diapause

Diapause is a developmental arrest observed in many insects and in other organisms, including some nematodes, crustaceans, and plant seeds. It is a genetically programmed state that halts development and metabolism during unfavorable environmental conditions, typically at a specific life stage such as egg, larva, pupa, or adult. It allows survival through adverse seasons.

It is distinct from quiescence; diapause is anticipatory, hormonally regulated, often terminating only after a cue, and involves metabolic suppression and increased stress tolerance. Quiescence directly follows unfavorable conditions and ends quickly when conditions improve.

Mechanisms include environmental cues like photoperiod and temperature; hormonal control mainly via juvenile hormone and ecdysteroids; changes in gene expression and metabolism reduce energy use.

Types: obligatory diapause occurs at a fixed stage regardless of conditions; facultative diapause is induced by environmental cues, such as short day length signaling winter; termination requires specific cues, such as prolonged exposure to favorable conditions.

Occurrence and impact: common in temperate regions; eggs or larvae may overwinter; diapause influences population dynamics and pest management; some plant seeds exhibit seed diapause, a comparable dormancy.