Immunological parameters of Javanese carp Puntius gonionotus (Bleeker) exposed to copper and challenged with Aeromonas hydrophila

This study was to determine the median lethal concentration (LC50) of coppe r to Javenese carp, Puntius gonionotus (Bleeker), and the immune response a fter the fish were exposed to sublethal levels of copper and challenged wit h formalin killed Aeromonas hydrophila. The LC50 of copper on P. gonionotus at 24, 48, 72, 96 and 120 h were estimated as 2.17, 0.91, 0.57, 0.53 and 0 .42 mg 1(-1), respectively. To determine the effect of copper on the immune system, fish were exposed for 66 days to 0.05, 0.10 and 0.15 mg Cu 1(-1). After 56 days of initial exposure to copper, fish were challenged with 0.1 ml of 45 x 10(5) cfu ml(-1) formalin killed A. hydrophila and maintained in the same concentration of copper. After the challenge, the immune response was monitored for 2 weeks using haematological and serological assays. Dur ing the initial phase of exposure to copper, significant changes were noted in the white blood cell, lysozyme, potential killing activity, total plasm a protein, total immunoglobulin and haematocrit levels between the control and treated fish. One week after challenge with A. hydrophila, there was a significant increase in the values of white blood cells, total protein and total immunoglobulin compared to the values before the challenge. However, these values were not significantly different (P>0.05) between the control and the treated fish. In contrast, NET and lysozyme assays exhibited a sign ificant difference (P<0.05) in fish exposed to 0.10 mg Cu 1(-1) (0.525 <plu s/minus> 0.17; 24.42 +/- 3.35 x 10(2) mu mg ml(-1)) and 0.15 mg Cu 1(-1) (0 .536 +/- 0.19; 21.78 +/- 1.29 x 10(2) mu mg ml(-1)) compared to the control (0.746 +/- 0.31; 30.73 +/- 5.42 x 10(2) mu mg ml(-1)) after the bacterial challenge (day 61). There was however no significant difference (P>0.05) in NET and lysozyme levels in fish exposed to lower level of copper (0.05 mg Cu 1(-1)), suggesting the absence of immunosuppressive effects at lower lev el of exposure. (C) 2001 Academic Press.