Diapausa

Diapausa, known in English as diapause, is a hormonally controlled developmental arrest used by many organisms to survive unfavorable conditions. Unlike immediate dormancy caused by current conditions, diapause is an anticipatory, programmed state that halts growth at a specific life stage and may persist for a defined period or until environmental cues signal resumption. It is especially common in insects and crustaceans and also found in some nematodes and seeds.

The diapause state is maintained by coordinated hormonal and metabolic changes. In insects, environmental cues such as photoperiod and temperature influence the endocrine system, including juvenile hormone and ecdysteroids, to trigger entry into diapause. Metabolic rate decreases, energy reserves accumulate, stress tolerance rises, and gene expression shifts to support long-term survival. Development resumes when favorable conditions return and appropriate cues are detected.

Types and timing: obligatory diapause occurs as a fixed part of a species' life cycle and is relatively insensitive to short-term conditions; facultative diapause is conditional and triggered by adverse cues. Diapause can occur at eggs, larvae, pupae, or adult stages, depending on the species. A diapause syndrome may include reduced reproduction, altered behavior, and increased cold or desiccation tolerance. In plants, a related process—seed dormancy—prevents germination until conditions favor seedling survival.

Examples and significance: many Lepidoptera, beetles, and mosquitoes exhibit diapause at various stages. The nematode Caenorhabditis elegans forms a dauer larva in response to crowding or food shortage. Diapause influences population dynamics, pest management, and species distribution, and climate change is expected to affect its timing and duration.