diapaasi

Diapaasi, often written as diapause in English, is a developmental arrest process used by many organisms to survive unfavorable environmental conditions. In a diapause, growth, development, and/or reproduction are paused at a defined stage and resume only when conditions improve. This state is pre-programmed rather than a direct response to immediate conditions, distinguishing diapause from quiescence.

Diapaasi occurs in multiple life stages: embryonic diapause during early development; larval or pupal diapause in insects; and adult diapause in some species. Some plants exhibit embryo or seed diapause, in which embryo development or seed germination is delayed until environmental cues such as temperature or moisture are favorable.

Cues include photoperiod (day length), temperature, and resource availability. Endocrine and metabolic changes accompany diapause, often involving suppression of juvenile hormone and ecdysteroids, neuroendocrine signaling from brain cells, and shifts in insulin/TOR pathways. Termination resumes development in synchrony with favorable conditions, sometimes triggered by a change in photoperiod or temperature.

In temperate zones, diapaasi coordinates life cycles with winter or dry seasons, reducing mortality and synchronizing emergence. Notable examples include embryonic diapause in some moths and beetles, and reproductive diapause in the fall generation of the monarch butterfly. In agriculture and horticulture, diapause affects pest timing and crop viability, and understanding it aids in pest management and conservation.

Research on diapaasi informs broader topics in development, endocrinology, and climate adaptation. The term is used across taxa, and its specifics vary widely among species.