Organs Of Fish Research Articles

Dietary Aflatoxin B1 attenuates immune function of immune organs in grass carp (Ctenopharyngodon idella) by modulating NF-κB and the TOR signaling pathway.

Aflatoxin B1 (AFB1) is kind of a common mycotoxin in food and feedstuff. Aquafeeds are susceptible to contamination of AFB1. In teleost fish, the spleen and head kidney are key immune organ. Moreover, the fish skin is a critical mucosal barrier system. However, there was little study on the effects of dietary AFB1 on the immune response of these immune organs in fish. This study aimed to explore the impacts of oral AFB1 on the immune competence and its mechanisms in the skin, spleen, and head kidney of grass carp. Our work indicated that dietary AFB1 reduced antibacterial compounds and immunoglobulins contents, and decreased the transcription levels of antimicrobial peptides in grass carp immune organs. In addition, dietary AFB1 increased the transcription levels of pro-inflammatory cytokines and reduced the transcription levels of anti-inflammatory cytokines in the grass carp immune organs, which might be regulated by NF-κB and TOR signaling, respectively. Meanwhile, we evaluated the content of AFB1 in the grass carp diet should not exceed 29.48 μg/kg diet according to the levels of acid phosphatase and lysozyme. In summary, dietary AFB1 impaired immune response in grass carp skin, spleen, and head kidney.

Domestication of captive-bred masu salmon Oncorhynchus masou masou (Salmonidae) leads to a significant decrease in numbers of lateral line organs

Because captive-bred animals gradually adapt to artificial rearing environments due to evolving life history traits, such individuals sometimes show lessened performance in natural environments. The lateral line system, one of the principal sensory organs of fishes, varies according to habitat environments, sometimes differing even within the same species. A reduction in lateral line elements may also occur in successive generations of captive-bred fish. Such a reduction, involving neuromasts over the entire body, was examined for the first time in captive-bred masu salmon Oncorhynchus masou masou. The total number of neuromasts in captive-bred fish was ca. 10% lower than in wild-caught and F1 fishes, suggesting that the system in captive-bred fish had reduced in number due to domestication. Furthermore, differences in total neuromast numbers between captive-bred and wild fish were greater than between anadromous and fluvial populations of the species. The lower number of neuromasts could be one of the reasons behind the lower survival of captive-bred fish in natural environments.

Combining Multiple Biomarkers to Evaluate the Environmental Stress in Cyprinid Populations

The Vilariça River was restored in order to improve the fish habitat due to the construction of dams. However, due to the pressure that agriculture exerts on water resources, it is crucial to evaluate its consequences on fish health from a histological perspective. The gonad histopathological changes of two cyprinid species were assessed microscopically and evaluated with semi-quantitative analysis. Histopathological changes in the gonad, gill, and liver were used as biomarkers in the determination of the Integrated Biomarker Response (IBR), as well as to evaluate the histopathological scores between seasons. The observation of the gonad histopathological changes showed that interstitial fibrosis and macrophage aggregates were present exclusively in the Summer and more prevalent in males of large size. In addition, the histopathological scores of the three organs were higher in the Summer. In terms of the severity degree, 98% and 68% of the fish showed pronounced and severe histopathological changes in the gill and liver, respectively, while 28% of the fish showed slight histopathological changes in the gonad. The IBR showed higher values in the Summer and in the middle stream and downstream, which is in agreement with the metal concentrations. Thus, this work showed a relationship between the anomalies present in the fish organs and the quality of the water (classified as polluted). Therefore, minimization measures are presented, such as improving the irrigation methods, preserving the vegetation cover; promoting reforestation in degraded and burned areas; and improving the riparian vegetation.

Effects of Temperature and Different Feed Uptake on Mercury (Hg) and Cadmium (Cd) Accumulation in Nile Tilapia

Climate warming due to increases in atmospherictemperature and heavy metal contamination constitutesa major issue for the aquatic ecosystem. Heavy metal toxicity hinges on an organism’s tolerable limit ofexposure to these elements, and in the aquatic environment, higher temperatures enhances this toxicity infish. The purpose of this study was to investigate the combined effects of higher temperature and differentfeed uptake on Hg and Cd accumulation in Nile tilapia (Oreochromis niloticus). Fish were exposed to asingle concentration of 10 μg/l mercury (Hg) or 100 μg/l cadmium (Cd) for 30 days under 24 °C (roomtemperature) and 32 °C (elevated temperature) conditions in a 7-L aquaria. The feed used in this experimentcomprised pellets, water and pellets, and water and silkworms, in combination with temperature andheavy metal exposure. Results demonstrated Hg and Cd accumulation in flesh, kidney and liver increasedwith increasing temperature. The influence of different uptake mediahas an effect onHg and Cdconcentration levels in fish organs. The order of Hg and Cd accumulation in organs, from the highest levelto the lowest, was kidney, liver and flesh.

Association of size structure, diet composition, endo-parasites of Snakehead fish (Channa striata, Bloch), in Lake Mainit, Caraga Region, Philippines

Channa striata Bloch is a type of indigenous freshwater fish abundant in Lake Mainit and it serves as a source of foods and finances of the people. This species was reported as an intermediate host of many helminth parasites. This research aimed to determine the association of endo-parasites, diet composition, and length and weight in snakehead fish C. striata Bloch in three selected municipalities along Lake Mainit, Caraga Region, Philippines. The results revealed that food items found in the stomach of the fish were mostly composed of shrimps, plant debris, fish, crab, detritus (dry & wet seasons), aquatic insects and snail (wet season). Among the seven food items, highest index of relative importance (IRI) value observed are shrimps in both wet and dry seasons. A nematode parasite was recovered in the gut of the fish samples. Out of 180 fish samples, 133 were infected with Procamallanus sp. The prevalence was higher in the dry season compared to the wet season. However, parasite intensity and diet count of C. striata Bloch. showed no significant variations between sampling sites and seasons. On the other hand, there were no significant differences between the intensity of the parasite count to the length and weight of the fish; the association between parasite count and diet count during dry and wet seasons showed a strong positive correlation. The results indicated that C. striata Bloch is susceptible to Procamallanus sp. nematode infection because of its carnivorous diet and serves as the vector or intermediate host in freshwater. Thus, more fish samples, the host’s age, host’s sex, the study gap, infection rate of the fish organs, and assessment of the physico-chemical parameters in future studies must be used.

Toxic and bioaccumulative effects of zinc nanoparticle exposure to goldfish, Carassius auratus (Linnaeus, 1758)

The widespread use of produced metal oxide nanoparticles (NPs) has increased major concerns about their impact on human as well as aquatic animal health. The present study shows that exposure to different concentrations of zinc oxide (ZnO) NPs led to high accumulations of Zn ions in the metabolic organs of fish (liver and gills), resulting in severe oxidative stress in Carassius auratus. The goldfish (C. auratus) was chosen as an aquatic species for the evaluation of the potential toxicity of aqueous ZnO-NPs (Treatments of hemoglobin and neutrophils (0, 0.5, 1, and 1.5 mg L− 1) following 14 days of exposure. A range of histological and hematological factors were examined. Exposure to the NPs produced significant reduction of red blood cell and white blood cell counts, hematocrit) were found to produce no significant differences in lymphocyte, monocyte, and eosinophil counts; as well as the mean corpuscular hemoglobin concentrations index (P > 0.05). Moreover, the results revealed significant alterations in serum biochemical parameters, hepatic enzyme levels, and immune and antioxidant responses; except for total protein and superoxide dismutase (SOD) of C. auratus exposed to ZnO-NPs, particularly at the 1 and 1.5 mg L− 1 concentrations. Fish exposed to 1 and 1.5 mg L−1 ZnO-NPs displayed a significant reduction in alternative complement pathway activity, lysozyme, and total protein contents of mucus compared to those in the control group. The results showed that hepatic SOD and catalase, and gill catalase activity were significantly decreased, and their malondialdehyde levels increased at 1 and 1.5 mg L−1 ZnO-NPs compared to the control group (P < 0.05). Significant accumulations of ZnO-NPs were observed in the liver, kidney, and gill tissues of fish leading to severe histopathological alterations in these organs. These results suggest that water-borne ZnO-NPs can easily accumulate in metabolic organs and lead to oxidative stress and destructive effects on the physiological features of C. auratus.

Streptococcosis a Re-Emerging Disease in Aquaculture: Significance and Phytotherapy.

Simple SummaryStreptococcosis is an economical important bacterial disease that can seriously cause huge losses in the global aquaculture sector. In recent years studies have focused on to use extracts or essences of medicinal herbs and plants to control or treat the disease outbreaks and, in most cases the results were promising. The essential oils of the herbs or plants are more effective than the extracts and, the extracts examined have moderate efficacy in term of increasing fish survival against fish streptococcosis that could be due to the enhancement of fish immunity by the herb bio-compounds. The lack of dosage optimization, toxicity and bioavailability assays of a specific herb/plant or its bioactive compound in fish organs make it difficult to judge the validation of clinical efficacy of a particular herb/plant against fish streptococcosis, and thus, required further investigations. Streptococcosis, particularly that caused by S. iniae and S. agalactiae, is a major re-emerging bacterial disease seriously affecting the global sustainability of aquaculture development. Despite a wide spread of the disease in aquaculture, few studies have been directed at assessing the in vitro antagonistic activity and in vivo efficacy of medicinal herbs and other plants against streptococcal agents. Most in vitro studies of plant extractives against S. iniae and S. agalactiae have found antibacterial activity, but essential oils, especially those containing eugenol, carvacrol or thymol, are more effective. Although essential oils have shown better anti-streptococcal activity in in vitro assays, in vivo bioassays require more attention. The extracts examined under in vivo conditions show moderate efficacy, increasing the survival rate of infected fish, probably through the enhancement of immunity before challenge bioassays. The available data, however, lack dosage optimization, toxicity and bioavailability assays of a specific plant or its bioactive compound in fish organs; hence, it is difficult to judge the validation of clinical efficacy for the prevention or treatment of fish streptococcosis. Despite the known bioactive compounds of many tested plants, few data are available on their mode of action towards streptococcal agents. This review addresses the efficacy of medicinal plants to fish streptococcosis and discusses the current gaps.

Modern ecological and hygienic problems of fish products safety, associated with the development of pond fish farming in the Saratov region

Materials about the study of the content of heavy metals and organochlorine pesticides in carp fishes of the agricultural sector, which is successfully developed in the Saratov region — pound fish farming, are presents in this article. It was found that the territorial location of pond production influence on the content of heavy metals and pesticides in fish. The content of the metals lead, cadmium and mercury in the liver and gonads of carp was higher than the permissible values when growing fish in ponds located in the city near highways. On the contrary, pesticides were detected in fish organs only in the territories of pond fish farming of agricultural farms. At the same time, the residual concentrations of organochlorine pesticides contained in freshwater fish did not exceed the maximum permissible levels. In order to safely consume fish grown near highways of the city limits, which are sources of heavy metal emissions, it should be recommended to remove internal organs (liver and gonads) from fish products.

Efficiency of thyme (Origanum onites) and coriander (Coriandrum sativum) essential oils on anesthesia and histopathology of rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate the anesthetic efficiency of coriander (Coriandrum sativum) and thyme (Origanum onites) essential oils at different concentrations (20, 50, 70, 100, 150, 200, 300, 400, 500, 600 mg L−1) on rainbow trout (Oncorhynchus mykiss). Additionally, the histopathological effects of essential oils were investigated on the fish tissues including gill, liver and kidney. At the end of the experiment, coriander essential oil was observed to be sedative at 50 mg L−1 and had an anesthetic effect at a concentration of 200 mg L−1 in rainbow trout. However, thyme essential oil caused mortality at the tested concentrations in rainbow trout. Histopathological examination, hyperemia, edema and desquamation were observed in the thyme group’ gills. Also, liver and kidney hyperemia was noticed in this group. No pathological findings were observed in any organ of fishes in the coriander group. The present study demonstrated that concentrations of 200 mg L−1 coriander essential oil can be used as an anesthetic for rainbow trout.

Bio-accumulation and health risk assessment of heavy metals in different edible fish species from Hurghada City, Red Sea, Egypt

BackgroundHeavy metal contamination has become a serious issue in this century especially detected in fish organs. Due to the presence of radioactive compounds in agricultural and sewage effluent, which destroys aquatic ecosystems, threatening human livelihoods. Health hazards associated with low and high consumption consumers assessed in five commercial fish species collected from Hurghada City, Egypt, during winter and summer, 2020. Atomic absorption spectrophotometer technique used for determination heavy meals in different organs and expressed as μg/g wet weight. ResultsHeavy metal concentrations in muscle ranged between:(0.054–0.109), (0.260–1.043), (0.264–0.897), (5.895–11.898), (0.381–0.970), (13.582–29.133) and (0.332–0.589) µg/g for Cd, Pb, Mn, Zn, Cu, Fe and Ni respectively, which were lower than those of gills and liver. These concentrations were within WHO, FAO/WHO, and EU standards. Consumption of edible species was lower than the (TDIs) established by the (JECFA) and Egyptian Standards. Even though THQ and TTHQ values were < 1 while, in children with highly consumer were> 1. ConclusionThis study concluded that intake of Red Sea fish is safe for human health. It is critical for consumers to be aware of the consequences of excessive fish consumption, particularly children with highly consumer, which represent possible health risks.

Concentrations of organotin compounds in aquatic biota in coastal waters of Johor, Malaysia

AbstractThe concentrations of organotin (OT) compounds, butyltin (BT) and phenyltin (PT), in aquatic organisms from Merambong and Tinggi Island, Malaysia, which differ in industrial and economic activities, were measured. Tributyltin (TBT) compounds among BTs ranged from 2.9–28 and &lt;0.1–21 ng g−1 ww in aquatic organisms from Merambong and Tinggi Island, respectively. Triphenyltin (TPT) compounds among PTs ranged from &lt;0.1–25 ng g−1 ww and &lt;0.1–61 ng g−1 ww in aquatic organisms from Merambong and Tinggi Island, respectively. A survey of OT concentrations among the species of OT compounds revealed that the concentrations of BTs and PTs in crabs and clams were high while those in fish were low. Correlation analysis with stable nitrogen isotopes suggest that OT compounds did not accumulate in aquatic organisms through the food web. The measurement of OT compounds in tissues and organs of fish revealed that BT concentrations in liver were higher than those in muscle and that BTs were detected in eggs of fish.

PARAQUAT-INDUCED HISTOPATHOLOGICAL CHANGES ON THE GILLS, KIDNEY AND LIVER TISSUES OF ANABAS TESTUDINEUS (BLOCH 1792)

Paraquat is the most widely used herbicide in agricultural activities for land preparation and weed control. Uncontrolled usage and poor waste management will introduce the chemical into the aquatic ecosystem due to agricultural runoff, causing harm to non-targeted aquatic species, especially fish. Therefore, this study was performed to evaluate the histological alterations of the gill, liver and kidney of the freshwater fish Anabas testudineus. Fish were exposed to four paraquat concentrations (2.0, 5.0, 12.0 and 15.0 mg/L) for 96 hours in controlled water parameters and without feeding. Following treatment, all fish were pithed and their gills, livers and kidneys were collected. Histopathological analysis with semi-quantitative scoring lesions were performed to determine the severity of the tissue changes in each fish organ. Histopathological changes in the gills after 96 hours of paraquat exposure showed lamella curvature, hyperplasia, edema, blood vessel congestion and necrosis compared with the control group. Histological changes, like degeneration in hepatocytes and necrosis were observed in the livers and kidneys exposed to 2.0-12.0 mg/L of paraquat. Prominent histopathological changes were observed in 15.0 mg/L of paraquat exposure, including nuclear pyknosis and necrosis. Overall, this study demonstrated deleterious effects of paraquat on the tissues of A. testudineus. The histopathological changes were proportional to the paraquat concentration and may impair organs’ vital functions which in turn affects the fish’s health.

Characterization and implication of microplastics on riverine population of the River Ravi, Lahore, Pakistan.

Microplastic (MP) pollution in the aquatic environment is an emerging subject worldwide. So far, very few investigations have been reported on the riverine fish population. This study investigated the implications of microplastics for three freshwater fish species (Labeo rohita, Cirrihinus mrigala, and Sperata seenghala) as bioindicators of this pollution. Raman spectroscopy was used to confirm MP polymer type and their distribution in water, sediments, and in different organs (gut, gills, liver, and muscles) of Labeo rohita, Cirrihinus mrigala, and Sperata seenghala collected from River Ravi at two sites (site I, Dhand Nano Dogar and site II, Jhamra). These selected sites were situated predominantly near agricultural lands and received polluted water from nearby sewerage and industries that represented potential sources of microplastic pollution. Histological analysis was combined with Raman spectroscopy to assess the effects of MPs on fish organs. MPs were identified in water and sediment samples with an average load (per 0.5 L or per 0.5kg) of 33 items and 64 items for water and sediments at site I and 27 items and 19 items at site II, respectively. Of total MPs identified, 56.9% were found in bottom feeder C. mrigala, 37.91% in column feeder L. rohita, and 5.21% in S. seenghala at site I while at site II 60% were found in C. mrigala, 29% in L. rohita and 10.34% in S. seenghala. This was linked with more plastic accumulation in sediments from the nearby residential sewerage and industrial effluent flow. In this study, the identified MPs polymers were in the order of polyvinyl chloride (PVC) > polystyrene (PS) > propylene (PP) > polyethylene (PE). Among plastic shapes, fiber (58%) was the dominant plastic in water followed by fragment (21%), sheet (12%), and cube (9%). In sediment, the fragment was the common plastic shape with 51% followed by fiber (28%), sheet (19%), and cube (2%). Fragments (62.9%) in water and fibers (68.4%) in sediments were abundant at site 2. Microplastic mean occurrence in organs was in the order of gut > gills > muscles > liver at both sites. Significant histological alterations were observed in all three species including intestinal edema, hyperplasia, hepatocyte infiltration, accumulation of lipid droplets in the liver, lamellar fusion and breakage in gills, and muscle fiber necrosis. This study showed MP occurrence in the selected freshwater fishes, so further research is needed to assess plastic pollution in the riverine fish population of Pakistan. This study appeared to be the first in the selected area, as no significant information regarding plastic pollution in that riverine system was found when this study was conducted.

Single cell transcriptomics of Atlantic salmon (Salmo salar L.) liver reveals cellular heterogeneity and immunological responses to challenge by Aeromonas salmonicida.

The liver is a multitasking organ with essential functions for vertebrate health spanning metabolism and immunity. In contrast to mammals, our understanding of liver cellular heterogeneity and its role in regulating immunological status remains poorly defined in fishes. Addressing this knowledge gap, we generated a transcriptomic atlas of 47,432 nuclei isolated from the liver of Atlantic salmon (Salmo salar L.) contrasting control fish with those challenged with a pathogenic strain of Aeromonas salmonicida, a problematic bacterial pathogen in global aquaculture. We identified the major liver cell types and their sub-populations, revealing poor conservation of many hepatic cell marker genes utilized in mammals, while identifying novel heterogeneity within the hepatocyte, lymphoid, and myeloid lineages. This included polyploid hepatocytes, multiple T cell populations including γδ T cells, and candidate populations of monocytes/macrophages and dendritic cells. A dominant hepatocyte population radically remodeled its transcriptome following infection to activate the acute phase response and other defense functions, while repressing routine functions such as metabolism. These defense-specialized hepatocytes showed strong activation of genes controlling protein synthesis and secretion, presumably to support the release of acute phase proteins into circulation. The infection response further involved up-regulation of numerous genes in an immune-cell specific manner, reflecting functions in pathogen recognition and killing, antigen presentation, phagocytosis, regulation of inflammation, B cell differentiation and T cell activation. Overall, this study greatly enhances our understanding of the multifaceted role played by liver immune and non-immune cells in host defense and metabolic remodeling following infection and provides many novel cell-specific marker genes to empower future studies of this organ in fishes.

Assessment of the exposure of two pesticides on common carp (Cyprinus carpio Linnaeus, 1758): Are the prolonged biomarker responses adaptive or destructive?

Chlorpyrifos (CPF) and cypermethrin (CYP) are two insecticides that have a proven negative effect on non-target aquatic organisms when they enter the surface waters. However, literature on the comparative effects of these pesticides on important aquaculture fish species, such as common carp (Cyprinus carpio Linnaeus, 1758) is not yet scientifically detailed, especially over the long-term. The idea of conducting a long-term exposure is to find out how the observed biomarkers would change compared to the short-term exposure. In the natural environment, toxicants are not present alone, but in combination. By monitoring the long-term impact of individual substances, the state of aquatic ecosystems exposed to various toxicants could be predicted. Thus, this study aimed to evaluate the toxicity of different concentrations of CYP (0.0002, 0.0003, and 0.0006 μg/L) and CPF (0.03, 0.05, and 0.10 μg/L) in 50-L glass tanks on C. carpio, exposed for 30 days under laboratory conditions. A set of histological and biochemical biomarkers in the gills and liver were applied with the chemical analyses of water and fish organs. Furthermore, the condition and hepatosomatic index were calculated to assess the physiological status of the treated carps. The behavioral responses were also monitored, and the respiration rate was analyzed. The results suggest that CYP had a more prominent effect on the histological structure of fish organs, biochemical responses of anti-oxidant enzymes, behavior, and respiration rate compared to the effect of CPF. In addition, the results also indicate that the liver is more susceptible to chronic and chemically induced cellular stress compared to the gills, with overall destructive changes in the histological biomarkers rather than adaptive. Regardless of the scenario, our results provide novel insights into pesticide exposure and the possible biological impacts on economically important freshwater fish, exposed to lower CYP and CPF concentrations, based on the EU legislation (maximum allowable concentrations, MAC-EQS).

Short-term Co-exposure of celery leaf powder exerts detoxifying action against acetaminophen-induced toxicity in fish gills

Acetaminophen (APAP) is one of the widely used health care products. After consumption, excess APAP is excreted along with its toxic metabolites as human waste into sewage and other aquatic systems. These serve as aquatic pollutants and affect aquatic organisms. Plants can remove, reduce and transform the acetaminophen from the contaminated water. Thus, the present study is aimed at exploring whether APAP + celery leaf powder (CE) exposure would protect the fish gills from the toxicity of APAP. The freshwater fish (Pangasius sutchi) were divided as Group 1 control (untreated), Group 2 APAP treated (500 mg/kg/24 h), Group 3 APAP + CE (500 mg/kg/24 h) co-exposed and Group 4 CE treated control. The gills of APAP-exposed fishes displayed the elevated levels of aquatic pollutions markers [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP)], increased oxidative stress markers, the altered enzymic and non-enzymic antioxidants activities, and abnormal histology. Whereas, these changes were minimized in the gills of APAP+CE exposed fish. The findings of the study suggest that the antioxidant effect of CE and a possible interacting ability of CE phytochemicals with APAP could protect the osmoregulatory organs of fish from the APAP polluted water.

Histo-pathology of the Vibrio alginolyticus bacteria on tiger grouper (Epinephelus fuscoguttatus Forskal)

The purpose of this study was to determine histo-pathology of bacterium V. alginolyticus against several tiger grouper fish organs. The pathogenicity test was carried out by injecting intramuscularly (IM) 0.1 ml of V. alginolyticus bacterial suspension with bacterial density of 107, 108, 109 cells/ml/fish and injected with 0.1 ml of PBS solution (phospate buffer solution) as a control. Results showed that bacterium V. alginolyticus causes degeneration, damage and structural changes in the tissues of gill organs, kidneys, liver, and brain of tiger grouper fish. Pathogenicity challenge tests also prove that this bacterium is a true pathogen for test animals. The degree of density of the suspension of pathogenic cells affects mortality and incubation period. The bacterial density of 107 cells/ml/fish has caused death of 33.33%, density of 108 cells/ml/fish causes’ death of 66.67%, and density of 109 cells/ml/fish causes death of 73.33%, while without bacteria (control) there is no death.

Heavy Metals Accumulation in Tissues of Wild and Farmed Barramundi from the Northern Bay of Bengal Coast, and Its Estimated Human Health Risks.

Globally, both natural water bodies and aquaculture systems are being severely contaminated by heavy metals due to rising anthropogenic activities. Fish living in aquatic environments can easily accumulate metals in their bodies, which can then be transferred to consumers and put them at risk. In this study, metal concentrations (Pb, Cd, Cr, As, Mn, Cu, Zn) in different organs (gill, liver, and muscle) of farmed and wild Barramundi (Lates calcarifer) fish from the northern Bay of Bengal were evaluated to quantify and compare contamination levels and related human health risk. Heavy metal concentrations were higher in liver tissues of farmed Barramundi than in wild Barramundi, with the following relative mean values in the liver, gills, and muscle: Zn > Cu > Pb > Mn > Cd > Cr > As; Zn > Cr > Cu > Pb > Mn > Cd > As; Zn > Pb > Cu > Cr > Mn > Cd > As; Zn > Pb > Cu > Cr > Mn > Cd > As; and Zn > Pb > Cu > Cr > Mn > Cd > As, respectively. The differences in heavy metal accumulation observed between farmed and wild fish were probably related to the differences in their environmental conditions and dietary element concentrations. However, ANOVA indicated that the variation of metals in wild and Barramundi was not statically significant. Pb concentrations in the liver tissue of farmed Barramundi exceeded the national and international threshold limits, whereas concentrations of other metals were within the limit. Among the examined organs in both fish species (wild and farmed), muscle had the lowest concentration compared to others, and liver was the target organ for Pb, Cu, and Cd accumulations. Metals such as Zn and Mn exhibited higher concentration in the gills. However, all the studied heavy metals were below the maximum permissible limits of national and international standards, but the mean concentrations of Pb and Cd values in the liver of farmed Barramundi exceeded all international and national guidelines. Based on the contamination factors (CF) and pollution indices (PLI and MPI), the degree of contamination in the fish organs was as follows: gills > liver > muscle. The major accumulation tissues for both farmed and wild fish were found to be the gills (MPI = 0.970) and the liver (MPI = 0.692). Based on the estimated daily intake (EDI), the fish samples examined in this study are safe for human consumption as within the recommended daily allowance (RDA) range established by various authorities. According to the Target Hazard Quotient (THQ) and Carcinogenic Risk (CR) calculations, though the Barramundi fishes depicted no potential hazard to humans, farmed fish posed a higher health risk than wild fish.

Immunopotentiation mechanism of a mannose-modified peptide fragment containing a dominant antigenic epitope of Micropterus salmoides rhabdovirus (MSRV) glycoprotein after coupling to nanocarrier

Micropterus salmoides rhabavirus (MSRV) is an important pathogen that threatens the aquaculture of bass farming worldwide, and the efficacy of vaccines developed against this pathogen still needs to be improved. In order to further enhance the immune efficacy of existing vaccines, a mannose-modified nanovector vaccine SWCNTs-M-G2 was constructed by screening for peptide fragments encoding highly immunogenic antigenic epitopes (G2) and mannose modifications. Mannose receptor (MR) is abundantly expressed on the surface of Antigen-presenting cells (APCs) and plays a role in recognizing pathogens and presenting antigens. In this study, the effect of mannosylated modification on the immunopotentiation of highly immunogenic peptide fragments was investigated by using the characteristics of MR-specific recognition of mannose and APCs surface. In vitro macrophage assays showed that SWCNTs-M-G2 was efficiently phagocytosed and taken up by largemouth black bass head kidney macrophages, and effectively stimulated macrophage activation and upregulated the secretion of macrophage cytokines IL-1β, IL-8 and IL-12. In vivo, SWCNTs-M-G2 was also shown to be better taken up by immune organs such as spleen and head kidney, and induced increased expression of IL-1β, IL-8 and IL-12 in the immune organs of Micropterus salmoides, and promoted the expression of TCR and CD4 molecules in specific immune cells. Meanwhile, in vivo fluorescence imaging revealed that SWCNTs-M-G2 could be in the immune organ of fish for a longer period of time, contributing to the efficient uptake of antigens. Finally, the challenge test showed that SWCNTs-M-G2 could mediate the production of specific antibodies at a higher level than the unmodified carrier vaccine SWCNTs-G2 and showed a higher relative immune protection rate.

Microplastic load in the surface water and Tilapia sparrmanii (Smith, 1840) of the river systems of Okavango Delta, Botswana.

Microplastics are 'emerging' contaminants that threatens freshwaters and may have negative impact on the aquatic organisms. However, Botswana has no information on the status of microplastics, including freshwater like the Okavango Delta- the largest, inland wetland hosting wildlife, tourism, and supporting the socio-economic lifestyle of inhabitants. This study assessed the spatial distribution and characterization of microplastics in surface water and in the digestive organs of fish (Tilapia sparrmanii) from the Okavango delta. Surface water samples (156) and whole intact fish (15) were collected and analysed for microplastic contents by wet peroxide oxidation, potassium hydroxide (fish only), density separation, extraction, and stereomicroscope identification. The weight of microplastics for surface water samples varied from 138.18 to 381.67µgm-3 and abundance ranged from 10.18 to 22.67 items L-1 with significant difference observed between sites in both variables. In tilapia, the highest microplastic abundance were found in the intestines then the stomach and the gills from the fish samples. Most prevailing size ranges of microplastics in fish and water samples were 1-2mm and 2-3mm while the most abundant shapes were fragments and fibres, respectively. Translucent microplastics were dominant in all samples. The results indicate the presence of microplastics in the Okavango delta even though they are very low (µg m-3). This baseline information will provide insights on the loads of microplastics in surface water and the quantities ingested by fish in the Okavango delta hence the need for monitoring. It would also guide on the need for effective policies addressing plastic and microplastic pollution.