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

1999; Taylor & Francis; Volume: 35; Issue: 2 Linguagem: Inglês

10.1080/07924259.1999.9652377

2157-0272

Kim S. Last, P. J. W. Olive, Alasdair J. Edwards,

Cephalopods and Marine Biology

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, when spontaneous emergence mainly occurs, was longer. The actographic records suggest that under LD 8:16 the feeding behaviour of the animals is substantially reduced compared with that observed under LD 16:8. A photoperiodic response curve has been obtained where there is a critical LD cycle around LD 11:12 and a progressive increase in emergence rate between LD 12:12 and LD 16:8. The mean number of emergence events per day is directly related to the duration of the photophase and inversely related to the scotophase duration although emergence mainly occurs during the night.