Blood Of Rainbow Trout Research Articles

Effect of β-glucans on rainbow trout (Oncorhynchus mykiss) IgM+ B cells

β-glucans are carbohydrates present in the cell wall of many fungi, which are often used as immunostimulants in feeds for farmed species. Their capacity to activate innate immune responses directly acting on innate cell populations has been widely documented in fish. However, whether they can affect the functionality of adaptive immune cells has been scarcely explored. In this context, in the current work, we have determined the effects of β-glucans on rainbow trout blood IgM+ B cells in the presence or absence of 2,4,6-trinitrophenyl hapten conjugated to lipopolysaccharide (TNP-LPS), a model antigen. For this, rainbow trout peripheral blood leukocytes were incubated with different doses of β-glucans or media alone in the presence or absence of TNP-LPS for 48 h. The size, levels of expression of surface MHC II, antigen processing and phagocytic capacities and proliferation of IgM+ B cells were then studied by flow cytometry. The number of IgM-secreting cells in the cultures was also estimated by ELISpot. β-glucans significantly decreased the levels of surface MHC II expression and the antigen processing capacities of these cells, especially in the presence of TNP-LPS, while they increased their phagocytic activity. On their own, β-glucans slightly activated the proliferation of IgM+ B cells but reduced that induced by TNP-LPS. In contrast, β-glucans significantly increased the number of cells secreting IgM in the cultures. This effect of β-glucans on the IgM-secreting capacity of B cells was also confirmed through a feeding experiment, in which the IgM-secreting capacity of blood leukocytes obtained from fish fed a β-glucan-supplemented diet for one month was compared to that of leukocytes obtained from fish fed a control diet. Altogether, these findings contribute to increase our knowledge regarding the effects of β-glucans on fish adaptive responses.

Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues.

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА КОРМОВ ПО БИОХИМИЧЕСКИМ ПОКАЗАТЕЛЯМ СЫВОРОТКИ КРОВИ ONCORHYNCHUS MYKISS (WALBAUM, 1792)

The main reasons for the decrease in feeding efficiency are dietary inadequacy and poor quality of the feed, which leads to its suboptimal consumption and accumulation of residue, which, in turn, results in deterioration of the hydrochemical regime. This study presents the comparative analysis of two fish feeds in terms of their safe use for Oncorhynchus mykiss (Walbaum, 1792) feeding and their impact on water quality. The investigation was conducted on the rainbow trout individuals in the recirculating aquaculture system at the Aquaculture Center of the K.G. Razumovsky Moscow State University of Technologies and Management in 2021-2020 and involved the comparison of the feeds CRYSTAL (protein content 42.65 %) produced by Alltech Coppens and Basic PL 45/20 A50 (protein content 45.81 %) produced by BNBC (Belarusian National Biotechnology Corporation). Six test groups were included in the experiment: three groups were fed with Alltech Coppens CRYSTAL and the other three groups were fed with BNBC Basic PL compound feed. The biochemical characteristics of the rainbow trout blood serum have been identified using the blood taken from a caudal vein, and the hydrochemical characteristics of the water have been identified using standard procedures. A distinct relationship between the protein content in Oncorhynchus mykiss blood serum and protein content in the feeds has been found. The hydrochemical characteristics of the water in the recirculating aquaculture system over the course of the experiment remained within the normal range, with exception of iron that had been present before the experiment and did not have an adverse effect on the fish’s health.

Investigation of Some Biochemical Parameters and Mineral Values in the Blood of Rainbow trout Growing in Dam and Sea water

In this study, it was aimed to investigate the effect of the difference in the breeding environment (pH, temperature, salinity, oxygen content and saturation) of rainbow trout grown in dam and sea water on the level of some minerals (calcium, magnesium, zinc, iron) and biochemical parameters in the serum. The study material consisted of 20 rainbow trout (Oncorhynchus mykiss) weighing about 800-1000 gr in the dam water of Samsun (Derbent Dam) and the Black Sea water (Yakakent). Blood samples were taken from both groups on the same day in December and the pH, temperature, oxygen content and saturation level of the water were determined by YSK oxygen meter, and salinity was determined by refractometry. Total protein (TP), albumin (Alb), cholesterol (TK), glucose (Glu), urea, creatinine (Cre), uric acid (UA), Aspartate transaminase (AST), Alanine Aminotransferase (ALT), triglyceride (TG) Calcium, magnesium, iron and zinc and ALT, AST enzyme activities were determined by spectrophotometric method in an autoanalyzer. It was observed that the salinity, oxygen and saturation levels of the sea water were higher than those of the dam water, and the pH and temperature were close to each other. It was determined that TP, Alb, Alb/Glo, TK, TG, UA and Ca levels in rainbow trout raised in the dam were significantly higher than those raised in the sea (P<0.05). Glu, Cre, Mg and Fe levels were found to be higher in the blood serum of rainbow trout (P<0.05). Zn, urea, AST and ALT levels of rainbow trout raised in sea and dam were similar. In our study where the same fish species were provided with the same feeding conditions, it was observed that the differences in salinity and dissolved oxygen levels of fish farming waters caused changes in some mineral and blood parameter levels in fish. It was concluded that determining the supplementation of the missing minerals in fish according to the salinity and dissolved oxygen level in the environment may be important for the development of the fish.

Oxidative Stress Biomarkers in the Blood of Rainbow Trout (Oncorhynchus mykiss Walbaum) and Equine Plasma after Incubation with Hemp Oil "Annabis Bio"

Industrial hemp is a multi-use crop that has been widely cultivated to produce fibers and nutrients, such as protein, dietary fiber, minerals, and unsaturated fatty acids, which make them a good fortifying component in food production. The antioxidant capability of hemp oils has been reported. In the current study, for evaluating the antioxidant activity of commercial hemp oil "Annabis BIO" derived from certified industrial hemp seeds without the psychoactive substance THC (Olomouc, Czech Republic), biomarkers of oxidative stress [2-thiobarbituric acid reactive substances (TBARS), oxidatively modified proteins (OMP), total antioxidant capacity (TAC)] were used in models of the blood collected from adult healthy rainbow trout (Oncorhynchus mykiss Walbaum), the blood of rainbow trout with clinical symptoms of ulcerative dermal necrosis (UDN), and equine plasma. A volume of 0.1 mL of the hemp oil was added to 1.9 mL of fish blood or equine plasma. After incubation of the mixture for 60 min with continuous stirring, biomarkers of oxidative stress were studied in samples. After in vitro incubation of hemp oil with the blood of clinically healthy rainbow trout, we noted a statistically significant decrease in biomarkers of lipid peroxidation by 55.6% (p <0.05). The highest increase in TBARS level was observed after in vitro incubation of hemp oil with the blood of UDN-affected rainbow trout. In vitro incubation of hemp oil with equine plasma resulted in a statistically significant increase in the level of ketonic derivatives (by 29%, p <0.05) and aldehydic derivatives of OMP (by 33.1%, p <0.05). Incubation of hemp oil with the blood of UDN-affected trout resulted in a decrease of the ketonic derivative of OMP (by 43.3%, p <0.05). Incubation of hemp oil with equine plasma, we observed a statistically significant decrease in TAC level by 56.6% (p <0.05). Similarly, after incubation hemp oil with blood samples of UDN-affected trout, a statistically significant decrease in total antioxidant capacity (by 59.3%, p <0.05) was observed. The results suggest that the investigated hemp oil have shown varied antioxidant capacities. Accordingly, this study proposes that the therapeutic benefit of this hemp oil can be, at least in part, attributed to using different biological materials (blood, plasma) used in vitro in the current study.

A Multidisciplinary Approach Evaluating Soybean Meal-Induced Enteritis in Rainbow Trout Oncorhynchus mykiss

This study evaluated a diverse range of markers of feeding stress to obtain a more precise assessment of the welfare of rainbow trout in relation to inadequate husbandry conditions. A feeding stress model based on dietary soybean meal was employed to identify suitable minimally invasive “classical” stress markers, together with molecular signatures. In a 56-day feeding experiment, rainbow trout were fed diets containing different levels of soybean meal. The impact of these different soybean meal diets on rainbow trout was assessed by water quality analyses, clinical health observations, classic growth and performance parameters, gut histopathology, blood-parameter measurements and multigene-expression profiling in RNA from whole blood. Soybean meal-induced enteritis was manifested phenotypically by an inflammatory reaction in the posterior section of the intestine and by diarrhoea in some trout. These inflammatory changes were associated with decreased supranuclear vacuolation. The haematocrit values and the levels of plasma cortisol and circulating lymphocytes in the blood were increased in trout that had consumed high amounts of SBM. Notably, the increased haematocrit depended significantly on the bodyweight of the individual trout. The transcript levels of certain genes (e.g., MAP3K1, LYG, NOD1, STAT1 and HSP90AB) emerged as potentially useful indicators in the blood of rainbow trout providing valuable information about inadequate nutrition. The expression-profiling findings provide a basis for improved, minimally invasive monitoring of feeding regimens in trout farming and may stimulate the development of practical detection devices for innovative aquaculture operations.

Hematological and biochemical indicators of rainbown trout blood depending on lysin and methionine levels in feed

The effect of use of complete feed with different lysine and methionine levels on the hematological and biochemical indicators of rainbow trout blood is studied in the article. The aim of the experiment was to establish the effect of different levels of amino acid nutrition of commercial rainbow trout on hematological and biochemical indicators of its blood. For this purpose, five experimental groups were formed by the analog method. The study lasted 210 days and was divided into two periods: equalizing (10 days) and basic (200 days). In the equalizing period, the trial fish consumed feed of the control group. In the basic period of the experiment, the level of lysine and methionine in the production feed ranged from 2.5 to 2.9% and from 0.8 to 1.0%, respectively. It was found that the different content of lysine and methionine in the diets of two-year-old rainbow trout did not cause significant changes in biochemical indicators of blood. The increase in the content of limiting amino acids in the combined feed of young rainbow trout caused slight deviations in hemoglobin content compared to control. The analysis of the obtained results revealed the highest content of erythrocytes (1.28 T/l) in the blood of specimen of experimental group 5, the level of amino acids in combined feeds was the lowest. Its highest content was found in the blood plasma of trout of experimental group 4, which received combined feed with a content of 2.8 % lysine and 0.95 % methionine. The concentration of total protein in the blood serum was almost the same in all experimental groups of commercial rainbow trout. It was found that different levels of amino acid nutrition of rainbow trout did not affect the dynamics of changes in the blood cell morphology differentials.

Diversity of Rainbow Trout Blood B Cells Revealed by Single Cell RNA Sequencing

Simple SummaryAlthough evolutionarily jawed fish constitute the first group of animals in which a complete adaptive immune system based on immunoglobulins (Igs) is present, many structural immune differences between fish and mammals predict important functional and phenotypical differences between B cells in these two animal groups. However, to date, very few tools are available to study B cell heterogeneity and functionality in fish. Hence, thus far, antibodies targeting the different Igs have been almost exclusively applied as tools to investigate B cell functionality in fish. In the current study, we used the newly developed 10× Genomics single cell RNA sequencing technology and used it to analyze the transcriptional pattern of single B cells from peripheral blood. The results obtained provide us with a transcriptional profile at single cell level of what seem to correspond to different B cell subsets or B cells in different stages of maturation or differentiation. The information provided will not only help us understand the biology of teleost B cells, but also provides us with a repertoire of potential markers that could be used in the future to differentiate trout B cell subsets. Single-cell sequencing technologies capable of providing us with immune information from dozens to thousands of individual cells simultaneously have revolutionized the field of immunology these past years. However, to date, most of these novel technologies have not been broadly applied to non-model organisms such as teleost fish. In this study, we used the 10× Genomics single cell RNA sequencing technology and used it to analyze for the first time in teleost fish the transcriptional pattern of single B cells from peripheral blood. The analysis of the data obtained in rainbow trout revealed ten distinct cell clusters that seem to be associated with different subsets and/or maturation/differentiation stages of circulating B cells. The potential characteristics and functions of these different B cell subpopulations are discussed on the basis of their transcriptomic profile. The results obtained provide us with valuable information to understand the biology of teleost B cells and offer us a repertoire of potential markers that could be used in the future to differentiate trout B cell subsets.

Pretreatment with selenium prevented the accumulation of hexavalent chromium in rainbow trout (Oncorhynchus mykiss) and reduced the potential health risk of fish consumption

Hexavalent chromium (Cr6+) is a toxic element in environment. Selenium (Se) is an essential micronutrient trace element for living organisms and can ameliorate the adverse effects induced by Cr6+. However, the correlations between Se and Cr in fish have been rarely reported. The present study focused on the antagonistic effects of Se on Cr-induced accumulation in tissues (blood, gills, intestines, liver, kidney and muscle) of rainbow trout. Initially, a 42-day feeding trail was conducted as the fish were fed with basal diet supplemented with or without 4 mg/kg Se (as Se-yeast). A remarkable increase of Se in tissues was observed. Se was predominately accumulated in liver and the Se significantly decreased the initial Cr level in liver. Furthermore, after the pretreatment of Se, the fish were exposed to 1 mg/L Cr solution and it could be found that all the tissues showed a significant accumulation of Cr. An exciting result was obtained that the pretreatment of Se could prevent the Cr accumulation in fish muscle and reduced the health risk of fish consuming. A pearson correlation analysis was conducted to examine the relationship between Se and Cr and a significant negative correlation was found in muscle. Overall, it could be concluded that the pretreatment of Se in rainbow trout could effectively prevent the Cr accumulation in muscle, which is beneficial for reducing health risk of fish consumption.

Hematological and biochemical blood indices of rainbow trout depending on the level of protein in feeds

Protein nutrition of fish is one of the main factors of ensuring their active growth. Finding the optimal concentration of protein is an actual direction of research. The purpose of the experiment was to establish the effect of different protein nutrition levels in commercial rainbow trout feeding on hematological and biochemical parameters of their blood. For this purpose, five experimental groups were formed by the method of analogs. The experiment lasted 210 days and was divided into two periods: equalization (10 days) and main (200 days). During the equalization period, the feeding ration was the same for fish in the control and experimental groups. In the main period, the level of protein in experimental feeds for different experimental trout groups ranged from 44 to 52% per 1 kg. It was found that different levels of rainbow trout’s protein nutrition did not cause significant changes in blood morphological composition. It is proved that rearing trout using compound feeds with a crude protein content of 50% and 52% promotes the increase of red blood cells, hemoglobin, white blood cells and phagocytic activity in blood. The use of 44% and 46% low crude protein diets in fish feeding reduces the morphological components in blood. As a result of studies on the phagocytic activity of neutrophils in fish blood, a slight increase was revealed under the influence of the studied factor. The analysis of the obtained results showed that with increasing levels of crude protein in the diets of rainbow trout, the concentration of total protein and its fractions in blood serum increased. Accordingly, the amount of total protein in blood of fish in the control group was 60.0 g/L, in the experimental groups – it was within the range of 59.6- 65.3 g/L. The increase in the level of rainbow trout’s protein nutrition in the experimental groups 4 and 5 caused an increase in the number of albumins, β-globulins and γ-globulins compared to control. As a result of experimental studies, an increase in the mineral status of rainbow trout blood during use of feeds with the crude protein content of 50-52 % was established. No differences were found during the assessment of trout white blood cell counts. The use of the obtained results during the production of compound feed will allow having a positive effect on the hematological parameters of commercial rainbow trout

Plasma proteome profiling of freshwater and seawater life stages of rainbow trout (Oncorhynchus mykiss).

The sea-run phenotype of rainbow trout (Oncorhynchus mykiss), like other anadromous salmonids, present a juvenile stage fully adapted to life in freshwater known as parr. Development in freshwater is followed by the smolt stage, where preadaptations needed for seawater life are developed making fish ready to migrate to the ocean, after which event they become post-smolts. While these three life stages have been studied using a variety of approaches, proteomics has never been used for such purpose. The present study characterised the blood plasma proteome of parr, smolt and post-smolt rainbow trout using a gel electrophoresis liquid chromatography tandem mass spectrometry approach alone or in combination with low-abundant protein enrichment technology (combinatorial peptide ligand library). In total, 1,822 proteins were quantified, 17.95% of them being detected only in plasma post enrichment. Across all life stages, the most abundant proteins were ankyrin-2, DNA primase large subunit, actin, serum albumin, apolipoproteins, hemoglobin subunits, hemopexin-like proteins and complement C3. When comparing the different life stages, 17 proteins involved in mechanisms to cope with hyperosmotic stress and retinal changes, as well as the downregulation of nonessential processes in smolts, were significantly different between parr and smolt samples. On the other hand, 11 proteins related to increased growth in post-smolts, and also related to coping with hyperosmotic stress and to retinal changes, were significantly different between smolt and post-smolt samples. Overall, this study presents a series of proteins with the potential to complement current seawater-readiness assessment tests in rainbow trout, which can be measured non-lethally in an easily accessible biofluid. Furthermore, this study represents a first in-depth characterisation of the rainbow trout blood plasma proteome, having considered three life stages of the fish and used both fractionation alone or in combination with enrichment methods to increase protein detection.

Synergistic effect of sodium selenite and Pediococcus acidilactici on growth, intestinal bacterial counts, selenium bioavailability, hepatic enzymes and non‐specific immune response in rainbow trout ( Oncorhynchus mykiss )

Lactic acid bacteria (LAB) have a crucial role in inorganic selenium metabolism as well as their known desirable effects on fish. In this study, the synergistic effects of dietary sodium selenite and Pediococcus acidilactici on growth performance, intestinal bacterial counts, selenium bioavailability, hepatic antioxidant enzyme thioredoxin reductase activity and hepatic glycolytic enzyme activity that is hexokinase, phosphofructokinase and pyruvate kinase, and non‐specific immune response such as serum lysozyme and complements C₃, C₄ and ACH₅₀ activity in rainbow trout (Oncorhynchus mykiss) were investigated. Thus, a 3 × 3 factorial design experiment was conducted with nine purified diets including three levels of sodium selenite (0, 1 and 2 mg/kg) and three levels of P. acidilactici (0, 7 and 9 log CFU/g). After 8 weeks of feeding, weight gain and specific growth rate were increased by increasing dietary sodium selenite and P. acidilactici levels compared to control (p .05). Total cultivable bacterial populations after 4 and 8 weeks of the feeding trial were not significantly different among the dietary treatments, while LAB levels were higher in P. acidilactici‐fed groups than in control and selenium‐fed groups (p < .05). Selenocysteine, methylselenocysteine and selenomethionine levels in the intestine of rainbow trout were increased by increasing the sodium selenite and P. acidilactici levels (p < .05), and selenocysteine was found the most selenium species in the trout intestine. The quantity of total selenium in the whole body, intestine, blood, liver and muscle of rainbow trout were increased by increasing the amounts of sodium selenite and P. acidilactici compared to control (p < .05). Hepatic thioredoxin reductase and hexokinase activity were increased by increasing dietary selenium and P. acidilactici levels in comparison to control (p < .05), whereas phosphofructokinase and pyruvate kinase activity in the liver of rainbow trout were not significantly different between the dietary treatments. Serum lysozyme, complements C₃, C₄ and ACH₅₀ activity were enhanced by increasing dietary selenium and P. acidilactici levels compared to control (p < .05). The most synergistic effects of dietary supplements on growth and metabolism of rainbow trout were obtained at 2 mg/kg sodium selenite and 7 log CFU/g P. acidilactici. The findings revealed the synergistic effect of dietary selenium and P. acidilactici on growth and metabolism in rainbow trout (O. mykiss).

Integrated Transcriptomic and Proteomic Analysis of Red Blood Cells from Rainbow Trout Challenged with VHSV Point Towards Novel Immunomodulant Targets.

Teleost red blood cells (RBCs) are nucleated and therefore can propagate cellular responses to exogenous stimuli. RBCs can mount an immune response against a variety of fish viruses, including the viral septicemia hemorrhagic virus (VHSV), which is one of the most prevalent fish viruses resulting in aquaculture losses. In this work, RBCs from blood and head kidney samples of rainbow trout challenged with VHSV were analyzed via transcriptomic and proteomic analyses. We detected an overrepresentation of differentially expressed genes (DEGs) related to the type I interferon response and signaling in RBCs from the head kidney and related to complement activation in RBCs from blood. Antigen processing and presentation of peptide antigen was overrepresented in RBCs from both tissues. DEGs shared by both tissues showed an opposite expression profile. In summary, this work has demonstrated that teleost RBCs can modulate the immune response during an in vivo viral infection, thus implicating RBCs as cell targets for the development of novel immunomodulants.

Immune-Specific Expression and Estrogenic Regulation of the Four Estrogen Receptor Isoforms in Female Rainbow Trout (Oncorhynchus mykiss).

Genomic actions of estrogens in vertebrates are exerted via two intracellular estrogen receptor (ER) subtypes, ERα and ERβ, which show cell- and tissue-specific expression profiles. Mammalian immune cells express ERs and are responsive to estrogens. More recently, evidence became available that ERs are also present in the immune organs and cells of teleost fish, suggesting that the immunomodulatory function of estrogens has been conserved throughout vertebrate evolution. For a better understanding of the sensitivity and the responsiveness of the fish immune system to estrogens, more insight is needed on the abundance of ERs in the fish immune system, the cellular ratios of the ER subtypes, and their autoregulation by estrogens. Consequently, the aims of the present study were (i) to determine the absolute mRNA copy numbers of the four ER isoforms in the immune organs and cells of rainbow trout, Oncorhynchus mykiss, and to compare them to the hepatic ER numbers; (ii) to analyse the ER mRNA isoform ratios in the immune system; and, (iii) finally, to examine the alterations of immune ER mRNA expression levels in sexually immature trout exposed to 17β-estradiol (E2), as well as the alterations of immune ER mRNA expression levels in sexually mature trout during the reproductive cycle. All four ER isoforms were present in immune organs—head kidney, spleen-and immune cells from head kidney and blood of rainbow trout, but their mRNA levels were substantially lower than in the liver. The ER isoform ratios were tissue- and cell-specific, both within the immune system, but also between the immune system and the liver. Short-term administration of E2 to juvenile female trout altered the ER mRNA levels in the liver, but the ERs of the immune organs and cells were not responsive. Changes of ER gene transcript numbers in immune organs and cells occurred during the reproductive cycle of mature female trout, but the changes in the immune ER profiles differed from those in the liver and gonads. The correlation between ER gene transcript numbers and serum E2 concentrations was only moderate to low. In conclusion, the low mRNA numbers of nuclear ER in the trout immune system, together with their limited estrogen-responsiveness, suggest that the known estrogen actions on trout immunity may be not primarily mediated through genomic actions, but may involve other mechanisms, such as non-genomic pathways or indirect effects.

Динаміка змін фізіологічного стану і гематологічних показників райдужної форелі під час запуску біофільтра в установках замкненого водовикористання

Наведено результати змін фізіологічного стану і гематологічних показників райдужної форелі у воді установок замкненого водопостачання. Показано, що під час запуску біофільтра УЗВ найбільша загибель малька райдужної форелі виникає з 16 по 20 добу досліду і становить 14,9% від усієї риби. При цьому вся жива риба плавала у верхніх шарах води, у ≈ 50% риби спостерігалося нервове тремтіння тіла та плавників, вона масово підпливала до місця подавання води, у ≈ 90% риби ввідмічали потемніння тіла і плавників, які були ущільнені, у ≈ 90% риби колір зябер змінювався з червоного на коричневий.З моменту запуску біофільтра і до 25 доби у крові риби знижувалася кількість еритроцитів, яка виявилася вірогідною у період з 16 по 20 добу (Р ≤ 0,05) і з 21 по 25 добу, а також вірогідно знижувався рівень гемоглобіну на 16–20 і 21–25 доби (Р ≤ 0,05).Із запуском біофільтра в присутності малька райдужної форелі у крові риб, порівняно із початком запуску біофільтра, зростає вміст метгемоглобіну: на 6–10 добу досліду на 8,8%, 11–15 добу – на 15,0%, 16–20 добу – на 26,4%, 21–25 добу – на 16,8%, 26–30 добу – на 12,8% і 31–35 добу – на 2,1%.

Proteomic identification of rainbow trout blood plasma proteins and their relationship to seminal plasma proteins.

The characterisation of fish blood proteomes is important for comparative studies of seminal and blood proteins as well as for the analysis of fish immune mechanisms and pathways. In this study, LC-MS/MS and 2D-DIGE were applied to compare rainbow trout seminal (SP) and blood plasma (BP) proteomes. The 54 differentially abundant proteins identified in SP are involved in a variety of signalling pathways, including protein ubiquitination, liver X receptor/retinoid X receptor (LXR/RXR) and farnesoid X receptor activation, cell cycle and acute phase signalling. These findings may indicate the prevalence of acute phase signalling pathways in trout SP, and its essential role in protecting spermatozoa and reproductive tissues. Our study provides the first in-depth analysis of the trout BP proteome, with a total of 119 proteins identified. The major proteins of rainbow trout BP were recognised as acute phase proteins. Analysis of BP proteins indicated that acute phase response signalling, the complement system, liver X receptor/retinoid X receptor and farnesoid X receptor activation and the coagulation system are the top canonical pathways. This study enhances knowledge of the blood origin of trout SP proteins and understanding of fish reproductive biology. Our results provide new insight into blood proteins specifically important for fish physiology and innate immunity. The mass spectrometry data are available via ProteomeXchange with the identifier PXD005988 and https://doi.org/10.6019/PXD005988.

Cortisol and testosterone accumulation in a low pH recirculating aquaculture system for rainbow trout (Oncorhynchus mykiss )

Steroids accumulate in recirculating aquaculture system (RAS), although explanatory factors for such accumulation are still poorly explored. This study investigated the effect of water exchange rate and pH in six replicated RAS on the concentration of the stress hormone cortisol in rainbow trout blood plasma and in the holding water and of the sex steroids testosterone, 11-ketotestosterone (11-KT) and 17,20β-dihydroxypregn-4-en-3-one (17,20β-P) over a 70-day experimental period. Three combinations of water exchange rate and pH were used each treatment, with two replications: (i) high water exchange rate (±1700 L kg−1 feed) and neutral pH (±7.3), (ii) low water exchange rate (±500 L kg−1 feed) and neutral pH (±7.3) and (iii) low water exchange rate (±500 L kg−1 feed) and low pH (±5.8). Plasma cortisol concentrations at day 70 were higher (24.4 ± 9.5 ng mL−1) for fish kept at low pH when compared to fish kept at neutral pH (12.0 ± 0.1 and 8.7 ± 0.2 ng mL−1). Water cortisol and testosterone concentrations at day 35 were higher at low pH than at neutral pH, whereas water 11-KT and 17,20β-P did not differ among treatments. At day 70, there were no significant differences between low and high pH. These results demonstrate that low pH contributes to increased plasma cortisol concentrations and to its accumulation in water, possibly indicating a stress response to low pH. The higher concentration of testosterone but not of the other sex hormones point to unspecified reproductive effects that need further investigation.

Individual monitoring of immune responses in rainbow trout after cohabitation and intraperitoneal injection challenge with Yersinia ruckeri.

Yersinia ruckeri, the causative agent of enteric red mouth disease (ERM), is a widely studied pathogen in disease models using rainbow trout. This infection model, mostly based on intraperitoneally injection or bath immersion challenges, has an impact on both components (innate and adaptive) of the fish immune system. Although there has been much attention in studying its host-pathogen interactions, there is still a lack of knowledge regarding the impact of a cohabitation challenge. To tackle this we used a newly established non-lethal sampling method (by withdrawing a small amount of blood) in rainbow trout which allowed the individual immune monitoring before (non-infected) and after infection with Yersinia ruckeri either by intraperitoneal (i.p.) injection or by cohabitation (cohab). A range of key immune genes were monitored during the infection by real-time PCR, and results were compared between the two infection routes. Results indicated that inflammatory (IL-1β1 and IL-8) cytokines and certain antimicrobial peptides (cathelicidins) revealed a different pattern of expression between the two infected groups (i.p. vs cohab), in comparison to adaptive immune cytokines (IL-22, IFN-γ and IL-4/13A) and β-defensins. This suggests a different involvement of distinct immune markers according to the infection model, and the importance of using a cohabitation challenge as a more natural disease model that likely simulates what would occur in the environment.

Chronic effect of waterborne colloidal silver nanoparticles on plasma biochemistry and hematology of rainbow trout (Oncorhynchus mykiss)

Objective: To investigate the possible effects of silver nanoparticles (AgNPs) on some blood and plasma indices of rainbow trout (Oncorhynchus mykiss). Methods: Hence, fish were exposed for 21 days to sub-lethal concentrations of colloidal AgNPs and blood parameters including erythrocyte size and hematocrit, plasma parameters including cholinesterase, cortisol, sodium, chloride, and potassium, and also silver concentration in plasma were measured following the 11th and 21st days of exposure. Results: According to the results of present study, higher concentrations of AgNPs had more significant effects on plasma biochemistry and hematology of trout. The greatest impacts were decline of chloride ions and increase of cortisol and cholinesterase. Also fish exposed to AgNPs significantly increased silver concentration in the plasma. Conclusions: Further studies are needed to identify appropriate blood biomarkers following fish exposed to nanomaterials, especially AgNPs. Article history:

Validation of the i-STAT system for the analysis of blood parameters in fish.

Portable clinical analysers, such as the i-STAT system, are increasingly being used for blood analysis in animal ecology and physiology because of their portability and easy operation. Although originally conceived for clinical application and to replace robust but lengthy techniques, researchers have extended the use of the i-STAT system outside of humans and even to poikilothermic fish, with only limited validation. The present study analysed a range of blood parameters [pH, haematocrit (Hct), haemoglobin (Hb), HCO3 (-), partial pressure of CO2 (PCO2), partial pressure of O2 (PO2), Hb saturation (sO2) and Na(+) concentration] in a model teleost fish (rainbow trout, Oncorhynchus mykiss) using the i-STAT system (CG8+ cartridges) and established laboratory techniques. This methodological comparison was performed at two temperatures (10 and 20°C), two haematocrits (low and high) and three PCO2 levels (0.5, 1.0 and 1.5%). Our results indicate that pH was measured accurately with the i-STAT system over a physiological pH range and using the i-STAT temperature correction. Haematocrit was consistently underestimated by the i-STAT, while the measurements of Na(+), PCO2, HCO3 (-) and PO2 were variably inaccurate over the range of values typically found in fish. The algorithm that the i-STAT uses to calculate sO2 did not yield meaningful results on rainbow trout blood. Application of conversion factors to correct i-STAT measurements is not recommended, due to significant effects of temperature, Hct and PCO2 on the measurement errors and complex interactions may exist. In conclusion, the i-STAT system can easily generate fast results from rainbow trout whole blood, but many are inaccurate values.