Effects Of Ammonia On Haematological And Immune Parameters Of Juvenile Southern Catfish (Silurus Meridionalis Chen)

This article investigated the effect of the environmental factor, TAN, on juvenile Southern catfish (Silurus meridionalis Chen). The 24-,48-,72-,96-h medial lethal concentrations ( LC50) of ammonia-nitrogen for the juvenile catfish were 182 mg l^-1 TAN (2.8mg l^-1 , NH3-N), 171 mg l^-1 TAN (2.7 mg l^-1 , NH₃-N), 151.4 mg l^-1 TAN (2.4 mg l^-1 , NH₃-N) and 123 mg l^-1 TAN (1.9 mg l^-1 , NH₃-N), which were determined by a series of acute toxic trials. The safe concentration of TAN for the juvenile catfish is 46.6 mg l^-1 TAN (0.7 mg l^-1 , NH₃-N). It was found that LC₅₀ declined with time.In chronic poisoning experiment, the individuals of juvenile southern catfish were randomly divided into five groups subject to different concentrations of TAN, i.e., 150mg l^-1, 120mg l^-1, 90mg l^-1, 60mg l^-1, 30mg l^-1 plus a control. Changes of the parameters , namely, red blood cells (RBC), differential leucocyte cells (DLC), haemoglobin (Hb), blood glucose (GLU), total protein (TP), albumin (ALB), alamine aminotransferase (ALT), aspartate aminotransferase (AST),alkaline phosphatase (ALP), antibacterial activity, superoxide dismutase (SOD), peroxidase (POD), phenoloxidase (PO) of the catfish blood, were measured on the 4, 7, 14, 21th day after the juvenile catfish were exposed to 0, 30, 60, 90, 120, 150 mg l^-1 total ammonia-nitrogen (TAN), respectively. Then the data were analyzed with statistic software SPSS(11.0) and Excel (2003 ) . The results were as follows:When the juvenile southern catfish were exposed to high concentrations of TAN, RBC, HCT and Hb of the catfish declined with increased concentrations and extended exposure span. Blood glucose increased in early stage and then declined as exposure extended;GLU in all groups increased significantly (P<0.05) on Day 7 and declined on Day 21, especially in groups with a high concentration treatment (150mg l^-1) (P< 0.05). The results suggested damage of experimental animals' hematopoiesis and a decline of their capability of oxygen transportation, which may be the main reasons of fish death caused by acute TAN toxicity.After 21 days of treatment with TAN, the activity of ALT, AST and ALP all increased by different margins, the activity of ALT and ALP increased significantly, which may imply they are more vulnerable to TAN treatment. Those data demonstrated adverse effects of ammonia on serum protein and showed that interior organs of the catfish treated in a series of TAN concentrations may be damaged to some extent.TAN inhibited such non-specific indices as SOD, POD, PO, antibacterial activity. Only on Day 4 that SOD and POD increased significantly in the groups subjected to 30 and 60mg I'1 TAN. Activity of enzymes was inhibited when the exposure time extended and it significantly decreased on Day 21 in high-concentration TAN treatment groups (90, 120, 150mg I'1). TAN treatment also affected DLC. Lymphocyte percentage of southern catfish in low level (30, 60, 90mg 1"') TAN groups increased significantly and then declined on Day 7 whereas those in low level (30, 60, 90mg I"1) TAN decreased significantly (P<0.05) on Day 14 and 21. Neutrophils changed likewise. The indices were closely related with fish's ability of oxidation resistance and immunity and their decline revealed a decrease in injury resistance and damage to immunity of the juvenile catfish after long-term exposure to TAN, as may be themain reason why fish exposed to TAN were more susceptible to other diseases.