Discus (Symphysodon spp.) is among the most popular ornamental fish for warm-water and species that tolerates low temperature should be preferred by discus farmers due to costs in heating aquaria. Here, we compared the antioxidant responses and oxidative stress to decreased temperatures in gills of two discus species (S. haraldi and S. aequifasciatus), by employing a continuous temperature change program, i.e., cooling (28 °C to 14 °C; −1 °C/h), cold maintenance (14 °C for 12 h) and recovery (14 °C to 28 °C; +1 °C/h). Heatmap showed distinct activities or levels of oxidative stress biomarkers in response to thermal stress between two discus species. Except for reduced glutathione content, indicators regarding antioxidant enzymatic activities (e.g., superoxide dismutase, glutathione reductase and glutathione peroxidase) and lipid peroxidation level were generally higher in S. aequifasciatus than in S. haraldi. Subordinate function analysis integrating oxidative stress biomarkers suggested that the thermal resistance of S. haraldi was in the order of cooling > cold maintenance ≈ recovery, but that of S. aequifasciatus was in the order of cold maintenance > cooling > recovery. Specifically, the lowest thermal resistance was observed in S. aequifasciatus during cold recovery, potentially indicating a more severe oxidative damage in terms of lipid peroxidation in S. aequifasciatus than in S. haraldi. These results suggest that S. haraldi had a stronger thermal resistance than S. aequifasciatus, exhibiting a significant interspecific variability under acute thermal stress.

铁饼（Symphysodon spp。）是最受欢迎的温水观赏鱼之一，由于加热水族箱的成本，铁饼养殖者应首选可耐受低温的鱼类。在这里，我们比较了两种铁饼（S. haraldi和S. aequifasciatus）g的抗氧化反应和氧化应激与温度降低的关系。），采用连续的温度变化程序，即冷却（28°C至14°C； -1°C / h），冷维护（14°C持续12 h）和恢复（14°C至28°C） ; +1°C / h）。热图显示了响应于两个铁饼物种之间的热应激而产生的氧化应激生物标志物的不同活性或水平。除了还原型谷胱甘肽含量，指标关于抗氧化酶活性（例如，超氧化物歧化酶，谷胱甘肽还原酶和谷胱甘肽过氧化物酶）和脂质过氧化水平普遍较高S.神仙比S. haraldi。结合氧化应激生物标志物的从属函数分析表明，哈拉迪链霉菌的热阻依次为冷却>低温维持≈恢复，但水母链球菌按冷维护>冷却>恢复的顺序排列。具体地，在观察到最低的热阻S.神仙冷恢复期间，潜在地表明在脂质过氧化作用方面具有更严重的氧化性损伤S.神仙比在S. haraldi。这些结果表明，S. haraldi具有比更强的热阻S.神仙，急性热应力下表现出显著种间的变异性。