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Thermal pollution creates substantial challenges that alter energy demand and produce reactive oxygen species that damage fish DNA, proteins, and lipids. Rhamdia voulezi is a species of fish native to the Iguaçu river, Paraná, Brazil, that does not have scientific records of minimum (CTmin) and maximum (CTmax) temperatures required for survival. As it is a top predator species in the food chain and lives at temperatures below 22 °C, the loss of the species can cause functional problems in controlling the ecosystem and energy flow. The study evaluated the tissue metabolism of the brain, heart, and muscle of R. voulezi (n = 72) subjected to acute thermal stress of 31 °C for 2, 6, 12, 24, and 96 h after acclimatization to 21 °C. The biochemical markers SOD, GPx, MDH, HK, and CK of the brain, PCO of the heart and CAT, glycogen, G6PDH, and ALT of muscle were significant. PCA, IBR, thermal sensitive, and condition factor suggested that R. voulezi has different physiological strategies for acclimatization to 31 °C to mobilize and sustain the metabolic needs of oxygenation and energy allocation/utilization for tissue ATP production. [ABSTRACT FROM AUTHOR]

Exposure to high temperatures induces changes in fish respiration, resulting in an increased production of reactive oxygen species. This, in turn, affects the enzymatic and non-enzymatic components of antioxidant defenses, which are essential for mitigating cellular stress. Rhamdia voulezi, an economically important fish species endemic to Brazil's Iguaçu River, served as the subject of our study. Our goal was to assess enzymatic antioxidant biomarkers (superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase, glucose-6-phosphate dehydrogenase), non-protein thiol levels (reduced glutathione), and markers of oxidative damage (lipoperoxidation and carbonylation) in the liver, gills, and kidneys of R. voulezi after acute exposure to high temperatures (31°C) for 2, 6, 12, 24, and 96 h. Control groups were maintained at 21°C. Our findings revealed that the liver exhibited increased superoxide dismutase levels up to 12 h and elevated glutathione S-transferase levels at 12 and 96 h at 31°C. In the gills, superoxide dismutase levels increased up to 24 h, along with increased lipoperoxidation at 2, 6, 12, and 96 h of exposure to high temperatures. The kidneys responded to heat stress at 12 h, with an increase in superoxide dismutase and catalase activity, and lipid peroxidation was observed at 2 and 6 h at 31°C. The three tissues evaluated responded differently to heat stress, with the liver demonstrating greater physiological adjustment to high temperatures. The intricate interplay of various antioxidant defense biomarkers and oxidative damage suggests the presence of oxidative stress in R. voulezi when exposed to high temperatures. [ABSTRACT FROM AUTHOR]

Objective: Ectothermic fish are directly affected by temperature changes in the environment. The aim of this study was to evaluate the metabolic responses in the gills of Yellowtail Lambari Astyanax lacustris under thermal stress. Methods: To this end, we used spectrophotometry to evaluate the biomarkers of carbohydrate and protein metabolism, antioxidant defense, and oxidative damage in fish subjected to low (15°C) and high (31°C) temperatures, with control groups held at 23°C, for 2, 6, 12, 24, 48, and 96 h. Result: The results showed that cold thermal stress did not change the energy demand, and the antioxidant defense was reduced; therefore, the gills were vulnerable to the action of reactive oxygen species (ROS), presenting increased protein carbonylation at 12 h. With heat thermal stress, a higher energy demand was observed, which was verified by an increase in aerobic metabolism by glycolysis and the citric acid cycle. High‐temperature stress also increased the antioxidant defenses, as verified by the increased activities of glutathione peroxidase, glutathione reductase, and glutathione S‐transferase. However, the antioxidant defense system could not protect tissues from the action of ROS, as protein carbonylation increased at 6 and 24 h, indicating oxidative stress. Conclusion: The results showed that (1) temperature variations caused metabolic adjustments in the gills of Yellowtail Lambari, (2) the adaptive responses were different for winter and summer temperatures, and (3) Yellowtail Lambari recovered homeostasis when subjected to thermal stress, even with the occurrence of oxidative stress. Impact statementThis study explores cellular stress responses in terms of metabolism, providing a comparison between low and high temperatures within an evolutionary and environmental context. These findings are crucial for fish farming and conservation efforts, revealing possible impacts of global climate change. [ABSTRACT FROM AUTHOR]

Multibiomarker studies are useful to evaluate the early warning signs of environmental degradation, and their unified responses are often assessed through two common indexes, Integrated Biomarker Response (IBR) and Integrated Biological Responses version 2 (IBRv2). The R package IBRtools allows users to calculate both IBR and IBRv2 while simultaneously incorporating all the biomarkers under evaluation. The package includes functions for calculating the indexes IBR and IBRv2 and obtaining their standardized values, as well a function for radar chart creation and three example datasets. Here we describe the main algorithms involved in IBR and IBRv2 calculations, a description of the novel package and illustrate a workflow using data examples available on the package to guide the user on how to accurately acquire the values for either the IBR index or the IBRv2 index. The IBRtools package provides a user‐friendly platform for R users to obtain IBR index and IBRv2 values, making it straightforward even for large datasets. [ABSTRACT FROM AUTHOR]

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Subtropical fish are exposed to seasonal variations in temperature that impose a set of adaptations on their metabolism necessary for the maintenance of homeostasis. In this study, we addressed the effects of temperature variation on the metabolism of Astyanax lacustris, a species of freshwater fish common in the subtropical region of Brazil. Biomarkers of carbohydrate and protein metabolism, antioxidant defense, and oxidative damage were evaluated in the liver of A. lacustris exposed to low (15 °C) and high (31 °C) temperature thermal shock, with controls at 23 °C for 2, 6, 12, 24, 48, 72, and 96 h. A high energy demand was observed during the first 48 h of exposure to 15 °C, which is necessary for metabolic adjustment at low temperatures, with an increase in glycolysis, citric acid cycle, and amino acid catabolism. In addition, at 31 °C, glucose was exported in the first 12 h of exposure, and an increase in the citric acid cycle suggested acetyl-CoA as the pathway substrate, originating from the oxidation of lipids. The antioxidant defenses did not change at 15 °C, as opposed to 31 °C, in which there were changes in several antioxidant defense markers, indicating a response to the production of ROS. However, oxidative stress was observed at both temperatures, with oxidative damage detected by lipid peroxidation at 15 °C and protein carbonylation at 31 °C. [ABSTRACT FROM AUTHOR]

Demersal shrimp trawling is among the least selective fishing methods, posing a considerable threat to marine ecosystems due to the catch of nontarget species (bycatch). Even when bycatch is immediately released, physical damage to organisms may reduce their survival. The probability of long-term survival and oxidative stress markers of two species of Sciaenidae fish, Paralonchurus brasiliensis and Stellifer rastrifer, caught incidentally while trawling for shrimp in the State of Paraná—Brazil, were analyzed. The mortality rate for both species was found to be high (P. brasiliensis, 76.94%, n = 337 and S. rastrifer, 69.32%, n = 2.586). Among other factors, mortality was associated with body size and the physical damage suffered. Smaller fish showed a higher incidence of damage, most commonly scale-loss and contusions or haematomas on the head and body. The mortality rate and catch damage index (CDI) were similar for both species, but were aggravated by higher tow durations (15, 30, and 45 min). The CDI can be a good predictor of mortality. The probability of survival improved in winter for both species. Increased lipid peroxidation and protein carbonylation were identified in P. brasiliensis but not in S. rastrifer. This indicates that the two species responded in different ways to the stressful conditions produced by trawling. Considering the oxidative stress markers identified, it appears that the high mortality rate recorded in two species was more closely associated with physical damage than oxidative stress markers. [ABSTRACT FROM AUTHOR]

Landfill is a public and environmental health problem; establishing and understanding methodologies to decrease its toxicity are thus necessary. Leachate samples were collected, at a sanitary landfill, immediately after the exit from the landfill, i.e. raw leachate (collection point A), after conventional treatment (point B) and after treatment by wetlands (point C). D. parodizi specimens were exposed to 3%, 10% and control (0%) dilutions of leachate from these collection points for 7 days. Markers of antioxidant defences and cell damage were analysed. At point B, the gills of D. parodizi showed higher glutathione-S-transferase (GST) and glutathione reductase (GR) activity; the latter is a supplier of glutathione reductase (GSH). The low GST activity at point A was associated with the hormesis effect. Higher levels of superoxide dismutase (SOD), ethoxyresorufin-O-deethylase (EROD) and glutathione peroxidase (GPx) occurred at point A. Glucose-6-phosphate dehydrogenase (G6PDH) was inhibited at the points with the highest pollutant load and at the highest leachate dilutions. Higher levels of markers at point A may be related to the high pollutant charge and specific compounds present in the untreated leachate. The multi-xenobiotic resistance mechanism (MXR), metallothionein-like proteins (MT) and lipid peroxidation (LPO) did not vary among treatments. The biomarker responses showed negative effects of the leachate on the freshwater bivalve and simultaneously showed that the wetland treatment employed at the Caximba sanitary landfill is effective. [ABSTRACT FROM AUTHOR]