Anatomy and physiology of lizards

Question 1

the most widely distributed of all the reptiles

Answer 1

lizards

They are found on every continent.

Question 2

Lizard Life expectancy:

Answer 2

5-28 years, depending on species

Question 3

Define Sauria/Saurians

Answer 3

a division of Reptilia comprising the lizards, crocodilians, and various extinct elongated limbed reptiles that superficially resemble lizards.

so these days sauria means lizards

Question 4

There are various infraorders of Saurians. Name 4.

Answer 4

Iguania
Gekkota
Scincomorpha
Varanoidea

Question 5

Describe Saurian infraorder Iguania

Answer 5

Contains three families:
Iguanidae,
Agamidae Agamas and
Chamaeleonida

Includes: Iguanas, Agamas, Water & Bearded dragons Chameleons

Question 6

Describe Saurian infraorder Gekkota

Answer 6

Gekkonidae: Geckos

Question 7

Describe Saurian infraorder Scincomorpha

Answer 7

Contains two families: Teiidae and Scincidae

Includes: Tegus and Skinks

Question 8

Describe Saurian infraorder Varanoidea

Answer 8

Contains two families:
Helodermatidae and Varanida

Include: Beaded lizards, Monitors, Komodo dragon

Question 9

The temperature at which a lizard can survive

Answer 9

depends from the species

Temperate lizards < 30ºC,
tropical ones < 35º C,
desert lizards <46º C

Many lizards are dark colored in the morning and lighten in color as the body warms up.

Question 10

define estivate

Answer 10

spend a hot or dry period in a prolonged state of torpor or dormancy.

Tropical species can estivate at times of drought, temperate and subtropical species can hibernate.

Question 11

Describe the morphology of Iguanidae.

Answer 11

They are moderate to large in size and include many herbivorous species.

They have a large, laterally compressed body with nuchal and dorsal crest, large gular pouch, and conspicuous subtympanic plate.

The tail is up to three times the snout-to-vent length and can be whip like.

Femoral pores are prominent in the males.
Males are generally more brightly colored but the coloring of females tends to wash out with age.

Several species have a prominent parietal eye. Almost all are oviparous. Many have partitions in the colon to slow down food ingesta.

Question 12

Iguanas are pleurodont, what does this mean?

Answer 12

adjective. (of the teeth of some reptiles) having no roots and being fused by their lateral sides only to the inner surface of the jawbone.

Question 13

Explain: Iguanas and nasal salt glands.

Answer 13

Nasal salt glands are present in herbivorous iguanid lizards such as the green iguana.

Solutions with high concentrations of sodium and potassium can be excreted by these glands, and their importance in osmoregulation in some species is greater than that of the kidneys and is vital for the animal’s survival.

Question 14

Describe Agamidae.

Answer 14

Mainly terrestrial lizards with well-developed limbs. The old world equivalent of Iguanidae.

They have acrodont teeth and some species have almost rodentlike incisors at the front
of the jaw.

Acrodont = adjective. (of the teeth of some reptiles) having no roots and being fused at the base to the margin of the jawbones

Some species have sexually dimorphic crests and spines. They are mainly oviparous.

Question 15

Describe Chamaeleonidae.

Answer 15

This is an arboreal family (tree-living).
They laterally compressed body and are mainly diurnal and insectivorous.

The upper and lower eyelid is fused to form a pyramid mound with the eye as the aperture in the center. Each eye is capable of independent movement and they use
accommodation to measure distance.

The eye lens is like a telephoto lens and the large retina and high number of cones provide the chameleon with large visual images of its prey.

The tongue is rapidly extensible to a distance of at least twice the animal’s trunk length.

Chameleons have very specialized skulls with their parietal crest raised into a casque.

Question 16

Chameleon feet

Answer 16

zygodactyl (having two toes pointing forward and two backward)

with toes fused together and opposed in groups of two and three

Question 17

identify

Answer 17

tegu lizard or
Argentine black and white tegu

carnivorous but sometimes kept as pets!

Question 18

Describe Gekkonidae/Eublepharidae.

Answer 18

nocturnal insectivores

They have loose skin and fat pads in the tail.
Many lack eyelids.

They are not sexually dimorphic so males and females may look the same (check the vent area for sexing).

They are oviparous and lay very hard-shelled eggs.

Some gecko species are capable of parthenogenesis.

Question 19

define Eublepharidae

Answer 19

a family of geckos that includes leopard geckos

Eublepharids are unusual in that they are terrestrial and have eyelids but they lack the adhesive lamellae and so are unable
to climb as opposed to the “typical” gecko species.

Question 20

identify

Answer 20

green anole

Question 21

Explain how geckos can stick to surfaces.

Answer 21

Most have adhesive toe pads which contain rows of tiny overlapping scales ventrally called lamellae.

Each lamella has tiny, branching hairs called setae which can number up to one million in some.

The ends of these setae are spatulate and it is the friction between these endings that creates the adhesive qualities of the
feet and enables them to walk across ceilings and glass.

Question 22

Describe Varanidae.

Answer 22

A family of lizards called monitor lizards.

Are the giants of the lizard world.
They are stocky with smooth scales.
The tongue is forked for half its length.

In some species ossification of the hemipenes can be seen on radiographs.
Despite their size they are active predators with higher metabolic rates than most other lizards.

They are oviparous.

Question 23

Describe Scincidae.

Answer 23

Family of lizards called skinks.

Large terrestrial family that live mostly on or underground. They are small to medium in size.

They are smooth scaled and are glossy in appearance. The limbs are short in relation to the body and some species are completely limbless.

They have a prominent ear opening.
The tail can be lost and regenerates.

Some species are oviparous some are viviparous (live young).

mainly insectivorous, some herbivorous species.

Question 24

Describe the skeletal system of lizards.

Answer 24

fused mandibular symphysis

All the vertebrae except the cervical ones, bear ribs. The number of tail vertebrae is usually higher than the number of presacral vertebrae.

Have a clavicle and often an interclavicle too.
The hindlimb is longer than the forelimb.

The tarsal bones have fused to form two bones called the astragalus-calcaneum.

Question 25

Describe the lizard cardiovascular system.

Answer 25

The heart has three chambers: two atria and one ventricle. Paired right and left aorta fuse caudal to it to form the dorsal aorta. A large ventral abdominal vein lies along the inner surface of the midline. (poss. site for venipuncture) Lizards have a renal portal system. Larger lizards have a vasovagal reflex whereby pressure on the eyeballs decreases the heart rate and blood pressure. (like in mammals)

Question 26

Describe the lizard respiratory system.

Answer 26

The lizard palate has two long slit-like openings rostrally. The glottis is variable in location and can be found very rostrally or at the back of the tongue. Lizards have no diaphragm so they breathe by expansion and contraction of the ribs. Three lung types are found in lizards: - unicameral, paucicameral (middle in image) and multicameral. (one chamber vs many chambers plus differently shaped (pauci)) Lizards have little capacity for aerobic respiration and switch to anaerobic quite fast.

Question 27

Describe the lizard digestive system.

Answer 27

The majority of lizards are omnivorous or carnivorous, only about 40 species are herbivorous. Teeth either pleurodont or acrodont (see image). Lizards chew their food and will tear off pieces if the food item is too big to swallow. Lizard teeth are simple conical structures that have no sockets and pleurodont teeth are regularly shed and replaced in waves. The gastrointestinal tract of insectivores and omnivores is relatively simple. The stomach is tubular and simple and leads into a short small intestine and large intestine. Some species like geckos use their tail for fat storage as an emergency energy source. Herbivores such as the iguana are hindgut fermenters.

Question 28

Describe the lizard urinary system.

Answer 28

The kidneys are lobed and lie retroperitoneally within the pelvic canal in the dorsocaudal coelom. Most lizards have a thin walled bladder but some have no bladder at all. In species without a bladder, urine is stored and modified in the distal colon before being excreted. Mainly uric acid. Nasal salt glands for excess salts.

Question 29

Describe the lizard reproductive system.

Answer 29

The testes as well as the ovaries are located cranial to the kidneys. The right testis and right ovary lies cranial to the left and is intimately connected with the vena cava by short blood vessels. The male has paired hemipenes, which are stored in the tail base and can be visualized externally by bulges at the ventral proximal tail. In oviparous species, the eggs are retained within the mother until birth. About one fifth of lizards are viviparous - the fetus is retained within the oviduct where there is a primitive placental type of circulation.

Question 30

Lizard senses.

Answer 30

Parietal eye for light detection. No external ear apart from a fold of skin in some species and the tympanic membrane is usually visible in a shallow depression on the side of the head. Some gecko species store calcium in endolymphatic sacs which can appear as white swellings on either side of the neck. Lizards have good color vision but only a narrow binocular field, so this is why they typically cock their head to one side to get the best monocular vision. Eyelids are present, except in some gecko species. The Jacobson’s organ located in the roof of the mouth is highly sensitive.

Question 31

what is egg yolk coelomitis

Answer 31

Yolk coelomitis as a result of pre-ovulatory follicular stasis is a common disorder in captive reptiles, especially in captive lizards of various genera. The clinical signs are generally fairly non-specific.

Question 32

Describe lizard integument.

Answer 32

Scales can be modified into crests, sharp spines, dewlaps and shields. The dermis contains the chromatophores, which provide the elaborate range of skin coloration. At ecdysis, scales are shed gradually and lizards will usually rub against hard objects to shed the molting layer. The skin has few glands but many lizards have femoral pores in a single row on the ventral aspect of the thigh. These are not true glands but are tubular skin invaginations that produce a waxy secretion.