Gabriela Tomas Jerônimo

The aim of this study was to evaluate the pharmacokinetics of eugenol in pacu (Piaractus mesopotamicus) juveniles following exposure to an immersion bath. Pacu juveniles (n = 42) with an average weight of 546.40 ± 74.51 g and total length of 25.43 ± 1.52 cm were subjected to a bath with 100 mg L⁻¹ eugenol previously dissolved in 95% ethanol (1:10). After a 10-min immersion, the fish were transferred to anesthetic-free aquaria for recovery. Blood, kidney, muscle, spleen, gills, and brain samples were collected at intervals 0, 0.5, 1.0, 3.0, 6.0, 12.0, and 24.0 h post-anesthesia. Pharmacokinetic parameters were calculated using non-compartmental methods. The highest eugenol concentrations were recorded immediately after anesthesia (0 h) in all tissues, in descending order: plasma > kidney > muscle > spleen > gills > brain. The plasma and brain half-lives of eugenol were 1.12 h and 0.73 h, respectively, with elimination constants of 0.62 and 0.95 per hour. In muscle and kidney tissues, the half-lives were 0.14 h and 0.09 h, with elimination constants of 4.97 and 7.44 per hour, respectively. In the spleen and gills, the half-lives were 0.21 h and 0.23 h, with elimination constants of 3.26 and 3.07 per hour. In conclusion, eugenol is rapidly absorbed and eliminated in growing phase pacu, reaching peak concentrations soon after anesthesia and showing a significant reduction up to 24 h.

The Amazon rainforest and its rivers host a vast biodiversity, including many unique yet undiscovered species, particularly among Amazonian fish. These organisms can be susceptible to ectoparasites, such as isopod crustaceans. This study describes the presence of the isopod Braga patagonica parasitizing Hoplias malabaricus in the state of Maranhão, located in the eastern Amazon region of Brazil. Isopod specimens were collected from the fish bodies in two sampling periods conducted between 2021 and 2022 and identified using dichotomous keys based on morphological analysis and measurements of the parasites. Furthermore, parasitological indices were calculated, including prevalence rate (P%), mean intensity (MI), and parasite abundance (PA). A total of 25 parasites, including females and males, were found fixed in the gill cavity, on the integument, and near the pectoral and pelvic fins. During the first collection period, the hosts exhibited a prevalence rate of 100%, with MI and PA of 1.0 ± 0.00. In contrast, during the second collection period, the prevalence rate decreased to 66.67%, with MI of 1.0 ± 0.04 and PA of 0.64 ± 0.49. Females were larger, measuring approximately 2.09 cm in length and 1.09 cm in width, while males reached 1.96 cm in length and 0.86 cm in width, and displayed a lighter coloration compared to the females in both collections. This study establishes a new geographical occurrence of Braga patagonica in the state of Maranhão, in Northeast Brazil, providing a comprehensive analysis of the morphological characteristics of this isopod. The results provide valuable insights into the distribution of the Cymothoidae family in the Eastern Amazon.

This study investigated the in vitro antimicrobial and anthelmintic effect of copper nanoparticles (CuNPs) against the bacterium Aeromonas hydrophila, the monogeneans Dactylogyrus minutus, Dactylogyrus extensus, Gyrodactylus cyprini, and the cestode Schyzocotyle acheilognathi, as well as their toxicity to Cyprinus carpio Koi. In the antimicrobial in vitro test, the inhibition zone method and minimum inhibitory concentration (MIC) were performed. In order to determine the time and efficacy of monogenean parasite mortality, the parasites were exposed to CuNP concentrations of 20, 50, 100, 150, 200, and 300 mg L⁻¹, and a control group with tank water and one with copper sulphate pentahydrate (CuSO₄.₅H₂O) at a concentration of 0.3 mg L⁻¹, performed in triplicate. The parasites were observed every 10 min for 300 min, and mortality was recorded. For the cestodes, parasites were immersed in CuNP concentrations of 50, 100, 150, and 300 mg L⁻¹. At the end of the in vitro tests, the anthelmintic efficacy of each treatment was calculated. To assess the tolerance and toxicity in fish, they were exposed to CuNP concentrations of 0.6, 1.25, 2.5, 5, 10, 20, and 50 mg L⁻¹ for 12 h. The MIC demonstrated that CuNPs effectively inhibited the growth of A. hydrophila up to a dilution of 12,500 mg L⁻¹ and showed an inhibition zone of 14.0 ± 1.6 mm for CuNPs. The results of anthelmintic activity showed a dose‐dependent effect of concentration for both groups of parasites, with the most effective concentration being 300 mg L⁻¹ in 120 min. In the toxicity test, the carps showed tolerance to lower concentrations. The study indicated that CuNPs were effective against the studied pathogens. However, it proved to be toxic to fish at high concentrations. The use of low concentrations is recommended still requires further investigation.

The production of silage using fish viscera can be carried out with straightforward methods and permits the exploitation of nutrients that are usually discarded. This process fosters the concept of circular aquaculture. The aim of this study was to evaluate the inclusion of increasing levels of fish viscera silage (VS) on the physical quality of the feed pellets and their effects on their growth performance, health parameters and on economic indices when the experimental extruded feed was offered to tambaqui. A fermented fish VS produced in‐house was included in increasing levels on a wet‐basis in the formulation of five experimental diets (VS 0%, VS 5%; VS 10%; VS 15% and VS 20%). Juvenile tambaqui (~22.6 g) were stocked in fibreglass tanks of 700 L (n = 4; 21 fish per tank) with a recirculation system and the five experimental diets were attributed in a completely randomized design. The fish were fed with the experimental diets (to apparent satiation) for 13 weeks. At the end of the trial, no significant differences were observed for production performance. Fish fed with the highest inclusion level of VS presented the highest concentration of plasma cholesterol, but this was still within acceptable values for this species. The inclusion of fish VS in diets for juvenile tambaqui reduced the activity of the plasma ALT enzyme, confirming normal liver function. Extruded feed containing fish VS had a production cost of US$ 0.95 per kg, which does not significantly impact the economic indices. Up to 20% of fish VS can be included in the extruded feed formulation for juvenile tambaqui without impairing growth performance or affecting health parameters.

The aim of this study was to evaluate the effect of supplementing feed with a functional mixture of immunomodulators, including β-glucans, nucleotides, ascorbic acid, and alpha-tocopherol, associated with a diet with lower levels of animal protein (11.5%) and higher levels of soybean meal (43.5%), on the zootechnical performance, health, hematological and immunological parameters, intestinal morphology, centesimal composition, and intestinal microbiome of juvenile Nile tilapia (initial weight 1.88 g ± 0.25 g, mean ± standard deviation). Two isocaloric and isoproteic diets (35% crude protein) were formulated, one with the inclusion of the immunostimulant functional mixture (40 kg·t⁻¹), composed of 150 mg·kg⁻¹ of nucleotides, 1000 mg·kg⁻¹ of β-glucans, 1000 mg·kg⁻¹ of ascorbic acid (vitamin C), and 20 mg·kg⁻¹ of alpha-tocopherol (vitamin E), and another without. The combined supplementation of nucleotides, β-glucans, ascorbic acid, and alpha-tocopherol resulted in a 59.95% increase in final weight, 64% weight gain, 66% daily gain, a 21.31% decrease in feed conversion rate, and double the retention of body protein. Supplementation also improved intestinal morphology and modulated the intestinal microbiome, increasing Chao-1 diversity. Transmission electron microscopy confirmed that fish fed with both diets exhibited intact intestinal mucosal membranes. Supplementation did not alter the hematological and immunological parameters, suggesting that there was no overstimulation of the fish’s immune system. This work allows us to evaluate the effect of reducing the use of animal protein in the diets of fish, along with the effects of nucleotides, β-glucans, ascorbic acid, and alpha-tocopherol. Together, these compounds can provide fish with the necessary tools to achieve optimal health and growth.

In Brazil, studies evaluating the concentration of trace metals in fish farms are scarce. Therefore, studies investigating the presence and levels of these metals in aquatic biota, particularly in fish tissues, are crucial for developing appropriate strategies to mitigate the impact of possible toxic metals. Herein, we investigated the levels of trace metals (Cr, Mn, Co, Ni, Cu, Zn, Al, Ag, Cd, Pb, Fe, Na, Mg, Ca, K, and Ba) in water, feed, and sediment, as well as the bioconcentration and bioaccumulation factors in tambaqui muscles (Colossoma macropomum). For this purpose, eight commercial fish farms, which are also engaged in other agricultural activities, were selected. Fe, Zn, Mg, and Cr concentration in tambaqui muscles exceeded the limits set by the Brazilian regulations for daily consumption by adults. Mn, Zn, Al, Pb, Fe, Na, Cu, Co, Ag, Cd, and Ba levels were substantially higher in the liver tissue of tambaquis than those in the muscle tissue. The most prevalent metals found in the feed were Ca, K, Na, Mg, and Fe. However, the levels of Cr and Cd in the sediment, as well as Pb, Mn, Cu, and Fe in the water, exceeded the maximum limits allowed by the Brazilian legislation. The highest bioconcentration factors were observed for the metals, Na, Zn, and K, with concentrations up to 4.74, 12.61, and 72.08 times, respectively, higher in tambaqui muscle compared to those in water. The bioaccumulation factors for Ca, Zn, Mg, Na, and K were 2.90, 6.96, 21.21, 212.33, and 492.02 times, respectively, higher in the muscle tissue than those in the sediment values in fishponds across all fish farms. Therefore, our findings suggest that tambaquis have a remarkable ability to bioaccumulate trace metals, particularly the essential ones, and can be categorized as a bioindicator species for environmental quality. Furthermore, we observed that, although water exhibits the highest prevalence and diversity of elements above the values recommended by the Brazilian legislation, sediment is the primary source of trace metal contamination for tambaquis.

This study aimed to evaluate the anesthetic activity of Ocimum basilicum essential oil and the distribution and depletion of its major compounds in different tissues of the pacu, Piaractus mesopotamicus. Juveniles (319.08 ± 9.14 g) were individually anesthetized with six concentrations of essential oil from O. basilicum (150, 180, 210, 240, 270, and 300 mg L⁻¹), while in a second experiment, fish (492.39 ± 51.51 g) were subjected to a 10 min immersion bath with essential oil from O. basilicum (300 mg L⁻¹). After anesthetic recovery, blood and tissue samples of the brain, gills, liver, spleen, and white muscle were collected at 0, 0.5, 1.0, 3.0, 6.0, 12.0, and 24 h. A 300 mg L⁻¹ concentration induced anesthesia in the shortest time (193.11 ± 9.31), while at 270 and 300 mg L⁻¹ concentrations, the anesthetic recovery period was the longest (244.33 ± 12.44) Methyl chavicol and linalool were quantified in all tissue samples. The plasma concentrations of methyl chavicol differed (p < 0.05) at all evaluated times. Linalool decreased (p < 0.05) from 0 to 1 h and decreased again only after 12 h. Reduction percentages in 24 h were 92.9% for methyl chavicol, and 97.2% for linalool. Elimination of the compounds methyl chavicol and linalool is slower in the gills, where lower elimination constants (0.03 and 0.15 per h) and longer half-lives (25.84 and 4.53 h), respectively, are noted. In general, essential oil from O. basilicum compounds was readily eliminated, showing promising potential for use as an anesthetic in aquaculture.

The aim of this study was to observe how abiotic and biotic factors in a tropical region influence the rate of monogenean parasitism in Nile tilapia (Oreochromis niloticus) that are farmed in net cages. A total of 240 sexually reversed fish were analyzed, and 20 from each culture stage were collected during each sampling month. Overall, 60 fish were sampled in April (autumn), 60 in August (winter), 60 in November (spring), and 60 in February (summer). Fish were collected from a commercial fish farm located in Capivara Reservoir in the lower Paranapanema River region of Paraná, Brazil. In total, 3290 monogenean parasites were collected from fish gills of the following species: Cichlidogyrushalli, C. thurstonae, Scutogyruslongicornis, C. cirratus, C. sclerosus, and C. tilapiae. Higher parasitological indices were observed in colder seasons with lower precipitation. Autumn had the highest parasitic infection values compared to the other seasons. The occurrence of monogenean parasites showed a negative correlation with season, in contrast to the culture stage, in which there was a positive correlation. These results may provide a means for establishing adequate fish farm management to predict periods of high monogenean infestation.

Fish parasites are excellent bioindicators of environmental contamination because they respond quickly to water pollutant chemicals, and they can accumulate high concentrations of trace metals compared to their hosts. Here, we investigated the bioaccumulation pattern of the following: Cd, Ca, K, Na, Mg, Fe, Al, Zn, Ba, Mn, Cu, Pb, Cr, Ni, and Co. We investigated the presence of trace metals in the acanthocephalan parasite Neoechinorhynchus buttnerae, and the bioaccumulation factors (BAFs) of metals were tested in the food, muscle, and liver of its host fish Colossoma macropomum (tambaqui). We used samples from four commercial fish farms that also conduct other agribusiness activities. Tissues of the fish along with their parasites were subjected a trace metal concentration analysis by inductively coupled plasma optical emission spectrometry. Most of metals showed significantly higher presence in N. buttnerae than in tambaqui (p < 0.05), with increased level of Na, Pb, Ca, Mn, Zn, Al, and Fe in fish muscle and that of Cr, Ni, Zn, Al, Ca, and Ba in fish liver. Considering all the fish farms, the highest values of BAF were observed for Fe, Al, Zn, and Mn with concentrations up to 35.63, 26.88, 14.12, and 6.66 times higher in acanthocephalan tissues than in the fish muscle, respectively. Moreover, Ba, Ca, and Al showed concentrations up to 18.11, 12.18, and 11.77 times higher in acanthocephalan than in the liver of tambaqui. Our results indicate that the higher the levels of these metals in the parasite, the lower their concentrations in the muscular and hepatic tissues of the fish. Therefore, we suggest that N. buttnerae can directly influence the concentrations of trace metals in the fish tissues and accumulate both essential trace (Fe, Zn, Mn, and Ca) and toxic elements (Al, Pb, and Ba) in the host.