English

Noun

snakes

1. Plural of snake

Verb

snakes

1. third-person singular of snake

   ''The road snakes through the mountains.

A snake is an elongate reptile of the suborder Serpentes. Like all reptiles, snakes are covered in scales. All snakes are carnivorous and can be distinguished from legless lizards by their lack of eyelids, limbs, external ears, and vestiges of forelimbs. The 2,700+ species of snakes spread across every continent except Antarctica ranging in size from the tiny, 10 cm long thread snake to pythons and anacondas over 17 feet long. In order to accommodate snakes' narrow bodies, paired organs (such as kidneys) appear one in front of the other instead of side by side. The snake is one of the most feared animals because of its association with evil and the common misconception that all snakes are venomous.

While venomous snakes comprise a minority of the species, some possess potent venom capable of causing painful injury or death to humans. However, venom in snakes is primarily for killing and subduing prey rather than for self-defense. Snakes may have evolved from a lizard which adapted to burrowing during the Cretaceous period (c 150 Ma), though some scientists have postulated an aquatic origin. The diversity of modern snakes appeared during the Paleocene period (c 66 to 56 Ma).

A literary word for snake is serpent (a Middle English word which comes from Old French, and ultimately from *serp-, "to creep"). In modern usage, the term serpent usually refers to a mythic or symbolic snake. In Christianity, the serpent is sometimes identified with the devil, as in the Biblical account of Adam and Eve, but also with healing, as in the Biblical account of the brass serpent of Moses. The serpent is also the symbol of the healing arts.

Introduction

|- |BolyeriidaeHoffstetter, 1946||Round Island boas||Round Island Burrowing Boa (Bolyeria multocarinata)|| |- |ColubridaeOppel, 1811||blind snakes||Black Blind Snake (Typhlops reticulatus)|| |}

Evolution

Phylogeny of snakes is poorly known because snake skeletons are typically small and fragile, making fossilization uncommon. However 150 million year old specimens readily definable as snakes with lizard-like skeletal structures have been uncovered in South America and Africa. It has been agreed, on the basis of morphology, that snakes descended from lizards. An early fossil snake, Najash rionegrina, was a two-legged burrowing animal with a sacrum, and was fully terrestrial. One extant analog of these putative ancestors is the earless monitor Lanthanotus of Borneo, although it also is semi-aquatic. As these ancestors became more subterranean, they lost their limbs and their bodies became more streamlined for burrowing. Primitive groups among the modern snakes, pythons and boas, have vestigial hind limbs: tiny, clawed digits known as anal spurs which are used to grasp during mating. There are numerous islands from which snakes are conspicuously absent such as Ireland, Iceland, and New Zealand. Snake scales are not discrete but extensions of the epidermis hence they are not shed separately, but are ejected as a complete contiguous outer layer of skin during each moult, akin to a sock being turned inside out.

Moulting serves a number of functions - firstly, the old and worn skin is replaced, secondly, it helps get rid of parasites such as mites and ticks. Renewal of the skin by moulting is supposed to allow growth in some animals such as insects, however this view has been disputed in the case of snakes.

Moulting is repeated periodically throughout a snake's life. Before a moult, the snake stops eating and often hides or moves to a safe place. Just prior to shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The inner surface of the old outer skin liquefies. This causes the old outer skin to separate from the new inner skin. After a few days, the eyes clear and the snake "crawls" out of its old skin. The old skin breaks near the mouth and the snake wriggles out aided by rubbing against rough surfaces. In many cases the cast skin peels backward over the body from head to tail, in one piece like an old sock. A new, larger, and brighter layer of skin has formed underneath.

An older snake may shed its skin only once or twice a year, but a younger, still-growing snake, may shed up to four times a year.

The shape and number of scales on the head, back and belly are characteristic to family, genus and species. Scales have a nomenclature analogous to the position on the body. In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing scientists to count the vertebrae without dissection.

Scalation counts are also used to tell the sex of a snake when the species is not readily sexually dimorphic. A probe is inserted into the cloaca until it can go no further. The probe is marked at the point where it stops, removed, and compared to the subcaudal depth by laying it alongside the scales. The fork in the tongue gives the snake a sort of directional sense of smell and taste simultaneously. In the majority of species, only one lung is functional. This lung contains a vascularized anterior portion and a posterior portion which does not function in gas exchange.

Lateral undulation

see also Lateral undulation Lateral undulation is the sole mode of aquatic locomotion, and the most common mode of terrestrial locomotion. This mode of movement is similar to running in lizards of the same mass.

Terrestrial

Terrestrial lateral undulation is the most common mode of terrestrial locomotion for most snake species.

Aquatic

When swimming, the waves become larger as they move down the snake's body, and the wave travels backwards faster than the snake moves forwards. Thrust is generated by pushing their body against the water, resulting in the observed slip. In spite of overall similarities, studies show that the pattern of muscle activation is different in aquatic vs terrestrial lateral undulation, which justifies calling them separate modes. All snakes can laterally undulate forward (with backward-moving waves), but only sea snakes have been observed reversing the pattern, i.e. moving backwards via forward-traveling waves. This mode of locomotion overcomes the slippery nature of sand or mud by pushing off with only static portions on the body, thereby minimzing slipping. In this mode, the belly scales are lifted and pulled forward before being placed down and the body pulled over them. Waves of movement and stasis pass posteriorly, resulting in a series of ripples in the skin. These snakes can perform a controlled glide for hundreds of feet depending upon launch altitude and can even turn in mid-air.

Reproduction

Although a wide range of reproductive modes are used by snakes; all snakes employ internal fertilization, accomplished by means of paired, forked hemipenes, which are stored inverted in the male's tail. The hemipenes are often grooved, hooked, or spined in order to grip the walls of the female's cloaca. The female python will not leave the eggs, except to occasionally bask in the sun or drink water and will generate heat to incubate the eggs by shivering. Recently, it has been confirmed that several species of snake are fully viviparous, such as the boa constrictor and green anaconda, nourishing their young through a placenta as well as a yolk sac, which is highly unusual among reptiles, or anything else outside of placental mammals. The fangs of 'advanced' venomous snakes like viperids and elapids are hollow in order to inject venom more effectively, while the fangs of rear-fanged snakes such as the Boomslang merely have a groove on the posterior edge to channel venom into the wound. Snake venoms are often prey specific, its role in self-defense is secondary.

Certain birds, mammals, and other snakes such as kingsnakes that prey on venomous snakes have developed resistance and even immunity to certain venom.

Snake venoms are complex mixtures of proteins and are stored in poison glands at the back of the head. These proteins can potentially be a mix of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins and many other toxins that affect the body in different ways. This makes it both difficult for the snake to use its venom and for scientists to milk them.

It has recently been suggested that all snakes may be venomous to a certain degree, the harmless snakes having weak venom and no fangs.

Snakes may have evolved from a common lizard ancestor that was venomous, from which venomous lizards like the gila monster and beaded lizard may have also derived. They share this venom clade with various other saurian species.

Venomous snakes are classified in two taxonomic families:

• Elapids - cobras including king cobras, kraits, mambas, Australian copperheads, sea snakes, and coral snakes.

The treatment for a snakebite is as variable as the bite itself. The most common and effective method is through antivenom, a serum made from the venom of the snake. Some antivenin is species specific or monovalent and some is made for use with multiple species in mind also known as polyvalent. In the United States for example, all species of venomous snakes are pit vipers, with the exception of the coral snake. To produce antivenin, a mixture of the venoms of the different species of rattlesnakes, copperheads, and cottonmouths is injected into the body of a horse in ever-increasing dosages until the horse is immunized. Blood is then extracted from the immunized horse and freeze-dried. It is reconstituted with sterile water and becomes antivenin. For this reason, people who are allergic to horses cannot be treated using antivenin. Antivenin for the more dangerous species (such as mambas, taipans, and cobras) is made in a similar manner in India, South Africa, and Australia with the exception being that those antivenins are species-specific.

Snake charmers

While not commonly thought of as a dietary item by most cultures, in some cultures, the consumption of snakes is acceptable, or even considered a delicacy, prized for its alleged pharmaceutical effect of warming the heart. Snake soup of Cantonese cuisine is consumed by local people in Autumn, to prevent a cold. Western cultures document the consumption of snakes under extreme circumstances of hunger. Cooked rattlesnake meat is an exception, which is commonly consumed in parts of the Midwestern United States. In Asian countries such as China, Taiwan, Thailand, Indonesia, Vietnam and Cambodia, drinking the blood of snakes, particularly the cobra, is believed to increase sexual virility. The blood is drained while the cobra is still alive when possible, and is usually mixed with some form of liquor to improve the taste.

Snakes as pets

In the Western world some snakes, especially docile species such as the ball python and corn snake, are kept as pets. To supply this demand a captive breeding industry has developed. Snakes bred in captivity tend to make better pets and are considered preferable to wild caught specimens.

Symbolism

In Egyptian history, the snake occupies a primary role with the Nile cobra adorning the crown of the pharaoh in ancient times. It was worshipped as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide (Cleopatra).

In Greek mythology snakes are often associated with deadly and dangerous antagonists, but this is not to say that snakes are symbolic of evil; in fact, snakes are a chthonic symbol, roughly translated as 'earthbound'. The nine-headed Lernaean Hydra that Hercules defeated and the three Gorgon sisters are children of Gaia, the earth. Medusa was one of the three Gorgon sisters who Perseus defeated.

India is often called the land of snakes and is steeped in tradition regarding snakes. The cobra is seen on the neck of Shiva and Vishnu is depicted often as sleeping on a 7 headed snake or within the coils of a serpent. There are also several temples in India solely for cobras sometimes called Nagraj (King of Snakes) and it is believed that snakes are symbols of fertility. There is a Hindu festival called Nag Panchami each year on which day snakes are venerated and prayed to. See also Nāga.

In Islam, Christianity and Judaism the snake makes its infamous appearance in the first book (Genesis 3:1) of the Bible when a serpent appears before the first couple Adam and Eve as an agent of the devil and tempts them with the forbidden fruit from the Tree of Knowledge. The snake returns in Exodus when Moses, as a sign of God's power, turns his staff into a snake and when Moses made the Nehushtan, a bronze snake on a pole that when looked at cured the people of bites from the snakes that plagued them in the desert. The serpent makes its final appearance symbolizing Satan in the Book of Revelation:"And he laid hold on the dragon the old serpent, which is the devil and Satan, and bound him for a thousand years." (Revelation 20:2)

The Ouroboros is a symbol that is associated with many different religions and customs, and is also claimed to be related to Alchemy. The Ouroboros or Oroboros is a snake eating its own tail in a clock-wise direction (from the head to the tail) in the shape of a circle, representing manifestation of one's own life and rebirth, leading to immortality.

The snake is one of the 12 celestial animals of Chinese Zodiac, in the Chinese calendar.

Many ancient Peruvian cultures worshipped nature. They placed emphasis on animals and often depicted snakes in their art.

In religion

Snakes

• Snake skeleton
• Venomous snake
• List of snakes
• List of Serpentes families
• Limbless vertebrates

Snakes in culture

• Snakebot
• Snake-arm robot
• Snake oil
• Exploding snake
• Snake Shyam
• Snakes on a Plane
• Serpent Mound
• Nahash

Cited references

References

• The Audubon Society Field Guide to Reptiles and Amphibians of North America
• Bullfinch's Complete Mythology

• Simon & Schuster's Guide to Reptiles and Amphibians of the World
• The Atlas of Snakes of the World
• Reptiles & Amphibians
• A Field Guide to Reptiles and Amphibians Eastern/Central North America
• The Worship of the Serpent
• Poisonous Snakes of the United States: How to Distinguish Them

• Snakes of the World
• Reptiles of the World: The Crocodilians, Lizards, Snakes, Turtles and Tortoises of the Eastern and Western Hemispheres
• Snake-Hunters' Holiday.
• A Field Book of North American Snakes
• The World of Venomous Animals
• Their Blood Runs Cold: Adventures With Reptiles and Amphibians
• The New Encyclopedia of Snakes
• Snake Species of the World: A Taxonomic and Geographic Reference
• Living Snakes of the World in Color
• நம்மை சுட்ரியுள்ள பாம்புகள் (Snakes around us, Tamil)
• Exotic Pets
• The Dangerous Snakes of Africa

External links

• Integrated Taxonomic Information System (USDA)
• US Snakes on eNature
• Snakes of the Indian Subcontinent
• European Snakes -- Large DB and Pictures about snakes
• Venomous Snakes Information Community
• Snake Cell -- An organization for wellbeing of snakes (INDIA)
• Snake World - Several Types of Snakes
• What's That Snake? Snake Identification Tool (OPLIN)
• Worlds Top 10 Most Poisonous Snakes - Toxic Ranking
• Swedish Museum of Natural History Herpetology Database

nah:Cōhuātl