Zhang Yuexing, Qiao Hui, Peng Leyang, Meng Yujie, Song Guili, Luo Cheng, Long Yong
National Engineering Research Center for Marine Aquaculture, Marine Science and Technology College, Zhejiang Ocean University, Zhoushan 316022, China.
State Key Laboratory of Breeding Biotechnology and Sustainable Aquaculture, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Antioxidants (Basel). 2025 Apr 20;14(4):495. doi: 10.3390/antiox14040495.
Hyperthermia and nitrogenous pollutants like ammonia and nitrite are common risk factors that adversely affect fish health and pose significant threats to the aquaculture industry. However, the impacts of high temperatures on the accumulation of nitrogenous pollutants in the water of the aquaculture systems and their toxicity to farmed fish are not well understood. In this study, juvenile largemouth bass (, LMB) were kept at 28 °C and 34 °C in a closed aquatic system to investigate the effects of higher temperatures on ammonia and nitrite accumulation. The fish were fed 2% of their body weight daily for a 14-day experiment. Ammonia levels gradually increased, peaking on day 7 at 34 °C and on day 9 at 28 °C, then decreased to near zero. Nitrite levels remained low initially and increased rapidly along with the reduction in ammonia levels at both temperatures. The 34 °C high temperature accelerated the accumulation of ammonia and its transformation into nitrite compared to 28 °C. Fish were sampled on day 1 (low ammonia and low nitrite, LALN), day 8 (high ammonia and low nitrite, HALN), and day 14 (low ammonia and high nitrite, LAHN) to explore toxic effects. Successive exposure to high levels of ammonia and nitrite caused oxidative stress in the liver and significant pathogenic changes in the liver and spleen, with more pronounced impacts observed at 34 °C. Significant changes in gene expression were detected in the liver and spleen of fish sampled at HALN and LAHN, compared to those at LALN, with upregulated genes primarily associated with extracellular matrix (ECM) and cytoskeleton organization. A second experiment was conducted at the same temperatures but without ammonia/nitrite accumulation. The results of this experiment confirmed the combined effects of hyperthermia and ammonia/nitrite toxicity on the expression of genes involved in ECM-receptor interaction and TGF-beta signaling. These findings are valuable for optimizing cultivation environments and promoting the health of farmed LMB.
高温以及氨和亚硝酸盐等含氮污染物是常见的风险因素，会对鱼类健康产生不利影响，并对水产养殖业构成重大威胁。然而，高温对水产养殖系统水体中含氮污染物积累及其对养殖鱼类毒性的影响尚未得到充分了解。在本研究中，将大口黑鲈幼鱼置于封闭的水生系统中，分别在28℃和34℃下饲养，以研究较高温度对氨和亚硝酸盐积累的影响。在为期14天的实验中，每天给鱼投喂其体重2%的饲料。氨水平逐渐升高，在34℃时于第7天达到峰值，在28℃时于第9天达到峰值，然后降至接近零。亚硝酸盐水平最初保持较低，并在两种温度下随着氨水平的降低而迅速升高。与28℃相比，34℃的高温加速了氨的积累及其向亚硝酸盐的转化。在第1天（低氨和低亚硝酸盐，LALN）、第8天（高氨和低亚硝酸盐，HALN）和第14天（低氨和高亚硝酸盐，LAHN）对鱼进行采样，以探究毒性作用。连续暴露于高水平的氨和亚硝酸盐会导致肝脏氧化应激以及肝脏和脾脏发生显著的病理变化，在34℃时观察到的影响更为明显。与LALN组相比，在HALN和LAHN组采样的鱼的肝脏和脾脏中检测到基因表达的显著变化，上调的基因主要与细胞外基质（ECM）和细胞骨架组织有关。在相同温度下进行了第二个实验，但没有氨/亚硝酸盐积累。该实验结果证实了高温与氨/亚硝酸盐毒性对参与ECM-受体相互作用和TGF-β信号传导的基因表达的联合作用。这些发现对于优化养殖环境和促进养殖大口黑鲈的健康具有重要价值。
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