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Predictions about global warming have raised interest in assessing whether ectothermic organisms will be able to adapt to these changes. Understanding the physiological mechanisms and metabolic adjustment capacity of fish subjected to heat stress can provide subsidies that may contribute to decision-making in relation to ecosystems and organisms subjected to global climate change. This study investigated the antioxidant defence system and energy metabolism of carbohydrate and protein responses in the gill, liver and kidney tissues of Psalidodon bifasciatus (Garavello & Sampaio 2010), a Brazilian freshwater fish used in aquaculture and in biological studies, following exposure to heat shock at 31 C for 2, 6, 12, 24 and 48 h. The fish pres-

The diversity of soils and climate in Brazil imposes the need to evaluate the adaptation of fodder species to soil and climate conditions to guide producers and technicians in choosing the best alternatives for their region. The objective of this study was to evaluate and identify fodder cultivars for pasture and soil cover with tolerance to drought and high production in the sandy soils of southern Bahia, Brazil. The performance of 29 commercial cultivars of perennial and annual tropical forage species was evaluated in six cuts in 2019 and 2020. The green and dry mass yield per cut and the daily dry matter accumulation rate were evaluated considering the periods of water surplus and deficit and the drought tolerance index for each cultivar was estimated. Grass and legume cultivars showed differences in establishment, yield in the water surplus, and in the re-establishment after the water deficit. Based on the values of the drought tolerance index and in the dry mass daily yields before and after the water deficit, the cultivars adapted and indicated for regional continuous grazing were Xaraés, Marandu, Massai, Tanzânia, Paiaguás, and Zuri, in that order. The grasses B. ruziziensis and B. decumbens were indicated for use as cover plants after the harvest due to their high capacity of establishment and short-term production. The annual and perennial legume plants were also indicated for cover, and the combination of cultivars and their potential for straw in direct planting or use in integrated systems still need to be validated.

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Human activities, such as urbanization, can cause instability in the aquatic biota. This instability can modify aquatic food resource availability, consequently shifting the diet composition of fish. Because the diet consumed by fish closely affects the anatomy of their digestive tract, it can also alter their intestinal coefficient. In this study, we analyzed the diet composition, condition factor and intestinal coefficient of Astyanax lineatus (Perugia, 1891) from two distinct habitats: a "degraded habitat" (Cabaça stream) in a reserve inside the city perimeter and a "preserved habitat" (Salobra River) in Mato Grosso do Sul State, Central Brazil. We found a total of 15 food items, all of which were found in the urban stream, with a predominance of detritus and Chironomidae larvae, and six in the natural area, with a predominance of plant remains. There was a distinct difference in diet composition between fishes in the two areas (p < 0.05, PERMANOVA); however, there was no significant difference in inter-individual variability. The most frequent food items were detritus in the "degraded habitat", while in the "preserved habitat" plant and insect remains were most frequent. The relative condition factor measured by the fish's length-weight relationship was not significantly different between the two habitats. The intestinal coefficient was significantly different between the individuals from each habitat, and it was longer in fish from the natural habitat. Therefore, even though A. lineatus is known to be a generalist species, its feeding plasticity depends on the ecological integrity of the two types of habitats.