Paula Brando de Medeiros

We aimed to identify the digestive microbiota of the golden mussel Limnoperna fortunei, and characterize its structure in different seasons. Limnoperna fortunei specimens were sampled in winter (September 2019) and summer (March 2020) in five reservoirs of hydroelectric power plants in southern Brazil. In each reservoir, we sampled 15 individuals at three different points. We collected the digestive diverticulum and portions of the intestine for bacterial DNA extraction, and subsequently conducted metagenomic analysis. The intestinal microbial communities of L. fortunei occurring in the upper Uruguay River region showed significant differences during winter and summer. Although the phyla Proteobacteria, Bacteroidetes, and Cyanobacteria were dominant regardless of the season, the microbial communities showed greater richness and bacterial diversity in the summer. Additionally, we found 143 species of bacteria in the digestive samples collected during both winter and summer, which may indicate a central microbial community for the species. The microbial communities in the digestive tract of L. fortunei showed greater bacterial richness and diversity in summer samples, which existed at a significantly higher temperature than those in winter samples. We observed seasonal variations in the microbiota of L. fortunei in the upper Uruguay River region, with increased bacterial richness and diversity in the digestive tract during summer, attributed to higher temperatures. However, Proteobacteria, Bacteroidetes, and Cyanobacteria consistently dominated the digestive tract of the golden mussel, regardless of seasonal fluctuations.

In this study, we analyzed the hematoimmunological effects of dietary supplementation with immunomodulators (β-glucans + nucleotides) and different levels of vitamins on Nile tilapia (Oreochromis niloticus) after exposure to physical stress. The following four diet treatments were used: diets with indicated vitamin levels (Vitind), diets with Vitind + immunomodulator (Vitind + Immune), diets with high vitamin content (Vithigh), and those with Vithigh + immunomodulator (Vithigh + Immune). The experiment included 560 fish in 28 tanks (20 fish tank-1), with seven replicates per treatment. After 60 days of supplementation, the water temperature was set at 20 °C, and complete biometrics were performed. The animals were then subjected to physical stress with temperature oscillations of 20 °C to 30 °C/30 °C to 20 °C/20 °C to 30 °C. Hematoimmunological data from 140 animals were collected poststress. Antimicrobial titer and total plasma protein levels were significantly higher in fish not receiving immunomodulator-supplemented diets (2.88 ± 0.43 log2 and 26.81 ± 4.01 mg∙mL-1, respectively) than in those that did. Conversely, the agglutination titer increased in fish fed with lower vitamin levels (3.33 ± 0.66 log2) compared to those with higher vitamin levels. Increased immunoglobulin levels were observed in fish fed diets co-supplemented with vitamins and immunomodulators, revealing an interaction between immunomodulators and dietary vitamin levels. In summary, the inclusion of immunomodulators in the diet enhanced the animals’ resistance to physical stress and improved hematoimmunological parameters. Additionally, a high vitamin content in the diet did not modulate the immune responses in the animals. Neste estudo analisamos os efeitos hematoimunológicos da suplementação dietética com imunomoduladores (β-glucanos+nucleotídeos) e diferentes níveis de vitaminas na tilápia do Nilo (Oreochromis niloticus) após exposição ao estresse físico. Foram utilizados quatro tratamentos: dietas com níveis indicados de vitaminas (Vitind), dietas com Vitind + imunomodulador (Vitind+Immune), dietas com alto teor de vitaminas (Vithigh) e dietas com Vithigh + imunomodulador (Vithigh+Immune). O experimento incluiu 560 peixes em 28 tanques (20 peixes tanques-1), com sete repetições por tratamento. Após 60 dias de suplementação, a temperatura da água foi fixada em 20 °C e realizada biometria completa. Os animais foram submetidos a estresse físico com oscilações de temperatura de 20 °C a 30 °C/30 °C a 20 °C/20 °C a 30 °C. Dados hematoimunológicos de 140 animais foram coletados pós-estresse. O título antimicrobiano e os níveis de proteína plasmática total foram significativamente maiores em peixes que não receberam dietas com imunomodulador (2,88±0,43 log2 e 26,81±4,01 mg∙mL-1) do que naqueles que receberam. Por outro lado, o título de aglutinação aumentou em peixes alimentados com níveis mais baixos de vitaminas (3,33±0,66 log2) comparado àqueles com níveis mais elevados. Níveis aumentados de imunoglobulinas foram observados em peixes alimentados com dietas co-suplementadas com vitaminas e imunomoduladores, revelando interação entre imunomoduladores e níveis de vitaminas na dieta. Em resumo, a inclusão de imunomoduladores na dieta aumentou a resistência dos animais ao estresse físico e melhorou os parâmetros hematoimunológicos. Além disso, o alto teor de vitaminas na dieta não modulou as respostas imunológicas dos animais.

This study aimed to evaluate the potential of Lippia sidoides essential oil as a food additive for Cyprinus carpio koi carp in improving the health parameters and resistance to infection by Aeromonas hydrophila. A total of 312 carp were divided into groups. Twenty-four animals were in the lethal dose 50% (LD50) test group. The remaining 288 were distributed in 24 experimental units (n = 12) divided into six treatments-Lippia0.250%, Lippia0.125%, Lippia0.063%, Lippia0.031%, alcohol, and control-with four replicates each. The animals were fed thrice daily with 5% of living biomass for 55 days. At the end of the period, five specimens were collected from each treatment to analyze the intestinal tract's zootechnical performance, hematological analysis, and microbiology. The remaining animals were challenged with A. hydrophila, and the mortality rate was monitored for 100 days. Thymol was the component with the highest concentration (76.6%) in the essential oil of L. sidoides. Fish fed Lippia0.125% had the greatest post-challenge survival. Fish fed Lippia0.063% showed increased zootechnical performance, and those fed Lippia0.250% had the highest concentration of lactic acid bacteria in the intestine. Hematological analyses did not show significant differences among treatments. The authors suggest new studies with higher concentrations of L. sidoides essential oil in the diet of C. carpio than were used in this study.