**7. Ecdysis**

The shedding of scales is called *ecdysis*, trivially mostly named molting or sloughing. Sloughing serves number of functions. Firstly, the old and worn skin is replaced and secondly it helps to get rid of parasites (mites and ticks). In the epidermis, which is generally consisted of *stratum basale*, *stratum granulosum,* and *stratum corneum*, during the process prior to molting in the reptiles that slough large pieces of cornified skin layer changes occur [8].

In snakes, the complete outer layer of skin is shed in one piece and layer. During molting, most animals also change their behavior, they prefer to hide or move to a safe place and refuse food. In snakes, a thin skin layer in the form of a thin transparent membrane (*spectaculum*) covers their eyes; therefore, before sloughing, their vision is the weakest, as they have cloudy eyes which become bluish in color. This affects their behavior, and because of their faint vision, they become more nervous. The snakes become restless and begin to rub on uneven surfaces [1]. Just before shedding, the color of the skin becomes dull, colorless, and dry looking and the eyes become cloudy or blue-colored. Skin sloughing depends on many factors, such as growth rate, season, hibernation, mating, etc. Molting is repeated periodically throughout a snake's life. Wild animals slough two to four times a year (younger, still growing snakes may shed up to four times a year and later only twice), which in captivity can occur more often. The most common complications in captivity occur due to reduced humidity in the vivarium. The skin has no role in changing the gases

**151**

**Figure 15.**

*Reptilian Skin and Its Special Histological Structures DOI: http://dx.doi.org/10.5772/intechopen.84212*

except in the marine snakes that alternate the gases through the skin. When sloughing, they help themselves by rubbing at different surfaces. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases, the cast skin peels backward over the body from head to tail, in one piece like an old sock. A new, larger, and brighter layer of skin forms underneath [14]. Snake scales are not discrete but are extensions of the epidermis; hence, they are not shed separately but are ejected as a complete contiguous outer layer of skin during each molt, similar to a sock being turned inside out. During the sloughing of the snake, the *stratum basale* is creating new cells, doubling *stratum granulosum* and *stratum corneum*. Specific to snakes and other reptiles is the formation of a *stratum intermedium*, a temporary layer between old and new skin. In this part of the skin, white blood cells help to separate layers and getting rid of the old layer of skin. Due to the pushing of old skin, the *stratum basale* is duplicated and after sloughing, the skin is up to 20% larger. Before the snakes shed the old skin, a new layer is already formed underneath it. The process of changing skin, takes about 2 weeks. As snakes grow, their skin cannot keep

up with their growth, so they occasionally shed the skin (**Figure 15**).

In the case of lizards, this coating is shed periodically, usually coming off in flakes, but in some cases, such as lizards having elongated bodies, in a single piece. Some geckos will eat their own shed skin. Ecdysis is controlled by the thyroid gland. Changes in feeding behavior and activity occur prior to ecdysis and the reptiles become very susceptible to dehydration. Snakes tend to shed the whole skin, unlike lizards and chelonians which shed pieces, which makes them more vulnerable during ecdysis. In a healthy snake, the whole process can take up to about

 *Mechanism of the ecdysis in snakes (adopted from Kardong [8], designed by Pia Cigler). In lizards and snakes, the shedding of the cornified layer is called molting or ecdysis and results in the removal of the superficial epidermis. As molting begins, stratum basale, which has given rise to the strata granulosum (inner) and corneum (outer), duplicates the deeper layers of granulosum and corneum, pushing up under the old layers. During ecdysis, the cells in the intermediate layer replicate to form a new three-layer epidermis. Once this process is complete, lymph and white blood cells diffuse into the area between the two layers, and enzymes are released to form cleavage zone at the separation line. At this phase, the snake becomes gray, and snakes and lizards without the eyelids are also blind, because cornea is also changed. The old skin is shed, and the new epithelium hardens, decreasing permeability to become a new skin. GL—germinative layer, IG—inner* 

*generation of epidermis, OG—outer generation of epidermis, SL—separation line, S—slough.*

#### *Reptilian Skin and Its Special Histological Structures DOI: http://dx.doi.org/10.5772/intechopen.84212*

*Veterinary Anatomy and Physiology*

dormant scutes are shed individually [14, 32].

pieces of cornified skin layer changes occur [8].

are called inframarginal scutes. Cranial from the first neural scutes it is nuchal plate. Above the tail are two scutes named suprapygeal (supracaudal). In the intramarginal plates, Rathke's pores are visible in sea turtles and similar structures can be observed in freshwater turtles. Below Rathke's pores, Rathe's glands are located, covered with fat tissue [31, 32]. The plastron is the nearly flat part of the shell structure of a turtle, which is basically the ventral surface of the shell. It also includes within its structure the anterior and posterior bridge struts and the bridge of the shell [32]. The plastron is made up of nine bones and the two epiplastra. The plastron usually consists of 12 plastral scutes, six on each side, which come together in the central line and their number depends on the shape of the shell and the type of turtle. Plastral formula is consisted from intergular, gular, humeral, pectoral, abdominal, femoral, and anal plastral scutes. The shape and mutual relationship of these scutes are of great importance in determining the species. In addition to the armor, turtles may also have specifically deployed jaw shells that may also be important in identifying the species. For example, in the sea turtles between the eyes, there are two horned shells that are characteristic of the Green sea turtle (*Chelonia mydas*), while in the other species there are more or only one. In the turtle, the

In some turtles, fragrant glands are open in the cloaca, and in some species, they produce an intensive smell, especially when they feel endangered. For most skin glands, it is considered to play a major role in reproduction or defense against predators. In the terrestrial turtles, glands are located only on the thighs, while in the water turtles, the mucous glands are found along the skin. During the hibernation of turtles, gas exchange occurs through the skin, while being buried in the ground or for example at the bottom of the lake. The turtles have developed lacrimal glands (*gll. lacrimalis*) and Harder's glands that, like lacrimal glands, produce tears and contain immunocompetent cells. In the sea turtles, the lacrimal gland has been altered and modified into the solitary gland. The turtles do not have nasolacri-

mal ducts (*ductus nasolacrimalis*) and tears are secreted by evaporation.

The shedding of scales is called *ecdysis*, trivially mostly named molting or sloughing. Sloughing serves number of functions. Firstly, the old and worn skin is replaced and secondly it helps to get rid of parasites (mites and ticks). In the epidermis, which is generally consisted of *stratum basale*, *stratum granulosum,* and *stratum corneum*, during the process prior to molting in the reptiles that slough large

In snakes, the complete outer layer of skin is shed in one piece and layer. During molting, most animals also change their behavior, they prefer to hide or move to a safe place and refuse food. In snakes, a thin skin layer in the form of a thin transparent membrane (*spectaculum*) covers their eyes; therefore, before sloughing, their vision is the weakest, as they have cloudy eyes which become bluish in color. This affects their behavior, and because of their faint vision, they become more nervous. The snakes become restless and begin to rub on uneven surfaces [1]. Just before shedding, the color of the skin becomes dull, colorless, and dry looking and the eyes become cloudy or blue-colored. Skin sloughing depends on many factors, such as growth rate, season, hibernation, mating, etc. Molting is repeated periodically throughout a snake's life. Wild animals slough two to four times a year (younger, still growing snakes may shed up to four times a year and later only twice), which in captivity can occur more often. The most common complications in captivity occur due to reduced humidity in the vivarium. The skin has no role in changing the gases

**150**

**7. Ecdysis**

except in the marine snakes that alternate the gases through the skin. When sloughing, they help themselves by rubbing at different surfaces. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases, the cast skin peels backward over the body from head to tail, in one piece like an old sock. A new, larger, and brighter layer of skin forms underneath [14].

Snake scales are not discrete but are extensions of the epidermis; hence, they are not shed separately but are ejected as a complete contiguous outer layer of skin during each molt, similar to a sock being turned inside out. During the sloughing of the snake, the *stratum basale* is creating new cells, doubling *stratum granulosum* and *stratum corneum*. Specific to snakes and other reptiles is the formation of a *stratum intermedium*, a temporary layer between old and new skin. In this part of the skin, white blood cells help to separate layers and getting rid of the old layer of skin. Due to the pushing of old skin, the *stratum basale* is duplicated and after sloughing, the skin is up to 20% larger. Before the snakes shed the old skin, a new layer is already formed underneath it. The process of changing skin, takes about 2 weeks. As snakes grow, their skin cannot keep up with their growth, so they occasionally shed the skin (**Figure 15**).

In the case of lizards, this coating is shed periodically, usually coming off in flakes, but in some cases, such as lizards having elongated bodies, in a single piece. Some geckos will eat their own shed skin. Ecdysis is controlled by the thyroid gland. Changes in feeding behavior and activity occur prior to ecdysis and the reptiles become very susceptible to dehydration. Snakes tend to shed the whole skin, unlike lizards and chelonians which shed pieces, which makes them more vulnerable during ecdysis. In a healthy snake, the whole process can take up to about

#### **Figure 15.**

 *Mechanism of the ecdysis in snakes (adopted from Kardong [8], designed by Pia Cigler). In lizards and snakes, the shedding of the cornified layer is called molting or ecdysis and results in the removal of the superficial epidermis. As molting begins, stratum basale, which has given rise to the strata granulosum (inner) and corneum (outer), duplicates the deeper layers of granulosum and corneum, pushing up under the old layers. During ecdysis, the cells in the intermediate layer replicate to form a new three-layer epidermis. Once this process is complete, lymph and white blood cells diffuse into the area between the two layers, and enzymes are released to form cleavage zone at the separation line. At this phase, the snake becomes gray, and snakes and lizards without the eyelids are also blind, because cornea is also changed. The old skin is shed, and the new epithelium hardens, decreasing permeability to become a new skin. GL—germinative layer, IG—inner generation of epidermis, OG—outer generation of epidermis, SL—separation line, S—slough.*

2 weeks [8, 32]. In turtles and crocodiles, sloughing of the skin arises to a lesser extent and it is comparable to that of birds and mammals, in whom small flakes fall off at irregular intervals and it takes longer periods.
