Scales are present, but these are fundamentally different from the dermal scales of fish. The reptilian scale usually lacks the bony under support or any significant structural contribution from the dermis.
Instead, it is a fold in the surface epidermis, hence, an epidermal scale. The junction between adjacent epidermal scales is the flexible hinge Figure 1. If the epidermal scale is large and plate-like, it is sometimes termed a scute. Additionally, epidermal scales may be modified into crests, spines, or horn-like processes. Although not usually associated with scales, dermal bone is present in many reptiles. The gastralia, a collection of bones in the abdominal area, are examples of these.
Where dermal bones support the epidermis, they are called osteoderms, plates of dermal bone located under the epidermal scales. Osteoderms are found in Crocodilians, some lizards, and some extinct reptiles. Some bones of the turtle shell are probably modified osteoderms. Germinal layer lies on the basal lamina a and below lies the tissue of the dermis.
The junction between epidermal scales is the flexible hinge adopted from Chang et al. Scales have many important functions, such as playing vital roles in skin permeability and providing protection from abrasion, and therefore tend to be thicker dorsally than ventrally.
In some species, they form into large plates and shields on the head. In snakes, they are widened ventrally to form gastropeges, which are important for locomotion [ 1 , 8 ]. Lizard scales vary in form from tubercular to plate-like or even largely overlapping each other in formation. The scales originate from the epidermal superficial layer of the skin and form keratinized wrinkles and may have bony plates underlying them osteoderms. They are very close to each other, and links between them allow them to move in all directions.
In lizards, scales can vary in form and be modified into crests, spikes, or horns, depending on the type of lizard and on the body part of the lizard and are often of use in taxonomically differentiating species. On the head and on the ventral part, scales are plate-shaped.
Scales are important to prevent water loss from the body, as well as to protect the body from injury, because the lizards touch the ground with the ventral surface of the body and thus damage the skin. The skin in the lizard does not follow the growth of the body, so they have to change it, which does not happen in one piece but in several smaller pieces [ 14 ]. In some lizards, it is characteristic that their fingers are covered with large scales.
These scales serve them to move easier as in the case of the basilisk lizard Basiliscus basiliscus , especially on the water surface or are helpful in the sand skink Neoseps reynoldsi to move in the sand. Geckos Gekkonidae have flattened fingers, characterized by around 20 leaf-like formations on the ventral side of the toes, named lamellas, with a structure that enables animals to climb on the vertical and very smooth surfaces Figure 2. Each seta branches to form a nanoarray of hundreds of spatular structures, which are 0.
The ventral view of a New Caledonian Giant Gecko Rhacodactylus leachianus climbing a vertical glass surface. On the ventral view of the foot of a New Caledonian Giant Gecko, a foot adhesive system is observed with adhesive lamellas which consist of microscale array of setae, which are together clustered in tetrads Photography, Valentina Kubale. The skin glands are mostly restricted to certain parts of the body.
Thus, in the medial side of the thighs of many lizards, for example, Green Iguana Iguana iguana , there are femoral pores, beneath which femoral glands are located.
These glands are larger and usually more developed in males. They secrete a waxed secretion that contains various pheromones relevant to the mating period or when the animal feels endangered. They also help to determine sex in these species [ 14 ].
The lizards do not have an external ear; however, in some species, they have a fold of the skin and tympanic membrane that can be seen from the side on the head in a shallow recess. This membrane is covered by a thin membrane in some species that is also changed in the process of ecdysis. Some lizards such as Green Iguana Iguana iguana have partial third eye. This organ is a superficial parietal gland which also contains a lens, cornea, and retina, and is located immediately below the skin in the parietal opening between the parietal and frontal bones.
The partial eye is a cavitary organ, which is constructed from epithelial cells that contain secretion glands and photoreceptors that convert light stimuli into neuroendocrine messages that can play an important role in thermoregulation but also in hormone production [ 16 ]. Lizard skin contains classical skin layers, which can vary in morphology at different positions. Here, we compare skin of the Leopard Gecko Eublepharis macularius Figure 3 with the skin of the Green Iguana Iguana iguana Figure 4 , both sampled from the dorsal region.
The second most prominent feature observed are the melanocytes, where in the Green Iguana the melanocytes are hardly seen at all. On the other hand, Leopard Geckos can vary very much in color and they exist in various color mutations termed morphs. Our sample originates from the most common one, which is basic yellow in color with black spots, which also contains more melanophores. Other morphs include the high yellow less black spots , hypomelanistic with ten or less dark spots on the body or on the other hand hypermelanistic, which has darker pigmentation but is not black in color.
Blizzards are morphs that are completely pattern less. The lavender Gecko has light violet or lavender color included, the tangerine one has an orange color included in its coloration, the carrot tail has orange color on the tail and there are some more variations in color also present in different geckos [ 14 ].
The sample was taken in the resting stage of the epidermis, when the animal was not in the process of ecdysis. In epidermis, the most visible part is the basal layer with keratinocytes with nuclei, which are dividing by mitosis. In the figure is the part with overlapping scale. The intervening mature stratum mesos consists of a few layers of cells, which are often not very well seen under this magnification. In the dermis, fibrous connective tissue, vessels, nerves, melanophores, and Merkel mechanoreceptor cells are observed.
In epidermis, different layers are observed. The stratum granulosum is not very clearly distinguishable with the nuclei. In the dermis, fibrous connective tissue, vessels, and nerves are observed. Especially important for camouflage mimicry is the skin color. Skin color is susceptible to changes depending on the amount of sunlight and it may be darker or lighter.
Chromatophores are pigment-containing cells found in the dermis of the skin and provide a large range of colors by changing the position of their granules. This ability is particularly significant for the chameleons, although it is also observed to a lesser extent in other types of lizards, such as the New Caledonian Giant Gecko Figure 5 , and in some species when light and temperature influence change of skin color to more pronounced such as in the Saharan Uromastyx Uromastyx geyri Figure 6.
These pigment cells are not just confined to skin but can also occur in the peritoneum of some species, for example in turtles. Animals of the same species during breeding may, due to different mutations, change their basic color and thus produce offspring with new patterns, which are new morphs.
Different color of the skin in the New Caledonian Giant Gecko caused by environment Rhacodactylus leachianus in the same species Photography, Pia Cigler. Different color of the skin in the Saharan Uromastyx Uromastyx geyri influenced by temperature and sunlight Photography, Pia Cigler. Chameleons are an extreme example group of lizards, and, of all the reptiles, they have the highest ability in relation to changing their skin coloration and pattern through combinations of pink, blue, red, orange, green, black, brown, light blue, yellow, turquoise, and purple [ 19 ].
Chameleons change skin color depending on the temperature of the surrounding area, their physical condition, intraspecies signaling and communication. Color change is also important for their camouflage. Chameleons tend to show brighter colors when displaying aggression to other chameleons, and darker colors when they signal they are not fighting [ 20 ]. Chameleons transform color by changing the space between the guanine crystals which are present in specialized cells named chromatophores.
The color change is based upon the wavelength of light reflected off of the crystals. The skin of the chameleons is as in other reptiles consisting of epidermis, dermis, and hypodermis.
The important features chameleons have regarding skin color are located in the dermis. It is within the dermis that the blood vessels, nerves, skin muscles, and special cells named chromatophores are present. The chromatophores contain guanine crystals and are subdivided into differing types including iridophores, xanthophores, erythrophores, guanophores, and melanophores Figure 7.
Chromatophores in reptiles Chameleons adapted from Krey and Farayalah [ 21 ] and designed by Pia Cigler. Different chromatophores lie in the different layers of the epidermis and dermis.
Keratin layer, B. Xanthophores, C. Erythrophores, D. Guanophores, E. The three figures show how coloration is achieved through their extensions. The iridophores granulophores lie in the dermis. They are the most important for true color change, not just changing shades of the same color. They contain semicrystalline nanocrystals of the amino acid guanine the breakdown of uric acid that reflects light.
They are arranged in a network in a surface and in a deeper layer. In the deeper layer, iridophore crystals have a protective role for the organism against harmful rays. At the surface of the iridophore, smaller crystals are located, which can diffract different wavelengths of light, depending on their arrangement and density.
The blue wavelengths are reflected more to produce a blue coloration in an effect called Tyndall scattering. When combined with the yellow carotenoids, they emit green color, which is a common camouflage in many reptiles [ 9 ]. Guanophores contain a colorless crystalline substance called guanin and reflect among others the blue part of light. Xanthophores produce the pigments called pteridines and are important for yellow shades of the skin.
Erythrophores contain the pigment carotene, which they get from the other parts of the body and are important for shades of red. Both types of cells are located above the iridophores and when they cover each other they can form different color combinations.
Green color is the consequence of the yellow pigment which covers the refracted blue color coming from iridophores. Melanophores produce the pigment melanin and they lie the deepest within the dermis.
Pigment melanin-containing cells give rise to black, brown, yellow, and gray coloration. Albinism in reptiles is caused by lack of melanin. The carotenoid cells are found beneath the epidermis above the melanophores and produce yellow, red, and orange pigments [ 9 ], so albino reptiles are often yellow to orange color.
Here might lie another part of the reason for the prevalence of five: pleiotropy, or the multiple effects of genes upon more than one physical characteristic. For instance, Hand-Foot-Genital syndrome is a rare condition in which, as the name implies, the genito-urinary tract and the limbs are malformed. Crucially, the genes responsible are within the set of those involved in digit number and patterning. Therefore, although this tells us nothing directly about the significance of digit number, it indicates something important about developmental stability: the mechanisms involved in patterning the tips of our limbs include those involved in our reproductive success.
Thus, tweak at your peril. Sign up for our email newsletter. Already a subscriber? Sign in. Thanks for reading Scientific American. Terry Philbin, an orthopedic surgeon, why we have them. We walk with a heel-first gait, so the heel absorbs the shock, then the toes help push you off for the next step. The human foot is quite different from that of the chimpanzee, according to Scientific American : "A major difference between the two stems from flexibility.
The former's foot is adapted for a stiff push-off which is necessary for bipedal locomotion. The latter's feet maintain greater flexibility overall and grasping abilities that enable climbing trees as well quadrupedalism on the ground. Short, thick toes are ideal for bipedal walking and running. According to Steve Gschmeissner , the photographer of a photo of a mosquito's foot that won entry into the Royal Photographic Society's International Images for Science contest in , the scales that cover most of a mosquito's body are especially dense on the leg.
He told Live Science that these scales "help protect the limb and enable the mosquito to land on water, where these insects lay their eggs. Mountain goats have cloven hooves with two spread-out toes that help with balance. Rough pads on the bottom of each toe "provide the grip of a natural climbing shoe," according to National Geographic.
Mountain goats' hooves are unique in the world of cloven hooves, wildlife researcher Stefan Pociask told Forbes. What results is a hard covering on top, a soft bottom, and surrounding the soft sole, a hard edge that touches the ground This is what allows them to be rock climbers. Pociask also explained to Forbes that when a goat places one of its hooves down, "the pad makes first contact over a larger area, and through the sense of touch, this gives the mountain goat more information as to what he is about to step on, and more opportunity to adjust as needed.
The large surface area and the sensory feedback allow the goat to adjust to its rocky environment. Cats are digitigrade walkers , meaning they walk on the balls of their feet.
The small, soft, and sensitive pads on their paws help cats assess their environments and move silently, allowing them to hunt. Cats are known for landing on their feet after big jumps, but it took nearly all of their evolutionary history to achieve that feat. Cats lack a collarbone, have six more vertebrae than humans do, and are equipped with a strong inner-ear compass that helps them reorient themselves. All these features help the animals correct their positions mid-fall.
According Mother Nature Network, kittens start learning to fall and perfecting their " righting reflex " at about seven weeks. As such, they carry many names: Venezuelans call them the arrau; in Colombia and Peru they are known as charapa; in Brazil they are called tartaruga and tartaruga da Amazonia.
The South American river turtle, historically, are social creatures who gather in groups that can range of a group of ten to a group of over a hundred or even a thousand. Unfortunately, this ingrained behavior made them easy pickings for poaching. Their eggs and hatchlings were also prized by poachers, and at the height of harvesting around 48 million eggs were taken every year by poachers.
Much like many other tortoises and turtles, the South American yellow-footed tortoise suffers from the predatory nature of humans. These tortoises suffer from habitat devastation, but they are also poached for their meat—which is considered a delicacy—as well as their shells. At this moment, they are considered vulnerable to extinction. On average, they grow to be around pounds with males growing to an average of 16 inches and females growing up to inches.
Some exceptional tortoises can grow to over 36 inches in length and reach up to pounds. These tortoises are all about body language! They do not need their hands to form a complex sign-language. Instead, they use rapid head movements to communicate with each other.
As they mate year round, males are always on the lookout for a receptive female. They distinguish male from female by looking out for head movements. Apparently, these male tortoises find the qualities of being silent and still attractive in their potential female mates.
Fer-de-lances are venomous vipers with a combative, deadly strike and impressive size. Living in forested areas throughout the Amazon as well as banana plantations, their coils can easily be camouflaged among the surrounding environment.
The fer-de-lance is recognized as a pit viper as a deep, heat-detecting pit lies visibly between each eye and nostril. The fer-de-lance is widely adapted throughout Central and South America. Their widespread populations are potentially unfortunate for humans, who suffer more deaths at the bite of this particular viper than any other snake. Skip to main content. Google Tag Manager. FUN FACT: Not only are basilisks not the servants of dark lords, but they are actually known as the Jesus Christ lizard for their remarkable ability to walk on water…or run on water, we should say.
FUN FACT: Unless you happen to be a male anaconda looking to procreate, the anaconda breeding ball is one ball you do not want an invitation to. FUN FACT: Black caimans were considered a critically endangered species in the s, by which time they had been severely overhunted for their skins. FUN FACT: The South American river turtle, historically, are social creatures who gather in groups that can range of a group of ten to a group of over a hundred or even a thousand.
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