Effect of 12hrs Phase Delay in Light-Dark Cycle, Subsequent Enucleation Followed by Exogenous Melatonin Treatment on Air-Breathing Activity Rhythm in Clarias Batrachus

Abstract

It has been aimed to examine the effect of 12hrs phase delay in light-dark cycle, subsequent enucleation followed by exogenous melatonin treatment on air-breathing activity rhythm in Clarias batrachus. Following acclimation, seven Clarias batrachus approximately of the same size were transferred to chronocubicles. They were initially maintained under LD 12:12 regime (lights on 06:00hrs) and considered as control group. The air-breathing activity was monitored with the help of PC based event recorder for 7days. Then, the phase delay of 12hrs in light dark cycle was maintained by reversing the light schedule with the help of automatic timer for consecutive 10 days. Subsequently the animals were enucleated and left in the similar photoperiod for next ten days and then they were given melatonin treatment (2g/fish) daily at the initiation of subjective dark hour for another ten days. The air–breathing activity was recorded with the help of infrared photoswitches connected to a microprocessor based event recorder. The results obtained by actograms depicted the occurrence of entrained rhythm with the timings of light on/off in air-breathing activity under LD 12:12 regime. Later, the activity pattern obtained from the actogram revealed that the air-breathing activity rhythm is quickly entrained with the timings of lights on/off as phase delayed by 12 hrs and the activity was found to be increased and decreased during the experimental dark and light hours of the LD regime, respectively. Further, after enucleation under phase delay by 12hrs, the activity curve graph showed that the air-breathing activity rhythm is similar as obtained under phase delay, showing increased activity during the experimental dark hour in most of the individuals. Then, individuals after receiving daily treatment of melatonin under the phase delayed by 12 hrs showed occurrence of the two peaks in air-breathing activity rhythm at 12:00 hrs and 24:00 hrs in most of the enucleated.