Anatomy and physiology of lizards Flashcards
the most widely distributed of all the reptiles
lizards
They are found on every continent.
Lizard Life expectancy:
5-28 years, depending on species
Define Sauria/Saurians
a division of Reptilia comprising the lizards, crocodilians, and various extinct elongated limbed reptiles that superficially resemble lizards.
so these days sauria means lizards
There are various infraorders of Saurians. Name 4.
Iguania
Gekkota
Scincomorpha
Varanoidea
Describe Saurian infraorder Iguania
Contains three families:
Iguanidae,
Agamidae Agamas and
Chamaeleonida
Includes: Iguanas, Agamas, Water & Bearded dragons Chameleons
Describe Saurian infraorder Gekkota
Gekkonidae: Geckos
Describe Saurian infraorder Scincomorpha
Contains two families: Teiidae and Scincidae
Includes: Tegus and Skinks
Describe Saurian infraorder Varanoidea
Contains two families:
Helodermatidae and Varanida
Include: Beaded lizards, Monitors, Komodo dragon
The temperature at which a lizard can survive
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.
define estivate
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.
Describe the morphology of Iguanidae.
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.
Iguanas are pleurodont, what does this mean?
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.
Explain: Iguanas and nasal salt glands.
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.
Describe Agamidae.
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.
Describe Chamaeleonidae.
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.
Chameleon feet
zygodactyl (having two toes pointing forward and two backward)
with toes fused together and opposed in groups of two and three
identify
tegu lizard or
Argentine black and white tegu
carnivorous but sometimes kept as pets!
Describe Gekkonidae/Eublepharidae.
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.
define Eublepharidae
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.
identify
green anole
Describe Varanidae.
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.
Describe Scincidae.
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.
Describe the lizard respiratory system.
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.
Describe the lizard digestive system.
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.
