Arrange the following physiological and anatomical events of ecdysis (moulting) in arthropods in the correct chronological sequence from initiation to final hardening of the new exoskeleton.
- 1The epidermis detaches from the old cuticle (apolysis) and secretes inactive moulting fluid into the exuvial space.
- 2Moulting enzymes activate to digest the old endocuticle while a soft new procuticle is synthesized beneath.
- 3The organism increases its internal hydrostatic pressure by swallowing air or water, cracking the old exoskeleton along ecdysial lines.
- 4The organism emerges from its old exoskeleton (exuviae) and inflates its body to stretch the soft new cuticle.
- 5Sclerotization takes place as phenolic compounds cross-link cuticular proteins, darkening and hardening the new exoskeleton.
Answer
The correct chronological sequence of ecdysis events is: (1) Detachment of the epidermis from the old cuticle and secretion of inactive fluid, (2) Enzymatic digestion of the old endocuticle and synthesis of a new soft cuticle, (3) Internal pressure buildup to crack the old exoskeleton along suture lines, (4) Emergence from the exuviae and expansion of the soft body, and (5) Sclerotization to permanently harden the new cuticle.
Ecdysis begins with apolysis, where the living epidermal layer detaches from the old cuticle and releases inactive fluid. Once activated, enzymes break down the old endocuticle so materials can be reabsorbed while a new cuticle forms beneath. The arthropod then inflates its internal pressure to crack the old exuviae along ecdysial lines. After emerging, it expands its body volume to stretch the soft new cuticle. Finally, sclerotization chemically hardens the stretched cuticle to complete the process.
Step-by-Step Solution
Key Concept
Chronological Sequence of Arthropod Ecdysis