THE EFFECTS OF CROWDING STRESS ON THE NONSPECIFIC IMMUNE-RESPONSE IN FANCY CARP (CYPRINUS-CARPIO L)

The effect of crowding condition (25 g l(-1)) on the non-specific immu ne response of fancy carp (Cyprinus carpio L.) was studied. The fish w ere stressed for 1, 7, 14 and 30 days. The total serum protein concent ration, serum lysozyme activity, bactericidal complement activity and chemiluminescent (CL) response of the phagocytic pronephros cells were all measured on day 30 after the initial crowding stress. Their susce ptibility to infectious disease was tested by challenging with the bac terium Aeromonas hydrophila. Stress indicators such as plasma cortisol , glucose and chloride levels were also determined. The results indica ted that the levels of cortisol and glucose were significantly increas ed from day I onwards until day 30. On the other hand, the activities of non-specific immune parameters except for phagocytic activity signi ficantly dropped on day 1, and then remained low throughout the remain ing time intervals. Disease resistance of the stressed fish was signif icantly reduced on day 7. However, no great difference in resistance a gainst A. hydrophila was found between day 7 and day 30. No mortality was encountered in either stressed or unstressed fish. This indicates that fish might have an adaptation capability to survive under a stabl e, chronically stressful environment although the activities of non-sp ecific defence mechanisms were significantly lower than those of the u nstressed fish. (C) 1995 Academic Press Limited