It is a physiological state with very specific conditions. Diapause is a mechanism used as a means to survive predictable, unfavourable environmental conditions, such as temperature extremes, drought or reduced food availability. It is most often observed in arthropods, especially insects, and in the embryos of many of the oviparous species of fish in the order Cyprinodontiformes.
Not only is diapause started by specific stimuli or conditions, but once it is started, only certain other stimuli are capable of bringing the organism out of diapause. This distinguishes diapause from other forms of dormancy such as hibernation.
Activity levels of diapausing stages can vary considerably among species. Diapause may occur in a completely immobile stage, such as the pupae and eggs, or it may occur in very active stages that undergo extensive migrations, such as the adult Monarch butterfly, Danaus plexippus. In cases where the insect remains active, feeding is reduced and reproductive development is slowed or halted.
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- R.F. Chapman 1998. The Insects: structure and function. 4th ed, Cambridge University Press. p403. ISBN 0521-57890-6
- Tauber M.J., Tauber C.A., Masaki S. 1986. Seasonal adaptations of insects. Oxford University Press.
- Murphy, W. J.; Collier, G. E. (August 1997). "A molecular phylogeny for aplocheiloid fishes (Atherinomorpha, Cyprinodontiformes): the role of vicariance and the origins of annualism". Molecular Biology and Evolution. 14 (8): 790–799. doi:10.1093/oxfordjournals.molbev.a025819. PMID 9254916.
Annual aplocheiloid killifish embryos possess a rare ability among vertebrates to enter stages of developmental arrest (diapause) when subjected to adverse environmental conditions. Diapause does not occur in embryos of the viviparous and ovoviviparous species of Cyprinodontiformes.PMID 9254916