| With the increasing environmental pollution, algal blooms outbreaks frequently all of the world, microcystin produced by cyanobacteria and their derivatives-ammonia etc has a serious impact on environmental and ecological systems.Toxic cyanobacterial (blue-green algal) blooms have been associated with the embryo development, behavior and growth but also in the physiological and biochemical changes of liver, kidney and other internal organs. Ammonia can make fish bradykinesia, loss of appetite, but also has a direct impact on disease resistance-related metabolic enzyme in animal, ammonia plays a role in toxicity by decreasing disease resistance of aquatic animals. I chose crucian carp(Carassius auratus) which is a common animal in Taihu as a subject, and investigated the effects of ammonia and microcystin-LR on biochemical indices of tissue and blood of juvenile crucian carp (Carassius auratus) using acute and chronic exposure experiments. The results showed that:1. The LC50 values of NH3-N at 24,48, and 96 h were 0.697±0.036, 0.581±0.023, and 0.511±0.007 mg L-1, respectively. Safe concentration of NH3-N for juvenile crucian carp was 0.123±0.027 mg L-1. The results showed that the LC50s of ammonia to juvenile crucian carp decreased significantly with time and fitted the hyperbolic decay model well. In the experiments, catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) in the livers of juvenile crucian carp fluctuated with time and ammonia concentration and had similar trend. And at 96 h, CAT, SOD, and GSH increased significantly in the treatment of 0.282 mg L-1 compared to those in other ammonia concentrations, after that decreased with ammonia concentration, suggesting that higher ammonia concentration can induce antioxidant defenses of juvenile crucian carp.2. In chronic exposure experiments, juvenile crucian carp were randomly divided into four groups and exposed to four different concentrations of NH3-N (0.107,0.214, 0.321 & 0.428 mg L-1) plus a control. Juvenile crucian carp were exposed in different ammonia solutions for 45 days and then immediately transferred to pristine freshwater to initiate a 15-day recovery period. During this time fish were periodically sampled on their blood, liver tissue and gill with the biochemical index:red blood cell (RBC), the total hemoglobin (Hb), malondialdehyde (MDA), alanine aminotransferase (GPT), aspartate aminotransferase (GOT), CAT, SOD,GSH, gill Na+/K+ ATPase, the feeding and growth indices measured. Then the data were analyzed with statistic software SigmaPlot (11.0) and Excel (2003). The results were as follows:(1) In the work, the feeding rate (FR), protein efficiency ratio (PER), and specific growth rate (SGR) of the control and lower concentration groups were significantly higher than those exposed to higher ammonia, whereas the feed conversion ratio (FCR) increased significantly with increasing concentrations of NH3-N in the water, from the models, their EC50s were 0.3049,0.2881,0.2115, and 0.1997 mg L-1 NH3-N, respectively, especially concentrations of NH3-N≥0.321 mg L-1. Which indicated sub-lethal ammonia in the external environment can significantly impair the feeding and growth of fish.(2) In the liver tissue, CAT, SOD, GSH, GPT, GOT, MDA in the livers of juvenile crucian carp have time-dose effect after 45 days of ammonia treatment. After a 15-day recovery period, some indices (CAT, SOD, GSH) appeared metabolic compensation, other indices (GPT, GOT, MDA) recovered to normal levels. The results showed that long-term sub-lethal ammonia in the external environment can significantly affect their protective functions, which inhibit the body's normal physiology of metabolism.,(3) In the blood, the fish exhibited a continuous decrease in RBC and Hb with time and the concentration of ammonia increased, especially NH3-N>0.214 mg L-1. The results showed that ammonia had a little effect on the SOD, whereas MDA increased with time prolong, especially to the 45 days, the level of MDA increased highest among the 4 phases. In addition, the level of RBC, Hb, MDA returned to normal after 15-day unexposure, however, high concentration of ammonia returned slower than low ones.(4) In the gill tissue, chronic ammonia exposure can cause reduction in CAT, Na+/K+ ATPase activity and MDA content in juvenile crucian carp, but had a little effect on the SOD. At the end of the experiments, Na+/K+ ATPase, CAT, MDA returned to the normal level after 15-day recovery, whereas SOD appeared metabolic compensation.3. Actue toxicity and toxic effects of ammonia and microcystins, alone and in combination on juvenile crucian carp for 168 h, posure doses of MC-LR and ammonia for crucian carp were 50,300μg kg-1 and 0.107,0.428 mg L-1 respectively.We focused on liver and damage of blood carp clinical, anatomical symptoms, liver injury, gill injury and damage of blood, the physiological and biochemical index were investigated to detect damage on fish. The results were as follows:(1) Aseites associated with intrahepatic and anal haemorrhage in crucian carp injected with microcystins, especially in high doses; MC with ammonia can make fish respiration rate has a first increased and then decreased trend in low concentrations of single and combined groups, respiration rate was inhibited in high concentration, and compound groups had a stronger effect than the others.(2) MC exposure can make CAT increase, SOD and GSH decreased within a short time in the liver; whereas ammonia had a little effect on them; whereas the phenomena was aggravated by MC and ammonia with the mutual influence.In the experiment MC and ammonia had little effect on Na+ /K+ ATPase in the gill both in single and combined groups.(3) We evaluated alterations in activities of some serum liver-eorrelated enzymes(ALT, AST, AKP and LDH). Serum enzyme aetivities showed marked inereases with inerease of MC does, and the activities of them rised to the highest level after 48 h, however, ammonia had no significant effect on them.Fishes treated with MC, ammonia decreased in Hb respectively, and there was a time-dose effect, combined groups strengthened this effect. SOD and MDA increased with the concentration of MC and there was a significant difference, whereas ammonia had little effect on them, Combined group has a stronger effect on the MDA.(4) Residue of MC in the liver was determined by (LC/MS) method after 168 h MC injection, the residues in the liver was about 30%-43% of the original injection, ammonia has no effect on the residues of microcystin in the liver (P=0.353)... |
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