Kidney Of Fish Research Articles

Resveratrol relieves chlorothalonil-induced apoptosis and necroptosis through miR-15a/Bcl2-A20 axis in fish kidney cells

Chlorothalonil (CT) is a commonly used fungicide and its excessive application seriously threatens aquatic life and human health. Resveratrol (RSV) is a natural polyphenol and can be used as a therapeutic and preventive agent for the treatment of various diseases. To explore the toxic mechanism of CT exposure on fish kidney cell, as well as the alleviation effect of RSV, we established CT poisoning and/or RSV treatment fish kidney cell models. Ctenopharyngodon idellus kidney (CIK) cell line was treated with CT (5 μg/L) and/or RSV (10 μM) for 48 h. The results showed that CT exposure activated cytochromeP450s (CYPs) including CYP1A1, CYP1B1 and CYP1C, caused malondialdehyde (MDA) accumulation, inhibited glutathione (GSH) levels and glutathione peroxidase (GPX) activities, increased the expression of miR-15a and downregulated BCL2 and TNFα-induced protein 3 (TNFAIP3, A20), triggered mitochondrial pathway mediated apoptosis and receptor interacting serine/threonine kinase (RIP)-dependent necroptosis in CIK cells. However, cell death under CT exposure could be relieved by RSV treatment through inhibiting the expression of CYP1 family genes and restoring miR-15a/BCL2-A20 axis disorders. Overall, we conclude that RSV could relieve CT-induced apoptosis and necroptosis through miR-15a/Bcl2-A20 axis in CIK cells. These results enrich the toxicological mechanisms of the CT and confirm that RSV can be used as a potential antidote for CT poisoning.

Transcriptomic analysis of red-spotted grouper nervous necrosis virus infected Asian seabass Lates calcarifer (Bloch, 1790)

Red-spotted grouper nervous necrosis virus (RGNNV) has threatened aquaculture of the Asian seabass (Lates calcarifer) in many countries of the Asia-Pacific for decades. To understand the pathogenesis of RGNNV, a transcriptome analysis of the head kidney, a major fish lymphoid tissue which performs important immune functions and is involved in the hematopoiesis was undertaken. RNA from the head kidney of RGNNV infected fish was sequenced and compared RNA from uninfected control fish at two and 15-days post infection. Functional analysis revealed a number of differentially expressed genes implicated in autophagy (beclin-1 and inositol 1,4,5-trisphosphate receptor), superoxide production (cytochrome b-245 light chain, C3a anaphylatoxin chemotactic receptor and neutrophil cytosol factor 2-like), inflammation (leukocyte surface antigen CD53), antigen presentation (MHC class I alpha chain), antiviral activity (cholesterol 25-hydroxylase) and other immune functions (oxysterol-binding protein 1, dipeptidyl peptidase I, interleukin-5 receptor subunit alpha-like and tyrosine-protein kinase BTK). This is the first description of the change in L. calcarifer head kidney mRNA expression as a consequence of RGNNV infection and the information will serve as the rational basis for future investigations into the pathophysiology of NNV infection of fish.

Sublethal Toxicity of Organophosphate Pesticides and its Effect on Hematology Parameter, Histopatology Hematopoietic Organ of Silver Rasbora (Rasbora argyrotaenia)

Pesticides are pollutants that are found in rice fields and rivers. Pesticides that are often used by farmers in Indonesia in eradicating insects are organophosphate insecticides, where they can eradicate insects that are very toxic to fish due to strong neurotoxic substances that inhibit AchE (Acetylcholinesterase) activity. The research aims to examine the effect of organophosphate pesticides on hematology and histopathology of hematopoietic organs in silver rasbora fish. The research method used is an experimental method with a CRD. The parameters observed were hematology and histopathology hematopoietic organ (liver and kidney). The results of this study showed a hematological change in silver rasbora fish where there was a decrease in total erythrocytes (0,59±0,004) and hemoglobin (2,5±0,1) while total leukocytes increased (245,35±15,78). Also, there are differential changes in leukocytes, namely an increased in the number of monocytes (5±1) and neutrophils (24±3), but lymphocytes have decreased in number (72±1). The Histopathology of the fish liver also can found in this research, those damages that are found are erythrocyte infiltration, necrosis picnosis, and karyolysis. Histopathology of fish kidney also can found cloudy sweling, necrosis karyolysis and tubular necrosis.

Most abundant metabolites in tissues of freshwater fish pike-perch (Sander lucioperca)

Quantitative metabolomic analysis was performed for eleven tissues of freshwater fish pike-perch (Sander lucioperca), including gill, heart, liver, kidney, spleen, muscle, brain, milt, lens, aqueous (AH) and vitreous (VH) humors with the use of NMR spectroscopy. The absolute values of concentrations were determined for more than 65 most abundant metabolites in every tissue. It was found that from the metabolomic viewpoint, kidney and gill are the most similar tissues, while the metabolomic compositions of ocular tissues—lens, AH, and VH significantly differ from that of other tissues. The combinations of intracellular osmolytes and antioxidants are specific for every tissue. In particular, the concentration of antioxidant ovothiol A in the lens is much higher than in any other tissue, while the brain enjoys the elevated level of ascorbate. The most abundant osmolyte in the fish spleen, muscle, and heart is taurine, and in the brain, gill, and lens—myo-inositol. Other important osmolytes specific for particular tissues are N-acetyl-histidine, N-acetyl-aspartate, betaine, threonine-phosphoethanolamine, and serine-phosphoethanolamine. The quantitative data obtained in the present work can be used as the baseline metabolite concentrations in the fish tissues to evaluate the influence of seasonal, ecological and other factors on the fish metabolism.

Monitoring of Heavy Metal Polution the Lead (Pb) with Bio Indicator Baung Fish (Hemibagrus nemurus) at the Musi River of South Sumatra

Safitri R, Riswanda J, Armanda F. 2020. Monitoring of heavy metal polution the lead (Pb) with bio indicator baung fish (Hemibagrus nemurus) at the Musi River of South Sumatra. Jurnal Lahan Suboptimal : Journal of Suboptimal Lands 9(2): 127-138.The high activity of the community in the musi river waters could affect the quality of river water, and can even caused water pollution and aquatic biota including fish baung (Hemibagrus nemurus) by lead heavy metals (Pb). This study aimed to determine the lead (Pb) heavy metal content of baung fish (H. nemurus) catches of fishermen in the musi river waters of palembang city. This research was conducted in May-June 2019. The method used is quantitative descriptive. The sample of this research is the meat, skin, liver, kidney and gill of baung fish (H. nemurus) which are tested for lead (Pb) heavy metal content using aas (atomic absorption spectrophotometry). The results of this study indicated that the concentration of heavy metal the lead (Pb) in fish baung (H. nemurus) in the waters of the musi river on the average meat of 0.046 mg/kg, on the skin of 0.058 mg/kg, in the liver of 0.1516 mg/kg, in the kidney at 0.2513 mg/kg, and in the gills at 0.2216 mg/kg. The Pb concentration on the meat, skin and liver samples were still below the established quality standards so that they were still suitable for consumption while the kidney and fish gill samples are above the quality standards that have been set based on the regulations of the Regulations Drug and Food Control Agency (DFCA) number 5 of 2018 which is equal to 0.20 mg/kg.

The Status of VNN (Viral Nervous Necrosis)-lnfected Grouper Fish Tissue with Chlorella vulgaris Extract as Anti-Virus Candidate

To date, the most common problem in Grouper fish cultivation is VNN (Viral Nervous Necrosis) virus attack. Visual and histological observations on the fish behavior can be done to diagnose the presence of VNN. Chlorella vulgaris is believed to be one of the natural alternative ingredients that have the potential to be a VNN anti-virus. The purpose of this study is to determine the potential use of C. vulgaris extract as a candidate for VNN antivirus by conducting histological observations on the organ tissue of Grouper fish. The method used in this study was a qualitative approach with histopathological techniques examining the fish organs such as brain, kidney and eyes from each treated fish. The clinical symptom observation was carried out for 14 days. Then, the harvested organs were brought for tissue preparation and observed again with a light microscope. In this case, the histopathological changes can be assessed using a semiquantitative scoring method. The results reveal that the Grouper fish had several symptoms such as darkening body-color, abdominal bloating, abnormal swimming behavior, and decreased appetite. It is also found that there was a change in the histological picture between the infected fish without treatment and the infected fish with the administration of C. vulgaris extract. There were a number of lesions such as vacuolization, hemorrhagic, hypertrophy, and necrosis in the kidney, eye, and brain of the infected fish. Of all the treatments given, treatment (D) shows a little damage to the fish kidney, eye, and brain respectively by 26.7%, 33.3% and 33.3%. Therefore, it can be said that the administration of C. vulgaris as an alternative feed and antivirus candidate can be used as a natural immune-stimulant to enhance the immune system of Grouper fish.

Zinc Induced Histopathological Alternations in Gill, Liver, and Kidney of Freshwater Fish Gonoproktopterus kolus (Sykes)

The present study aims to investigate the histopathological changes in gill, liver, and kidney of fresh water fish Gonoproktopterus kolus (Sykes). The fingerlings of fish were exposed to Zinc (Zinc sulphate) in acute toxicity experiment (96 hrs.). The LC₀ and LC₅₀ concentrations were 2.430 ppm and 4.860 ppm respectively. After acute exposure, fish were sacrificed and tissues were obtained separately from control and LC₀ and LC₅₀ groups. These tissues were fixed in Bouin's fluid and standard protocol was followed to study histopathological alterations in gill, liver and kidney of experimental fish. In gills, fusion and degenerative changes were observed in secondary gill lamellae. In liver, hepatocytes showed hypertrophy due to degenerative changes in cellular structure. Empty hepatocytes showed shifting of nucleus. Kidney showed degenerative nuclei in the epithelial lining of the tubule. Haemopoetic tissue showed hypertrophy and disarray. Distended glomerulus was observed. Renal tubules showed disarrangement as compared to control. Thus, in present investigation, it was observed that heavy metal zinc is affecting the fishes at tissue level, which may interfere in physiological processes.

Effect of pollution with lead, cupper, cadmium on gene expression pattern of liver GST and serum lysozymes in Nile tilapia (Oreochromis. niloticus)

Objective: This study was conducted to evaluate the influence of pollution with lead, copper, cadmium on the gene expression pattern of liver Glutathione-S-transferase and serum lysozyme in Nile tilapia (Oreochromis. niloticus). Design: Descriptive study. Fish: A Total of 120 Nile tilapia fish (Oreochromis niloticus) samples were collected from Lake Manzala, and drainage water at different localities. Procedures: Cd, Cu, and Pb concentrations residues within mid-dorsal muscle tissue, within gills, liver, and kidney were determined. Erythrocyte count, hemoglobin concentration, Packed Cell volume and other blood indices, as well as, total leukocyte count were measured. Biochemically, Alanine transaminase, Aspartate transaminase activities, total protein, creatinine, uric acid, lysozymes activity were estimated. GST gene expression was determined in the liver. Results: The results showed that Pb, Cu and Cd were bio accumulated at a higher level in the liver, kidney and gills of Nile tilapia fish (Oreochromis niloticus) from all sampling sites. The levels of the ALT and AST were increased, total protein and Albumin concentrations were decreased. Creatinine and uric acid were significantly (P≤ 0.05) increased in all groups (compared to the control group. Hematological parameters and lysozyme activity were decreased. Up regulation of the hepatic GST expression levels in Nile tilapia exposed to the heavy metals in comparison to the control value. Conclusion and clinical relevance: This study shows that lead, copper and cadmium were bio accumulated at higher concentration in liver, kidney, gills and muscles of Nile tilapia due to large industrial activities near locations of the sampling sites. Additionally, GST gene expression represents sensitive biomarker of aquatic pollution.

Effects of selenium-enriched prebiotic on the growth performance, innate immune response, oxidative enzyme activity and microbiome of rainbow trout (Oncorhynchus mykiss)

Using prebiotics as functional ingredients in aquafeed is an emerging approach to prevent disease and improve fish production. This study explored the effect of supplementing aquafeed with selenium-enriched prebiotic on the growth performance, plasma lysozyme activity, and oxidative enzymes activities of various tissues of the rainbow trout, Oncorhynchus mykiss. The fish scale and intestinal microbiomes were also characterized. A genetically- modified, whole-cell inactivated Schizosaccharomyces pombe that produces a novel form of selenium called selenoneine was used as a prebiotic supplement in this study. Selenoneine is a novel selenium-containing molecule with an antioxidant activity, suggesting it has potential to improve the production of fish when used as a functional ingredient in aquafeeds. To investigate if this selenium-enriched S. pombe can strengthen the production metrics, modulate the surface and internal microbiome, and improve the health status of fish, an 8-week fish feeding trial was conducted. A commercial feed was supplemented with no addition (control), 5 g Kg−1 (0.5%), or 10 g Kg−1 (1.0%) of selenium-enriched S. pombe. Fish were harvested at the middle (week 4) and end of the trial (week 8). There were no significant differences (p > 0.05) in food conversion ratio, condition factor, or survival of fish during the trial. The microbiome also remained stable during the experiment. No effect (p > 0.05) was observed in the growth performance of the fish at week 4; however, at week 8 fish that were fed 0.5% yeast had a significantly higher weight gain (p < 0.05), hepatosomatic index, and viscerosomatic index than the fish fed control and 1.0% diets. At week 4, the concentration of plasma lysozyme in fish fed 0.5% yeast was significantly higher (p < 0.05) than the control fish and fish fed the 1.0% diet. No significant differences (p > 0.05) were observed in glutathione peroxidase activity in the liver, kidney, or plasma of fish fed experimental diets at the two different sampling times. However, the superoxide dismutase activity of plasma was significantly higher with the 0.5% diet than the control and 1.0% fed fish at week 4. At week 8, both the 0.5% and 1.0% diets led to significant increases (p < 0.05) in superoxide dismutase activity in the plasma of fish when compared to the control diet. This study demonstrates that supplementation of aquafeed with selenoneine-producing S. pombe can improve the growth, immune response, and oxidative status of fish. Thus, this ingredient holds a promising potential to enhance sustainability within the aquaculture industry.

Molecular and histopathological characterization of Photobacterium damselae in naturally and experimentally infected Nile tilapia (Oreochromis niloticus).

Mass mortality has occurred among cultured Nile tilapia, Oreochromis niloticus, on fish farms in Manzala, Dakahlia province, Egypt, in the summer season, 2019. Moribund fish were reported with deep ulcers, septicaemic lesions and sampled for bacterial isolation. In this study, most isolates were subjected to bacteriological examination, antibiotic sensitivity test, 16S rRNA gene sequencing and histopathological examination. Following isolate identification, intraperitoneal challenge of Nile tilapia with a bacterial suspension 2×106 CFU/ml was performed. Samples from liver, spleen and kidney were collected for histological and biochemical analysis. The results showed a high similarity (99%) to Photobacterium damselae strains using phylogenetic analysis of 16S rRNA. P. damselae exhibited resistance to amoxicillin and erythromycin, as well it was highly sensitive to chloramphenicol and doxycycline. Moreover, haemorrhage, oedema, hemosiderosis and melanomacrophage activation in the liver and head kidney of infected fish were detected by light and electron microscopy. Also, significant higher levels of CAT and SOD in the spleen and head kidney, as well as the serum levels of NO were observed in experimentally challenged O. niloticus, compared to the control fish. Our data identified P. damselae for the first time from infected Nile tilapia, describing its sensitivity to a variety of antibiotics, histopathological alterations and oxidative stress impact, and it could be useful indicators for understanding P. damselae pathogenesis, which might provide a preventive efficacy for P. damselae.

Characterisation of IL-15 and IL-2Rβ in grass carp: IL-15 upregulates cytokines and transcription factors of type 1 immune response and NK cell activation

Interleukin (IL) −15 belongs to the common cytokine receptor γ chain (γC) family and has diverse functions in regulating the development, proliferation and activation of NK and T cells. It activates a hetero-trimeric receptor complex consisting of IL-2Rα, IL-2Rβ and a common γ chain (γC). In this study, the full-length cDNA sequences of IL-15 and IL-2Rβ were identified in grass carp (Ctenopharyngodon idella, Ci) and their expression profiles analysed. The CiIL-15 and CiIL-2Rβ were shown to be broadly expressed in tissues, with the highest levels detected in the spleen. Moreover, the CiIL-15 and CiIL-2Rβ were modulated in primary head kidney leucocytes (HKLs) and splenocytes by immunostimulants and cytokines, and in the head kidney and spleen of fish after infection of Flavobacterium columnare and grass carp reovirus. The bioactivity of bacteria derived recombinant CiIL-15 protein was evaluated in the primary leucocytes. The CiIL-15 was shown to induce signature genes of type 1 immune response (IFN-γ and T-bet) and NK cell activation (perforin and Eomesa), whilst exhibiting inhibitory effects on the genes involved in the type 2 immune response (IL-4/13, IL-10 and Gata3). Our data suggest that IL-15 is a key regulator in promoting the type 1 immune response and NK cell activation in fish.

PCR-RFLP: a targeted method to reveal host specific malacosporean infection profiles (Cnidaria: Myxozoa: Malacosporea).

Malacosporeans are a group of endoparasitic cnidarians (Myxozoa) that use freshwater bryozoans and fish as final and intermediate hosts, respectively. The malacosporean Tetracapsuloides bryosalmonae causes proliferative kidney disease (PKD), an emerging disease in aquaculture and wild fish populations, including threatened salmonids in Europe and the USA. Mixed infections of malacosporeans are often encountered, and a monitoring tool for screening of multiple malacosporean species in either their fish or bryozoan hosts is therefore desirable. We describe an inexpensive method that combines PCR amplification of the partial 18S rRNA gene (~260 bp) and a single-step restriction fragment length polymorphism (RFLP) method for identification of 10 malacosporean lineages and species. We demonstrate and test this methodology on a set of DNA extracted from malacosporeans infecting fish kidney and tissues sampled from bryozoan colonies and compare the results with Sanger sequencing of the same parasite DNA isolates. The PCR-RFLP and Sanger sequencing methods agreed in 100% of cases. The PCR-RFLP method offers a number of opportunities, including screening large panels of host tissue samples to gain insights into infection patterns, characterizing mixed infections, and confirming highly pathogenic T. bryosalmonae infections. The method can also be further refined as new sequence data become available for malacosporeans.

Internal dynamics of inorganic and methylmercury in a marine fish: Insights from mercury stable isotopes

Mercury isotope ratios in fish tissues have been used to infer sources and biogeochemical processes of mercury in aquatic ecosystems. More experimental studies are however needed to understand the internal dynamics of mercury isotopes and to further assess the feasibility of using fish mercury isotope ratios as a monitoring tool. We exposed Olive flounder (Paralichthys olivaceus) to food pellets spiked with varying concentrations (400, 1600 ng/g) of methylmercury (MeHg) and inorganic mercury (IHg) for 10 weeks. Total mercury (THg), MeHg concentrations, and mercury isotope ratios (δ202Hg, Δ199Hg, Δ200Hg) were measured in the muscle, liver, kidney, and intestine of fish. Fish fed mercury unamended food pellets and MeHg amended food pellets showed absence of internal δ202Hg and Δ199Hg fractionation in all tissue type. For fish fed IHg food pellets, the δ202Hg and Δ199Hg values of intestine equilibrated to those of the IHg food pellets. Kidney, muscle, and liver exhibited varying degrees of isotopic mixing toward the IHg food pellets, consistent with the degree of IHg bioaccumulation. Liver showed additional positive δ202Hg shifts (∼0.63‰) from the binary mixing line between the unamended food pellets and IHg food pellets, which we attribute to redistribution or biliary excretion of liver IHg with a lower δ202Hg to other tissues. Significant δ202Hg fractionation in the liver and incomplete isotopic equilibration in the muscle indicate that these tissues may not be suitable for source monitoring at sites heavily polluted by IHg. Instead, fish intestine appears to be a more suitable proxy for identifying IHg sources. The results from our study are essential for determining the appropriate fish tissues for monitoring environmental sources of IHg and MeHg.

Relationship between Southern Bluefin Tuna, Thunnus maccoyii, melanomacrophage centres and Cardicola spp. (Trematoda: Aporocotylidae) infection

Southern Bluefin Tuna (SBT), Thunnus maccoyii, is ranched off Port Lincoln, South Australia and is Australia's second largest economic finfish aquaculture industry. The biggest threats to SBT health identified by the industry are the blood flukes Cardicola forsteri and C. orientalis (Trematoda: Aporocotylidae). Melanomacrophage centres (MMCs) are aggregations of pigmented macrophage like cells present in spleen, kidney and liver of teleost fish. The aim of this study was to quantify MMCs in SBT anterior kidney, liver and spleen to investigate changes in relation to Cardicola spp. Infection. Samples were collected at the end of ranching from pontoons where SBT were treated with PZQ and pontoons with untreated SBT. SBT MMC percentage of surface area cover was highest in SBT spleen and lowest in the liver. Significant positive correlations were identified between SBT MMC area and SBT size in all three organs (p < 0.05). MMC area and parasite infection showed significant positive correlations in the kidney and spleen for Cardicola spp. gill egg counts, and in the kidney for C. forsteri DNA from SBT hearts and gills (p < 0.05). MMCs area increased with increased intensity of Cardicola spp. Infection and MMCs have the potential to be used as an indicator to assess health effects that Cardicola spp. have on SBT.

Effect of pollution with lead, cupper, cadmium on gene expression pattern of liver GST and serum lysozymes in Nile tilapia (Oreochromis. niloticus)

Objective: This study was conducted to evaluate the influence of pollution with lead, copper, cadmium on the gene expression pattern of liver Glutathione-S-transferase and serum lysozyme in Nile tilapia (Oreochromis. niloticus). Design: Descriptive study. Fish: A Total of 120 Nile tilapia fish (Oreochromis niloticus) samples were collected from Lake Manzala, and drainage water at different localities. Procedures: lead, copper and cadmium concentrations within mid-dorsal muscle tissue, within gills, liver, and kidney were determined. Erythrocyte count, hemoglobin concentration, Packed Cell volume and other blood indices, as well as, total leukocyte count were measured. Biochemically, Alanine transaminase, Aspartate transaminase activities, total protein, creatinine, uric acid, lysozymes activity were estimated. GST gene expression was determined in the liver. Results: The results showed that Pb, Cu and Cd were bio accumulated at a higher level in the liver, kidney and gills of Nile tilapia fish (Oreochromis niloticus) from all sampling sites. The activities of ALT and AST were increased significantly (p < 0.05), but total protein and Albumin concentrations were decreased. Creatinine and uric acid were significantly increased in all groups compared to the control group (P≤ 0.05). Hematological parameters and lysozyme activity were decreased. Up regulation of the hepatic GST expression levels in Nile tilapia exposed to the heavy metals in comparison to the control value. Conclusion and clinical relevance: This study shows that lead, copper and cadmium were bio accumulated at higher concentration in liver, kidney, gills and muscles of Nile tilapia due to large industrial activities near locations of the sampling sites. Additionally, GST gene expression represents sensitive biomarker of aquatic pollution.

Effects of Toxic Metal Contamination in the Tri-State Mining District on the Ecological Community and Human Health: A Systematic Review.

Although extensive research exists on toxic environments in the Tri-State Mining District (TSMD), there has been a lack of research on how harmful effects in TSMD could affect residents living in those areas. However, quite recently, such research regarding relationships between the health conditions of residents and toxic elements in the TSMD began to grow. The increase of empirical studies means greater complexity of the findings that require a more intricate understanding. To meet the goals of this study, an extensive, systematic review of the literature using PRISMA was conducted. This method resulted in 19 articles that define the harmful effects of the TSMD on the ecology and the physical health of residents. This research found that toxic metals not only negatively impact natural processes in the TSMD environments (fish species reduction, kidney and liver problems, and toxic diet) but also continuously affect the health of residents (high blood Pb and mortality).This study makes a vital contribution building upon the existing outcomes of the correlations between toxic elements in the TSMD areas and the health of residents. Furthermore, conclusions of this study provide updated information to policymakers and health-related professionals by providing adequate and innovative remediations and health-related services in the TSMD.

Development of an immersion challenge model for Streptococcus agalactiae in Nile tilapia (Oreochromis niloticus)

Streptococcus agalactiae, the causative agent of streptococcosis in fish, induces significant mortality in the tilapia aquaculture. To elucidate the pathogenesis of S. agalactiae in tilapia, a simple and feasible challenge model was established in this study. Here, we report the development of an immersion challenge model that mimics a natural outbreak of S. agalactiae. In this model, tilapia were allowed to stress under high temperature, and hypoxia (33.5 ± 0.5°C, 2.0 ± 0.5 mg L-1 dissolved oxygen), and the bacterial exposure increased the mortality. The infection concentration assay showed the cumulative mortality to be 6.67 ± 3.34%, 32.22 ± 1.92%, and 53.3 ± 1.92% for the tilapia in the stressed group (under high temperature and hypoxia after immersed in 6.24×107, 3.12×108 and 1.56×109 CFU mL-1 for 20 min), which were higher than the cumulative mortality (0, 0, and 4.42 ± 1.95%) of the unstressed control group. The infection time assay showed the cumulative mortality to be 6.67 ± 3.34%, 26.67 ± 3.34%, and 35.56 ± 1.93% for the tilapia in the stressed group (under high temperature and hypoxia after immersed with 3.06×108 CFU mL-1 for 5, 20 and 60 min), which were higher than the cumulative mortality (0, 0, and 0%) of the unstressed control group. No mortality was observed in tilapia under stressed water conditions. The high mortality may attributed to the increased bacterial loads at 24 h post infection in the liver (6.81 × 104 vs. 2.63 × 103 CFU mg-1), spleen (1.85 × 106 vs. 8.69 × 104 CFU mg-1), and kidney (3.84 × 105 vs. 2.14 × 104 CFU mg-1) in the stressed fish compared to the unstressed fish. The serum non-specific immune parameters (adenosine deaminase, acetylcholinesterase, catalase, and superoxide dismutase) were also found to be decreased in the stressed fish. In addition, the transcripts of inflammatory-related genes (TNF-α, IL-1β, and IL10) exhibited up-regulation, whereas IgM and IgT exhibited down-regulation in the head kidney of the stressed fish, which could also increase the probability of disease. In conclusion, these findings indicate that the mortality of tilapia increased upon exposure to high temperature and hypoxia with S. agalactiae. The immersion challenge model may provide an insight into the evaluation of pathogenesis and vaccine efficacy.

Intracoelomic- and Intramuscular-Injection Challenge Model of Piscine Streptococcosis in White Sturgeon Fingerlings.

Streptococcus iniae is a zoonotic pathogen and one of the major aetiologic agents of streptococcosis. In White Sturgeon Acipenser transmontanus, S. iniae infection typically presents as a necrotizing and heterophilic myositis, causing 30-50% mortality in infected fish. To gain a better understanding of the pathogenesis of streptococcosis in White Sturgeon, and to identify the experimental route of infection that most closely mimics the natural disease, fingerlings were challenged with a single dose of 1.3×108 cells/fish of S. iniae that was administered via intracoelomic/intraperitoneal (IC) or intramuscular (IM) routes. Acute mortalities were present only in the IM-challenged fish, with first mortality occurring 4d postchallenge and the mortality rate reaching 18.3% after 9d. The challenged fish presented erratic swimming, ulcerative skin lesions, and hemorrhages in the liver and swim bladder. Streptococcus iniae was recovered from the kidney and brain tissues of moribund and dead fish. Histopathologic analysis of fish that died acutely revealed massive proliferation of bacteria in the muscle at the injection site and within vascular organs such as the heart and spleen, with variable amounts of tissue necrosis including a necrotizing myositis. Fish that died closer to 9d postchallenge demonstrated more pronounced multifocal to locally extensive granulomatous inflammation of skeletal muscle at the injection site, liver, kidney, and spleen. No mortality, clinical signs, or gross changes were observed in the control or IC-challenged fish. Postmortem evaluation of 10 survivors in each treatment was performed to determine carrier status in the brain and posterior kidney tissues. The prevalence of S. iniae in survivors was 10% and 0% in the IM- and IC-challenged groups, respectively. The results from this study suggest that IM-injection challenge methods are suitable for inducing streptococcosis in White Sturgeon, and they may be the preferred method for studying the pathogenesis of the naturally occurring disease in this species.

Protective effect of ascorbic acid against fenvalerate induced toxicity in air-breathing fish Clarias batrachus

The food demand in recent times has increased many folds. In order to augment the need for food, the agriculture practice is extensively carried out by the farmers and pesticides are widely used by them for the better yield of crops. Fishes are also cultivated by these farmers, and humans are consuming the fishes as they are very high nutritious food product. But, these pesticides through agricultural runoffs are contaminating the ponds as well the aquatic fauna like fish. The present research work deals with the evaluation of the protective effect of ascorbic acid on fenvalerate induced nephrotoxicity in Clarias batrachus. The pyrethroid pesticide- Fenvalerate EC 20% was administered directly in the water contained in the aquarium at the dose of 0.027 ppm, 0.042 ppm and 0.083 ppm respectively for 96 hrs hours after the dose calculation through LC50. Thereafter, ascorbic acid was administered orally by gastric intubation method at the dose of 200 mg/Kg body weight per day for 04 days to each pesticide treated group. The study revealed that, after the exposure of fenvalerate, there was significant damage at the biochemical levels like urea, creatinine, protein and albumin and histopathological study of kidney tissue in fish C. batrachus. But, after the administration of ascorbic acid, there was a significant restoration in the biochemical levels and in histopathology of the kidney of fish. The study concluded that Ascorbic acid possessed protective effect against fenvalerate induced toxicity in C. batrachus.

Large-scale survey of lithium concentrations in marine organisms

Trace metals such as Cu, Hg, and Zn have been widely investigated in marine ecotoxicological studies considering their bioaccumulation, transfer along trophic webs, and the risks they pose to ecosystems and human health. Comparatively, Li has received little attention, although this element is increasingly used in the high-tech, ceramics/glass, and medication industries. Here, we report Li concentrations in more than 400 samples, including whole organisms and different organs of bivalves, cephalopods, crustaceans, and fish. We investigated species from three contrasting biogeographic areas, i.e. temperate (Bay of Biscay, northeast Atlantic Ocean), tropical (New Caledonia, Pacific Ocean), and subpolar climates (Kerguelen Islands, southern Indian Ocean), among diverse trophic groups (filter-feeders to meso-predators) and habitats (benthic, demersal, and pelagic). Although Li is homogeneously distributed in the ocean (at 0.18 μg/mL), Li concentrations in soft tissues vary greatly, from 0.01 to 1.20 μg/g dry weight. Multiple correspondence analyses reveal two clusters of high and low Li concentrations. Li distributions in marine organisms appear to be mostly geographically independent, though our results highlight a temperature dependency in fish muscles. Li is consistently bio-reduced through the trophic webs, with filter-feeders showing the highest concentrations and predatory fish the lowest. Strong variations are observed among organs, consistent with the biochemical similarity between Na and Li during transport in the brain and in osmoregulatory organs. Fish gills and kidneys show relatively high Li concentrations (0.26 and 0.15 μg/g, respectively) and fish brains show a large range of Li contents (up to 0.34 μg/g), whereas fish liver and muscles are Li depleted (0.07 ± 0.03 and 0.06 ± 0.08 μg/g, respectively). Altogether, these results provide the first exhaustive baseline for future Li ecotoxicology studies in marine coastal environments.