Periodicity in the hatching of digenean eggs: a possible circadian rhythm in the life-cycle ofTransversotrema patialense

Abstract

SUMMARYThe temporal distribution of hatching of the embryonated eggs ofTransversotrema patialensehas been examined under different temperature and illumination regimens. Under a DL 12: 12 regimen at 30°C egg hatching exhibited a circadian rhythm with a period of 24 h. Within a diel time-frame hatching was distributed over the final 9 h of the light period with less than 2% of the eggs hatching during the dark period. This pattern was temperature independent over the range 25 to 30°C and persisted under constant illumination. It is suggested that the timing of hatching is under endogenous control and is functionally related to a circadian rhythm of behaviour of the intermediate host mollusc,Melanoides tuberculata.