Lizards Flashcards
What are the two large subgroups of lizard taxonomy? What families are within each group?
Iguania
- Agamidae
- Chamaelionidae
- Iguanidae
Scleroglossa
- Nyctisaura - Gekkonidae, Amphisbaenidae (worm lizards)
- Diploglossa
- Scincidae - largest family
- Anguimorpha
- Anguidae - glass & legless lizards
- Varoindae
- Helodermatidae
- Varanidae
- Lanthanotidae - earless monitor lizards
How do lizards shed? What factors affect shedding?
Describe the glands found in lizards. Are they sex-linked?
What provides the pigmentation to the skin in lizards? What are they composed of?
What species have osteoderms?
How do gecko’s climb so well?
- Integument
- Thick, keratinized skin with ectodermal scales (formed by folding of the epidermis and outer dermal layers)
- Lizards typically shed in small pieces - exception is geckos that shed all at once
- Factors that affect shedding:
- Species, size, temperature, humidity, state of nutrition, age, sex, growth rate, skin damage (trauma, surgery, infection), health status, endocrine factors
- Glands are more developed in males
- Femoral pores in iguanas and many agamids
- V-shaped pre-cloacal glands in many geckos and agamids
- Not true glands, just skin invaginations that produce waxy substance
- Chromatophores change size and positioning in the dermis some species (chameleons, anoles)
- Melanophores - melanin
- Erythrophores
- Xanthophores - pteridines, carotenoids
- Iridophores - reflective platelets of guanine, adenine, hypoxanthine, urica cid
- Osteoderms are dermal bones that support epidermal scales
- Present in Heliodermata and some skinks, legless lizards, and girdle-tailed lizards
- Gecko feet have adhesive setae for climbing
Describe the anatomy of the lizard heart.
Describe the flow of blood through the lizard heart.
Where is the heart located? Does it vary by species?
Describe the renal portal system. How is it clinically relevant?
- Cardiovascular System
- Three chambers = right atria + left atria + single ventricle
- Single ventricle = cavum venosum + cavum arteiosum + cavum pulmonale
- Blood flow: Venous blood → right atrium → cavum vensoum → cavum pulmonale → pulmonary artery → lungs → left atrium → cavum arteriosum → atrioventricular valve → cavum venosum → aortic arches x 2
- Heart is within the pectoral girdles except monitors and tegus, where it is more caudal
- Renal portal system: blood from the tail and some from the hind limbs flows directly to kidneys
- Decreased serum concentration if you inject drugs that are cleared via tubular secretion in the caudal half of the body, but unknown clinical significance
- Can increase nephrotoxicity of aminoglycosides administered in the caudal half of the body
- The postcava can shunt blood past the kidneys
- Baroreceptor control of hypotension is not affected by temperature
- Normal blood pressure in brumation
How do salt glands work? What species have them?
How does glottis location vary by species of lizard?
What kind of tracheal rings do lizards have.
Describe the lung anatomy of lizards. How does it vary by species - Skinks, Varanids, Chameleons?
How does inspiration occur without a diaphragm?
What is unique about monitor respiration?
What stimulates lizards to breathe?
- Respiratory System
- Nasal salt glands in herbivorous iguanids excrete concentrations high in Na and K
- May be more important for osmoregulation than kidneys
- Glottis is rostral in monitors caudally in agamids
- Closed only during inspiration and expiration
- Incomplete tracheal rings that bifurcates at the level of the heart
- Lungs
- Primitive Lizards have a hollow single chamber lined with faveoi (spongelike)
- Skinks have large caudal nonrespiratory sacs that are thin-welled and poorly vascularized
- Advanced lizards have interconnected chambers that are divided by a few septae
- A membrane connects to the pericardium
- Chameleons have hollow fingelike projections at the margins of the lungs
- Used for inflation, not air exchange
- Monitor lizards have multiple lung chambers and primary and tertiary bronchi
- Inspiration is voluntarily controlled by intercostal muscles and coelomic wall muscles
- No diaphragm but monitors and gilas have a fascial layer to separate thorax and coelom
- Require ventilation when anesthetized
- Monitors have unidirectional airflow
- Fluttering of the ventral throat moves air in oropharynx for cooling and olfaction
- No a significant part of respiration
- Control of Respiration
- CO2 and O2 chemoreceptors in periphery
- Increased CO2 (not O2) is the primary drive to breathe
- Pulmonary stretch receptors suppress inspiration and increase expiration
- Nasal salt glands in herbivorous iguanids excrete concentrations high in Na and K
What are the two dental patterns of lizards? List the families that have each type.
What lizards have venom?
Describe the intestinal anatomy of herbivorous lizards.
Is stone ingestion normal?
Describe the appearance of the liver. What process may lead to a light gray appearance?
- Digestive System
- Dentition
- Pleurodont: teeth attached to the lingual side of the mandible without sockets
- Iguanids and varanids
- Shed and replaced (odd-numbered teeth, then even-numbered)
- Periodontal disease has not been reported with this dentition
- Acrodont: teeth attached to the biting surface of the jaws without sockets
- No replacement, though may add some to the back as the animals grows
- Agamids and Chamaeleonidae
- Pleurodont: teeth attached to the lingual side of the mandible without sockets
- Gustatation
- In fleshy tongues, many taste buds in tongue and in pharynx
- Protrusion of tongue controlled by hyoid apparatus
- Monitors and tegus have a keratinized tongue with few taste buds
- Forked tongues bring scent particles to vomeronasal (Jacobson’s) organ
- Tip of agamid and iguanid tongues is naturally darker (not a lesion
- Paired openings to vomeronasal organ at the roof of the mouth
- In fleshy tongues, many taste buds in tongue and in pharynx
- Venom
- Gila monsters and Mexican beaded lizard have sublingual venom glands that indirectly move venom into prey through grooves in the teeth with mastication
- Symptoms: pain, hypotension, tachycardia, nasua, vomiting
- Some varanids and iguanas also have venom that affects coagulation
- Stomach
- C-shaped with a fundic and parapyloric regions +/- cardia +/- rugae
- Stone ingestion is not normal - except in marine iguanas
- Intestines
- Herbivores have long intestines and an obvious colon
- Species with a large, sacculated colon for fermentation: green iguana, prehensile-tailed skink, Egyptian spiny-tailed lizard, and chuckwalla
- Cloaca = coprodeum (collects feces) + urodeum (urinary waste and sexual structures) + proctodeum (final chamber before the vent
- Cloacocolonic region is important for reabsorption for electrolytes and fluids from feces
- Liver is bilobed (R>L) with a gallbladder
- Some lizard species may have a disant gall bladder (similar to snakes)
- Normal mahogany color - chronic disease increased melanomacrophages create light gray appearance.
- Dentition
List at least 5 dimorphisms that may indicate a lizard is male.
How can you confirm?
What is the groove that sperm travels down in the hemipenes?
Parthenogenesis is reported in what lizard groups?
- Reproductive System
- During breeding season, testicles increase in size and males are more aggressive
- Signs that your lizard may be a boy:
- Taller dorsal spine
- Larger dewlap
- Larger operculum scales
- Elaborate head ornamentation (chameleons)
- Brighter colors
- Larger body size
- Hemipenal bulges
- Enlarged femoral and precloacal pores
- Ways to evaluate for hemipenes:
- Probing
- Eversion with gentle pressure (avoid in lizards with tail autonomy)
- Transillumination
- Radiograph for possible calcification
- Hemipene contrast radiography
- Ultrasonography
- Male Sex Organs = testes, epidymides, vasa deferens, hemipenes
- Sulcus spermaticus = groove in hemipenes that sperms run down into the female
- Retractor hemipenis = muscles that retracts everted hemipenes after copulation
- Female Sex Organs = ovaries, oviducts
- Internal fertilization
- Sperm storage can occur
- Can be oviparous or viviparous
- Parthenogenesis: female gamete develops into a new individual without being fertilized by a male gamete
- Occurs in several all-female species of lizards
- May be an incidental occurrence in other lizard species, like Komodo dragons
- Parthenogenesis reported in lizards, especially Cnemidophorus
- Gekkonidae and Komodo dragons can also reproduce asexually
Where are the kidneys located in lizards? Does this vary?
What renal structures are missing?
What groups of lizards have a sexual segment?
What lizards lack a urinary bladder?
- Urinary System
- Metaneprhic, paired, elongated, and slightly lobulated
- Lack a loop of Henle, renal pelvis
- Have fewer nephrons than mammals
- Located retrocoelomically in dorsal coelom (chameleons, varanids) or in pelvic canal (agamids, iguanids)
- In some male geckos, skinks, and iguanids, posterior kidney is called the sexual segment because it has distal tubular hypertrophy, becomes swollen during breeding season, and contributes to seminal fluid
- Reptiles can excrete nitrogenous waste as…
- Uric acid - primary route
- Urea: High water loss
- Ammonia: High water loss
- Bladder
- Urinary waste cannot be used to determine renal function
- Urine cannot be concentrated about plasma
- Bladder can absorb water
- Lacking in some agamids, varanids, Crotophylus, Cleropus, and geckos
- Urine stored in distal colon
- Urinary waste is not sterile because it flows into the urodeum, then the bladder
- Urinary waste cannot be used to determine renal function
- Metaneprhic, paired, elongated, and slightly lobulated
How does the lizard manidble differ from the snake mandible?
How does legless lizard anatomy differ from snakes?
How many phalanges on each toe?
What is unique about chameleon feet?
How does tail autotomy occur?
- Musculoskeletal System
- Fused mandibular symphysis (unlike in snakes)
- Legless lizards have lost leg long bones but retained pectoral and pelvic girdles
- Phalanges
- Front: 2-3-4-5-3
- Hind: 2-3-4-5-4
- Chameleons have zygodactyl feet with digits 1,2, and 3 opposing 4 and 5
- Development of fracture planes associated with autotomy and regrowth of tail in several species
- Autotomy can occur at various levels except where caudal vertebrae are associated with extrinsic caudofemoralis longus muscle (primary extensor of the hip joint) and cranial tail where hemipenes, fat deposits, and other structures are present.
- Regenerated tail skin is generally darker, muscle is pale and lacks well defined septa and quadrants
- Caudal vertebrae are replaced by a cartilaginous tube that may become mineralized but vertebral bones do not regrow
How many cranial nerves do lizards have?
How does the spinal cord anatomy differ from mammals?
- Nervous System
- Brain: Forebrain + hindbrain
- 12 cranial nerves
- Spinal cord extends to tail tip (different from mammals)
- No subarachnoid space = no myelography
Describe the ear anatomy of lizards. How many auditory ossicles do they have?
The iris of lizards is composed of what type of muscle?
Do lizards have a PLR?
What is unique about the lizard cornea?
Describe what you may find on your fundic examination of a lizard.
- Special Senses
- Ear is covered in transparent skin (except for earless and horned lizards in which it is covered with a scale)
- Two auditory ossicles (mammals have three) = stapes and extra columella
- Inner ear = two sacs with a broad passage
- Utriculus = three semicircular canals arranged perpendicular to each other
- Eustachian tube connects the middle ear to the dorsolateral pharynx
- Iris = striated muscle
- Muscles of the ciliary body change the lens shape
- Consensual PLR is absent
- Cornea lacks a Descemet’s membrane
- Retina is avascular;
- Conus papillaris = large vascular body that protrudes into the vitreous
- Fovea centralis = depression in the retina that improves visual acuity (diurnal species)
- Parietal eye on dorsal midline in iguanas
- Connects neurologically ot the pineal body
- Regulates circadian rhythms
- Ear is covered in transparent skin (except for earless and horned lizards in which it is covered with a scale)
What is unique about the tongue of chameleons?
How do their tongues function?
- Tongues.
- Chameleons – Over full body length, sticky fleshy tip for capturing prey.
- Supported and propelled or retracted by specialized lingual muscles, the hyobranchial apparatus, and elastic collagen tissues.
- Chameleons – Over full body length, sticky fleshy tip for capturing prey.
Describe the ideal housing set up for lizards (generally).
- Housing Requirements
- Lizards need large cages for their active lifestyle
- Horizontal dimensions are more important than vertical height for terrestrial species
- Cages may be made from glass, acrylic, timber, assorted plastics, fiberglass, and wire
- Caiman lizards require water to fully submerge in
- Do not use sand (obstruction) or redwood/cedar bark (oils damage respiratory system)
- Some species require vertical branches
- Require access to a thermal gradient within POTZ, also for light and humidity.
- Minimum acceptable size for enclosure varies, but bigger is better in most cases.
- Multiple comfortable resting spots, orientation of the cage should be appropriate for reflecting habitats of that spp.
- Important the lizard can choose appropriate temp, humidity, light exposure and feel safe and secure.
- Basking spots need to be secure enough for them to feel comfortable using them.
- Some lizards will choose thermal needs over exposure to UVB, artificial light and heat sources should be combined when possible.
- Lizards need large cages for their active lifestyle
- Outdoor Enclosures
- Have a thermostat to regular heating sources and gradient
- Full spectrum UV light is important for vitamin D synthesis
Describe the feeding strategies of lizards. Are there any specialists?
Describe the feeding of herbivorous lizards.
Describe the feeding of insectivorous lizards.
What are some common nutritional issues? How can those be addressed?
- Feeding and Nutrition
- Carnivores, insectivores, herbivores, omnivores.
- Caiman lizard feed exclusively on snails in wild.
- Horned lizards exclusively ants and termites.
- Marine iguanas – marine vegetation.
- Feed herbivorous lizards dark, leafy greens
- Limit fruit and goitrogenic vegetables
- Feed insectivores crickets that have been gut-loaded for 4 days
- Apply supplements to prey regularly for young animals
- Chameleons may need to be hand fed
- Feeding fibrous insects and food can decrease incidence of periodontal disease in agamids
- Feed carnivores whole, dead prey
- Obesity is common. Also orthopedic disease, CV disease, GI and repro dysfunction appear releated to obesity.
- Limit caloric intake and maximize physical activity in captive animals.
- Carnivores, insectivores, herbivores, omnivores.
Describe surgery of the reproductive tract in lizards.
Describe the management of limb or tail amputations in lizards.
How shoudl abscesses be treated?
- Surgery (F8):
- Surgery of the female repro tract often necessary to address problems ranging from preovulatory follicular stasis to egg-binding or dystocia.
- Ovariectomy or ovariosalpingectomy is often performed as a preventive measure in captive lizards not intended for breeding.
- Complete removal of all ovarian tissue is paramount.
- If left behind, itsue may regenerate and ovulation may resume, resulting in peritonitis.
- Amputations – Limbs or tail.
- Tail – Important to know if spp is capable of autotomy.
- If so, skin should be left open if tail regrowth is desired.
- If no ta spp that is capable of autotomy, skin should be closed to expedite healing.
- Lizards do well with limb amputations but avoid leaving stumps that could be traumatized.
- Generally have to amputate at the coxofemoral or scapulohumeral joints.
- Tail – Important to know if spp is capable of autotomy.
- Abscesses should be treated as surgical.
- Removal of abscess and capsule is necessary.
- Debride and treat topically if full excision not possible.
- Cytology, histo, culture and sensitivity should be performed.
Describe the two main approaches to lizard coeliotomy.
What are the concerns with the ventral abdominal vein?
Describe the closure
- Mader Ch. 98 – Lizard Celiotomy:
- Fasting recommended to minimize the size of GIT
- Two basic approaches to the coelom in lizards:
- Ventral coeliotomy (midline and paramedian)
- Preferred approach for most species
- Most common
- Lateral (flank) coeliotomy
- Used primarily for laterally compressed lizards such as old-world chameleons
- Ventral coeliotomy (midline and paramedian)
- Paramedian approach - incision parallel and lateral to midline then blunt dissect thin musculature
- Allows to surgeon to avoid and identify ventral abdominal vein
- Midline celiotomy
- Initial ventral midline skin incision then linea alba sharply dissected avoiding ventral abdominal vein
- Main advantage - reduction in pain associated with an incision through the linea alba
- Ventral abdominal vein
- Confluence of bilateral pelvic veins, joined bilaterally by hypogastric veins and single ventral pubic vein
- Located along ventral midline, just axial to abdominal muscles
- Distance from pubis to caudal origin of abdominal vein varies by species and patient size but approximately one-fourth distance between cranial pubic bone and umbilicus
- Courses along inside of coelomic wall until reaching umbilicus, where it turns dorsad and joins the hepatic vein
- Variable location within mesovasorum
- Location at surgery depends on animal’s state of repletion and other space-occupying coelomic structures
- Can be ligated if traumatized
- Region between cranial margin of pubis and extending one-fourth of distance toward umbilicus, and region cranial to umbilicus progressing to xiphoid à no significant ventral vessels present
- Fat bodies
- Can be vascular and friable
- Small amount of “clear” free fluid not uncommon in healthy lizards
- Lateral (flank) celiotomy
- Requires rib transection
- Incision and subsequent scar not readily visible once healed
- Complications after paramedian coeliotomy in chameleons are rare
- Incision below lumbar spine in paralumbar space, often at an angle (caudal to or between the last ribs) to allow the largest possible incision without involving ribs
- No major vessels on entry into the coelom
- Technique also reduces interference by the paired coelomic fat bodies
- Presence of air-sac–like extensions of lungs, which appear as clear finger-like projections often present in the surgical field in chameleons
- Closure of coelomic aponeurosis not considered a holding layer as in mammals
- Seal only
- Absorbable monofilament suture in 3.0 to 5.0 size depending on the patient size, in simple continuous pattern with minimal tension recommended
- Exception - some gecko species (leopard geckos, African fat-tailed geckos, and crested geckos)
- Skin delicate and fragile and does not have the same “holding” strength that more typical keratinized lizard skin does
- Simple interrupted suture pattern recommended to close coelomic wall, followed by a typical horizontal mattress suture pattern in skin to increase strength and integrity of closure
- Exception - some gecko species (leopard geckos, African fat-tailed geckos, and crested geckos)
- Skin closed with nylon suture in horizontal mattress pattern to evert edges
- Surgery and sutures placed too close to wound edges may accelerate ecdysis
- Tissue adhesive over incision - help with waterproofing and protection

Describe the presentation of nutritional secondary hyperparathyroidism in lizards.
Metabolic bone disease (fibrous osteodystrophy)
- Secondary nutritional or renal hyperparathyroidism
- Inappropriate exposure to UVB
- Stages
- Preclinical
- early clinical (anorexia, lethargy, difficulty ambulating, +/- tremors, neuro signs, hypocalcemia)
- late clinical (thickened, swollen limbs, bowing - esp chameleons, pathologic fractures - often near metaphsysi, rubber jaw, neuro secondary to vertebral fractures)
- Pseudo hypertrophy of limbs from cartilage and fibrous tissue deposited on periosteal surfaces with progressive pressure atrophy of muscles
ZP
Describe the effects of the following vitamin deficiencies or excesses in lizards:
Hypovitaminosis D
Hypervitaminiosis B
Hypovitaminosis A
Hypervitaminiosis A
Vit E/Selenium Deficiency
Vitamin B1 (Thiamine) Deficiency
Hypovitaminosis D - fibrous osteodystrophy
- Metastatic calcification (green iguanas), dystrophic mineralization (Uromastyx) with low D3
Hypervitaminosis B - Calcium salt deposition in arterial media, terminal nephritis (green iguanas)
Hypovitaminosis A - squamous metaplasia esp pharyngeal mucosa, conjunctiva, urogenital tract, upper and lower respiratory tract
- Organochlorine pesticides may inhibit vitamin A metabolism
- Old world chameleons - may predispose to stomatitis
Hypervitaminosis A - soft tissue mineralization (chameleons), segmental calcification in colon
Vit E/ Selenium deficiency - muscle degeneration and necrosis: cutaneous red-white discoloration, myocardial mineralization, granulomatous lesions in dermis
- Progressive inability to use tongue, circling, weakness (veild chameleons)
Vit B1 (thiamine) deficiency - severe brain lesions, CNS signs (tremors, abnormal axial skeleton posture, hyperextension, twisting)
ZP
Describe the lesions associated with gout in lizards.
What affect does formalin have on urate crystals?
Gout - basophilic, needle-like (acicular), monosodium urate crystals (tophi) arranged in radiant pattern (or amorphous and eosinophlic to amphophilic), birefringent under polarizing light
- Deposited in and on tissues or in joints
- Predisposing factors: dehydration, renal disease
- Grossly chalk-like precipitates
- Articular - swollen and deformed joints, common in chronic
- Renal - white to gold foci grossly corresponding to tophi in renal tubules on histo
- Results in renal tubular necrosis, secondary foreign body reaction, variably extensive fibrosis and nephromegaly in chronic cases
- Visceral
- *urate crystals solubilize in 10% buffered formalin, better preserved in 100% alcohol
ZP
What are some common renal diseases of lizards, their lesions, and potential sequelae?
Renal disease - including degenerative changes with fibrosis, gout, and mineralization
- Most common outcome - nephromegaly esp green iguanas, may cause compression of distal colon and intestinal obstruction
- Renal secondary hyperparathyroidism - fibrous osteodystrophy
- Acute glomerulonephritis: thickening; membranous, exudative, and mesangioproliferative; intra- and extracapillary
- Chronic: fibrosis, glomerular tuft sclerosis, tubular nephrosis, brown pigment deposition in tubular epithelial cells, amyloid-like material in Komodo dragons
ZP
Cardiac disease is over-represented in what species?
What diseases are commonly seen?
Cardiovascular disease
- Inland bearded dragons overrepresented
- Artherosclerosis, aortic aneurism, pseudoaneurism (large, fluctuant to firm swellings up to 5cm bulging at dorsolateral neck just caudal to skull)
- Hemopericardium
What are two possible causes of avascular necrosis of the tail in lizards?
Trauma, venipuncture
ZP
Describe the lesions and clinical signs of compressive myelopathy in lizards.
What species is commonly affected?
What site does this occur?
Compressive myelopathy - secondary to cervical spine subluxation in Komodo dragons (C1-C4)
- Articular cartilage degeneration, necrosis and axonal degeneration, multifocal hemorrhage, demyelination, diffuse Wallerian degeneration, oligodendrocyte necrosis
ZP
Describe some of the common reproductive issues of female lizards.
What is the difference between follicular stasis and egg binding?
What lesions are present with egg-yolk coelomitis? Are any species particularly predisposed?
Folliculostasis, egg binding - environmental conditions
Obstructive dystocia
Yolk coelomitis - foreign body-type inflammation, mesothelial cell proliferation, secondary bacterial complication, often fatal
- Etiology trauma vs mature vitellogenic follicles failing to ovulate undergo atresia and rupture, released yolk overwhelms resorptin capacity
- Major cause of death in captive sexually mature female Fiji Island banded iguanas
What are some causes of cloacal prolapse in lizards?
What about hemipenal prolapse?
Cloacal and penile prolapse - nutritional, renal secondary hyperparathyroidsm, infection, dystocia, urolithiasis, neoplasia
- Causes of hemipene prolapse: truama, traction during copulation, myopathy, neurologic disease, GI foreign body













