Many organisms produce dormant stages, building up large germ banks in the sediments. Timing of emergence from these germ banks is a key feature in the recurrent cycle of dormant and active life stages. We exposed dormant egg bank samples of Daphnia magna from (semi-)permanent ponds to seasonal cues mimicking temperature and photoperiod during early spring, late spring, and summer in the region of sampling and investigated hatching success and response time after incubation. Whereas no differences in hatching success were observed between seasonal treatments, within each seasonal treatment a variable fraction of eggs postponed the hatching response for several days. We link immediate versus short-term delayed hatching to a trade-off between the advantages of quick niche filling and the unpredictability of reproductive success under unstable environmental conditions. A scenario where hatching investment is spread over immediate and delayed hatchers as a bet-hedging strategy is corroborated by environmental data on the risk of abortive hatching in early spring and by modeling results that show that immediate versus short-term delayed hatching is a valid alternative to bet-hedging over years in the investigated habitats to cope with variability in the onset of favourable conditions.
Nomenclature: Daphnia magna Straus, 1820.