Aloysia triphylla essential oil as food additive for Rhamdia quelen – Stress and antioxidant parameters

We examined the effects of dietary supplementation for 21 days with different levels (0, 0.25 and 2.0 ml/kg) of the Aloysia triphylla essential oil (EOAT) on silver catfish (Rhamdia quelen). Cortisol levels were lower in fish fed EOAT at 2.0 ml/kg diet, and lactate levels were lower in those fed at both doses. Glucose, alanine aminotransferase, aspartate aminotransferase and triglyceride levels did not vary between groups. The biomarkers of oxidative stress, thiobarbituric acid‐reactive substances, lipid hydroperoxide, superoxide dismutase, catalase and non‐protein thiols, were lower in the brain, liver and muscle of fish fed EOAT at 2.0 ml EO/kg diet. Glutathione‐S‐transferase, reduced glutathione, plasma Na⁺, Cl^?, and K⁺, and gill Na⁺/K⁺‐ATPase and H⁺‐ATPase did not vary between groups. Taken together, our results clearly indicate that the addition of EOAT at 2.0 ml/kg diet improves oxidative status and lowers the stress response in silver catfish.     

Anaesthetic and antioxidant effects of Myrcia sylvatica (G. Mey.) DC. and Curcuma longa L. essential oils on tambaqui (Colossoma macropomum)

Anaesthetic substances are necessary to reduce fish stress during aquaculture activities. The objectives of this study were: (i) to determine the efficacy of essential oils (EOs) of Myrcia sylvatica (EOMS) and Curcuma longa (EOCL) as anaesthetics for Colossoma macropomum and (ii) to evaluate the effects of rapid anaesthesia and long‐term sedation (6 h) with these oils. Therefore, the main primary stress indicator (cortisol) and secondary factors (biochemical indices, hepatic metabolism, oxidative biomarkers) were measured. Sedation with the EOCL resulted in lower cortisol levels compared to control group. Total cholesterol levels were lower in fish sedated with EOMS than in control. Lactate levels were higher in fish anaesthetized with both EOs and sedated with EOCL compared to control. Both EOs increased hepatic glycogen levels after anaesthesia and EOMS increased this parameter after sedation compared to control. Anaesthesia and sedation with EOs resulted in lower levels of lipid peroxidation (LPO) compared to control. In turn, the activity of some antioxidant enzymes evaluated (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione‐S‐transferase), the content of non‐protein thiols and total reactive antioxidant potential were higher in tissues of fish anaesthetized and sedated with EOs compared to control. This induction of antioxidant capacity in the tissues could be due to the antioxidant property exerted by these EOs. Thus, EOMS and EOCL are recommended for anaesthesia and sedation of fish because in spite of inducing anaerobic metabolism, these EOs did not alter most biochemical parameters, reduced the LPO and increased the antioxidant capacity in vital tissues.     

Redox profile in liver of Leporinus macrocephalus exposed to different dissolved oxygen levels

Aquatic organisms are continuously exposed to environmental variations, which can lead to physiological and biochemical alterations. Leporinus macrocephalus, known as piavu?u, is a migratory species that may be exposed to variations in dissolved oxygen levels. Studies evaluating oxidative changes undergone by this species in these conditions are scarce. Therefore, this investigation aimed at evaluating oxidative alterations in L. macrocephalus exposed to different oxygen levels for 96?h: 6.12?±?0.18, 3.99?±?0.17, 3.22?±?0.17, 2.47?±?0.30 and 0.710?±?0.07?mg?L(-1). At the end of the experimental period, fish were euthanized and livers used to determine lipid hydroperoxides, thiobarbituric acid reactive substances, catalase, glutathione-S-transferase, superoxide dismutase and thiol groups, which are an indirect measure of reduced glutathione. Results indicated a decrease in the studied parameters in hypoxic situations, suggesting a possible metabolic depression.     

Silver catfish Rhamdia quelen immersion anaesthesia with essential oil of Aloysia triphylla (L'Hérit) Britton or tricaine methanesulfonate: effect on stress response and antioxidant status

Responses to anaesthesia with essential oil (EO) of Aloysia triphylla (135 and 180 mg L^?1) and tricaine methanesulfonate (MS222) (150 and 300 mg L^?1) were assessed in silver catfish. Exposure to the anaesthetics elicited a stress response in the species. In the case of MS222, it was displayed as a release of cortisol into bloodstream, elevation in hematocrit and plasma ion loss. The EO presented cortisol‐blocking properties, but increased haematocrit and disturbances of hydromineral balance were observed. Liver antioxidant/oxidant status of EO and MS222‐anaesthetized silver catfish was also estimated. The synthetic anaesthetic induced lipoperoxidation, notwithstanding increased catalase contents, whereas the naturally occurring product was capable of preventing the formation of lipid peroxides, possibly due to combined actions of catalase and glutathione‐S‐transferase. Anaesthetic efficacy was also tested via induction and recovery times. Overall, the promising results obtained for the physiological parameters of the EO‐treated fish counterbalanced the slight prolonged induction time observed for 180 mg L^?1. As for 135 mg L^?1, both induction and recovery times were lengthy; despite that, the EO was able to promote oxidative protection and mitigate stress. None of the MS222 concentrations prompted such responses concomitantly.     

Citrus x aurantium essential oil as feed additive improved growth performance,survival, metabolic,and oxidative parameters of silver catfish (Rhamdia quelen)

The effects of dietary supplementation of graded level (0, 0.25, 0.5, 1.0, and 2.0 ml/kg diet) of Citrus aurantium essential oil (EOCA) on the growth, metabolic, and oxidative parameters of silver catfish (Rhamdia quelen) were investigated in a 60‐day growth trial. Fish fed with 2.0 ml EOCA per kg exhibited significantly better growth performance than those fed the control diet. Glucose, lactate, and protein levels in liver and muscle were altered significantly by dietary addition of EOCA. Hepatic lipid peroxidation levels, measured using thiobarbituric acid reactive substance and lipid hydroperoxides assays, were reduced in animals receiving the diet containing EOCA. Superoxide dismutase activity was higher, while glutathione S‐transferase activity was lower in the liver of fish receiving 0.5, 1.0, and 2.0 ml EOCA per kg of diet than in control. The nonprotein thiols content was higher in fish receiving the EOCA‐containing diet. Thus, dietary addition of EOCA improved growth, biochemical, and antioxidant parameters in silver catfish and could be useful as dietary supplement.     

Oxidative and biochemical responses in Brycon amazonicus anesthetized and sedated with Myrcia sylvatica (G. Mey.) DC. and Curcuma longa L. essential oils

Objective

To investigate the effects of rapid anesthesia and long-term sedation with the essential oils (EOs) of Myrcia sylvatica (EOMS) and Curcuma longa (EOCL) on biochemical and oxidative parameters in matrinxã.

Genetic variability of soybean bradyrhizobia populations under different soil managements

Due to their ecologic and economic importance, bradyrhizobia have been extensively studied in recent years. Since 1992, Bradyrhizobium elkanii SEMIA 587 and SEMIA 5019 and Bradyrhizobium japonicum SEMIA 5079 and SEMIA 5080 have been widely used in most Brazilian soybean fields. The objective of this work was to estimate the genetic variability of bradyrhizobial isolates recovered from soils under rhizobial inoculation and different soil managements. Only 25% of the isolates demonstrated high similarities to the original strains, and a strong correlation was obtained between the bradyrhizobial genetic variability and soil management. A high level of genetic diversity was observed both within isolates (H = 5.46) as well as among the different soil practices. Soil under no-tillage presented a higher bradyrhizobia diversity compared with bradyrhizobia isolated from soil under conventional tillage. Serological characterization also indicated that B. elkanii strains SEMIA 587 and SEMIA 5019 were more competitive and presented a higher nodular occupancy capacity than strains belonging to B. japonicum species in Southern Brazilian soils.     

Morphological traits of stem to indirect selection of resistance to lodging in Avena sativa L

Journal of Crop Science and Biotechnology - The runout of newly cultivated areas in the world without recurring to the deforestation, demand a necessity to improve yield to sustain a growth...     

Myrcia sylvatica essential oil in the diet of gilthead sea bream (Sparus aurata L.) attenuates the stress response induced by high stocking density

The effects of diet supplemented with Myrcia sylvatica essential oil (EOMS) on growth and stress tolerance to different stocking densities were assessed in Sparus aurata. Initially, three experimental groups were established: (i) control, (ii) 1.0 and (iii) 2.0 ml EOMS/kg dry feed. After 90 days, nine fish per group were anaesthetized, weighed and sampled for metabolic analysis. The remaining fish were divided into two different conditions: low (LD—5 kg/m³) and high (HD—40 kg/m³) stocking densities, constituting a final experimental setup with six treatments. After 22 days, 10 individuals per treatment were anaesthetized and sampled for biochemical analysis. EOMS feeding for 90 days did not interfere with growth, although it was effective in reducing cortisol levels and the activation of lipid and carbohydrate metabolism. The HD interfered in growth performance, increased the lactate levels in the control group, reducing also hepatic glycogen levels without dependence on diet supplementation. The 2.0 ml EOMS + LD group increased the growth parameters and decreased the cortisol and triglycerides levels. Additionally, metabolism adjustment was observed to provide energy during LD and HD conditions, indicating that diets supplemented with EOMS produce metabolic reorganization to maintain body homeostasis, suggesting its use as a beneficial supplement in fish.     

Histological and antioxidant responses in Rhamdia quelen sedated with propofol

Morphometry of gills and antioxidant/oxidant status in gills, brain, liver and blood of Rhamdia quelen sedated with propofol were studied. The purpose was to investigate structural and functional responses upon administration of the drug in order to validate its use for the species. The fish were exposed to 0, 0.4 or 0.8 mg L^?1 propofol for 1, 6 or 12 h, which are times normally used in live fish transport. Propofol induced an increase in chloride cell in the non‐respiratory epithelium of the gill. Standard biochemical assays (thiobarbituric acid reactive substances and lipid hydroperoxides) indicated that the lowest concentration of propofol did not induce lipoperoxidation in gills, brain, liver or blood. The oxidative status of enzymatic (catalase, superoxide dismutase and glutathione‐S‐transferase) and non‐enzymatic (non‐protein thiols) antioxidants differed among the tested sites. Apart from the blood, superoxide dismutase was the enzyme to show the highest activity in the presence of propofol, which is known to possess antioxidant properties that resemble those of vitamin E. The absence of chloride cells in the respiratory epithelium (lamella) in association with the stability of the lamellar structure (i.e. lamellar area, total height of lamella and width of lamella) indicate that ion and oxygen uptake were preserved under propofol sedation. Thus, 0.4 mg L^?1 propofol should be considered to sedate R. quelen during lengthy procedures, such as transport, for it was able to maintain ionic and respiratory homeostasis as well as prevent peroxidative damage in vital organs.