View source for Diapause

'''Diapause''' is a [[physiological]] state of [[dormancy]] with very specific triggering and releasing conditions; there are various definitions and contexts in which the term is used, but its most common application is in [[arthropod]]s, especially [[insect]]s. One of the most explicit definitions, covering many of the important features, is the following:

''"a [[neurohormone|neurohormonally]] mediated, dynamic state of low [[metabolic]] activity. Associated with this are reduced [[morphogenesis]], increased resistance to environmental extremes, and altered or reduced behavioral activity. Diapause occurs during a genetically determined stage(s) of [[metamorphosis]], and its full expression develops in a species-specific manner, usually in response to a number of environmental stimuli that precede unfavorable conditions. Once diapause has begun, metabolic activity is suppressed even if conditions favorable for development prevail."''<ref>Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press, 414 pp.</ref>

Of primary importance is that diapause is not only induced by specific stimuli, but - once initiated - only certain stimuli are capable of releasing the organism from this state; the latter is essential in distinguishing diapause as a different phenomenon from [[hibernation]], for example.

A similar phenomenon occurs in the [[seed]]s or other resting stages of various [[plant]]s. In the eggs of various [[vertebrate]]s there is a phenomenon sometimes known as "[[embryonic diapause]]", which is also termed "delayed implantation," and is not directly equivalent to the phenomenon in arthropods, though in both cases there is a cessation of metabolic activity.

The definition above specifically includes the phrase ''"altered or reduced behavioral activity"'' to accommodate for the related phenomenon of '''reproductive diapause'''; this is a physiological condition where the organism itself will remain fully active, including feeding and other routine activities, but the reproductive organs experience a ''tissue-specific'' reduction in metabolism (with characteristic triggering and releasing stimuli). This is widespread in insects, including common and well-known species such as the [[Monarch butterfly]].<ref>Herman, W. S. (1981) Studies on the Adult Reproductive Diapause of the Monarch Butterfly, ''Danaus plexippus''. Biol. Bull. 160: 89-106.</ref>

==References==
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[[Category:Physiology]]
[[Category:Developmental biology]]

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