molts

Molts, or molting, is the process by which an animal sheds its outer covering or skin and forms a new one. In many invertebrates, especially arthropods, molting allows growth by replacing a rigid exoskeleton with a larger one. In some vertebrates and other organisms, molts refer to periodic shedding of skin, fur, or feathers.

In arthropods, molts occur in hormonally regulated cycles. A new cuticle forms beneath the old one during premolt. The epidermis separates from the old cuticle in a phase called apolysis. During ecdysis the animal splits and emerges from the old exoskeleton. The new cuticle then hardens through sclerotization.

Crustaceans such as crabs and lobsters molt several times as they grow, often influenced by environment and nutrition. Insects molt in discrete instars, controlled by the molting hormone ecdysone; juvenile hormone levels help determine whether development proceeds to metamorphosis or remains in a larval form.

Non-arthropod molts include birds replacing feathers, reptiles shedding scales or skin, and amphibians shedding skin in patches; mammals sometimes molt hair seasonally. The timing and pattern of molts vary widely among species and life stages.

Molting is essential for growth and maintenance of protective coverings, but it can leave the animal vulnerable to predation and environmental stress. Studying molting provides insight into endocrinology, development, and ecology across many animal groups.