Abstract

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.

Highlights

  • Many aquatic invertebrates possess a diapause stage that allows them to endure extended periods of unfavourable conditions and to disperse passively across non-aquatic boundaries (Hairston, 1996; Brendonck & De Meester, 2003)

  • Organisms with heterogonic life cycles (e.g. Daphnia or monogonont rotifers) reproduce asexually for several generations by producing subitaneous eggs, which hatch within hours, whereas once a zygote has been formed after sexual reproduction, the embryo arrests its development and enters diapause (=resting egg, RE)

  • Two additional treatments were used to compare the length of embryonic development times: amictic eggs (AE) and REs stored in cold/dark

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Summary

Introduction

Many aquatic invertebrates possess a diapause stage that allows them to endure extended periods of unfavourable conditions and to disperse passively across non-aquatic boundaries (Hairston, 1996; Brendonck & De Meester, 2003). This diapause stage is often linked to sexual recombination. The duration of diapause is typically considered long relative to the lifespan of active individuals. Diapause lasts for months to years, while individual lifespan is only days to a few weeks (Gilbert, 1974; Pourriot & Snell, 1983; Schroder, 2005)

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