Studies on the Interrelationship of Temperature, Stress and Immunity in Carp (Cyprinus Carpio L.)

Abstract

The thesis examines the effect of temperature and handling stress upon in vitro and in vivo immune functions in the common carp (Cyprinus carpio L.). Fish were subjected to handling stress or to handling stress and temperature change, before monitoring thechanges in plasma cortisol and glucose levels. Plasma cortisol was found to be significantly elevated in both groups after three hours, returning to basal levels after 3 - 6 days. There was no significant difference between the two groups, indicating that temperature change played a subordinate role to the handling stress. The plasma glucose levels were also found to be elevated in both groups, with the fish subjected to handling stress alone exhibiting a greater increase. A return to basal levels occurred over a six day period. The effects of temperature on immunity were also examined. The haemagglutinin reaction to peritoneally injected sheep erythrocytes was monitored, over a period of five weeks, at 10°C and 20°C. Peak titres were reached on day 17 post - injection at the higher temperature and on day 27 post - injection at 10°C. The levels of the peak titres were not affected by temperature. The rate of in vitro phagocytic particle clearance was also examined at the two temperatures. Candida albicans was cleared from suspension in 48 hours at an in vitro incubation temperature of 10°C, and in 16 hours at a temperature of 20°C. The temperature at which fish were acclimated (either 10°C or 20°C) had no effect upon the rate of particle clearance. ‘Arming’ the fish leucocytes by administering a priming dose of Candida albicans 15 days prior to the collection of leucocytes, resulted in a faster in vitro clearance of Candida particles at both temperatures. ‘Opsonisation’ of Candida albicans, using the immune sera from the fish that received the priming injection, did not appear to affect the clearance rate of the Candida in vitro.