Molting

Molting or moulting, also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer layer or covering), either at specific times of the year, or at specific points in its life cycle.

Overview

Molting can involve shedding the epidermis (skin), pelage (hair, feathers, fur, wool), or other external layer. In some groups, other body parts may be shed, for example, wings in some insects or the entire exoskeleton in arachnids.

Process

For most organisms, the process of molting is synchronized with other physiological processes and is controlled by neurohormones. These hormones include ecdysteroids and juvenile hormones.

In different animals

Molting occurs in a wide range of animals, including mammals, birds, insects, crustaceans, fish, and reptiles. Each of these groups has a different process and purpose for molting.

Mammals

In mammals, the skin is continually being renewed, but small flakes of skin are shed unnoticed. Some mammals, such as the Virginia opossum, undergo a complete molt, shedding and replacing their fur in one continuous process.

Birds

In birds, molting is the periodic replacement of feathers by shedding old feathers while producing new ones. Feathers are dead structures at maturity which are gradually abraded and need to be replaced.

Insects

Insects, being the largest group of molting animals, replace their exoskeletons through a process called ecdysis. During ecdysis, the insect sheds its entire exoskeleton, leaving the animal vulnerable to predators and environmental hazards.

Crustaceans

Crustaceans must molt to grow, since their exoskeleton is rigid and cannot expand like skin. This process is called ecdysis, and the stages of molting are collectively known as the molt cycle.

Fish

Fish also molt, but they shed their scales rather than their skin. This is usually a response to damaging conditions such as water pollution or a high parasite load in the water.

Reptiles

Reptiles, including snakes and lizards, shed their skin in one piece, unlike mammals and birds. This process, called ecdysis, allows the reptile to grow.

See also

• Ecdysis
• Feather
• Scale (zoology)

References

Molting Resources
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