Diel variations in the selected serum immune parameters in Oreochromis mossambicus

Almost all metabolic processes in an organism alternate through high and low activity phases with a regular periodicity of nearly 24 h. These daily/diel variations are governed by factors such as light, weather conditions, availability of food or predator activity. The immune system in fish is expected to follow the same routine based on external cues from the environment which it lives. The present study was carried out to investigate such daily/diel variations in selected immune parameters such as serum lysozyme and peroxidases activity, total serum globulin level and peripheral blood leukocyte count in Oreochromis mossambicus. The fish were maintained in semi natural condition (i.e.12L:12D). The results showed significant rise in serum peroxidases and lysozyme between 0200 h and 0600 h of the day and serum cortisol exhibited elevated level between 2200 h and 0600 h. Total serum globulin exhibited peak concentration from 1400 h to 1800 h. Thus suggesting the possibility of rhythmic functioning of immune system in O. mossambicus.