Hematological characteristics of the spotted rose snapper Lutjanus guttatus (Steindachner, 1869) healthy and naturally infected by dactylogyrid monogeneans

Heavy Metals Assessment and Health Risk to Consumers of Two Commercial Fish Species from Polyculture Fishponds in El-Sharkia and Kafr El-Sheikh, Egypt: Physiological and Biochemical Study

Metal pollution is a major environmental concern worldwide, especially in Egypt. The aquaculture industry uses widespread artificial feeds to stimulate fish production, leading to metal accumulation in the aquatic environment. Heavy metal concentrations (HMCs) in sediments, water, and tissues were studied to study the effect of pollution levels on heamatological, and biochemical, immunological aspects of farmed fish as well as on human health. Results declared that the HMC levels in the water and sediment were significantly different between El-Sharkia and Kafr El-Sheikh fishponds (T-test, p < 0.05). This was supported by the metal pollution index in the water and sediment, indicating that El-Sharkia fishponds (ES fishponds) were more contaminated than Kafr El-Sheikh fishponds (KES fishponds). Also, HMCs in fish tissues were significantly increased in fish cultivated in ES fishponds than in KES fishponds. Haematological, immunological, and biochemical alterations of Bolti (Oreochromis niloticus) and Topara (Chelon ramada) fish were significantly different within the different fish species as well as the different fishponds. From the human health perspective, the THQ-HMC and HI-HMC associated with the consumption of muscle suggest a safe non-carcinogenic risk to human health. In contrast, cadmium poses a cancer risk to children who consume the muscular tissue of Bolti fish from ES fishponds, which should be regarded as a warning sign based on data indices and a human health perspective. In order to minimise HMC pollution in the aquaculture sector, it is advisable to take possible assessments and carry out continuous monitoring considering international WHO/FAO assessments.

The haematology of clinically healthy, farmed juvenile Asian seabass (Lates calcarifer Bloch)-reference intervals, and indicators of subclinical disease

This study establishes the blood reference intervals (RIs) for clinically healthy and farmed juvenile Asian seabass (Lates calcarifer), within 4-6 weeks after stocking into flow-through, marine aquaculture systems. The 90% percentile RIs (n = 156, mean bodyweight 41.8 g) are as follows: glucose (GLU) 2.4-11.3 mmol/L, haematocrit (Hct) 18.9%-39.2%, haemoglobin concentration (Hb) 56.0-85.0 g/L, total plasma protein (TPP) 56.0-77.0 g/L, total red blood cell (RBC) count 4.1-11.2 × 1012 /L, total white blood cell (WBC) count 5.3-69.9 × 109 /L, total lymphocytes 4.7-51.4 × 109 /L, monocytes 0.3-16.2 × 109 /L and heterophils count 0.6-8.4 × 109 /L. Pearson's method analysis showed weak but significantly positive correlations between fish bodyweight and Hct, Hb, TPP and total RBC count (p < 0.05). Histopathology of 42 of the 156 clinically healthy fish used to derive the RIs, with blood values within the 90% percentile range, did not exhibit any abnormal pathology. In contrast, histopathology from a different group of clinically healthy L. calcarifer (n = 72, mean bodyweight 31.3 g) with blood values falling outside of these established 90% percentile RIs showed that 25% of these fish had severe, chronic granulomatous enteritis, and 13% had severely depleted lipid stores in their liver. Point biserial correlation analysis of blood values from this second group of 72 fish showed that elevated total WBC, monocyte and heterophil counts and reduced Hct levels are significantly associated (p < 0.05) with the occurrence of severe, chronic granulomatous enteritis and depleted lipid stores in their liver. Reduced blood GLU and TPP levels in the second group of fish were significantly associated with fish that had depleted lipid stores in liver (p < 0.05), corroborating a period of malnutrition. This study is among the first to establish blood RIs for clinically healthy, farmed juvenile L. calcarifer and detection of subclinical diseases in fish to support early intervention.

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.

Extreme climate scenario and parasitism affect the Amazonian fish Colossoma macropomum

Global warming caused by greenhouse gases accumulation, in particular carbon dioxide, is the major current environmental challenge, as it will affect all life forms over the next decades. Aquaculture, a fast growing food production sector, is already facing the effects of global warming. The fish immune system is expected to be especially affected by increased temperature and carbon dioxide, mainly when associated to infectious diseases outbreaks. Here, we experimentally investigated the associated effects of an extreme climate scenario and two levels of monogenean parasitism on the hematological and immunological response of an important Amazon fish for continental aquaculture: Colossoma macropomum. Individuals of C. macropomum with low and high levels of parasitism were exposed to current and extreme climate scenarios (4.5 °C and 900 ppm CO₂ above current levels). We characterized their hematological profile using classical methods, and their immune-related gills gene expression (HSP70, IL-1β and IL-10) using quantitative real-time polymerase chain reaction (qPCR). After 7 days of exposure, we observed that exposure to extreme climate scenario caused rapid increase of parasitism intensity and likely acute inflammation, indicated by the higher expression of HSP70 and IL-1β. The IL-10 gene was downregulated in both groups exposed to extreme climate scenario, contrasting with animals exposed to current scenario. Thus, in the current scenario, the parasitized tambaqui showed a response to the tissue damage, which was not observed in the animals exposed to the extreme scenario.

Cumulative effects of municipal effluent and parasite infection in yellow perch: A field study using high-throughput RNA-sequencing

Multiple metabolic, immune and reproductive effects have been reported in fish residing in effluent-impacted sites. Natural stressors such as parasites also have been shown to impact the responses of organisms to chronic exposure to municipal effluent in the St. Lawrence River (Quebec, Canada). In order to comprehensively evaluate the cumulative impacts of anthropogenic and natural stressors on the health of yellow perch, differential mRNA transcription profiles were examined in juvenile females collected from effluent-impacted and upstream sites with low or high infection levels of the larval trematode Apophallus brevis. Transcriptomics was used to identify biological pathways associated with environmental exposure. In total, 3463 isoforms were differentially transcribed between sites. Patterns reflecting the combined effects of stressors were numerically dominant, with a majority of downregulated transcripts (68%). The differentially expressed transcripts were associated with 27 molecular and cellular functions ranging from cellular development to xenobiotic metabolism and were involved in the development and function of 13 organ systems including hematological, hepatic, nervous, reproductive and endocrine systems. Based on RNA-seq results, sixteen genes were measured by qPCR. Significant differences were observed for six genes in fish exposed to both stressors combined, whereas parasites and effluent individually impacted the transcription of one gene. Lysozyme activity, lipid peroxidation, retinol-binding protein and glucose-6-phosphate dehydrogenase were selected as potential biomarkers of effects to study specific pathways of interest. Lipid peroxidation in perch liver was different between sites, parasite loads, and for combined stressors. Overall, results indicated that juvenile yellow perch responded strongly to combined parasite and effluent exposure, suggesting cumulative effects on immune responses, inflammation and lipid metabolism mediated by retinoid receptors. The present study highlight the importance of using a comprehensive approach combining transcriptomics and endpoints measured at higher levels of biological organization to better understand cumulative risks of contaminants and pathogens in aquatic ecosystems.

Hematological and biochemical characteristics during the transport of dog snapper Lutjanus jocu (Perciformes: Lutjanidae)

ABSTRACT The objective of this study was to evaluate stress responses in dog snapper (Lutjanus jocu) during transport by evaluating their hematological and biochemical responses. Twenty-five wild dog snapper specimens were used in the experiment (220 ± 68 g and 24.5 ± 2.5 cm total length). Blood samples were collected prior to transport (control), and fish were placed in two transport boxes, one with anesthetic and one without anesthetic. Immediately after transport and after 24 h, blood was collected from the fish that underwent each treatment (with anesthetic and without anesthetic). Biochemical and hematological results demonstrated the inefficiency of benzocaine as a stress reliever during handling and transport. Biochemical parameters revealed the effects of stress during transport, and after 24 h, glucose levels and hematological parameters (hemoglobin, erythrocytes, leukocytes, neutrophils and MCH) showed a tendency to return to control levels. This study is the first to report stress response measurements of hematological and biochemical indicators in dog snapper, representing an important basis for the planning of future experiments involving the transport and handling of this fish species.

Physiological responses of reared sea bream (Sparus aurata Linnaeus, 1758) to an Amyloodinium ocellatum outbreak

Amyloodiniosis represents a major bottleneck for semi-intensive aquaculture production in Southern Europe, causing extremely high mortalities. Amyloodinium ocellatum is a parasitic dinoflagellate that can infest almost all fish, crustacean and bivalves that live within its ecological range. Fish mortalities are usually attributed to anoxia, associated with serious gill hyperplasia, inflammation, haemorrhage and necrosis in heavy infestations; or with osmoregulatory impairment and secondary microbial infections due to severe epithelial damage in mild infestation. However, physiological information about the host responses to A. ocellatum infestation is scarce. In this work, we analysed the proteome of gilthead sea bream (Sparus aurata) plasma and relate it with haematological and immunological indicators, in order to enlighten the different physiological responses when exposed to an A. ocellatum outbreak. Using 2D-DIGE, immunological and haematological analysis and in response to the A. ocellatum contamination we have identified several proteins associated with acute-phase response, inflammation, lipid transport, homoeostasis, and osmoregulation, wound healing, neoplasia and iron transport. Overall, this preliminary study revealed that amyloodiniosis affects some fish functional pathways as revealed by the changes in the plasma proteome of S. aurata, and that the innate immunological system is not activated in the presence of the parasite.

Fish Hematology and Associated Disorders

Fish health is a growing concern as pets, education, and aquaculture evolves. For the veterinary staff, fish handling, diagnostics, medicine, and surgery may require specialized training and equipment in comparison with terrestrial and arboreal animals, simply because of their aquatic nature and diversity. Fish hematology is one diagnostic tool that may not require additional equipment, may be inexpensive, and provide useful information in guiding treatment options. Challenges involving hematology may include handling and restraint, venipuncture, evaluation, and interpretation. In this article, strategies for these challenges are discussed for teleost (bony fish) and elasmobranch (cartilaginous fish) fish types.

Fish hematology and associated disorders

Fish health is a growing concern as pets, education, and aquaculture evolves. For the veterinary staff, fish handling, diagnostics, medicine, and surgery may require specialized training and equipment in comparison with terrestrial and arboreal animals, simply because of their aquatic nature and diversity. Fish hematology is one diagnostic tool that may not require additional equipment, may be inexpensive, and provide useful information in guiding treatment options. Challenges involving hematology may include handling and restraint, venipuncture, evaluation, and interpretation. In this article, strategies for these challenges are discussed for teleost (bony fish) and elasmobranch (cartilaginous fish) fish types.

Ultrastructure of novel thrombocytes in the dog snapper Lutjanus jocu

Myxosporean cysts containing spores of Henneguya sp. were observed in the gills of the dog snapper Lutjanus jocu. Adjacent to the cysts were capillaries, allowing observation of peripheral blood cells. Numerous white blood cells displaying uncommon cytoplasmic projections were observed amongst the erythrocytes. Their morphology allowed them to be identified as thrombocytes (TCs). Each TC displayed 18-26 cytoplasmic projections, most of which were in close proximity to erythrocytes. At their apical end, each cytoplasmic projection presented an ellipsoidal vacuole (c. 0·6 µm × 0·3 µm) from which a secretory tubule, 0·3-0·4 µm long and c. 120 nm in total diameter, extended towards the periphery of the TC plasmalemma and fused with the cellular membrane. From this opening, contents of vacuoles were apparently released into the lumen of the capillaries. Other vacuoles with similar features, and containing an electron-lucent matrix, were observed in the cytoplasm of the TC. This is the first description of fish TC with these ultrastructural features and organization, which suggest that they perform a secretory function.