RESUMO
Probiotic production in commercial culture media is expensive, so, it is necessary to design culture media based on "low-cost" components like agro-industrial by-products. Therefore, this study aimed to design an agro-industrial by-product-based culture media using whey, sugarcane molasses, and palm kernel cake as components to produce Lactococcus lactis A12, Priestia megaterium M4, and Priestia sp. M10 isolated from Nile tilapia (Oreochromis niloticus) associated gut microbiota. Higher bacterial concentrations were achieved at high whey concentrations and low concentrations of sugarcane molasses and palm kernel cake (PKC) using agitation. The optimal conditions were whey, 3.84% w/v; sugarcane molasses, 7.39% w/v; PKC, 0.77% w/v; and agitation speed, 75 RPM. Bacterial growth under optimal conditions was compared to that in commercial Brain-Heart Infusion (BHI) broth. L. lactis A12 showed similar growth in the optimal media and BHI. The estimated cost of the culture media based on component prices was USD $ 3.01/L, which is 86.93% lower than BHI broth (USD $ 23.04/L). It was possible to design a "low-cost agro-industrial by-product-based culture media to produce L. lactis A12 and the two Priestia species under monoculture conditions.
Assuntos
Meios de Cultura , Probióticos , Probióticos/metabolismo , Animais , Meios de Cultura/química , Lactococcus lactis/metabolismo , Lactococcus lactis/crescimento & desenvolvimento , Soro do Leite/microbiologia , Soro do Leite/metabolismo , Ciclídeos/microbiologia , Ciclídeos/metabolismo , Ciclídeos/crescimento & desenvolvimento , Microbioma Gastrointestinal , Melaço , Ração Animal , SaccharumRESUMO
MicroRNAs play crucial regulatory roles in various aspects of development and physiology, including environmental adaptation and stress responses in teleosts. RT-qPCR is the most commonly used method for studying microRNA expression, with the accuracy and reliability of results depending on the use of an appropriate reference gene for normalization. This study aimed to evaluate seven miRNAs (U6, Let-7a, miR-23a, miR-25-3, miR-103, miR-99-5, and miR-455) expression stability in different tissues of Nile tilapia subjected to osmotic stress. Fish were divided into two groups: a control and an experimental group, raised in 0 and 12 ppt salinity water respectively. After 21 days, brain, gills, liver, and posterior intestine were collected for analysis. Different mathematical algorithms (geNorm, NormFinder, BestKeeper, and the comparative ΔCt method) were employed to identify the most suitable reference miRNAs. The results indicate that the miR-455/miR-23a combination is a robust reference for normalizing miRNA expression levels in studies of osmotic stress responses in Nile tilapia. The stability of miRNA expression can vary depending on specific stress conditions and biological processes, underscoring the necessity of selecting appropriate normalizing miRNAs for each experimental context. This study identifies reliable reference genes for future RT-qPCR analyses of miRNA expression, thereby enhancing our understanding of molecular responses in fish to environmental challenges. These insights are fundamental to the development of new technologies for the improved management and sustainability of aquaculture practices.
Assuntos
Ciclídeos , MicroRNAs , Pressão Osmótica , Reação em Cadeia da Polimerase em Tempo Real , Animais , MicroRNAs/genética , MicroRNAs/metabolismo , Ciclídeos/genética , Ciclídeos/metabolismo , Reação em Cadeia da Polimerase em Tempo Real/normas , Padrões de ReferênciaRESUMO
The biofloc system is a biotechnology available for fish farming. Feeding rate is an important factor as it influences production costs and fish performance. The aim og this study was to evaluate the effects of feeding rates (2, 4, 6 and 8%) on growth, body composition, biochemical parameters and thiobarbituric acid-reactive-substances in tilapia. An experiment was conducted for 4 weeks, using 144 tilapias juvenile (initial weight = 12.06 ± 0.16 g), in triplicate for feeding rate tested. Fish fed three times a day, with comercial extrude diet (36%CP). After the end of the experiment, measurements were carried out and samples were collected for analysis. The feeding rate of 6% increased fish growth parameters, not differing between 4 and 8%. Since apparent feed conversion increased proportionally to increase in feed supply. Body protein of fish was higher at 8% feeding rate and the dry matter raised according to the rate. The feeding rates affected the body lipids in fish. Fish that fed 6% and 8% showed more lipid in the whole body. The biochemical parameters presented a lower amount of protein, amino acids, and hepatic glucose when employing a feed rate of 6%. Higher levels of ammonia were observed in the muscle of fish reared at 4% of feeding rate. There was no difference in amino acids and ammonia regarding the gills. Fish reared at lower feeding rates (2% and 4%) showed better oxidative parameters, which may be due to the consumption of the biofloc phenolic compounds. We recommend the use of a 4% feeding rate for juvenile tilapia in a Biofloc Technology system.
Assuntos
Ração Animal , Aquicultura , Composição Corporal , Ciclídeos , Animais , Ciclídeos/crescimento & desenvolvimento , Ciclídeos/metabolismo , Aquicultura/métodos , Ração Animal/análise , Dieta/veterinária , Estresse OxidativoRESUMO
The daily variations of temperature are one of the main synchronizers of the circadian rhythms. In addition, water temperature influences the embryonic and larval development of fish and directly affects their metabolic processes. The application of thermocycles to fish larvae has been reported to improve growth and the maturation of the digestive system, but their effects on metabolism are poorly understood. The aim of the present study was to evaluate the effect of two different temperature regimes, cycling versus constant, on the daily rhythms of metabolic factors of Nile tilapia (Oreochromis niloticus) larvae. For this purpose, fertilized eggs were divided into two groups: one reared in a 31 °C:25 °C day:night thermocycle (TCY) and another group maintained in a constant 28 °C temperature (CTE). The photoperiod was set to a 12:12 h light/dark cycle. Samples were collected every 4 h during a 24-h cycle on days 4, 8 and 13 post fertilization (dpf). The expression levels of alanine aminotransferase (alt), aspartate aminotransferase (ast), malic enzyme, glucose-6-phosphate dehydrogenase (g6pd), phosphofructokinase (pfk) and pyruvate kinase (pk) were analyzed by qPCR. Results showed that, in 13 dpf animals, most of the genes analyzed (alt, ast, malic, g6pd and pfk) showed daily rhythms in TCY, but not in the group kept at constant temperature, with most acrophases detected during the feeding period. An increase in nutrient metabolism around feeding time can improve food utilization and thus increase larval performance. Therefore, the use of thermocycles is recommended for tilapia larviculture.
Assuntos
Ciclídeos , Ritmo Circadiano , Temperatura , Animais , Ciclídeos/crescimento & desenvolvimento , Ciclídeos/metabolismo , Ciclídeos/fisiologia , Ciclídeos/genética , Ritmo Circadiano/fisiologia , Larva/crescimento & desenvolvimento , Larva/metabolismo , Fotoperíodo , Glucosefosfato Desidrogenase/metabolismo , Glucosefosfato Desidrogenase/genética , Aspartato Aminotransferases/metabolismo , Alanina Transaminase/metabolismoRESUMO
This study aimed to evaluate the effect of the biofloc technology (BFT) system and the replacement of fish meal with Spirulina biomass on productive performance, intestinal histomorphometry, plasma biochemistry, and oxidative stress of Nile tilapia juveniles (Oreochromis niloticus) fed suboptimal levels of protein. Two factors were evaluated: production systems (clear water × BFT) and replacement of fish meal with Spirulina (0, 33, 66 e 100%). The design was in a 2 × 4 randomized factorial scheme with four replications, and the fish were evaluated for 48 days. Four isoproteic (28% crude protein) diets were formulated with gross energy values close to 4300 kcal kg-1. Nile tilapia juveniles (0.23 ± 0.01 g) were distributed in 16 circular tanks (70 L) at seven fish/tank. The diets were formulated with protein levels approximately 20% below that required for the species and life stage. No interaction was observed between the factors evaluated (production systems × Spirulina inclusion). Rearing the fish in the BFT system avoided the adverse effects of diets with suboptimal protein levels on performance, intestinal histomorphometry, and protein metabolism. Lower values lower lipid peroxidation and higher antioxidant capacity were observed in fish reared in the BFT system, showing evidence of improvements in antioxidant responses and lower levels of physiological oxidative stress. Spirulina completely replaced fish meal in the diets of Nile tilapia juveniles without adverse effects on intestinal morphometry, protein metabolism, and antioxidant response. Replacing 66% of fish meal with Spirulina improved the productive performance, regardless of the rearing system.
Assuntos
Ração Animal , Ciclídeos , Dieta , Intestinos , Spirulina , Animais , Ciclídeos/metabolismo , Ciclídeos/crescimento & desenvolvimento , Ração Animal/análise , Intestinos/efeitos dos fármacos , Dieta/veterinária , Proteínas Alimentares/administração & dosagem , Estresse Oxidativo/efeitos dos fármacos , Fenômenos Fisiológicos da Nutrição Animal , Aquicultura/métodosRESUMO
Spermatogenesis is a finely regulated process that involves the interaction of several cellular mechanisms to ensure the proper development and maturation of germ cells. This study assessed autophagy contribution and its relation to apoptosis in fish spermatogenesis during starvation. To that end, Nile tilapia males were subjected to 0 (control), 7, 14, 21, and 28 days of starvation to induce autophagy. Testes samples were obtained for analyses of spermatogenesis by histology, electron microscopy, immunohistochemistry, and western blotting. Sperm quality was assessed using a computer-assisted sperm analysis (CASA) system. Data indicated a significant reduction in gonadosomatic index, seminiferous tubule area, and spermatozoa proportion in fish subject to starvation compared to the control group. Immunoblotting revealed a reduction of Bcl2 and Beclin 1 associated with increased Bax and Caspase-3, mainly after 21 and 28 days of starvation. LC3 and P62 indicated reduced autophagic flux in these starvation times. Immunolabeling for autophagic and apoptotic proteins occurred in all development stages of the germ cells, but protein expression varied throughout starvation. Beclin 1 and Cathepsin D decreased while Bax and Caspase-3 increased in spermatocytes, spermatids, and spermatozoa after 21 and 28 days. Autophagic and lysosomal proteins colocalization indicated the fusion of autophagosomes with lysosomes and lysosomal degradation in spermatogenic cells. The CASA system indicated reduced sperm motility and velocity in animals subjected to 21 and 28 days of starvation. Altogether, the data support autophagy acting at different spermatogenesis stages in Nile tilapia, with decreased autophagy and increased apoptosis after 21 and 28 days of starvation, which results in a decrease in the spermatozoa number and sperm quality.
Assuntos
Ciclídeos , Masculino , Animais , Caspase 3/metabolismo , Ciclídeos/metabolismo , Proteína Beclina-1/genética , Proteína Beclina-1/metabolismo , Proteína X Associada a bcl-2/metabolismo , Motilidade dos Espermatozoides , Sêmen/metabolismo , Espermatozoides/metabolismo , Espermatogênese , Espermátides , AutofagiaRESUMO
The Nile tilapia (Oreochromis niloticus) is one of the most important cultured fish worldwide, but tilapia culture is largely affected by low temperatures. Recent studies suggest that microRNAs (miRNAs) regulate cold tolerance traits in fish. In general, qPCR-based methods are the simplest and most accurate forms of miRNA quantification. However, qPCR data heavily depends on appropriate normalization. Therefore, the aim of the present study is to determine whether the expression of previously tested, stably expressed miRNAs are affected by acute cold stress in Nile tilapia. For this purpose, one small nuclear RNA (U6) and six candidate reference miRNAs (miR-23a, miR-25-3, Let-7a, miR-103, miR-99-5, and miR-455) were evaluated in four tissues (blood, brain, liver, and gills) under two experimental conditions (acute cold stress and control) in O. niloticus. The stability of the expression of each candidate reference miRNA was analyzed by four independent methods (the delta Ct method, geNorm, NormFinder, and BestKeeper). Further, consensual comprehensive ranking of stability was built with RefFinder. Overall, miR-103 was the most stable reference miRNA in this study, and miR-103 and Let-7a were the best combination of reference targets. Equally important, Let-7a, miR-23a, and miR-25-3 remained consistently stable across different tissues and experimental groups. Considering all variables, U6, miR-99-5, and miR-455 were the least stable candidates under acute cold stress. Most important, suitable reference miRNAs were validated in O. niloticus, facilitating further accurate miRNA quantification in this species.
Assuntos
Ciclídeos , MicroRNAs , Tilápia , Animais , MicroRNAs/genética , MicroRNAs/metabolismo , Ciclídeos/genética , Ciclídeos/metabolismo , Resposta ao Choque Frio , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Tilápia/metabolismo , Perfilação da Expressão Gênica , Padrões de ReferênciaRESUMO
The aim of this study was to evaluate the feeding activity and the rhythm of daily locomotor activity of the convict cichlid (Amatitlania sp.) kept in different social groups under a self-feeding system. A total of 120 animals was distributed among six repetitions of four social groups, as follows: group 1 with one male and one female per tank; group 2 with three males and three females per tank; group 3 with six males per tank; and group 4 with six females per tank. Feeding activity (FA) and locomotor activity (LA) were evaluated using photoelectric presence-sensors connected to automatic feeders. The fish were fed a commercial extruded diet (46% crude protein and 3600 kcal kg-1 of digestible energy). Animal growth was evaluated for all groups. After 30 days of experimentation, the fish stabilized their demands by adjusting their consumption. Amatitlania sp. showed predominantly diurnal FA and LA. All groups showed a peak of activity when the light was turned on and when it was turned off. In summary, FA and LA of Amatitlania sp. are predominantly diurnal and independent of social group. Pairs and groups of males and females together consume less food in relation to groups of one sex or the other due to reproductive behaviour. On the other hand, groups of only males or females consume more food because they lack reproductive stimuli and thus prioritize growth. These results may support good feeding management practices for this ornamental cichlid. Studies relating feeding behaviour with different social groups are of great importance for determining effective feeding strategies for this species in captivity. Thus, such a study assists in a more efficient production of Amatitlania sp.
Assuntos
Ciclídeos , Animais , Feminino , Masculino , Ciclídeos/metabolismo , Ritmo Circadiano , Dieta , Comportamento Alimentar , ReproduçãoRESUMO
The indiscriminate use of pesticides has led to an increased risk of environmental contamination and pest resistance worldwide, favoring the development of less hazardous formulations. The commercial insecticide ZEUS® (Ihara, Brazil) combining dinotefuran and lambda-cyhalothrin was recently formulated in order to meet the environmental sustainability and food security. However, little is known about the potential toxic effects of ZEUS® to aquatic species. Thus, we report, for the first time, the biochemical and histological responses in tilapia (Oreochromis niloticus) following 96 h exposure to 0.01 mg/L, 0.05 mg/L and 0.1 mg/L ZEUS®. Different biochemical endpoints, including acetylcholinesterase (AChE), gamma-glutamyltransferase (GGT) and alkaline phosphatase (ALP), were assessed as potential biomarkers of insecticide effects. Glutathione S-transferase (GST) was evaluated as a marker of phase II biotransformation, and histopathological changes were measured to indicate gill alterations following ZEUS® exposure. After 96 h exposure, ZEUS® treatment increased GST activity in the liver of fish exposed to the highest concentration, while the intermediate dose increased both renal GGT and hepatic ALP activities. These findings reflect the importance of the liver and kidneys in the detoxification of ZEUS® and highlight the need to understand further toxicity effects. Likewise, the histopathological analysis of gills provided evidence that ZEUS® caused moderate damages. Despite biomarkers alterations reported for O. niloticus following ZEUS® exposure, by comparing our findings with data on toxicity of individual compounds, the commercial ZEUS® mixture seems to present similar or even lower adverse effects on freshwater fish.
Assuntos
Ciclídeos , Inseticidas , Poluentes Químicos da Água , Acetilcolinesterase/metabolismo , Fosfatase Alcalina/metabolismo , Animais , Biomarcadores/metabolismo , Ciclídeos/metabolismo , Brânquias/metabolismo , Glutationa Transferase/metabolismo , Guanidinas , Inseticidas/farmacologia , Fígado/metabolismo , Neonicotinoides , Nitrilas , Nitrocompostos , Estresse Oxidativo , Piretrinas , Poluentes Químicos da Água/metabolismo , gama-Glutamiltransferase/metabolismo , gama-Glutamiltransferase/farmacologiaRESUMO
We investigated whether dietary supplementation with Aurantiochytrium sp. meal, a DHA-rich source (docosahexaenoic acid, 22: 6 n-3), fed during long-term exposure to cold-suboptimal temperature (22 °C, P1), followed by short-term exposure to higher temperatures (28 °C, P2, and 33 °C, P3), would promote oxidative damage in Nile tilapia (Oreochromis niloticus). Two supplementation levels were tested: 1.0 g 100 g-1 (D1) and 4.0 g 100 g-1 (D4). A control diet, without the additive (D0, 0 g 100 g-1), and a positive control diet supplemented with cod liver oil (CLO) were also tested. The concentrations of DHA and total n-3 PUFAs in the CLO diet were similar to those found in diets D1 and D4, respectively. The parameters analyzed included hemoglobin (Hb), the antioxidant enzymes catalase, glutathione peroxidase, total glutathione, non-protein thiols, and the oxidative markers protein carbonyl and erythrocyte DNA damage. Nile tilapia did not present differences in Hb content, regardless of diet composition, but the temperature increase (P1 to P2) led to a higher Hb content. Likewise, the temperature increases promoted alterations in all antioxidant enzymes. The dietary supplementation with 1.0 g 100 g-1 Aurantiochytrium sp. meal after P1 caused minor DNA damage in Nile tilapia, demonstrating that the additive can safely be included in winter diets, despite its high DHA concentration.