Fish Immune System Research Articles

Sharks Provide Evidence for a Highly Complex TNFSF Repertoire in the Jawed Vertebrate Ancestor.

Cytokines of the TNF superfamily (TNFSF) control many immunological processes and are implicated in the etiology of many immune disorders and diseases. Despite their obvious biological importance, the TNFSF repertoires of many species remain poorly characterized. In this study, we perform detailed bioinformatic, phylogenetic, and syntenic analyses of five cartilaginous fish genomes to identify their TNFSF repertoires. Strikingly, we find that shark genomes harbor ∼30 TNFSF genes, more than any other vertebrate examined to date and substantially more than humans. This is due to better retention of the ancestral jawed vertebrate TNFSF repertoire than any other jawed vertebrate lineage, combined with lineage-specific gene family expansions. All human TNFSFs appear in shark genomes, except for lymphotoxin-α (LTA; TNFSF1) and TNF (TNFSF2), and CD70 (TNFSF7) and 4-1BBL (TNFSF9), which diverged by tandem duplications early in tetrapod and mammalian evolution, respectively. Although lacking one-to-one LTA and TNF orthologs, sharks have evolved lineage-specific clusters of LTA/TNF co-orthologs. Other key findings include the presence of two BAFF (TNFSF13B) genes along with orthologs of APRIL (TNFSF13) and BALM (TNFSF13C) in sharks, and that all cartilaginous fish genomes harbor an ∼400-million-year-old cluster of multiple FASLG (TNFSF6) orthologs. Finally, sharks have retained seven ancestral jawed vertebrate TNFSF genes lost in humans. Taken together, our data indicate that the jawed vertebrate ancestor possessed a much larger and diverse TNFSF repertoire than previously hypothesized and oppose the idea that the cartilaginous fish immune system is "primitive" compared with that of mammals.

Effects of autochthonous strains mixture on gut microbiota and metabolic profile in cobia (Rachycentroncanadum)

The fish immune system is a topic or subject that offers a unique understanding of defensive system evolution in vertebrate heredity. While gut microbiota plays several roles in fish: well-being, promoting health and growth, resistance to bacterial invasion, regulation of energy absorption, and lipid metabolism. However, studies on fish gut microbiota face practical challenges due to the large number of fish varieties, fluctuating environmental conditions, and differences in feeding habits. This study was carried out to evaluate the impacts of supplemented three autochthonous strains, Bacillus sp. RCS1, Pantoeaagglomerans RCS2, and Bacilluscereus RCS3 mixture diet on cobia fish (Rachycentroncanadum). Also, chromatography, mass spectrometry and high throughput sequencing were combined to explore composition and metabolite profile of gut microbiota in juvenile cobia fed with supplemented diet. In the trial group, juvenile cobia received diets supplemented with 1 × 1012 CFU mL−1 autochthonous strains for ten weeks and a control diet without supplementation. Juvenile cobia receiving diets supplementation exhibited significantly improved growth than those without additives (control). Haematological indices, such as red blood cells, white blood cells, corpuscular haemoglobin concentration, mean corpuscular volume, haemoglobin, and mean corpuscular haemoglobin, were higher in the supplemented group. Similarly, digestive enzymes (trypsin, lipase, amylase, pepsin and cellulose, activities) activities were higher in supplemented diet with an indigenous isolates mixture. Serum biochemical parameters albumin, globulin, and total protein were significantly higher, while triglyceride, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and cholesterol showed no significant difference. On the other hand, glucose was significantly (P < 0.05) higher in the group without supplementation. On gene expression in the midgut, Immunoglobulin, Colony-stimulating factor receptor 1, major histocompatibility complex 1 were up-regulated by native isolates while T cell receptor beta, and Major histocompatibility complex 2 showed no significant difference. Gut bacterial composition was altered in fish receiving supplemented diet with autochthonous strains. Metabolomics also revealed that some metabolic pathways were considerably enriched in fish fed with supplemented diet; pathway analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed that differentially expressed metabolites were involved in galactose metabolism, tryptophan metabolism, carbohydrate digestion and absorption, purine metabolism, and ABC transporters. Functional analysis of bacterial community showed that differences in enriched metabolic pathways generally comprised carbohydrate and its metabolites, nucleotide and its metabolites, amino acid and its metabolites, heterocyclic compounds, and tryptamines, cholines, pigments. The current investigation results showed that autochthonous strains mixture has significantly enhanced the growth, survival, and innate and adaptive immunities of juvenile cobia.

The roles of polysaccharides in tilapia farming: A review

Impairment of fish growth and immune system due to stress and disease are major constraints in aquaculture industry. Traditionally, antibiotic was used as prophylactic agent in the health management of aquaculture species. However, antibiotic only provide a temporary solution to the problem of disease outbreak. Over-reliance on antibiotic also has led to the increasing cases of antibiotic resistance among pathogenic bacteria from aquaculture sites and contamination of antibiotic residues into human food chain. Probiotic, prebiotic and symbiotic are therefore suggested as alternatives to prophylactic antibiotic to be used in the aquaculture industry. A potential prophylactic agent is polysaccharide that could be developed into an alternative antibiotic for aquatic animals. In this review paper, definition, sources, and mode of action of polysaccharide are presented. The roles of polysaccharides in fish farming with emphasis on growth improvement, immune system enhancement, disease resistance stimulation in tilapia farming, and the effects of polysaccharides on abiotic stressors are summarized and discussed.

Characterization of a novel Toll-like receptor 13 homologue from a marine fish Nibea albiflora, revealing its immunologic function as PRRs

Congenital immunity mediated by Toll-like receptor (TLR) family is the first line of defense for disease-resistant immunity of fish and plays a vital role as a bridge between innate immunity and acquired immunity. As a less known member of the TLR family TLR13 can participate in the immune and inflammatory reactions of the body for recognizing the conserved sequence of 23S rRNA in bacteria and induce immune response. In this study, the full-length cDNA of TLR13 from Nibea albiflora (named as NaTLR13) was cloned and was functionally characterized. It was 4210bp (GenBank accession no. MT701899) including an open reading frame (ORF) of 2886bp to encode 962 amino acids with molecular weight of 110.37 kDa and the theoretical isoelectric point of 9.08. There were several conservative structures in NaTLR13 such as 15 leucine-rich repeat sequences (LRRs), a Toll-IL-1 receptor domain (TIR), an LRR-CT terminal domain, two LRR-TYP structures and two transmembrane domains. The multiple sequence alignment and phylogenetic analysis manifested that NaTLR13 had high similarity with Larimichthys crocea and Collichthys lucidus (88.79% and 87.02%, respectively) and they fell into the same branch. The Real-time PCR showed that NaTLR13 was expressed in all selected tissues, with the highest in the spleen, followed by the liver, kidney, gill, heart and muscle. After being challenged by Vibrio alginolyticus, Vibrio parahaemolyticus or Poly (I:C), the expression of NaTLR13 increased firstly, then decreased and finally stabilized with time for its immune defense function. Subcellular localization analysis revealed that NaTLR13 was unevenly distributed in the cytoplasm with green fluorescence and MyD88 was evenly spread in the cytoplasm with red signals. When NaTLR13 and MyD88 were co-transfected, they obviously overlapped and displayed orange-yellow color, which showed that the homologous TLR13 might interact with MyD88 for NFκB signaling pathway transmission. The functional domains of NaTLR13 (named NaTLR13-TIR and NaTLR13-LRR) were expressed in E.coli BL21 (DE3) and purified by Ni-NAT Superflow Resin conforming to the expected molecular weights, and the recombinant proteins could bind to three Vibrios (V.alginolyticus, V.parahaemolyticus and Vibrio harveyi), indicating that NaTLR13 could be bounden to bacteria through its functional domain. These results suggested that NaTLR13 might play an important role in the defense of N.albiflora against bacteria or viral infection and the data would provide some information for further understanding the regulatory mechanism of the innate immune system in fish.

A simple method to evaluate the toxic effects of Prorocentrum lima extracts to fish (sea bass) kidney cells

The diarrhetic shellfish toxins (DSTs) okadaic acid (OA) and its analogues — the dinophysistoxins (DTXs) — are produced by dinoflagellates such as Prorocentrum lima and can bioaccumulate in filter-feeding organisms as they are transferred through the food web. Although there is no assessment of the harmful effects of these toxins on the fish's immune system, this study developed a primary culture protocol for kidney cells from marine fish Centropomus parallelus and evaluated the immunotoxic effects to P. lima extracts containing DSTs. The cells were obtained by mechanical dissociation, segregated with Percoll gradient, and incubated for 24 h at 28 °C in a Leibovitz culture medium supplemented with 2% fetal bovine serum and antibiotics. The exposed cells were evaluated in flow cytometry using the CD54 PE antibody. We obtained >5.0 × 106 viable cells per 1.0 g of tissue that exhibited no cell differentiation. Exposure to 1.2 or 12 ng DST mL−1 stimulated the immune system activation and increased the proportion of activated macrophages and monocytes in 48 to 52% and in 127 to 146%, respectively. The protocol proved to be an alternative tool to assess the immunotoxic effects of DST exposure on fish's anterior kidney cells.

The Effects of Dietary Thyme Oil (Thymus vulgaris) Essential Oils for Common Carp (Cyprinus carpio): Growth Performance, Digestive Enzyme Activity, Antioxidant Defense, Tissue and Mucus Immune Parameters, and Resistance against Aeromonas hydrophila.

This study evaluated the effects of dietary supplementation of thyme (Thymus vulgaris) essential oil (TVO) on growth performance, digestive enzymes, biochemical parameters, hematological indices, liver enzymes, and pathogen resistance in common carp (Cyprinus carpio). Triplicate groups of fish (15.36 ± 0.10 g) were fed daily with diets supplemented with TVO at 0, 0.5, 1, and 2 percent for 60 days then challenged with Aeromonas hydrophila. The results determined that supplementation of thyme resulted in significantly higher final body weights (FBW) and lower feed conversion ratios (FCR). Furthermore, no mortality was observed in the thyme-supplemented treatments. Regression analysis showed that fish growth parameters were polynomially related to dietary TVO levels. The optimum dietary TVO level, based upon the varied growth parameters, was 1.344 to 1.436%. Digestive enzymes activity, including amylase and protease, significantly increased in fish fed the supplemented diets. The thyme-supplemented diets also significantly increased the biochemical parameters, including total protein, albumin, and acid phosphatase (ACP), compared to the control group. We also observed significant increases in hematological indices, including red blood cells (RBC), white blood cells (WBC), hematocrit (Hct), and hemoglobin (Hb) in common carp fed diets containing thyme oil (P < 0.05). Liver enzymes activity including alanine aminotransferase (ALT), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) was also reduced (P < 0.05). Immune parameters, including total protein and total immunoglobulin (total Ig) levels, alternative complement pathway hemolytic (ACH50), lysozyme, protease, and ALP in the skin mucus, and lysozyme, total Ig, and ACH50 in the intestine were higher (P < 0.05) in TVO-supplemented fish. Catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) in the liver were also elevated (P < 0.05) in TVO administered groups. Lastly, thyme-supplementation resulted in higher survival rates after the A. hydrophila challenge compared to the control (P < 0.05). In conclusion, dietary inclusion of thyme oil (1 and 2%) effectively improved fish growth, immune systems, and resistance to A. hydrophila.

Can dietary Dictyota dichotoma powder affect performance, serum, and mucus immune parameters, and antioxidant defense in Zebrafish (Danio rerio)?

The present study was performed to study possible effects of Dictyota dichotoma which is a brown macroalgae on whole body extract (WBE) and skin mucus immune parameters, antioxidant enzyme activities as well as expression of growth, immune, and antioxidant related genes in zebrafish (Danio rerio). Zebrafish with an average weight of 0.3 ± 0.08 g were supplied and stocked in 12 aquariums. They were fed with different levels (0 %, 0.25 %, 0.5 %, and 1 %) of D. dichotoma powder for eight weeks. At the end of the trial, results revealed skin mucus immune parameters in fish treated with 1 % D. dichotoma were remarkably higher than control (P < 0.05). Similar results were obtained following evaluation of WBE total Ig and lysozyme activity (P < 0.05). Also, the activity of Superoxide dismutase (SOD) and glutathione S transferase (GST) were significantly increased (P < 0.05) when fish fed with 0.5 % and 1 % D. dichotoma supplemented diets. However, no significant alteration was noticed in the case of CAT (P > 0.05). The gene expression study revealed significant up-regulation of immune-related genes (LYZ and IL-1β) in fish fed D. dichotoma supplemented groups compared to the control group (P < 0.05). Regarding growth-related genes, D. dichotoma significantly increased GH and IGF1 expression in a dose-dependent manner (P < 0.05). Evaluation of SOD and CAT genes expression showed significant differences between the control group and treatments (P < 0.05). The highest increase was observed when zebrafish was fed 1 % macroalgae. In conclusion, the present findings suggested that adding 0.5–1 % of D. dichotoma powder to the zebrafish diet can positively affect fish antioxidant defense and immune system.

Insulin-like growth factor 1 injection changes gene expression related to amino acid transporting, complement and coagulation cascades in the stomach of tilapia revealed by RNA-seq.

Insulin-like growth factor 1 (IGF-1) is a key hormone that regulates fish growth. It acts on a variety of organs and regulates multiple signaling pathways. In order to explore the specific effects of IGF-1 on fish nutrient absorption, immune system, and other functions, the present study investigated the transcriptional changes of stomachs in tilapia by IGF injection. The tilapias were divided into two groups which were injected with saline (C group) and IGF-1 (2 μg/g body weight) (I group), respectively. After three times injections, the stomachs from the tested tilapias were collected 7 days post the first injection and the transcriptomes were sequenced by Illumina HiSeqTM 2000 platform. The results showed that a total of 155 DEGs were identified between C and I groups. By gene ontology (GO) enrichment analysis, two GO terms related to absorption function were enriched including organic acid transport, and amino acid transport which contained 6 functional DEGs. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested that Staphylococcus aureus infection, as well as complement and coagulation cascades pathways were enriched and contained 6 DEGs. Taken together, the present study indicated that IGF-1 injection altered gene expression related to amino acid transporting, complement and coagulation cascades which provides a promise immunopotentiation therapy by IGF-1 in digestive tract of tilapia.

Cryptochrome 1 is involved in anti-bacterial immunity in Japanese flounder (Paralichthys olivaceus)

Cryptochrome is a pivotal protein of the core regulatory machinery in circadian clock and participates in various biological processes including immunity. In fish, the immunological functionality of Cryptochrome is unclear. In this study, we profiled the expression pattern of Japanese flounder cryptochrome 1 (named PoCry1) and investigated its involvement in the immune response during bacterial infection. PoCry1 is approximately 75% identical in amino acid sequence to mammalian Cryptochrome 1 and possesses the conserved DNA photolyase domain and FAD binding domain. Its transcription was detected in 10 flounder tissues and was reduced upon Vibrio harveyi challenge. The transcription of PoCry1 exhibited apparent rhythmic oscillation upon the light actuation of a day-night cycle in different tissues. The knockdown of PoCry1 resulted in significant augment of inflammatory cytokine expression. During bacterial infection, PoCry1 silencing led to increase in cytokine expression and decrease in bacterial dissemination, which could be neutralized by a specific PKA inhibitor, suggesting PoCry1 is likely able to negatively modulate the immune response to bacterial infection through PKA associated pathways.Taken together, our results revealed that PoCry1 is circadian oscillated in transcription upon rhythmic light stimulation and involved in anti-infection immunity, thus enlightening that light condition as a circadian zeitgeber could be exploited to strength fish immune system and benefit disease control in aquaculture.

Transcriptomic Down-Regulation of Immune System Components in Barrier and Hematopoietic Tissues after Lipopolysaccharide Injection in Antarctic Notothenia coriiceps

The environmental conditions and isolation in the Antarctic have driven the evolution of a unique biodiversity at a macro to microorganism scale. Here, we investigated the possible adaptation of the teleost Nototheniacoriiceps immune system to the cold environment and unique microbial community of the Southern Ocean. The fish immune system was stimulated through an intraperitoneal injection of lipopolysaccharide (LPS 0111:B4 from E. coli) and the tissue transcriptomic response and plasma biochemistry were analyzed 7 days later and compared to a sham injected control. Gene transcription in the head-kidney, intestine and skin was significantly modified by LPS, although tissues showed different responsiveness, with the duodenum most modified and the skin the least modified. The most modified processes in head-kidney, duodenum and skin were related to cell metabolism (up-regulated) and the immune system (comprising 30% of differentially expressed genes). The immune processes identified were mostly down-regulated, particularly interleukins and pattern recognition receptors (PRRs), nucleotide-binding oligomerization domain-like receptors and mannose receptors, unlike the toll-like receptors response commonly described in other teleost fish. The modified transcriptional response was not mirrored by a modified systemic response, as the circulating levels of enzymes of innate immunity, lysozyme and antiproteases, were not significantly different from the untreated and sham control fish. In conclusion, while the N.coriiceps immune system shares many features with other teleosts there are also some specificities. Further studies should better characterize the PRRs and their role in Antarctic teleosts, as well as the importance of the LPS source and its consequences for immune activation in teleosts.

Influence of the essential oil of thyme and the introduction of yeast mushrooms from the genus sacharomycetes on the organism of the rainbow trout

The aim of this study was to investigate the combined effects of thyme essential oil and Saccharomycetes on blood counts and body productivity in rainbow trout. The fishery complex demonstrates positive dynamics in all key economic indicators. The use of feed additives in a complete fish diet is one such practical solution that not only improves nutritional efficiency, but also helps to reduce stress and control diseases by strengthening the immune system of fish. The study was carried out in the fish farm of the Leningrad region, on rainbow trout. 3 groups were taken, 5 in each group. The control group received only the main diet, only Saccharomycetes were introduced to the diet of group 2, and thyme essential oil was added to the main diet of group 3 in addition to Saccharomycetes. The mixture was administered at a dose of 2% of the norm was the essential oil of thyme, and 0.1% of saccharomycetes. Physico-chemical indicators of water, including temperature, were at the same level in all groups, within the physiological norm. The experiment lasted 30 days; at the end of the experiment, blood was taken to study blood parameters. Statistical analysis was carried out using STATISTICA 6 software.The present study showed that the combination of Saccharomycetes and thyme essential oil promotes the full development of fish and the efficient use of feed. Can theoretically successfully increase growth rates, survival rates, and digestive enzymes in farmed rainbow trout. Also, their inclusion in the diet can be useful for enhancing immune parameters and antioxidant responses and, therefore, can be included in the diet of this fish species as a safe feed additive.

A mini-review: Potential of Nigella sativa L. For immune fish against pathogen bacteria attack

Improving the immune system in fish as an effort to prevent fish from disease attacks caused by pathogenic organisms, because disease attacks on fish are projected to continue to grow and cause mass death of cultured fish. Giving immunostimulants as additives to feed can be a strategy to improve the fish's immune system. Immunostimulants are compounds that are able to increase the non-specific immune response or the innate immune response. Nigella sativa L known as

Th1–Th2 and M1-M2 interplay sculpt Aeromonas hydrophila pathogenesis in zebrafish (Danio rerio)

Aeromonas hydrophila is an important aquatic zoonotic pathogen that causes septicemia, necrotizing fasciitis and gastroenteritis in various aquatic and non-aquatic animals. However, the pathogenesis of A. hydrophila is not fully understood. Here, we examined the pathogenicity and histopathology of A. hydrophila in the zebrafish (Danio rerio) model system. We found that the intensity of symptoms and mortality is dose-dependent. Bacterial colonization studies demonstrated that A. hydrophila never cleared out from the fish body but stayed in a state of inactivity till it enters a fresh host. Reinfection studies showed that exposure to A. hydrophila provides immunity against future infection and hence improves fish survival. Gene expression studies revealed the crosstalk between T-helper cell and macrophage responses in fish immune system in response to A. hydrophila and infection memory. Histopathological studies showed that symptoms of tissue damage and inflammation lasted for less duration with less intensity in immunized fish when compared to non-immunized fish. Together, our results suggest that the zebrafish model is a useful system in studying the interplay between A. hydrophila pathogenesis, persistence and immunity.

Cloning of Grass Carp Chemokine XC Receptor 1 (XCR1) Gene and Evaluation of Its Expression in Various Organs after GCRV Infection

Interaction between the chemokine receptor XCR1 and its ligand is closely related to the immune function in animals; however, there are only a few reports on role of XCR1 in the immune system of fish. We aimed to analyze the expression of XCR1 in various organs or tissues of grass carp before and after Grass Carp Reovirus (GCRV) infection to better understand the function of XCR1 in resistance to GCRV infection. We cloned and sequenced the cDNA of grass carp XCR1 and analyzed the molecular structure of XCR1 based its amino acid sequence. Further, we analyzed the relative expression levels of XCR1 in different organs or tissues of male parent grass carp with GCRV resistance (P1) and their first-generation offspring (F1) before and after GCRV infection. Our results show that the total length of cDNA of the grass carp XCR1 gene is 1659 bp and encodes 365 amino acids. XCR1 contains seven conserved transmembrane helical domains. The homologous tertiary structure of XCR1 is similar to its homologs in other species. After artificial GCRV infection, there were significant differences in the expression of the grass carp XCR1 gene in different tissues, at different time points, and between P1 and F1 fish. These results will contribute to our understanding of the role of XCR1 in fish immune responses and contribute to the development of GCRV-resistant grass carp.

Structural and Functional Aspects of the Spleen in Molly Fish Poecilia sphenops (Valenciennes, 1846): Synergistic Interactions of Stem Cells, Neurons, and Immune Cells.

Simple SummaryFish are free-living organisms who are dependent on their innate immune system for survival. This system is fundamental for the defense mechanisms against invading pathogens. The head kidney, spleen, and thymus are the main immune organs in fish, albeit with slightly different roles between species. This study aims to highlight the cellular components of the spleen in the molly fish (Poecilia sphenops) by providing some background on their potential role in the immune system of fish. The splenic parenchyma of molly fish is comprised mainly of red pulp intermingled with clusters of white pulp cells. The main cells identified in this study included: erythrocytes, neurons, dendritic cells, stem cells, epithelial reticular cells, lymphocytes, ellipsoids, and granular leukocytes (eosinophils, basophils, neutrophils), and macrophages. The current study demonstrated a variety of immune cell types with specific functions in the spleen of molly fish. The strong positive immunoreactivity of the cellular constituents of the spleen for APG-5, IL-1β, NF-κB, and TGF-β suggests its critical role in immunity.In fish, the spleen is the prime secondary lymphoid organ. It has a role in the induction of adaptive immune responses, in addition to its significance in the elimination of immune complexes. This study was conducted on 18 randomly obtained adult molly fish (Poecilia sphenops) of both sexes using histological, immunohistochemical, and ultrastructural studies to highlight the cellular components of the spleen and their potential role in the immune system. The spleen of molly fish was characterized by the presence of well-distinct melanomacrophage centers, and other basic structures present in higher vertebrates including red and white pulps, blood vessels, and ellipsoids. Some mitotic cells could also be identified in the red pulp. Mast cells with characteristic metachromatic granules could be seen among the splenic cells. Rodlet cells were randomly distributed in the spleen and were also observed around the ellipsoids. The white pulp of the spleen expressed APG5. The expressions were well distinct in the melanomacrophages, leukocytes, and macrophages. Myostatin was expressed in leukocytes and epithelial reticular cells. IL-1β showed immunoreactivity in monocytes and macrophages around the ellipsoids. NF-κB and TGF-β were expressed in macrophages and epithelial reticular cells. Nrf2 expression was detected in stem cells and rodlet cells. Sox-9 had a higher expression in epithelial reticular cells and stem cells. The high frequency of immune cells in the spleen confirmed its role in the regulation of both innate and adaptive immunity, cell proliferation, and apoptosis.

Lympho-Hematopoietic Microenvironments and Fish Immune System.

Simple SummaryTeleost fish, the most abundant group of vertebrates, represent an excellent tool to establish possible correlations between the histological organization of their lymphoid organs and their immunological capacities. This approach allows us to analyze embryonic and larval lymphopoiesis, the remarkable organization of the teleost thymus, the role of the kidney as a true equivalent of the lympho-hematopoietic bone marrow of higher vertebrates, the mechanisms of antigen trapping in both ellipsoids and the so-called melano-macrophage centers (MMCs) and their relation with the generation of memory and the lack of germinal centers, and the extended development of the lymphoid tissue associated to mucosae.In the last 50 years information on the fish immune system has increased importantly, particularly that on species of marked commercial interest (i.e., salmonids, cods, catfish, sea breams), that occupy a key position in the vertebrate phylogenetical tree (i.e., Agnatha, Chondrichtyes, lungfish) or represent consolidated experimental models, such as zebrafish or medaka. However, most obtained information was based on genetic sequence analysis with little or no information on the cellular basis of the immune responses. Although jawed fish contain a thymus and lympho-hematopoietic organs equivalents to mammalian bone marrow, few studies have accounted for the presumptive relationships between the organization of these cell microenvironments and the known immune capabilities of the fish immune system. In the current review, we analyze this topic providing information on: (1) The origins of T and B lymphopoiesis in Agnatha and jawed fish; (2) the remarkable organization of the thymus of teleost fish; (3) the occurrence of numerous, apparently unrelated organs housing lympho-hematopoietic progenitors and, presumably, B lymphopoiesis; (4) the existence of fish immunological memory in the absence of germinal centers.

A review of Saprolegniosis

The most common infection in freshwater fish is a fungal infection, and they occur when the fish's immune system is weakened. Saprolegnia are fungi found in freshwater ecosystems around the world, and some species may be found in brackish to estuarine waters. These fungi need water to grow and hexose, which is why they are called water molds. Most transmission is by zoospores, which are produced by vegetative hyphae. Fish infections are usually caused by non-living sources, i.e. the fungus hexes on non-living organic matter and then attacks the fish.

Effects of dietary taurine amino acid on growth performance, mucosal and immune response, gene expression and antioxidant defence of asian seabass (Lates calcarifer).

The enhancement of fish immune system and growth performance throughout the administration of bio-friendly agents such as diet supplements (taurine) is considered a promising alternative in farmed aquatic species. The present study was aimed to examine the effect of supplementation of dietary taurine (0, 5g-TAU5 and 10g-TAU10) in crystalline form (99% purity) in L. calcarifer juveniles, taking into account growth performance, general health indices and immune related-genes mRNA transcript abundance. The results confirmed that the supplementation of taurine enhances significantly all the growth parameters and a better flesh quality. While the blood biochemical and immunological factors didn't present any significant differences, the expression of growth-related genes showed that IGF-1 was almost 3 times higher in fishes fed diet Tau 5 and Tau 10 compared to the control group. Finally, it can be concluded that at the maximum dose tested (10g) the treatment was effective for Asian seabass. In addition, Tau inclusion in an FM-based diet can increase the productivity parameters along with raising the antioxidant status.

Peynir Altı Suyunun (PAS) Gökkuşağı Alabalığı (Oncorhynchus mykiss) Bağışıklık Parametreleri Üzerine Etkisi

The aim of this study was to investigate the effect of whey on the immune system of cultured rainbow trout (Oncorhynchus mykiss). It was targeted to use whey, which is a by-product of the dairy industry, in the aquaculture industry as a promoter of fish immune system and as a source of fish feed protein. Rainbow trout individuals with an average weight of 70.28 ± 1.50 g were placed in 6 tanks with a stock density of 10 kg/m3. While fish meal (52%) was used as a protein source in the control group feeds, in the experimental group feeds whey powder (48%) was used. The fish were fed these pellet feeds that were isocaloric (21 kj / g) and isonitrogenous (41% protein) for 3 weeks. Blood samples were collected once a week and while hematocrit and hemoglobin values were determined using a fully automated hematology analyzer, standard hemocytometry methods were used in erythrocyte and leukocyte counts. In addition, free radical production and complement 3 concentrations were determined quantitatively. According to the one-way ANOVA analysis, the control group and the experimental group were statistically similar (p&amp;gt; 0,05). However, it was found that C3 complement concentration, which was measured equally at the beginning in the control and experimental groups, showed a statistically significant increase (p &amp;lt;0.05) in the experimental group compared to the control group in the second week. This is the first study in Turkey investigating the effect of using whey in fish feeds on the immune system of fish.

Integrated Management Strategies for Viral Nervous Necrosis (VNN) Disease Control in Marine Fish Farming in the Mediterranean.

Viral nervous necrosis (VNN) is the most important viral disease affecting farmed fish in the Mediterranean. VNN can affect multiple fish species in all production phases (broodstock, hatchery, nursery and ongrowing) and sizes, but it is especially severe in larvae and juvenile stages, where can it cause up to 100% mortalities. European sea bass has been and is still the most affected species, and VNN in gilthead sea bream has become an emerging problem in recent years affecting larvae and juveniles and associated to the presence of new nervous necrosis virus (NNV) reassortants. The relevance of this disease as one of the main biological hazards for Mediterranean finfish farming has been particularly addressed in two recent H2020 projects: PerformFISH and MedAID. The presence of the virus in the environment and in the farming systems poses a serious menace for the development of the Mediterranean finfish aquaculture. Several risks associated to the VNN development in farms have been identified in the different phases of the farming system. The main risks concerning VNN affecting gilthead seabream and European seabass have been identified as restocking from wild fish in broodstock facilities, the origin of eggs and juveniles, quality water supply and live food in hatcheries and nurseries, and infected juveniles and location of farms in endemic areas for on-growing sites. Due to the potential severe impact, a holistic integrated management approach is the best strategy to control VNN in marine fish farms. This approach should include continuous surveillance and early and accurate diagnosis, essential for an early intervention when an outbreak occurs, the implementation of biosecurity and disinfection procedures in the production sites and systematic vaccination with effective vaccines. Outbreak management practices, clinical aspects, diagnostic techniques, and disinfections methods are reviewed in detail in this paper. Additionally, new strategies are becoming more relevant, such as the use of genetic resistant lines and boosting the fish immune system though nutrition.