Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China; Bangladesh Fisheries Research Institute, Mymensingh, Bangladesh.
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Ecotoxicol Environ Saf. 2024 Oct 1;284:116827. doi: 10.1016/j.ecoenv.2024.116827. Epub 2024 Aug 22.
Elevated ammonia levels in aquaculture systems could reduce fish growth and survival rates and produce a range of physiological problems. Ammonia toxicity in aquatic environments was regulated by various factors. Feeding was usually reported to help in the detoxification of fish, thereby increasing their capacity to tolerate ammonia nitrogen. However, the impact of different feeding amounts on fish in relation to ammonia exposure stress remains to be determined. To determine how feeding levels affected fish's responses to different ammonia nitrogen concentrations, two acute toxicity experiments were conducted with Carassius auratus gibelio, the major strain of gibel carp in aquaculture systems in China. In Test I, fed Carassius auratus gibelio (3 % body weight) showed a higher survival rate under a specific ammonia exposure stress. 96-h LC of NH-N to 3 %F gibel carp was 1.1 times greater than that for NF (no feeding). In Test II, all fed groups (2 %F and 4 %F) under low and high ammonia stress exhibited improved ammonia detoxification, evidenced by higher liver GSase, GDH, and glutamine concentrations compared with the NF treatment. Muscle glycogen levels in feeding treatments were higher than those in NF, indicating that fed fish have more energy for ammonia detoxification. While compared with low ammonia treatment (2.70 mg L TAN; NH 0.06 mg L), fish exposed to high ammonia levels (26.03 mg L TAN; NH 0.57 mg L) demonstrated a decrease in food consumption, severe histopathological alterations in their liver, gill, and kidney, and decreased GSase, GDH, and glutamine production in the liver and brain. The results partly supported our hypothesis and suggested that increasing feeding enhances gibel carp's tolerance to ammonia nitrogen. The highest detoxification metabolism was observed under low ammonia stress. While excessive ammonia exposure could inhibit feeding and damage the detoxification organs of fish, and thus reduce the detoxification metabolism of gibel carp.
水产养殖系统中氨水平升高会降低鱼类的生长率和存活率，并产生一系列生理问题。水生环境中的氨毒性受多种因素调节。通常报道的是，摄食有助于鱼类解毒，从而提高其耐受氨氮的能力。然而，不同摄食水平对鱼类在暴露于氨应激时的影响仍有待确定。为了确定摄食水平如何影响鱼类对不同氨氮浓度的反应，用中国水产养殖系统中主要的异育银鲫养殖品种——彭泽鲫（Carassius auratus gibelio）进行了两项急性毒性实验。在实验 I 中，投喂彭泽鲫（摄食率 3%体重）在特定的氨暴露应激下表现出更高的存活率。有摄食的彭泽鲫 96-h 半致死氨氮浓度（LC50）比无摄食的（NF）高 1.1 倍。在实验 II 中，在低氨和高氨应激下，所有投喂组（2%F 和 4%F）的氨解毒能力均得到改善，与 NF 处理相比，肝脏谷氨酰胺合成酶（GSase）、谷氨酸脱氢酶（GDH）和谷氨酸浓度更高。摄食处理的肌肉糖原水平高于 NF，表明摄食鱼有更多的能量用于氨解毒。而与低氨处理（2.70mg L TAN；NH 0.06mg L）相比，暴露于高氨水平（26.03mg L TAN；NH 0.57mg L）的鱼的摄食量减少，肝脏、鳃和肾脏的组织病理学严重改变，以及肝脏和大脑中 GSase、GDH 和谷氨酸的产生减少。结果部分支持了我们的假设，并表明增加摄食可增强异育银鲫对氨氮的耐受性。在低氨应激下观察到最高的解毒代谢。而过度的氨暴露会抑制摄食并损害鱼类的解毒器官，从而降低异育银鲫的解毒代谢。
