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[[File:Ophiophagus scalation.png|thumb|left|Scalation of the king cobra]]
[[File:Ophiophagus scalation.png|thumb|left|Scalation of the king cobra]]
The [[skin]] of this snake is either olive-green, tan, or black, and it has faint, pale yellow cross bands down the length of the body. The belly is cream or pale yellow, and the scales are smooth. Juveniles are shiny black with narrow yellow bands (can be mistaken for a [[banded krait]], but readily identified with its expandable hood). The head of a mature snake can be quite massive and bulky in appearance, though like all snakes, they can expand their jaws to swallow large prey items. It has [[proteroglyph]] dentition, meaning it has two short, fixed fangs in the front of the mouth which channel venom into the prey like hypodermic needles. The male is larger and thicker than the female. The average lifespan of a wild king cobra is about 20 years.<ref name="NG"/>
The [[skin]] of this snake is either olive-green, tan, or black, and it has faint, pale yellow cross bands down the length of the body. The belly is cream or pale yellow, and the scales are smooth. Juveniles are shiny black with narrow yellow bands (can be mistaken for a [[banded krait]], but readily identified with its expandable hood). The head of a mature snake can be quite massive and bulky in appearance, though like all snakes, they can expand their jaws to swallow large prey items. It has [[proteroglyph]] dentition, meaning it has two short, fixed fangs in the front of the mouth which channel venom into the prey like hypodermic needles. The male is larger and thicker than the female. The average lifespan of a wild king cobra is about 20 years.<ref name="NG"/> hey there peeps u gay darrin!!!


The dorsal scales along the center of the king cobra's body have 15 rows. Males have 235 to 250 ventral scales, while females have 239 to 265. The subcaudal scales are single or paired in each row, numbering 83 to 96 in males and 77 to 98 in females.<ref name="ds">{{cite book |title=Venomous Land Snakes, Dr.Willott|publisher= Cosmos Books Ltd|isbn= 988-211-326-5}}</ref>
The dorsal scales along the center of the king cobra's body have 15 rows. Males have 235 to 250 ventral scales, while females have 239 to 265. The subcaudal scales are single or paired in each row, numbering 83 to 96 in males and 77 to 98 in females.<ref name="ds">{{cite book |title=Venomous Land Snakes, Dr.Willott|publisher= Cosmos Books Ltd|isbn= 988-211-326-5}}</ref>

Revision as of 16:14, 4 December 2012

This article is about the snake. For other uses, see King Cobra (disambiguation).

King cobra
A captive king cobra in Puttur, India
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Ophiophagus
Species:
O. hannah
Binomial name
Ophiophagus hannah
Cantor, 1836
  Distribution of the king cobra
Synonyms

Genus-level:

The king cobra (Ophiophagus hannah) is the world's longest venomous snake, with a length up to 5.6 m (18.5 ft).[1] This species, which preys chiefly on other snakes, is found predominantly in forests from India through Southeast Asia to Indonesia and the Philippines. Despite the word "cobra" in its name, this snake is not a member of Naja ("true cobras") but belongs to its own genus. The king cobra is considered to be a very dangerous snake.[2][3][4] It has cultural significance as well.[5]

Description

The king cobra averages at 3 to 4 m (9.8 to 13.1 ft) in length and typically weighs about 6 kg (13 lb). This species is more slender than the Eastern Diamondback Rattlesnake and the Gaboon Viper, who compete for the title of the heaviest venomous snake, but at average sizes, it is much longer and will weigh approximately the same as the two bulky vipers. The longest known specimen was kept captive at the London Zoo, and grew to around 18.5 to 18.8 ft (5.6 to 5.7 m) before being euthanised upon the outbreak of World War II. The heaviest wild specimen was caught at Royal Island Club in Singapore in 1951, which weighed 12 kilograms (26 lb) and measured 4.8 m (16 ft), though an even heavier captive specimen was kept at New York Zoological Park and was measured as 12.7 kilograms (28 lb) at 4.4 m (14 ft) long in 1972.[6] The length and mass of the snakes highly depend on their localities and some other factors. Despite their large sizes, typical king cobras are fast and agile.[7]

Scalation of the king cobra

The skin of this snake is either olive-green, tan, or black, and it has faint, pale yellow cross bands down the length of the body. The belly is cream or pale yellow, and the scales are smooth. Juveniles are shiny black with narrow yellow bands (can be mistaken for a banded krait, but readily identified with its expandable hood). The head of a mature snake can be quite massive and bulky in appearance, though like all snakes, they can expand their jaws to swallow large prey items. It has proteroglyph dentition, meaning it has two short, fixed fangs in the front of the mouth which channel venom into the prey like hypodermic needles. The male is larger and thicker than the female. The average lifespan of a wild king cobra is about 20 years.[8] hey there peeps u gay darrin!!!

The dorsal scales along the center of the king cobra's body have 15 rows. Males have 235 to 250 ventral scales, while females have 239 to 265. The subcaudal scales are single or paired in each row, numbering 83 to 96 in males and 77 to 98 in females.[7]

Taxonomy

Ophiophagus hannah belongs to the monotypic genus Ophiophagus. It is classified under the family Elapidae.

The king cobra is the sole member of genus Ophiophagus, while most other cobras are members of the genus Naja. They can be distinguished from other cobras by size and hood. King cobras are generally larger than other cobras, and the stripe on the neck is a chevron instead of a double or single eye shape that may be seen in most of the other Asian cobras. Moreover, the hood of the king cobra is narrower and longer.[2] A foolproof method of identification is if on the head, clearly visible, is the presence of a pair of large scales known as occipitals, at the back of the top of the head. These are behind the usual "nine-plate" arrangement typical of colubrids and elapids, and are unique to the king cobra.

The species was first described by the Danish naturalist Theodore Edward Cantor in 1836.

Distribution and habitat

The king cobra is distributed across South Asia, Southeast Asia, and the southern areas of East Asia (southern China) where it is not common. It lives in dense highland forests,[1][9] preferring areas dotted with lakes and streams. King cobra populations have dropped in some areas of its range because of the destruction of forests. It is listed as an Appendix II Animal within CITES.[10]

Behaviour

A male king cobra extending its hood

A king cobra, like other snakes, receives chemical information via its forked tongue, which picks up scent particles and transfers them to a special sensory receptor (Jacobson's organ) located in the roof of its mouth.[1] This is akin to the human sense of smell. When the scent of a meal is detected, the snake flicks its tongue to gauge the prey's location (the twin forks of the tongue acting in stereo); it also uses its keen eyesight (king cobras are able to detect moving prey almost 100 m [330 feet] away), intelligence,[11] and sensitivity to earth-borne vibration to track its prey.

Following envenomation, the king cobra will begin to swallow its struggling prey while its toxins begin the digestion of its victim. King cobras, like all snakes, have flexible jaws. The jaw bones are connected by pliable ligaments, enabling the lower jaw bones to move independently. This allows the king cobra to swallow its prey whole, as well as letting it swallow prey much larger than its head.[1]

King cobras are able to hunt throughout the day, although it is rarely seen at night, leading most herpetologists to classify it as a diurnal species.[1][12]

A king cobra in the St. Louis Zoo with the hood retracted

Diet

The king cobra's generic name, Ophiophagus is a Greek-derived word which means "snake-eater", and its diet consists primarily of other snakes, including ratsnakes, small pythons and even other venomous snakes such as various members of the true cobras (of the genus Naja), and even the much more venomous members of the krait family.[12][13] When food is scarce, they may also feed on other small vertebrates, such as lizards, birds, and rodents. In some cases, the cobra may "constrict" its prey, such as birds and larger rodents, using its muscular body, though this is uncommon.[1][13] After a large meal, the snake may live for many months without another one because of its slow metabolic rate.[1] The king cobra's most common meal is the ratsnake; pursuit of this species often brings king cobras close to human settlements.

A king cobra in its defensing posture (mounted specimen at the Royal Ontario Museum).

Defense

When confronted, this species will quickly attempt to escape and avoid any sort of confrontation.[14] However, if provoked, the king cobra can be highly aggressive.[4][8]

When concerned, it rears up the anterior portion (usually one-third) of its body when extending the neck, showing the fangs and hissing loudly.[2][8] It can be easily irritated by closely approaching objects or sudden movements. When raising its body, the king cobra can still move forward to strike with a long distance [8] and people may misjudge the safe zone. The king cobra may deliver multiple bites in a single attack [3] but adults are known to bite and hold on. In spite of being a highly dangerous snake, it prefers to escape first unless there is no way to go.[4] Since this species is secretive and tends to inhabit less-populated forested regions and dense jungle,[2][8] it is rarely encountered and seldom comes across humans, except those individuals which are caught for performances and thus many victims bitten by king cobras are actually snake charmers.[2]

If a king cobra encounters a natural predator, such as the mongoose, which has resistance to the neurotoxins,[15] the snake generally tries to flee. If unable to do so, it forms the distinctive cobra hood and emits a hiss, sometimes with feigned closed-mouth strikes. These efforts usually prove to be very effective, especially since it is much more dangerous than other mongoose prey, as well as being much too large for the small mammal to kill with ease.

A good defense against a cobra for anyone who accidentally encounters this snake is to slowly remove a shirt or hat and toss it to the ground while backing away.[16]

The growling hiss

The hiss of the king cobra is a much lower pitch than many other snakes and many people thus liken its call to a "growl" rather than a hiss. While the hisses of most snakes are of a broad-frequency span ranging from roughly 3,000 to 13,000 Hz with a dominant frequency near 7,500 Hz, king cobra growls consist solely of frequencies below 2,500 Hz, with a dominant frequency near 600 Hz, a much lower sounding frequency closer to that of a human voice. Comparative anatomical morphometric analysis has led to a discovery of tracheal diverticula that function as low-frequency resonating chambers in king cobra and its prey, the mangrove rat snake, both of which can make similar growls.[17]

Reproduction

A juvenile king cobra

The king cobra is unusual among snakes in that the female king cobra is a very dedicated parent. She makes a nest for her eggs, scraping up leaves and other debris into a mound in which to deposit them, and remains in the nest until the young hatch. A female usually deposits 20 to 40 eggs into the mound, which acts as an incubator. She stays with the eggs and guards the mound tenaciously, rearing up into a threat display if any large animal gets too close, for roughly 60 to 90 days.[18] Inside the mound, the eggs are incubated at a steady 28 °C (82 °F). When the eggs start to hatch, instinct causes the female to leave the nest and find prey to eat so she does not eat her young.[19] The baby king cobras, with an average length of 45 to 55 cm (18 to 22 in), have venom which is as potent as that of the adults. They may be brightly marked, but these colours often fade as they mature. They are alert and nervous, being highly aggressive if disturbed.[2]

Venom

The venom of the king cobra consists primarily of neurotoxins, but it also contains cardiotoxic and some other compounds.[12] Similar to other venomous creatures, toxic constituents inside the venom are mainly proteins and polypeptides.[20]

King cobra skull, lateral view, showing fangs

In common with those of other venomous snakes, LD50 values of the king cobra venom vary with different injection methods and toxicological research, although 1.7 mg/kg of subcutaneous injection, 1.31 mg/kg of Intravenous injection and 1.644 mg/kg of Intraperitoneal injection are common data found in toxicological sources (Australian Venom and Toxin database and Dr. Bryan Grieg Fry's sources).[21][22] Engelmann listed the Intravenous LD50 at 0.9 mg/kg[23] and the mean value of subcutaneous LD50 of five wild-caught king cobras in Southeast Asia was determined as 1.93 mg/kg in another study.[24] The book "Snake of medical importance" (1990) gives a datum of 0.34 mg/kg of intramuscular injection for the specimens found in China in a passing sentence.[25] Besides, toxicity may vary among individuals coming from different geographical localities.

This species is capable of delivering a fatal bite and a large quantity of venom can be injected with a dose anywhere from 200–500 mg on average,[2][25][26] and up to 7 ml.[8] Engelmann and Obst (1981) list the average venom yield at 420 mg (dry weight).[23] A large quantity of antivenom may be needed to reverse the progression of symptoms developed if bitten by a king cobra.[3]

During a bite, venom is forced through the snake's 1.25 to 1.5 cm (0.49 to 0.59 in) fangs into the wound, and the toxins begin to attack the victim's central nervous system. Symptoms may include severe pain, blurred vision, vertigo, drowsiness, and paralysis. Envenomation progresses to cardiovascular collapse, and the victim falls into a coma. Death soon follows due to respiratory failure. Moreover, envenomation from king cobras is clinically known to cause renal failure as observed from some snakebite precedents of this species.[27]

The mortality rate and death time resulting from a bite can vary sharply with many factors including the quantity of venom delivered, the site of bite and the health state of the victim.[27] Data provided by different sources, which may come from different regions, could also have a significant difference: while a report mentions that many bites from king cobras involved non-fatal amounts of venom,[28] another report of clinical statistics released by the South Indian Hospital reveals that actually two-thirds of the bitten patients received severe bites from this species.[27] According to the University of Adelaide Department of Toxicology, an untreated bite has a mortality rate of 50-60%.[29] Bites from a king cobra may result in a rapid fatality [2][3] which can be as early as 30 minutes after envenomation,[3] depending upon several factors including the nature and severity of the bites. A bite from a king cobra is said to be capable of bringing down an elephant.[8]

There are two types of antivenom made specifically to treat king cobra envenomations. The Red Cross in Thailand manufactures one, and the Central Research Institute in India manufactures the other; however, both are made in small quantities and are not widely available.[30] Ohanin, a protein component of the venom, causes hypolocomotion and hyperalgesia in mammals.[31] Other components have cardiotoxic,[32] cytotoxic and neurotoxic effects.[33] In Thailand, a concoction of alcohol and the ground root of turmeric is ingested, which has been clinically shown to create a strong resilience against the venom of the king cobra, and other snakes with neurotoxic venom.[34]

The haditoxin in the king cobra venom was discovered by Singaporean scientists to be structurally unique and can have unique pharmacological properties.[35] Biochemical studies confirmed it existed as a noncovalent dimer species in solution. Its structural similarity to short-chain α-neurotoxins and κ-neurotoxins notwithstanding, haditoxin exhibited unique blockade of α7-nAChRs (IC50 180 nM), which is recognized by neither short-chain α-neurotoxins nor κ-neurotoxins.[20]

Cultural significance

A king cobra in India

In Burma, king cobras are often used by female snake charmers.[13] The charmer is usually tattooed with three pictograms, using an ink mixed with snake venom; superstition holds that it protects the charmer from the snake.[13] The charmer kisses the snake on the top of its head at the end of the show.[13]

In India, the king cobra is believed to possess exceptional memory. According to a myth, the picture of the killer of a king cobra stays in the eyes of the snake, which is later picked up by the partner and is used to hunt down the killer for revenge. To prove this theory, a king cobra was captured and left free in an enclosure which had small openings. Numerous people stood in front of the openings but the snake rose to its full height and locked eyes only with the captor. Due to this myth, whenever a cobra is killed, especially in India, the head is either crushed or burned to damage the eyes completely.[5]

Wikimedia Commons has media related to Ophiophagus hannah.
Wikispecies has information related to Ophiophagus hannah.

References

  1. ^ a b c d e f g Mehrtens, John (1987). Living Snakes of the World. New York: Sterling. ISBN 0-8069-6461-8.
  2. ^ a b c d e f g h Mark O'Shea. Venomou snakes of the world. ISBN 978-0-691-15023-9. Average venom yield is 200-500 mg;an adult king cobra is not only the most impressive of all snakes but also one of the most dangerous.
  3. ^ a b c d e Davidson, Terence. "IMMEDIATE FIRST AID". University of California, San Diego. Retrieved 24 September 2011.
  4. ^ a b c "Ophiophagus hannah". the King Cobra is undoubtedly a very dangerous snake(section of "Behavior")
  5. ^ a b In India, the cobra in general is also associated with the two principal gods, Shiva and Vishnu. Shiva, the "destroyer" ascetic warrior, wears one around his neck. Vishnu is shielded from the sun by a gigantic five-headed cobra called Kaliya, who was once his enemy. Serpentine inhabitants of the underworld known as nagas also mostly resemble cobras. Taylor, David (1997). "King Cobra" (Document). National Geographic Magazine. {{cite document}}: Unknown parameter |accessdate= ignored (help); Unknown parameter |archivedate= ignored (help); Unknown parameter |archiveurl= ignored (help); Unknown parameter |url= ignored (help)
  6. ^ Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0-85112-235-9
  7. ^ a b Venomous Land Snakes, Dr.Willott. Cosmos Books Ltd. ISBN 988-211-326-5.
  8. ^ a b c d e f g "National geographic- KING COBRA". They are fiercely aggressive when cornered (line 28-29);average life span in the wild: 20 years (fast facts)
  9. ^ Miller, Harry (September 1970). "The Cobra, India's 'Good Snake'". National Geographic. 20: 393–409.
  10. ^ "CITES List of animal species used in traditional medicine". Retrieved 1 September 2007.
  11. ^ Philadelphia Zoo - King cobra
  12. ^ a b c Capula, Massimo (1989). Simon & Schuster's Guide to Reptiles and Amphibians of the World. New York: Simon & Schuster. ISBN 0-671-69098-1. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  13. ^ a b c d e Coborn, John (October 1991). The Atlas of Snakes of the World. TFH Publications. pp. 30, 452. ISBN 978-0-86622-749-0.
  14. ^ Reptile Knowledge (King cobra)
  15. ^ Dr. Zoltan Takacs. "Why the cobra is resistant to its own venom". Retrieved 5 September 2007.
  16. ^ King Cobras, the largest venomous snakes, by Sjon Hauser, website accessed 11 August 2012
  17. ^ Provider: John Wiley & Sons, Ltd Content:text/plain; charset="UTF-8" TY - JOUR AU - Young, Bruce A. TI - Morphological basis of "growling" in the king cobra, Ophiophagus hannah JO - Journal of Experimental Zoology JA - J. Exp. Zool. VL - 260 IS - 3 PB - Wiley Subscription Services, Inc., A Wiley Company SN - 1097-010X UR - http://dx.doi.org/10.1002/jez.1402600302 DO - 10.1002/jez.1402600302 SP - 275 EP - 287 PY - 1991
  18. ^ Piper, Ross (2007). Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Westport, Connecticut: Greenwood Press. ISBN 0-313-33922-8.
  19. ^ National Geographic Program 17 May 2009
  20. ^ a b "Structural and Functional Characterization of a Novel Homodimeric Three-finger Neurotoxin from the Venom of Ophiophagus hannah (King Cobra)".
  21. ^ Dr. Bryan Grieg Fry. "LD50 menu".
  22. ^ Séan Thomas & Eugene Griessel - Dec 1999. "LD50".{{cite web}}: CS1 maint: numeric names: authors list (link)
  23. ^ a b Engelmann, Wolf-Eberhard (1981). Snakes: Biology, Behavior, and Relationship to Man. Leipzig; English version NY, USA: Leipzig Publishing; English version published by Exeter Books (1982). p. 222. ISBN 0-89673-110-3.
  24. ^ Handbook of clinical toxicology of animal venoms and poisons. Vol. 236. USA: CRC Press. 1995. p. 768. ISBN 0-8493-4489-1.
  25. ^ a b Snake of medical importance. Singapore: Venom and toxins research group. ISBN 9971-62-217-3.
  26. ^ Carroll, Sean B. (25 October 2010). "science-the king cobra". The New York Times.
  27. ^ a b c "Snake-bite Envenomation: A Comprehensive Evaluation of Severity, Treatment and Outcome in a tertiary Care South Indian Hospital". South Indian Hospital.
  28. ^ Mortality Rate
  29. ^ "University of Adelaide Clinical Toxinology Resources".
  30. ^ "Munich AntiVenom Index:Ophiophagus hannah". Munich Poison Center. MAVIN (Munich AntiVenom Index). 01/02/2007. Retrieved 2 September 2007. {{cite web}}: Check date values in: |date= (help)
  31. ^ Pung, Y.F., Kumar, S.V., Rajagopalan, N., Fry, B.G., Kumar, P.P., Kini, R.M. 2006 Ohanin, a novel protein from king cobra venom: Its cDNA and genomic organization. Gene 371 (2):246–256
  32. ^ Rajagopalan, N., Pung, Y.F., Zhu, Y.Z., Wong, P.T.H., Kumar, P.P., Kini, R.M. 2007 β-Cardiotoxin: A new three-finger toxin from Ophiophagus hannah (King Cobra) venom with beta-blocker activity. FASEB Journal 21 (13):3685–3695
  33. ^ Chang, L.-S., Liou, J.-C., Lin, S.-R., Huang, H.-B. 2002Purification and characterization of a neurotoxin from the venom of Ophiophagus hannah (king cobra). Biochemical and Biophysical Research Communications 294 (3):574–578
  34. ^ Ernst, Carl H. & Evelyn M. (2011). Venomous Reptiles of the United States, Canada, and Northern Mexico: Heloderma, Micruroides, Micrurus, Pelamis, Agkistrodon, Sistrurus. JHU Press. pp. 44–45. ISBN 978-0-8018-9875-4.
  35. ^ "King Cobra venom may lead to a new drug".

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