Diapause in the marine copepod, Calanus finmarchicus - A review

Overwintering strategy plays a key role in the life cycle of Calanus finmarchicus. This species has developed adaptations such as arrested development, ontogenetic vertical migration and reduced metabolism in late developmental stages in order to survive long periods of food shortage, typical of temperate and high latitudes. At the same time preparations for the reproductive period are an integral part of its overwintering physiology. Terms such as resting phase or stage, dormancy, quiescence, hibernation and diapause are frequently encountered in descriptions of the overwintering conditions, but have not been defined. As many aspects of insect diapause are also found in the overwintering physiology of C. finmarchicus, an attempt was made to classify patterns of overwintering physiology according to insect diapause phases. A short comparison was also made with the diapause of freshwater cyclopoids. Although, with the knowledge available, it is difficult in some cases correspondence in the sequence of physiological changes suggest equivalence of insect and cyclopoid diapause and the physiology of the overwintering stages of Calanus finmarchicus.