An actographic study of diel activity in the semelparous polychaete Nereis (Neanthes) virens Sars in relation to the annual cycle of growth and reproduction

Summary Photoperiod has a profound influence on the life cycle of Nereis (Neanthes) virens coordinating the transition from somatic growth to reproductive development. Here we report on a rapid method to characterize the diel component of the photoperiodic response and characterize the photoperiodic response curve. The diel emergence activity of the semelparous polychaete Nereis (Neanthes) virens Sars has been investigated by means of an automated actograph. Emergence events were recorded for every second of real time and the number of events per hour analyzed over periods of up to 5 consecutive days under a variety of photoregimes. There is a marked nocturnal pattern of activity. The number of excursions from the burrow system is high during the night reaching near zero shortly after dawn. Excursions from the burrow system during daylight hours were much less frequent. The total number of emergence events per 24 h was significantly higher under LD 16:8 than under LD 8.16 even though the period of dark, w...