Life-cycle synchrony in a marine copepod

It is clearly advantageous to an organism in a periodically varying environment to synchronise its life-cycle to that variation. Previous studies have demonstrated an effective mechanism by which such entrainment occurs at the individual level, through the response of development rate to varying conditions. It has been shown that synchrony requires two or more life stages that have characteristic and different developmental responses to the environment. One such difference, that has been shown to promote synchrony, is a stage specific period of arrested development (quiescence or diapause). Since the marine copepod Calanus finmarchicus undergoes just such a period of diapause, we test whether this provides a mechanism for synchrony. Using a simple model of the life-cycle we show that in the absence of diapause a population in Malangen Fjord, Norway, is unable to achieve synchrony. We then demonstrate the effectiveness of diapause in copepodite stage five in inducing entrainment. The timing of diapause is critical in determining the number of generations per year. The study highlights the importance of increasing our knowledge of Calanus finmarchicus diapause in order that we may better understand its ecology. We conclude that for this marine copepod diapause may play an important part in entraining its life-cycle to environmental periodicity