Extremely short diapause in rotifers and its fitness consequences

All monogonont rotifers have a diapause stage (=resting egg, RE), which allows them to endure unfavourable periods and to disperse across non-aquatic boundaries. However, recent research has shown that REs may often develop spontaneously within a few days, which seems to partly offset these adaptive explanations. In this study, I determined the minimum duration of RE development in a Brachionus calyciflorus Pallas 1766 strain in relation to other life-history variables. RE development took at least 72 h, but 50 % of those REs that hatched within the first week did so in a much synchronized manner, within 72-82 h. By contrast, amictic egg development took 11 h, while REs that had been previously stored in the cold/dark for weeks, hatched within 21 h if exposed to warm/light conditions. I discuss the fitness consequences of such fast RE development and whether it can ameliorate the costs of sex in this system. I also propose a conceptual model of RE development, which assumes two obligatory phases of pre- and post-diapause development and a facultative phase of dormancy. The latter phase may be missing in spontaneously developing REs.