Protium heptaphyllum essential oil from the fruit as a sedative and anesthetic in Rhamdia quelen: influence in cardiac frequency, biochemical, and oxidative parameters.

This study aimed to evaluate the effects of Protium heptaphyllum fruit essential oil (PHEO) on the physiology of silver catfish (Rhamdia quelen) during anesthesia and recovery, through studying echocardiograms, oxidative status, and metabolic parameters. Three experiments were performed: (1) 50 silver catfish juveniles were submitted to anesthesia and recovery tests with 300, 400, 500, 600, and 700 mg L-1 of PHEO. (2) Echocardiogram analysis was performed in anesthetized and non-anesthetized fish. (3) Biochemical parameters were evaluated at 0, 30, 60, and 120 min of recovery after being anesthetized for 3 min with 600 mg L-1 PHEO. Times to sedation and deep anesthesia were reduced with PHEO increasing concentrations. The echocardiogram showed a higher cardiac rate in anesthetized fish. Plasma glucose levels increased in control fish through recovery time, but anesthetized fish showed lower levels than controls at 120 min of recovery. Metabolic parameters such as plasma and hepatic glucose did not show changes considering the recovery time of up to 120 min. Hepatic glycogen, lactate, and triglycerides reduced their levels over recovery times. Fish anesthetized enhanced superoxide dismutase activity and thiobarbituric acid reactive substances levels but decreased reduced glutathione (GSH) levels at 30 min compared to controls. After 60 min, GSH values were significantly higher in anesthetized fish than in controls. These results suggest that PHEO at 600 mg L-1 is an effective anesthetic for the rapid handling of silver catfish, providing stable metabolic parameters and enhanced antioxidant responses during recovery. Echocardiogram analysis confirms the anesthetic effect, supporting PHEO as a viable and efficient option for fish anesthesia in aquaculture. The use of PHEO in aquaculture can enhance fish welfare by reducing stress during handling and transportation, potentially leading to improved growth, health, and survival rates.

Essential oil of Aloysia citriodora Paláu and citral: sedative and anesthetic efficacy and safety in Rhamdia quelen and Ctenopharyngodon idella.

OBJECTIVE: To verify the efficacy of citral in inducing sedation and anesthesia in silver catfish (Rhamdia quelen) and grass carp (Ctenopharyngodon idella) and to assess the safety of essential oil (EO) of Aloysia citriodora and citral in inducing and maintaining anesthesia in silver catfish. STUDY DESIGN: Clinical study, randomized, parallel, multi-arm with control group in target species. ANIMALS: A total of 96 juvenile and 72 adult silver catfish and 80 juvenile grass carp were used. METHODS: Silver catfish and grass carp were exposed to different concentrations of citral, 15-675 and 15-600 µL L-1, respectively, during the maximum period of 30 minutes to verify sedation and anesthesia induction and recovery times. In addition, for anesthetic induction, silver catfish were exposed to the EO of A. citriodora and citral at 225 µL L-1 for 3.5 minutes. Then, fish were transferred to an anesthesia maintenance solution at 50 µL L-1 for 10 minutes to assess hematologic and biochemical variables at 60 minutes, 2 and 6 days after treatment. RESULTS: Citral only induced sedation from 15, 25 and 40 µLL-1 in both species. Anesthesia without mortality was induced in silver catfish at 50-600 µL L-1 and grass carp at 75-450 µL L-1. At 675 and 600 µL L-1, mortality was recorded in silver catfish and grass carp, respectively. The EO of A. citriodora and citral were safe in inducing and maintaining anesthesia in silver catfish, with mean corpuscular hemoglobin concentration being the only variable that varied in relation to time and treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Citral was effective in inducing sedation and anesthesia in both species. In addition, A. citriodora EO and citral were safe in inducing and maintaining anesthesia in silver catfish. Both agents are promising substances for the development of new drugs for fish.

The influence of dietary Motore™ supplement on antioxidant status to Aeromonas hydrophila infection in Rhamdia quelen.

This study points to evaluate the effects of pre-treatment with standardized dry extract of Curcuma longa (Motore™) added to the diet (0; 250; 500; and 750 mg/kg) on oxidative stress parameters, longevity, and therapeutic success in Rhamdia quelen experimentally infected with Aeromonas hydrophila (MF 372510). After treatment, the liver and kidney were collected to determine non-enzymatic oxidative parameters such as the formation of thiobarbituric acid reactive substances (TBARS), non-protein thiols (NPSH), and quantification of reactive oxygen species (ROS) levels. Also, two enzymatic antioxidant parameters were evaluated: superoxide dismutase (SOD) and catalase (CAT) activities. The results showed an increase of ROS and TBARS levels, a depletion in NPSH, and a decrease of SOD and CAT activities in infected fish compared to control. The highest Motore™ dose minimized the deleterious effect of A. hydrophila infection improving longevity, oxidative status, and survival rate. The addition of 750 mg Motore™/kg feed is recommended for silver catfish in fish farming. Serious economic losses in Rhamdia quelen culture caused by Aeromonas hydrophila infections can be prevented by the addition of Motore™ to the diet.

Autochthonous vs allochthonous probiotic strains to Rhamdia quelen.

The aim of this study was to obtain an autochthonous probiotic candidate strain from the silver catfish (Rhamdia quelen) intestinal tract, comparing its in vivo performance with an allochthonous probiotic isolated from another fish, Nile tilapia (Oreochromis niloticus), in a growth performance assay. The study was divided in two parts: in vitro and in vivo assay followed by challenge with A. hydrophila. In the in vitro assay, the species-specific isolated strain Lactococcus lactis presented characteristics such as: absence of hemolysis, antagonism to bacterial pathogens isolated from freshwater fish, and considerable speed of duplication. In the in vivo trial, both fish supplemented with autochthonous or allochthonous strains presented an increase the final concentration of lactic acid bacteria in the intestinal tract of the fish after 60 days of dietary supplementation reaching concentrations of 1 × 107 CFU g-1 and 4 × 107 UFC.g-1, respectively. In addition, the autochthonous strain increased the mean corpuscular hemoglobin (MCH) of the treated animals, but no significant differences were observed in the other hemato-immunological and zootechnical parameters between treatments. After challenge with Aeromonas hydrophila, only animals that received autochthonous probiotic supplementation showed an increase in the serum total immunoglobulin concentration, but not enough to observe a significant difference in the survival rate between the treatments. Dietary supplementation of the probiotic allochthonous strain did not demonstrate any effects superior to those of the isolated autochthonous strain. Although the autochthonous strain did not present significant improvements in the other parameters evaluated in this study, it was able to inhibit bacterial pathogens in vitro, to increase the final concentration of LAB's and the amount of immunoglobulin after experimental challenge, demonstrating probiotic potential. This study demonstrated for the first time the isolation and in vivo use of an autochthonous probiotic strain isolated from silver catfish, as well as its comparative evaluation with the performance of allochthonous probiotic.

Linseed fibers modulate the production of short-chain fatty acids and improve performance and plasma and skin mucus parameters of silver catfish (Rhamdia quelen).

This study was conducted to evaluate the prebiotic action of distinct linseed fibers on diets for silver catfish (Rhamdia quelen) juvenile. For this, soluble and insoluble fractions of linseed fiber were concentrated separately and combined in four ratios (1:0.5, 1:1, 1:2, 1:4), which were added in diets and evaluated along with a control diet. After 45 days receiving the experimental diets, the animals were submitted to biometry for data collection and samples. The experimental design was completely randomized, data were submitted to analysis of variance, and the means were compared by Tukey's test (P < 0.05). Fish performance was higher for the group that received the 1:2 and 1:4 diets. The production of intestinal acetic acid was higher in fish fed on the 1:2 diet, and butyric acid was higher with 1:4 diet and the propionic acid with the control diet. The control diet led to lower counts of goblet cells. Total proteins and globulins in plasma, mucoprotein, total immunoglobulins, and cutaneous mucus pH were higher in fish fed on diets 1:2 and 1:4. Cortisol levels and intestinal pH were lower in these treatments. The linseed fiber intake increased total plasma immunoglobulins and plasma alkaline phosphatase activity and in mucus. It was concluded that the use of 1:2 and 1:4 soluble fiber/insoluble linseed in the diet beneficially modulates the production of short-chain fatty acids in the digesta, with reflection on growth performance, number of goblet cells in the intestinal epithelium, and improvement in plasma and skin mucus parameters of fish.

The survival and hepatic and muscle glucose and lactate levels of Rhamdia quelen inoculated with Aeromonas hydrophila and treated with terpinen-4-ol, carvacrol or thymol.

The aim of this study was to evaluate the resistance of Rhamdia quelen (silver catfish) to Aeromonas hydrophila infection after treatment with pure and nanoencapsulated forms either terpinen-4-ol, thymol, or carvacrol and the effects of these treatments on fish metabolic responses. After A. hydrophila inoculation, fish were treated with 30 min daily baths for 6 consecutive days with terpinen-4-ol, thymol, or carvacrol in their pure or nanoencapsulated forms at concentrations of 5, 10, 15 or 25 mg L-1. A positive control group, negative control group and saline group were also included. Survival was evaluated at the end of treatment for six consecutive days. Muscle and liver were collected to determine glucose and lactate levels. The fish treated with the nanoencapsulated form of the compounds had a high survival rate, similar to saline group and negative control groups. The carvacrol, thymol and terpinen-4-ol nanoencapsulated forms improved survival of silver catfish infected with A. hydrophila. Muscle and liver glucose and lactate levels are not indicated as biomarkers because they did not present any correlation between the metabolic state of the fish and the bacterial infection.

ß-Glucan improves wound healing in silver catfish (Rhamdia quelen).

The immune modulating activity of ß-glucan on aquatic species has been a matter of intense investigation. Here, we aimed to investigate the effect of ß-glucan on wound healing of silver catfish, a Neotropical South American scale-free fish. Small sections of skin and muscle (3 mm in diameter) were removed and fish were bathed daily with ß-glucan (0.1% and 0.5%) up to 28 days when cicatrization was complete. A group of fish similarly injured and non-exposed to ß-glucan was used as control. Wound closure and healing was monitored visually and by histopathological analysis. In fish bathed with 0.5% ß-glucan we found reduced blood cortisol levels at day one post-wounding and, by day 7 post wounding, the deposition of granulation tissue was higher compared to non-exposed fish. In addition, from day 7 forward, wound size was significantly lower in fish bathed with 0.5% ß-glucan. Histopathological analysis of the wounded site indicated a thin layer of immature epidermal cells at day one post wounding. A discrete inflammation with mixed inflammatory cell infiltrate was observed on wounded muscle and was lower by day 7 post wounding on fish bathed with 0.5% ß-glucan. By day 14 post wounding, the deposition of collagen fibers and the presence of fibroblast and new muscle fibers were higher in fish exposed to 0.5% ß-glucan, and dermis restoration was complete. Thus, our results indicate that in silver catfish wound healing occurs rapidly and improves greatly by daily bathing with ß-glucan.

The antibacterial and physiological effects of pure and nanoencapsulated Origanum majorana essential oil on fish infected with Aeromonas hydrophila.

This study evaluated the antibacterial activity of Origanum majorana essential oil (EOM) and nanocapsules of this oil (NOM) in silver catfish, Rhamdia quelen, infected with Aeromonas hydrophila, and addressed their effects on silver catfish hematological and metabolic parameters. Fish were inoculated with A. hydrophila (360 µL, at a concentration of 1.5 × 109 CFU mL-1) and submitted to 1 h daily baths with EOM (0 (control), 20 or 30 µL L-1), NOM (0 (control), 5 or 10 µL L-1) or a positive control containing florfenicol (30 µL L-1) called group Maxflor® for five consecutive days. All treatments improved the survival rate of the infected fish, but we suggest the treatment of A. hydrophila infections through daily baths with 20 µL L-1 EOM or 5 µL L-1 NOM for five consecutive days as these were the lowest effective concentrations tested. Silver catfish treated with EOM and NOM had higher lymphocyte levels, indicating stimulation of the immune system in these fish. The lowest liver glucose level was found in the group treated with the lowest concentration of NOM, and the lactate values in the liver and muscle of all groups were within the normal values reported for this species. In addition, nanocapsules required much less EOM to elicit effective antibacterial treatment.

Evaluation of the antioxidant system and neurotoxic effects observed in Rhamdia branneri (Teleostei: Heptapteridae) sampled from streams of the lower Iguazu River basin.

The use of multiple biomarkers has been shown to be an efficient method for evaluating environmental contamination. In this work, we evaluate neurotoxic effects and the antioxidant system responses of the R. branneri collected in two streams of lower Iguazu River basin, relating them with different percentage of vegetation coverture, presence of pesticides and fall and winter seasons. The biological samples were collected in March and August of 2015, from two streams that belong to the lower Iguazu River basin (Brazil): the Manoel Gomes River and the Arquimedes Stream. Soil analyses were performed, and the results showed the presence of the following organophosphates in the Manoel Gomes River and the Arquimedes Stream: disulfoton, methyl parathion, and ronnel. The present study detected inhibition of cholinesterase activity in the brain and muscle of fish samples during the fall from the Manoel Gomes River and the Arquimedes Stream. In the Manoel Gomes River, elevated lipoperoxidation was also observed during the fall. It was observed that the increase or decrease of biomarkers was related to temporal variation and, possibly, to the exposure of animals to agrochemicals. Although the Manoel Gomes River and the Arquimedes Stream are located in regions with large areas of vegetation, the soil analyses show that agrochemical residues are able to reach these locations, which suggests that the fauna are in contact with oxidant and anti-cholinesterase agents during the fall, in addition to respond differently during each season.

Effects of dietary microencapsulated Cymbopogon flexuosus essential oil on reproductive-related parameters in male Rhamdia quelen.

In aquaculture, nutrition and supplemented diets have been shown to affect broodstock reproductive performance. In this study, we investigated the effects of dietary supplementation with Cymbopogon flexuosus essential oil (CFEO) microcapsules on reproductive-related parameters in silver catfish (Rhamdia quelen) male broodfish. Adult male broodstocks were separated into three groups according to the concentrations of supplemented CFEO (0.0 = control; 1.0 or 3.0 mL per kg of diet). After 20 days under experimental conditions, the animals were euthanized and the gonads were harvested for gonadosomatic index, sperm analysis, oxidative stress, and histopathology; testosterone levels were measured in the plasma; gene expression of prl, smtl, pomca, and pomcb was assessed in the pituitary gland by real-time PCR. The results showed no alterations on reproductive parameters in R. quelen males treated with Cymbopogon flexuosus essential oil compared to the control-diet animals. In conclusion, CFEO microcapsules supplied for 20 days in the concentrations of 1.00 or 3.00 mL per kilogram of diet did not affect the reproduction criteria evaluated in this study in male silver catfish.

Triphenyltin hydroxide induces changes in the oxidative stress parameters of fish.

Among all organotin compounds , triphenyltin hydroxide (TPhTH) is widely used as fungicide and moluscicide in Brazil. However, the effects of TPhTH on the biochemical parameters of non-target organisms, such as fish, are little known. The aim of the present study is to assess the possible toxic effects of different concentrations of waterborne TPhTH on silver catfish belonging to species Rhamdia quelen. The fish were exposed to two different concentrations of TPhTH (1.08 and 1.70 µg/L as Sn) for 15 days and then compared to the control group (triplicate, n = 3). The antioxidant profile (catalase (CAT) and the glutathione S-transferase (GST)) and the oxidative stress parameters (TBARS-thiobarbituric acid-reactive substances and protein carbonyl (PC)) were set after the exposure to TPhTH. The TBARS level and the PC content increased in several organs of the Rhamdia quelen (brain, liver, muscle and gills) under the two concentrations of TPhTH in comparison to the control group. The CAT activity in the liver and gills has enhanced in all tested TPhTH concentrations. The GST activity increased in the brain, liver and muscle tissues under all the TPhTH concentrations. The significant changes in the biomarkers indicated that the investigated pesticide could have harmful effect on fish, in the field. However, these biomarkers were measured after the fish received doses lower than the recommended for use in agriculture.

Pre-sedation and transport of Rhamdia quelen in water containing essential oil of Lippia alba: metabolic and physiological responses.

The effects of transporting silver catfish (Rhamdia quelen) for 6 h in plastic bags containing 0 (control), 30 or 40 µL/L of essential oil (EO) from Lippia alba leaves were investigated. Prior to transport, the fish in the two experimental groups were sedated with 200 µL/L of EO for 3 min. After transport, dissolved oxygen, carbon dioxide, alkalinity, water hardness, pH, temperature and un-ionized ammonia levels in the transport water did not differ significantly among the groups. However, total ammonia nitrogen levels and net Na(+), Cl(-) and K(+) effluxes were significantly lower in the groups transported with EO of L. alba than those in the control group. PvO2, PvCO2 and HCO3(-) were higher after transporting fish in 40 µL/L of EO of L. alba, but there were no significant differences between groups regarding blood pH or hematocrit. Cortisol levels were significantly higher in fish transported in 30 µL/L of EO of L. alba compared to those of the control group. The metabolic parameters (glycogen, lactate, total amino acid, total ammonia and total protein) showed different responses after adding EO to the transport water. In conclusion, while the EO of L. alba is recommended for fish transport in the conditions tested in the present study because it was effective in reducing waterborne total ammonia levels and net ion loss, the higher hepatic oxidative stress in this species with the same EO concentrations reported by a previous study led us to conclude that the 10-20 µL/L concentration range of EO and lack of pre-sedation before transport are more effective.

Effect of Extraction Time on the Extractability and Physicochemical Properties of Pepsin-Soluble Collagen (PCS) from the Skin of Silver Catfish (Pangasius sp.).

The current study aimed to determine the effects of extraction time on the extractability and physicochemical properties of collagen from the skin of silver catfish (Pangasius sp.). Pepsin soluble collagen (PSC) was extracted for 24 and 48 h and analysed in terms of chemical composition, solubility, functional group, microstructure, and rheological properties. The yields of PSC at 24 h and 48 h extraction time were 23.64% and 26.43%, respectively. The chemical composition exhibited significant differences, with PSC extracted at 24 h showing better moisture, protein, fat, and ash content. Both collagen extractions indicated the highest solubility at pH 5. In addition, both collagen extractions exhibited Amide A, I, II, and III as fingerprint regions for collagen structure. The morphology of the extracted collagen appeared porous with a fibril structure. The dynamic viscoelastic measurements of complex viscosity (η*) and loss tangent (tan δ) decreased as temperature increased, and the viscosity increased exponentially as the frequency increased, whereas the loss tangent decreased. In conclusion, PSC extracted at 24 h showed similar extractability to that extracted at 48 h but with a better chemical composition and shorter extraction time. Therefore, 24 h is the best extraction time for PSC from silver catfish skin.

Modulation of expression of proinflammatory genes and humoral immune response following immunization or infection with Aeromonas hydrophila in silver catfish (Rhamdia quelen).

The early immune-related events arising from the interaction of antigen and innate immune cells are central to modulating the acquired immune response. Ideally, the immunizing antigen should elicit immunological changes similar to that observed after infection with the wild type pathogen. Here, we evaluated early changes on the expression of selected proinflammatory genes (TNF-α, IL-1ß, IRAK4 and myeloperoxidase) and innate immune parameters (serum myeloperoxidase, lysozyme and complement hemolytic activity) in silver catfish vaccinated or infected with Aeromonas hydrophila, the etiological agent of hemorrhagic septicemia. The humoral immune response and resistance to challenge were also evaluated in vaccinated and placebo inoculated fish. We found that the expression of TNF-α and IL-1ß genes was higher (p<0.05) in vaccinated or infected fish at 24 h post inoculation (p.i) compared to the control group but returned to basal levels at 72 h p.i. The expression of IRAK4 gene, however, was not altered by vaccination or infection. In addition, the natural hemolytic activity of complement was higher (p<0.05) at 24 h and 72 h p.i. in the vaccinated and infected groups; serum myeloperoxidase was higher (p<0.05) in these groups but only at 24 h p.i. and lysozyme activity was higher (p<0.05) only in the infected group at 72 h p.i. Furthermore, vaccination induced the production of IgM-like antibodies and protection to challenge with the A. hydrophila. Our results indicate that the vaccine formulation induces an immune response similar to that induced by the infecting pathogen and might be a valuable tool in the prophylaxis of hemorrhagic septicemia in silver catfish.

Post-thaw dilution of Rhamdia quelen sperm improves the reproductive success.

The aim was to evaluate the effect of a post-thaw dilution of Rhamdia quelen sperm in 1.1% NaCl (325 mOsm kg-1; pH 7.6; 24 °C) solution on the quality and reproductive capacity. Sperm from eight males were cryopreservation in nitrogen vapor at - 170 °C for 18 h in 0.25 mL straws in a freezing medium containing 5% fructose, 5% Powdered milk, and 10% methanol. The samples were thawed and post-thaw diluted (1:20) in NaCl solution or not (control). The higher spermatozoa velocities were observed in the post-thaw diluted samples (curvilinear (VCL) - 69 ± 11 µm s-1; average path (VAP) - 45 ± 8 µm s-1; straight-line (VSL) - 43 ± 8 µm s-1) compared to the control (VCL - 47 ± 10 µm s-1; VAP - 31 ± 6 µm s-1; VSL - 30 ± 6 µm s-1). Greater straightness (STR), progression (PROG), and beat cross frequency (BCF) were observed in the post-thaw diluted samples (STR - 96 ± 7%; PROG - 666 ± 128 µm; BCF - 42 ± 2 Hz) than in control (STR - 95 ± 5%; PROG - 463 ± 92 µm; BCF - 40 ± 2 Hz). The strongly curled tail was the only morphology change that differ between the post-thaw diluted (5 ± 2%) and control (2 ± 1%). Membrane integrity, mitochondrial activity, and normal larvae rate were not different between treatments. Fertilization and hatching were higher in the post-thaw diluted sperm (93 ± 3%; 82 ± 9%) when compared to control samples (65 ± 13%; 55 ± 17%). Were used oocytes from one female, limiting these results. The post-thaw dilution improved the sperm kinetics and reproductive parameters. Thus, this methodology can be included in the sperm cryopreservation protocol for R. quelen.

Effect of Smoking Methods and Natural Spices on Quality and Consumer Acceptance of Smoked Silver Catfish (Chrysichthys nigrodigitatus).

AIMS AND BACKGROUND: Fish serves as a good source of dietary protein which is very inexpensive in relation to other animal protein foods and it is an excellent component of human diet. This study assessed the effects of smoking methods and natural spices on studied parameters and consumer acceptance of smoked silver catfish (Chrysichthys nigrodigitatus). METHODS: One hundred samples of silver catfish were obtained by purposive sampling method. The fresh fish samples were smoked in two batches, the first batch was smoked with drum smoker and the second batch with oven smoker while the control was smoked without the natural spices. Rancidity indices (TVB-N, TMA-N, TBA and pH), microbiological analysis and sensory evaluation were carried out on smoked fish samples. The recent patents on edible fat blends (US20020031595A1), long chain fatty acids (WO2008085840A2) and esters of polyunsaturated fatty acids (US20090023808A1) helped in selecting the analytical methods. RESULTS: The results showed that there was statistical significant difference (P≤0.05) between total volatile base-nitrogen, trimethylamine values and pH of the smoked silver catfish samples treated with different concentrations of clove, ginger and garlic paste and those samples which were not treated with clove, ginger and garlic. This study showed that smoking methods has effects on quality indices, microbial quality and consumer acceptance of smoked silver catfish. Clove, ginger and garlic have some anti-oxidative effects on rancidity indices of smoked silver catfish as there was inverse relationship between clove, ginger and garlic and values of peroxide, free fatty acid and thiobarbituric acid. This was also observed for the microbial quality of the smoked silver catfish. There was also inverse relationship between clove, ginger and garlic and all the sensory parameters except for texture and as the concentrations of the natural spices increase the values of the sensory parameters decrease. CONCLUSION: In conclusion, this study showed that smoking methods affects the studied parameters, microbial quality and consumer acceptance of smoked silver catfish. Addition of clove, ginger and garlic had anti-microbial and anti-oxidative effects on quality parameters of smoked silver catfish. There was also a negative correlation between clove, ginger and garlic and all the sensory parameters except for texture.

Melaleuca alternifolia essential oil abrogates hepatic oxidative damage in silver catfish (Rhamdia quelen) fed with an aflatoxin-contaminated diet.

Mycotoxins are secondary metabolites produced by varieties of fungi that contaminate food and feed resources and are capable of inducing a wide range of toxicity. This problem is extensively aggravated due to the increasing replacement of fish meal by plant-derived proteins. Among the mycotoxins, aflatoxins have received a great deal of attention owing to their great prevalence in plant feedstuffs and to the detrimental effects on animals. The objective of this study was to evaluate whether dietary supplementation with tea tree (Melaleuca alternifolia) oil (TTO) would avoid or minimize the negative impacts on silver catfish (Rhamdia quelen) fed with aflatoxins-contaminated diets. Four treatments were tested: control (fish fed with a control diet); AFB (fish fed with a mycotoxin-contaminated diet - 1893 µg kg-1 of AFB1 and 52.2 µg kg-1 AFB2); TTO (fish fed with a control diet + 1 mL kg-1 of TTO), and TTO + AFB (fish fed with a mycotoxin contaminated diet - 2324 µg kg-1 of AFB1 and 43.5 µg kg-1 AFB2 + 1 mL kg-1 of TTO). Diets were tested in three replications and analyzed at days 5 and 10 of dietary intake. Significantly reduced antioxidant enzymes (SOD, GPx, and GST) and increased lipid peroxidation (LOOH) and protein carbonyl (PC) content in plasma and liver, with 16.6% mortality occurrence, were observed in the group fed aflatoxin-contaminated diet. Furthermore, aflatoxins also significantly increased plasmatic and hepatic ROS levels and decreased hepatic antioxidant capacity against peroxyl radical (ACAP) levels. Plasma cortisol levels were not altered by aflatoxicosis, but the intoxication induced hepatose. Notwithstanding, addition of TTO to the groups receiving aflatoxins showed a protective effect, avoiding the increase of ROS, LOOH, and PC levels in plasma and liver. Moreover, TTO treatment ameliorated the aflatoxin-associated liver damage. Thus, TTO supplementation at concentration of 1 mL kg-1 in feed may be used in fish to increase antioxidant status and reduce the negative effects caused by aflatoxins toxicity.

Aflatoxin B1-contaminated diet disrupts the blood-brain barrier and affects fish behavior: Involvement of neurotransmitters in brain synaptosomes.

It is known that the cytotoxic effects of aflatoxin B1 (AFB1) in endothelial cells of the blood-brain barrier (BBB) are associated with behavioral dysfunction. However, the effects of a diet contaminated with AFB1 on the behavior of silver catfish remain unknown. Thus, the aim of this study was to evaluate whether an AFB1-contaminated diet (1177 ppb kg feed-1) impaired silver catfish behavior, as well as whether disruption of the BBB and alteration of neurotransmitters in brain synaptosomes are involved. Fish fed a diet contaminated with AFB1 presented a behavioral impairment linked with hyperlocomotion on days 14 and 21 compared with the control group (basal diet). Neurotransmitter levels were also affected on days 14 and 21. The permeability of the BBB to Evans blue dye increased in the intoxicated animals compared with the control group, which suggests that the BBB was disrupted. Moreover, acetylcholinesterase (AChE) activity in brain synaptosomes was increased in fish fed a diet contaminated with AFB1, while activity of the sodium-potassium pump (Na+, K+-ATPase) was decreased. Based on this evidence, the present study shows that silver catfish fed a diet containing AFB1 exhibit behavioral impairments related to hyperlocomotion. This diet caused a disruption of the BBB and brain lesions, which may contribute to the behavioral changes. Also, the alterations in the activities of AChE and Na+, K+-ATPase in brain synaptosomes may directly contribute to this behavior, since they may promote synapse dysfunction. In addition, the hyperlocomotion may be considered an important macroscopic marker indicating possible AFB1 intoxication.

Gill bioenergetics dysfunction and oxidative damage induced by thiamethoxam exposure as relevant toxicological mechanisms in freshwater silver catfish Rhamdia quelen.

Thiamethoxam is a neonicotinoid pesticide utilized on a worldwide scale, it has been reported in freshwater ecosystems, and detected in fishery products. Nevertheless, there is a lack of information about thiamethoxam sublethal effects on the gills of freshwater fish, principally linked to energetic metabolism. In this context, creatine kinase (CK) is an enzyme of the phosphoryl transfer network that provides a temporal and spatial energy buffer to maintain cellular energy homeostasis in tissues with high energy requirements, such as gills. Based on this evidence, the aim of this study was to evaluate whether exposure to thiamethoxam impairs the cytosolic and mitochondrial CK activities in gills of Rhamdia quelen, and the involvement of oxidative stress in the energetic imbalance. Branchial CK (cytosolic and mitochondrial) activity and sodium­potassium pump (Na+, K+-ATPase) were inhibited, and adenosine triphosphate (ATP) levels decreased after 96 h exposure to 1.125 and 3.75 µg/L thiamethoxam compared to the control group. Moreover, levels of branchial thiobarbituric acid reactive substances (TBARS) and protein carbonylation increased at 3.75 µg/L thiamethoxam after 96 h of exposure compared to the control group, while the non-protein thiol (NPSH) content did not differ between groups. It is important to emphasize that all evaluated parameters did not recover after 48 h in clean water. To summarize, the data presented here clearly demonstrated that thiamethoxan exposure severely impairs cytosolic and mitochondrial CK activities, a key enzyme for gill energy buffering to maintain cellular energy homeostasis, and this effect appears to be mediated by oxidation of lipid and protein molecules, which consequently thereby induces oxidative stress.