diapause: one construct, many systems

In entomology diapause is a programmed state of suspended development (arrested growth, reproduction, or metamorphosis with depressed metabolism) that lets an insect bridge a predictably hostile season. Crucially it is anticipatory and token-cued, typically triggered by shortening daylength well before conditions deteriorate, rather than a direct response to current hardship, and it must be actively terminated before development can resume. Tauber, Tauber, and Masaki's Seasonal Adaptations of Insects is the standard synthesis of its induction, maintenance, and termination. The referent is an environmentally programmed developmental arrest.[1]

Unit

A token-cued, programmed arrest of insect development

Recovery means

Development resumes only once diapause is terminated by the required cue, such as a period of chilling or changing daylength

Measured by

Characterised by the cue (often photoperiod) that induces it, the depth of metabolic depression, and the conditions needed to break it

In mammalian reproductive biology embryonic diapause (delayed implantation) is a programmed pause in which the early blastocyst arrests and lies dormant in the uterus rather than implanting, resuming only when hormonal and environmental conditions favour it, so that birth is timed to a benign season. Renfree and Shaw's review Diapause treats this across marsupials and other mammals as the same class of adaptive developmental arrest named for the insect phenomenon. It is the identical construct (a cued, reversible suspension of development to match a favourable window) realised in a mammalian embryo.[2]

Unit

A reversible arrest of the mammalian blastocyst before implantation

Recovery means

The blastocyst resumes development and implants once the arrest is lifted by the appropriate hormonal and environmental cues

Measured by

Tracked by the arrest of blastocyst cell division and metabolism and by the timing of reactivation and implantation