Diapause
Diapauseis a delay in development which hasevolvedin response to regular periods of adverse environmental conditions.[1][2]
It is aphysiologicalstate 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 inarthropods,especiallyinsects,and in theembryosof many of theoviparousspeciesof fish in the orderCyprinodontiformes.[3]
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 ofdormancysuch ashibernation.
Activity levels of diapausing stages can vary considerably among species. Diapause may occur in a completely immobile stage, such as thepupaeand eggs, or it may occur in very active stages that undergo extensive migrations, such as the adultMonarch butterfly,Danaus plexippus.In cases where the insect remains active, feeding is reduced and reproductive development is slowed or halted.
References[change|change source]
- ↑R.F. Chapman 1998.The Insects: structure and function.4th ed, Cambridge University Press. p403.ISBN0521-57890-6
- ↑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.PMID9254916.
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 theviviparousandovoviviparousspecies of Cyprinodontiformes.
PMID 9254916