A systematic review of invasive non-native freshwater bivalves.

The introduction of invasive species has become an increasing environmental problem in freshwater ecosystems due to the high economic and ecological impacts it has generated. This systematic review covers publications from 2010 to 2020, focusing on non-native invasive freshwater bivalves, a particularly relevant and widespread introduced taxonomic group in fresh waters. We collected information on the most studied species, the main objectives of the studies, their geographical location, study duration, and type of research. Furthermore, we focused on assessing the levels of ecological evidence presented, the type of interactions of non-native bivalves with other organisms and the classification of their impacts. A total of 397 publications were retrieved. The studies addressed a total of 17 species of non-native freshwater bivalves; however, most publications focused on the species Corbicula fluminea and Dreissena polymorpha, which are recognised for their widespread distribution and extensive negative impacts. Many other non-native invasive bivalve species have been poorly studied. A high geographical bias was also present, with a considerable lack of studies in developing countries. The most frequent studies had shorter temporal periods, smaller spatial extents, and more observational data, were field-based, and usually evaluated possible ecological impacts at the individual and population levels. There were 94 publications documenting discernible impacts according to the Environmental Impact Classification for Alien Taxa (EICAT). However, 41 of these publications did not provide sufficient data to determine an impact. The most common effects of invasive bivalves on ecosystems were structural alterations, and chemical and physical changes, which are anticipated due to their role as ecosystem engineers. Despite a considerable number of studies in the field and advances in our understanding of some species over the past decade, long-term data and large-scale studies are still needed to understand better the impacts, particularly at the community and ecosystem levels and in less-studied geographic regions. The widespread distribution of several non-native freshwater bivalves, their ongoing introductions, and high ecological and economic impacts demand continued research. Systematic reviews such as this are essential for identifying knowledge gaps and guiding future research to enable a more complete understanding of the ecological implications of invasive bivalves, and the development of effective management strategies.

Physiological strategies of acute thermal conditions of Rhamdia voulezi collected in the Iguaçu river watershed, Paraná, Brazil: biochemical markers of metabolic and oxidative stress.

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.

Metabolic responses in the gills of Yellowtail Lambari Astyanax lacustris under low- and high-temperature thermal stress.

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.

Integrated biomarker response index as an ally in the observation of metabolic biomarkers in muscle of Astyanax lacustris exposed to thermal variation.

Temperature is an important factor that conditions the physiological responses of fish, generating a stressful condition when in non-ideal parameters. Thus, the objective was to evaluate metabolic aspects in the muscle of fish Astyanax lacustris submitted to thermal shock. The specimens were subjected to 2, 6, 12, 24, 48, and 96 h of exposure to 15 °C and 31 1 °C, with their respective controls 23 °C. At 15 °C there was a reduction in glycogenolysis in the initial periods indicated by changes in glycogen phosphorylase (GP), pyruvate and lactate. Subsequently, there was an increase in GP activity, pyruvate levels and hexokinase activity in the next time periods, suggesting an increase in energy demand. At 31 °C there was observed low need for the protein metabolism, indicated by reduction in the activity of aspartate aminotransferase and alanine aminotransferase. At 15 °C, initial periods show an increase in glutathione reductase activity and an increase in carbonylated protein levels, indicating induction of oxidative stress for muscle. At 31 °C, there was a punctual increase in reduced glutathione levels at 24 h. In addition, the integrated biomarker response index proved to be a good ally in the evaluation of a set of biomarkers, corroborating the results observed by the biomarkers individually. Thus, it is possible to conclude that the acute thermal shock affects the metabolism of A. lacustris muscle, which undergoes rearrangements to deal with temperature, where 15 °C is more stressful than 31 °C.

Cold and warm waters: energy metabolism and antioxidant defenses of the freshwater fish Astyanax lacustris (Characiformes: Characidae) under thermal stress.

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.

Biomarkers of oxidative stress and cell damage in freshwater bivalves Diplodon parodizi exposed to landfill leachate.

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.