Mercury pollution and macrophage centres in pike (Esox lucius) tissues

A multi-level assessment of biological effects associated with mercury concentrations in smallmouth bass, Micropterus dolomieu

Total mercury (THg) was measured in muscle (fillet) and liver tissue of adult smallmouth bass Micropterus dolomieu collected at multiple sites in the Potomac and Susquehanna River drainages within the Chesapeake Bay watershed. Smallmouth bass in these drainages have experienced episodic mortality events, a high prevalence of skin lesions and reproductive endocrine disruption (intersex or testicular oocytes and plasma vitellogenin in males). A multi-level assessment of general and reproductive health including indicators at the organismal, organ, cellular and molecular levels was conducted on adult smallmouth bass during the spring (prespawn) season. Concentrations of THg were correlated with increased visible abnormalities, increased macrophage aggregates and tissue parasite burdens. In male bass positive correlations of THg were observed with plasma vitellogenin and hepatic transcript abundance of estrogen receptor β1 and androgen receptor α, while there was a negative association with estrogen receptors α and β2 and androgen receptors β. In female bass there was a negative correlation between THg and plasma vitellogenin as well as hepatic transcript abundance of vitellogenin, choriogenin, estrogen receptor β2 and 17β hydroxysteroid dehydrogenase. Associations of THg concentrations with various biological indicators suggest mercury may be an important environmental stressor contributing to the observed adverse effects in smallmouth bass populations.

Pathologic impacts of contaminants in freshwater fish of Cook County IL

Mercury (Hg) and polychlorinated biphenyls (PCBs) are widespread environmental toxicants in urban environments with negative impacts to fish health. The present study evaluated the potential association between muscle tissue contaminant (total Hg and total PCB) concentrations and indicators of health in benthic and predatory fish collected from four Forest Preserves of Cook County lakes in the Chicago metropolitan area. Common carp (carp; Cyprinus carpio) and largemouth bass (LMB; Micropterus salmoides) were sampled three times a year (spring, summer, fall) during 2019 and 2020. Water quality analyses (temperature, color, turbidity, dissolved oxygen, total alkalinity, pH, chloride, nitrate, phosphate, ammonium, and pH) were performed concurrently with fish collections. Tissue (skin-on fillet) contaminant concentrations were compared between lake types and fish species and assessed for any relationship with fish morphometric data and pathologic lesions. Main health indicator endpoints included muscle lipid content, parasite burden, and pathologic lesions. Mean total PCB concentrations were greater in carp (203.1 ± 152 µg/kg, wet weight), and mean Hg concentrations were greater in LMB (0.11 ± 0.1 mg/kg, wet weight). In most fish, concentrations of both toxicants surpassed the EPA's lowest threshold to restrict fish consumption for sensitive cohorts (0.029 mg/kg for Hg and 1.5 µg/kg for PCBs). In both species, Hg positively correlated with splenic pigmented macrophage aggregate area (P < 0.001). In carp, Hg also positively correlated with hepatocellular pigmentation (P < 0.01). Mercury correlated with standard length in both species (LMB: P < 0.001, carp: P = 0.95), but polychlorinated biphenyls only correlated with standard length in carp (P < 0.001). No association was found between intraspecific contaminant concentrations and parasite burden, year, or lake type, though differences were noted among individual lakes. The contaminant burden appeared well-tolerated with only mild Hg-associated and no appreciable PCB-associated lesions. However, possible effects on reproduction or behavior were not fully assessed, and future studies are warranted.

Mercury offloading in gametes and potential adverse effects of high mercury concentrations in blood and tissues of Atlantic Goliath Grouper Epinephelus itajara in the southeastern United States

Mercury (Hg) is a ubiquitous and non-essential heavy metal that is highly toxic to aquatic organisms. Few studies examine Hg and its effects on wild fish populations. Here, we investigated the potential effects of Hg exposure on a large and long-lived marine species of conservation concern, the vulnerable Atlantic Goliath Grouper Epinephelus itajara. Our objectives were (1) to measure Hg (methyl-Hg; and total Hg = combined methyl-Hg and inorganic-Hg) concentrations in whole blood (WB) and gametes (eggs and sperm); (2) to investigate the relationships between Hg concentrations in muscle and liver with WB and gametes; (3) to investigate the relationships between Hg concentrations in liver, muscle, and WB with hematological and plasma biochemical analytes; and (4) to investigate the relationship between liver Hg and pigmented macrophage aggregates in liver tissue sections. We found several lines of evidence for potential adverse effects on Goliath Grouper health and reproduction by high Hg concentrations in liver, muscle, WB, and gametes, including (1) Hg concentrations in all tissues and gametes were well above observable ranges of marine and freshwater fishes from experimental exposure studies; (2) gamete Hg concentrations were among the highest recorded in wild fishes, with seasonal patterns suggesting females offload significant amounts of Hg into their eggs during the spawning season; (3) Methyl-Hg was highest in muscle, followed by sperm, liver, eggs, and WB; (4) there were significant correlations between liver, muscle, and WB Hg concentrations with various blood analytes; (5) vitellogenin positively correlated with female liver methyl-Hg concentrations, and was abnormally high in males, suggesting direct endocrine effects; and (6) liver total Hg positively correlated with pigmented macrophage aggregate count and percent area. This work will help guide future research examining the potential adverse effects of Hg and its role as an additional stressor on wild fish populations.

Productive Results, Oxidative Stress and Contaminant Markers in European Sea Bass: Conventional vs. Organic Feeding

In the present study European sea bass (Dicentrarchus labrax) subjected to two different diets (organic vs. conventional) were evaluated in terms of growing performances, oxidative stress, and contaminant markers. Growing performances were evaluated using biometric measures and condition factor (K), whereas insulin-like growth factor (IGF-I and IGF-II) levels were assessed trough Real-Time PCR analysis. For oxidative stress, immunohistochemical staining for 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4-hydroxy-2-nonenal (HNE) was performed, whereas total glutathione (GSH) in blood serum was determined by an enzymatic method adapted. Cytochrome P4501A (CYP1A) and melanomacrophage centers (MMCs) were evaluated as contaminant markers trough immunohistochemical and histochemical approaches, respectively. The growing performances showed a positive trend in both groups but a greater productivity in conventional fed fish compared to the organic ones. A significant higher expression of MMCs was observed in organic vs. conventional diet fed fish. Fillet analysis showed a higher MUFA content and a lower PUFAs n-6 content in organically fed sea bass indicating that diets with a content in fatty acids closer to that of wild fish will definitely affect the fatty acid profile of the fish flesh. On the other hand, the diet composition did not seem to affect neither the oxidative stress parameters (GSH, 8-OHdG, HNE) nor the CYP1A expression.

The effect of different pollutants exposure on the pigment content of pigmented macrophage aggregates in the spleen of Vardar chub (Squalius vardarensis Karaman, 1928)

Pigmented macrophage aggregates (MAs) are known to change under influence of various factors, such as aging, season, starvation, and/or pollution. In this study, changes in the pigment content of the MAs in the spleen of Vardar chub (Squalius vardarensis, Karaman) (n = 129) collected in spring and autumn, from three rivers with different pollution impact was examined: Zletovska River (metals), Kriva River (metals and municipal wastewater), and Bregalnica River (municipal wastewater). Collected data revealed increased relative volume and number of MAs containing hemosiderin under the influence of metals, significant in autumn (p < .05). In chub exposed to metals combined with municipal wastewater, significant increase of lipochrome accumulation in MAs in autumn, melanin in MAs in fish captured in the spring season, and number of splenic MAs containing combination of melanin and lipochrome was noted. Volumes and number of MAs containing combination of hemosiderin and lipochrome increased in spleen of fish captured in autumn from both Zletovska River and Kriva River, most likely due to the contribution of hemosiderin and lipochrome, respectively. Values measured for the various pigments in splenic MAs in fish captured from Bregalnica River, were overall closer to the values measured for fish captured from Kriva River. Notably, melanin and lipochrome are more likely to be found in fish from waters influenced by municipal wastewater (organic pollution) and hemosiderin in fish spleen from water influenced by mining activity (heavy metals pollution).

Comparisons of Stereological and Other Approaches for Quantifying Macrophage Aggregates in Piscine Spleens

Macrophage aggregates (MAs) are focal accumulations of pigmented macrophages in the spleen and other tissues of fish. A central role of MAs is the clearance and destruction of degenerating cells and recycling of some cellular components. Macrophage aggregates also respond to chemical contaminants and infectious agents and may play a role in the adaptive immune response. Tissue damage or physiological stress can result in increased MA accumulation. As a result, MAs may be sensitive biomarkers of environmental stress in fish. Abundance of MAs in tissues has been reported in a variety of ways-most commonly as density, mean size, and relative area-but the utility of these estimates has not been compared. In this study, four different types of splenic MA abundance estimates (abundance score, density, relative area, and total volume) were compared in two fish populations (Striped Bass Morone saxatilis and White Perch M. americana) with a wide range in ages. Stereological estimates of total volume indicated an increase in MA abundance with spleen volume, which generally corresponded to fish age, and with splenic infections (mycobacteria or trematode parasites). Abundance scores were generally limited in the ability to detect changes in MA abundance by these factors, whereas density estimates were greatly influenced by changes in spleen volume. In some instances, densities declined while the total volume of MAs and spleen volume increased. Experimentally induced acute stress resulted in a decrease in spleen volume and an increase in MA density, although the total volume of MAs remained unchanged. Relative area estimates accounted for the size and number of MAs but not for changes in organ volume. Total volume is an absolute measure of MA abundance irrespective of changes in organ volume or patterns of accumulation and may provide an improved means of quantifying MAs in the spleens of fish.

Biotransformation, antioxidant and histopathological biomarker responses to contaminants in European and American yellow eels from the Gironde and St. Lawrence estuaries

Since the early 1980s, populations of American (Anguilla rostrata) and European eels (Anguilla anguilla) have suffered a sharp decline. The causes of their decline are likely multifactorial and include chemical pollution. A field study was conducted in eight sites varying in organic and metal contamination along the St. Lawrence (Eastern Canada) and Gironde (France) systems to investigate the relationships among contaminants, biological characteristics and biotransformation, antioxidant and histopathological biomarkers in eels from both species. For A. rostrata, no major influences of persistent organic contaminants on biomarkers were identified. For A. anguilla, eels from the most contaminated site expressed higher surface of MelanoMacrophage Centers (MMCs) and eels from another contaminated site expressed higher amount of spleen lipofuscin pigment. These two histopathological biomarkers were also associated with aging. Compared to eels from the cleanest French site, higher hepatic catalase activity and density of MMC in eels from contaminated sites was related to higher concentration of organic (DDT and metabolites, sum of PCBs, sum of PBDEs) and inorganic (Hg and Cd) contaminants. In both species, a higher deposition of spleen hemosiderin pigment was measured in eels from the most brackish sites compared to eels living in freshwater environments. Our results suggest an association between higher hemosiderin pigment and metal contamination (As for A. anguilla and Pb for A. rostrata). Parasitism by A. crassus was observed in European eels from freshwater sites but not in eels from brackish habitats. Overall, contamination may pose a greater risk for the health of European compared to American eels.

Long term exposure to cadmium: Pathological effects on kidney tubules cells in Sparus aurata juveniles

The effects of an exposure to cadmium chloride 0.47μM for 150days were studied in kidneys of juveniles Sparus aurata by a multidisciplinary approach so to correlate uptake and detoxification potential to changes in brush border and glycocalyx sugar composition. Results demonstrated that cadmium concentration in kidney significantly increased from day 30 reaching a plateau on day 120 while metallothioneins reached a peak on day 90 and by day 120 were already decreasing to control values. Cytological damage was extensive on day 90, clearly detectable at both structural and ultrastructural levels, in tubular cells and brush-border. Staining with a panel of four lectins revealed a significant increase in N-Ac-Gal and a decrease in mannose in the glycocalyx and the tubular basal membranes. From day 120, when cadmium concentration was high and metallothionein concentration decreasing, a clear recovery was observed in tubular cells morphology and sugar composition. Possible significance of these apparently contrasting data are discussed.

General and histological indicators of health in wild fishes from a biological mercury hotspot in northeastern North America

Kejimkujik National Park and National Historic Site, Nova Scotia, Canada, is considered a biological mercury (Hg) hotspot because the tissues of yellow perch (Perca flavescens) and common loons (Gavia immer) inhabiting the lakes frequently exceed so-called safe levels of Hg. In the present study, the relationships between Hg and overall health of males and females of 3 forage fish species (brown bullhead Ameirus nebulosus, banded killifish Fundulus diaphanus, and golden shiner Notemigonus crysoleucas; n = 6-18/sex/lake) in 6 lakes at the park were assessed using condition factor, liversomatic index (LSI), and macrophage aggregates (MAs; indicators of tissue damage). Mean muscle total Hg (THg) concentrations of brown bullhead, banded killifish, and golden shiner across lakes were 0.32 μg/g, 0.27 μg/g, and 0.34 μg/g, respectively. Condition was negatively related to muscle THg in golden shiner and banded killifish, LSI was not related to THg in any species, and all species showed evidence of increasing MA prevalence (counts and area) with increasing THg concentrations. The MAs were most prevalent in spleen tissues of golden shiner, with mean percentage cover ranging from 0.36% to 5.59% across lakes. In addition, the area of MAs appeared to be better predicted by THg concentration than was the number of MAs in the same tissue. These findings suggest that Hg is affecting the health of wild fishes in Kejimkujik National Park and National Historic Site and that other populations with similar or higher concentrations of this metal may also be at risk. Environ Toxicol Chem 2017;36:976-987. © 2016 SETAC.

Mercury accumulation and its effects on molecular, physiological, and histopathological responses in the peacock blenny Salaria pavo

For humans, fish consumption is the major source of mercury (Hg) exposure. The aim of this study was to assess the effect of Hg in the peacock blenny Salaria pavo, a species of the family of blennies that was used as indicator of water pollution. We performed a sublethal contamination of fish to 66 μg HgCl₂ L^-1 during 1, 4, 10 and 15 days but Hg concentration measured in the experimental water was much lower than the nominal concentration. Hg was also measured in both gill and liver tissues and displays a significant increase of its concentration in gills after 1 day of exposure followed by a decrease throughout the experiment. In the liver, Hg burden reaches its maximum at day 4 followed also by a decrease. Partial-length cDNA of mt1, mt2, gpx, cat, mnsod and cuznsod was characterized. Results from mRNA expression levels displayed an up-regulation of mt1, gpx and mnsod while a downregulation of cat was observed. Several biomarker activities were determined in gills and liver and exposure to Hg affected all antioxidant enzymes in gills. EROD, GST and GPx significantly decreased, while CAT levels increased from 4 days of Hg exposure. No lipid peroxidation (LPO) induction was observed in gills of exposed fish. Regarding the liver, the activity of all enzymes increased significantly from the beginning of the experiment. LPO induction was, however, induced after 4 days only. The histological analysis also performed indicated that fish exhibited several damages in gills and liver, mainly in relation to circulatory disturbances in the gills and regressive changes in the liver. All biomarkers assessed showed that peacock blennies are able to detoxify Hg from gill and liver tissues by developing various defense mechanisms.

Morphological alterations in the liver of yellow perch (Perca flavescens) from a biological mercury hotspot

Mercury (Hg) contamination is a global issue due to its anthropogenic release, long-range transport, and deposition in remote areas. In Kejimkujik National Park and National Historic Site, Nova Scotia, Canada, high concentrations of total mercury (THg) were found in tissues of yellow perch (Perca flavescens). The aim of this study was to evaluate a possible relationship between THg concentrations and the morphology of perch liver as a main site of metal storage and toxicity. Yellow perch were sampled from five lakes known to contain fish representing a wide range in Hg concentrations in fall 2013. The ultrastructure of hepatocytes and the distribution of Hg within the liver parenchyma were analyzed by transmission electron microscopy (TEM) and electron energy loss spectrometry (EELS). The relative area of macrophage aggregates (MAs) in the liver was determined using image analysis software and fluorescence microscopy. No relation between general health indicators (Fulton's condition index) and THg was observed. In line with this, TEM examination of the liver ultrastructure revealed no prominent pathologies related to THg accumulation. However, a morphological parameter that appeared to increase with muscle THg was the relative area of MAs in the liver. The hepatic lysosomes appeared to be enlarged in samples with the highest THg concentrations. Interestingly, EELS analysis revealed that the MAs and hepatic lysosomes contained Hg.

Histopathological changes in gill and liver of Capoeta capoeta living in the Karasu River, Erzurum

The contamination of surface waters by different pollutants is an important problem worldwide. In this study, the histopathological effects of water pollution were investigated on freshwater fish species Capoeta capoeta caught from the Karasu River. Fish were caught at three different sites in the Karasu River, namely, Aşkale, Dumlu, and Serçeme. The histological changes in gill and liver of fish were detected microscopically and evaluated with quantitative analyses. In addition, heavy metals have also been determined in surface water samples from these sites. Results showed that the Aşkale site was polluted by different kinds of heavy metals. In Aşkale site, some heavy metals such as Cd, Al, As, Pb, and Mn levels were mostly detected at concentrations above than the accepted values by the Turkish Standards Institute. The presence of gill and liver histological alterations were assessed by the degree of tissue change (DTC). In gill filaments, hypertrophy and hyperplasia of the gill epithelium, lamellar epithelial lifting, lamellae shortening, vasodilatation, lamellar disorganization, blood congestion, fusion, and aneurysm were observed. In the liver, the changes included an increase in the number and size of melanomacrophage aggregates, nonhomogenous parenchyma, proliferation of the hepatopancreas, sinusoidal dilatation, vacuolization, hypertrophy of the hepatocytes, congestion and degeneration of central vein, blood congestion, pyknotic nucleus, focal necrosis, and hepatic granuloma. The histological lesions were comparatively most severe in liver. The DTC means were varied from slight to moderate of gill and moderate to severe of liver tissue in the Aşkale site, thus the site is considered to be of low quality. Some pathological alterations were observed in the Serçeme site, although their distribution was lower than sites Dumlu and especially Aşkale. The least DTC means of the Serçeme site demonstrated their good environmental quality. The results suggest that there is a close relationship between amounts of pathological alterations and environmental contamination.

Methylmercury-induced oxidative stress in rainbow trout (Oncorhynchus mykiss) liver: ameliorating effect of vitamin C

The present study was undertaken to evaluate methylmercury-induced alterations in hepatic enzymes and oxidative stress markers in liver tissue of rainbow trout (Oncorhynchus mykiss) by using a perfusion method, and to explore possible protective effect of vitamin C against these alterations. Forty-eight fish were divided into six groups containing control, test, and amelioration groups. The liver of fish in the test groups were exposed to different doses of methylmercury, i.e., 0.6, 1.2, and 2.4 μg L(-1), respectively, for 120 min. In the amelioration group, liver was treated with vitamin C (17.2 μg L(-1)) along with high dose (2.4 μg L(-1)) of methylmercury. The results of the present study showed that exposure with 0.6, 1.2, and 2.4 μg L(-1) of methylmercury significantly increased (p < 0.05) hepatic enzyme activities (alanine transaminase (ALT), aspartate transaminase (AST), and Lactate dehydrogenase (LDH)) and malondialdehyde (MDA) level, as a marker of lipid peroxidation. On the other hand, the concentration of reduced glutathione (GSH) and total antioxidant capacity of the liver decreased (p < 0.05) in the methylmercury-exposed groups when compared to the control group. Pearson's correlation analysis revealed a positive correlation between MDA concentration and ALT, AST, and LDH activities in the methylmercury groups, suggesting that the enhanced lipid peroxidation may be linked to hepatic damage caused by methylmercury. Treatment with vitamin C in methylmercury-exposed group led to a significant decrease (p < 0.05) in MDA concentration and hepatic enzyme activities and significant increase (p < 0.05) in levels of GSH and total antioxidant capacity. The values of measured parameters in the methylmercury + vitamin C group were comparable to those of the control group. The results of the present study demonstrated that methylmercury exposure induces oxidative stress in the liver of rainbow trout and treatment with vitamin C can protect fish liver against this oxidative insult.

Liver melanomacrophage centres as indicators of Atlantic bluefin tuna, Thunnus thynnus L. well-being

Melanomacrophage centres (MMCs), located in different organs of non-mammalian vertebrates, play a role in the destruction, detoxification or recycling of endogenous and exogenous materials. Cytochrome P450 monoxygenase 1A (CYP1A) is involved in xenobiotics biotransformation, and its liver expression is considered as a biomarker for detecting exposure to environmental pollutants. Atlantic bluefin tuna (ABFT), Thunnus thynnus L., liver samples were collected from: wild animals caught in the eastern Atlantic; juveniles reared in the central Adriatic; juveniles reared in the northern Adriatic; adults reared in the western Mediterranean. The samples were processed for basic histology, histochemistry and for CYP1A immunodetection. An unexpected high density of MMCs, containing ferric iron and lipofuscin-ceroids, was detected in the juveniles sampled in the northern Adriatic Sea. These individuals showed also a strong anti-CYP1A immunopositivity in hepatocytes and in the epithelium of bile ducts. This study supports the utility of MMCs as biomarkers of fish 'health status' and gives concern for a potential contaminant accumulation in ABFT.

Evidence of impaired health in yellow perch (Perca flavescens) from a biological mercury hotspot in northeastern North America

Few studies have investigated the effects of mercury (Hg) on wild fish from remote areas, even though these fish can have high total Hg concentrations. In Kejimkujik National Park and National Historic Site (KNPNHS), Nova Scotia, Canada, concentrations of total Hg in many yellow perch (Perca flavescens) currently exceed the estimated threshold level for adverse effects in fish (0.2 µg Hg g(-1) (wet wt), whole body). To determine whether Hg exposure is adversely affecting the general health of these fish, the authors collected male and female perch in the fall of 2009 and 2010 from 12 lakes within KNPNHS. The health endpoints condition, liver somatic index (LSI), and macrophage aggregates (MAs; indicators of oxidative stress and tissue damage) in the liver, kidney, and spleen were examined, and in female perch were compared between lakes and related to Hg concentrations measured in the muscle and liver tissue. No negative relationships between fish condition or LSI and Hg were found. However, within the liver, kidney, and spleen tissues of females, the relative area occupied by MAs was positively related to both muscle and liver Hg concentrations, indicating the health of these perch was adversely affected at the cellular level. These findings raise concerns for the health of these perch as well as for other wild fish populations known to have similarly elevated Hg concentrations.

Distribution and relationships of As, Cd, Pb and Hg in freshwater fish from five French fishing areas

The concentrations of arsenic, cadmium, mercury and lead in 149 muscle samples of eight freshwater fish species (European eel, bream, common carp, European catfish, roach, perch, pike and pikeperch) from five different French fishing areas from contaminated and control sites were measured by inductively coupled plasma mass spectrometry after microwave digestion under pressure. No significant correlation was found between the condition factor (CF), based on the length-mass relationship, and As, Cd and Pb levels in all the samples analysed, but a positive correlation was detected between CF and Hg levels (P<0.0001, R=0.49). Positive correlations with body length were only found for Hg in roach (P<0.05, R=0.32) and Pb in bream (P<0.05, R=0.48) and correlations with both body weight and length were also found for Hg in pike (P<0.05, R=0.90 and 0.86) and Cd in European eel (P<0.01, R=-0.35 and -0.37). The average content and the standard deviation in fish muscle samples was 0.007±0.012, 0.102±0.077, 0.142±0.097 and 0.035±0.053 mg kg(-1) of wet mass for Cd, As, Hg and Pb, respectively. Significant differences were established between groups of predatory fish and non-predatory fish for Hg and Pb, and between control and contaminated sites in the whole selection and also within feeding guilds, i.e. the values of Hg in the benthophagic fish were significantly different between these sites. Finally, these results were also compared for each species with previous French and European studies.

Histopathological biomarkers in gills and liver of Oreochromis niloticus from polluted wetland environments, Saudi Arabia

Fish live in direct contact with their immediate external environment and, therefore, are highly vulnerable to aquatic pollutants. In this study, Oreochromis niloticus were caught at three different sites in Al-Hassa irrigation channels, namely Al-Jawhariya, Um-Sabah and Al-Khadoud. The histological changes in gills and liver were detected microscopically and evaluated with semi-quantitative analyses. Also, heavy metals have been determined in the water samples in these sites. Results showed that all sites were polluted by different kinds of heavy metals. Cd and Pb were mostly detected at concentrations above the WHO reference values. Meanwhile, various histopathological abnormalities were observed in gills and liver of fish specimens. In the gill filaments, cell proliferation, lamellar cell hyperplasia, lamellar fusion, lifting of the respiratory epithelium, and the presence of aneurysmal areas were observed. In the liver, there was vacuolization of the hepatocytes, sinusoidal congestion, necrosis of the parenchyma tissue, nuclear pyknosis, eosinophilic hepatocellular degeneration, pigment accumulation, an increase in the number and size of melanomacrophage centers. Liver tumors with severe chronic inflammation were occasionally found in fish at Al-Khadoud area (first-time report). The histological lesions were comparatively most severe in the liver. Despite heavy metals assessment did not show marked differences among sites, histopathological biomarkers indicated that the surveyed fish are living under stressful environmental conditions. So, we suggest use those biomarkers in future monitoring of aquatic systems.

The impact of an oil spill on organs of bream Abramis brama in the Po River

An oil spill into the River Lambro occurred on 23 February 2010 and reached the Po River the following day. Breams captured here on 1 March 2010, along with a sample from a control site, were examined by light and electron microscopy. The main affected organs were skin and gill with slight or no damage to liver, kidney, and intestine. The gills exhibited lamellar aneurisms, fusion of secondary lamellae, edema with epithelial lifting, mucous cell hypertrophy, and mucus hypersecretion. Significantly higher mucous cell density was observed in the skin of exposed fish. Histochemical staining revealed that acid glycoconjugates were prevalent in epidermal mucous cells in the exposed Abramis brama, whereas neutral and mixed glycoconjugates were dominant in the control fish. Rodlet cells were significantly more abundant in the kidney of exposed fish and showed ultrastructural differences compared to controls. These histopathologic effects were indicators of chemical stress due to exposure to oil. The present study is one of the first which explores the acute effects of this incident and makes part of a few reports focused on freshwater oil spill.

Histologic, immunologic and endocrine biomarkers indicate contaminant effects in fishes of the Ashtabula River

The use of fish as sentinels of aquatic ecosystem health is a biologically relevant approach to environmental monitoring and assessment. We examined the health of the Ashtabula River using histologic, immunologic, and endocrine biomarkers in brown bullhead (BB; Ameiurus nebulosus) and largemouth bass (Micropterus salmoides) and compared fish collected from a reference site (Conneaut Creek). Seasonal analysis was necessary to distinguish differences in fish between the two rivers. Overall BB from the Ashtabula River had a lower condition factor and significantly more macrophage aggregates than those from the reference site. Reduced bactericidal and cytotoxic-cell activity was observed in anterior kidney leukocytes from both BB and largemouth bass from the Ashtabula River. Lower plasma thyroxine and triiodo-L-thyronine in both species in the Ashtabula River indicated disruption of the thyroid axis. Differences in physiological biomarker responses were supported by body burden chemical concentrations when data were analyzed on a seasonal basis. The use of two fish species added a level of rigor that demonstrated biological effects were not exclusive to a single species. The results provide strong evidence that contaminants have affected fish in the Ashtabula River, a Great Lakes Area of Concern, and provide a baseline by which to evaluate remediation activities.

Laser ablation ICP-MS Co-localization of mercury and immune response in fish

Mercury (Hg) contamination is a global issue with implications for both ecosystem and human health. In this study, we use a new approach to link Hg exposure to health effects in spotted gar (Lepisosteus oculatus) from Caddo Lake (TX/LA). Previous field studies have reported elevated incidences of macrophage centers in liver, kidney, and spleen of fish with high concentrations of Hg. Macrophage centers are aggregates of specialized white blood cells that form as an immune response to tissue damage, and are considered a general biomarker of contaminant toxicity. We found elevated incidences of macrophage centers in liver of spotted gar and used a new technology for ecotoxicology studies, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), to colocalize aggregates and Hg deposits within the tissue architecture. We conclude that Hg compromises the health of spotted gar in our study and, perhaps, other fish exposed to elevated concentrations of Hg.

Histo-cytological responses of Dicentrarchus labrax (L.) following mercury exposure

This work deals with the damaging effects of mercury (Hg concentrations 251, 355, 501 microgl(-1)) on the structure and ultrastructure of gills, liver, intestine and kidney of farmed European sea bass (Dicentrarchus labrax L., 1758) acutely treated for 24 and 48 h. The histoarchitecture of the gills of exposed fish was highly modified due to severe oedema, telangiectasia and secondary lamellar fusion. In hepatocytes and enterocytes hydropic cell swelling, alterations to the endoplasmic reticulum and mitochondria were noted, in addition to an abundance of myelinoid bodies which were frequently encountered following treatment. In the intestine and renal tubules of exposed European sea bass, rodlet cells (RCs) displayed ultrastructural modifications. Statistical analyses were conducted on the number and the size of selected cell types and structures. Following exposure to mercury for 24 and 48 h, the number of chloride cells, RCs and macrophage aggregates were found to have increased significantly in the gills, the intestine and the head kidney.

Mercury toxicity in livers of northern pike (Esox lucius) from Isle Royale, USA

Many laboratory studies have documented that mercury can be toxic to fish, but it is largely unknown if mercury is toxic to fish in their natural environments. The objective of our study was to investigate the toxic effects of mercury on northern pike (Esox lucius) at Isle Royale, Michigan. In 124 northern pike from eight inland lakes, concentrations of total mercury in skin-on fillets ranged from 0.069 to 0.622 microg/g wet mass (wet wt). Concentrations of total mercury in livers increased exponentially compared with concentrations in fillets, to a maximum of 3.1 microg/g wet wt. Methylmercury constituted a majority of the mercury in livers with total mercury concentrations <0.5 microg/g wet wt, but declined to 28-51% of the mercury in livers with total mercury concentrations >0.5 microg/g wet wt. Liver color (absorbance at 400 nm) varied among northern pike and was positively related to liver total mercury concentration. The pigment causing variation in liver color was identified as lipofuscin, which results from lipid peroxidation of membranous organelles. An analysis of covariance revealed lipofuscin accumulation was primarily associated with mercury exposure, and this association obscured any normal accumulation from aging. We also documented decreased lipid reserves in livers and poor condition factors of northern pike with high liver total mercury concentrations. Our results suggest (i) northern pike at Isle Royale are experiencing toxicity at concentrations of total mercury common for northern pike and other piscivorous fish elsewhere in North America and (ii) liver color may be useful for indicating mercury exposure and effects in northern pike at Isle Royale and possibly other aquatic ecosystems and other fish species.

Mercury concentrations in salmonids from western U.S. National Parks and relationships with age and macrophage aggregates

Mercury accumulation in aquatic foodwebs and its effects on aquatic biota are of growing concern both for the health of the fish and the piscivores that prey upon them. This is of particular concern for western U.S. National Parks because it is known that mountainous and Arctic areas are sinks for some contaminants. The Western Airborne Contaminants Assessment Project seeks, in part, to ascertain mercury concentrations and evaluate effects of contaminants on biota in 14 lakes from 8 National Parks or Preserves. In this paper we report that mercury has accumulated to concentrations in troutthat may negatively impact some piscivorous wildlife, indicating potential terrestrial ecosystem effects. Additionally, we show that mercury concentrations increase with age in 4 species of trout, providing evidence of bioaccumulation. Finally, we demonstrate that mercury is associated with tissue damage in the kidney and spleen, as indicated by increases in macrophage aggregates. This finding suggests that mercury, and possibly other contaminants, are Macrophage aggregates suggests that mercury, a negatively affecting the trout that inhabit these remote and protected ecosystems. Our results indicate that mercury is indeed a concern for the U.S. National Parks, from an organismic and potentially an ecosystem perspective.

Biomarkers of contaminant exposure in Northern Pike (Esox lucius) from the Yukon River Basin, Alaska

As part of a larger investigation, northern pike (n = 158; Esox lucius) were collected from ten sites in the Yukon River Basin (YRB), Alaska, to document biomarkers and their correlations with organochlorine pesticide (total p,p'-DDT, total chlordane, dieldrin, and toxaphene), total polychlorinated biphenyls (PCBs), and elemental contaminant (arsenic, cadmium, copper, lead, total mercury, selenium, and zinc) concentrations. A suite of biomarkers including somatic indices, hepatic 7-ethoxyresorufin O-deethylase (EROD) activity, vitellogenin concentrations, steroid hormone (17B- ustradiol and 16-kebtestosteront) concentrations, splenic macrophage aggregates (MAs), oocyte atresia, and other microscopic anomalies in various tissues were documented in YRB pike. Mean condition factor (0.50 to 0.68), hepatosomatic index (1.00% to 3.56%), and splenosomatic index (0.09% to 0.18%) were not anomalous at any site nor correlated with any contaminant concentration. Mean EROD activity (0.71 to 17.51 pmol/min/mg protein) was similar to basal activity levels previously measured in pike and was positively correlated with selenium concentrations (r = 0.88, P < 0.01). Vitellogenin concentrations in female (0.09 to 5.32 mg/mL) and male (<0.0005 to 0.097 mg/mL) pike were not correlated with any contaminant, but vitellogenin concentrations >0.01 mg/mL in male pike from multiple sites indicated exposure to estrogenic compounds. Mean steroid hormone concentrations and percent oocyte atresia were not anomalous in pike from any YRB site. Few site differences were significant for mean MA density (1.86 to 6.42 MA/mm(2)), size (812 to 1481 microm(2)), and tissue occupied (MA-%; 0.24% to 0.75%). A linear regression between MA-% and total PCBs was significant, although PCB concentrations were generally low in YRB pike (< or =63 ng/g), and MA-% values in female pike (0.24% to 0.54%) were lower than in male pike (0.32% to 0.75%) at similar PCB concentrations. Greater numbers of MAs were found as zinc concentrations increased in YRB female pike, but it is unlikely that this is a causative relationship. Histological abnormalities observed in gill, liver, spleen, and kidney tissues were not likely a result of contaminant exposure but provide information on the general health of YRB pike. The most common histologic anomalies were parasitic infestations in various organs and developing nephrons and nephrocalcinosis in posterior kidney tissues. Overall, few biomarker responses in YRB pike were correlated with chemical contaminant concentrations, and YRB pike generally appeared to be healthy with no site having multiple anomalous biomarker responses.

Cellular alterations in different organs of European sea bass Dicentrarchus labrax (L.) exposed to cadmium

Specimens of farmed European sea bass (Dicentrarchus labrax L., 1758) were exposed to different cadmium (Cd) concentrations (4.47, 5.63, 7.08 and 8.91 mg l(-1)) for 24 and 48 h. The effects of Cd on numbers of some cell types and structures (i.e., chloride cells, CCs; macrophage aggregates, MAs; rodlet cells, RCs) and on structure and ultrastructure of the main organs (gill, liver, intestine, kidney) were studied with routine process for light and transmission electron microscopy. Following cadmium exposure, the numbers of branchial CCs as well as intestinal and renal RCs increased significantly within 24h. Increase in metal concentration did not affect the magnitude of the numerical increment of the aforementioned cells. Moreover, in treated fish (24 and 48 h) the numbers of MAs in both head kidney and spleen were significantly higher than in control conspecifics, whilst the global area of MAs was less influenced by the acute treatment. In exposed sea bass, all the examined organs exhibited cellular modifications which appeared time- and dose-dependent. The gills showed telangectasia, lamellar fusion, oedema, epithelial lifting and leukocyte infiltration. In the liver, kidney and intestine acute cell swelling and vacuolization were common. Ultrastructurally the alterations observed frequently in hepatocytes, tubular epithelial cells and enterocytes included presence of numerous myelinoid bodies, damaged mitochondria, dilatation of endoplasmic reticulum, high number of lysosomes and autophagolysosomes. In intestinal and kidney tubular epithelia of treated fish, rodlet cells displayed some anomalies like dilatation of nuclear envelope, cytoplasmic vacuolization, presence of myelinoid bodies, rodlets degeneration and extensive discharge activity.

Preliminary morphometrics of spleen and kidney macrophage aggregates in clinically normal blue gourami Trichogaster trichopterus and freshwater angelfish Pterophyllum scalare

Macrophage aggregate (MA) morphometry and pigment composition are believed to be dependent on the species, age, and health status of the fish. The aim of this study was to characterize a "normal" morphometry baseline of spleen and kidney MAs in blue gourami Trichogaster trichopterus and freshwater angelfish Pterophyllum scalare. Three size-classes of clinically normal fish were analyzed. Blue gourami and freshwater angelfish were obtained from three local ornamental fish farms; for each size-class, 10 fish from each farm were analyzed. Hematoxylin- and eosin-stained tissue sections were analyzed by light microscopy at 100x magnification and an image analysis program. The percentage of tissue occupied by MAs, MA size, and MA number were calculated on three arbitrarily selected fields of view from each spleen and kidney. In clinically normal blue gourami, increases in the percentage of tissue occupied by MAs and in MA size were associated with an increase in fish size, but in clinically normal angelfish no correlation was observed. Furthermore, in angelfish, a high variability in MA morphometry was observed, even among fish from the same sample group. In both species, a significant difference in the value of the morphometric parameters was observed among farms. Because iridoviruses inhibit macrophage activity and (possibly) proliferation, MAs in 25 clinical cases of iridovirus-infected blue gourami were analyzed. Preliminary data indicate that in iridovirus-infected blue gourami, there is a decrease in MA size and MA number compared with those of healthy fish.

Mercury levels and liver pathology in feral fish living in the vicinity of a mercury cell chlor-alkali factory

Twenty-three barbels (Barbus graellsii), 30 bleaks (Alburnus alburnus) and 4 sediment samples were collected from four areas of the Cinca River (NE Spain), upstream and downstream of a mercury cell chlor-alkali plant. Mercury concentration in sediments downstream of the plant was about 25 times higher than the concentration upstream. Mercury levels in the muscle and liver of barbels downstream of the chlor-alkali plant were 10 and 30 times higher than those upstream. The average mercury concentration in the muscle and liver of barbels downstream of the factory was 1.48 and 1.78mg/kgw.w., with maximal concentrations of 2.43 and 3.64mg/kgw.w, respectively. Liver/muscle ratio of mercury was significantly higher in barbels sampled downstream of the factory. Bleak showed a similar pattern, with a significantly higher whole-body mercury concentration downstream of the chlor-alkali plant. Nevertheless, a progressive decrease in mercury concentration downstream of the impact area was found in bleak, but not in barbel. Histopathological analysis showed that fish downstream of the factory had significantly higher prevalence of liver pathologies (p<0.05). Although there are no specific histopathological markers of mercury exposure, barbels with the highest Hg levels in the liver also showed the most severe pathologies, and the processes found in these barbels were consistent with the pro-oxidant effect of heavy metals.

Bioaccumulation of mercury in muscle tissue of fish in the Elbe River (Czech Republic): multispecies monitoring study 1991-1996

The study monitored mercury (Hg) contamination of fish muscle tissue at 13 geographical sites that can be regarded as crucial points for an ecotoxicological assessment of the Czech Republic section of the Elbe River. The descriptive part of the study was primarily aimed at comparative evaluation of the Hg load during the period 1991-1996. The conclusions were supported by multivariate statistical analyses of the content of Hg in the muscle tissue of 1251 fish belonging to 23 species with four dominant indicator species: Perca fluviatilis (n=163), Abramis brama (n=173), Rutilus rutilus (n=148), and Leuciscus cephalus (n=166). Considering data from 3- to 5-year-old fish, significantly increased contamination was detected in typical predators compared to the other fish species in all sites (P<0.001). On the other hand, omnivorous and planctivorous species were ranked as the least sensitive for Hg pollution. Perch appeared to be the most contaminated species in the sample with muscle Hg concentration in the range of 0.840-1.398 mg Hg kg(-1). Although less contaminated than perch, muscle contamination of bream sensitively separated differently contaminated sites; the highest load ranged from 0.368 to 0.543 mg Hg kg(-1). Time-related comparison of sampling campaigns revealed no significant trend changes, in either sediment samples or fish tissue. Thus, the analyses documented an evidently rather stabilized total Hg pollution in the Elbe River environment. Multivariate multispecies analyses found the age of analyzed individuals and the feeding strategy of a given species as the most important, however mutually interactive, covariates for Hg accumulation in muscle tissue. The analyses revealed decreasing sensitivity of older predator individuals to differentiate highly and moderately contaminated sites. Benthophagous species mostly kept their discrimination capacity toward contaminated sites in all age categories, with the exception of bream that was rather linked to the pattern typical for predator species. The unclear position of omnivorous species, represented namely by roach, corresponded with their weak bioindicator power, mainly in the young age categories.

Melano-macrophage centres and their role in fish pathology

Melano-macrophage centres, also known as macrophage aggregates, are distinctive groupings of pigment-containing cells within the tissues of heterothermic vertebrates. In fish they are normally located in the stroma of the haemopoietic tissue of the spleen and the kidney, although in amphibians and reptiles, and some fish, they are also found in the liver. They may also develop in association with chronic inflammatory lesions elsewhere in the body and during ovarian atresia. In higher teleosts, they often exist as complex discrete centres, containing lymphocytes and macrophages, and may be primitive analogues of the germinal centres of lymph nodes. Melano-macrophage centres usually contain a variety of pigments, including melanins, and these increase in range and volume in older fish or in the presence of cachectic disease. Melano-macrophage centres act as focal depositories for resistant intracellular bacteria, from which chronic infections may develop. Iron capture and storage in haemolytic diseases appears to be a primary function, but antigen trapping and presentation to lymphocytes, sequestration of products of cellular degradation and potentially toxic tissue materials, such as melanins, free radicals and catabolic breakdown products are among other functions that have been ascribed. Recent work suggests that they are a site of primary melanogenesis rather than mere storage. Melano-macrophage centres increase in size or frequency in conditions of environmental stress and have been suggested as reliable biomarkers for water quality in terms of both deoxygenation and iatragenic chemical pollution.