this work, we investigated the efficiency of two distinct depuration periods, 3 or 7d, in a clean environment, as a mean of restoring the levels of several oxidative stress biomarkers in tilapia (Oreochromis niloticus) subchronically exposed to CYN by immersion in an Aphanizomenon ovalisporum culture (by adding 10 μg CYN/L every two days during 14 d). Lipid peroxidation (LPO) and DNA oxidation returned to normal values after 7d of depuration, whereas the time needed for restoring of the oxidatively damaged proteins was longer. Superoxide dismutase (SOD) and gamma-glutamyl-cysteine-synthetase (γ-GCS) activities recovered after just 3d of depuration, while catalase (CAT) activity needed up to 7d to return to control values. Ratio of reduced glutathione to oxidized glutathione (GSH/GSSG) returned to control levels after 7d of depuration in both organs. These results validate the depuration process as a very effective practice for detoxification in fish contaminated with these toxins., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Hepatic antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) of Nile tilapia in response to pesticide methomyl and recovery pattern were researched by exposing tilapia to sub-lethal methomyl concentrations of 0, 0.2, 2, 20 and 200 μg/L for 30 days, and then transferred to methomyl-free water for 18 days. Hepatic SOD and CAT were measured at 10 min (day 0), 6, 12, 18, 24 and 30 days after starting the experiment and at 18 days after transferring to methomyl-free water. The results showed hepatic SOD and CAT activities in 2, 20 and 200 μg/L groups were affected significantly, however, that in 0.2 μg/L group didn't change significantly compared to control during 30-day exposure period. Thus it would appear the 0.2 μg/L methomyl might be considered the no observed adverse effect level. Recovery data showed that, for SOD, the effects produced by lower concentration of methomyl 2 μg/L were reversible but not at concentrations higher than 20 μg/L, however, for CAT, the effects produced by all the concentrations were reversible.

The chronic effect of methomyl on the antioxidant system in tilapia (Oreochromis niloticus) was investigated. Fish were exposed to sub-lethal concentrations of 0.2, 2, 20 and 200μgL(-1) for 30 days, and then transferred to methomyl-free water for 18 days. Hepatic antioxidant parameters, including Glutathione-S-transferase (GST), Glutathione peroxidase (GPx), Glutathione reductase (GR), Reduced glutathione (GSH) and oxidized glutathione (GSSG), were measured at 10min (day 0), 6, 12, 18, 24 and 30 days after starting the experiment and at 18 days after transferring to methomyl-free water. There were no significant changes in enzymatic activity and content of antioxidants in liver of tilapia exposed to 0.2μgL(-1) methomyl compared to controls. However, the results showed significant increases in activities of GST, GR, GPx and levels of GSSG accompanied by a decrease in GSH levels following methomyl exposure in tilapia to 2, 20 or 200μgL(-1) over the 30-day exposure period and the highest induction rates in GST, GR, GPx and GSSG were 150.87%, 163.21%, 189.76%, and 179.56% of the control respectively, and the highest inhibition rate in GSH was 50.67% of the control, suggesting the presence of oxidative stress. Thus it would appear that the 0.2μgL(-1) methomyl might be considered as the no observed adverse effect level (NOAEL). Recovery data showed that the effects produced by lower concentration of methomyl 20μgL(-1) were reversible but not at the higher 200μgL(-1) concentration., (© 2013 Published by Elsevier Inc.)

Lake Al-Asfar (Al-Hassa, Saudi Arabia) is under threat from contaminants released through human activities such as agriculture and urban and industrial developments. In the present study, histopathologic and ultrastructural changes in liver of tilapia Oreochromis niloticus were analyzed to monitor the possible impact of pollution in Al-Asfar estuary. Heavy metals such as Ni, Fe, Zn, Co, Ba, Pb, and Cd were predominant in the lake water and far exceeded the international permissible limits. In fish samples, high prevalences of preneoplastic changes (50 %) and one case of cholangiocarcinoma were revealed in liver tissues. Cytological damage in fish hepatocytes included glycogen exhaustion, deformation of nuclear envelope, heterochromatin condensation, mitochondrial degeneration, vesiculation of rough endoplasmic reticulum, augmentation of smooth endoplasmic reticulum, and lysosomal proliferation. In conclusion, the observed biomarker responses were potential indicators of health impairment or disease in field fish populations, although there was no direct proof of a simple cause-effect relationship. This is the first biological effect assessment in Lake Al-Asfar using tilapia as suitable target species.

Freshwater organisms are highly sensitive to increases in salinity because they causes serious osmoregulation problems. Salinity of inland waters can be increased as a result of anthropogenic activities. In this study, freshwater fish Oreochromis niloticus were exposed individually to increased salinities (0, 2, and 8 ppt) alone and salinity+metal [1 μg/mL chromium (Cr) or lead (Pb) exposure at 2 and 8 ppt] exposures for different time periods (1, 7, and 14 days) to investigate the response of Na(+)/K(+)-ATPase and Mg(2+)-ATPase in the osmoregulatory tissues (gill and intestine). Results showed that enzyme activity varied depending on salinity, tissue, metal, and exposure duration. Metal levels in controls and salinity-exposed groups were lower than the detection limit, although significant Cr and Pb accumulation occurred in the salinity+metal combination groups. In salinity-exposed groups, there were increasing trends in the enzyme activity, whereas there were decreasing trends in the metal+salinity groups. Gill ATPases were more affected by the exposure conditions compared with intestine ATPases. Results showed that salinity+metal exposure both played significant roles on ATPase activities in the osmoregulatory tissues, although the alterations in the activity were mostly insignificant supporting compensation mechanisms. Results also suggest that the osmoregulation of freshwater fish should be investigated in toxicity- monitoring programs in inland waters.

Tilapia were exposed to sublethal methomyl concentrations of 0, 0.2, 2, 20, or 200 μg/L for 30 d, and then were transferred to methomyl-free water for 18 d. Renal antioxidant parameters, including catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPx) , glutathione reductase (GR), total glutathione (GSH), and reduced glutathione (GSSG), were examined in tilapia at d 0, 6, 12, 18, 24, and 30 after starting the experiment and at 18 d after transferring to methomyl-free water. There were no significant changes in enzymatic activity and content of antioxidants in kidney of tilapia exposed to 0.2 μg/L methomyl compared to controls. The results showed significant increases in SOD, CAT, GST, GR, GPx, and level of GSSG accompanied by a decrease in GSH levels following methomyl exposure in tilapia to 2, 20, or 200 μg/L over the 30-d exposure period, suggesting the presence of oxidative stress. Thus, it would appear the 0.2 μg/L methomyl might be considered the no-observed-adverse-effect level (NOAEL). Recovery data showed that the effects produced by lower concentration of methomyl at 20 μg/L were reversible but not at the higher 200 μg/L concentration.

This study clarified the suitability of fishes caught from illegal fish farms to human consumption and their hazards to public health. For this purpose, the concentrations of some metals (Al, Cd, Pb, Hg and Ni) in water and Nile tilapia (Oreochromis niloticus) fish samples collected from an illegal fish farm, in addition to pathological conditions of the fish tissues, were examined. The illegal farm water was found to be heavily polluted with metals which far exceeded the permissible limits. It was found that metals accumulated in tissues of O. niloticus in concentrations higher than those of farm water. Kidney of O. niloticus contained the highest concentrations of the detected metals, while muscle and skin contained the lowest concentrations. The examination of fish tissues revealed various histopathological lesions which related directly to the pollution of the illegal farm water. Moreover, metals levels in O. niloticus muscle were higher than the maximum permissible levels for human consumption. Consequently, the flesh of fishes from the illegal farms could be considered hazardous to human health. Therefore, warning against eating fish caught from the illegal fish farms should be announced. Moreover, removal of such illegal fish farms is necessary for the public health protection., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The aim of this study was to describe the time-course of estrogen-induced gene expression, corresponding plasma protein detection and histological alterations after cessation of octylphenol (OP) exposure of Cichlasoma dimerus, to test differential responses of biomarkers suitable for environmental monitoring. Male fish were exposed to a nominal concentration of 150 μg/L OP for 28 days, and later transferred to OP-free water aquaria for 1, 3, 7, 14, 21 or 28 days. Blood and mucus samples were obtained in order to analyze vitellogenin (VTG) and zona pellucida (ZP) proteins by Western blot; liver samples were used for gene expression and to assess tissue damage and further recovery of all the analyzed endpoints. Partial sequences of C. dimerus VTG and Na⁺/K⁺-ATPase were obtained. Comparison with VTGs of several teleosts supports that the partial sequence obtained for C. dimerus belongs to VTGAb type. ZP and VTG expression was highly up-regulated by OP. Immunoreactive (ir-) bands of 62, 52 and 50 kDa for ZP and 140, 103, 75 and 64 kDa for VTG, were detected after 28 days of OP exposure in plasma and mucus samples. After transfer of treated fish to clean water, ZP ir-bands in plasma disappeared rapidly (day 3), while VTG ir-bands decreased gradually; no ir-bands were detected on day 28 of recovery. Similarly, ZPB transcripts abruptly returned to background levels (day 3), earlier than for ZPC (day 7) or VTG (day 14). Liver from OP treated fish showed tissue disarrangement, eccentric and euchromatic hepatocytes nuclei and intense perinuclear basophilia. After the recovery period, these changes were still evident though less pronounced, accounting for irreversibility of tissue damage or the requirement for a longer period of depuration. The present results confirm that for biochemical and molecular biomarkers, such as induction of female proteins in male fish exposed to OP, complete recovery is achieved after adequate time of depuration (28 days). Male ZPB expression reflects a recent exposure to estrogenic contaminants, while VTG may reveal past exposures. The combination of biomarkers with different temporal responses such as C. dimerus ZP and VTG provides a more comprehensive interpretation of pollution status., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The effects of sub-lethal concentrations of lindane on behavioral, hematological and histological parameters in Etroplus maculatus were investigated. The LC₅₀ value of lindane for E. maculatus was estimated using the Probit method and was found to be 0.028 mg/L. The red blood cell count (RBC) and the hemoglobin (Hb), hematocrit (Ht), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) were significantly reduced (p > 0.0001) in fish exposed to the toxicant concentrations compared to the control groups. However, the white blood cell count (WBC) was observed to be significantly higher (p < 0.0001). Observations of the tissues showed that lindane had profound destructive effects on the gills, liver and kidney of the fish. The gills showed proliferation of the lamellar epithelium and lamellar fusion, the liver showed necrosis and the kidneys had constriction of the tubular lumen. The frequency of observed behaviors had the same levels of significance throughout the period of study. There was a reduction in the frequency of occurrence between test concentrations, but remained significantly higher than the control. The study shows that lindane is harmful to E. maculatus at sub-lethal concentrations and that the application of this pesticide close to bodies of water is a dangerous threat to aquatic life., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Copper sulfate (CuSO(4))is an inorganic chemical product worldwide used as an algaecide and a fungicide in aquaculture and agriculture and being discharged into freshwater environments where it can affect the freshwater fauna, especially fishes. The impact of copper on fish cardiac function was analyzed in two groups of Nile tilapias, Oreochromis niloticus (control group and group exposed to 1 mg l(-1) of CuSO(4) for 96 h). Structural and ultra-structural changes were studied and related to perturbations of the inotropic and chronotropic responses of ventricle strips. Fish of Cu exposed group did not show significant alterations in the medium diameter and in the percentage of collagen in the cardiac myocytes when evaluated through the light microscope. However, the ultrastructural analysis revealed cellular swelling followed by mitochondrial swelling. The myofibrils did not show significant variations among groups. Force contraction was significantly decreased, and rates of time to tension increase (contraction) and decrease (relaxation) were significantly augmented after copper exposure. The results suggest that the copper sulfate impairs the oxidative mitochondrial function and consequently alters the cardiac performance of this species.

This study focused on several wetlands in Laguna del Tigre National Park (Guatemala) as part of Conservation International's Rapid Assessment Program. Sediment and water samples were collected from a laguna near Xan field, Guatemala's largest oil facility, and three other sites for determination of levels of polycyclic aromatic hydrocarbons (PAHs). Cichlid fish (Thorichthys meeki and Vieja synspila) were collected for determination of DNA strand breakage (by gel electrophoresis), chromosomal breakage (flow cytometry), and fin erosion. For T. meeki from Xan field, chromosomal breakage and strand breakage was greater than in at least two of the three reference sites. For V. synspila, chromosomal breakage and strand breakage were greater in Xan than one of the two reference sites. Fin erosion was observed only at the Xan laguna. Genetic biomarker effects and fin erosion, along with patterns of aqueous PAH concentrations, indicate that fish are affected by anthropogenic contaminants. PAHs were elevated at some reference sites, but environmental forensic analysis suggested a pyrogenic or diagenic origin. It is possible that oil field brines injected into the ground water caused fin erosion and genotoxicity in fish at Xan field, and it is also possible that pyrogenic PAHs influence levels of DNA damage in reference sites. These analyses represent one of the first efforts to examine genotoxicity in native Mesoamerican cichlids.

Nile tilapia Oreochromis niloticus at 9 days post-hatch were exposed in semi-static experiments to the carbamate insecticide carbofuran, which is applied in agricultural systems in Brazil. Although the molecular mechanism of carbofuran toxicity is well known, a detailed understanding of the ecological mechanisms through which carbofuran effects can propagate towards higher levels of biological organization in fish is incomplete. Mortality rates were quantified for larvae exposed for 96 h to 8.3, 40.6, 69.9, 140, 297 and 397 μg/L carbofuran, and the LC(50) 96 h was 214.7 μg/L. In addition, the biochemical biomarker cholinesterase inhibition and behavioral biomarkers related to vision, swimming, prey capture and predator avoidance were quantified in individual larvae, as well as their growth in weight. The behavioral parameters were quantified by analysis of digitally recorded videos of individual larvae within appropriate experimental setups. The activity of the enzyme cholinesterase decreased after exposure to carbofuran with a lowest observed effects concentration (LOEC) of 69.9 μg/L. Visual acuity deficits were detected after carbofuran exposure with a LOEC of 40.6 μg/L. Swimming speed decreased with carbofuran exposure, with a LOEC of 397.6 μg/L. The number of attacks to prey (Daphnia magna nauplii) decreased in larvae exposed to carbofuran, with a LOEC of 397.6 μg/L. Growth in weight was significantly reduced in a dose dependent manner, and all carbofuran groups exhibited a statistically significant decrease in growth when compared to controls (p<0.05). The number of predator attacks necessary to capture larvae decreased after exposure to carbofuran, and the LOEC was 69.9 μg/L. These results show that exposure of sensitive early life stages of tilapia O. niloticus to sublethal concentrations of carbofuran can affect fundamental aspects of fish larval ecology that are relevant to recruitment of fish populations, and that can be better understood by the application of behavioral biomarkers., (Copyright © 2011 Elsevier B.V. All rights reserved.)