Cobra

Egyptian Cobra, Naga haje

Cobra is the common name for a number of Asian and African snakes in several genera of the family Elapidae, characterized by smooth scales, large shields covering the head, eyes with round pupils, a pair of short, rigid fangs to inject venom, and the ability to expand their neck area to form a flattened hood. The term cobra is especially associated with the genus Naja, the "true cobras."

Description

King Cobra
Scientific classification
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Reptilia Order: Squamata Suborder: Serpentes Family: Elapidae Boie, 1827

Cobras are elapid snakes—members of the Elapidae family. The elapids are a family of venomous snakes found in tropical and subtropical regions around the world, including the Indian Ocean and the Pacific. They are characterized by possessing a set of hollow, fixed fangs through which they inject venom, and come in a wide range of sizes, from only 18 cm (Drysdalia) up to 6 m in length (King cobra, Ophiophagus). Myers et al. (2006a) recognize 46 genera of elapids, while the Integrated Taxonomic Information System (ITIS) lists 61 genera with 231 species. In addition to cobras, the Elapidae includes the taipans, brown snakes, tiger snakes, fierce snakes, coral snakes, mambas, sea snakes, and others.

Outwardly, terrestrial elapids look similar to the colubridae: almost all have long and slender bodies with smooth scales, a head that is covered with large shields and not always distinct from the neck, and eyes with round pupils. In addition, their behavior is usually quite active and most are oviparous. There are exceptions to all these generalizations: e.g. the death adders (Acanthophis) include short and fat, rough-scaled, very broad-headed, cat-eyed, live-bearing, sluggish ambush predators with partly fragmented head shields.

Some elapids are strongly arboreal (African Pseudohaje and Dendroaspis, Australian Hoplocephalus), while many others are more or less specialized burrowers (e.g. Ogmodon, Parapistocalamus, Simoselaps, Toxicocalamus, Vermicella) in either humid or arid environments. Some species have very generalized diets but many taxa have narrow prey preferences and correlated morphological specialisations, such as for feeding on other snakes, elongate burrowing lizards, squamate eggs, mammals, birds, frogs, fish, and so forth.

Sea snakes, which are also elapids, have adapted to a marine way of life in different ways and to various degrees. All have evolved paddle-like tails for swimming and the ability to excrete salt. Most also have laterally compressed bodies, ventral scales are much reduced in size, their nostrils are located dorsally (no internasal scales) and they give birth to live young (ovoviviparous). In general they have the ability to respire through their skin; experiments with the yellow-bellied sea snake, Pelamis platurus, have shown that this species can satisfy about 20% of its oxygen requirements in this manner, allowing for prolonged dives. The sea kraits (Laticauda sp. ), are the least well-adapted to an aquatic life. They spend much of their time on land where they also lay their eggs (oviparous). They having wide ventral scales, the tail is not as well-developed for swimming, and their nostrils are separated by internasal scales. See also Sea snake.

All elapids have a pair of proteroglyphous fangs that are used to inject venom from glands located towards the rear of the upper jaws. The fangs are the first two teeth on each maxillary bone, which are enlarged and hollow, and usually only one is in place on each side at any time. The maxilla is intermediate in length and mobility between typical colubrids (long, less mobile) and viperids (very short, highly mobile). When the mouth is closed, the fangs fit into grooved slots in the buccal floor; in the longest-fanged elapids (e.g. Acanthophis, Oxyuranus) it is common for the fangs to pierce right through the intermandibular skin, which does not seem to endanger the snake. The fangs are usually below the front edge of the eye and are angled backwards; due to this construction, most elapids must actually bite in order to envenomate. This action is therefore not as quick as with the viperids, that can envenomate with only a quick, stabbing motion. Some elapids (Acanthophis, Oxyuranus, and especially Dendroaspis) have long fangs on quite mobile maxillae (the prefrontal and ectopterygoid contacts are nearly as close together as in viperids), and can therefore make very fast stabbing strikes like viperids. Elapids use their venom both to immobilize their prey and in self-defense.

The hood is the name in anatomy for the flap of skin behind the head of cobras, which can be used to make the snake appear bigger. It can also carry distinctive markings. The hood of the Asian cobra is, proportionately, much larger than that of the king cobra and is usually yellow to brown, with a black-and-white spectacle pattern on top and two black and white spots on the lower surface.

The hood have also some kinds of lizards, e.g. Tropidurus delanonis.

Cobras generally inhabit tropical and desert regions of Asia and Africa.

genus

Types of cobra

The most common cobra is the Indian cobra or Spectacled cobra Naja naja, native to the Indian subcontinent and associated with snake charming there. The Black cobra, found in Pakistan and North India, is generally considered to be a sub-species.^{[citation needed]}

The second most common cobra species is the Monocled cobra, Naja kaouthia, widespread in Asia.

Coiled Cobra with hood dormant

In addition to a deadly bite, the Spitting cobra can incapacitate larger would-be predators by delivering venom to their eyes. While extremely irritating, it rarely causes lasting damage if washed out promptly

The King cobra is ophiophagous; it feeds almost entirely on other snakes, even venomous ones, although it sometimes preys on small rodents and birds. It will only attack humans if provoked or in other extreme circumstances that threaten its survival. If not treated, a king cobra's bite can kill a person in just half an hour. King Cobras may reach up to 5.2m (17.1ft) in length, making them the largest venomous snakes in the world.

Cobra venom

The snake will only attack a human if provoked or in other extreme circumstances which threaten its survival. Furthermore, for a dangerously venomous snake, the cobra's strikes are quite slow when compared to the almost literally "faster than the eye can see" strikes of such species as rattlesnakes. Additionally, not all bites result in envenomation and in the case of the Cobra the amount of "blank" strikes may be quite high: in one series of recorded bites in Malaysia only 55% of strikes had been poisonous. Cobra bites are fatal in about 10% of human cases. However, as with any venomous snake, a bite from a cobra should be treated as a potentially fatal injury and medical attention should be sought immediately. As with all elapids, the venom of cobras is highly neurotoxic and dangerous. Therefore, any cobra bite must be regarded as life-threatening and professional medical assistance should be immediately sought. Early symptoms of a bite include ptosis, diplopia , dysphagia, and dizziness, followed by progressive respiratory muscle weakness, ultimately requiring endotracheal intubation. Cobra venom is a postsynaptic neurotoxin. It works by stopping the acetylcholine molecules in the diaphragm muscle from interacting. Without treatment death from respiratory failure in very rare occasions may occur as early as 30 minutes after being bitten.

Standard treatment involves the use of antivenin. Additionally, it is possible to support bite victims via mechanical ventilation, using equipment of the type generally available at hospitals. Such support should be provided until the venom is metabolised and the victim can breathe unaided. If death occurs it takes place approximately 6 to 12 hours after the cobra bite. Cause of death is respiratory failure ie suffocation caused by complete paralysis of the diaphragm.

Rhythm

Cobra being charmed

Indian snake charmers play a harmless trick on spectators. A cobra rises from its basket and sways in time with the music, apparently hypnotized. In fact, as far as the snake is concerned, the music is irrelevant - the cobra can't hear a thing. What prompts it to perform is the snake charmer's clever manipulation of the cobra's natural tendencies. When suddenly thrust into the open air from the darkness of the basket, the snake rises up and spreads its hood, its normal reaction to a threat. It sees the swaying pipe and mistakes it for another snake. That error, together with the charmer's movements in time with the music, holds the snake's attention. As the charmer moves the pipe, so the cobra bobs its head. That is the only way for the snake to follow the pipe's movements, because it cannot swivel its eyes.

References

ISBN links support NWE through referral fees

Elapidae (TSN 174348). Integrated Taxonomic Information System. Accessed on 27 November 2006. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=174348 Elapidae F. Boie, 1827 Taxonomic Serial No.: 174348

Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed December 05, 2007 at http://animaldiversity.org. Family Elapidae (cobras, coral snakes, and kraits) http://animaldiversity.ummz.umich.edu/site/accounts/classification/Elapidae.html

Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed December 05, 2007 at http://animaldiversity.org. 

http://animaldiversity.ummz.umich.edu/site/accounts/classification/Naja.html#Naja Genus Naja

External links

• The Asiatic Cobra Systematics Page
• Richard Mastenbroek's Elapid Pages, captive care information

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