Shedding: Peeling Away the Mystery Christina Miller Last update: Thursday, June 12, 2008

Most reptiles and amphibians will periodically shed their skin. A common belief is that reptiles, like invertebrates, will shed their skin so that their body can grow larger. This is actually a myth!

The skin is our first line of defense against injury and microorganisms. It helps keep water inside our body, protects our muscles and nerves from the environment, and human skin produces sweat to help cool us down. Humans and other mammals are constantly shedding the outermost protective layer of their skin, the epidermis, in small flakes. This outer layer has a cushion of dead skin cells that have been toughened with a protein called keratin. These dead cells will be shed, because new cells are constantly being produced beneath them to replace the older dead cells.


Anatomy

As implied above, the epidermis is the outermost layer of the skin. The epidermis and the layer below it, the dermis, make up the cutis or cutaneous layer of skin. The dermis is made up of connective tissue and contains nerves, blood and lymphatic vessels, sweat glands, sebaceous (oil) glands, etc. Below the cutis is the subcutis, or subcutaneous layer, made up mostly of adipose tissue (fat).

Reptile skin is different than mammalian skin. Reptilian epidermis has many tiny folds toughened with ß keratin, which is a protein unique to reptiles (other animals produce only a keratin). These folds have a flexible, a keratin base so that they have some limited movement. Think of reptile scales as many tiny finger nails with a bit more "give" to their flexible base.

The reptile epidermis actually consists of three layers:

 

• Stratum corneum: "Hardened layer." The protective, outer keratinized layer described above.
• A middle layer rich in lipids (fats), contributing to the skin's waterproof character.
• Stratum germinativum or stratum basale: "Germinative" or "basal" layer. The innermost layer of cells, these produce keratin as well as the cells that move upwards to replace old cells from the stratum corneum.

The ecdysis cycle

As the cells from the stratum germinativum move outwards they will eventually become the tough, keratinized cells of the stratum corneum. Humans, and all mammals, are always flaking off these cornified cells, but reptile epidermis is normally in a "dormant" stage. The following diagram depicts the changes in the epidermis at the cell level, from left to right.

Image based on Mader 2006, Reptile Medicine and Surgery.

	Resting Phase	Beginning of Renewal Phase	Renewal Phase	End of Renewal Phase
	Length is indefinite.	Lasts between 5-7 days.	Lasts between 3-4 days.	Shedding begins 3-4 days after the skin becomes clear.
		Ecdysis cycle (approx. 10-14 days)

The phases are as follows:

 

• Resting phase: This is the animal's "typical" skin condition, its length is indefinite. The period of time between ecdysis cycles varies between species and between individuals depending on age, health status and physiological status.
• Beginning of renewal phase: The skin becomes dull and colours are muted, as the stratum germinativum begins to create a new layer of cells. This phase lasts between 5-7 days.
• Renewal phase: The skin becomes very dull, and the spectacles are white or opaque. More cells divide in the stratum germinativum and migrate upwards, the outermost cells undergo keratinization. This phase lasts between 3-4 days.
• End of renewal phase: The skin and eyes become clear and shiny. Lymphatic fluid infiltrates the cleavage zone, creating a gap between the inner and outer epidermal generation layers. Shedding of the old stratum corneum begins 3-4 days after the skin becomes clear.

The pattern in which ecdysis occurs on the body does vary with different groups of herps. Lizards shed their skin either in patches (many iguanids and agamids) or all at once (skinks, geckos). Snakes shed their skin all at once. Some chelonians do not shed their skin, although some aquatic and semi-aquatic species will shed one scute at a time.

Shedding in captivity

Shedding is in inevitable experience with your pet reptile. There are several factors that contribute to the frequency of shedding:

• Age: Younger animals will shed more often than older animals.
• Nutrition: Animals that are fed a healthy, balanced diet will shed more often. Note that animals with a protein-deficient diet will be more likely to have difficulties shedding, this is discussed further below.
• Health: Healthy animals will shed more often than sick or diseased animals.
• Season: Most reptiles display seasonal changes in activity levels and appetite. Consequently, there are changes in shedding schedule.

Your pet's shedding schedule is not as important as facilitating the shedding process. Many species need to have a rough surface, like a rock or a branch, to help remove the shedding skin. This is especially important for snakes, that rub their nose to start the shed, then use the surface to pull the shed skin off like an inverted sock. Lizards will also use their claws and teeth to remove shed skin.

A humid hide can be a simple plastic food container with an entry hole, filled with damp sphagnum moss or paper towels. This "rock" is actually a moulded humid hide with a removable lid for easy access inside. It is filled with damp sphagnum moss, and a snake.

Providing a humid microhabitat (humid hide) is also important. Reptiles will spend a lot of time either soaking in their water dish or sitting in a humid hide during ecdysis. It is thought that the extra humidity helps skin sloughing. Species that have spectacles over their eyes will be extra secretive during the renewal phase where the scales become opaque, so they are almost blind. Failure to provide a humid hide can result in shedding problems. Humid hides can be as simple as a plastic food container with an entry hole cut in the side or top, filled with a moist substrate like sphagnum moss or paper towels. If you use slabs of bark or rock caves as hides in your enclosure, adding sphagnum moss to the substrate in or under these hides and ensuring they stay moist is also effective. There are now "natural-looking" rock hides with removable lids available.

Dysecdysis

Dysecdysis is a condition of "difficult ecdysis," where shed skin is stuck on the body. There exist various causes:

• The most common cause for this is too dry of an environment, and lack of a humid hide.
• Poor nutrition (more specifically, a protein-deficient diet) may also cause dysecdysis, as the body cannot produce enough lymphatic fluid to effectively separate the old and new epidermal layers.
• Dehydration (caused by poor husbandry or by disease) may result in dysecdysis.
• Ectoparasites such as mites can cause inflammation, and shed skin may not slough properly.
• Skin infections (caused by bacteria or fungi) may interfere with normal ecdysis.
• Large wounds or scars may have chronic, local dysecdysis due to the scale deformities that may occur.

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