High School Reptile Shows & Biology Programs

Reptiles are exotherms and must obtain their body heat from outside sources. Their optimum temperature is around 30°C. In snakes, one lung is either atrophied or non-existent, while the other is elongated, as are some of the internal organs. Some snake species have remnant hip structure with atrophied leg bones, while the more modern species have little or none of these vestiges.

Reptiles evolved from labyrinthodont amphibians during the late carboniferous era, and in crossing the boundary from aquatic to terrestrial life became the ancestral stock from which all terrestrial vertebrates have evolved, both living and extinct.

Many changes and improvements were needed in the basic body plan to enable the transition to occur, some of these being: skin sufficiently able to resist dehydration of essential body fluids, lungs and circulatory system improved, a strengthened musculature and skeletal structure, larger brain, and, perhaps the most innovative of all — the land egg!

The origin of the snakes (Ophidia) is a problem. From the anatomy of primitive snakes — Boas, Pythons and Blindsnakes — it is obvious they evolved from Lizard ancestry (these species have remnant pelvic and leg bones), but the rarity of fossil remains from the Mesozoic (Dinosaur) era has prevented Paleontologists from ascertaining the particular lizard species from which they arose.

As there are many similarities in the skulls of Varanid monitors (Goannas) and snakes, it is theorised that when transitional forms between lizards and snakes are discovered, they will be similar to Ianthasaurus, a primitive short-legged, long bodied burrowing varanid from Borneo. According to this theory, some of the early transitional forms of snakes remained in their habitat, giving rise to the several families of burrowing blind snakes still extant, while others produced descendants that moved above ground and sired the Pythons, Boids and more progressive members of the group, the venomous snakes.

Certain senses of snakes are quite unique. Pit Vipers, Boas and Pythons have evolved senses not present in other vertebrates — heat sensitive organs (pits) which can pick up a change of temperature as little as 0.002°C. These are used to detect the presence and position of camouflaged or nocturnal prey.

In the roof of the mouth is the Jacobson’s organ — tiny airborne particles are picked up by the forked tongue and transferred to this organ where they are ‘tasted’. Snakes are very good at tracking prey using this organ, and can follow the faintest of scent trails.

Most snakes — with a few exceptions, have poor eyesight and are colour blind. When a snake wants to focus its eyes on a subject, it has to make a conscious effort to do so — snakes’ eyes don’t focus automatically like most other animals.

The venomous snakes — especially the Vipers and Pit Vipers — have evolved the most advanced and specialised fang structures of probably any venomous animal known, although their venom is nowhere near as potent as that of the Elapids — comprising snakes such as the Cobra Family, Mamba’s etc. with relatively fixed fangs. All Australian venomous snakes are members of this (Elapid) Family, even the ‘Death Adder’ — a short, thickset snake very similar in appearance and habit to the overseas Vipers — (hence the name ‘adder’). The venom of Elapid snakes, unlike that of the Vipers, contains potent amounts of neurotoxins (nerve poisons) as well as the tissue destroying toxins prevalent in Viper venom.