Melano-macrophage centres and their role in fish pathology

Morpho-histology of head kidney of female catfish Heteropneustes fossilis: seasonal variations in melano-macrophage centers, melanin contents and effects of lipopolysaccharide and dexamethasone on melanins

In the catfish Heteropneustes fossilis, the anterior kidney is a hemopoietic tissue which surrounds the adrenal homologues, interrenal (IR) and chromaffin tissues corresponding to the adrenal cortical and adrenal medulla of higher mammals. The IR tissue is arranged in cell cords around the posterior cardinal vein (PCV) and its tributaries and secretes corticosteroids. The chromaffin tissue is scattered singly or in nests of one or more cells around the epithelial lining of the PCV or blood capillaries within the IR tissue. They are ferric ferricyanide-positive. Leukemia-inhibitory factor (LIF)-like reactivity was noticed in the lining of the epithelium of the IR cell cords and around the wall of the PCV and blood capillaries. No staining was observed in the hemopoietic cells. IL-1β- and TNF-α-like immunoreactivity was seen in certain cells in the hemopoietic tissue but not in the IR region. Macrophages were identified with mammalian macrophage-specific MAC387 antibodies and are present in the hemopoietic mass but not in the IR tissue. Pigments accumulate in the hemopoietic mass as melano-macrophage centers (MMCs) and are PAS-, Schmorl's- and Perls'-positive. The pigments contain melanin (black), hemosiderin (blue) and lipofuscin/ceroid (oxidized lipid, yellowish tan), as evident from the Perls' reaction. The MMCs were TUNEL-positive as evident from FITC fluorescence, indicating their apoptotic nature. The MMCs showed significant seasonal variation with their density increasing to the peak in the postspawning phase. Melanins were characterized spectrophotometrically for the first time in fish anterior kidney. The predominant form is pheomelanin (PM), followed by eumelanin (EM) and alkali-soluble melanin (ASM). Melanins showed significant seasonal variations with the level low in the resting phase and increasing to the peak in the postspawning phase. Under in vitro conditions, lipopolysaccharide (10 µg/mL) treatment increased significantly the levels of PM and EM levels both at 16 and at 32 h and the ASM level at 32 h. On the other hand, the synthetic glucocorticoid dexamethasone (100 nM) decreased significantly the levels of EM, PM and ASM time-dependently. The results indicate that the anterior kidney is an important site of immune-endocrine interaction.

Heavy metal mediated innate immune responses of the Indian green frog, Euphlyctis hexadactylus (Anura: Ranidae): Cellular profiles and associated Th1 skewed cytokine response

Immune cell and cytokine profiles in relation to metal exposure though much studied in mammals has not been adequately investigated in amphibians, due mainly to lack of suitable reagents for cytokine profiling in non-model species. However, interspecies cross reactivity of cytokines permitted us to assay levels of IFNγ, TNFα, IL6 and IL10in a common anuran, the Indian green frog (Euphlyctis hexadactylus), exposed to heavy metals (Cd, Cr, Cu, Zn and Pb, at ~5ppm each) under field and laboratory settings in Sri Lanka. Enumeration of immune cells in blood and melanomacrophages in the liver, assay of serum and hepatic cytokines, and Th1/Th2 cytokine polarisation were investigated. Immune cell counts indicated overall immunosuppression with decreasing total WBC and splenocyte counts while neutrophil/lymphocyte ratio increased with metal exposure, indicating metal mediated stress. Serum IL6 levels of metal exposed frogs reported the highest (~9360pg/mL) of all cytokines tested. Significantly elevated IFNγ production (P<0.05) was evident in heavy metal exposed frogs. Th1/Th2 cytokine ratio in both serum and liver tissue homogenates was Th1 skewed due to significantly higher production of pro-inflammatory cytokines, IFNγ in serum and TNFα in the liver (P<0.01).Metal mediated aggregations of melanomacrophages in the liver were positively and significantly (P<0.05) correlated with the hepatic expression of TNFα, IL6 and IL10 activity. Overall, Th1 skewed response may well be due to oxidative stress mediated nuclear factor κ-light chain enhancer of activated B cells (NFκB) which enhances the transcription of pro-inflammatory cytokines. Xenobiotic stress has recently imposed an unprecedented level of threat to wildlife, particularly to sensitive species such as amphibians. Therefore, understanding the interactions between physiological stress and related immune responses is fundamental to conserve these environmental sentinels in the face of emerging eco-challenges.

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

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

Anguilla anguilla intestinal immune response to natural infection with Contracaecum rudolphii A larvae

The European eel, Anguilla anguilla, is a major warm-water fish species cultured in North and South Europe. Seventy-one A. anguilla collected between 2010 and 2015 from the Comacchio lagoons were examined. Fish were infected and damaged by larvae (L3) of the nematode Contracaecum rudolphii A, which were encapsulated within the thickness of the intestinal wall and within the external visceral peritoneum (serosa). Conspicuous granulomas, visible at sites of infection, were arranged in a trilayer, formed by a series of concentric whorls. The cells involved in the immune response and their distribution in the granuloma layers were assessed by immunohistochemical, immunofluorescence, and ultrastructural techniques. The outer part of the granuloma contained macrophages, macrophage aggregates, and mast cells (MCs) scattered among fibroblasts. This layer was vascularized, with degranulation of MCs occurring in close proximity to the capillaries. The middle layer was rich in MCs and fibroblasts. The inner layer, closest to the parasite larva, consisted mainly of dark epithelioid cells, some of which were necrotic. Non-necrotic epithelioid cells formed desmosomes between themselves or with fibroblasts. Within the granulomas, numerous cells of different types were positive to proliferative cell nuclear antigen antibody, indicating a high degree of cellular proliferation around the larvae.

Immunohistochemical study of inducible nitric oxide synthase and tumour necrosis factor alpha response in turbot (Scophthalmus maximus) experimentally infected with Aeromonas salmonicida subsp. salmonicida

Aeromonas salmonicida subsp. salmonicida represents one of the major threats in aquaculture, especially in salmonid fish and turbot farming. In order to fight bacterial infections, fish have an immune system composed by innate and specific cellular and humoral elements analogous to those present in mammals. However, innate immunity plays a primordial role against bacterial infections in teleost fish. Among these non-specific mechanisms, the production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) pathway and the tumour necrosis factor-alpha (TNFα) produced by mononuclear phagocytes, are two of the main immune effectors to eliminate bacterial pathogens. In this study, the distribution and kinetic of iNOS and TNFα-producing cells of kidney and spleen of turbot experimentally inoculated with A. salmonicida was assessed by immunohistochemistry. In control and challenged fish, individual iNOS(+) and TNFα(+) cells, showing a similar pattern of distribution, were detected. In challenged fish, the number of immunoreactive cells was significantly increased in the evaluated organs, as well as the melanomacrophage centres showed variable positivity for both antigens. These results indicate that A. salmonicida induced an immune response in challenged turbot, which involved the increase of the activity of iNOS and TNFα in the leukocytic population from kidney and spleen.

NMR-based metabolomics reveals compartmental metabolic heterogeneity in liver of Arctic char (Salvelinus alpinus)

Metabolomics involves systematic study of low-molecular-mass metabolites in cells, tissues, or biofluids and is nowadays widely applied to characterize the physiological status of aquatic organisms under a set of conditions, such as disease and toxin exposure. Liver, an important metabolic center in the fish body, is often used for metabolomics analysis. Compared with the whole fish liver, the proportion of liver sample needed for metabolomics analysis is relatively small. The homogeneity of metabolites in liver is thus an important issue, especially for comparative studies and biomarker discovery. This study examined the homogeneity of the metabolic profile in liver of Arctic char (Salvelinus alpinus (L., 1758)) using a NMR-based metabolomics approach. For the analysis, whole liver samples were cut into four parts along the direction of gall bladder and at right angles to this, and metabolites in each part of the liver were extracted and analyzed by multivariate and univariate data analyses. Although the multivariate model was not significant due to variation within the data, the metabolic differences in polar portion of liver extract between the parts were seen, indicating non-homogeneity of Arctic char liver. Therefore, when sampling fish liver for further metabolomics studies, this heterogeneity should be taken into consideration.

B-cell activating CpG ODN 1668 enhance the immune response of Pacific red snapper (Lutjanus peru) exposed to Vibrio parahaemolitycus

B-class CpG ODN 1668 is known to possess clear immunostimulatory properties. In this study, we investigated the potential ability of CpG ODN 1668 to enhance the immune response of Pacific red snapper exposed to Vibrio parahaemolyticus. Four different treatments were evaluated in Pacific red snapper: (1) stimulatory CpG ODN 1668, (2) stimulatory CpG ODN 1668 and V. parahaemolyticus, (3) exposure only to V. parahaemolyticus and (4) PBS. Samples were taken at 24, 72, 168 and 240 h of stimulation/infection. The results show that intraperitoneal injection of CpG-ODN 1668 enhanced the anti-protease, superoxide dismutase and catalase activities in serum. CpG ODN 1668 upregulated TLR9 and IgM gene expression in head-kidney, intestine and skin, with higher expression in head-kidney. A higher correlation was observed between TLR9 and IgM in head-kidney and intestine. Finally, no histopathological damages were observed in fish stimulated with CpG ODN 1668. In contrast, melanomacrophages-like structures were present in higher numbers in infected fish. Taken together, these results indicate that CpG ODN 1668 activates innate immune response and upregulate the TLR9 and IgM-mediated immune response. These results may be exploited for the control of Vibriosis in farmed Pacific red snapper.

Nematode infection in liver of the fish Gymnotus inaequilabiatus (Gymnotiformes: Gymnotidae) from the Pantanal Region in Brazil: pathobiology and inflammatory response

BACKGROUND

A survey on endoparasitic helminths from freshwater fishes in the Pantanal Region (Mato Grosso do Sul, Brazil) revealed the occurrence of third-larval stage of the nematode Brevimulticaecum sp. (Heterocheilidae) in most organs of Gymnotus inaequilabiatus (Gymnotidae) also known by the local name tuvira. The aim of the present study was to examine Brevimulticaecum sp.-infected tuvira liver at the ultrastructural level and clarify the nature of granulomas and the cellular elements involved in the immune response to nematode larvae.

METHODS

Thirty-eight adult specimens of tuvira from Porto Morrinho, were acquired in January and March 2016. Infected and uninfected liver tissues were fixed and prepared for histological and ultrastructure investigations.

RESULTS

The prevalence of infection of tuvira liver by the nematode larvae was 95 %, with an intensity of infection ranging from 4 to 343 larvae (mean ± SD: 55.31 ± 73.94 larvae per liver). In livers with high numbers of nematode larvae, almost entire hepatic tissue was occupied by the parasites. Hepatocytes showed slight to mild degenerative changes and accumulation of pigments. Parasite larvae were surrounded by round to oval granulomas, the result of focal host tissue response to the infection. Each granuloma was typically formed by three concentric layers: an outer layer of fibrous connective tissue with thin elongated fibroblasts; a middle layer of mast cells entrapped in a thin fibroblast-connective mesh; and an inner layer of densely packed epithelioid cells, displaying numerous desmosomes between each other. Numerous macrophage aggregates occurred in the granulomas and in the parenchyma.

CONCLUSIONS

Our results in tuvira showed that the larvae were efficiently sequestered within the granulomas, most of the inflammatory components were confined within the thickness of the granuloma, and the parenchyma was relatively free of immune cells and without fibrosis. Presumably this focal encapsulation of the parasites permits uninfected portions of liver to maintain its functions and allows the survival of the host.

Cutaneous malignant melanoma in a Haller's round ray Urobatis halleri

Multiple black raised nodular masses were noted on the dorsal surface of an adult male Haller's round ray Urobatis halleri. Biopsy of 2 masses was performed, and histopathology revealed proliferative sheets of melanocytes exhibiting mild anisocytosis and anisokaryosis, supporting a diagnosis of malignant melanoma. Approximately 2 mo following the biopsy procedure, the round ray became acutely anorexic and was found dead in its enclosure. A full necropsy was performed, and tissues were submitted for histopathology. The black raised nodular masses again exhibited histologic features of a melanoma. In addition to the nodular masses present, multiple flat areas of increased pigmentation were also present throughout the course of the case and were not suggestive of neoplasia histologically. The transformation of benign to malignant neoplasia has been well described in other species and may have played a role in the development of multiple tumors in this case.

Gene expression profiling in melanised sites of Atlantic salmon fillets

Black spots, which deteriorate quality of Atlantic salmon fillets represent a significant problem for commercial aquaculture. These areas are characterized with accumulation of melanomacrophages, occasional formation of granulomas and substitution of skeletal muscle with connective tissue. A number of possible causative agents have been suggested including vaccination and infection with piscine reovirus (PRV). We report transcriptome profiling of melanised foci with oligonucleotide DNA microarrays. Analyses revealed a multitude of differentially expressed genes associated with melanogenesis, metabolic changes and formation of scar. The immune profile was characterized with inflammation, preferential activation of classical complement pathway, MHCII and helper T cells combined with strong B cells responses and massive induction of immunoglobulins; innate antiviral responses were relatively weak in sharp contrast to PRV-caused heart and skeletal muscle inflammation and other viral infections. A panel of immune genes with specific activation in dark spots was found, most up-regulated were CD209-like lectin (44-fold) and prostaglandin reductase (11-fold). Further, RNA sequencing was performed on the same material to search for the presence of putative pathogens. Transcripts of prokaryotic rRNA with exclusive or preferential location in black spots were found. Results suggest mild chronic inflammation initiated with trauma, bacterial or viral infection followed by sustained immune responses to opportunistic microorganisms as a realistic scenario of dark spots formation.

Alterations in histology and antioxidant defense system in the testes of the lake Van fish (Alburnus tarichi Güldenstädt, 1814)

Recent reports have demonstrated gonadal abnormalities in the Lake Van fish (Alburnus tarichi) from Lake Van caused by increasing pollution. In the present study, the fish was collected from an area of Lake Van receiving mainly sewage treatment plant effluent at prespawning period (April) and from a river (Karasu) which is close to the polluted area of the lake and where the fish migrates at spawning period (May). Collected specimens were examined for testicular alterations, gonadosomatic index (GSI), condition factor (CF), and antioxidant defense system biomarkers based on comparison with a reference lake (Erçek) and a reference freshwater inlet (Memedik River). Histological examinations of the testes of fish from the polluted area and the connected river showed various alterations consisting of macrophage aggregates, vacuolation, pyknosis, germ cell degeneration, seminiferous tubule dilation, disorganization of tubules, reduced spermatozoa, and fibrosis. A lower GSI and CF were also observed. Moreover, alterations in the antioxidant system biomarkers were determined in the testis tissues of fish from the Lake Van and Karasu River, indicating oxidative stress. These results suggest that the abnormalities in the testes are causally related to the increased oxidative stress, and pollution in Lake Van may have adversely affected the reproductive health of the lake Van fish.

Melanomacrophage centers in Clarias gariepinus as an immunological biomarker for toxicity of silver nanoparticles

Although there are many applications of silver nanoparticles (Ag-NPs) in human activities, there is still little known about their potential environmental toxicity, particularly to fish. In the present study, the effects of Ag-NPs on African catfish (Clarias gariepinus) were studied using melanomacrophage centers as immunohistological biomarkers. Fish were exposed to 25 mg/L, 50 mg/L and 75 mg/L 100-nm Ag-NPs. We studied the effects on the size and number of melanomacrophage centers in all target tissues. Many histopathological alterations in those tissues were observed. The histological changes were represented as dislocation of the epithelium, dilatation of central veins associated with inflammatory leukocytic infiltration, necrosis, and pyknotic nuclei of hepatocytes. There was shrinkage of Malpighian corpuscles, dislocation of nuclei of convoluted tubules, cellular degeneration, and dispersed infiltration of leukocytes in kidney tissue. Examination of spleen sections after exposure to Ag-NPs showed rupture within the red pulp and hemorrhage, dislocation of nuclei, accumulation of inflammatory leukocytes, and congestion in blood vessels. In conclusion, exposure to Ag-NPs induced alterations in tissues, suggesting a possible increase in oxidative stress in those tissues.

Impact of treated wastewater reuse and floods on water quality and fish health within a water reservoir in an arid climate

Treated wastewater (TWW) reuse for agricultural irrigation is a well-established approach to coping with water shortages in semi-arid and arid environments. Recently, additional uses of TWW have emerged, including streamflow augmentation and aquatic ecosystem restoration. The purpose of the current study was to evaluate the water quality and fish health, in an artificial reservoir located in an arid climate (the Yeruham Reservoir, Israel), which regularly receives TWW and sporadic winter floods. The temporal distribution of water levels, nutrients and organic micropollutants (OMPs) were measured during the years 2013-2014. OMPs were also measured in sediment and fish tissues. Finally, the status of fish health was evaluated by histopathology. Water levels and quality were mainly influenced by seasonal processes such as floods and evaporation, and not by the discharge of TWW. Out of 16 tested OMPs, estrone, carbamazepine, diclofenac and bezafibrate were found in the reservoir water, but mostly at concentrations below the predicted no-effect concentration (PNEC) for fish. Concentrations of PCBs and dioxins in fish muscle and liver were much lower than the EU maximal permitted concentrations, and similar to concentrations that were found in food fish in Israel and Europe. In the histopathological analysis, there were no evident tissue abnormalities, and low to moderate infection levels of fish parasites were recorded. The results from the Yeruham Reservoir demonstrated a unique model for the mixture effect between TWW reuse and natural floods to support a unique stable and thriving ecosystem in a water reservoir located in an arid region. This type of reservoir can be widely used for recreation, education, and the social and economic development of a rural environment, such as has occurred in the Yeruham region.

Flutamide effects on morphology of reproductive organs and liver of Neotropical Anura, Rhinella schneideri

Water contamination is one of the factors influencing the decline of amphibians. Flutamide is an antiandrogenic medicine that occurs as water contaminant. This compound especially affects the reproductive organs, but it can also show hepatotoxic effects. The Bufonidae family has a peculiar organ named Bidder's organ, considered by some authors as a rudimentary ovary, but capable to respond to some external stimuli. This study investigated flutamide effects on testes and Bidder's organ germ cells, liver pigmentation, and sexual hormones levels in Rhinella schneideri males. We randomly divided 15 males in three groups (N=5): two groups were injected with flutamide, at 1 and 5mg/kg, while the control group received only mineral oil, for 7days. After euthanasia, blood samples were collected and the organs were sent to histological routine. In the testes, both treatments caused an increase in spermatogonia and spermatocytes, and a decrease in spermatozoa and locular area. In the Bidder's organ, the final diplotene oocytes increased, but the initial diplotene, degrading and atresic oocytes reduced in both treatments. The lipofuscin in the Bidder's organ was not affected. In the liver, melanin and lipofuscin increased only for the 1mg/kg flutamide treatment. The 5mg/kg treatment did not affect the liver. Serum testosterone and estradiol levels did not vary compared with the control group. This compound has antiandrogenic activity, which can affect the spermatogenetic process. The decrease in degrading and atresic Bidderian oocytes indicated that flutamide could stimulate the organ, retarding the degradation processes. The increase in liver melanin, which has protective role, and lipofuscin, a sign of degradation, indicates that flutamide cause hepatotoxic effects. So we conclude that flutamide negatively affects the testes, especially by reducing the sperm area, and the liver, inducing cell degradation and producing protective responses. Furthermore, the compound encourages lower degradation rates of the Bidder's organ germ cells.

Adverse health effects and histological changes in white sturgeon (Acipenser transmontanus) exposed to dietary selenomethionine

It has been shown that selenium (Se) released to the aquatic environment can have devastating effects on local wildlife. White sturgeon (Acipenser transmontanus) have a life history particularly susceptible to contaminants, and their protection is of interest as they are culturally and economically important, and many populations are classified as endangered. During the present 72-d dietary study, multiple signs of decreased health and Se lethality were observed. Juvenile white sturgeon were given diets containing 1.4 μg, 5.6 μg, 22.4 μg, or 104.4 μg selenomethionine/g food (dry mass). Selenium accumulated in muscle and liver tissue in a dose-dependent manner. Edema causing exophthalmos developed within 15 d and 23 d, and lethal effects occurred in 54% and 22% of fish in the high- and medium-dose groups, respectively. Growth and hepatosomatic index were significantly lower in the high-dose group, which also had a high incidence of food avoidance. Histology of the liver revealed a dose-dependent increase in melanomacrophage aggregates and decrease of energy stores, which indicated toxicity. These results indicate that white sturgeon are susceptible to the effects of Se accumulation over relatively short time periods. This stresses the need for continued sturgeon research and studies looking into the environmental fate and regulation of released Se. Environ Toxicol Chem 2016;35:1741-1750. © 2015 SETAC.

Levamisole Activates Several Innate Immune Factors in Scophthalmus Maximus (L.) (Teleostei)

Levamisole, originally synthesized as an anti-helminthic, has been widely used in human and veterinary medicine as an immunomodulator or adjuvant. However, data on its use in fish are scarce, and no information is available for turbot. To study the effects of levamisole treatment on the innate immune system of juvenile turbot, two different doses (D1=500 mg/kg; D2=250 mg/kg dry food) were orally administered for 2 weeks and samplings were performed at −10, 14, 28, 49 and 77 days post treatment (p.t.). Biometrical, haematological, histological and immunological data were obtained. Specific growth rate was higher in the medicated groups than in the control (C), but the difference was statistically significant only for D1 fish at day 49 p.t. The leucocytes/trombocytes ratio was significantly higher in D1 than in C fish at 14 days p.t., but decreased subsequently. At most samplings, the percentage of the circulating lymphocytes was lower and that of the progranulocytes was higher in the medicated fish than in the C ones. The percentage offish with high haemotopoietic activity in the kidney was clearly higher in D1 and D2 fish than in C ones at some sampling points. The respiratory burst activity of blood leucocytes was significantly higher in D1 fish than in C ones in all samplings, except at day 77 p.t. when control fish experienced a rebound effect. In all medicated fish, an initial increase of such activity was observed, followed by a further decrease. Their serum peroxidases followed a contrary pattern, with a decrease in the second sampling and a subsequent and non-significant recovery, a situation also observed for serum lysozyme and complement. Therefore, oral levamisole treatment actually affects some turbot immune factors, although stimulation or depression can occur depending on the considered factor and the administered dose. These results point out the interest of further studies on the mechanisms involved in the levamisole action for its adequate use as immunomodulator.

Mobilisation and dysfunction of haematopoietic stem/progenitor cells after Listonella anguillarum infection in ayu, Plecoglossus altivelis

Haematopoietic stem/progenitor cells (HSPCs) can mobilise into blood and produce immune cell lineages following stress. However, the homeostasis and function of HSPCs after infection in teleosts are less well known. Here, we report that Listonella anguillarum infection enhances HSPC mobilisation and reduces their differentiation into myeloid cells in ayu (Plecoglossus altivelis), an aquacultured teleost in East Asia. We established a colony-forming unit culture (CFU-C) assay to measure HSPCs using conditioned medium from peripheral blood mononuclear cells stimulated with phytohaemagglutinin. The number of CFU-Cs decreased in the head kidney and increased in the blood and spleen of ayu infected with L. anguillarum. HSPC mobilisation after L. anguillarum infection was mediated by norepinephrine. Furthermore, HSPCs from ayu treated with L. anguillarum lipopolysaccharide (LPS) showed defective myeloid differentiation and could no longer rescue L. anguillarum-infected ayu. HSPC expansion was suppressed after L. anguillarum infection or its LPS treatment in vitro. These results reveal a link between HSPC regulation and pathogen infection in teleosts.

Duplex PCR assay and in situ hybridization for detection of Francisella spp. and Francisella noatunensis subsp. orientalis in red tilapia

Conventional isolation and identification based on phenotypic characteristics is challenging with the highly fastidious, intracellular bacterium Francisella noatunensis subsp. orientalis (Fno). Here, we developed a duplex PCR method for simultaneous detection of the Francisella genus and Fno in one PCR reaction and an in situ hybridization method for paraffin section based diagnosis of Fno. The PCR results showed genus- and species-specific bands (1140 and 203 bp) from Fno but only one genus-specific band (1140 bp) from F. noatunensis subsp. noatunensis. Sensitivity of the duplex PCR assay revealed a detection limit of 20 to 200 fg genomic DNA (~10 to 100 genome equivalents) depending on DNA template extraction methods. The newly developed duplex PCR assay could be used to detect Fno from clinically sick fish exhibiting signs of visceral granulomas and would also be able to detect Fno infection in naturally diseased fish without symptoms of francisellosis, indicating potential application for diagnosis of field samples. The in situ hybridization assay using Fno species-specific probe revealed positive signals in multiple organs including the spleen, liver, kidney, gills and intestine of infected fish.

Subcellular distribution of trace elements and liver histology of landlocked Arctic char (Salvelinus alpinus) sampled along a mercury contamination gradient

We sampled landlocked Arctic char (Salvelinus alpinus) from four lakes (Small, 9-Mile, North, Amituk) in the Canadian High Arctic that span a gradient of mercury contamination. Metals (Hg, Se, Tl, and Fe) were measured in char tissues to determine their relationships with health indices (relative condition factor and hepatosomatic index), stable nitrogen isotope ratios, and liver histology. A subcellular partitioning procedure was employed to determine how metals were distributed between potentially sensitive and detoxified compartments of Arctic char livers from a low- and high-mercury lake (Small Lake and Amituk Lake, respectively). Differences in health indices and metal concentrations among char populations were likely related to differences in feeding ecology. Concentrations of Hg, Se, and Tl were highest in the livers of Amituk char, whereas concentrations of Fe were highest in Small and 9-Mile char. At the subcellular level we found that although Amituk char had higher concentrations of Tl in whole liver than Small Lake char, they maintained a greater proportion of this metal in detoxified fractions, suggesting an attempt at detoxification. Mercury was found mainly in potentially sensitive fractions of both Small and Amituk Lake char, indicating that Arctic char are not effectively detoxifying this metal. Histological changes in char livers, mainly in the form of melano-macrophage aggregates and hepatic fibrosis, could be linked to the concentrations and subcellular distributions of essential or non-essential metals.

Persistent organic pollutants (POPs) in fish with different feeding habits inhabiting a shallow lake ecosystem

The occurrence of persistent organic pollutants (POPs) in the environment can affect organisms inhabiting aquatic systems, in particular shallow lakes that are vulnerable to environmental stressors. This study aimed to assess POPs accumulation and changes at histological and physiological levels in tissues of three fish species with different trophic habits. Gills, brain, muscle, liver and gonads of Odontesthes bonariensis, Oligosarcus jenynsii and Cyphocharax voga were collected from the shallow lake La Peregrina, located in an agricultural area from Argentina. In addition, contaminant levels in surface water (SW), suspended particulate matter (SPM) and bottom sediments (BS) were assessed. Histological lesions were evaluated in fish tissues and levels of vitellogenin (VTG) were assessed in plasma of male fish in order to correlate these alterations with the presence of POPs in the environment. Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined by GC-ECD. Biotic and abiotic samples showed the same POPs distribution pattern: OCPs>PCBs>PBDEs. Although tissue distribution of OCPs was species-specific, muscle showed the lowest levels in all species. The most abundant contaminants were endosulfans, suggesting their widespread use in the area. O. bonariensis showed the highest endosulfans levels in liver (184.2-219ngg(-1)wet w), which was associated with the high SPM levels considering this species is a filter feeder. The occurrence of PCBs and PBDEs shows the ubiquity of these pollutants in the area. Histological lesions in gills and liver of O. bonariensis and O. jenynsii, might be related with the high levels of endosulfans in these organs. The detection of VTG in males warns about a possible exposure to estrogenic compounds in the environment. In conclusion, the simultaneous exposure of fish to multiple environmental pollutants leads to different alterations, so measures should be taken in order to prevent their occurrence and toxic effects.

Heavy Metals and Histopathological Alterations in Salminus franciscanus (Lima & Britski, 2007) (Pisces: Characiformes) in the Paraopeba River, Minas Gerais, Brazil

Cu, Pb, Cd, Zn, Cr, Hg, and Fe in the liver, spleen and muscle, of the fish Salminus franciscanus, from two sections of Paraopeba River, highly affected by anthropogenic influences, was detected in levels above those recommended for human consumption. Positive correlations between fish size and levels of metals were detected for Cd, Pb, Hg, and Zn. In the livers, areas with lipid accumulation and pigmented macrophages were also observed, as was fibrosis of the spleen in the parenchymal area through the presence of pigmented macrophages. The diameter of vitellogenic follicles was less and the frequency of atresia was higher in fish from section A. Thus, our study showed that beyond the risk to the population that eats S. franciscanus from the Paraopeba River, we should also consider the risk to the conservation of this species, since histopathological changes were detected in target organs and in some reproductive parameters.

Persistence of external signs in Pacific herring Clupea pallasii Valenciennes with ichthyophoniasis

The progression of external signs of Ichthyophonus infection in Pacific herring Clupea pallasii Valenciennes was highly variable and asynchronous after intraperitoneal injection with pure parasite preparations; however, external signs generally persisted through the end of the study (429 days post-exposure). Observed signs included papules, erosions and ulcers. The prevalence of external signs plateaued 35 days post-exposure and persisted in 73-79% of exposed individuals through the end of the first experiment (147 days post-exposure). Among a second group of infected herring, external signs completely resolved in only 10% of the fish after 429 days. The onset of mortality preceded the appearance of external signs. Histological examination of infected skin and skeletal muscle tissues indicated an apparent affinity of the parasite for host red muscle. Host responses consisted primarily of granulomatous inflammation, fibrosis and necrosis in the skeletal muscle and other tissues. The persistence and asynchrony of external signs and host response indicated that they were neither a precursor to host mortality nor did they provide reliable metrics for hindcasting on the date of exposure. However, the long-term persistence of clinical signs in Pacific herring may be useful in ascertaining the population-level impacts of ichthyophoniasis in regularly observed populations.

Hepatic effects of the clomazone herbicide in both its free form and associated with chitosan-alginate nanoparticles in bullfrog tadpoles

The use of agrochemicals in agriculture is intense and most of them could be carried out to aquatic environment. Nevertheless, there are only few studies that assess the effects of these xenobiotics on amphibians. Clomazone is an herbicide widely used in rice fields, where amphibian species live. Thus, those species may be threatened by non-target exposure. However, nanoparticles are being developed to be used as a carrier system for the agrochemicals. Such nanoparticles release the herbicide in a modified way, and are considered to be more efficient and less harmful to the environment. The aim of this study was to comparatively evaluate the effect of clomazone in its free form and associated with nanoparticles, in the liver of bullfrog tadpoles (Lithobates catesbeianus) when submitted to acute exposure for 96 h. According to semi-quantitative analysis, there was an increase in the frequency of melanomacrophage centres, in the accumulation of eosinophils and in lipidosis in the liver of experimental groups exposed to clomazone - in its free form and associated with nanoparticles - in comparison with the control group, and the nanotoxicity of chitosan-alginate nanoparticles. The increase of melanomacrophage centres in all exposed groups was significant (P < 0.0001) in comparison to control group. Therefore, the results of this research have shown that exposure to sublethal doses of the herbicide and nanoparticles triggered hepatic responses. Moreover, these results provided important data about the effect of the clomazone herbicide and organic nanoparticles, which act as carriers of agrochemicals, on the bullfrog tadpole liver.

Fish innate immunity against intestinal helminths

Most individual fish in farmed and wild populations are infected with parasites. Upon dissection of fish, helminths from gut are often easily visible. Enteric helminths include several species of digeneans, cestodes, acanthocephalans and nematodes. Some insights into biology, morphology and histopathological effects of the main fish enteric helminths taxa will be described here. The immune system of fish, as that of other vertebrates, can be subdivided into specific and aspecific types, which in vivo act in concert with each other and indeed are interdependent in many ways. Beyond the small number of well-described models that exist, research focusing on innate immunity in fish against parasitic infections is lacking. Enteric helminths frequently cause inflammation of the digestive tract, resulting in a series of chemical and morphological changes in the affected tissues and inducing leukocyte migration to the site of infection. This review provides an overview on the aspecific defence mechanisms of fish intestine against helminths. Emphasis will be placed on the immune cellular response involving mast cells, neutrophils, macrophages, rodlet cells and mucous cells against enteric helminths. Given the relative importance of innate immunity in fish, and the magnitude of economic loss in aquaculture as a consequence of disease, this area deserves considerable attention and support.

Bioaccumulation of mercury, cadmium, zinc, chromium, and lead in muscle, liver, and spleen tissues of a large commercially valuable catfish species from Brazil

The increasing amounts of heavy metals entering aquatic environments can result in high accumulation levels of these contaminants in fish and their consumers, which pose a serious risk to ecosystems and human health. We investigated the concentrations of mercury (Hg), cadmium (Cd), zinc (Zn), chromium (Cr), and lead (Pb) in muscle, liver, and spleen tissues of Pseudoplatystoma corruscans specimens collected from two sites on the Paraopeba River, Brazil. The level of heavy metals concentrations in the tissues was often higher in viscera (i.e. liver and spleen) than in muscle, and thus, the viscera should not be considered for human consumption. Correlations between metal concentrations and fish size were not significant. Although the levels of muscle bioaccumulation of Hg, Cd, Zn, Cr, and Pb, generally do not exceed the safe levels for human consumption, the constant presence of heavy metals in concentrations near those limits considered safe for human consumption, is a reason for concern, and populations who constantly consume fish from polluted rivers should be warned. Our findings also indicate that in a river network where certain areas are connected to other areas with high rates of environmental pollutants, people should be cautious about the regular consumption of fish, even when the fish consumed are caught in stretches of the basin where contamination levels are considered low, since many of the freshwater fish with high commercial value, such as the catfish surubim, are migratory.

Development and characterization of a cell line from tilapia head kidney with melanomacrophage characteristics

A novel cell line THK, derived from the tilapia head kidney, was developed and characterized. The THK cell line comprised fibroblastoid cells that markedly proliferated in Leibovitz L-15 medium containing 2%-15% fetal bovine serum (FBS) at 20 °C-35 °C. Cell proliferation was dependent on the FBS concentration, and the optimal temperature for proliferation ranged between 25 °C and 30 °C. THK cells were characterized for the presence of phagocytic activity, acid phosphatase, alkaline phosphatase, α-naphthyl acetate esterase, lipofuscin, and tyrosinase. Transcripts of CD33, CD53, CD82, CD205, macrophage colony stimulating factor receptor, GATA2, and GATA3 that are specific for leucocytes or monocytes/macrophages or both were detected in the THK cells through PCR. However, THK cells lacked for CD83, a specific marker for dendritic cells. The results indicated that the fibroblastoid THK cells were melanomacrophage-related progenitors. PCR revealed that the THK cells exhibited the transcripts of toll-like receptor 1 (TLR1), TLR2, TLR3, and CD200, of which concern with immunity as well as the transcripts of vascular endothelial growth factor receptor 3, angiomotin, and angiopoietin-like protein 2 that associate with angiogenesis regulation and macrophage proliferation. THK cells were subcultured more than 90 times and can be useful for investigating the development and functioning of the teleostean innate immune system.

In vivo studies on hepato-renal impairments in freshwater fish Cyprinus carpio following exposure to sublethal concentrations of sodium cyanide

Reactive oxygen species is an inevitable composite of aerobic systems that could channelize their lethality by imparting oxidative stress under a stressful environment. Cyanide is an important environmental toxicant that could be responsible in the resulting detrimental health issues of aquatic fauna. The present effort investigates the possibilities of hepato-renal damage in freshwater fish Cyprinus carpio following exposure to sublethal concentrations of sodium cyanide (NaCN). Fish were exposed to 0.1 mg/L of NaCN for 10 days (E1) and 20 days (E2) and were further subjected to recovery for 14 days (R) in NaCN-free medium. Liver tissue exhibited a significant decline in activity of catalase, superoxide dismutase, glutathione peroxidase, and glutathione S-transferase enzymes in exposed fish, unlike in control (C). Subsequent levels of lipid peroxidation elevation at 'E1' and 'E2' suggested oxidative damage to hepatocytes. This was further confirmed through a histopathological evaluation which indicated important findings like lymphocytic infiltration and necrosis in liver and tubular and glomerular degeneration in renal organ. The investigation suggests biochemical and histopathological alterations in fish following exposure to NaCN. Nevertheless, fish upon the recovery period were known to exhibit incomplete recuperation which was indicated by partial restoration tendencies under biochemical and histopathological factions. The study clearly implicated the role of NaCN in emphasizing its toxicity to C. carpio, further suggesting lack of recovery transition at a limited tenure of 14 days. The study might contribute in the course of regulatory surveillance and monitoring of aquatic bodies and may also reflect the possibilities of NaCN contamination during aquaculture practices. Graphical Abstract ᅟ.

Ecological relevance of biomarkers in monitoring studies of macro-invertebrates and fish in Mediterranean rivers

Mediterranean rivers are probably one of the most singular and endangered ecosystems worldwide due to the presence of many endemic species and a long history of anthropogenic impacts. Besides a conservation value per se, biodiversity is related to the services that ecosystems provide to society and the ability of these to cope with stressors, including climate change. Using macro-invertebrates and fish as sentinel organisms, this overview presents a synthesis of the state of the art in the application of biomarkers (stress and enzymatic responses, endocrine disruptors, trophic tracers, energy and bile metabolites, genotoxic indicators, histopathological and behavioural alterations, and genetic and cutting edge omic markers) to determine the causes and effects of anthropogenic stressors on the biodiversity of European Mediterranean rivers. We also discuss how a careful selection of sentinel species according to their ecological traits and the food-web structure of Mediterranean rivers could increase the ecological relevance of biomarker responses. Further, we provide suggestions to better harmonise ecological realism with experimental design in biomarker studies, including statistical analyses, which may also deliver a more comprehensible message to managers and policy makers. By keeping on the safe side the health status of populations of multiple-species in a community, we advocate to increase the resilience of fluvial ecosystems to face present and forecasted stressors. In conclusion, this review provides evidence that multi-biomarker approaches detect early signs of impairment in populations, and supports their incorporation in the standardised procedures of the Water Frame Work Directive to better appraise the status of European water bodies.

Identification and expression modulation of a C-type lectin domain family 4 homologue that is highly expressed in monocytes/macrophages in rainbow trout (Oncorhynchus mykiss)

The C-type lectin domain containing (CLEC) receptors including CD209 are expressed in vivo by monocytes, monocyte-derived macrophages and dendritic cells and by in vitro generated monocyte-derived cells. This paper reports the cloning and sequencing of a lectin molecule, CLEC4T1, in rainbow trout that is a homologue of the CLEC4 family. The expression pattern of the CLEC4T1 was investigated in vivo after infection with a bacterial pathogen and in cultured macrophages after modulation with microbial mimics. Trout CLEC4T1 was highly expressed in spleen and head kidney following infection with Yersinia ruckeri. Expression could also be induced in macrophage cultures by LPS but not by Poly I:C, and suggests that the regulation of CLEC4T1 expression in trout varies according to the nature of the stimulant. A polyclonal CLEC4T1 antibody was generated and validated by Western blotting for use in evaluation of CLEC4T1(+) cells by flow cytometry analysis. Freshly isolated adherent trout head kidney cultures, potentially containing macrophages and dendritic cell precursors, showed an increase of CLEC4T1(+) cells (assessed by flow cytometry) upon stimulation with recombinant interleukin-4/13A. The results suggest that CLEC4T1 is a useful marker for further characterisation of monocyte derived antigen presenting cells in fish.

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

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

The chromium accumulation and its physiological effects in juvenile rockfish, Sebastes schlegelii, exposed to different levels of dietary chromium (Cr(6+)) concentrations

Juvenile rockfish (mean length 13.7±1.7 cm, and mean weight 55.6±4.8 g) were exposed for 4 weeks with the different levels of dietary chromium (Cr(6+)) at 0, 30, 60, 120 and 240 mg/kg. The profile of chromium in the tissues of rockfish is dependent on the exposure periods and chromium concentration. After 4 weeks, the order of chromium accumulation in tissues was liver>kidney>spleen>intestine>gill>muscle. The dietary chromium exposure decreased the growth rate and hepatosomatic index of rockfish. The major hematological findings were significant decrease in the red blood cell (RBC) count, hematocrit (Ht) value, and hemoglobin (Hb) concentration exposed to ≥120 mg/kg chromium concentrations. The dietary chromium exposure (≥120 mg/kg) led to notable increase in glucose, cholesterol, glutamic oxalate transaminase (GOT), and glutamic pyruvate transaminase (GPT) in plasma, whereas there was no considerable change in calcium, magnesium, total protein, and alkaline phosphatase (ALP). The results indicated that the dietary chromium exposure to rockfish can induce significant chromium accumulation in the specific tissues, inhibition of growth, and hematological alterations.

Linking Ah receptor mediated effects of sediments and impacts on fish to key pollutants in the Yangtze Three Gorges Reservoir, China - A comprehensive perspective

The Three Gorges Reservoir (TGR), created in consequence of the Yangtze River's impoundment by the Three Gorges Dam, faces numerous anthropogenic impacts that challenge its unique ecosystem. Organic pollutants, particularly aryl hydrocarbon receptor (AhR) agonists, have been widely detected in the Yangtze River, but only little research was yet done on AhR-mediated activities. Hence, in order to assess effects of organic pollution, with particular focus on AhR-mediated activities, several sites in the TGR area were examined applying the "triad approach". It combines chemical analysis, in vitro, in vivo and in situ investigations to a holistic assessment. Sediments and the benthic fish species Pelteobagrus vachellii were sampled in 2011/2012, respectively, to identify relevant endpoints. Sediment was tested in vitro with the ethoxyresorufin-O-deethylase (EROD) induction assay, and in vivo with the Fish Embryo Toxicity Test and Sediment Contact Assay with Danio rerio. Activities of phase I (EROD) and phase II (glutathione-S-transferase) biotransformation enzymes, pollutant metabolites and histopathological alterations were studied in situ in P. vachellii. EROD induction was tested in vitro and in situ to evaluate possible relationships. Two sites, near Chongqing and Kaixian city, were identified as regional hot-spots and further investigated in 2013. The sediments induced in the in vitro/in vivo bioassays AhR-mediated activities and embryotoxic/teratogenic effects - particularly on the cardiovascular system. These endpoints could be significantly correlated to each other and respective chemical data. However, particle-bound pollutants showed only low bioavailability. The in situ investigations suggested a rather poor condition of P. vachellii, with histopathological alterations in liver and excretory kidney. Fish from Chongqing city exhibited significant hepatic EROD induction and obvious parasitic infestations. The polycyclic aromatic hydrocarbon (PAH) metabolite 1-hydroxypyrene was detected in bile of fish from all sites. All endpoints in combination with the chemical data suggest a pivotal role of PAHs in the observed ecotoxicological impacts.

Administration of a Polyphenol-Enriched Feed to Farmed Sea Bass (Dicentrarchus labrax L.) Modulates Intestinal and Spleen Immune Responses

Farmed fish are exposed to a continuous antigenic pressure by microbial and environmental agents, which may lead to a condition of chronic inflammation. In view of the notion that polyphenols, largely contained in fruits and vegetables, are endowed with antioxidant and anti-inflammatory activities, farmed sea bass (Dicentrarchus labrax L.) have been administered with red grape polyphenol-enriched feed. Polyphenols were extracted from the seeds of Canosina Nero di Troia Vitis vinifera and mixed with conventional feed at two different concentrations (100 and 200 mg/kg, resp.). Fish samples collected at days 223 and 273, respectively, were evaluated for intestinal and spleen cytokine release as well as for spleen macrophage (MØ) and melanomacrophage center (MMC) areas and distribution. Data will show that in treated fish decrease of intestinal interleukin- (IL-) 1β and IL-6 and increase of splenic interferon- (IFN-) γ occur. On the other hand, in the spleen reduction of MØ number seems to parallel increase in MMCs. Collectively, these data suggest that polyphenol-administered sea bass generate lower levels of intestinal proinflammatory cytokines, while producing larger amounts of spleen IFN-γ, as an expression of a robust and protective adaptive immune response. Increase of MMCs corroborates the evidence for a protective spleen response induced by feed enriched with polyphenols.

Effects of adjuvant Montanide™ ISA 763 A VG in rainbow trout injection vaccinated against Yersinia ruckeri

Enteric redmouth disease (ERM) caused by the fish pathogen Yersinia ruckeri is a major threat to freshwater production of rainbow trout (Oncorhynchus mykiss) throughout all life stages. Injection vaccination of rainbow trout against Y. ruckeri infection has been shown to confer better protection compared to the traditionally applied immersion vaccination. It may be hypothesized, based on experience from other vaccines, that adjuvants may increase the protective level of ERM injection vaccines even more. Controlled comparative vaccination studies have been performed to investigate effects of the oil adjuvant Montanide™ ISA 763 A VG (Seppic) when added to an experimental Y. ruckeri bacterin (containing both biotype 1 and 2 of serotype O1). A total of 1000 fish with mean weight 19 g was divided into five different groups (in duplicated tanks 2 × 100 fish per group) 1) non-vaccinated control fish (NonVac), 2) fish injected with a commercial vaccine (AquaVac(®) Relera™) (ComVac), 3) fish injected with an experimental vaccine (ExpVac), 4) fish injected with an experimental vaccine + adjuvant (ExpVacAdj) and 5) fish injected with adjuvant alone (Adj). Injection of the experimental vaccine (both adjuvanted and non-adjuvanted) induced a significantly higher antibody (IgM) level, increased occurrence of IgM(+) cells in spleen tissue and significant up-regulation of several immune genes. Additional experiments using a higher challenge dosage suggested an immune enhancing effect of the adjuvant as the challenge produced 100% mortality in the NonVac group, 60% mortality in both of ComVac and Adj groups and only 13 and 2.5% mortalities in the ExpVac and the ExpVacAdj groups, respectively.

What the Erythrocytic Nuclear Alteration Frequencies Could Tell Us about Genotoxicity and Macrophage Iron Storage?

Erythrocytic nuclear alterations have been considered as an indicative of organism’s exposure to genotoxic agents. Due to their close relationship among their frequencies and DNA damages, they are considered excellent markers of exposure in eukaryotes. However, poor data has been found in literature concerning their genesis, differential occurrence and their life span. In this study, we use markers of cell viability; genotoxicity and cellular turn over in order to shed light to these events. Tilapia and their blood were exposed to cadmium in acute exposure and in vitro assays. They were analyzed using flow cytometry for oxidative stress and membrane disruption, optical microscopy for erythrocytic nuclear alteration, graphite furnace atomic absorption spectrometry for cadmium content in aquaria water, blood and cytochemical and analytical electron microscopy techniques for the hemocateretic aspects. The results showed a close relationship among the total nuclear alterations and cadmium content in the total blood and melanomacrophage centres area, mismatching reactive oxygen species and membrane damages. Moreover, nuclear alterations frequencies (vacuolated, condensed and blebbed) showed to be associated to cadmium exposure whereas others (lobed and bud) were associated to depuration period. Decrease on nuclear alterations frequencies was also associated with hemosiderin increase inside spleen and head kidney macrophages mainly during depurative processes. These data disclosure in temporal fashion the main processes that drive the nuclear alterations frequencies and their relationship with some cellular and systemic biomarkers.

Relation between increased oxidative stress and histological abnormalities in the ovaries of Alburnus tarichi in Lake Van, Turkey

Recent studies have shown reproductively arrested gonad development in female Alburnus tarichi (Güldenstädt, 1814) (Cyprinidae) from the eastern coastline of Lake Van, Turkey, due to increasing pollution. In the reproductively arrested females (RAF), oocytes were developmentally blocked and arrested at the previtellogenic stage and gonadosomatic indices (GSI) were very low, while reproductively non-arrested females (RNF) found at the same site displayed relatively normal ovarian development and higher GSI. The present study investigated various oxidative stress biomarkers in the ovaries of RAF and RNF collected from a polluted site at Lake Van at the mid-vitellogenic phase, compared with reference fish from a non-polluted site (Lake Erçek). Ovarian total protein content, biometric indices, and histology were also evaluated. The oxidative stress biomarkers used were levels of lipid peroxidation (LPO) and glutathione (GSH), and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione-S-transferase (GST). High levels of LPO and GSH and activities of SOD, GPx and GST were found in the ovaries of RAF compared with the reference fish. GSH content and activities of GPx and GST were also higher in the RNF. The total protein content and biometric indices decreased significantly in the RAF compared with the RNF and reference fish. The histology of the ovaries revealed atresia, melano-macrophage centers, encapsulated follicle cysts, and severe fibrosis in the RAF. The results of this study suggest that abnormalities in the ovaries of A. tarichi are causally related to increased oxidative stress as a result of pollution.

Uncaria tomentosa increases growth and immune activity in Oreochromis niloticus challenged with Streptococcus agalactiae

Cat's claw (Uncaria tomentosa) is an Amazon herb using in native cultures in Peru. In mammals, it has been described several effects of this herb. However, this is the first report of its use on the diet of fish. The aim of this study was to determinate the effect of this plant on the growth and immune activity in Oreochromis niloticus. Nile tilapia (81.3 ± 4.5 g) were distributed into 5 groups and supplemented with 0 (non-supplement fish), 75, 150, 300, and 450 mg of U. tomentosa.kg(-1) of diet for a period of 28 days. Fish were inoculated in the swim bladder with inactivated Streptococcus agalactiae and samples were taken at 6, 24, and 48 h post inoculation (HPI). Dose dependent increases were noted in some of the evaluated times of thrombocytes and white blood cells counts (WBC) in blood and exudate, burst respiratory activity, lysozyme activity, melanomacrophage centers count (MMCs), villi length, IgM by immunohistochemistry in splenic tissue, and unexpectedly on growth parameters. However, dietary supplementation of this herb did not affect red blood cells count (RBC), hemoglobin, and there were no observed histological lesions in gills, intestine, spleen, and liver. The current results demonstrate for the first time that U. tomentosa can stimulate fish immunity and improve growth performance in Nile tilapia.

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.

Occurrence of immune cells in the intestinal wall of Squalius cephalus infected with Pomphorhynchus laevis

A sub-population of 34 specimens of chub, Squalius cephalus, was sampled from the River Brenta (Northern Italy) and examined for ecto- and endo-parasites. Pomphorhynchus laevis (Acanthocephala) was the only enteric helminth encountered. Immunofluorescence and ultrastructural studies were conducted on the intestines of chub. Near the site of parasite's attachment, mucous cells, mast cells (MCs), neutrophils and rodlet cells (RCs) were found to co-occur within the intestinal epithelium. The numbers of mucous cells, MCs and neutrophils were significantly higher in infected fish (Mann-Whitney U test, p < 0.05). Dual immunofluorescence staining with the lectin Dolichos Biflorus Agglutinin (DBA) and the macrophage-specific MAC387 monoclonal antibody, with parallel transmission electron microscopy, revealed that epithelial MCs often made intimate contact with the mucous cells. Degranulation of a large number of MCs around the site of the acanthocephalan's attachment and in proximity to mucous cells was also documented. MCs and neutrophils were abundant in the submucosa. Immune cells of the intestinal epithelium have been described at the ultrastructural level and their possible functions and interactions are discussed.

Using immune responses in Euryglossa orientalis and Acanthopagrus latus from Persian Gulf as indicators of environmental health

One hundred and twenty sole (Euryglossa orientalis) and yellowfin seabream (Acanthopagrus latus) fishes were captured from five stations at the Musa Creek (northwest of the Persian Gulf): petrochemical, Gaffari, Majidieh, Ghazaleh, and Zangi stations. Blood was collected from the caudal vein as samples. Tissue samples were also taken from the spleen and head kidney, and tissue sections were prepared according to routine histological methods. The concentrations of Hg, Pb, Zn, Cu, and Cd in the water and sediment samples were measured. The most tissue changes, the maximum concentration of C3 and C4, and the minimum amount of serum antibacterial activity and lysosomal membrane stability in fish collected near a petrochemical station were determined. This station is adjacent to the Imam Khomeini Petrochemical Complex, and it receives highly contaminated effluents from this complex. The fish collected from the Zangi station exhibited the highest lysosomal membrane stability and antibacterial activity and the lowest amounts of C3 and C4.

Piscine orthoreovirus (PRV) in red and melanised foci in white muscle of Atlantic salmon (Salmo salar)

Melanised focal changes (black spots) are common findings in the white skeletal muscle of seawater-farmed Atlantic salmon (Salmo salar). Fillets with melanised focal changes are considered as lower quality and cause large economic losses. It has been suggested that red focal changes (red spots) precede the melanised focal changes. In the present work, we examined different populations of captive and wild salmon for the occurrence of both types of changes, which were investigated for the presence of different viruses by immunohistochemistry and RT-qPCR. The occurrence of red or melanised foci varied significantly between the populations, from none in wild fish control group, low prevalence of small foci in fish kept in in-house tanks, to high prevalence of large foci in farm-raised salmon. Large amounts of Piscine orthoreovirus (PRV) antigen were detected in all foci. No other viruses were detected. Red focal changes contained significantly higher levels of PRV RNA than apparently non-affected areas in white muscle of the same individuals. Some changes displayed a transient form between a red and melanised pathotype, indicating a progression from an acute to a chronic manifestation. We conclude that PRV is associated with the focal pathological changes in the white muscle of farmed Atlantic salmon and is a premise for the development of focal melanised changes.

Towards science-based sediment quality standards-Effects of field-collected sediments in rainbow trout (Oncorhynchus mykiss)

Sediments can act as long-term sinks for environmental pollutants. Within the past decades, dioxin-like compounds (DLCs) such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) have attracted significant attention in the scientific community. To investigate the time- and concentration-dependent uptake of DLCs and PAHs in rainbow trout (Oncorhynchus mykiss) and their associated toxicological effects, we conducted exposure experiments using suspensions of three field-collected sediments from the rivers Rhine and Elbe, which were chosen to represent different contamination levels. Five serial dilutions of contaminated sediments were tested; these originated from the Prossen and Zollelbe sampling sites (both in the river Elbe, Germany) and from Ehrenbreitstein (Rhine, Germany), with lower levels of contamination. Fish were exposed to suspensions of these dilutions under semi-static conditions for 90 days. Analysis of muscle tissue by high resolution gas chromatography and mass spectrometry and of bile liquid by high-performance liquid chromatography showed that particle-bound PCDD/Fs, PCBs and PAHs were readily bioavailable from re-suspended sediments. Uptake of these contaminants and the associated toxicological effects in fish were largely proportional to their sediment concentrations. The changes in the investigated biomarkers closely reflected the different sediment contamination levels: cytochrome P450 1A mRNA expression and 7-ethoxyresorufin-O-deethylase activity in fish livers responded immediately and with high sensitivity, while increased frequencies of micronuclei and other nuclear aberrations, as well as histopathological and gross pathological lesions, were strong indicators of the potential long-term effects of re-suspension events. Our study clearly demonstrates that sediment re-suspension can lead to accumulation of PCDD/Fs and PCBs in fish, resulting in potentially adverse toxicological effects. For a sound risk assessment within the implementation of the European Water Framework Directive and related legislation, we propose a strong emphasis on sediment-bound contaminants in the context of integrated river basin management plans.

Use of histopathology and elemental accumulation in different organs of two benthophagous fish species as indicators of river pollution

The bottom feeding fish species have a good potential to be used for assessments of pollution, as they are under pressure from pollutants from both water and sediments. In this study, the level of similarity of histopathological responses to pollution in gills and liver between barbel (Barbus barbus) and sterlet (Acipenser ruthenus) from the Danube River was assessed, and compared with elemental concentrations in their gills, liver, and muscle. Results indicate that the detected metal concentrations were likely cause of different tissue responses in gills and liver of the two investigated fish species. Statistical analysis indicated a clear differentiation of the two species based on elemental concentrations and the level of histopathological changes in gills and liver. Metal concentrations exceeded maximum acceptable concentrations in a number of analyzed specimens, which indicates the importance of this type of monitoring. Results indicate that barbel is a better indicator for specific, rather narrow sites, whereas sterlet is a better indicator of larger (longer) water current segments. Obtained information could be of importance for both scientists and fishery and water management authorities working on the development of water monitoring programs.

Immunolocalization of tumor necrosis factor alpha in turbot (Scophthalmus maximus, L.) tissues

Tumor necrosis factor alpha (TNFα) is a cytokine involved in a broad spectrum of cellular and organismal responses. Its main function, as a potent pro-inflammatory mediator, has been demonstrated in numerous teleost species and there are many reports on the modulation of TNFα gene expression under pathological conditions. Nevertheless, there is still scarce knowledge about the tissue distribution and type of cells that express this cytokine in fish species, which would help to further investigate its biological activities. These studies are hampered by the lack of molecular markers for teleost that hinder the development of morphological techniques, like immunohistochemistry. The aim of this work was to develop an immunohistochemical technique for the detection of TNFα in paraffin-embedded organs from healthy turbot (Scophthalmus maximus), an economically-important marine fish species. A commercial anti-human TNFα antibody, whose specificity was confirmed by western blot analysis, was used. Immunoreactive cells were observed in higher numbers in the lymphohematopoietic organs, kidney, spleen and thymus, although TNFα-positive cells were also present in the digestive tract, liver, heart, gills and skin. Similarly to non-fish species, monocytes/macrophages appeared to be the main producers of this cytokine; nevertheless, the presence of immunoreactive rodlet cells in different tissues was also reported. The nature and distribution of the labeled cells appeared to be related with a strategic localization for defense response to antigenic challenge. The relative abundance of TNFα-positive cells in the lymphohematopoietic organs also suggests that this cytokine may have a broader role in the normal physiology of those organs. The immunohistochemical technique allowed the in-situ characterization of TNFα expression, representing a valid tool to investigate the immune response of turbot.

The role of melano-macrophage aggregates in the storage of mercury and other metals: an example from yelloweye rockfish (Sebastes ruberrimus)

Melano-macrophage aggregates, collections of specialized cells of the innate immune system of fish, are considered a general biomarker for contaminant toxicity. To elucidate further the relationship between macrophage aggregates and metals exposure, yelloweye rockfish (Sebastes ruberrimus), a long-lived species, were sampled from the east and west coasts of Prince of Wales Island, Alaska. Metals concentrations in livers (inorganic Hg, methyl mercury, Se, Ni, Cd, Cu, Zn) and spleens (inorganic Hg and methyl mercury) were determined, as well as their correlations with melano-macrophage aggregate area. Sections of liver tissue were analyzed by laser ablation-inductively coupled plasma-mass spectrometry to determine how metals were spatially distributed between hepatocytes and macrophage aggregates. The concentration of inorganic Hg in whole tissue was the best predictor of macrophage area in yelloweye livers and spleens. Macrophage aggregates had higher relative concentrations than most metals compared with the surrounding hepatocytes. However, not all metals were accumulated to the same degree, as evidenced by differences in the ratios of metals in macrophages compared with hepatocytes. Laser ablation data were corroborated with the results of X-ray synchrotron fluorescence imaging of a yelloweye liver section. Hepatic macrophage aggregates in yelloweye rockfish may play an important role in the detoxification and storage of Hg and other metals.

Evaluation of a high-EPA oil from transgenic Camelina sativa in feeds for Atlantic salmon (Salmo salar L.): Effects on tissue fatty acid composition, histology and gene expression

Currently, one alternative for dietary fish oil (FO) in aquafeeds is vegetable oils (VO) that are devoid of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFAs). Entirely new sources of n-3 LC-PUFA such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids through de novo production are a potential solution to fill the gap between supply and demand of these important nutrients. Camelina sativa was metabolically engineered to produce a seed oil (ECO) with > 20% EPA and its potential to substitute for FO in Atlantic salmon feeds was tested. Fish were fed with one of the three experimental diets containing FO, wild-type camelina oil (WCO) or ECO as the sole lipid sources for 7 weeks. Inclusion of ECO did not affect any of the performance parameters studied and enhanced apparent digestibility of individual n-6 and n-3 PUFA compared to dietary WCO. High levels of EPA were maintained in brain, liver and intestine (pyloric caeca), and levels of DPA and DHA were increased in liver and intestine of fish fed ECO compared to fish fed WCO likely due to increased LC-PUFA biosynthesis based on up-regulation of the genes. Fish fed ECO showed slight lipid accumulation within hepatocytes similar to that with WCO, although not significantly different to fish fed FO. The regulation of a small number of genes could be attributed to the specific effect of ECO (311 features) with metabolism being the most affected category. The EPA oil from transgenic Camelina (ECO) could be used as a substitute for FO, however it is a hybrid oil containing both FO (EPA) and VO (18:2n-6) fatty acid signatures that resulted in similarly mixed metabolic and physiological responses.