Histopathology of rainbow trout exposed to sublethal concentrations of methiocarb or endosulfan

Protective role of selenium and selenium-nanoparticles against multiple stresses in Pangasianodon hypophthalmus

Pollution and climate change pose significant threats to aquatic ecosystems, with adverse impacts on aquatic animals, including fish. Climate change increases the toxicity of metal in aquatic ecosystems. To understand the severity of metal pollution and climate change, an experiment was conducted to delineate the mitigation potential of selenium (Se) and selenium nanoparticles (Se-NPs) against lead (Pb) and high temperature stress in Pangasianodon hypophthalmus. For the experiment, five isonitrogenous and isocaloric diets were prepared, varying in selenium supplementation as Se at 0, 1, and 2 mg kg-1 diet, and Se-NPs at 1 and 2 mg kg-1 diet. The fish in stressor groups were exposed to Pb (1/20th of LC50 concentration, 4 ppm) and high temperature (34 °C) throughout the experiment. The results demonstrated that dietary supplementation of Se at 1 and 2 mg kg-1 diet, as well as Se-NPs at 1 mg kg-1 diet, significantly reduced (p < 0.01) the levels of lactate dehydrogenase and malate dehydrogenase in both liver and muscle tissues. Additionally, the levels of alanine aminotransferase and aspartate aminotransferase in both gill and liver tissues were significantly decreased (p < 0.01) with the inclusion of Se and Se-NPs in the diets. Furthermore, the enzymes glucose-6-phosphate dehydrogenase in gill and liver tissues, fructose 1,6-bisphosphatase in liver and muscle tissues, and acid phosphatase in liver tissue were remarkably reduced (p < 0.01) due to the supplementation of Se and Se-NPs. Moreover, dietary supplementation of Se and Se-NPs significantly enhanced (p < 0.01) the activity of pyruvate kinase, glucokinase, hexokinase, alkaline phosphatase, ATPase, protease, amylase, lipase, and RNA/DNA ratio in the fish. Histopathological examination of gill and liver tissues also indicated that Se and Se-NPs protected against structural damage caused by lead and high-temperature stress. Moreover, the study examined the bioaccumulation of selenium and lead in muscle, water, and diets. The aim of the study revealed that Se and Se-NPs effectively protected the fish from lead toxicity and high-temperature stress, while also improving the function of cellular metabolic enzymes in P. hypophthalmus.

The effects of the water-soluble fractions of crude oil on liver and kidney tissues of Caspian Kutum juveniles, Rutilus frisii

The lethal and histopathological impacts of crude oil's Water-Soluble Fraction (WSF) on the liver and kidney tissues of juvenile Rutilus frisii were investigated. The LC₅₀ 96 h of WSF was calculated at 33.95 ppm. Fish exposed to two concentrations (0.1 LC₅₀ and LC₅₀) of WSF and control for 24 and 96 h were used for histopathological studies. Tissues in the control group and 0.1 LC₅₀-24 h were healthy, and no specific damages were observed. With increasing exposure time (96 h) and concentration (LC₅₀), damages' type, frequency, and intensity gradually increased. Cloudy swelling, loss of cell boundary, nuclei deformation, and congestion of blood vessels were found in the liver, enlarged glomeruli, reduced Bowman's space, and occlusion of the tubular lumen, were found in the kidney. It is demonstrated that the WSF of crude oil can cause severe damage to the tissues of juvenile Kutum, depending on the exposure concentration.

Toxicity of synthesized silver nanoparticles in a widespread fish: A comparison between green and chemical

Metallic nanoparticles are gaining importance in various fields of life due to their large surface area to volume ratio. However, metallic nanoparticles pose different toxic effects on fish when they appear with different shapes and compositions in water. Herein the present study was designed to evaluate the median (LC₅₀) and sub-lethal (1/10th of LC₅₀) concentrations of Ag-Green NPs, 700 μg/L for Ag-Chem NPs, and 50 μg/L for Ag₂O-Chem NPs were confirmed in Hypophthalmichthys molitrix. Furthermore, exposure of H. molitrix fingerlings to 10 % of LC₅₀ concentration of these particles induced significantly higher (p < 0.05) activities of serum alanine transaminase, aspartate aminotransferase, lactate dehydrogenase, white blood cells, acetylcholinesterase and catalase, superoxide dismutase, peroxidase, relative gene expressions of antioxidant enzymes, heat shock protein (Hsp70), hypoxia- inducible factor 1-alpha (HIF-1α) and lipid peroxidase level than the control, but decreased hematological parameters with less effects of Ag-Green NPs than chemically synthesized AgNPs. Moreover, the histopathological study also indicated morphological changes in the liver and gills of treated fish groups. The comparative toxicity evaluation revealed the maximum negative effect of Ag₂O-Chem NPs followed by Ag-Chem NPs while Ag-Green NPs showed the least toxic effects. Based on our results, replacement of chemically synthesized NPs to green synthesized AgNPs can be recommended in large scale application to reduce the noxious effects to aquatic environment.

Improving the assessment of polluted sites using an integrated bio-physico-chemical monitoring framework

Soil - water pollution resulting from anthropogenic activities is a growing concern internationally. Effective monitoring techniques play a crucial role in the detection, prevention, and remediation of polluted sites. Current pollution monitoring practices in many geographical locations are primarily based on physico-chemical assessments which do not always reflect the potential toxicity of contaminant 'cocktails' and harmful chemicals not screened for routinely. Biomonitoring provides a range of sensitive techniques to characterise the eco-toxicological effects of chemical contamination. The bioavailability of contaminants, in addition to their effects on organisms at the molecular, cellular, individual, and community level allows the characterisation of the overall health status of polluted sites and ecosystems. Quantifying bioaccumulation, changes to community structure, faunal morphology, behavioural, and biochemical responses are standard procedures employed in biomonitoring studies in many High-Income Countries (HICs). This review highlights the need to integrate biomonitoring tools alongside physico-chemical monitoring techniques by using 'effect-based' tools to provide more holistic information on the ecological impairment of soil-water systems. This paper considers the wider implementation of biomonitoring methods in Low to Middle Income Countries (LMICs) and their significance in pollution investigations and proposes an integrated monitoring framework that can identify toxicity drivers by utilising 'effect-based' and 'risk-based' monitoring approaches.

Analysis of micropollutants in a marine outfall using network analysis and decision tree

The presence of micropollutants (MPs), including pharmaceutical, industrial, and pesticidal compounds, threatens both human health and the aquatic ecosystem. The development and extensive use of new chemicals have also inevitably led to the accumulation of MPs in aquatic environments. Recreational beaches are especially vulnerable to contamination, affecting humans and aquatic animals via the absorption of MPs in water during marine activities (e.g., swimming, sailing, and windsurfing). Additionally, marine outfalls in an urbanized coastal city can cause serious chemical and microbial pollution on recreational beaches, leading to an increase in adverse effects on public health and the ecological system. Therefore, the aim of this study was to, with the use of network and decision tree analyses, identify the features and factors that influence the change in MP concentrations in a marine outfall. These analyses were conducted to inspect the relationship between each MP and its hierarchical structure as well as hydrometeorological variables. Additionally, a risk analysis was conducted in this study in which the MPs were prioritized based on their optimized risk quotient values. During our monitoring of MP concentrations over time at the marine outfall, high concentrations of pharmaceutical and industrial compounds were detected when the tide level was low after rainfall. Furthermore, results of the risk analysis and the prioritization revealed that a total of 18 substances identified in our study posed a risk to the ecosystem; these include major ecotoxicologically hazardous substances such as telmisartan, mevinphos, and methiocarb. Results of the network analysis demonstrated distinct trends for pharmaceutical and industrial substances, whilst those for pesticide compounds were irregular. Additionally, the hierarchical structures for most MPs consisted of rainfall, tide level, and antecedent dry hours; this implies that these factors influence MP dynamics. These findings will be helpful for establishing chemical contamination management plans for recreational beaches in the future.

Determination of Median Lethal Concentration (LC50) for Endosulfan, Heptachlor and Dieldrin Pesticides to African Catfish, Clarias gariepinus and Their Impact on Its Behavioral Patterns and Histopathological Responses

Pesticides such as endosulfan, heptachlor and dieldrin persist in aquatic environments as a result of their resistance to biodegradation. However, there is no adequate information about the toxicity of endosulfan, heptachlor and dieldrin to the aquatic organism, African catfish (Clarias gariepinus)-a high valued widely distributed commercially interesting species. The current experiment was performed with the aim to determine the median lethal concentration (LC50) of endosulfan, heptachlor and dieldrin to African catfish (Clarias gariepinus); their behavioral abnormalities and histopathological alterations in several vital organs. A total of 324 juvenile fish were exposed for 96 h to six concentrations of endosulfan and dieldrin at 0, 0.001, 0.002, 0.004, 0.008 and 0.016 ppm, and to heptachlor at concentrations of 0, 0.02, 0.04, 0.08, 0.16 and 0.32 ppm for dose-response tests. The study demonstrated that the species is highly susceptible to those contaminants showing a number of behavioral abnormalities and histopathological changes in gill, liver and muscle. The 96-h LC50 value of endosulfan, dieldrin and heptachlor for the African catfish was found as 0.004 (0.001-0.01) mg/L, 0.006 mg/L and 0.056 (0.006-0.144) mg/L, respectively. Abnormal behaviors such as erratic jerky swimming, frequent surfacing movement with gulping of air, secretion of mucus on the body and gills were observed in response to the increasing exposure concentrations. Histopathological alterations of liver, gill and muscle tissues were demonstrated as vacuolization in hepatocytes, congestion of red blood cells (RBCs) in hepatic portal vein; deformed secondary lamellae and disintegrated myotomes with disintegrated epidermis, respectively. These findings are important to monitor and responsibly manage pesticide use in and around C. gariepinus aquacultural areas.

Investigation of oxidative stress enzymes and histological alterations in tilapia exposed to chlorpyrifos

Chlorpyrifos (ChF) is an organophosphate pesticide that is widely used in agricultural fields and indoor for controlling pests. Aquatic ecosystems are the recipients of various pesticide residues due to leaching spray drift and agricultural runoff and pose toxicity for aquatic organisms. Therefore, the current study was designed to investigate the oxidative stress enzymes and histological alterations in the vital organs of tilapia due to ChF exposure. LC50 (24 h) was calculated as 52.78 μg/l by exposing tilapia with different acute concentrations of ChF. For assessment of sub-lethal toxicity of ChF, the fish were divided into four groups (ChF1, ChF2, ChF3, and control group). ChF1 group was treated with 1/15th of LC50, whereas ChF2 and ChF3 groups were treated with 1/10th and 1/5th of LC50, respectively for 14 days. After that, ChF induced changes in oxidative stress enzymes and histological alterations were evaluated. It was found that the level of glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) increased significantly in the liver of ChF-treated tilapia. Histological study of liver tissues showed an increased number of Kupffer cells, hydropic degeneration, necrosis, and hemorrhage. In the spleen of treated fish, increased melanomacrophage centers, necrosis, and congestion were detected. Disorganized muscle fibers, cardiac muscle fiber degeneration, and coagulative necrosis were observed in the heart of ChF-treated fish. It is concluded that sub-lethal concentrations of ChF can induce oxidative stress and histological alterations in the tissues of tilapia.

Impacts of Neonicotinoids on Molluscs: What We Know and What We Need to Know

The broad utilisation of neonicotinoids in agriculture has led to the unplanned contamination of adjacent terrestrial and aquatic systems around the world. Environmental monitoring regularly detects neonicotinoids at concentrations that may cause negative impacts on molluscs. The toxicity of neonicotinoids to some non-target invertebrates has been established; however, information on mollusc species is limited. Molluscs are likely to be exposed to various concentrations of neonicotinoids in the soil, food and water, which could increase their vulnerability to other sources of mortality and cause accidental exposure of other organisms higher in the food chain. This review examines the impacts of various concentrations of neonicotinoids on molluscs, including behavioural, physiological and biochemical responses. The review also identifies knowledge gaps and provides recommendations for future studies, to ensure a more comprehensive understanding of impacts from neonicotinoid exposure to molluscs.

Histopathology changes in the rainbow trout (Onchorhyncus mykiss) consuming boric acid supplemented fish fodder

OBJECTIVE

Even though boron (B), as a trace micronutrient, occurs in natural waters and organisms, its high concentration could cause harmful and even toxic for organisms. The aim of present study was to investigate the effects of boric acid (BA) added to feed (0.01%, 0.05%, 0.10%, and 0.20% of B in feed) on Rainbow Trout (Oncorhynchus mykiss) by histopathological methods and compared to the control feed as without B.

METHODOLOGY

At the end of the feeding, after weighing the live weight of 9 rainbow trout from each group, tissue fragments were taken from the liver, gill, kidney, skeletal muscle, spleen and brains of fish, which systemic necropsies was done, and were fixed in 10 % buffered formalin solution.

RESULTS

Histopathological examinations revealed degenerative and necrotic changes in the liver, gill, kidney, skeletal muscle, spleen and brain. Hydropic and vacuolar degenerations in liver parenchyma, lamellar edema in the gills, hyaline accumulation in the kidneys, degenerations in the muscles, necrosis in the spleen and hyperemia in the brain were observed in all groups except control group. It was observed that the destruction of boric acid on fish increased depending on the amount of boron supplemented to the feed, and the most effect was in the group fed with 0.20 % boron supplemented feed.

CONCLUSIONS

The findings aside from causing pathological changes in all organs in terms of histopathological findings of Boric Acid (BA), the most severe lesions were observed in the liver.

Multiorgan histopathological changes in the juvenile seabream Sparus aurata as a biomarker for zinc oxide particles toxicity

Zinc oxide nanoparticles are widely used in some domains (cosmetics, pharmaceuticals optical devices, and agricultural field) due to their physical, optical, and antimicrobial properties. However, the release of ZnO-NPs into the environment may affect organisms like fish with potential consequences for human health. Histological approaches of the acute effects of these materials on fish are scarce; thus, the present study aimed to investigate the potential toxic effects of acute exposure to ZnO particles in marine environments, by assessing histological changes in the gills, liver, spleen, and muscle of gilthead seabream (Sparus aurata) juveniles. Thus, fish were exposed for 96 h, via water, to 1 mg L-1 of ionic zinc and zinc oxide particles (1.1, 1.2, and 1.4 μm of size). Histological examination revealed gills as the most affected organ, followed by liver, muscle, and spleen. In the gills, histopathological changes included hyperplasia of epithelial cells, fusion of the secondary lamellae, and lifting of the lamellar epithelium with edema. In the liver, lipid vacuolation of several degrees, necrosis of hepatic and pancreatic tissues, blood congestion in sinusoids and hepatoportal vessels, presence of cellular infiltrate, and melano-macrophages diffusion was found. Muscle showed degeneration, atrophy, thickening and necrosis of muscle fibers with edema between them, and presence of melano-macrophages in the muscle layer. Spleen was the less damaged organ, displaying congested blood, white pulp increase/rupture, and bigger and darker melano-macrophage aggregates in the splenic stroma. These results underline that the size of particles plays a determinant role in their potential pernicious effects. A short-term exposure caused major histopathological changes in relevant organs of S. aurata juveniles, possibly affecting their function.

Synergistic effect of zinc nanoparticles and temperature on acute toxicity with response to biochemical markers and histopathological attributes in fish

In the present study, an experiment was carried out to delineate the lethal concentration of (LC₅₀) zinc nanoparticles (Zn-NPs) alone and with concurrent to high temperature (34 °C) in Pangasianodon hypophthalmus. The lethal concentration of Zn-NPs alone and with high temperature was estimated as 21.89 and 19.74 mg/L respectivey in P. hypophthalmus. The lethal concentration was decided with the help of definite concentration via 16, 18, 20, 22, 24, 26, 28 and 30 mg/L. The Zn-NPs were significantly alter the biochemical and histopathology of different fish tissues. The stress biomarkers such as oxidative stress (catalase superoxide dismutase and glutathione-s-transferase, lipid peroxidation) was studied in the liver, gill and kidney tissue, which was noticeable (p < 0.01) enhanced with higher concentration in both condition (Zn-NPs alone and Zn-NPs-T) in dose dependent manners. The carbohydrate (lactate dehydrogenase and malate dehydrogenase) and protein metabolic enzymes (alanine amino transferase and aspartate amino transferase) were also remarkable enhanced (p < 0.01) with higher concentration of Zn-NPs and Zn-NPs-T. The neurotransmitter (acetylcholine esterase) activities were significant inhibited (p < 0.01) with exposure to Zn-NPs and Zn-NPs-T and digestive enzymes such as protease and amylase were non-significant (p > 0.01) with the exposure of Zn-NPs and Zn-NPs-T, further, lipase were significantly reduced (p < 0.01) with exposure to Zn-NPs and temperature exposure group. The histopathological alteration were also observed in the liver and gill tissue. The present investigation suggested that, essential trace elements at higher concentration in acute exposure led to pronounced deleterious alteration on histopathology and cellular and metabolic activities in fish.

Histopathological effects of the antibiotic erythromycin on the freshwater fish species Oncorhynchus mykiss

Pharmaceuticals are found in the aquatic compartment due to their continuous release in wastewater effluents or direct dispersal in aquaculture practices raising serious threats to human and environmental health. Erythromycin (ERY) is a macrolide antibiotic widely prescribed in human and veterinary medicine to threat a number of bacterial infections, being consequently found in the aquatic environment. The present work intends to evaluate the sub-lethal effects of ERY on juveniles of rainbow trout (Oncorhynchus mykiss) in terms of tissue damage using histochemical staining procedures. Individuals were exposed for 96 h (acute exposure: 0.001-10 mg/L) and 28 days (chronic exposure: 0.05-0.8 μg/L) to environmentally realistic concentrations of ERY. Qualitative and quantitative approaches were used to assess O. mykiss gills and liver tissue alterations after exposure to ERY. For both exposures the most common gill changes recorded were progressive (e.g. hypertrophy of mucous cells and hyperplasia of the epithelial cells). However, circulatory (e.g. aneurysms and oedemas) and regressive (e.g. epithelial lifting of lamellae and lamellar fusion) changes were also observed in the acute assay. Gill morphometric analysis revealed to be a good indicator of subtle alterations in gill architecture in agreement with the qualitative scoring system. In liver, regressive (e.g. cytoplasmic vacuolization, pyknotic nucleus and hepatocellular degeneration) and circulatory disturbances (e.g. hemorrhage and increase of sinusoidal space) were the most frequently observed alterations, but only for the acute assay. Furthermore, all histological changes observed contributed to a significant increase in the pathological index for both organs. The current data demonstrate the existence of a direct dose-effect relationship between the exposure to this specific macrolide antibiotic and the histological disorders recorded in different tissues of the exposed fish. The histopathological findings observed in this study may have been the result of several physio-metabolic dysfunctions. However, the observed tissue lesions were of minimal or moderate pathological importance, non-specific and reversible. Further investigation into the cellular mechanism of action of ERY is needed.

An integrated approach in subtropical agro-ecosystems: Active biomonitoring, environmental contaminants, bioaccumulation, and multiple biomarkers in fish

Aquatic contamination in agricultural areas is a global problem, characterized by a complex mixture of organic and inorganic pollutants whose effects on biota are unpredictable and poorly investigated. In this context, in the present study, the Neotropical fish Prochilodus lineatus was confined in situ for 120 days in two sites with different levels of anthropic impact: 1) a fish hatchery station, within the State University of Londrina (reference site - REF) and 2) an agro-ecosystem area in one of the most productive regions of southern Brazil (experimental site - EXP). We evaluated multiple biomarkers at different levels of biological organization, such as biotransformation and antioxidant enzymes, oxidative damages, DNA damages and liver histopathology. We also evaluated the occurrence of 22 organochlorine pesticides (OCPs) and 6 trace metals in water and sediment; and 33 current-use pesticides (CUPs) in the water; besides the presence of OCPs in the liver and metals in different tissues of the confined fish. The chemical analysis confirmed that the two environments presented different levels of contamination. We verified a distribution gradient of data in the principal component analysis (PCA), separating the REF fish to one side and the fish at the agricultural area (EXP) to the other side. In general, the biomarker responses were more altered in fish from the EXP than fish from the hatchery station; and this fish presented a greater accumulation of endosulfan (an increase of 18× compared to basal value) and showed oxidative, genetic, and histological damage. Through the Biomarkers Response Index (BRI), we found that the EXP fish demonstrated a decrease in health status compared with the REF fish during the confinement time, due to their exposure to a higher concentration of contaminants. In conclusion, the use of multiple biomarkers at different response levels is an important tool for environmental monitoring.

Oxidative and Cellular Metabolic Stress of Fish: An Appealing Tool for Biomonitoring of Metal Contamination in the Kolkata Wetland, a Ramsar Site

The present study delineate the various biochemical and histopathological tool to evaluate as strong biomarker in the field condition for detection of the least and maximize level of pollution and contamination. We have collected Labeo rohita from 13 different sites from East Kolkata wetland to determine biochemical and histopathological status to analyse metal contamination in the significant biological hot spot EKW. The biochemical marker as antioxidative status, i.e., catalase, superoxide dismutase (SOD), and glutathione-S-transferase (GST) in liver and gill, were remarkably higher (p < 0.01) at some of the sampling sites, but catalase in brain, SOD in kidney, GST in brain and kidney, and neurotransmitter as acetylcholine esterase (AChE) in brain were not significant (p > 0.05) among the sampling sites. The glycolytic enzymes, such as lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in liver, gill, and muscle, and protein metabolic enzymes, such as alanine amino transferase (ALT) and aspartate amino transferase (AST) in liver, gill, muscle, and kidney, were noticeably higher (p < 0.01) at some of the sampling sites. The histopathology of the liver and gill were altered at different sampling sites, such as blood congestion, leucocyte infiltration with parenchymal vacuolisation, nucleus with blood vessels, hepatocytes granular degeneration, haemorrhage, karyorrhexis, shrink nucleus, and pyknotic nuclei in liver. In the gill, structural changes, such as complete destruction and shortening of secondary gill lamellae, blood vessel in gill arch, curling of secondary gill lamellae, aneurism in gill lamellae, and neoplasia, were observed. Most of the metals were found within the safe limit all along the 13 sampling sites, indicating that fishes are safe for the consumption. Based on our finding, we could recommend that a rational application of biochemical profiles, such as oxidative and metabolic stress parameters, including histopathology to be used as biomarkers for biomonitoring the metal contamination in the aquatic environment.

Changes in the gills of the European eel (Anguilla anguilla) after chronic exposure to environmental cocaine concentration

The recent discovery of illicit drugs in the aquatic environment has raised concerns about the possible effects on the aquatic fauna, because of the pharmacological activity of these substances. Cocaine is an illicit drug widespread in surface waters since it is the third most widely used drug in North America, Western and Central Europe, and the second in Latin America and the Caribbean. The aim of this study was to evaluate the influence of environmental concentrations of cocaine on the gills of the European eel (Anguilla anguilla). The gills of male silver eels exposed to 20 ng L^-1 of cocaine for fifty days were compared to control, vehicle control and post-exposure recovery ten days groups. The following parameters were evaluated: the thickness of the interlamellar epithelium (TIE), the length of the secondary lamellae (LSL) and the fraction of the interlamellar epithelium and the secondary lamellae occupied by the mucous cells (MC(IE-SL)FA) 3) the plasma cortisol and prolactin levels. After cocaine exposure, the gill epithelium appeared hyperplastic. The following changes were observed: proliferation in the interlamellar epithelium; partial and total fusion of the secondary lamellae, that appeared shortened and dilated; epithelial lifting and aneurism in the secondary lamellae. Moreover, in cocaine exposed eels, an increase in TIE and MC(IE-SL)FA and a decrease in LSL were observed. These changes were still present ten days after the interruption of cocaine exposure. Plasma levels of both cortisol and prolactin increased after cocaine exposure; ten days after the interruption of cocaine exposure, the plasma cortisol levels were still higher, whereas the plasma prolactin levels were lower, than control values. Our results show that even a chronic exposure to low environmental cocaine concentrations severely harms the eel gills, suggesting damages to their functions, and potentially affecting the survival of this species.

Comparative toxicity of chlorpyrifos: Sublethal effects on enzyme activities and histopathology of Mugil cephalus and Chanos chanos

Ecotoxicological data and potential impact of chlorpyrifos (CPF) in the region are scarce for prescribing safety limits. Therefore, toxicity and sublethal impact of CPF on fish fingerlings of Mugil cephalus (3.0 ± 1.2 cm) and Chanos chanos (3.0 ± 1.5 cm) were studied. Acute and chronic toxicity tests were conducted by continuous flow through method and derived 96 h median lethal concentration (LC₅₀). Mean LC₅₀ value of 1.13 μg/L for M. cephalus, and 3.20 μg/L for C. chanos were derived by Probit. Chronic toxicity tests were conducted for 30 days and determined no observed effect concentration values of 0.09 μg/L 0.17 μg/L and lowest observed effect concentration values of 0.16 μg/L 0.32 μg/L and chronic values of 0.13 μg/L 0.25 μg/L for M. cephalus and C. chanos respectively. Key biomarker enzyme activities viz., EST, SOD and MDH were studied at sublethal concentrations of CPF. Native gel electrophoresis revealed gradual decrease in isoforms of EST and SOD activities, whereas MDH activity increased in fingerlings. These responses indicate inhibition of cholinesterase, antioxidants and synthesis of ATPs in the cells due to CPF stress. Pathological lesions were evaluated in gill and eye tissues of fingerlings. Epithelial fusion and degenerative changes were prominent in primary lamellae. Hyperplasia, lifting epithelium, fusion of lamellae and necrosis were evidenced in the secondary lamellae. Cellular anomalies in the retina of the eye of C. chanos include vacuoles in nerve fiber layer, shrinkage of outer plexiform layer and detachment of pigment epithelium layer. These changes indicate physiological disturbance in the gill and eye.

Sublethal chronic effects of oral dietary exposure to deltamethrin in Swiss albino mice

The hazards of dietary exposure to environmentally relevant levels of deltamethrin are poorly understood though studies enunciate the acute toxicity hazards. In this study, prolonged exposure to low levels of deltamethrin in mice was investigated. The mice were exposed daily via gavage method for 60 days. Four doses (0.1, 0.05, 0.01, and 0.005 mg/kg bwt/d) were selected, which are equal to or less than the maximum residue limits for deltamethrin permitted in animal food/feed. Liver, kidney, lungs, spleen, and testes were collected on day 61 for histology, residue, and biochemical analysis (aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALKP), total bilirubin (TBIL), total proteins (TPs), cholesterol (CHOL), urea, and creatinine). No significant changes were observed in body weight gain in all treatment groups ( p > 0.05). The gas chromatography analysis indicated that none of the tissue samples contained deltamethrin residues above the limits of quantification. The significant differences in biochemical profile (AST, ALT, TBIL, and creatinine) reported in animals exposed to 0.1 and 0.05 mg/kg bwt/d deltamethrin ( p < 0.05) suggest respective tissue injury and lipid peroxidation; however, few significant changes in urea and CHOL were also reported in doses 0.01 and 0.005 mg/kg bwt. No significant differences in TP and ALKP were observed ( p > 0.05). The target organs for deltamethrin toxicity showed prominent histopathological changes in concentrations of 0.1 and 0.05 mg/kg bwt. Other two doses showed no or sporadic changes. Our findings suggest that chronic exposure to environmentally relevant levels of deltamethrin can have detrimental effects on vital organs in the circumstances allowing daily exposure, in congruence with available literature.

Alterations in the activity of certain enzymes in the gills of a carp Labeo rohita exposed to an azo dye, Eriochrome black T: a biochemical investigation

In Labeo rohita exposed to sub-lethal concentrations of an azo dye, Eriochrome black T for 4 days, gills show considerable alterations in the activity of certain metabolic enzymes-alkaline phosphatase, acid phosphatase, carboxylesterase, lactate dehydrogenase, and succinate dehydrogenase; and antioxidant enzymes-catalase and peroxidase. The activities of alkaline phosphatase, acid phosphatase, carboxylesterase, succinate dehydrogenase, catalase, and peroxidase decline significantly. This has been associated with impaired metabolic function of the gills due to azo dye toxicity. The activity of lactate dehydrogenase, in contrast, shows a gradual increase, reflecting a shift from aerobic to anaerobic metabolism. In the fish kept for recovery for 8 days, after exposing the fish to the dye for 4 days, activity of succinate dehydrogenase, alkaline phosphatase, and lactate dehydrogenase gradually become similar to control. Nevertheless, activity of acid phosphatase, catalase, peroxidase, and carboxylesterase, although recover gradually, remained significantly low as compared to that of control. This study signifies that the dye is highly toxic to Labeo rohita and suggests that the activity of metabolic and antioxidant enzymes can be used as biomarker for fish toxicity.

Toxicological effect of Al2O3 nanoparticles on histoarchitecture of the freshwater fish Oreochromis mossambicus

In the present study, freshwater fish Oreochromis mossambicus were exposed to sub lethal concentrations (120, 150 and 180 ppm) of Aluminium oxide nanoparticles (Al₂O₃ NPs) for 96 h. Histological abnormalities were not observed in the organs of control fishes whereas severe damages and extensive architectural loss was found in the brain, gill, intestine, kidney and muscle tissues of treated fishes with more pronounced effects in 180 ppm. The results showed that the acute exposure to Al₂O₃NPs altered the histoarchitecture in various fish tissues.

Endosulfan Toxicity to Anabas testudineus and Histopathological Changes on Vital Organs

The toxicity of endosulfan, an organochlorine type insecticide to a commonly consumed freshwater fish species, A. testudineus (40.68±9.03 g; 13.49±0.99 cm), was investigated under static conditions. The nominal endosulfan concentrations ranging from 10 to 80 μg/L subjected to the fish population results in 96-hour median lethal concentration, LC50, of 35.2±3.99 μg/L. The toxicity is a function of both endosulfan concentration and exposure time (p>0.05). Histopathological analysis on vital organs exposed to sublethal concentrations indicates that structural changes started at sublethal dose and the effects aggravated with increasing endosulfan concentration. Gill was found to experience aneurism, hyperplasia in lamellar and autolysis of mast cell. Pyknotic nuclei and necrosis were observed in liver cell, while the lumen of renal tubule was found to narrow and haemorrhage was observed in cytoplasm cell. High LC50 compared to other fishes indicates that A. testudineus has high tolerant to endosulfan, however, endosulfan slowly alters the fish biochemistry and is potentially transferable to human

Comparison of waterborne and intraperitoneal exposure to fipronil in the Caspian white fish (Rutilus frisii) on acute toxicity and histopathology

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Determination of median lethal dose of fipronil in fish for the first time.

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Determination of median lehal concentration of fipronil in the Caspian white fish.

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Comparison of acute toxicity and histopathological effect of fipronil in the fish exposed via different routes.

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Waterborne exposure to fipronil has more effect on gill whereas its intraperitoneal exposure has more effect on kidney.

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Fish exposed to fipronil shows some alterations in brain tissue reported for the first time.

Fipronil is an effective insecticide widely used in agriculture with potential ecotoxicological consequences. The median lethal dose (LD₅₀) and concentration (LC₅₀) of fipronil in 16.3 g Caspian white fish, Rutilus frisii kutum fingerlings were determined. To determine the LD₅₀, a total of 133 fish were assigned to 19 tanks (7 fish/tank) including one control and 6 treatment groups (300, 450, 550, 650, 750, 850 mg/kg). Fish were injected intraperitoneally and monitored at 96 h. The LD₅₀ of fipronil was 632 mg/kg suggesting it was slightly toxic to the Caspian white fish. To determine LC₅₀, 114 fish were assigned to 19 tanks (6 fish/tank) including one control and 6 treatment groups (300, 400, 500, 600, 700, 800 μg/L). The LC₅₀ of fipronil was 572 μg/L, which was highly toxic to the fish. The degree of tissue change (DTC) in vital organs from moribund fish exposed via waterborne exposure showed severe damage (DTC: 71 ± 52 for 700 μg/L) in the gill, including aneurisms, extensive fusion and necrosis. The fish exposed through the intraperitoneal route seemed to have severe lesions (DTC: 66 ± 50 for 750 mg/kg) in the kidney, involving hemorrhage, tubular degeneration and necrosis. The liver had no significant differences in DTC values between the two routes and showed pyknosis and sinusoid dilation. Hematoxylin and eosin staining did not show any histological alterations in the brain but nissl staining showed some alterations in distribution of purkinje cells. Generally, this study showed that the route of exposure to fipronil not only affects its acute toxicity but also determines the main target organs of toxicity and histopathological alterations in Caspian white fish.

Dietary β-glucans differentially modulate immune and stress-related gene expression in lymphoid organs from healthy and Aeromonas hydrophila-infected rainbow trout (Oncorhynchus mykiss)

Although β-glucans stimulating effects have already been demonstrated on the immune system of numerous animal species, available data remain relatively variable and more research should be done regarding the complexity of underlying mechanisms. In this context, the present study aimed to evaluate the stress and immune-related effects of dietary β-glucans (i.e. Macrogard^®) by considering a number of influencing factors such as the dose (0, 0.1, 0.2 and 0.5% in food), feeding duration (15 versus 30 days), tissue (blood, kidney, spleen, gills) and infection status (healthy or infected). Blood parameters (lysozyme, ACH50 activities, leucocyte populations) and mRNA expression level of several immune- and stress-related genes (TFN-α1, IL-1β, IL10, COX-2, TGF-β, MC2R, HSP70) were measured. Our results suggest that spleen may be a highly responsive organ to dietary β-glucans both in healthy or infected fish, and that this organ may therefore significantly contribute to the immune reinforcement induced by such immunostimulatory diet. Our study further reveals that overdoses of β-glucans and/or prolonged medication can lead to a non-reactive physiological status and, consequently, to a poor immune response. All in all, the current data emphasizes the need for further extensive research in the field of dietary β-glucans as a preventive method for farmed fish protection.

Alterations in the skin of Labeo rohita exposed to an azo dye, Eriochrome black T: a histopathological and enzyme biochemical investigation

Histopathological changes and alterations in the activity of certain metabolic and antioxidant enzymes were analyzed in the head skin of Labeo rohita, exposed to sublethal test concentrations of the azo dye, Eriochrome black T for 4 days, using 24 h renewal bioassay method. Hypertrophied epithelial cells, increased density of mucous goblet cells, and profuse mucous secretion at the surface were considered to protect the skin from toxic impact of the azo dye. Degenerative changes including vacuolization, shrinkage, decrease in dimension, and density of club cells with simultaneous release of their contents in the intercellular spaces were associated to plug them, preventing indiscriminate entry of foreign matter. On exposure of fish to the dye, significant decline in the activity of enzymes-alkaline phosphatase, acid phosphatase, carboxylesterase, succinate dehydrogenase, catalase, and peroxidase-was associated with the binding of dye to the enzymes. Gradual increase in the activity of lactate dehydrogenase was considered to reflect a shift from aerobic to anaerobic metabolism. On transfer of azo dye exposed fish to freshwater, skin gradually recovers and, by 8 days, density and area of mucous goblet cells, club cells, and activity of the enzymes appear similar to that of controls. Alteration in histopathology and enzyme activity could be considered beneficial tool in monitoring environmental toxicity, valuable in the sustenance of fish populations.

Cellular stress and histopathological tools used as biomarkers in Oreochromis mossambicus for assessing metal contamination

In the present study, we have analyzed various biochemical and histopathological biomarkers in the Oreochromis mossambicus collected from 18 sites at Bhima River. The biochemical biomarkers viz. antioxidative enzymes in muscle viz. catalase, SOD, and GST, glycolytic enzymes in kidney viz. LDH and MDH, protein metabolic enzymes in liver, gill, brain, gonad and muscle viz. ALT and AST, neurotransmitter enzymes in muscle AChE, lipid peroxidation and histopathology in the liver and gill have been evaluated. The oxidative biomarkers, glycolytic enzymes, protein metabolic enzymes and lipid peroxidation were significantly (p<0.01) higher and AChE in muscle were significantly inhibited (p<0.01) in fishes from different sampling sites. The histopathology of the liver and gill were altered at different sampling sites. The liver histopathology showed hepatocytes vacuolization, haemorrhage, karyokinesis, necrosis, pyknotic nuclei, dilation of sinusoids and hepatocyte granular degeneration and in the gill histopathology showed distal lamellar gill tissue, diffuse epithelial hyperplasia and multifocal mucus cell hyperplasia, extensive edema of epithelial cells, blood congestion and edema in secondary lamellae. All the indicators are giving strong signals for contamination of the aquatic water bodies. The Bhima River is surrounded by several cities and agriculture land indicates that vigorous industrial activity coupled with intensive use of chemicals in agricultural practices may held. Therefore, based on our results, we could recommend that the investigated tissue and cell alterations may be successfully applied as reliable biomarkers for monitoring contaminated freshwater ecosystems. This study suggests that, the importance of antioxidative enzymes, cellular biomarkers, AChE, and histopathology used as biomarkers in aquatic ecosystem biomonitoring.

Inducible headkidney cytochrome P450 contributes to endosulfan immunotoxicity in walking catfish Clarias gariepinus

The effect of endosulfan metabolites on fish immune system is not well known. It is also not clear whether endosulfan accumulates in fish immune organs and undergoes metabolic biotransformation in situ. In the present study we investigated the role of headkidney (HK), an important fish immune organ on endosulfan metabolism and the long term effects of endosulfan metabolites on the fish immune system. C. gariepinus (walking catfish) were exposed to 2.884ppb of endosulfan (1/10th LC50) for 30d followed by their maintenance in endosulfan-free water for 30d for recovery. Endosulfan induced time-dependent reduction in the HK somatic index and histo-pathological changes in renal and hemopoietic components of the organ. At cellular level, exposure to endosulfan led to death of HK leucocytes. Gas-liquid-chromatography documented the presence of both α- and β-isomers of endosulfan along with the toxic metabolite endosulfan sulfate (ESS) in the HK of exposed fishes. We report that β-endosulfan accumulates more readily in the HK. Depuration studies suggested the persistence of ESS in the HK. Enzyme-immunoassay and qPCR results demonstrated direct relationship between cytochrome P450 1A (CYP1A) expression and ESS levels in the HK. Pre-treatment of HKL with CYP1A specific inhibitor α-Naphthoflavone (ANF) led to reduction in CYP1A mRNA, protein levels, and inhibited ESS formation together implicating the role of CYP1A on endosulfan metabolism. When the exposed fish were transferred to endosulfan-free water ('recovered fish') it was observed that after 30d of recovery period the concentration of endosulfan and its metabolite in the HK were significantly reduced, compared to 30-d exposed fish. We also observed improvement in HK histo-architecture but no significant recovery in HKL number and viability. Collectively, our findings suggest that HK plays an important role in endosulfan metabolism. We propose that endosulfan induces the activation of CYP1A in HK which led to the generation of persistent metabolite, ESS, resulting in immunotoxicity.

Acute toxicity, biochemical and histopathological responses of endosulfan in Chanos chanos

This study investigated 96h median lethal concentration of endosulfan (99%, pure α: β ratio of 7:3) by conducting static non-renewable acute toxicity bio-assay in Chanos chanos juvenile with average weight (110±5.65g). Further, the effect of different definitive doses (18.5, 19.5, 20.5, 21.5 and 22.5µg/L) of endosulfan on metabolic, heamato-immunoligcal and histopathological response were probed. Anti-oxidative enzymes CAT, SOD and GST showed significant (p<0.01) increase of activity in the liver, gill and brain during exposure to endosulfan in a dose and time dependent manner. The brain AChE activity showed significant (p<0.01) inhibition from 18.5 to 22.5µg/L exposure of endosulfan than the control group. LDH and MDH activity gradually increased with consequent increasing dose of endosulfan exposure in the liver, gill and brain. Similarly, ALT, AST and G6PDH activities in both liver and gill increased with consequent increases in the dose of endosulfan exposure. Immunological profile such as blood glucose and serum cortisol level significantly enhanced while respiratory burst activity declined with consequent increasing doses of endosulfan exposure. Histopathological alteration in the gill demonstrated curling of secondary lamellae, thickening of primary epithelium, shorting of secondary lamellae, epithelial hyperplasia, fusion of secondary lamellae, aneurism, and collapsed secondary lamellae due to dose dependent exposure of endosulfan. Liver histology illustrated cloudy swelling and necrosis with pyknotic nuclei to the moderate dose of endosulfan, whereas higher dose of endosulfan (21.5µg/L) displayed severe necrosis of hepatic cells. Overall results clearly indicate that acute exposure of endosulfan led to pronounced deleterious alterations on biochemical, heamato-immunological, and histopathological responses of C. chanos juvenile.

Cellular metabolic, stress, and histological response on exposure to acute toxicity of endosulfan in tilapia (Oreochromis mossambicus)

Endosulfan is one of the most hazardous organochlorines pesticides responsible for environmental pollution, as it is very persistent and shows bio-magnification. This study evaluated the impact of acute endosulfan toxicity on metabolic enzymes, lysozyme activities, heat shock protein (Hsp) 70 expression, and histopathology in Tilapia (Oreochromis mossambicus). Among the indicators that were induced in dose dependent manner were the enzymes of amino acid metabolism (serum alanine aminotransferase and aspartate aminotransferase), carbohydrate metabolism (serum lactate dehydrogenase), pentose phosphate pathway (Glucose-6-phosphate dehydrogenase) as well as lysozyme and Hsp70 in liver and gill, while liver and gill Isocitrate dehydrogenase (TCA cycle enzyme) and marker of general energetics (Total adenosine triphosphatase) were inhibited. Histopathological alterations in gill were clubbing of secondary gill lamellae, marked hyperplasia, complete loss of secondary lamellae and atrophy of primary gill filaments. Whereas in liver, swollen hepatocyte, and degeneration with loss of cellular boundaries were distinctly noticed. Overall results clearly demonstrated the unbalanced metabolism and damage of the vital organs like liver and gill in Tilapia due to acute endosulfan exposure.

Histopathological effects of silver and copper nanoparticles on the epidermis, gills, and liver of Siberian sturgeon

The influence of nanoparticles (NPs) on aquatic environments is still poorly documented. The aim of the study was to determine the effects of silver (AgNPs) and copper (CuNPs) nanoparticles on larval Siberian sturgeon (Acipenser baerii) after 21 days of exposure. Acute toxicity of AgNPs on Siberian sturgeon was investigated in a 96-h static renewal study and compared with the toxicity of CuNPs. The AgNPs and CuNPs 96 h mean lethal concentrations (96 h LC50) were 15.03 ± 2.91 and 1.41 ± 0.24 mg L(-1), respectively. Toxicity tests were done in triplicates for each concentration of AgNPs 0.1, 0.5, 1.5 mg L(-1) and CuNPs 0.01, 0.05, 0.15 mg L(-1). The control group was exposed in freshwater. The results indicate that AgNPs and CuNPs exposure negatively influenced survival; body length and mass; and morphology and physiology of the epidermis, gills, and liver of Siberian sturgeon larvae. Fish exposed to AgNPs and CuNPs showed similar pathological changes: irregular structure and pyknotic nuclei of epidermis, aplasia and/or fusion of lamellae, telangiectasis, epithelial necrosis and lifting of the gills, dilation of sinusoidal space, overfilled blood vessels, and pyknotic nuclei of the liver. Fish exposed to CuNPs only demonstrated hyaline degeneration in the gills epithelium and liver. The study shows that CuNPs were more toxic to Siberian sturgeon larvae than AgNPs.

Evaluation of histopathological alterations in the gills of Vardar chub (Squalius vardarensis Karaman) as an indicator of river pollution

Quantification of histopathological alterations in the gills of Vardar chub (Squalius vardarensis Karaman) was performed in 2012 in rivers of north-eastern Macedonia, with the aim to examine the effects of water quality in the rivers (Zletovska and Kriva River-impacted by active Pb/Zn mines; Bregalnica River-contaminated by agricultural waste). The biological alterations in chub were classified as: circulatory disturbances, regressive and progressive changes, but their severity differed. Altogether the mildest changes were observed in the gills of chub from the Bregalnica River, a less polluted river, whereas mining impacted rivers were characterized by more severe alterations. In the gills of chub from the Zletovska River, which is highly contaminated with numerous metals, sulphates and chlorides, the highest lesion indices were found for the regressive changes of both epithelium and supporting tissue, with typical lesions referring to atrophy, thinning and lifting of epithelial cells, necrosis of epithelium and chloride cells, as well as deformations of lamellar cartilaginous base. Gill damages of chub from the Kriva River were overall milder compared to the Zletovska River, in accordance with pollution status. In the gills of chub from that river, progressive changes were more pronounced, specifically severe hyperplasia of mucous cells and epithelium in the interlammellar space, leading to fusion of lamellae, as well as hypertrophy of chloride cells. The comparison between seasons indicated higher intensity of progressive changes in all three rivers in autumn, when water level was very low, and consequently, water contamination was more pronounced due to concentration effect. The pattern and severity of histopathological alterations in the chub gills reflected differences in contamination levels and type of contaminants in different rivers and sampling periods, and thus have been proven as a valuable indicator of water quality.

Pesticides used in cotton production affect reproductive development, endocrine regulation, liver status and offspring fitness in African catfish Clarias gariepinus (Burchell, 1822)

We exposed African catfish Clarias gariepinus from embryo-larvae stage to adult stage (13 months old, BW) to chronic doses of Tihan 175 O-TEQ and endosulfan (Thionex) and assessed the impact of this exposure on endocrine regulation, liver status and offspring fitness. Endosulfan exposure caused a significant increase in plasma estradiol-17β (E2) and decreased plasma testosterone (T) but not 11 ketotestosterone (11-KT). Tihan decreased significantly plasma E2 and 11-KT, but not T. Endosulfan doses altered gonad histology and induced high proportions (18–30% of males) of ovotestis in males and follicular atretic oocytes in females, indicating occurrence of feminization in fish. Tihan also altered gonad histology but only one case of ovotestis was observed at the highest dose. Presence of foam cells in lobular lumen, fibrosis, necrosis, and immature cells released in lobular lumen were found in male gonads and melano-macrophage centers (MMCs), necrosis, fibrosis and vacuolation were observed in female gonads. Fish livers also suffered injuries such as MMCs, necrosis, fibrosis, vacuolation, dilatation of sinusoids, and nuclear pleomorphism. Chronic Tihan and Thionex exposures decreased fertilization rate, hatching rate, ova and larval weight, as well as larval resistance to osmotic choc. They also delayed hatching and increased abnormalities in the F1 generation, all these indicators suggesting transgenerational effects of these compounds.

Lipotropes protect against pathogen-aggravated stress and mortality in low dose pesticide-exposed fish

The decline of freshwater fish biodiversity corroborates the trends of unsustainable pesticide usage and increase of disease incidence in the last few decades. Little is known about the role of nonlethal exposure to pesticide, which is not uncommon, and concurrent infection of opportunistic pathogens in species decline. Moreover, preventative measures based on current knowledge of stress biology and an emerging role for epigenetic (especially methylation) dysregulation in toxicity in fish are lacking. We herein report the protective role of lipotropes/methyl donors (like choline, betaine and lecithin) in eliciting primary (endocrine), secondary (cellular and hemato-immunological and histoarchitectural changes) and tertiary (whole animal) stress responses including mortality (50%) in pesticide-exposed (nonlethal dose) and pathogen-challenged fish. The relative survival with betaine and lecithin was 10 and 20 percent higher. This proof of cause-and-effect relation and physiological basis under simulated controlled conditions indicate that sustained stress even due to nonlethal exposure to single pollutant enhances pathogenic infectivity in already nutritionally-stressed fish, which may be a driver for freshwater aquatic species decline in nature. Dietary lipotropes can be used as one of the tools in resurrecting the aquatic species decline.

Effects of chronic carbosulfan exposure on liver antioxidant enzyme activities in rainbow trout

Catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and selenium-dependent glutathione peroxidase (Se-GPx) activities in liver of rainbow trout (Oncorhynchus mykiss; 116.88±21.69g) were evaluated after exposing fish to sublethal concentrations (25μg/L) of carbosulfan in flow-through tanks for 60 days. During the experiment activities of CAT, SOD, GST, and Se-GPx and histopathological effects were determined once a week and once at the end of the 21 days of recovery period. All enzymes were affected by carbosulfan when compared to control fish. Fish had intracellular oedema, cell necrosis, pycnotic nucleus, and increase of sinusoidal space in the liver. After 21 days of the recovery period, all enzyme activities had returned to control levels and fish had no histological lesions in liver. Therefore all the changes observed during exposure were reversible. Results indicate that the liver CAT, SOD and GST enzymes are highly sensitive to carbosulfan as their activities altered significantly, suggesting they could be useful in predicting sublethal pesticide toxicity and useful as an indicator for assessment of pesticides in contaminated water.

Assessment of the acute toxicity of the organochlorine pesticide endosulfan in Cichlasoma dimerus (Teleostei, Perciformes)

The organochlorine insecticide endosulfan (ES) is widely used despite its high toxicity to fish (96-h LC(50) median value of 2.6 μg L(-1)). This study aimed to assess the acute toxicity, histological and physiological parameters after exposure to 0; 0.25; 1; 2; 3; 4 and 16 μg L(-1) ES for 96 h under semi-static conditions in a freshwater perciform fish, Cichlasoma dimerus. Prior to death, fish exhibited behavior indicative of neurotoxicity. No difference was found in brain AChE activity. A decrease in erythrocyte mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration in exposed fish suggests a state of anemia. Histological alterations observed in exposed fish included hyperplasia of the interlamellar epithelium, blood congestion in secondary lamellae, and mucous cells hyperplasia and hypertrophy in gills; pycnotic nuclei and hydropic degeneration in liver; testicular damage. These moderate pathological responses in major organs could become crucial during reproduction and under prolonged exposure periods.

Endosulfan affects health variables in adult zebrafish (Danio rerio) and induces alterations in larvae development

Adult zebrafish (Danio rerio) were exposed to 0 (control), 0.16 or 0.48μg/L of the insecticide, endosulfan, for 28days. Haematology, whole body ions, thiobarbituric acid reactive substances (TBARS), Na(+)K(+)-ATPase, organ histology and reproduction were assessed in adults. The resulting offspring were examined for latent effects on development (heart rate and morphometrics). On day 14, adult fish exposed to 0.16μg/L endosulfan showed significantly lower red blood cell counts than those exposed to 0.48μg/L endosulfan; adult fish exposed to 0.16 ug/L also showed elevated TBARS compared to controls. Both concentrations of endosulfan caused a 4.0 fold increase in Na(+)K(+)-ATPase activity compared to controls (ANOVA, p<0.05). On day 14, the livers of fish exposed to endosulfan had fewer, enlarged hepatocytes, with cell diameters greater than the controls (ANOVA, p<0.05). Morphological alterations in the progeny of fish exposed to endosulfan were observed. Heart beat frequency was significantly lower in larvae from exposed adults to 0.16 μg/L compared to the control (ANOVA, p<0.05). These findings show that sublethal exposure to endosulfan causes adverse sublethal effects in adult D. rerio, and effects on the development of their offspring.

Assessment of acute toxicity and histopathology of the fungicide captan in rainbow trout

Acute toxicity of the fungicide, captan, to juvenile rainbow trout was evaluated under static-renewal test condition. Actual concentrations of captan ranged from 0.05 to 1.00 mg/L. The concentrations of captan that killed 50% of the rainbow trout (3.11±0.8 g) within 24 (24 h; LC(50)), 48, 72 and 96 h were 0.57±0.09, 0.49±0.10, 0.44±0.11 and 0.38±0.13 mg/L (95% confidence limits), respectively. None of the unexposed control fish died and the first fish died 6 h after exposure to captan (≥0.65 mg/L). Hypertrophy, separation of epithelium from lamellae, lamellar fusion, and epithelial cell necrosis were observed on captan exposed fish. Gills also had scattered areas of focal lamellar hyperplasia. Fish exposed to fungicide had inflammation and necrosis in liver, trunk kidney and spleen. In order, the most affected organs were gill, trunk kidney and liver.

Histopathological effects of cypermethrin on gill, liver and kidney of fresh water fish Clarias gariepinus (Burchell, 1822), and recovery after exposure

Gill, liver and kidney of Clarias gariepinus were examined histologically after exposure to sublethal concentrations (10.05, 20.10 and 30.15 microg/L) of cypermethrin for 10 days. Histological recovery was also studied by maintaining the pesticide-exposed fish in a fresh water system for an additional 10 days. Epithelial hypertrophy and hyperplasia, epithelial lifting, oedema, fusion of secondary lamellae, necrosis and desquamation were histopathological changes in the gills of fish exposed to cypermethrin. Hepatic lesions in the liver tissues of fish were characterized by cloudy swelling of hepatocytes, lipoid vacuoles, pycnotic nuclei and focal necrosis. Epithelial hypertrophy, narrowing of the tubular lumen, atrophy of the glomerulus, broader Bowman's capsule, necrosis in the epithelial cells and pycnosis in the hematopoietic tissue were observed in kidney tissues of fish. These lesions grew with increasing concentration. Although some of the changes were reversible, the rest were less pronounced after a recovery period; a period of 10 days was not long enough for complete recovery.

Histopathological changes in rainbow trout (Oncorhynchus mykiss) after exposure to sublethal composite nitrogen fertilizers

Subchronic toxicity of composite inorganic fertilizers such as ammonium sulfate [fertilizer A; (NH(4))(2)SO(4); 21% NH(4)-N)], composite fertilizer 15-15-15 (fertilizer B; commercial formulation: 15% NH(4)-N, 15% phosphorus, and 15% potassium oxide), and composite fertilizer 25-5-10 (fertilizer C; commercial formulation: 25% NH(4)-N, 5% phosphorus, and 10% potassium oxide) on the skin, liver, kidney, pancreas, and gills of the juvenile rainbow trout (Oncorhynchus mykiss) was studied in two-week toxicity tests under static-renewal test conditions. Fish exposed to sublethal concentrations of fertilizers did not show any behavioral abnormality compared to control groups. Histological lesions were observed in skin, gills, liver, pancreas, and trunk kidney of the fish. In the epidermis, degenerated/vacuolated epithelial cells, microcystic dilatations, and intracellular edema of mucus cell were observed. Liver had swollen and degenerated hepatocytes without losing adenoid structure. Hematopoietic tissues had necrosis and vacuolar degeneration on proximal tubules of the kidney. In order, the most affected organs were skin, liver, and kidney.

Sublethal cyfluthrin toxicity to carp (Cyprinus carpio L.) fingerlings: biochemical, hematological, histopathological alterations

This study measures a whole series of biological endpoints, and histopathological and behavioral changes of carp (Cyprinus carpio L.) fingerlings in order to investigate the adverse effects of a sublethal concentration of 10 microg/L cyfluthrin for 48h and one week using the semi-static test system. The most significantly altered findings of this study was that total antioxidant status levels decreased in 48h, chloride levels decreased in one week, and sodium and phosphorous levels increased in the 48h-exposed group. Plasma cortisol increased in both the 48h-exposed and the one-week-exposed groups. The unique tissue was the brain that had an increased level of malondialdehyde after one week of exposure. Such biomarkers may be used in assessing adverse/toxic effects of pesticides as environmental stressors. Potential oxidative-stress-inducing effect of synthetic pyrethroid cyfluthrin, as lipid peroxidation, in addition to its sodium channel blocking, is reported for the first time as an additional mechanism of action.