Histopathological biomarkers in estuarine fish species for the assessment of biological effects of contaminants

Ecotoxicological mechanism of glyphosate on Moerella iridescens: Evidence from enzyme, histology and metabolome

This study aimed to elucidate the regulatory mechanisms underlying the toxic effects of glyphosate (GLY) on rainbow clam (M. iridescens), with implications for their culture and conservation. GLY residues in aquatic systems raise significant environmental and public health concerns, yet the underlying mechanisms remain largely elusive. In this study, M. iridescens were acutely exposed to GLY at various concentrations (0, 2.34, 5.45, 12.74, 29.74, and 69.46 mg/L) for 7 days. Gill and hepatopancreas samples were collected to assess oxidative stress status and histopathological examination. Additionally, three concentration groups low concentration (LC) group at 2.34 mg/L, medium concentration (MC) group at 12.74 mg/L, and high concentration (HC) group at 69.46 mg/L were selected for metabolomic analysis. The findings indicated that GLY exposure led to oxidative stress and structural changes in tissues. The metabolomic analysis suggested that GLY exposure exacerbates inflammatory responses and disrupts endocrine function, and sex hormones.

Short-term in situ Exposure of Guinean Tilapia and Blue Crab Near a Sawmill Wastes-impacted Coastal Ecosystem Reveal Significant Oxidative Stress Effects

Coastal ecosystems are characterized by various human activities with potential adverse impacts. This study aimed to evaluate the potential oxidative stress effects in representative aquatic biota deployed in situ at a sawmill wastes dump (test site) and reference site in a coastal ecosystem for a short term (28 days) period. PAHs and OCPs were analysed using GC-FID and GC-MS respectively in surface water and sediments. Oxidative stress indices (malondialdehyde, glutathione-s-transferase, reduced glutathione, catalase and superoxide dismutase) were evaluated following standard methods in Coptodon guineensis (Guinean Tilapia) and Callinectes amnicola (Blue crab) over a period of 28 days. Sum PAHs in the test site sediments, oxidative stress indices in C. guineensis liver and C. amnicola haemolymph after 28 days exposure were significantly higher (p < 0.0.5) compared to the reference site. The results showed the adverse impacts to biota of sawmill wastes which are continuously burnt at the test site with potential for long-term effects. Sustainable sawmill wastes management at the test site are recommended to sustain life below water (UNSDG 14).

Effect of Metaldehyde on Survival, Enzyme Activities, and Histopathology of the Apple Snail Pomacea canaliculata (Lamarck 1822)

Pomacea canaliculata, as an invasive exotic species in Asia, can adversely affect crop yields, eco-environment, and human health. Application of molluscicides containing metaldehyde is one effective method for controlling P. canaliculata. In order to investigate the effects of metaldehyde on adult snails, we conducted acute toxicological experiments to investigate the changes in enzyme activities and histopathology after 24 h and 48 h of metaldehyde action. The results showed that the median lethal concentrations (LC) of metaldehyde on P. canaliculata were 3.792, 2.195, 1.833, and 1.706 mg/L at exposure times of 24, 48, 72, and 96 h, respectively. Treatment and time significantly affected acetylcholinesterase (AChE), glutathione S-transferase (GST), and total antioxidant capacity (TAC) activity, with sex significantly affecting AChE, GST, and TAC activity and time significantly affecting carboxylesterase (CarE). In addition, the interaction of treatment and time significantly affected the activity of GST, CarE and TAC. In addition, histopathological changes occurred in the digestive glands, gills and gastropods of apple snail exposed to metaldehyde. Histological examination of the digestive glands included atrophy of the digestive cells, widening of the hemolymph gap, and an increase in basophils. In treated snails, the hemolymph gap in the gills was widely dilated, the columnar cells were disorganized or even necrotic, and the columnar muscle cells in the ventral foot were loosely arranged and the muscle fibers reduced. The findings of this study can provide some references for controlling the toxicity mechanism of invasive species.

Histopathological Evaluation of the Curative Effects of EDTA on Lymnaea stagnalis Exposed to Subacute Cadmium

We investigated the therapeutic effects of EDTA application for 14 and 28 days on cadmium (Cd) induced pond snail Lymnaea stagnalis (Linnaeus, 1758). The sublethal concentration of cadmium (63.4 mg/l Cd) caused tissue damages to the snail after an exposure for 28 days.In the groups treated with EDTA, the concentration of Cd in the foot, mantle and hepatopancreas tissues showed significantly decreased during the recovery period. The curative effects of EDTA on Cd-induced damage were assessed using a scoring system. Cadmium exposure led to histopathological changes including increased mucositis, pigment and protein cells, foot epithelium desquamation, muscle fibril damage, connective tissue cell atrophy, and increased lipid vacuoles in the mantle and hepatopancreas. However, these changes were less severe in snails treated with EDTA (2.00 mL/L for 28 day), indicating that EDTA reduces their susceptibility to heavy metal toxicity.

Coping with current impacts: The case of Scyliorhinus canicula in the NW Mediterranean Sea and implications for human consumption

The small-spotted catshark (Scyliorhinus canicula) is a bottom-dwelling elasmobranch that represents the most discarded catch in terms of biomass in the Catalan coast (NW Mediterranean). Potential impacts affecting its population and food safety implications have been assessed in three localities along the Catalan coast. Distinct indicators were integrated, such as biological data, ingested anthropogenic items (plastic and cellulose-like items), parasitological indices, trace metal concentrations and histopathology using liver as target organ. Although high ingestion rates of fibres and levels of some heavy metals, they do not seem negatively affected by any major pathology nor by the current levels of pollutants. Small-scale differences among localities and depths were found and discussed. No zoonotic parasites were found. Encysted larvae of Grillotia adenoplusia and, above all, the levels of Hg found in the musculature, that are well over the European Commission limits, rise concerns regarding human consumption of S. canicula in this region.

Multiple biomarkers in pufferfish as a proxy of environmental health in brazilian marine protected areas

Marine Protected Areas (MPAs) are designed to conserve biodiversity and vulnerable ecosystems. This study aimed to assess the environmental quality of three Brazilian MPAs, based on the integrated analysis of biomarkers in pufferfish. The MPAs are differentiated by the degree of anthropogenic influences. The Barra do Una Estuary sustainable reserve (JUR) is a reference area due to its low levels of contamination and species diversity. The Cananéia Estuarine System (CAN) has been recognized as a biosphere reserve by UNESCO, as well as a Ramsar wetland. This MPA was influenced by upstream mining activities, resulting in the introduction of metals in the estuarine waters and the discharge of untreated urban sewage. The São Vicente estuary (SSV) lacks proper sanitation infrastructure. All collections were conducted during winter season, and, after collection, the animals were euthanized, their soft tissues were removed, and multiple biomarkers were analyzed in the gills and liver, as biometric, genotoxic, biochemical, and morphological. A one-factor multivariate analysis was applied to evaluate the differences between the data sets, and the matrices were analyzed using PERMANOVA to evaluate the "estuary" factor. The results were integrated using PCA with a 0.4 cut value and an Enhanced Integrated Biomarker Response (EIBR) was calculated. PCA was correlated with biochemical, genotoxic, and morphological biomarkers. In general, SVV differed from CAN and JUR as shown by both univariate and multivariate analyses. SVV also showed the highest EIBR, followed by CAN. Organisms from SSV showed greater gill pathology, elevated AChE activity and lipoperoxidation (LPO), and micronuclei frequency. CAN present intermediate EIBR, with severe pathologies in the liver. CAN seems to present an intermediate environmental quality between SSV and JUR indicating the importance of the existence of MPAs for environmental conservation and the need to monitor such areas, to maintain their suitable environmental quality.

Differences on the level of hepatic transcriptome between two flatfish species in response to liver cancer and environmental pollution levels

Environmental factors can cause cancer in both wild animals and humans. In ecological settings, genetic variation and natural selection can sometimes produce resilience to the negative impacts of environmental change. An increase in oncogenic substances in natural habitats has therefore, unintentionally, created opportunities for using polluted habitats to study cancer defence mechanisms. The Baltic and North Sea are among the most contaminated marine areas, with a long history of pollution. Two flatfish species (flounder, Platichthys flesus and dab, Limanda limanda) are used as ecotoxicological indicator species due to pollution-induced liver cancer. Cancer is more prevalent in dab, suggesting species-specific differences in vulnerability and/or defence mechanisms. We conducted gene expression analyses for 30 flatfishes. We characterize between- and within-species patterns in potential cancer-related mechanisms. By comparing cancerous and healthy fishes, and non-cancerous fishes from clean and polluted sites, we suggest also genes and related physiological mechanisms that could contribute to a higher resistance to pollution-induced cancer in flounders. We discovered changes in transcriptome related to elevated pollutant metabolism, alongside greater tumour suppression mechanisms in the liver tissue of flounders compared to dabs. This suggests either hormetic upregulation of tumour suppression or a stronger natural selection pressure for higher cancer resistance for flounders in polluted environment. Based on gene expression patterns seen in cancerous and healthy fish, for liver cancer to develop in flounders, genetic defence mechanisms need to be suppressed, while in dabs, analogous process is weak or absent. We conclude that wild species could offer novel insights and ideas for understanding the nature and evolution of natural cancer defence mechanisms.

Correlations between oxidative DNA damage and formation of hepatic tumours in two flatfish species from contaminated environments

Many species in aquatic environments face increased exposure to oncogenic pollution due to anthropogenic environmental change which can lead to higher cancer prevalence. The mechanistic relationship connecting environmental pollution and cancer is multi-factorial and poorly understood, and the specific mechanisms are so far still uncharacterized. One potential mediator between pollutant exposure and cancer is oxidative damage to DNA. We conducted a study in the field with two flatfish species, European flounder (Platichthys flesus L.) and common dab (Limanda limanda L.) with overlapping distribution and similar ecological niche, to investigate if the link between oncogenic pollutants and cancer described in ecotoxicological literature could be mediated by oxidative DNA damage. This was not the case for flounders as neither polycyclic aromatic hydrocarbon (PAH) bile metabolites nor metallic trace element concentrations were related to oxidative DNA damage measurements. However, dabs with higher PAH concentrations did exhibit increased oxidative damage. High oxidative DNA damage also did not predict neoplasm occurrence, rather, healthy individuals tended to have higher oxidative damage measurements compared to fishes with pre-neoplastic tumours. Our analyses showed that flounders had lower concentrations of PAH bile metabolites, suggesting that compared to dab this species is less exposed or better at eliminating these contaminants.

Co-exposure to arsenic and fluoride to explore the interactive effect on oxidative stress and autophagy in myocardial tissue and cell

Co-contamination of arsenic and fluoride is widely distributed in groundwater. However, little is known about the interactively influence of arsenic and fluoride, especially the combined mechanism in cardiotoxicity. Cellular and animal models exposure to arsenic and fluoride were established to assess the oxidative stress and autophagy mechanism of cardiotoxic damage using the factorial design, a widely used statistical method for assessing two factor interventions. In vivo, combined exposure to high arsenic (50 mg/L) and high fluoride (100 mg/L) induced myocardial injury. The damage is accompanied by accumulation of myocardial enzyme, mitochondrial disorder, and excessive oxidative stress. Further experiment identified that arsenic and fluoride induced the accumulation of autophagosome and increased expression level of autophagy related genes during the cardiotoxicity process. These findings were further demonstrated through the in vitro model of arsenic and fluoride-treated the H9c2 cells. Additionally, combined of arsenic-fluoride exposure possesses the interactively influence on oxidative stress and autophagy, contributing to the myocardial cell toxicity. In conclusion, our data suggest that oxidative stress and autophagy are involved in the process of cardiotoxic injury, and that these indicators showed interaction effect in response to the combined exposure of arsenic and fluoride.

Assessing metal(loid)s concentrations and biomarkers in tilapia (Oreochromis niloticus) and largemouth bass (Micropterus salmoides) of three ecosystems of the Yaqui River Basin, Mexico

Aquatic ecosystems have been suffering deleterious effects due to the development of different economic activities. Metal(loid)s are one of the most persistent chemicals in environmental reservoirs, and may produce adverse effects on different organisms. Since fishes have been largely used in studies of metal(loid)s exposure, tilapia and largemouth bass were collected in three ecosystems from the Yaqui River Basin to measure the concentrations of metal(loid)s (chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn) arsenic (As), mercury (Hg), and selenium (Se)) and some biomarkers (somatic indices, metallothionein expression and histopathological analysis) in tissues of both species. Metal(loid) concentrations varied seasonally among ecosystems in tissues of both species. The elements varied seasonally and spatially in tissues of both species, with a general distribution of liver > gills > gonads. Also, biomarkers showed variations indicative that the fish species were exposed to different environmental stressor conditions. The highest values of some biomarkers were in largemouth bass, possibly due to differences in their biological characteristics, mainly feeding habits. The multivariate analysis showed positive associations between metal(loid)s and biomarkers, which are usually associated to the use of these elements in metabolic and/or regulatory physiological processes. Both fish species presented histological damage at different levels, from SI types (changes that are reversible for organ structure) to SII types (changes that are more severe but may be repairable). Taken together, the results from this study suggest that the Yaqui River Basin is moderately impacted by metals and metalloids.

Review of ecologically relevant in vitro bioassays to supplement current in vivo tests for whole effluent toxicity testing - Part 2: Non-apical endpoints

Whole effluent toxicity (WET) testing uses whole animal exposures to assess the toxicity of complex mixtures, like wastewater. These assessments typically include four apical endpoints: mortality, growth, development, and reproduction. In the last decade, there has been a shift to alternative methods that align with the 3Rs to replace, reduce, and refine the use of animals in research. In vitro bioassays can provide a cost-effective, high-throughput, ethical alternative to in vivo assays. In addition, they can potentially include additional, more sensitive, environmentally relevant endpoints than traditional toxicity tests. However, the ecological relevance of these endpoints must be established before they are adopted into regulatory frameworks. This is Part 2 of a two-part review that aims to identify in vitro bioassays that are linked to ecologically relevant endpoints that could be included in WET testing. Part 2 of this review focuses on non-apical endpoints that should be incorporated into WET testing. In addition to the four apical endpoints addressed in Part 1, this review identified seven additional toxic outcomes: endocrine disruption, xenobiotic metabolism, carcinogenicity, oxidative stress, inflammation, immunotoxicity and neurotoxicity. For each, the response at the molecular or cellular level measured in vitro was linked to the response at the organism level through a toxicity pathway. Literature from 2015 to 2020 was used to identify suitable bioassays that could be incorporated into WET testing.

Assessment of the health status of the European anchovy (Engraulis encrasicolus) in the NW Mediterranean Sea from an interdisciplinary approach and implications for food safety

The European anchovy (Engraulis encrasicolus) is a small pelagic fish with an outstanding commercial value supporting important fisheries and is a key component of pelagic ecosystems in the Mediterranean Sea. Progressive reductions in the population size of this species has been observed in the Mediterranean Sea during recent decades, accompanied by a decline in the body condition, as well as the size/age of maturation. Nonetheless, the health status has not been yet assessed using a holistic approach. Herein, we analyse the health status of the European anchovy, integrating distinct indicators from fish condition, enzymatic biomarkers, presence of tissue alterations, and parasite descriptors. In addition, we analyse the presence of anthropogenic items (AIs) in the digestive tract of fish and their potential impact on health status. Additionally, we assess the differences between current AIs values and those recorded over 12 years ago. None of the health indicators studied provided evidence of relevant pathologic conditions affecting this fish species in the studied area. However, changes in the pattern of liver parenchyma were found. Compared with anchovy populations from other distribution areas, no zoonotic parasites were recorded in this study, demonstrating a reduced risks associated with foodborne transmission to humans. AIs, such as fibres and plastic particles, were found in the digestive tract of half of the fish analysed. A significant increase was detected in AIs prevalence between 2007 (40 %) and 2019 (70 %), alongside differences in the abundance and typology of the AIs, though this does not seem to have impacted fish health yet. Therefore, our work underscores the importance of implementing a regular program to monitor the health status of this key species to better understand population dynamics and their drivers.

Heavy metals and parasitological infection associated with oxidative stress and histopathological alteration in the Clarias gariepinus

The goal of this study was to assess the harmful effects of heavy metal accumulation on Clarias gariepinus (catfish) in two different polluted areas in the Al Sharkia governorate and assess the impact on oxidative stress and histological changes. The results revealed a highly significant difference in heavy metal levels in the water and inside fish tissues (liver and gonads) between the two sites. The total prevalence of parasitic infection was at the highest percentage in area B, in addition to severe histopathological damage to the liver and the gonads. Findings show that the total prevalence of parasitic infection is associated with uptake of metals, depleted antioxidant activity, and incidence of lipid peroxidation in tissue.

Histological biomarkers and biometric data on trahira Hoplias malabaricus (Pisces, Characiformes, Erythrinidae): a bioindicator species in the Mearim river, Brazilian Amazon

The objective of this study was to evaluate the levels of environmental contamination in a protected area in the Brazilian Amazon. For this, two areas were chosen along the Mearim River: the reference area (A1) and the potentially contaminated area (A2), where water samples were collected, for physicochemical and microbiological analyses, as well as specimens of Hoplias malabaricus, for the evaluation of biometric data and incidence of branchial lesions. The physicochemical analyzes of the water from both areas showed contamination (low levels of dissolved oxygen, tubidity and high iron concentrations, especially in A2). The microbiological analyzes showed that all water samples showed total coliform values higher than those acceptable by CONAMA and WHO (with higher values in A2), in addition to E. coli values higher than those allowed by legislation in A2. Regarding biometric data, male and female fishes were significantly longer and heavier in A1 during the dry and rain seasons and the gonadosomatic index also showed higher values in A1 than in A2 in both seasons. H. malabaricus showed gill lesions of minimal to moderate pathological importance in A1 and A2, indicating that specimens from both areas of the Mearim River showed biological responses to contamination. The observed changes in the water quality, bimetic parameters and the histological analyzes of the specimens of H. malabaricus directly reflect on the quality and health of the fishes in the Mearim River, and point to the urgent need for prevention and remediation of contamination in these ecosystems.

Multi-biomarker Assessment in a Native Species Psalidodon eigenmanniorum Under Inorganic Mercury and Recovery Scenarios

The increasing contamination of water bodies with mercury raises concerns about its possible effects on aquatic organisms. The combined use of several biomarkers allows researchers to study the impact of a chemical at different levels of biological organization. In the present work, we determined the response of histological (gills and liver), somatic (condition factor and hepato-somatic index), and behavioral (predator-prey relationship, through the presentation of a computer-animated image) biomarkers in the native species Psalidodon eigenmanniorum exposed to 100 µg L^-1 of inorganic Hg (IHg) during 96 h. We also assessed whether there was a change in the biomarkers analyzed after 7 days in Hg-free water compared with those exposed to IHg. In exposed fish, IHg caused damage to the gills and liver tissues. The condition factor showed no difference between IHg-exposed organisms and control organisms, while the hepato-somatic index was lower in IHg-exposed fish. As for the behavioral analyses, it was observed that the presentation of a stimulus induced changes in the behavioral responses of fish exposed to IHg, which showed a heightened state of alertness with respect to control. On the other hand, after 7 days in Hg-free water, the organisms generally showed no changes in biomarkers compared with IHg-exposed fish. Our results contribute new data on IHg toxicity in a native species and provide information on the plasticity of damage to reverse itself. Furthermore, this work provides baseline information for environmental assessments in water bodies where mercury is present.

In vivo appraisal of oxidative stress response, cell ultrastructural aberration and accumulation in Juvenile Scylla serrata exposed to uranium

In vivo studies were performed to evaluate the organ specific tissue accumulation and cellular toxicity of uranium to mud crab Scylla serrata. The specimens were acclimated in natural seawater and the exposure to 50-250 μg/L uranium was investigated up to 60 days. The present study examined the effects of concentration and duration of uranium exposure in the tissue of S. serrata at cellular and subcellular level using scanning electron microscopy and bright field transmission electron microscopy in addition to histological analysis. The results indicated that accumulation of U in S. serrata was organ specific and followed the order gills > hepatopancreas > muscle. The response of key antioxidant enzyme activities such as SOD, GPx and CAT in different organs of crabs indicated oxidative stress due to U in the ambient medium and tissue. At 50 and 100 μg/L of U exposure, individuals were able to acclimate the oxidative stress and withstand the uranium exposure. This acclimation could not be sustained at higher concentrations (250 μg/L), affecting the production of CAT in the tissues. Cellular and subcellular changes were observed in the hemocytes with reduction in their number in consonance with the antioxidant enzymes. Histological aberrations like lamellar disruption of gill, necrosis of hepatopancreas, disruption and rupture of muscle bundles were observed at different concentrations and were severe at higher concentration (250 μg/L). Necrosis was observed in the electron micrographs of tissues shortly after 15 days of exposure. SEM micrograph clearly shows disrupted lamellae, folding of marginal canal and reduction of inter lamellar spaces in the gills of crab exposed to high concentration of uranium. Mitochondrial anomalies are reported for the first time in the present study in addition to the subcellular changes and vacuoles on exposure uranium in the cells of gill and hepatopancreas.

Univariate or multivariate approaches for histopathological biomarkers in the context of environmental quality assessments?

Although the simplification of multivariate histopathological data into univariate indices can be useful for the assessment of environmental quality, this implies a great loss of information. The objective of the present study was to evaluate the effectiveness, in the context of environmental quality assessment, of an approach that integrates individual histopathological responses in a discriminated manner with the results of contaminants by means of multivariate analyses. This analysis was compared to the diagnosis of environmental quality provided by the use of the univariate Bernet histopathological index. Contaminant loads (sediments and fish) and the liver histopathology of Cathorops spixii were integrated through multivariate analysis. Integrated individual histopathological responses allowed classifying environmental quality from more to less impacted sites, while the univariate index showed some inconsistencies with chemical loads and allowed identifying only the most impacted site.

Biological responses of whitefish (Coregonus lavaretus L.) to reduced toxic impact: Metal accumulation, haematological, immunological, and histopathological alterations

Bioaccumulation of the main pollutants in the organs of whitefish, as well as their haematological parameters, were examined dynamically over a 40-year period in historically contaminated Lake Imandra. A quantitative histological analysis was performed to assess the physiological state of whitefish and histopathologies of organs, as well as their physiological and biochemical functions in the current period of toxic load decline. Biological reactions of whitefish from the historically contaminated area have been greatly modified in contrast to those of whitefish from the never contaminated area of the lake, and this shift persisted even after approximately 20 years of toxic load decline. First, high antioxidant status supports the body's systems, smoothing over the negative consequences of metal toxicity, phagocytosis and inflammatory reactions. Moreover, the defence mechanism of whitefish from the historically contaminated area actively uses the oxidative systems of nonspecific immunity. Second, the adaptive strategy is aimed at improving gas exchange without compensatory proliferation of gill structure, which increases their functional surface and reduces the distance to the bloodstream, as well as increasing haemoglobin in maturing erythrocytes. Third, the higher efficiency of endo- and phagocytosis was confirmed by detecting increased monocytes and macrophages in the peripheral blood and decreased melano-macrophage centres in the fish kidney. Elevated accumulation of Fe, Cu, and Se may serve a sign of liver pathology, while elevated accumulation of Zn and Co already indicates kidney pathology, which is confirmed by histopathological alterations.

Chemical pollution impairs the health of fish species and fishery activities along the Algeria coastline, Mediterranean Sea

Chronic exposure to multiple pollutants affects aquatic organisms, even at low concentrations, and can impair fishery activities along marine coastlines. The bioavailability of toxic metals and the presence of metals and polycyclic aromatic hydrocarbons (PAHs) in both water and sediment can explain the worst-case scenario of fish health and fishery production decline along the Algeria coastline. The hepatosomatic index (HIS), gonadosomatic index (GSI), and condition factor (K) in the studied species from the Algiers, Bou Ismail, and Zemmouri bays are the first indicators of the poor environmental health along the studied region. These findings could be explained by the bioavailability of Zn, Cu, Cr, Mn, Hg, and Ni and the detection of PAHs in the water and sediment of these bays. Additionally, histopathological damage in the liver is described in sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus), and sardinelle (Sardinella aurita) highlights the current study in the investigation of the risk of exposure to biota or human populations. The occurrence of permanent lesions in the livers of fish impairs organ function and increases the incidence of diseases affecting the fish community. Furthermore, the factor analysis with principal component analysis (FA/PCA) dataset explains the physiological disturbances described in all studied species. These findings revealed that Zemmouri bay is the most affected by chemicals, suggesting that S. pilchardus is the most sensitive species. Finally, the results showed that the bioavailability of chemicals present in the studied bays confirms poor water quality, which can explain the decrease in fishery production along the Algerian Coastline.

Study of Ultrastructural Abnormalities in the Renal Cells of Cyprinus carpio Induced by Toxicants

Transmission Electron Microscopic (TEM) assessments were performed on the renal cells of common carp Cyprinus carpio to observe the deleterious effects of two organophosphate insecticides, Phorate and Dimethoate. Pesticides such as Phorate and Dimethoate often pollute aquatic systems where they may negatively impact fish, but so far, the ultrastructural toxicity of these pesticides remains poorly understood. Here, we use Transmission Electron Microscopy (TEM) to determine how acute exposure to sublethal concentrations of these two pesticides may affect the renal cells of common carp Cyprinus carpio. For each insecticide, the fish were divided in four experimental conditions: a control and three different exposure concentrations of the pesticide. The Phorate treated fish were exposed to three sublethal concentrations of 0.2 mg/L, 0.4 mg/L, 0.6 mg/L for a duration of 24, 48 & 72 h. The dimethoate treated fish were exposed to three sublethal concentrations of 0.005 mL/L, 0.01 mL/L, 0.015 mL/L for a duration of 24, 48 and 72 h. The two-dimensional transmission electron microscopy revealed ultrastructural abnormalities in the treated fish renal cells when exposed to two toxicants including deformation in the glomerulus, vacuolization of cytoplasm, degenerative nucleus and damaged mitochondria. Furthermore, the ultrastructural abnormalities were more prominent with the increase in the concentrations of both the insecticides and also with their exposure period. Overall, these results provide important baseline data on the ultrastructural toxicity of Phorate and Dimethoate and will allow important follow-up studies to further elucidate the underlying cellular mechanisms of pesticide toxicity in wildlife.

In vivo genotoxic effects of commercial grade cypermethrin on fish peripheral erythrocytes

The study explicates the genotoxic effects of commercial grade cypermethrin on peripheral erythrocytes of Catla catla, chronically exposed to two environmentally relevant concentrations. The fish was treated with sub-lethal concentrations 0.12 μg/L and 0.41 μg/L (1/10th and /1/3rd of 96 h LC₅₀ ) of cypermethrin for 45 days. DNA damage in the exposed fish was assessed using alkaline comet assay, presence of micronuclei (MN), erythrocyte nuclear and cytoplasmic abnormalities. Exposure to cypermethrin induced a dose-dependent increase in percent DNA damage, micronucleus frequency and erythrocyte abnormalities. Nuclear anomalies such as notched nuclei, lobed nuclei, bridged nuclei, and deformed nuclei; and cytoplasmic anomalies like anisochromasia, vacuolated cytoplasm, lobed cells, and echinocytes were observed. The findings revealed the genotoxic potential of commercial formulations pyrethroid cypermethrin at concentrations found in the environment and their potential deleterious effects on nontarget aquatic organisms.

Impact assessment of a large river on the sediments and fish from its continental shelf: using Solea solea as sentinel in the Ebro river mouth (NW Mediterranean, Spain)

Many studies have been carried out along mighty rivers with heavily industrialized watersheds to evaluate pollutants and their effects on freshwater organisms. However, their impact on marine organisms is virtually unknown. In order to cover this gap, Solea solea, one of the most important commercial fish species, together with sediments, were sampled during 2013-2015 offshore from the Ebro Delta river mouth. Fish health indicators (condition indices, histological tissue alterations, and parasite descriptors) were used to assess the potential effect of pollutants, an issue of particular interest in the area following the dredging activities taking place in the river upstream in 2013. No major histopathological alterations were detected, but perivascular inflammatory foci (PIF) were frequently observed, especially in 2014. The most prevalent and abundant parasites were acanthocephalans and digeneans within the digestive tract and copepods on the gills. Levels of trace metals from sediments and fish muscle were below the effects range median and reference levels accepted for human consumption, respectively. However, the lower levels of the hepatosomatic index, higher numbers of PIF, and variations in the abundance of parasites in 2014 and 2015 could suggest a pollutant exposure during these years. These results warn signs of toxicity, which could be associated with sediment leaks during the dredging activities.

Hepatic nodular alterations in wild fish from a hyper-eutrophic freshwater system with cyanobacterial blooms: a species and seasonal comparison

This paper reports on the seasonal and species comparison of hepatic nodular alterations in two indicator fish species from the hyper-eutrophic Roodeplaat Dam in South Africa. This freshwater system is characterized by seasonal cyanobacterial algal blooms which release bio-toxins, including hepato-toxins, which can have negative effects on the health of the resident fish population. A total of 115 Clarias gariepinus (Burchell) and 98 Oreochromis mossambicus (Peters) were collected seasonally across six different surveys over a period of 3 years. Nodular alterations in livers were assessed both macroscopically and microscopically. We found a species difference with a 48% prevalence of nodular alterations in C. gariepinus and no macroscopically visible alterations in O. mossambicus. Affected fish also showed an increase in the ratio of liver mass to body mass, i.e., the hepatosomatic index. The microscopic characteristics of the nodules were primarily associated with pre-neoplastic, focal areas of cellular alterations; most prevalent were focal areas of steatosis. However, we could not establish a seasonal pattern regarding the occurrence of these alterations and therefore no association between the occurrence of the liver pathology and the cyanobacterial blooms. Our results therefore suggest that the occurrence of nodular alterations is not an acute, seasonal response, but rather a chronic, and possibly, and more interestingly, a species-specific, pathological response.

2, 3-Dimethylsuccinic acid and fulvic acid attenuate lead-induced oxidative misbalance in brain tissues of Nile tilapia Oreochromis niloticus

Lead has long been known as neurotoxic and immunotoxic heavy metal in human and animals including fish, whereas, 2, 3-dimethylsuccinic acid (DMSA) and fulvic acid (FA) are well-known biological chelators. The present investigation was carried out to assess the potential chelating and antioxidant effects of dietary supplementation with DMSA and FA against lead acetate (Pb)-induced oxidative stress in Nile tilapia, O. niloticus. One-hundred and eighty apparently healthy O. niloticus fish (30 ± 2.5 g) were allocated into six equal groups. The first group was fed on basal diet and served as control, while the second group was fed on DMSA-supplemented basal diets at levels of 30 mg/kg diet; the third group was fed on FA-supplemented basal diet at level of 0.3 mg/kg diet; the forth, fifths, and sixth groups were exposed to 14.4 mg Pb /L water (1/10 LC50) and feed on basal diet only, basal diet supplemented with DMSA (0.3 mg/kg diet), or basal diet supplemented with FA (0.3 mg/kg diet), respectively. Antioxidant and lipid peroxidative status, activity of glucose 6-phosphate dehydrogenase (G6PD), and lactate dehydrogenase (LDH) as well as the histopathologic findings were evaluated in brain tissues, while the Pb residues were evaluated in liver, muscles, and brain tissues. The results of the present study showed that DMSA and FA decreased malondialdehyde (MDA) and Pb residue in tissues of Pb-exposed fish and improved the histologic picture and brain contents of glutathione (GSH), glutathione-s-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), G6PD, LDH, and total antioxidant capacity (TAC). It could be concluded that DMSA and FA supplementation exhibited potential neuroprotective effect against Pb-induced oxidative brain damages in O. niloticus through improvement of antioxidant status of the brain tissue.

Investigation of the impact caused by different sizes of polyethylene plastics (nano, micro, and macro) in common carp juveniles, Cyprinus carpio L., using multi-biomarkers

Plastic pollution poses a global threat to aquatic organisms, yet its effect on many species remains poorly documented and understood. This study addresses the impact caused by different sizes of polyethylene (PE) plastics on the common carp and evaluates their multi-biomarkers response. We investigated the histological structure and measurement of biochemical alterations, antioxidant enzymes, immunological responses, and fluctuations in blood profiles of the organisms after 15 days of exposure to a concentration of 100 mg/L of nano- (NPs), micro- (MPs) and macroplastics (MaPs). The fish health status was altered in the sole presence of PE particles. All biomarkers changed after exposure compared to the control group, with larger changes being observed with the decreasing size of particles (NPs > MPs > MaPs) compared to their absence. A synergistic effect resulting from the individual impact of plastics penetration in the circulatory system, bursting biochemical responses, and lesions in tissues, might explain the more considerable impact of NPs compared to MPs and/or MaPs.

Diversification of Dawkinsia filamentosa (Valenciennes, 1844) and their growth conditions by the impact of toxic metals in the river Tamiraparani

The concentration of toxic metals in water, sediment, and organs of species Dawkinsia filamentosa and its growth conditions were analyzed from the Tamiraparani river of Tamilnadu, India. The water quality preferred to examine the existence of metals, and the concentration of Pb, Cr and Cd expand the first time were found to be high in sediment, which was followed by water and the organs of the fish gill and liver. Even though, intakes of the toxic metals were highly accumulated in the gill instead of the liver. From that, the histological assessments of organ damages were observed significant variations in the study sites. Within the linear regression parameters for length-weight relationships of coefficient value r², 'a' value and 'b' value were showed the allometric growth rate and condition factor of 'K' was fittest. The phylogenetic tree analyses were showing analogy between the opposite groups of Clade III and Clade II showed that the species were closely correlated with the Puntius sp. of other species. And in Clade I was intimately related within the identical population of D. filamentosa as respectively. However, the comparison of metal concentrations of other Indian rivers and of other parts of the world specified that these metals are getting closer to the standard permissible limits. Altogether, the potential ecological risk factor was slightly increased at the sampling sites; therefore, we conclude that the metal contents might pollute the river. Throughout this research, the observed findings emphasize that fish species from the riverine ecosystem may useful for environmental management and genetic diversity.

Biological responses and toxicopathic effects elicited in Solea senegalensis juveniles by waterborne exposure to benzo[a]pyrene

Polycyclic aromatic hydrocarbons (PAHs) are priority contaminants in coastal and estuarine ecosystems under anthropogenic pressure. Although PAHs tend to accumulate in the sediment, toxicity for benthic flat fish such as soles may be caused by PAHs released from the sediment to the water column. Within this context, the present investigation aims at recognizing toxicopathic effects elicited after waterborne exposure to benzo[a]pyrene B[a]P, a model individual PAH compound, in juvenile Solea senegalensis. Sole juveniles were exposed to various concentrations of waterborne B[a]P for 3 and 7 days. Brain, liver, gills and gonad were the target tissues selected to determine biochemical and lysosomal biomarkers, and histopathology. Biological responses and toxicopathic effects were consistent with B[a]P concentration and exposure time. From day 3, hepatic catalase inhibition indicated potential oxidative effects of B[a]P. At day 7, contaminant exposure produced hepatic glutathione-S-transferase induction at low concentrations and inhibition at higher levels, evidencing a bell-shaped response. A clear gradient in lysosomal membrane destabilisation was observed in relation with B[a]P concentrations. Histopathological lesions were more frequent at day 7 and at higher contaminant levels. It seems that environmentally relevant waterborne concentrations of B[a]P (1000 ng/l) would suffice to cause toxicopathic effects on sole juveniles in relatively short exposure times. In agreement, the Integrative Biological Response index (IBR/n) indicated a dose-dependent decline in health condition upon exposure to B[a]P (IBR/n_HighB[a]P > IBR/n_MidB[a]P > IBR/n_LowB[a]P > IBR/n_DMSO > IBR/n_Control). Overall, changes in antioxidant enzymes activity, lysosomal biomarkers and gill and liver histopathology are responsive early-warning signs of health disturbance in sole juveniles exposed to waterborne PAHs.

Biological and anthropogenic influences on macrophage aggregates in white perch Morone americana from Chesapeake Bay, USA

The response of macrophage aggregates in fish to a variety of environmental stressors has been useful as a biomarker of exposure to habitat degradation. Total volume of macrophage aggregates (MAV) was estimated in the liver and spleen of white perch Morone americana from Chesapeake Bay using stereological approaches. Hepatic and splenic MAV were compared between fish populations from the rural Choptank River (n = 122) and the highly urbanized Severn River (n = 131). Hepatic and splenic MAV increased with fish age, were greater in females from the Severn River only, and were significantly greater in fish from the more polluted Severn River (higher concentrations of polycyclic aromatic hydrocarbons, organochlorine pesticides, and brominated diphenyl ethers). Water temperature and dissolved oxygen had a significant effect on organ volumes, but not on MAV. Age and river were most influential on hepatic and splenic MAV, suggesting that increased MAV in Severn River fish resulted from chronic exposures to higher concentrations of environmental contaminants and other stressors. Hemosiderin was abundant in 97% of spleens and was inversely related to fish condition and positively related to fish age and trematode infections. Minor amounts of hemosiderin were detected in 30% of livers and positively related to concentrations of benzo[a]pyrene metabolite equivalents in the bile. This study demonstrated that hepatic and splenic MAV were useful indicators in fish from the 2 tributaries with different land use characteristics and concentrations of environmental contaminants. More data are needed from additional tributaries with a wider gradient of environmental impacts to validate our results in this species.

Insights into the development of hepatocellular fibrillar inclusions in European flounder (Platichthys flesus) from UK estuaries

Hepatocellular fibrillar inclusions (HFI) are an unusual pathology of unknown aetiology affecting European flounder (Platichthys flesus), particularly from estuaries historically impacted by pollution. This study demonstrated that the HFI prevalence range was 6-77% at several UK estuaries, with Spearman rank correlation analysis showing a correlation between HFI prevalence and sediment concentrations of ∑PBDEs and ∑HBCDs. The data showed that males exhibit higher HFI prevalence than females, with severity being more pronounced in estuaries exhibiting higher prevalence. HFI were not age associated indicating a subacute condition. Electron microscopy confirmed that HFI were modified proliferating rough endoplasmic reticulum (RER), whilst immunohistochemistry provided evidence of VTG production in HFI of male P. flesus. Despite positive labelling of aberrant VTG production, we could not provide additional evidence of xenoestrogen exposure. Gene transcripts (VTG/CHR) and plasma VTG concentrations (>1 μg ml^-1), were only considered elevated in four male fish showing no correlation with HFI severity. Further analysis revealed that reproductively mature female P. flesus i.e. >3-year-old, did not exhibit HFI, whereas males of all ages were affected. This, combined with previous reports that estradiol (E2) can impair mixed function oxygenase activity, supports a hypothesis that harmful chemical metabolites (following phase 1 metabolism of their parent compounds) are potentially responsible for HFIs observed in male and ≤ 3-year-old female fish. Consequently, HFI and xenoestrogenic induced VTG production could be independent of each other resulting from different concurrent toxicopathic mechanisms, although laboratory exposures will likely be the only way to determine the true aetiology of HFI.

The use of Atlantic hagfish (Myxine glutinosa) as a bioindicator species for studies on effects of dumped chemical warfare agents in the Skagerrak. 1: Liver histopathology

Within the framework of the international project DAIMON (Decision Aid for Marine Munitions), the impact of dumped chemical munitions on fish health was investigated. The Skagerrak Straight (North Sea, at 600 m depth) contains munitions with chemical warfare agents (CWA), scuttled after the end of World War II. Studies of liver histopathology in Atlantic hagfish (Myxine glutinosa) were carried out at three sampling sites: at a wreck with CWA in the Skagerrak (n = 82), a Skagerrak reference site considered to be free of CWA (n = 14) and at a reference site in the northern North Sea outside the Skagerrak (n = 17). Liver lesions were diagnosed and categorized according to standardized ICES and BEQUALM protocols and OSPAR guidelines. Non-specific liver lesions were found in 87.6% of 113 hagfish examined. The prevalence of pre-neoplastic lesions was 7.1% and of neoplastic lesions 6.2%. There was no statistically significant difference in prevalence between hagfish samples from the wreck site and from the reference site near the wrecks. However, at the reference site in the northern North Sea, the prevalence of non-specific lesions was low and neither pre-neoplastic nor neoplastic lesions were observed.

Are anthropogenic fibres a real problem for red mullets (Mullus barbatus) from the NW Mediterranean?

Microfibres are among the most prevalent type of microplastics in marine environments. Man-made fibres derived from cellulose are distributed worldwide, but are often confused with synthetic plastic fibres and consequently neglected. All these fibres may adversely affect aquatic organisms, but their levels and potential effects in wild fish remain unknown. We analysed anthropogenic fibre (AF) ingestion in the red mullet (Mullus barbatus), at both temporal and geographical scales, to assess potential effects of these fibres on fish health condition. AFs were present in 50% of fish digestive tracts, with a mean of 1.48 AFs per individual (SD = 1.98). In Barcelona, an increase of 46% in AF ingestion was observed in 2018 compared to 2007. AF ingestion also increases by 20% when Barcelona is compared to a less urban area (the town of Blanes). Visual characterization of fibres by typologies-corroborated by Raman spectroscopy-allowed classification and identification of 88% of AFs as cellulosic (57%), and synthetic polymers (PET) (31%). In all sampling stations, the only histopathological alterations were cysts of unknown etiology, and the most abundant parasites were nematodes. None of these alterations, parasite load, or other fish health indicators (condition indices) indicate an effect of AF ingestion.

Biological responses and toxicopathic effects elicited in Solea senegalensis juveniles on exposure to contaminated sediments under laboratory conditions

Whole-sediment toxicity assays contribute to elucidating the intricate association between the presence of contaminants in sediments and their toxicopathic effects in benthic fish. In the present study, Solea senegalensis juveniles were exposed under laboratory conditions to contaminated whole-sediments for 7 and 28 days. Sediments were obtained from a low to moderately polluted estuary, a highly polluted harbour and from the mixture of both field-collected sediments. Biometry data were recorded. Liver, brain, gills, and gonads were dissected out and processed to determine markers of oxidative stress, neurotoxicity and lysosomal biomarkers, and histopathology. Analyses of sediment granulometry and chemical profiles indicated different degrees of toxicity and suggested a distinct release of pollutants from each sediment in relation with their physicochemical properties. Interestingly, biological responses were in agreement with contaminant levels reported in source sediments. The most distinct toxicopathic effects were detected upon exposure to the harbour's sediment and particularly on day 28. Overall, enhanced hepatic glutathione-S-transferase activity and lysosomal enlargement were detected in all experimental groups, demonstrating a toxic effect from all sediments whilst catalase inhibition, lysosomal membrane destabilisation, changes in lysosomal content and liver histopathology were most pronounced in soles exposed to the harbour's sediment. The Integrative Biomarker Response index (IBR/n) evidenced that exposure to the three sediments caused an impact of diverse magnitude in sole health (IBR/n_Harbour > IBR/n_Mixture > IBR/n_Estuary). The magnitude of biological responses essentially depended on the presence of contaminants in source sediments, which seemed to be altered by the conditions imposed by whole-sediment toxicity assays.

Biomarcadores histológicos em Sciades herzbergii (Pisces, Ariidae) para avaliação de impactos em ambientes estuarinos da Baía de São Marcos, Maranhão

RESUMO Neste estudo, objetivou-se avaliar o impacto ambiental em áreas estuarinas da Baía de São Marcos, Maranhão, utilizando-se alterações histológicas nas brânquias e no fígado de Sciades herzbergii como biomarcadores de contaminação aquática. Foram realizadas coletas no período chuvoso (março de 2018) e de estiagem (julho de 2018), em que foram capturados 40 exemplares de S. herzbergii em duas regiões distintas da Baía de São Marcos: A1) Ilha dos Caranguejos (área referência); A2) Terminal de Pesca Industrial de Porto Grande (área potencialmente contaminada). As estações foram georreferenciadas por GPS e, em cada local de captura dos peixes, registraram-se as seguintes variáveis abióticas: temperatura, salinidade, pH e oxigênio dissolvido. Em campo, os organismos foram pesados e medidos, as brânquias e os fígados foram retirados e fixados. Posteriormente, foram mantidos em álcool a 70% até o procedimento histológico padrão. Resultados indicam que as duas áreas são semelhantes em termos de características físico-químicas da água e do sedimento. Todavia, a análise semiquantitativa das alterações histológicas observadas revelou que as brânquias foram o órgão mais afetado nos peixes de A2, indicando que os peixes desse local apresentam danos teciduais maiores resultantes de estresse acentuado por impactos antrópicos.

Accumulation and histopathological effects of cadmium on the great pond snail Lymnaea stagnalis Linnaeus, 1758 (Gastropoda: Pulmonata)

Toxic metal ions are an important stress factor for a living organism. In this study, accumulation and histopathological changes in foot, mantle and hepatopancreas of great pond snail, Lymnaea stagnalis exposed to different Cadmium (Cd) concentrations in laboratory conditions were investigated. Great pond snails were exposed to sublethal concentrations of 7.92 μg/L, 15.85 μg/L, 31.7 μg/L and 63.4 μg/L Cd. At the end of 7, 14, 21 and 28 days, snail foot, mantle and hepatopancreas were removed to investigate and determine Cd accumulation and histopathological alterations by light microscopy. Cd levels determined in hepatopancreas were higher than those measured from the foot and the mantle of studied specimens. A positive correlation was found between Cd levels in tissues and exposure days. As a result of Cd application, we observed increase in the number of mucosit, pigment and protein cells and desquamation in the epithelium in the foot, atrophy in muscle fibrils, connective tissue cells and increase in the lipid vacuoles in the mantle, increase in the lipid vacuoles and amoebocyte in the hepatopancreas. The severity of the alterations resulting from Cd increased with dose-time dependent.

Histopathological assessment of seven year-classes of Delta Smelt

The Delta Smelt (Hypomesus transpacificus) is an imperiled, annual fish endemic to the Sacramento-San Joaquin Delta and San Francisco Estuary. This study examined the severity and prevalence of liver and gill lesions of juvenile through adult Delta Smelt from 2011 through 2017 collected from five regions throughout its habitat (n = 1,053). The first and last years of the study were wet, but bracketed an extreme drought in CA (2012-2016), during which the Delta Smelt population reached historical lows. Overall, the three most common lesions were gill ionocyte hyperplasia, liver lipidosis, and gill aneurysm. Individuals with higher fork lengths exhibited increased gill and liver lesion score (summations of the severity scores), suggesting that Delta Smelt accumulate lesions through their lives, and that larger individuals were more tolerant of liver and gill lesions. Liver lesion score showed significant regional differences, while salinity was a better predictor of gill lesions than region, with lower gill lesion scores associated with higher salinities. Largely consistent with previously reported histopathology patterns, Delta Smelt collected from the Confluence and Suisun Marsh had the lowest liver lesion score, while Delta Smelt collected from Cache Slough and Suisun Bay had the highest lesion scores, and Suisun Marsh had the lowest glycogen depletion, suggesting heterogeneous levels of exposure to environmental stressors across regions. Gill and liver lesion score also varied significantly with year-class. The highest gill lesion score occurred in the 2015/16 year-class, and the lowest occurred in the 2017/18 year-class, a 2.8-fold difference. Controlling for size and regional effects, individuals with comparatively high liver lesion scores were prevalent in the population until the 2014/15 year-class. In the two subsequent year-classes, Delta Smelt livers were in the best condition, coinciding with peak drought conditions and record low abundances.

Multi-Biomarker Assessment in Common Carp (Cyprinus carpio, Linnaeus 1758) Liver after Acute Chlorpyrifos Exposure

The excessive use of pesticides at different stages of crop production can pose a great danger to the aquatic environment, and particularly to fish. The purpose of the present work was to assess the negative effects of chlorpyrifos (CPF) on the liver histological architecture and the activities of marker enzymes in common carp (Cyprinus carpio Linnaeus, 1758), by applying a multi-biomarker technique. The tested insecticide is categorized as a priority pollutant in surface waters in terms of Directive 2013/39/EU. The carps were exposed to different and environmentally relevant CPF concentrations for 72 h (a short-term acute experiment). The results showed that the tested insecticide alters the liver histological structure, causing degenerative lesions, such as granular and vacuolar degeneration; necrobiotic alterations and necrosis, as well as changes in the circulatory system. In addition, CPF induces changes in the enzymatic activity of lactate dehydrogenase (LDH), aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), cholinesterase (ChE), glutathione peroxidase (GPx) and catalase (CAT). The results from such experimental set ups could be successfully used in the legislation related to the protection of water bodies from contamination, in areas with intensive application of plant protection products used in agricultural practices, and also in implementing the Water Frame Directive by using multi-biomarker approaches.

3-(4-Methylbenzylidene) camphor induced reproduction toxicity and antiandrogenicity in Japanese medaka (Oryzias latipes)

To assess the toxic effects of 3-(4-Methylbenzylidene) camphor (4-MBC) at environmentally relevant concentrations on the reproduction and development of Japanese medaka (Oryzias latipes), adult paired medaka (F0) were exposed to 5, 50, and 500 μg/L 4-MBC for 28 d in the current study. The fecundity and fertility were significantly decreased at 500 μg/L 4-MBC (p < 0.05). Histological observations showed that spermatogenesis in F0 males was significantly inhibited at 50 and 500 μg/L 4-MBC, similar to the effects obtained with all treatments of plasma 11-ketotestosterone (p < 0.05). Moreover, the plasma vitellogenin and estradiol levels in F0 females were significantly increased at 5 μg/L 4-MBC (p < 0.05). All the transcripts of hypothalamic-pituitary-gonadal (HPG) axis-related genes tested in the brains and gonads of males were significantly increased at all treatments, similar to the effects obtained for erα, erβ and vtg in the livers and in contrast to those found for arα in the livers (p < 0.05). Equal numbers of embryos were exposed to tap water and 4-MBC solutions. Significantly increased times to hatching, decreased hatching rates and decreased body lengths at 14-day post-hatching (dph) were obtained at 500 μg/L 4-MBC treatment (p < 0.05). The cumulative death rates at 14 dph were significantly increased with all the treatments (p < 0.05). Therefore, our results showed that long-term exposure to 50 and 500 μg/L 4-MBC causes reproductive and developmental toxicity and thus provide new insight into antiandrogenicity and the mechanism of 4-MBC in Japanese medaka.

Toxicity evaluation and microbiota response of the lined sole Achirus lineatus (Chordata: Achiridae) exposed to the light petroleum water-accommodated fraction (WAF)

Exposure to contaminants might directly affect organisms and alter their associated microbiota. The objective of the present study was to determine the impact of the petroleum-water-accommodated fraction (WAF) from a light crude oil (API gravity 35) on a benthic fish species native from the Gulf of Mexico (GoM). Ten adults of Achirus lineatus (Linnaeus, 1758) were exposed to a sublethal WAF/water solution of 50% v/v for 48 hr. Multiple endpoints were measured including tissue damage, presence of polycyclic aromatic hydrocarbons (PAHs) metabolites in bile and gut microbiota analyses. Atrophy and fatty degeneration were observed in livers. Nodules and inflammation were detected in spleen, and structural disintegration and atrophy in the kidney. In gills hyperplasia, aneurysm, and gills lamellar fusion were observed. PAHs metabolites concentrations in bile were significantly higher in exposed organisms. Gut microbiome taxonomic analysis showed significant shifts in bacterial structure and composition following WAF exposure. Data indicate that exposure to WAF produced toxic effects in adults of A. lineatus, as evidenced by histological alterations and dysbiosis, which might represent an impairment to long-term subsistence of exposed aquatic organisms.

Chronic microfiber exposure in adult Japanese medaka (Oryzias latipes)

Microplastic fibers (MFs) pollute aquatic habitats globally via sewage release, stormwater runoff, or atmospheric deposition. Of the synthetic MFs, polyester (PES) and polypropylene (PP) are the most common. Field studies show that fish ingest large quantities of MFs. However, few laboratory studies have addressed host responses, particularly at the organ and tissue levels. Adult Japanese medaka (Oryzias latipes), a laboratory model fish, were exposed to aqueous concentrations of PES or PP MFs (10,000 MFs/L) for 21 days. Medaka egested 1,367 ± 819 PES MFs (0.1 ± 0.04 mg) and 157 ± 105 PP MFs (1.4 ± 0.06 mg) per 24 hrs, with PP egestion increasing over time. Exposure did not result in changes in body condition, gonadosomatic- or hepatosomatic indices. PES exposure resulted in no reproductive changes, but females exposed to PP MFs produced more eggs over time. MF exposure did not affect embryonic mortality, development, or hatching. Scanning electron microscopy (SEM) of gills revealed denuding of epithelium on arches, fusion of primary lamellae, and increased mucus. Histologic sections revealed aneurysms in secondary lamellae, epithelial lifting, and swellings of inner opercular membrane that altered morphology of rostral most gill lamellae. SEM and histochemical analyses showed increased mucous cells and secretions on epithelium of foregut; however, overt abrasions with sloughing of cells were absent. For these reasons, increased focus at the tissue and cell levels proved necessary to appreciate toxicity associated with MFs.

Environmental exposure of arsenic and fluoride and their combined toxicity: A recent update

Environmental exposure to arsenic (As) and fluoride (F) in the recent year has been increased because of excessive use of naturally contaminated ground water. Surface water is also regularly contaminated with these elements in various industrial areas. Arsenicosis and fluorosis upon individual exposure of As and F are reported in many studies. A syndrome of endemic As poisoning and fluorosis occurs during concurrent exposure of As and F. Previous reports showed synergistic, antagonistic and independent effects of these two compounds, although few recent reports also revealed antagonistic effects after co-exposure. Interaction during intestinal absorption and influence of F on As metabolism might be the cause of antagonism. The synergism/antagonism is thought to depend on the dose and duration of the co-exposure. However, the detailed mechanism is still not fully understood and needs further studies. Removal technologies of As and F from contaminated water is available but removal of such contaminants from food is yet to be developed. Antioxidants are useful to mitigate the toxic effects of As and F. This review focused on the effect of co-exposure, amelioration as well as removal techniques of As and F.

Acute exposure to the water-soluble fraction of gasoline (WSFG) affects oxygen consumption, nitrogenous-waste and Mg excretion, and activates anaerobic metabolism in the goldfish Carassius auratus

Contamination of aquatic environments by petroleum and its products (e.g. gasoline) is a hazard for aquatic organisms as a result of the potential toxicity of monocyclic aromatic hydrocarbons (BTEX) and polycyclic aromatic hydrocarbons (PAH). Our goal was to evaluate the acute effects of the water-soluble fraction of gasoline (WSF_G) on nitrogen excretion, osmoregulation, and metabolism of goldfish Carassius auratus. We first chemically characterized the WSF_G and then tested its effects on these physiological aspects of C. auratus, in several different exposure scenarios (0, 0.25, 5, 10 and 25% of WSF_G). The WSF_G contained high concentrations BTEX (toluene 70% and benzene 17%) relative to PAH (<1%), and low levels of several metals (Al, Fe, Zn, Sr). Routine O₂ uptake rate (MO₂) of goldfish was inhibited by exposure to 5% WSF_G, and during post-exposure recovery, MO₂ increased in a dose-dependent fashion. Ammonia excretion was not affected by exposure to WSF_G, but urea-N excretion increased progressively with the WSF_G concentration. The same pattern of dose/response was observed for net Mg²⁺ loss rates and steadily increasing plasma lactate concentrations. Loss rates of Na⁺, Ca²⁺, K⁺ and Cl^-, and plasma concentrations of Mg²⁺ and urea-N were not significantly altered. We propose that acute exposure to WSF_G inhibits aerobic metabolism and activates anaerobic metabolism, breaking down ATP such that bound Mg²⁺ is liberated and the purine ring component is metabolized to urea-N, both of which are subsequently excreted.

Ecotoxicity of nanomaterials in amphibians: A critical review

Nanomaterials (NMs) have been used in a growing number of commercial products, and their rapid expansion could lead to their release into the aquatic environments. However, there is limited knowledge about the impact of NMs in the biota, especially the amphibians. The present study revised the historical use of amphibian species as a model system for nanoecotoxicological studies and summarized the data available in the scientific literature about the genotoxic, mutagenic, histopathological, embryotoxic and reproductive effects of NMs in different groups of amphibians. The interaction, bioaccumulation, mode of action (MoA) and ecotoxicity of NMs on amphibians were also revised. The nanoecotoxicological studies were conducted with 11 amphibian species, being eight species of the order Anura and three species of the order Caudata. Xenopus laevis was the most studied species. The studies were conducted mainly with inorganic NMs (72%) compared to organic ones. The nanoecotoxicity depends on NM behavior and transformation in the environment, as well as the developmental stages of amphibians. The known effects of NMs in amphibians were mainly reported with reactive oxygen species (ROS) production, oxidative stress, and genotoxic effects. Results emphasize the need for further studies testing the ecotoxicity of different NMs, concentrations and exposure periods at environmentally relevant approaches. Furthermore, standard protocols for nanoecotoxicological tests using amphibians are required. Revised data showed that amphibians are suitable organisms to assess the environmental impact of NMs and indicated significant research gaps concerning the ecotoxicity of NMs on freshwater ecosystems and recommendations for future researches.

Mixture effect of arsenic and fluoride at environmentally relevant concentrations in zebrafish (Danio rerio) liver: Expression pattern of Nrf2 and related xenobiotic metabolizing enzymes

Nrf2 is a crucial transcription factor that regulates the expression of cytoprotective enzymes and controls cellular redox homeostasis. Both arsenic and fluoride are potent toxicants that are known to induce Nrf2. They are reported to coexist in many areas of the world leading to complex mixture effects in exposed organisms. The present study investigated the expression of Nrf2 and related xenobiotic metabolizing enzymes along with other stress markers such as histopathological alterations, catalase activity, reduced glutathione content and lipid peroxidation in zebrafish liver as a function of combined exposure to environmentally relevant concentrations of arsenic (37.87 μgL^-1 or 5.05 × 10^-7 M) and fluoride (6.8 mg L^-1 or 3.57 × 10^-4 M) for 60 days. The decrease in the total reduced glutathione level was evident in all treatment conditions. Hyperactivity of catalase along with conspicuous elevation in reactive oxygen species, malondialdehyde content and histo-architectural anomalies signified the presence of oxidative stress in the treatment groups. Nrf2 was seen to be induced at both transcriptional and translational levels in case of both individual and co-exposure. The same pattern was observed in case of its nuclear translocation also. From the results of qRT-PCR it was evident that at each time point co-exposure to arsenic and fluoride seemed to alter the gene expression of Cu/Zn Sod, Mn Sod, Gpx and Nqo1 just like their individual exposure but at a very low magnitude. In conclusion, this study demonstrates for the first time the differential expression and activity of Nrf2 and other stress response genes in the zebrafish liver following individual and combined exposure to arsenic and fluoride.

Multi-annual survey of health status disturbance in the Bilbao estuary (Bay of Biscay) based on sediment chemistry and juvenile sole (Solea spp.) histopathology

The Bilbao estuary (SE Bay of Biscay) is a recovering ecosystem whose sediments are still contaminated. They represent a potential risk for the biota including benthic and demersal species living in direct contact with the sediment. In this context, the present study aims to survey trends of the health status of the Bilbao estuary based on sediment chemistry and sole (Solea spp.) histopathology. Monitoring campaigns were carried out every autumn from 2011 to 2017 along the estuary. Contaminant levels were measured in sediments; liver, gills and gonads of juvenile fish were collected for histopathology. Overall, contaminant levels fluctuated throughout the years, with highest values recorded in the earlier years of the study period. Sole histopathology showed alterations of mild severity. Results permitted to assess the environmental health status of the Bilbao estuary during 7 years, although no clear temporal trend was detected. Longer-term monitoring programmes are necessary to confirm the ecosystem recovery.

Gonad pathology and intersex severity in pelagic (Tilapia zilli) and benthic (Neochanna diversus and Clarias gariepinus) species from a pesticide-impacted agrarian catchment, south-south Nigeria

Pesticides are distributed to different degrees in surface water and sediment, thus, risks of toxicity and adverse impacts to physiology of resident species could be determined by their microhabitat (sub-habitat) associations, either water column or sediment. River Owan receives pesticide input from diffuse sources from adjacent farmlands. Surface water, sediment and fish samples [(Pelagic: Tilapia zilli (n = 92) and benthic: Neochanna diversus (n = 59), Clarias gariepinus (n = 68) were collected within the catchment area across seasons for 18-months (August 2016-January 2018) and measured for pesticide levels. Testicular and Ovarian tissue samples across the three species were also examined for pathological alterations. Individual pesticide concentrations in surface water and sediment exceeded international allowable limits, while concentration of pesticide residues in tissues of benthic species was higher compared to pelagic fish. Histopathological assessment revealed a higher incidence of ovarian disruption including atretic follicles, intersex and disorganization of ovarian structure in benthic (bottom-dwelling) fish (C. gariepinus and N. diversus) compared to pelagic (water-column) fish (T. zilli). Males benthic fish species also recorded more severe anomalies, compared to pelagic fish. The damages and anomalies observed in ovarian and testicular tissue indicate chronic responses to pollutant exposure, and implicates the elevation of pesticide concentrations in surface water and sediment above permissible limits. The higher incidence of anomalies recorded for benthic species compared to pelagic species, indicates greater risks of reproductive disruption and could be associated with the microhabitat preferences (water-column or sediment).

Feminization, altered gonadal development, and liver damage in least killifish (Heterandria formosa) exposed to sublethal concentrations of 17α-ethinylestradiol

The widespread use of the synthetic estrogen 17 α-ethinylestradiol (EE₂) has resulted in elevated levels in aquatic environments, where it is known to act as an endocrine disrupting chemical affecting fish and other aquatic organisms. Examining changes in the structure of the fish' gonads and liver has proven to be an effective approach for assessing these impacts. While changes have been reported for various fish species, it is not clear whether impacts are equally severe in live-bearing fishes. The present study looked at gonadal and liver development in EE₂-exposed least killifish (Heterandria formosa), a live-bearing Poeciliid. Exposures to 0, 5, or 25 ng/L EE₂ began within six days of birth and continued until fish became sexually mature 12-23 weeks later. Exposure to 5 ng/L EE₂ resulted in severe intersex in fish with external male characteristics, a slowdown of spermatogenesis in these intersex fish and a slowdown of oogenesis in the female fish. Moreover, these fish had a variety of liver injuries. Fish exposed to 25 ng/L EE₂ exhibited intersex but at a lower frequency than occurred at 5 ng/L. In contrast, liver damage and slowdown of both oogenesis and spermatogenesis exhibited the typical dose-dependence. These findings illustrate the importance of including histological analyses when assessing endocrine disruption in fish, demonstrate that the live-bearing mode of reproduction appears to provide limited protection from the effects of waterborne EE₂, and provide further evidence that EE₂ has multiple impacts on fish health and reproduction that are severe enough to potentially affect fish populations.

Uncommon hepatic macrophagic foamy-cell nodules in Iberian barbel (Luciobarbus bocagei Steindachner, 1864) from the Vizela River (Portugal)

The main intent of this work (after the by chance finding, in archived histological slides) is to characterize one previously non-described liver lesion of the Iberian barbel from the Vizela River (Portugal). This ran through a textile and dyeing industrial region. The lesion type was made of groups of foamy cells (presumptive macrophages), which appear either as a "smaller non-nodular form," without a connective tissue capsule and displaying an irregular profile, or as a "bigger nodular form," presenting a thin capsule and a circular profile. The nodular forms could appear multi-layered, resembling "cross-sectioned onions". The lesions number, dimension, and structural complexity were greater in bigger fish, appearing only after a history of poor water quality. In extreme cases, the lesions slightly protruded the liver surface. Special histological staining proved the connective tissue nature of the capsule (and its eventual septa), the presence of proteins, glycoproteins, lipofuscin, melanin, iron (putative hemosiderin), and copper, in a variable number of foamy cells within the lesions. At times, degenerating hepatocytes appeared at the border of the lesions. It is proposed that this lesion type incorporates both macrophages and degenerating hepatocytes, looking as one (unpublished) form of a macrophage aggregate. The term "foamy-cell nodules" was advanced for this abnormality. The lesion could have been induced by pollution, because: no parasites were ever associated with the lesion; there was co-existence of the lesion with a water quality status scored as "bad"; such lesion neither existed in fish sampled after mitigation and remediation measures nor in reference fish.

A screening test based on hematological and histological biomarkers to evaluate the environmental impacts in tambaqui (Colossoma macropomum) from a protected area in Maranhão, Brazilian Amazon

Nowadays biomonitoring programs can benefit with mathematical models able to correlate biomarkers to monitor water pollution. The aim of this study was to develop a screening test based on hematological parameters and histological lesions in tambaqui (Colossoma macropomum), to allow the assessment of environmental impacts on fish inhabiting a protected area in Maranhão inside of Brazilian Amazon. Samples collected during three years (2012, 2013 and 2014) were grouped by season (dry and rainy) Water samples were also collected for physical chemistry analysis. Blood samples were stained with Acridine Orange to detect micronuclei and erythrocyte abnormalities. Gill tissues were stained with hematoxylin and counterstained with alcoholic eosin, and histopathological lesions were scored on a scale of 1-3, being 1 = minimal pathological importance, 2 = moderate pathological importance and 3 = marked pathological importance. A screening test for evaluating environmental impact was developed by fitting the measured data (necrosis, erythrocyte abnormalities, number of micronuclei) from tambaqui. A three-dimensional surface was fit to the empirical data. Our proposed model predicted the probability of necrosis (observed in euthanized animals) based on the numbers of micronuclei and abnormal erythrocytes (observed in blood samples from live animals) (correlation coefficient R = 0.89). The methodology could be applied for predicting contamination histories (chronic pollution that induces branchial lesions) in rivers using the micronucleus and erythrocyte abnormalities of the fishes (with a simple blood sample).

Histological and Genotoxic Biomarkers in Prochilodus lacustris (Pisces, Prochilodontidae) for Environmental Assessment in a Protected Area in the Northeast of Brazil

The quality of aquatic environments all around the world is being altered by different human activities that represent direct threat to the ecological system and the aquatic biota. This study aimed to evaluate the occurrence of histological and genotoxic alterations in Prochilodus lacustris as indicators of anthropic impacts in a lacustrine environment in northeast Brazil. The histological alterations were evaluated using the histological alteration index, and the genotoxic alterations were detected using the micronuclei test, at three sampling stations (S1, S2 and S3). The gills presented lesions with three stages of severity, with mild lesions more frequent in the specimens collected at station S1. Mild hepatic tissue lesions were the most frequent type in both areas. Micronucleus analysis showed that station S3 was the most affected. The biological responses observed indicated that the fish are under influence of environmental changes. It is important to highlight that the organisms collected at station S3 had a more compromised health status.