Fish hematology and associated disorders

Maximum storage time of refrigerated blood and frozen plasma samples from tambaqui, Colossoma macropomum

Blood analysis is an important tool for monitoring the health status of fish, but the time between collection and analysis can affect the outcome of the analysis. This study sought to determine the maximum time refrigerated blood and frozen plasma samples of the tambaqui, Colossoma macropomum, can be stored without affecting analysis. Samples from 12 fish were obtained, stored under refrigeration at 4 °C and evaluated after 0, 24, 48, 72, and 96 h, while samples from 14 fish were centrifuged, and the resulting plasma was frozen at -20 °C and then evaluated after 0, 8, 12, 16 and 20 weeks. The parameters analyzed were hematocrit (Ht), hemoglobin content (Hb), total erythrocytes (RBC), total (WBC) and differential leukocytes, total thrombocytes (TC), glucose content (Glc), total protein (TP), triglyceride content (TG), total cholesterol (CoT), and the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). For refrigerated whole blood samples, mean corpuscular hemoglobin content (MCHC) showed a transient decline in 24 h, and there were decreases in WBC, TC, Glc and TG that persisted until the 72 h sample point (for Glc and TG) or persisted until the 96 h sample point (for WBC and TC). A decrease in RBC was noted from 48 h on, while ALT was significantly higher in the 96 h sample. Significant decreases in lymphocytes, monocytes, neutrophils and eosinophils were noted from 48 h of storage on, while a significant decline in basophil counts were noted over the last two sampled timepoints. The coefficient of variation was greatest at the 96 h timepoint, indicating increased variability in measured parameters after 4 d of refrigeration. Plasma samples frozen at -20 °C showed a significant variation in ALT after 8 weeks, and increases in TP and TG after 20 weeks. Therefore, it is recommended that refrigerated tambaqui whole blood samples be analyzed within 24 h and frozen tambaqui plasma samples analyzed within 8 weeks.

Immuno-protective response of Asian seabass (Lates calcarifer) to inactivated vaccines against Streptococcus iniae and Vibrio harveyi

BACKGROUND

In this study, the protective immunity and immunogenicity of the monovalent and bivalent Streptococcus iniae and Vibrio harveyi vaccine were evaluated in Asian seabass. To analyze immune responses, 1200 Asian seabass with an average weight of 132.6 ± 25.4 g were divided into eight treatments in triplicates (50 fish per tank) as follows: S. iniae immunized by injection (SI), V. harveyi immunized by injection (VI), bivalent S. iniae and V. harveyi (SVI) immunized by injection, S. iniae immunized by immersion (SIM), V. harveyi (VIM) immunized by immersion, bivalent S. iniae and V. harvei (SVIM) immunized by immersion, phosphate-buffered saline (PBS) by injection (PBSI) and control group without vaccine administration (CTRL). Blood and serum samples were taken at the end of the 30th and 60th days. Then the vaccinated groups were challenged with two bacteria (S. iniae) and (V. harveyi) separately and mortality was recorded for 14 days.

RESULTS

This study reveals that there is no significant difference in the hematological parameters on the 30th and 60th days of the experiment in the vaccine-immunized groups compared to the CTRL group (P > 0.05). Meanwhile, there was no significant difference in the amount of serum albumin level, respiratory burst activity, and serum bactericidal activity in the vaccine-immunized groups compared to the CTRL group on the 30th and 60th days of the experiment (P > 0.05). Total protein on the 60th day (in the VI and SVI groups), globulin on the 30th day (in the VI and SVI groups) and the 60th day (in the VI group) compared to the CTRL and PBSI groups had a significant increase (P < 0.05). Complement activity (in the VI and SVI groups) and lysozyme (in the SI and SVI groups) increased significantly compared to the control group (P < 0.05). Serum antibody titer against S. iniae had a significant increase in the SI, VI, SVI and SVIM groups compared to the CTRL and PBSI groups (P < 0.05). Serum antibody titer against V. harveyi had a significant increase in the groups immunized with the vaccine compared to the CTRL and PBSI groups (P < 0.05). A significant increase in the relative percentage survival (RPS) following challenge with S. iniae in the SVI (86.6%), SI (83.3%,) and VI (73.3%) groups were observed compared to the CTRL (43.3%) and PBSI (40%) groups (P < 0.05). Also, a significant increase in the RPS after challenge with V. harveyi in the SVI group, VI 86.6%, SVI 83.3%, VIM 80% and SVIM 76.6% were observed compared to the CTRL (46.6%) and PBSI (50%) groups (P < 0.05).

CONCLUSION

Overall, the results demonstrated that the bivalent vaccine of S. iniae and V. harveywas able to produce significant immunogenicity and RPS in Asian seabass.

Impacts of florfenicol on immunity, antioxidant activity, and histopathology of Oreochromis niloticus: a potential protective effect of dietary spirulina platensis

The misuse of antibiotics enhances the development of resistant microorganisms and decreases the efficacy of treatments. Florfenicol (FF) is one of the antibiotics approved for use in aquaculture in Egypt. Because of its extensive usage, potential negative impacts on aquatic creatures are a major concern. This motivates us to search for an appropriate neoadjuvant to work synergistically with FF and reduce adverse effects. Results from this study will contribute towards improving the understanding of the impacts of FF on Oreochromis niloticus and the possible amelioratory effects of Spirulina platensis algae (SP). O. niloticus (n = 240; 40 ± 2.5 g) were fed on two diets supplemented with or without SP for 4 weeks, then divided into four treatments each in three replicates (n = 60/treatment). G1; was fed a control diet, and the other groups were fed diets supplemented with FF (10 mg /kg of BW, G2), SP (2 g/kg of diet, G3), or FF + SP (G4) for 10 days. Among the four groups, the SP group (G3) had the best immunostimulatory effects as observed by a significant (p < 0.05) elevation in phagocytic activity, phagocytic index, IL6, and TNF-α. The treatment with FF had significantly impacted hepatic and renal tissues, as the values of liver enzymes and creatinine demonstrated tissue deterioration and also resulted in oxidative stress, which was expressed by an increase of GPx, CAT, and SOD in (G2). Additionally, the combined FF + SP improved the hematological parameters and decreased the oxidative damage induced by FF (G4). Thus, it was clear that FF has harmful effects on O. niloticus and that SP can modulate such impacts. These data recommend the use of SP as an effective immunostimulant and a probable adjuvant to FF in O. niloticus diets to attain maximum disease resistance.

Automated Hematological Approach and Protein Electrophoretic Pattern in Tilapia (Oreochromis niloticus): An Innovative and Experimental Model for Aquaculture

This study aimed to assess the usefulness of two innovative automated methods (automated blood count counters and flow cytometry) for hematological investigation in Tilapia to make a contribution to the clinical diagnostics of this farmed species. Moreover, serum total proteins and their electrophoretic fractions (prealbumin, albumin, α-, β-, and γ-fraction), as health condition indicators, were assessed. The analysis of serum total proteins and electrophoretic fraction showed a normal and typical electrophoretic pattern of healthy fish (serum total proteins, 3.70 ± 0.62 g/dL; prealbumin, 0.44 ± 0.20 g/dL; albumin, 1.17 ± 0.66 g/dL; α-fraction, 1.49 ± 0.64 g/dL; β-fraction, 0.32 ± 0.16 g/dL; and γ-fraction, 0.29 ± 0.13 g/dL). The relationships between the values of red blood cells (RBCs), white blood cells (WBCs), and thrombocytes (TCs) obtained with the two automated methods were determined using Pearson correlation analysis. The results showed a significant positive correlation between automatic blood cell counting and flow cytometry analysis for RBCs (r = 0.97, p < 0.0001) and WBCs (r = 0.91, p < 0.0001), whereas no correlation was found for TCs (r = -0.11, p = 0.66). The preliminary results gathered in this study seem to highlight the usefulness of the new analytical techniques herein investigated in tilapia, suggesting their application in the hematological investigation of farmed fish species and their usefulness for monitoring the health and well-being of fish reared in aquaculture.

Stocking density affects immune and stress-related gene expression of Butter catfish (Ompok bimaculatus) fry in biofloc landscapes

Scientific research into fish wellness is critical, and the concerns about crowding-related stress due to increased stocking density are inevitable. Taking this into consideration, the study defines the physiological signature of Ompok bimaculatus (Butter catfish) in a biofloc system when subjected to varying levels of stocking density. Fish (mean weight = 1.21 g ± 0.08, n = 600) were randomly stocked in 40-L glass aquaria at stocking densities of 0.5 g/L (T1), 1 g/L (T2), 1.5 g/L (T3), and 2 g/L (T4) and fed a 35% protein diet. After the 90-day trial, the physio-biochemical, molecular, and tissue-level changes were assessed. An integrated biomarker response (IBR) analysis for the key stress indicators aided us in better understanding them. There was a significant difference in blood count between T1 and T4 (total erythrocyte count, hemoglobin, and packed cell volume). T1 had higher levels of globulin and total plasma protein, but T2 had higher levels of albumin. Only in T1 did the respiratory burst and lysozyme activity appear to be higher (p < 0.05). Increased stocking densities had a significant impact on the liver function enzymes, GOT and GPT (p < 0.05). In comparison to lower densities (T1 & T2), higher stocking density (T3 & T4) was found to raise glucose and cortisol levels (p < 0.05). Antioxidant enzymes such as catalase, glutathione-S-transferase, and malondialdehyde were found to be more pronounced in lower density tissues (T1). Furthermore, the IBR plots show that lower densities have better health than higher densities. At higher stocking densities, mRNA expression of HSP70, IL-1, and IL-20 increased (p < 0.05) in kidney and liver tissues. The Nrf-2 and Tlr-9 genes were also upregulated. Also, when stocking density was increased, tissue-level histo-architectural changes were more pronounced than when stocking density was kept low. The findings of this study show that the welfare of Butter catfish cultured at high density in biofloc systems suffers from severe stress, and therefore draw more attention to the development of a species-specific standard rearing methodology in the pursuit of a profitable aqua-farming enterprise.

An experiment on the glucose metabolite, serum electrolytes, and somatic characteristics of the Levantine Barbel Luciobarbus pectoralis (Heckel, 1843) under the effect of heavy metals

Levantine Barbel (Luciobarbus pectoralis) is a benthopelagic, subtropical native fish living in the inland waters of the Mediterranean region in Türkiye and Syria. Even though it is widely consumed locally, experimental observations on how heavy metals [zinc (Zn), copper (Cu), cadmium (Cd), and lead (Pb)] and their mixtures affect the fish are lacking. Several bioindicators of the fish exposed to heavy metals are the focus of the current investigation. Initially, Fulton condition factor (K) and hepato-somatic index (HSI) were utilized in the somatic characteristics of L. pectoralis. Then, changes in the level of glucose metabolite and electrolytes [sodium (Na+), potassium (K+), and chloride (Cl-)] of blood were determined by Architect C-800 auto-analyzer after exposure durations. The results of the experiments demonstrated that heavy metals can rapidly have a negative impact on the regulation of blood and somatic characteristics of fish. It was observed that the K index decreased in all metal groups at 24 and 96 h, while considerably increased in the 24-h effect of cadmium only (P ≤ 0.05). Along with that, in the 96-h effect of metals, Cu indicated the highest decrease in the HSI value (19.33%, P ≤ 0.05). In general, all heavy metal exposures caused the fish's glucose metabolite level to rise compared to the control (P ≤ 0.05). Furthermore, sublethal effects of metals at both durations caused considerable changes in blood electrolytes of the fish compared to control (P ≤ 0.05). Additionally, putative biomarkers in both durations had the greatest difference in toxic similarity under the Cu impact compared to the control, according to Hierarchical clustering and Euclidean distance metrics. Although the applied concentrations of Zn, Cu, Cd, and Pb and their mixture studied were generally within the limits of the various organizations and the surface water regulations, changes in ecophysiological and somatic indices were nonetheless seen in fish.

First Isolation of a Herpesvirus (Family Alloherpesviridae) from Great Lakes Lake Sturgeon (Acipenser fulvescens)

The lake sturgeon (Acipenser fulvescens; LST) is the only native sturgeon species in the Great Lakes (GL), but due to multiple factors, their current populations are estimated to be <1% of historical abundances. Little is known about infectious diseases affecting GL-LST in hatchery and wild settings. Therefore, a two-year disease surveillance study was undertaken, resulting in the detection and first in vitro isolation of a herpesvirus from grossly apparent cutaneous lesions in wild adult LST inhabiting two GL watersheds (Erie and Huron). Histological and ultrastructural examination of lesions revealed proliferative epidermitis associated with herpesvirus-like virions. A virus with identical ultrastructural characteristics was recovered from cells inoculated with lesion tissues. Partial DNA polymerase gene sequencing placed the virus within the Family Alloherpesviridae, with high similarity to a lake sturgeon herpesvirus (LSHV) from Wisconsin, USA. Genomic comparisons revealed ~84% Average Nucleotide Identity between the two isolates, leading to the proposed classification of LSHV-1 (Wisconsin) and LSHV-2 (Michigan) for the two viruses. When naïve juvenile LST were immersion-exposed to LSHV-2, severe disease and ~33% mortality occurred, with virus re-isolated from representative skin lesions, fulfilling Rivers’ postulates. Results collectively show LSHV-2 is associated with epithelial changes in wild adult LST, disease and mortality in juvenile LST, and is a potential threat to GL-LST conservation.

Blood biomarkers as diagnostic tools: An overview of climate-driven stress responses in fish

Global climate change due to anthropogenic activities affects the dynamics of aquatic communities by altering the adaptive capacities of their inhabitants. Analysis of blood provides valuable insights in the form of a comprehensive representation of the physiological and functional status of fish under various environmental and treatment conditions. This review synthesizes currently available information about blood biomarkers used in climate change induced stress responses in fish. Alterations in informative blood-based indicators are used to monitor the physiological fitness of individual fishes or entire populations. Specific characteristics of fish blood, such as serum and plasma metabolites, cell composition, cellular abnormalities, cellular and antioxidant enzymes necessitate adapted protocols, as well as careful attention to experimental designs and meticulous interpretation of patterns of data. Moreover, the sampling technique, transportation, type of culture system, acclimation procedure, and water quality must all be considered for valid interpretation of hemato-biochemical parameters. Besides, blood collection, handling, and storage time of blood samples can all have significant impacts on the results of a hematological analysis, so it is optimal to perform hemato-biochemical evaluations immediately after blood collection because long-term storage can alter the results of the analyses, at least in part as a result of storage-related degenerative changes that may occur. However, the scarcity of high-throughput sophisticated approaches makes fish blood examination studies promising for climate-driven stress responses in fish.

Haematology reference values for Dicentrarchus labrax and Sparus aurata: A systematic review and meta-analysis

Haematological parameters are frequently used as physiological indicators in aquaculture studies. These parameters also have extended applications in clinical evaluation, diagnosis and prognosis in fish health status. However, no normal reference range of values has been demonstrated in depth for any of these haematological parameters for the European sea bass (Dicentrarchus labrax) or gilthead seabream (Sparus aurata). The main objective of this article is to present for the first time through extended literature review, the haematological parameters normal range values for the two most important aquaculture fish species farmed in Mediterranean Sea, D. labrax and S. aurata, and to demonstrate their similarities and their differences. In this article, we also discuss the environmental and external factors affecting their normal blood parameters values and we propose fundamental guidelines on the reporting units.

Biological Responses of Nile tilapia Oreochromis niloticus as Influenced by Dietary Florfenicol

Antibiotics are used in the treatment of bacterial diseases in commercial aquaculture. In this study, we the biological responses of Oreochromis niloticus juveniles upon dietary florfenicol (FFC) administration at 15 mg (1×) and 45 mg kg biomass^-1 day^-1 (3×) for 10 days in terms of feed intake, survival, biomass, hematological, erythro-morphological, serum biochemical, and histopathological aberrations as compared with controls. FFC caused a dose-dependent reduction in feed intake, survival, and biomass, with marked variations in hematology, hematological indices, and erythrocytic cellular and nuclear abnormalities, suggesting its apparent cytotoxic and nucleotoxic effects. The serum biomarkers increased significantly in a dose-dependent manner, except for calcium and chloride, which decreased significantly. The therapeutic dose (1×) group exhibited marked histopathological aberrations, such as renal tubular epithelial degeneration and a widened lumen in the kidney, as well as glycogen-type vacuolation and cytoplasmic degeneration in the liver during the dosing period. The extent of kidney and liver tissue damage was more prominent in the 3× group. The 1× serum biomarker levels became normal, with the exception of alkaline phosphatase, within 3 weeks of suspension of dosing. The recovery of the measured parameters and histopathological and erythro-morphological changes suggested that the therapeutic dietary biological responses induced by FFC are reversible and safe for O. niloticus.

Effect of Supplementation of Vitamin A on Growth, Haemato-Biochemical Composition, and Antioxidant Ability in Cyprinus carpio var. communis

Vitamin A requirement in fingerling common carp, Cyprinus carpio var. communis (1.64 ± 0.02 g; ABW ± SD), was evaluated by conducting a 10 week growth experiment. Casein-gelatin-based test diets representing six graded levels of vitamin A (0, 0.03, 0.07, 0.11, 0.15, and 0.19 g/kg, dry diet) were designed and fed to the triplicate group of fish at 08:00 and 16:00 hrs at the rate of 4% body weight per day. Growth parameters like live weight gain (LWG %), feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR), and body protein deposition (BPD) improved significantly (P < 0.05) with each elevated dietary vitamin A level and found maximum growth rate along with the best- FCR at 0.11 g/kg diet. Dietary vitamin A levels also significantly (P < 0.05) affected haematological parameters of the fish. Highest haemoglobin (Hb), erythrocyte count (RBC), haematocrit content (Hct %), and lowest leucocyte count (WBC) were observed at 0.11 g/kg vitamin A fed diet compared to all the diets. Highest protein and lowest fat content were observed in the group of fingerlings fed with 0.11 g/kg vitamin A containing diet. Blood and serum profile also showed some significant (P < 0.05) differences with elevating concentration of dietary vitamin A levels. Serum parameters like aspartate aminotransferase (AST), alanine aminotransferase (ALT), and cholesterol values decreased significantly (P < 0.05) at 0.11 g/kg vitamin A fed diet compared to control diet. However, except albumin the other electrolytes improved significantly (P < 0.05) and maximal values of these parameters were also evident at 0.11 g/kg of vitamin A fed diet. Better value of TBARS was found in the group that fed 0.11 g/kg vitamin A diet. Hepatosomatic index and condition factor improved significantly (P < 0.05) with fish fed at optimal dose 0.11 g/kg of vitamin A diet. Based on quadratic regression analysis of LWG%, FCR, BPD, Hb, and calcium values of C. carpio var. communis against the varying levels of dietary vitamin A, an optimum growth, best FCR, higher BPD, Hb, and Ca values lie in the range of 0.10 to 0.12 g/kg diet, respectively. The data generated during this study would be important in developing vitamin A balanced feed for successful intensive culture of C. carpio var. communis.

Left shift and toxic change in heterophils and neutrophils of non-mammalian vertebrates: A comparative review, image atlas, and practical considerations

Heterophils and neutrophils are important first cellular responders to inflammatory conditions. In addition to quantitative shifts in the numbers of these cells in blood, inflammatory disease states often have accompanying increases in immature precursor stages (left shift) and/or evidence of toxic change on blood film evaluation. Recognition of left shift and toxic change morphologies is a salient diagnostic finding with clinical relevance across species. The objectives of this report are to (a) review heterophil and neutrophil function and structure across the vertebrate animal kingdom, (b) compare morphologic features of left shift and toxic change in heterophils and neutrophils of non-mammalian vertebrates (NMV) to mammals, (c) provide an image guide demonstrating the breadth of morphologic diversity of heterophil and neutrophil lineages in health and disease across taxa, and (d) discuss practical considerations for clinical pathologists and other professionals involved in the recognition and interpretation of observations in the inflammatory leukogram of NMV.

Influence of winter water temperatures on the physiological state of carp (Cyprinus carpio)

In the winter period, water temperature is one of the main factors influencing the physiological state of fish. Its optimal and stable indicator during the whole winter period guarantees high yield of fish and its quality. To this date, the winter period is characterized by elevated temperatures with acute fluctuations. In this work, the main object of study is carp (Cyprinus carpio) at the age of six (young-of-the-year) and ten (one-year) months. The aim of this study was to determine how much the period of the optimal winter water temperatures decreased and how this affected the weight and fatness, hematological profiles, erythrocyte indices and basic biochemical parameters of carp muscle tissue. As a result of research, it was found that optimal winter water temperatures decreased by an average of two months, which affected the physiological state of carp. Consequently, there was a decrease in body weight and fatness. Dissolved oxygen level, pH, nitrites, nitrates and hardness were normal, while oxidation was increased. Muscle fat and protein levels decreased to critical levels, at the same time, moisture and ash levels were noted to increase. The total content of red blood cells decreased, however, the level of hemoglobin, mean corpuscular hemoglobin (MCH), mean cell hemoglobin concentration (MCHC) increased. With increasing hemoglobin content and concentration, mean corpuscular volume (MCV) decreased. After wintering, the number of white blood cells increased. The biochemical profile of carp blood showed a decrease in total protein in blood serum, albumin, triglycerides, cholesterol and glucose. After wintering, there was an increase in creatinine, phosphorus and calcium. Knowing how much the period of optimal winter temperatures has shortened, and how this affects the state of carp at the physiological level, will provide an opportunity to develop recommendations for improving wintering technologies. Considering the dynamics of climate change, the research in this area is promising.

Immunomodulatory effects of Yarrowia lipolytica as a food additive in the diet of Nile tilapia

The use of yeasts as a dietary additive for fish can act as a source of nutrients and as an immunostimulant. This work aimed to evaluate the effects of the fermented biomass of the yeast Yarrowia lipolytica as a food additive on zootechnical and hematological parameters, and on immune response in the plasma and kidney of Nile Tilapia (Oreochromis niloticus). After supplementation with 3, 5, and 7% of the yeast biomass for 35 days, the blood and tissues of the animals of each experimental group were collected for analysis. The addition of this biomass in the feed promoted an improvement of zootechnical parameters in tilapia. There was also a rise in the number of neutrophils (groups with 3, 5, and 7%) and monocytes (group 3, 5, and 7%) compared with the control group. Moreover, there was an increase in the levels of lysozyme, myeloperoxidase, and nitrite/nitrate content in the blood of animals fed with yeast biomass. On the other hand, there were no observed alterations in survival and hematological parameters of animals fed with yeast biomass. In the analysis of the kidney, the addition of biomass in feed promoted an increase in levels of myeloperoxidase (group with 3%) but did not alter the levels of lysozyme and nitrite/nitrate content. In conclusion, this study demonstrated that Y. lipolytica had growth and immunostimulatory effects on Nile tilapia. These findings strongly suggest the potential application of a Y. lipolytica-based immunostimulant for tilapia aquaculture.

Comparative study of peripheral blood cells in two marine fishes (Synechogobius hasta and Sebastes schlegelii): Morphological and cytochemical characterization

The morphology, cell size and relative number of peripheral blood cells in two teleosts, Synechogobius hasta and Sebastes schlegelii, were compared using different staining methods. The results showed significant differences in cell size. The percentage of monocytes in S. hasta was greater than that in S. schlegelii (P < 0.01); however, the opposite results were obtained in the percentage of lymphocytes and thrombocytes. The two fishes shared common cytochemical-staining results, which showed that both erythrocytes were negative for all cytochemical staining; monocytes were strongly positive for PAS and positive for SBB and NAE; lymphocytes were negative for SBB, POX and NAE; neutrophils were positive for SBB and NAE; and thrombocytes were negative for SBB, ALP, POX and NAE. However, species specificity existed in the cytochemical properties. For S. hasta, monocytes were strongly positive for ALP and ACP; lymphocytes were strongly positive for ALP and weakly positive for ACP; neutrophils were strongly positive for ACP and POX; and thrombocytes were weakly positive for PAS and positive for ACP. Unlike S. hasta, monocytes were strongly positive for ACP and positive for ALP in S. schlegelii; lymphocytes were positive for ALP and partially positive for PAS; neutrophils were positive for ACP and POX; and thrombocytes were negative for PAS and ACP. The POX activity of monocytes in S. hasta was greater than that in S. schlegelii (P < 0.05), while the POX activity of neutrophils and the NAE activity of monocytes in S. hasta were significantly greater than those in S. schlegelii (P < 0.01). The results of this study can be used as a reference for the construction of haematological parameters in S. hasta and S. schlegelii for the assessment of fish health and can provide a research basis for fish diseases and immunity.

Blood Analyte Changes of Wild-Caught Adult Almaco Jack in Response to Acclimation to Recirculating Aquaculture Systems and Hyposalinity Treatment

Despite the utility of blood analyte evaluation as a diagnostic tool to assist in monitoring the health of marine fishes, baseline data are often lacking for many commercially important finfish species. The objective of this study was to compare hematology and plasma chemistry data for adult wild-caught Almaco Jack Seriola rivoliana at time of capture and again following a period of acclimation to a recirculating aquaculture system and hyposalinity treatment. A total of 30 clinically healthy adult fish were caught via hook and line in the eastern Gulf of Mexico, approximately 120 mi offshore from Madeira Beach, Florida. Blood was collected from a subset of these fish (n = 13) immediately after capture and again at 16 weeks postcapture from another subset (n = 12) following a 45-d antiparasitic hyposalinity treatment. A 19% increase in fish body weight was observed during the study period (16 weeks) and no overt health issues or mortality were noted. Compared to fish that were sampled immediately following capture, several significant differences (P < 0.05) were observed. Absolute white blood cells were lower in captive held fish, suggesting biological variation, antigenic stimulation in wild fish, and/or immunosuppression associated with stress in captive held fish. Lower sodium, chloride, and calculated osmolality indicate osmoregulatory adjustments following the hyposalinity treatment by 16 weeks postcapture. Other observed plasma biochemical differences presumptively reflect dietary and/or environmental changes, or physiological variation following acclimation to captive culture conditions. This study reports baseline blood analyte data of wild-caught Almaco Jack and documents hematological and plasma biochemical responses to their new environment as captive broodstock. Baseline hematological and plasma biochemistry data obtained during this study are the first reported for this species.

Blood Transcriptomics of Turbot Scophthalmus maximus: A Tool for Health Monitoring and Disease Studies

Simple Summary

The analysis of blood gene expression is emerging as a relevant source of information about the health status of an organism. While these investigations are increasingly performed in human and terrestrial animals, their potential is still underexplored in fish pathology. The aim of this work was to analyze the blood transcriptional profile of a commercially important flatfish species, turbot (Scophthalmus maximus), in healthy and diseased specimens. The analysis of the most expressed genes in healthy fish indicated that turbot red blood cells have important immunological functions. In diseased fish, parasitized by a myxozoan, the blood analysis reflected a broad inhibition of the immune response followed by intense inflammatory activation in heavy infections. The results showed that turbot response appears delayed, dysregulated and ineffective in stopping the infection. Particularly, a proper development of the adaptive immune response was lacking. This study points out that blood gene expression profiling is a reliable tool for health monitoring, as well as to advance in the knowledge of fish immunity and diseases.

Abstract

Blood transcriptomics is emerging as a relevant tool to monitor the status of the immune system and assist in diagnosis, prognosis, treatment and pathogenesis studies of diseases. In fish pathology, the potential of transcriptome profiling of blood is still poorly explored. Here, RNA sequencing was applied to analyze the blood transcriptional profile of turbot (Scophthalmus maximus), the most important farmed flatfish. The study was conducted in healthy specimens and specimens parasitized by the myxozoan Enteromyxum scophthalmi, which causes one of the most devastating diseases in turbot aquaculture. The blood of healthy turbot showed a transcriptomic profile mainly related to erythrocyte gas transportation function, but also to antigen processing and presentation. In moderately infected turbot, the blood reflected a broad inhibition of the immune response. Particularly, down-regulation of the B cell receptor signaling pathway was shared with heavily parasitized fish, which showed larger transcriptomic changes, including the activation of the inflammatory response. Turbot response to enteromyxosis proved to be delayed, dysregulated and ineffective in stopping the infection. The study evinces that blood transcriptomics can contribute to a better understanding of the teleost immune system and serve as a reliable tool to investigate the physiopathological status of fish.

Hematological and cytochemical characteristics of peripheral blood cells in the argus snakehead (Ophiocephalus argus Cantor)

BACKGROUND

The argus snakehead (Ophiocephalus argus Cantor) is a highly nutritious, freshwater, cultured bony fish with a high economic value. The health of the fish is closely related to its blood cells, which are critical for oxygen transport, natural defense, and immunity. We investigated the morphometry, microstructure, and cytochemical characteristics of the peripheral blood cells of O. argus. Our results may provide the basic reference values needed to monitor the health of this fish for large-scale cultivation.

METHODS

The number of blood cells in O. argus were counted on a hemocytometer and their size was measured using a micrometer under light microscope. The morphology and classification of the blood cells were studied using Wright's staining and the cytochemical characteristics were studied using seven chemical stains including peroxidase (POX), Sudan black B (SBB), periodic acid-Schiff (PAS), acid phosphatase (ACP), alkaline phosphatase (ALP), chloroacetic acid AS-D naphthol esterase (AS-D), and α-naphthol acetate esterase (α-NAE).

RESULTS

The peripheral blood cells in O. argus can be classified as erythrocytes, leukocytes, and thrombocytes; of which, females had 2.9597 million/mm3, 88,400/mm3, and 43,600/mm3, respectively, and males had 3.0105 million/mm3, 105,500/mm3, and 34,000/mm3, respectively. Leukocytes consisted of neutrophils, monocytes, large lymphocytes, and small lymphocytes. Eosinophils and basophils were not found. Monocytes were the most numerous leukocytes identified, followed by neutrophils and small lymphocytes, while large lymphocytes were the least frequently identified. Cytochemical staining showed that erythrocytes were only positive for PAS staining. Neutrophils were strongly positive for POX, SBB, and ACP, and positive for all the other cytochemical stains. Monocytes were positive for PAS and α-NAE and were weakly positive for ACP and AS-D staining. Large lymphocytes were positive for PAS and were weakly positive for ALP, AS-D, and α-NAE staining. Small lymphocytes were positive for PAS and weakly positive for AS-D and α-NAE staining. Thrombocytes were positive for PAS and were weakly positive for ACP and AS-D, but negative for the remaining cytochemical stains. The morphology of peripheral blood cells in O. argus was generally similar to that of other fish species, while the cytochemical staining patterns showed clear species specificity.

Hematology and blood biochemistry profile of the freshwater stingray Potamotrygon magdalenae as a tool for population assessment in artificial environments

Hematological and blood biochemical reference information is important to establish physiological status of freshwater stingray populations and improve care and management protocols in artificial environments. Here, we used a commercial freshwater stingray with high mortality rates in the market (Potamotrygon magdalenae), as an example to understand how artificial environments and handling protocols influence physiological status of captive freshwater stingrays. To this purpose, blood from five adult males and six adult females was collected to perform complete blood counts and blood chemistry analyses. All sampled animals showed good body condition with no differences between sexes. Differences between sexes were only found for the differential count of lymphocytes. Red blood results were consistent with previously studied potamotrygonids while white blood results showed higher values of leukocytes, thrombocytes, heterophils and lymphocytes in P. magdalenae compared to other Potamotrygonids. All types of leukocytes described for elasmobranchs were found except neutrophils and basophils. Blood metabolites showed an influence of ex situ diet in total protein, triglycerides and cholesterol. Glucose results were consistent while urea showed lower levels than those recorded for other freshwater stingrays. These results highlight the importance of physical, physiological and health analysis in freshwater stingrays as a part of welfare assessment to improve monitoring protocols and survival rates in public or private aquaria.

Growth and health status of Pangasionodon hypophthalmus reared under manipulated photoperiod conditions

Background: In general, the length of photoperiod affects the physiology of Pangasionodon hypophthalmus. This study aimed to understand the growth and health status of this fish reared under manipulated photoperiods.

Methods: The study was conducted between June to August 2020[A1] . Three treatments were applied: control (natural photoperiod); 18 hours of darkness (18D6L; tanks were placed under a dark tarp tent for 18 hours); and 24 hours of darkness (24D0L; tanks were placed under a dark tarp tent continuously). Three replications were performed per treatment. At baseline, fish were approx. 7.5 cm  [A2] total length (TL) and 4 g body weight (BW), and were reared in circular plastic tanks (100 L; 30 fish/tank) with aerators and filters, and fed with commercial fish feed pellet (2 times/day to satiation). Fish growth and survival were studied once/week, and blood and tissue samples were taken at the end of the experiment (8 ^th week). Tissue was formalin fixed and HE stained.

Results: The survival of fish in all treatment was 100%. The fish reared in 24D0L and 18D6L grew better than control, achieving mean TL of 23 cm and BW of 98 g (control = 19 cm TL and 72 g BW). There was no difference in hematology condition or tissue structure between the three groups. Tissue structure of gill, kidney and liver were normal, but light abnormality due to parasites was present in the gill of fish reared in 24D0L. Blood samples for all three groups showed mean red blood cell count of 1,800,000 cells/ml and white blood cell (WBC) count of 55,200 cells/ml. WBC consisted of lymphocyte 65%, monocyte 24%, thrombocyte 6%, neutrophil 3%, eosinophil 1% and basophile 1%.

Conclusion: Data obtained indicate that a short photoperiod improves the growth of P. hypophthalmus fish and does not negatively affects their health.

Computed tomographic and ultrasonographic diagnosis with successful excision of a lipoma in a shusui koi (Cyprinus carpio)

CASE DESCRIPTION

A client-owned 12-year-old 10.3-kg (22.7-lb) female shusui koi (Cyprinus carpio) was evaluated because of an ulcerated mass on the left body wall, hyporexia, and decreased activity.

CLINICAL FINDINGS

The patient was anesthetized with a solution of eugenol in water for all examinations and procedures. An approximately 7 × 5-cm smooth, raised, ulcerated, and firm mass was present ventral and lateral to the dorsal fin on the left body wall. Whole-body CT images obtained before and after contrast administration revealed an encapsulated, homogeneous, fat-opaque mass within the muscle. The mass was fat echoic with poor vascularity on ultrasonographic examination. Histologic evaluation of an ultrasound-guided needle biopsy specimen was suggestive of a lipoma.

TREATMENT AND OUTCOME

The mass was excised, and the fish was placed in water with 0.3% salinity for 3 weeks after surgery. Postoperative antimicrobial administration was not indicated, and additional postoperative analgesic administration was considered impractical. The patient had noticeable improvement in appetite and activity with no indication of discomfort immediately following surgery. Five weeks after surgery, the incision site had healed with minimal scarring, and evaluation of CT images revealed no evidence of mass regrowth or regional osteomyelitis.

CLINICAL RELEVANCE

Antemortem evaluation and diagnosis of a lipoma in a teleost with subsequent excision was described. This report highlighted the logistic challenges associated with anesthesia, advanced diagnostic imaging, and surgery in fish and showed that they can be successfully overcome so that high-level medical care can be provided to such patients.

Cold-Resistant Heterotrophic Ammonium and Nitrite-Removing Bacteria Improve Aquaculture Conditions of Rainbow Trout (Oncorhynchus mykiss)

The aim of this study was isolation and characterization of heterotrophic bacteria capable of ammonium and nitrite removal at 15 °C (optimal temperature for growing rainbow trout Oncorhynchus mykiss). Environmental isolates were grown in liquid media containing ammonium or nitrite, and best strains in terms of growth and ammonium or nitrite removal were identified via 16S rRNA sequencing. Dyadobacter sp. (no. 68) and Janthinobacterium sp. (no. 100) were selected for optimal adaptation to growth at 15 °C and best ammonium and nitrite removal (P < 0.05), respectively. A heterotrophic ammonium and nitrite removal (HAN) microbial complex, containing selected strains, was prepared and applied in a trout culture system. After 10 days, the effect of microbial HAN complex was investigated in terms of ammonium and nitrite removal, as well as stress and immune indices present in the plasma of cultivated trout. Compared to a standard cultivation setup, addition of the HAN complex had a clear beneficial effect on keeping the un-ionized ammonia and nitrite level below prescribed standards (P < 0.05). This resulted in reduction of stress and immune reactions of cultivated fish (P < 0.05), leading to an augmentation of final weight and survival. Application of the selected microbial complex resulted in a significant improvement of the aquaculture ecosystem.

Multidisciplinary haematology as prognostic device in environmental and xenobiotic stress-induced response in fish

The variations of haematological parameters hematocrit, hemoglobin concentration, leukocyte and erythrocyte count have been used as pollution and physiological indicators of organic dysfunction in both environmental and aquaculture studies. These parameters are commonly applied as prognostic and diagnostic tools in fish health status. However, there are both extrinsic and intrinsic factors to consider when performing a blood test, because a major limitation for field researchers is that the "rules" for animal or human haematology do not always apply to wildlife. The main objective of this review is to show how some environmental and xenobiotic factors are capable to modulating the haematic cells. Visualizing the strengths and limitations of a haematological analysis in the health assessment of wild and culture fish. Finally, we point out the importance of the use of mitochondrial activities as part of haematological evaluations associated to environment or aquaculture stress.

Effects of replacing fish meal with soybean meal on growth performance, feed utilization and physiological status of juvenile obscure puffer, Takifugu obscurus

An 8-week feeding trial was conducted to evaluate the growth performance, feed utilization and physiological status of obscure puffer, Takifugu obscurus (13.03 ± 0.14 g) fed diets in which fish meal (FM) was replaced with various levels of dehulled and defatted soybean meal (SBM): 0% (SBM0), 15% (SBM15), 30% (SBM30), 45% (SBM45), 60% (SBM60) and 75% (SBM75). No significant differences were observed in weight gain and specific growth rate (SGR) of fish when FM replacement level was lower than 30%, and the broken-line model of SGR showed the maximum replacement level was 40%. Fish fed the SBM-containing diets had a lower red blood cell value compared to the control. The hemoglobin and methemoglobin values showed a declining tendency as dietary SBM level increased. Plasma triacylglycerol, cholesterol and low-density lipoprotein cholesterol levels also showed a decreasing trend that was associated with the reduced crude lipid content of whole body as dietary SBM level increased. The activities of alanine aminotransferase and aspartate aminotransferase in fish fed the SBM-containing diets were all higher than those fed the control diet while glutathione peroxidase and catalase activities were lower than the control group. Results indicated that up to 40% FM protein, based on the broken-line analysis of SGR, can be replaced with SBM in diet for obscure puffer juveniles with supplemental lysine, methionine and taurine.

Camellia sinensis supplemented diet enhances the innate non-specific responses, haematological parameters and growth performance in Mugil cephalus against Photobacterium damselae

This study evaluated the effect of dietary supplementation of Camellia sinensis leaf-extract on non-specific immune responses and disease resistance of Mugil cephalus fingerling against P. damselae. Fish were fed with 0 (unsupplemented), 50, 100 and 200 mg/kg of green tea extract (GTE) supplemented diets. Results indicated that GTE decreased mortality in M. cephalus in a dose-dependent manner after challenge with P. damselae. Haematological parameters containing RBC, Hct, Hb and WBC and growth performance (weight gain) showed remarkable changes in comparison with control group. In addition, the phagocytic (PA) and respiratory burst activity (RBA) significantly increased in M. cephalus, fed 100 and 50, 100 and 200 mg/kg GTE, respectively. Lysozyme statistically increased in GTE supplemented fish. Overall, our results indicated that incorporation of C. sinensis supplemented diet at 100 and 200 mg/kg doses significantly enhanced the immune responses in M. cephalus and that the mortality percentage could be remarkably reduced after challenging the fish against P. damselae.