Amazon fish are vulnerable to climate change. Current temperature increases in Amazonian rivers are likely to continue in the coming years. Elevated temperatures impair homeostasis and subject fish to oxidative stress; nevertheless, the effects of elevated temperature on plasma and muscle oxidative stress as well as fillet fatty acid composition in matrinxã (Brycon amazonicus) remain unknown. Therefore, the aims of the present study were to determine whether antioxidant system is able to withstand acute thermal stress to avoid plasma and muscle oxidative damage and to determine the manner in which matrinxã adjust their muscle fatty acid metabolism in a response to acute heat stress. We exposed juvenile matrinxã to four temperatures (28 °C as control and 30, 32, and 34 °C) for 72 h and observed the effects on plasma and muscle oxidant/antioxidant status and on fatty acid composition. Plasma reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in matrinxã exposed to 34 °C compared with the control group, while they were significantly higher in the muscle of matrinxã exposed to 32 °C and 34 °C compared with the control group. Superoxide dismutase (SOD) activity and total antioxidant capacity (TAC) levels were significantly lower in the plasma and muscle of matrinxã exposed to 34 °C compared with the control group. Plasma glutathione peroxidase (GPx) activity was significantly lower in matrinxã exposed to 32 and 34 °C compared with the control group, while it was significantly lower in the muscle of matrinxã exposed to 34 °C. The total content of saturated fatty acid (SFA) was significantly higher in the fillet of matrinxã exposed to 34 °C compared with the control group, while the total content of polyunsaturated fatty acid (PUFA) was significantly lower. Based on this evidence, we conclude that acute heat stress at 32 °C and 34 °C causes plasma and muscular oxidative stress, and the enzymatic and non-enzymatic antioxidant system is unable to prevent oxidative damage. Moreover, increased levels of total SFA and decreased levels of PUFA occur in an attempt to withstand heat stress and maintain membrane fluidity; nevertheless, these responses can represent negative impacts for consumers.

亚马逊河鱼类易受气候变化的影响。未来几年，亚马逊河流域目前的温度升高可能会继续。温度升高会破坏体内平衡​​，使鱼类遭受氧化应激；然而，高温对matrinxã（Brycon amazonicus）血浆和肌肉氧化应激以及鱼片脂肪酸组成的影响）仍然未知。因此，本研究的目的是确定抗氧化剂系统是否能够承受急性热应激以避免血浆和肌肉氧化损伤，并确定Matrinxã在响应急性热应激时调节其肌肉脂肪酸代谢的方式。我们将青少年Matrinxã暴露于四个温度下（对照为28°C，分别为30、32和34°C）72小时，并观察了其对血浆和肌肉氧化/抗氧化状态以及脂肪酸组成的影响。Matrinxã暴露于34°C的血浆中的活性氧（ROS）和脂质过氧化（LPO）水平与对照组相比显着升高，而Matrinxã暴露于32°C和34°C的肌肉中的血浆中活性氧含量（ROS）和脂质过氧化与对照组。与对照组相比，暴露于34°C的Matrinxã的血浆和肌肉中的超氧化物歧化酶（SOD）活性和总抗氧化能力（TAC）水平显着降低。与对照组相比，暴露于32和34°C的Matrinxã血浆血浆谷胱甘肽过氧化物酶（GPx）活性明显低于对照组，而暴露于34°C的Matrinxã肌肉中血浆谷胱甘肽过氧化物酶（GPx）活性则显着降低。与对照组相比，暴露于34°C的Matrinxã的鱼片中饱和脂肪酸（SFA）的总含量明显高于对照组，而多不饱和脂肪酸（PUFA）的总含量则明显较低。基于此证据，我们得出结论，在32°C和34°C的急性热应激会引起血浆和肌肉的氧化应激，而酶促和非酶促抗氧化剂体系无法防止氧化损伤。此外，总SFA含量增加和PUFA含量降低是为了承受热应力并保持膜的流动性。但是，这些响应可能会对消费者产生负面影响。