 Snake Structure |
Snakes have a long slender body. It has some 100 vertebrae and in some cases more than 300 vertebrae. Snakes have a light skeleton and are made in such a way so as to enable it to have free movement. Each vertebra is connected to a pair of ribs on both sides. The first two vertebrae are connected to the head and not to the ribs. The skull of the snake is built loosely so as to permit it to swallow a large pray. Both jaws have a large number of sharp, needle like teeth, all curved toward the rear of the mouth.Venomous snakes have two hollow, hypodermics like teeth, known as fangs, in the front of the upper jaw. In a large group of snakes that includes the vipers, the fang-bearing bone is attached to the skull in such a way that the fangs can be moved back up against the roof of the mouth when not in use. The cobras and coral snakes represent another large group of snakes, in which the fangs are not movable but are constantly erect. The fangs are connected by the venom duct to the two venom glands, which are modified salivary glands situated on each side of the head behind the eye.The snakes must bite to inject their venom. They can bite from any position including under water. Three species of snake can spit or eject the venom in a fine spray, which is aimed at the eyes of an enemy. They can spit for distances up to 8 ft. If the venom gets into the eyes, it may cause blindness. The spitting is used only in defence and never to obtain food.Vision is well developed in most snakes. Many burrowing snakes are virtually blind. Snakes have a strong sense of smell, which they use to a large extent for hunting food. They also have an extra chemical sense that is widely used during most activities. The tongue flicks out, picking up odours and carrying them to the roof of the mouth into contact with a sensory receptor called Jacobson’s organ.Snakes are deaf to airborne sounds. Thus a rattlesnake does not hear the sound of another snake’s rattle, nor does the cobra hear the snake charmer’s flute. They can, however, feel vibrations through the ground or whatever they are resting on.The pit vipers, as well as some boas and pythons, have another kind of sense organ, a heat receptor that can detect small differences in temperature. By means of these receptors the snakes can locate and capture warm-blooded prey at night.Snakes move slower than an adult human can run; the fastest recorded speed achieved by any snake is about 13 km/hr.Snakes have a well developed nervous system. Their intelligence level is between fish and mammals. They are nervous and excitable when caught but adapt to gentle care. Some snakes, such as the hognose when disturbed, go through elaborate bluffing performances; harmless snakes can even appear more dangerous than venomous ones. Many snakes vibrate their tails back and forth when excited, and if they happen to be in dry grass or leaves, a whirring noise may be heard. The rattling sound is a warning to enemies.Urogenital system – The urogenital system in snakes is not very distinctive from that of other vertebrates. The testes and ovaries tend to be staggered as a consequence of the elongation of the body, with the right usually lying anterior to the left. Snakes do not have a urinary bladder, and kidney wastes are excreted in a solid state as uric acid. The male snake has two separate organs, the hemipenes. This structure is not homologous with the penis of mammals but seems to represent a completely different solution to the problem of internal fertilization. It is a saclike structure that must be turned inside out to be inserted in the cloaca of the female and can be removed only by turning it back to inside in, because to draw it out directly would damage the female considerably. The hemipenis is extremely variable in its overall appearance and structure; the cloaca of the female is often similarly constructed, thus preventing cross-fertilization by males of related species.All snakes are carnivorous, eating a variety of animal life, from insects, spiders, and snails to frogs, mice, and rats. A number of snakes eat only other kinds of snakes.Snakes reproduce both by laying eggs and by producing living ones hatched inside their body. The young ones are usually abandoned. Parental care is entirely absent as far as the young are concerned, but a few species guard the eggs during incubation, and the female python actually broods them.The greatest age known for any snake is just under 30 years, attained by both the anaconda and the black-lipped cobra. Snakes are found in all the warmer parts of the world, except Ireland, New Zealand. |
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