Diapause in Monogonont Rotifers

This review focuses on more recent findings on the diapause in Monogonont rotifers, since the major reviews by Pourriot & Snell (1983, Hydrobiologia 104: 213–224) and Gilbert (1992, Rotifera. In Adiyodi, K. G. & R. G. Adiyodi (eds), Reproductive Biology of Invertebrates, Vol. 5 – Sexual Differentiation and Behaviour. IBH Publishing Co., Oxford: 115–136; Vol. 6A – Asexual Propagation and Reproductive Strategies. IBH Publishing Co., Oxford: 231–263.). It covers diapausing egg formation, diapausing egg survival, and diapausing egg hatching as well as possible strategies involved in these processes. Data from laboratory and field studies exist, but little information is available on diapausing egg hatching in the field. Resting or diapausing egg production can be mictic and in some cases amictic. Mictic diapausing egg production depends on the balance between cues promoting and inhibiting mictic female production. Such cues can be either environmental or endogenous. Our knowledge on factors inducing mixis is still limited to a few species, but effects of crowding on mixis induction may be more widespread. Recent results also show that male mating behavior may play an important role in the successful production of diapausing eggs. Hatching may be induced by factors related to temperature and light conditions; also desiccation may have a role. However, desiccation of temporary habitats may also be damaging to diapausing stages. Although few data are available, those existing point to distinct differences between populations and the importance of clonal variation within populations regarding the initiation as well as the termination of diapause.