Melissa
Kaplan's
Herp Care Collection
Last updated
April 19, 2007
Reptile Skin Basics
Construction, Infections, and Color
©2000 Melissa Kaplan
Skin
Construction
Reptile skin
has some things in common with mammal skin...and some things that are
are not. Iguanas differ from other reptiles in that their pus, while made
of the same things as mammalian and other reptilian pus, is solid, rather
than flowing. Reptile
skin (integument) is comprised of two main layers, the epidermis and the
dermis.
Epidermis: characterized by complete covering of keratin (the same stuff that makes up mammalian hair and mammalian, avian, and reptilian nails/claws also makes up the plates we call "scales"). The keratin may be thick, as on the belly and tail, or thin, as on the dewlap. The hard spikes on such lizards as bearded dragons and horned lizards are just harder bits of integument, as are the keeled ridges on many snakes' scales and some lizards, such as some iguanas. The keratin is composed of many layers of very thin, flat cells. The closer they get to the surface of the reptile, the more highly compacted they are as they are pressed against by new keratin cells being formed lower down in the epidermal layer, the stratum germinativum. Three such layers of increasingly compacted keratin cells are formed, called, from the surface inward toward the stratum germinativum, the Oberhautchen layer, the beta-keratin layer, and the alpha-keratin. Some reference the epidermis as being three layers:
Stratum corneum: heavily keratinized outer layer.
Intermediate zone: composed of stratum germinativum cells in various stages of development.
Stratum germinativum: the deepest layer, consisting of cuboidal cells. Undergoes mitosis to form the intermediate zone.
During shedding (ecdysis), the mitosis in the stratum germinativum forms the new cells moved up to the intermediate zone and those cells up to the stratum corneum. It is during this time that the skin is metabolically active and it in this period of activity that healing will occur. Otherwise, skin is essentially inert.
Exception to the norm... The exception to the above is the chelonians. Their shell, which many people think is just bone, is actually covered with living tissue composed of keratinized epidermis covering the underlying dermal plate which is itself the chelonians vertebrae and rib cage. (Thus, the practice of piercing a chelonians's shell to put a ring in with which to tether chelonian (which is in itself inhumane), or to decorate it with stud earrings, is akin to our puncturing our skulls.)
Dermis: consists of connective tissue. In some reptiles, there may be small bones called osteoderms. These are what form the distinctive specialized scales on savannah monitors and crocodilians, for example.
Reptile skin heals much more slowly than mammalian skin, often taking about 6 weeks for the defect to be fully restored.
Infections
Reptiles,
being reptiles, do not have hair follicles. Not having hair follicles
means they don't get complications that hair follicles get - like acne
(pimples). Since they don't have these oil-producing follicles nor the
bacteria and things which live inside the follicles, there are no follicles
to get plugged with dirt or oil - so, no "pimples." Lumps and
bumps, then, though they may be filled with pus, are not to be treated
like an occasional pimple, but like the potentially dangerous bacterial
or parasitic infection that they really are.
Noted reptile vet John V. Rossi, in his chapter on Dermatology in Mader's book, Reptile Medicine and Surgery (pp. 104-117), notes the following skin conditions encountered in reptiles that may be described by reptile keepers as "lumps", "bumps" or "scrapes".
Abscess: most common dermatologic problem seen in reptiles; a variety of gram-negative bacteria are involved in these infections. Reptiles do not have the enzymes required to break down these masses, so the mass must be surgically removed (including the use of sterile instruments in a sterile field) and appropriate antibiotics administered. Carbuncles, another condition, is one of multiple abscesses connected by sinuses which may invade deeper into the underlying tissues.
Abrasions: a traumatic removal of the epidermis, such as when the reptile tries to escape through a too-small opening in his enclosure, or a turtle scrapes against an inappropriate rock, such as lava rock. Abrasions from repeated trauma, such as rostral rubbing or snout-banging may become infected, turning into abscesses.
Blisters/Bullae: The difference between the two is simply a matter of size. In both cases, they result from being kept in an environment that is too moist (terrestrial reptiles), or dirty water (aquatic and semi-aquatic turtles). While they may be free of bacteria when first formed, when they break, they permit bacteria to enter through the resulting defect, which can lead to localized infection or septicemia ("blood poisoning", or system-wide infection).
Crusts: dried intracellular fluid, blood and other matter that forms on top of a laceration or abrasion. Before these areas dry and become crusty, they will be seen and felt as a thin, wet, clear or yellowish fluid.
Cysts: these large, fluid filled structures are most commonly associated with subcutaneous parasites, such as tapeworm. Other causes include the traumatic separation of the epidermis from the dermis below, burns, or other severe trauma.
Discoloration: when not associated with stress, breeding season, bruise or shedding, they signal a bacterial or fungal infection, one that may be affecting just the skin, or may be systemic in nature. Both require immediate diagnosis and appropriate treatment.
Edema: some localized swelling may occur at an injection site or after some dewormers.
Nodules: granulomas which are usually associated with many kinds of infection, from bacteria, fungi or parasites. In order to appropriately treat the underlying condition, proper diagnosis must be made.
Parasites: besides ticks and mites, there are various endoparasites which live part of their life cycle inside the host, and then migrate outwards, through organs and tissues, to form small nodes or bumps under the skin, which may or may not create exudates or crusts. The parasite does cause an irritation, which, when in its usual host, will cause the host to rub up against something to 'scratch the itch'. This serves to break open the already inflamed skin, freeing the parasite to move on to its next stage. With the lack of proper quarantine and generally filthy conditions endemic in the pet trade, animals - and humans - are coming into contact with, and playing host to, parasites which don't normally inhabit them. This can result in a parasitic nodule sitting under the skin, causing an inflammatory reaction. If not removed properly, it can cause stress, leading to infection...or infect the human who carelessly picks at it.
Patches of skin color/texture change: may be associated with fungi or bacterial infections, necessitating proper diagnosis to determine the required treatment.
The skin is the body's largest organ and plays an important role in keeping the body healthy. The skin of all vertebrates serves to keep bodily fluids in the body, and keep bacteria, fungi, and parasitic organisms that don't belong in the body out of it. When a problem occurs in the skin, it is important that it be properly evaluated.
Wound healing, while it takes longer in reptiles, is similar to that of mammals: a mix of proteinaceous fluid and fibrin start to form in the defect, filling it in and forming a scab. Epithelial cells start to move into the area under the scab, forming a thin layer. As these cells increase in number, the layer thickens. While this is going on, macrophages and heterophils, the body's clean-up crew, move in under the scab layer and clean up bacteria and cellular debris. Since the most rapid period of growth and repair is during the shed period, which occurs every 4-6 weeks in a healthy reptile (and may occur more frequently over and immediately around the site of an abscess or wound), sutures should, if possible, be left in place for at least 4-6 weeks or until after the next shed, if the reptile starts a shed within a week or so after the surgical procedure.
Interesting note... Wounds and incisions that are oriented cranially-caudally (lined up in the direction from head to tail) heal faster than transverse (side-to-side) ones.
New reptile owners who try to get answers by email or posts in forums, or even by posting pictures, are just wasting what may be precious time: they need to get their reptile to a reptile vet for proper diagnosis, treatment, and learn what they may need to fix in the reptile's captive environment to ensure that the condition heals uneventfully and does not occur again.
A
Note On Sutures
Some of the sutures used
in stitching up inside the iguana as well as on the skin surface are "dissolving"
stitches. That is, over a period of time, they dissolve away and fall
out. They do not always fall out, even though they may have dissolved
under the epidermis. These stitches should be removed to prevent them
getting caught on anything - or falling out and being ingested by the
reptile, child or pet.
Sutures placed in the gastrointestinal tract may end up passing through the intestine and cecum, being excreted with the urates and feces. Or, they may lodge in the tract, kidney or bladder. If the latter occurs, uric acid stones may form around them. This can cause impaction or difficulty voiding wastes, or they may lodge high enough in the cecum or intestine that they require surgery to remove them.
Color
(or why an albino isn't always an albino)
Really, there
ought to be truth-in-advertising when it comes to calling any reptile
who is missing most - but not all - of its skin pigments "albino."
What triggered the addition of this section in my reptile skin article
is yet another "albino" iguana for sale, this one for $8,000.
Like a lot of breeders and importers who end up with an unusual color
morph, they are quick - but not accurate - in slapping an 'albino' label
on it.
Albinism is the lack of melanin in the skin so the skin is white or pinkish (from the circulating blood). Since pigments give the eyes their color, albinos have red eyes (so colored from the blood vessels in the eye). Photos of this $8,000 "albino" and others I've seen clearly show that they are not albinos. This one is clearly very light green and has light brown eyes. That means he is has some green (made of yellow and blue chromatophores) and very little melanin - enough to color the eyes brown and create the darker stripes along the tail. The few other "albino" iguanas for sale throughout the last several years were similar to this one or had even less of the blue, making them yellow and white with blue eyes.
In general, reptiles have two sets of cells that produce color, the melanocytes and the chromatophores:
Melanocytes are present throughout the basal layers of the epidermis. During the skin-renewal phase of epidermal growth, the melanocytes send pseudopodia into the melanin-bearing keratocytes to transfer the melanin to the new cells. In crocodilians, iguanids and snakes, these melanin-bearing keratocytes are in the ß-layer; in other reptiles, they occur in both the a- and ß-layer.
The chromatophores are layered upon one another in the outer portion of the dermis. A layer of xanthophores (yellow pigment cells) erythrophores (reddish-purple pigment cells) and other fat-soluble pigment cells lay just under the basal membrane of the epidermal layer. Under the xanthophores are several layers of iridiophores which produce iridescent colors in the range from blue to gold, as well as white (guanophores and leucophores).
The presence or absence, and density and distribution when present, of the melanocytes and chromatophores within each layer will determine the color of the reptile - not some breeder slapping an "albino" label on it. In some static-colored species, the stacks of chromatophores are absent.
Related Articles
Blackening Skin/Blackening Skin Syndrome/Vesicular Dermatitis
Shell-Rot in Turtles and Tortoises
Small oozing bumps and lesions on reptiles
Tail, Digit, Limb and Skin Autotomy
References:
Bennett, AR and Mader DR. 1996. Soft Tissue Surgery. In, Reptile Medicine and Surgery. Douglas R. Mader, editor. WB Saunders, NY.
Marsden, Anne. 2000. IML/AIML postings.
Rossi, JV. 1996. Dermatology. In, Reptile Medicine and Surgery. Douglas R. Mader, editor. WB Saunders, NY.
Zug, GR. 1993. Herpetology: An introductory biology of amphibians and reptiles. Academic Press, NY.
