apolysis

Apolysis is a biological term describing the detachment of epidermal cells from the inside surface of the old exoskeleton (cuticle) during the molting cycle of many arthropods. It precedes ecdysis, the shedding of the old cuticle, and serves as a preparatory stage for growth by molting. The term derives from Greek apo, away, and lysis, loosening or dissolution.

During apolysis, the epidermis secretes molting fluid containing enzymes that partially digest the endocuticle, weakening the adhesion between the epidermis and the cuticle. This allows the epidermal layer to detach and reorganize while a new epicuticle and procuticle are formed beneath the old layer. When the new cuticle is sufficiently formed, the old cuticle ruptures and is shed in the subsequent molt (ecdysis), enabling expansion and progression to the next developmental stage.

Apolysis is observed in many crustaceans and insects, and to a lesser extent in other molting arthropods. The process is hormonally regulated, primarily by ecdysteroids (the molting hormones), with juvenile hormone levels influencing the pattern and outcomes of the molt, including metamorphosis in some species.

Significance and applications: Apolysis is essential for successful molting and growth in arthropods. Disruptions to apolysis can lead to molting failure and mortality, a fact that has implications for ecological interactions and pest-management strategies.