Untreated Fish Research Articles

Gut microbiota perturbation and subsequent oxidative stress in gut and kidney tissues of zebrafish after individual and combined exposure to inorganic arsenic and fluoride.

Chronic exposure to inorganic arsenic (iAs) and fluoride (F) affect gut health and potentially damage organs. The present study investigates the interplay between gut bacteria and oxidative stress (measured by MDA level, GSH level, catalase activity, Nrf2 translocation and expression) in zebrafish exposed to F (NaF 15 ppm) and As (As2O3 50 ppb) alone or in combination. Combined exposure to As and F reduced gut bacterial alteration and imposed less oxidative stress compared to F- exposure alone. V3-V4 metagenomic sequencing revealed Pseudomonas, Aeromonas and Plesiomonas genera dominated in As or F treated groups while As+F treated group was enriched in beneficial Lactococcus and Streptococcus genera. Functional KEGG analysis demonstrated treatment-specific changes in bacterial metabolism, host organismal systems, human diseases, as well as cellular processes of microbial community were significantly affected. When Aeromonas sp. isolated from F-treated fish gut, tagged with GFP-vector and fed (~3.2 × 106 CFU/ml) to untreated fish, induced oxidative stress in gut and kidney. Gut bacteria were found to both increase and mitigate iAs or F-toxicity, whereas As+F treatment promoted a protective response. Correlation analysis between gut microbial community at genus level and oxidative stress parameters of gut and kidney, showed Aeromonas and Plesiomonas genera are strongly correlated with oxidative stress (r = 0.5-0.9, p˂0.05). This study identifies microbiome biomarkers of iAs and F toxicity on gut-kidney axis.

Economic-ecological assessment of multi-crop small-scale model farms in the Republic of Armenia (piloting results from Gegharqunik region)

Background: Biogenic elements such as nitrogen (N), phosphorus (P), and potassium (K) are major pollutants of Lake Sevan's water, causing eutrophication and deterioration of water quality. Untreated wastewater, sewage, agriculture, fish farming, and other activities are significant sources of these pollutants. Vegetable cultivation, heavily reliant on mineral fertilizers and chemicals, and livestock breeding contribute substantially to nitrogen pollution in the lake. However, improved vegetable growing practices, including small-scale agriculture using organic fertilizers, natural soil improvers, and eco-friendly bio-liquids as growth stimulants, can enhance the socio-economic conditions for farmers in the Lake Sevan basin. These practices promote environmentally friendly, water-saving land-use methods, reducing nitrogen leaching into the lake. Objective: This study aims to demonstrate the socio-economic and environmental benefits of applying innovative agro-technology to small-scale farming in the Lake Sevan watershed (Gegharkunik region). Specifically, the study objectives are to determine the quality characteristics of crops grown in small-scale farms and compare these quality indicators between yields obtained through the proposed technology and traditional cultivation methods. Methods: Field trials of multi-crop systems were conducted on 0.25 ha land plots in four variations across four different locations in the Lake Sevan watershed. The trials were evaluated for various parameters. Nitrate content, dry matter, starch, vitamin C, and sugar levels were determined in potatoes, cabbage, broccoli, beets, and green beans, while fat content was measured in green beans and green peas. Results: Economic efficiency calculations revealed that utilizing the proposed innovative agro-technology in a multi-crop small-scale farm (0.25 ha) yielded a 20-25% increase compared to traditional cultivation with synthetic fertilizers, accompanied by notable environmental benefits. Conclusions: The study demonstrates that small-scale agricultural practices employing the proposed agro-technology have significant socioeconomic and environmental impacts on local farmers. Keywords: Cultivation of non-traditional crops, organic farming, small-scale farming, activities, economic and ecological evaluation, and food quality characteristics.

Decontamination of fish aquarium wastewater by ozonation catalyzed by multi-metal loaded activated carbons for sustainable aquaculture

This study aims to promote sustainable aquaculture for fish farming practices for long-term application. The potential of catalytic ozonation was evaluated for the successful purification and recycling of fish aquarium wastewater. Before continuous testing, ozone dosage, catalyst dose, reaction time, and adsorbent dose were optimized to obtain values of 1.8 mg/min, 15 g/L, 45 min, and 150 g, respectively. During this work, two different goldfish aquarium setups were installed at the lab scale to compare the treated aquarium water (tank A) with the untreated water (tank B). Tank A was a kind of continuous tank, where the water in the aquarium was continuously treated by the catalytic ozonation process. For the first time, activated carbon (AC) loaded with iron (Fe) and zinc (Zn) (Fe-Zn-AC) was used as the catalyst for fish water purification. Around 170 L of water was conserved through water purification in comparison with a normal fish aquarium setup (tank B). The results indicated successful decontamination by the decline in parameters such as ammonia, COD, BOD5, turbidity, and potentially toxic metals as compared to untreated fish aquarium wastewater. Additionally, catalytic ozonation (Fe-Zn-AC/O3), was more efficient for the removal of nitrogenous compounds. It is concluded that catalytic ozonation provides more efficient removal of contaminants to facilitate the establishment of a sustainably disease-free environment and better growth of fish inside a recirculating setup.

Basal Expression Profile of Seven Glutathione-S-Transferases (GSTs) Genes in Six Tissues of Tilapia (Oreochromis niloticus) for Polymerase Chain Reaction Array

Study’s Excerpt The differential expression patterns of Glutathione-S-transferase (GST) isoforms in six tissues of Nile tilapia are investigated. Seven specific GST genes are examined across six tissues, and it is determined that the liver, spleen, and intestines are key sites of significant gene expression. GST isoforms could be potentially used as biomarkers for assessing xenobiotic stress in aquatic environments. Full Abstract Because aquatic habitats are being destroyed and biodiversity is declining, xenobiotic pollution of water is a critical environmental problem that has garnered a lot of attention in the past few decades. This study looked at the expression patterns of Glutathione-S-transferases isoforms (GSTMA, GSTO1LA, GSTA, GSTR1, GSTK, GSTT1, and MGST), which are genes involved in xenobiotic metabolism, in Nile tilapia. From adult Nile tilapia, six tissues—liver, spleen, intestines, gills, heart, and muscle—were chosen, and seven genes that were optimised via quantitative polymerase chain reaction (qPCR) were used for validation. Gene expressions were assessed using a PCR array that included duplicate tissues in 96-well qPCR plates, with each gene/plate being assayed six times. Water is used in the remaining wells as no template control (NTC). As reference genes, Pan Ribosomal Protein L3 (RPL3) and Pan 18S ribosomal RNA (18S RNA) were employed. The genes’ basal tissue mRNA expression was measured in each tissue. The muscle was utilised to renormalise the expression levels of all genes throughout the remaining tissues since, under assay’s circumstances the muscle showed very low signal for most of the genes. Using quantitative real-time PCR (qPCR), the result demonstrated widespread differential expression patterns of the seven GST mRNA in the liver, spleen, intestine, gills, heart, and muscle of an untreated fish. However, it was clear that the highest significant expression level of most genes (different GST’s isoforms) was in the liver, followed by the spleen and gut, then the heart and gills compared to muscle (P<0.05). The findings demonstrated widespread differential expression of the GST’s isoforms at basal level and highlighted their utility as biomarkers for xenobiotic stress in aquatic environments.

In silico, In vitro, and In vivo Evaluation of the Anti-alzheimer’s Activity of Berberine

Background: Alzheimer’s disease (AD), a progressive neurodegenerative disease for which there is no effective cure is among the leading causes of death worldwide. Objectives: To investigate the potential anti-AD activity of berberine (BBR). Methods: In silico assessment included molecular docking and ADMET prediction. BBR’s in vitro inhibitory activity of the target selected from docking results was assessed via colorimetric inhibitor screening assay. BBR’s LC50 in adult zebrafish was determined via an Acute Toxicity Study. ZnCl2 concentration for AD induction was determined via toxicity study and T-maze test. Finally, zebrafish were treated with ZnCl2 alone or simultaneously with either BBR or donepezil and assessed via the inhibitory avoidance task, followed by ELISA of AD-related biomarker levels in brain tissue. Results: The in silico assessment showed BBR’s desirable drug properties and binding affinity on selected AD-related targets, which was the greatest docking score with AChE. The in vitro IC50 on AChE was 3.45 μM. The LC50 in adult zebrafish was calculated at 366 ppm. In the T-maze test, ZnCl2 at 2.5 ppm caused the greatest cognitive impairment accompanied by moderate freezing. In the inhibitory avoidance test, fish treated with either 100 ppm BBR or 2.5 ppm donepezil had significantly better performance than ZnCl2-treated fish. ZnCl2-treated zebrafish brain tissue had the highest Aβ levels and AChE activity of all groups, but these were significantly lower in donepeziland BBR-treated fish. ZnCl2- and donepezil-treated fish had similar TNF-α levels, whereas BBR treatment significantly lowered them close to those of untreated fish. Conclusion: BBR showed anti-amyloidogenic, anti-AChE, and anti-inflammatory effects, which support its potential use in AD therapy.

Toward new biomarkers of cold tolerance: microRNAs regulating cold adaptation in fish are differentially expressed in cold-tolerant and cold-sensitive Nile tilapia (Oreochromis niloticus)

Overcoming the negative effects of cold stress in Nile tilapia (Oreochromis niloticus) is of great interest for the overall aquaculture economy. Recent evidence suggests that microRNAs may regulate mechanisms of cold adaptation in fish and could be potential biomarkers of cold tolerance in these animals. However, information on how microRNAs regulating cold adaptation in fish are expressed in cold-tolerant and cold-sensitive fish is still scarce. Therefore, the aim of the present study is to investigate the relationship between a panel of previously identified differentially expressed microRNAs in fish exposed to low temperatures and their association with cold tolerance in Nile tilapia. To this end, fish were individualized based on their weight and length, and subjected to a critical thermal minimum (CTmin) test. Blood samples were collected before and after the CTmin test. After the CTmin, brain and liver tissues were collected. Fish were separated into cold-tolerant and cold-sensitive based on their CTmin results. Untreated fish were used as control. The relative expression of miR-9-3p, miR-135c, miR-9-5p, miR-30b, miR-122, miR-92a was assessed through qPCR. Additionally, qPCR was used to measure the mRNA relative expression of IGF-I and SCD in the tissues. Cortisol and biochemical parameters were determined in plasma samples. As a result, miR-92a was up-regulated in the liver of cold-sensitive fish and in the blood of cold-tolerant fish post-CTmin. miR-30b was up-regulated in the blood and liver of cold stressed fish. In the brain, miR-9-5p and miR-9-3p were up-regulated in cold-tolerant fish post-CTmin. Furthermore, miR-122 and miR-135c expression levels remained similar to the control post-CTmin. In addition, miR-122 and miR-92a were differentially expressed in the blood of cold-tolerant and cold-sensitive Nile tilapia pre-CTmin. Therefore, besides regulating fish cold acclimation responses differently in cold-tolerant and cold-sensitive fish, miRNAs may also regulate pre-existing physiological conditions that are determinant to cold tolerance in Nile tilapia. In the transcriptional level, SCD expression increased in both cold-tolerant and cold-sensitive fish post-CTmin. Cold-tolerant Nile tilapia post-CTmin had increased levels of plasma cholesterol and IGF-I mRNA in the liver, which could mean an adaptive advantage. The present findings provide new insights on the role of post-transcriptional regulation of cold tolerance in Nile tilapia. Furthermore, miRNAs differentially expressed in cold-tolerant Nile tilapia may be potential targets for the development of new biomarkers and aid in the breeding of cold-tolerant strains in this species.

Plants buffer some of the effects of a pair of cadmium-exposed zebrafish on the un-exposed majority

Certain individuals have a disproportionate effect on group responses. Characteristics may include susceptibility to pollutants, such as cadmium (Cd), a potent trace metal. Here, we show how a pair of Cd-exposed individuals can impact the behavior of unexposed groups. We used behavioral assessments to characterize the extent of the effects of the Cd-exposed individuals on group boldness, cohesion, foraging, activity, and responses to plants. We found that groups with a pair of Cd-exposed fish remained closer to novel stimuli and plants than did groups with untreated (control) fish. The presence of plants reduced Cd-induced differences in shoal cohesion and delays feeding in male shoals. Shoals with Cd- and water-treated fish were equally active. The results suggest that fish acutely exposed to environmentally relevant Cd concentrations can have profound effects on the un-exposed majority. However, the presence of plants may mitigate the effects of contaminants on some aspects of social behavior.

Effect of 17α-methyl testosterone on sex reversal and growth performance of Nile tilapia,Oreochromis niloticus

The present study aimed at developing all-male Nile tilapia using17α-methyl testosterone(17α-MT) along with its growth and feed utilization performances. Three days old Niletilapia fry were stocked in plastic jars with 5 L capacity installed in four fiber glass tanks. The fry were fed with 0, 30, 60, and 100 mg MT/kg diets for 30 days. Later, the fry were shifted to hapas installed in a pond and then, reared for four months separately. The fish were fed with the control diet. The results showed that the highest male population(93.6%) was observed in the fish treated with a 60 mg MT/kg diet, while the lowest(82.6%) was observed in the fish treated with a 30 mg MT/kg diet. The results also showed that the fish fed with a 60 mg MT/kg diet had significantly higher mean body weight (24.1±1.40 g), specific growth rate (2.5±0.10%), feed conversion ratio (1.3±0.10), and protein efficiency ratio (0.63±0.11) than the untreated fish treated (control) group. In conclusion, a 60 mg MT/kg diet can be considered as an optimal and economically viable dose for Nile tilapia sex reversal along with its optimum growth and feed utilization performances.

The Hexane Extract of Citrus sphaerocarpa Ameliorates Visceral Adiposity by Regulating the PI3K/AKT/FoxO1 and AMPK/ACC Signaling Pathways in High-Fat-Diet-Induced Obese Mice.

Obesity is an emerging global health issue with an increasing risk of disease linked to lifestyle choices. Previously, we reported that the hexane extract of Citrus sphaerocarpa (CSHE) suppressed lipid accumulation in differentiated 3T3-L1 adipocytes. In this study, we conducted in vivo experiments to assess whether CSHE suppressed obesity in zebrafish and mouse models. We administered 10 and 20 μg/mL CSHE to obese zebrafish juveniles. CSHE significantly inhibited visceral fat accumulation compared to untreated obese fish. Moreover, the oral administration (100 μg/g body weight/day) of CSHE to high-fat-diet-induced obese mice significantly reduced their body weight, visceral fat volume, and hepatic lipid accumulation. The expression analyses of key regulatory genes involved in lipid metabolism revealed that CSHE upregulated the mRNA expression of lipolysis-related genes in the mouse liver (Pparα and Acox1) and downregulated lipogenesis-related gene (Fasn) expression in epididymal white adipose tissue (eWAT). Fluorescence immunostaining demonstrated the CSHE-mediated enhanced phosphorylation of AKT, AMPK, ACC, and FoxO1, which are crucial factors regulating adipogenesis. CSHE-treated differentiated 3T3L1 adipocytes also exhibited an increased phosphorylation of ACC. Therefore, we propose that CSHE suppresses adipogenesis and enhances lipolysis by regulating the PI3K/AKT/FoxO1 and AMPK/ACC signaling pathways. These findings suggested that CSHE is a promising novel preventive and therapeutic agent for managing obesity.

Cost-effective production of ergothioneine using Rhodotorula mucilaginosa DL-X01 from molasses and fish bone meal enzymatic hydrolysate

Ergothioneine (EGT) is a high-value natural antioxidant that cannot be synthesized by the human body. This study showed that Rhodotorula mucilaginosa DL-X01 can use untreated molasses and fish bone meal enzymatic hydrolysate as the substrates to synthesize EGT. By optimizing the growth conditions, the EGT yield reached 29.39 mg/L when molasses and fish bone meal (FBM) were added at 60 g/L and 400 g/L respectively. Finally, the EGT yield was increased to 216.25 mg/L by fed-batch fermentation in a 5 L bioreactor. Compared with the fermentation by yeast extract peptone dextrose medium, the feedstock cost of EGT production was reduced by 330.91 % by using molasses and FBM as substrates. These results showed that R. mucilaginosa DL-X01 can produce high-value EGT using two cheap processing by-products, molasses and FBM, which is of great significance for environmental protection and sustainable development.

Consecutive treatments of methamphetamine promote the development of cardiac pathological symptoms in zebrafish.

Chronic methamphetamine use, a widespread drug epidemic, has been associated with cardiac morphological and electrical remodeling, leading to the development of numerous cardiovascular diseases. While methamphetamine has been documented to induce arrhythmia, most results originate from clinical trials from users who experienced different durations of methamphetamine abuse, providing no documentation on the use of methamphetamine in standardized settings. Additionally, the underlying molecular mechanism on how methamphetamine affects the cardiovascular system remains elusive. A relationship was sought between cardiotoxicity and arrhythmia with associated methamphetamine abuse in zebrafish to identify and to understand the adverse cardiac symptoms associated with methamphetamine. Zebrafish were first treated with methamphetamine 3 times a week over a 2-week duration. Immediately after treatment, zebrafish underwent electrocardiogram (ECG) measurement using an in-house developed acquisition system for electrophysiological analysis. Subsequent analyses of cAMP expression and Ca2+ regulation in zebrafish cardiomyocytes were conducted. cAMP is vital to development of myocardial fibrosis and arrhythmia, prominent symptoms in the development of cardiovascular diseases. Ca2+ dysregulation is also a factor in inducing arrhythmias. During the first week of treatment, zebrafish that were administered with methamphetamine displayed a decrease in heart rate, which persisted throughout the second week and remained significantly lower than the heart rate of untreated fish. Results also indicate an increased heart rate variability during the early stage of treatment followed by a decrease in the late stage for methamphetamine-treated fish over the duration of the experiment, suggesting a biphasic response to methamphetamine exposure. Methamphetamine-treated fish also exhibited reduced QTc intervals throughout the experiment. Results from the cAMP and Ca2+ assays demonstrate that cAMP was upregulated and Ca2+ was dysregulated in response to methamphetamine treatment. Collagenic assays indicated significant fibrotic response to methamphetamine treatment. These results provide potential insight into the role of methamphetamine in the development of fibrosis and arrhythmia due to downstream effectors of cAMP.

Assessment of textile industry effluent (untreated and microbially treated) induced genotoxic, haematological, biochemical, histopathological and ultrastructural alterations in fresh water fish Channa punctata.

The unregulated expulsion of untreated textile water into water bodies is a major hazard to aquatic ecosystems. The present investigation was contrived to estimate the impact of textile dye bath effluent (untreated and microbially treated) on fish Channa punctata. Untreated effluent-exposed fish showed extremely altered behaviour (air gulping, erratic and speedy movements, increased opercular activity) and morphology (deposition of dyes on skin and scales, high pigmentation, mucus exudation). Significantly increased micronuclei (1.61-, 1.28-, 1.38-fold) and aberrant cell frequency (1.37-, 1.45-, 1.28-fold) was observed in untreated group as compared to treated group after 15, 30, and 45 days of exposure. Tail length, % tail intensity, tail moment and olive tail moment were also enhanced in all the exposed tissues. However, maximum damage was noticed in gill tissues showing 1.19-, 1.37-, 1.34- and 1.50-fold increased TL, %TI, TM and OTM in untreated group as compared to treated group after 45 days of exposure. On comparing untreated and treated groups, increased blood parameters and significantly reduced white blood cell count (WBC) were noticed in treated group. Significantly enhanced alterations in biochemical parameters were also analysed in untreated group. Reduced alterations in enzymological levels of fishes exposed to treated effluent indicate lesser toxic nature of the degraded metabolites of dye. Histological analysis in fishes exposed to untreated effluent showed several deformities in liver (necrosis, congestion, fusion of cells and melanomacrophage infiltration) and gill tissues (necrosis, bending of lamellae and severe aneurysm). Scanning electron microscopy (SEM) analysis further reaffirmed the pathologies observed in histological analysis. Fewer structural alterations were noticed in treated effluent fishes. The results concluded that untreated effluent inflicted toxicity potential on morphology as well as physiological defects in fish, and the severity increased with increasing duration of exposure, whereas reduction in toxicity in microbially treated groups can be analysed for aquacultural purposes owing to their lesser toxic nature.

Role of Citrullus colocynthis and Psidium guajava Mediated Green Synthesized Silver Nanoparticles in Disease Resistance against Aeromonas hydrophila Challenge in Labeo rohita.

Green synthesis of metallic nanoparticles is an auspicious method of preparing nanoparticles using plant extracts that have lesser toxicity to animal cells and the host. In the present work, we analyzed the antibacterial activity of Citrullus colocynthis and Psidium guajava-mediated silver nanoparticles (Cc-AgNPs and Pg-AgNPs, respectively) against Aeromonas hydrophila (A. hydrophila) in an in vivo assay employing Labeo rohita (L. rohita). L. rohita were divided into six groups for both Cc-AgNPs and Pg-AgNPs treatments separately: Control, A. hydrophila infected, A. hydrophila + Ampicillin, A. hydrophila + Cc/Pg-AgNPs (25 µg/L), A. hydrophila + Cc/Pg-AgNPs (50 µg/L), and A. hydrophila + Cc/Pg-AgNPs (75 µg/L). Changes in different bio-indicators such as hematological, histological, oxidative stress, and cytokine analysis were observed. Interestingly, the infected fish treated with both types of AgNPs (Cc-AgNPs and Pg-AgNPs) exhibited a higher survival rate than the untreated infected fish and demonstrated signs of recovery from the infection, providing a compelling indication of the positive impact of phytosynthesized AgNPs. Disruptions in hematological and histological parameters were found in the infected fish. Both Cc-AgNPs and Pg-AgNPs showed recovery on the hematological and histological parameters. Analysis of oxidative stress and cytokine markers also revealed provoking evidence of the positive impact of Cc-AgNPs and Pg-AgNPs treatment against disease progression in the infected fish. The major finding of the study was that the higher concentrations of the nanoparticles (50 µg/L in the case of Cc-AgNPs and 75 µg/L in the case of Pg-AgNPs) were more effective in fighting against disease. In conclusion, our work presents novel insights for the use of green-synthesized AgNPs as economic and innocuous antibacterial candidates in aquaculture.

Enhancement of Soybean Meal Alters Gut Microbiome and Influences Behavior of Farmed Atlantic Salmon (Salmo salar).

Atlantic salmon (Salmo salar) is one of the worlds most domesticated fish. As production volumes increase, access to high quality and sustainable protein sources for formulated feeds of this carnivorous fish is required. Soybean meal (SBM) and soy-derived proteins are the dominant protein sources in commercial aquafeeds due to their low-cost, availability and favorable amino acid profile. However, for Atlantic salmon, the inclusion of soybean meal (SBM), and soy protein concentrate (SPC) in certain combinations can impact gut health, which has consequences for immunity and welfare, limiting the use of soy products in salmonid feeds. This study sought to address this challenge by evaluating two gut health-targeted enhancements of SBM for inclusion in freshwater phase salmon diets: enzyme pre-treatment (ETS), and addition of fructose oligosaccharide (USP). These were compared with untreated soybean meal (US) and fish meal (FM). This study took a multi-disciplinary approach, investigating the effect on growth performance, gut microbiome, and behaviors relevant to welfare in aquaculture. This study suggests that both enhancements of SBM provide benefits for growth performance compared with conventional SBM. Both SBM treatments altered fish gut microbiomes and in the case of ETS, increased the presence of the lactic acid bacteria Enterococcus. For the first time, the effects of marine protein sources and plant protein sources on the coping style of salmon were demonstrated. Fish fed SBM showed a tendency for more reactive behavior compared with those fed the FM-based control. All fish had a similar low response to elicited stress, although ETS-fed fish responded more actively than US-fed fish for a single swimming measure. Furthermore, SBM-fed fish displayed lower repeatability of behavior, which may indicate diminished welfare for intensively farmed fish. The implications of these findings for commercial salmonid aquaculture are discussed.

Melaleuca cajuputi leaf extract accelerates wound healing in African catfish, Clarias gariepinus

African catfish Clarias gariepinus is a scale-less fish prone to injury from high stocking under captive condition. Untreated wounds are susceptible to pathogenic infections that can cause biological and economic losses. This study evaluated the potential of Melaleuca cajuputi leaf extract (MCLE) for wound treatment in artificially injured C. gariepinus. Methanol extracts of M. cajuputi were freeze-dried and applied as treatment solutions as follows; 0.0 mg/L, 12.7 mg/L, 25.4 mg/L, and 38.1 mg/L. Tetracycline was used as a positive control group. The fish were artificially injured (i.e., laceration of 1 cm long, 0.4 cm depth) on both lateral sides and allowed to swim in the treatment solutions for 30 days. Wound healing progress, histological changes, hematological and biochemical parameters are herein reported. Results revealed that MCLE treatments caused faster epidermal cell migration, epidermal covering, and cell proliferation as early as 1 h after the artificial injury was inflicted compared to the control. At 3 h, the MCLE treatment at 12.7 and 25.4 mg/L caused the wounds to be closed and initiated the formation of the basement membrane; where these conditions were found only after 6 h with the tetracycline and control treatments. Meanwhile, the vascularization was found to occur after about 6 h in the 12.7 and 25.4 mg/L MCLE treated fish, whereas the process was delayed until 12 h in untreated fish. Our finding shows that treatment of fish wounds for 30 days with MCLE did not affect the health status of the fish as no significant changes (p > 0.05) were observed between the MCLE-treated and control groups for most parameters. It was concluded that the treatment of injured C. gariepinus can be done using MCLE concentration between 12.7 and 25.4 mg/L to accelerate healing.

Behavioral and histopathological changes of Clarias gariepinus as a predatory fish against Culex pipiens larvae following exposure to sublethal concentration of quinclorac and bensulfuron-methyl based herbicide

Summary Clarias gariepinus is one of the widespread culturable freshwater fish species in Africa, which is prevalent in various natural and human-made aquatic habitats including rice-fish system. This fish species displays predation potential on the aquatic stages of mosquitoes. Bensulfuron-methyl and quinclorac are herbicide active substances that have been extensively applied in rice culture in Egypt and other countries worldwide. This study assessed the adverse effects of sublethal concentration of a commercial herbicide formulation containing quinclorac and bensulfuron-methyl on the predation potential of C. gariepinus female and male predatory fish on Culex pipiens mosquito larvae. Also, stomach and intestine histopathology of the treated fish was investigated. The exposure of C. gariepinus to sublethal concentration of quinclorac and bensulfuron-methyl based herbicide produced detrimental effects on prey consumption and histopathological changes in the stomach and intestine of the fish. The mosquito consumption by the treated female and male fish decreased significantly compared to the untreated fish of both sexes. The histological changes in the intestines were hyperplasia of the intestinal epithelium and goblet cells; edema of lamina propria and broad intestinal villi, and distortion in intestinal villi in comparison to control. The stomach histopathology changes were necrosis and sloughing of mucosal epithelium with severe damage of sub-mucosa. Thus, the tested herbicide at sublethal concentration on C. gariepinus decreased the prey consumption on mosquito larvae and caused histopathological alterations in the fish that may impair its digestive physiology. These findings suggest a threat of the tested herbicide to C. gariepinus survival and potential as a native successful biocontrol agent against Cx. pipiens larvae.

ROLE OF KAOLIN ON HEMTOLOGICAL, BIOCHEMICAL AND SURVIVAL RATE OF CYPRINUS CARPIO CHALLENGED WITH PESUYDOMONAS AERUGINOSA

In present study, we assessed the role of kaolin [(Al2Si2O5(OH)4), an inert clay], for treatment of common carp, Cyprinus carpio experimentally infected with Pesudomonas aeruginosa. Fish were experimentally challenged with P. aeruginosa (LD50= 2±0.2×109 CFU/ml), in untreated water or water treated with addition of kaolin at levels of 4, 6 and 8g/l (G1, G2 and G3 respectively). Over the 5‐day course of kaolin treatment led to significantly (P ≤ 0.05) improved of survival (100%) in treated groups (G2 and G3) as compared to untreated fish (infected group; 75% survival). Considerable changes were observed in blood parameters, leucocyte count recorded significant increase (P≤0.05) in G2 and G3 relative to C- and C+ groups. Erythrocyte count, Hb content and HT(%) reported significant decrease (P≤0.05) in all treated groups (G1, G2 and G3) related to C- group. Globulin level registered significantly increased (P≤0.05) in G2 and G3 than C+ group. The current study strongly recommends that treatment of common carp infected with kaolin at 6 and 8g/l improves survival, hematological and biochemical profile, against P. aeruginosa. Future complete molecular studies are required before application of kaolin as a treatment in aquaculture.

Irradiation as a Promising Technology to Improve Bacteriological and Physicochemical Quality of Fish.

Fish is an excellent source of protein and other essential minerals and vitamins; nevertheless, several food-borne disease outbreaks have been linked to the consumption of different types of fish. Therefore, we aimed to overcome these health threats by evaluating gamma radiation as a good fish preservation method. The aerobic plate count (APC), identification of most common pathogenic bacteria, organoleptic properties, proximate composition, and other chemical evaluations were detected in both untreated and gamma-treated fish. The overall grades of organoleptic evaluations ranged from good to very good. Fortunately, the overall chemical analysis of all examined fish samples was accepted. For the untreated fish samples, the APC was within and above the permissible limit (5 × 107 CFU/g). Pathogenic bacteria were detected with a high prevalence rate, especially S. aureus, which was found in high percentages among examined untreated fish samples. Regarding the treated fish samples, APC and pathogenic bacterial counts were reduced in a dose-dependent manner, and the irradiation at dose 5 KGy resulted in complete eradication of the aerobic plate count (not detectable) with a mean reduction percentage equal to 100%. However, gamma irradiation has no significant effect on proximate composition; particularly, carbohydrates, proteins, and lipids were not significantly affected by low and medium doses of radiation. Therefore, gamma irradiation is a highly effective fish preservation method without any effect on fish quality. Additionally, gamma irradiation as a cold process is an attractive technology for solving the problem arising from fish-borne pathogens, and it has been purposed in this study as a cheap and safe method for reducing microbial contamination of fish.

Benzo(a)pyrene exposure in early life suppresses spermatogenesis in adult male zebrafish and association with the methylation of germ cell-specific genes

Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that are widely present in aquatic ecosystems. To assess the impact of early-life exposure to benzo[a]pyrene (BaP), a representative PAH, on reproductive ability in adult male zebrafish (Danio rerio), fertilized embryos were exposed to 0.05, 0.5, 5 and 50 nM of BaP for 96 h, and then the hatched larvae were raised to adulthood in clean water. In one-year-old male fish, the percentage of spermatozoa in testis was significantly reduced in the 0.5, 5 and 50 nM treatments. When the treated fish were mated with untreated fish, significantly decreased rate of egg fertilization and hatching success and significantly elevated malformation rate the F1 larvae were observed in the 0.5, 5 and 50 nM treatments. The transcriptional levels of genes along the brain-pituitary-gonadal axis, involving gnrh3, gnrhr3, fshβ, lhβ, lhγ, lhrγ and ar, were downregulated. In addition, embryonic BaP exposure upregulated the promotor methylation of germ cell-specific genes in the testis of adult fish. The upregulated methylation of ddx4, dnd1, nanos2 in the testis might be associated with the downregulated mRNA levels of these genes, which could be another reason for the inhibition of spermatogenesis. These results indicate that early-life exposure to BaP suppress the reproductive capability of adult male fish, which would cause a decrease in fish population.

Effect of Ultra-High-Pressure Homogenization Processing on the Microbiological, Physicochemical, and Sensory Characteristics of Fish Broth.

The effect of ultra-high-pressure homogenization (UHPH) treatments at 300 MPa at inlet temperatures (Ti) between 45 and 75 °C on the microbiological, physical, and sensorial characteristics of fish broth was evaluated. Before the application of UHPH treatments, different fish broth formulations were tested, selecting the formula with the best organoleptic and nutritional characteristics and the lowest cost, containing 45% monkfish heads and rock fish in the same proportion. The microbiological shelf-life of fish broth during cold storage at 4 and 8 °C was extended by a minimum of 20 days by applying UHPH treatments at inlet temperatures (Ti) between 45 and 65 °C. Fish broth UHPH-treated at Ti = 75 °C was microbiologically sterile during storage at 4 °C, 8 °C, and room temperature. Fish broth UHPH-treated was physically stable, significantly reducing the particle size. Color showed higher luminosity and lower yellowness as the inlet temperature increased. In fish broth UHPH-treated at Ti = 75 °C, selected for its microbiological stability, no differences were observed in the nutritional composition, antioxidant activity, and sensorial perception compared to untreated fish broth. Hence, UHPH treatments showed to be an alternative to preserving fish broth with an improved microbiological shelf-life and good sensorial characteristics.