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|+ Most venomous land snakes (Ernst and Zug ''et al.'' 1996)<ref name="ErZug">{{cite book |last= Ernst|first= Carl H.|last= Zug|first= George R.|title= Snakes in Question: The Smithsonian Answer Book |year= 1996|publisher= Smithsonian Institution Scholarly Press |location= Washington D.C., USA|isbn= 1560986484}}</ref><ref>[http://www.venomdoc.com/LD50/LD50men.html LD50 Toxicology Study (Dr. Bryan Grieg Fry)]</ref>
|+ Most venomous land snakes (Ernst and Zug ''et al.'' 1996)<ref name="ErZug">{{cite book |last= Ernst|first= Carl H.|last= Zug|first= George R.|title= Snakes in Question: The Smithsonian Answer Book |year= 1996|publisher= Smithsonian Institution Scholarly Press |location= Washington D.C., USA|isbn= 1560986484}}</ref><ref>[http://www.venomdoc.com/LD50/LD50men.html LD50 Toxicology Study (Dr. Bryan Grieg Fry)]</ref>
|-
|-
| '''Snake''' || '''Region''' || '''[[subcutaneous injection|SC]] {{LD50}}'''
| '''Snake''' || '''Region''' || '''[[subcutaneous injection|SC]] {{LD50}}''' || '''Venom yield average (mg)'''
|-
|-
| [[Inland taipan]] || Australia || 0.025&nbsp;mg/kg
| [[Inland taipan]] || Australia || 0.025&nbsp;mg/kg || 44
|-
|-
| [[Pseudonaja textilis|Eastern brown snake]] || Australia || 0.0365&nbsp;mg/kg
| [[Pseudonaja textilis|Eastern brown snake]] || Australia || 0.0365&nbsp;mg/kg || 2
|-
|-
| [[Coastal Taipan|Coastal taipan]] || Australia, New Guinea || 0.106&nbsp;mg/kg
| [[Coastal Taipan|Coastal taipan]] || Australia, New Guinea || 0.106&nbsp;mg/kg || 100
|-
|-
| [[Bungarus multicinctus|Many-banded krait]] || China, Taiwan, Burma, Laos, Vietnam || 0.108&nbsp;mg/kg
| [[Bungarus multicinctus|Many-banded krait]] || China, Taiwan, Burma, Laos, Vietnam || 0.108&nbsp;mg/kg || 10
|-
|-
| [[Tiger snake|Peninsula tiger snake]] || Australia || 0.131&nbsp;mg/kg
| [[Tiger snake|Peninsula tiger snake]] || Australia || 0.131&nbsp;mg/kg || 34
|-
|-
| [[Echis carinatus|Saw-scaled viper]] || Asia; Indian subcontinent || 0.151&nbsp;mg/kg
| [[Echis carinatus|Saw-scaled viper]] || Asia; Indian subcontinent || 0.151&nbsp;mg/kg || 18
|-
|-
| [[Black Mamba]] || Sub-Saharan Africa || 0.185&nbsp;mg/kg
| [[Black Mamba]] || Sub-Saharan Africa || 0.185&nbsp;mg/kg || 120
|-
|-
| [[Tiger snake|Western tiger snake]] || Australia || 0.194&nbsp;mg/kg
| [[Tiger snake|Western tiger snake]] || Australia || 0.194&nbsp;mg/kg || 35
|-
|-
| [[Micrurus fulvius|Eastern coral snake]] || Northeast Mexico, southeast U.S. || 0.196&nbsp;mg/kg
| [[Micrurus fulvius|Eastern coral snake]] || Northeast Mexico, southeast U.S. || 0.196&nbsp;mg/kg || 2
|-
|-
| [[Philippine cobra]] || Philippines || 0.20&nbsp;mg/kg
| [[Philippine cobra]] || Philippines || 0.20&nbsp;mg/kg || 90
|}
|}


Revision as of 04:32, 15 March 2012

"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.

The Indian cobra (Naja naja), one of the most recognizable venomous snakes

Venomous snakes have venom glands and specialized teeth for the injection of venom. Members of the families Elapidae, Viperidae, Hydrophiidae, and Atractaspididae (and some from Colubridae, as well) are major venomous snakes.

Description

Venomous snakes use modified saliva, snake venom, usually delivered through highly specialized teeth, such as hollow fangs, for the purpose of prey immobilization and self-defense. In contrast, nonvenomous species either constrict their prey, or simply overpower it with their jaws.

Venomous snakes include several families of snakes and do not form a single taxonomic group. This has been interpreted to mean venom in snakes originated more than once as the result of convergent evolution. Evidence has recently been presented for the Toxicofera hypothesis; however, venom was present (in small amounts) in the ancestors of all snakes (as well as several lizard families) as 'toxic saliva' and evolved to extremes in those snake families normally classified as venomous by parallel evolution. The Toxicofera hypothesis further implies that 'nonvenomous' snake lineages have either lost the ability to produce venom (but may still have lingering venom pseudogenes), or actually do produce venom in small quantities, likely sufficient to assist in small prey capture, but cause no harm to humans if bitten.

Most venomous snake

Most venomous land snakes (Ernst and Zug et al. 1996)[1][2]
Snake Region SC LD50 Venom yield average (mg)
Inland taipan Australia 0.025 mg/kg 44
Eastern brown snake Australia 0.0365 mg/kg 2
Coastal taipan Australia, New Guinea 0.106 mg/kg 100
Many-banded krait China, Taiwan, Burma, Laos, Vietnam 0.108 mg/kg 10
Peninsula tiger snake Australia 0.131 mg/kg 34
Saw-scaled viper Asia; Indian subcontinent 0.151 mg/kg 18
Black Mamba Sub-Saharan Africa 0.185 mg/kg 120
Western tiger snake Australia 0.194 mg/kg 35
Eastern coral snake Northeast Mexico, southeast U.S. 0.196 mg/kg 2
Philippine cobra Philippines 0.20 mg/kg 90

Lists or rankings of the world's "most venomous snakes" are tentative and differ greatly due to numerous factors, including the age and reliability of the data, the number of species analyzed, and the testing methods used.[3] In addition, since mice are the common indicator used to test venom from venomous snakes in LD50 tests, the LD50 results may not reflect the actual effects on humans due to the physiological differences between mice and humans. For example, many venomous snakes are specialized predators on mice, and their venom may be adapted specifically to incapacitate mice. While most mammals have a very similar physiology, LD50 results may or may not be directly relevant to humans. Sometimes, results from different tests may cause confusion, as different toxicity scales are in use.[4]

While there have been numerous studies on snake venom, potency estimates can vary,[5] creating overlap and greatly complicating the task. Further, LD50 may be measured through intramuscular, intraperitoneal, intravenous or subcutaneous injections on small rodents, although the latter is the most applicable to actual bites.[3] Mice, the most commonly used animals in determining LD50, may react to some snake venoms differently from humans; this may be why some species of snake show high toxicity when tested on mice, but have surprisingly low mortality rates in untreated human bites (for example, the eastern coral snake, Philippine cobra, and even the eastern brown snake).[6] Based on medical literature dating back from the early 1900s to the present, the most venomous or deadliest snake to humans has been the black mamba. The species has the most rapid-acting venom of any snake[7] and it carries a 100% mortality rate in untreated cases of human envenomation.[8][9][10][11][12][13][14] Another snake with a similar reputation is the coastal taipan, which has an untreated mortality rate of 95–99% in humans, second only to the black mamba. Although more venomous than the black mamba, the coastal taipan's venom is slower to act; in some cases in the medical literature, people have survived coastal taipan bites without any kind of medical treatment, although this is very rare. The eastern brown snake's venom is nearly three times more potent than the coastal taipan's, yet to humans the untreated mortality rate for the eastern brown snake is somewhere between 10 and 20%, far lower than both the black mamba and coastal taipan.[12][15][16]

Another important factor is the venom yield. Some snakes may have very potent venom, but are unable to produce much. Others may have less-toxic venom, but are able to produce vast quatities, making them more lethal. Yet others are able to replenish their supplies quickly, allowing multiple strikes. To determine how lethal a snake bite might be, the LD50 is only one of many factors. Some snakes also live in the desert (inland taipan, for example) and present little problem, while those that live where humans live could be considered more dangerous (common cobra).

Many of these lists only take into account of terrestrial and arboreal snakes and neglect to list the of venom of the sea snakes. Species of sea snakes have been listed to have more toxic venom than even that of the inland taipan and further investigations of some species' venom are needed.

Other information

Venomous snakes are often said to be poisonous, although this is not the correct term, as venoms and poisons are different. Poisons can be absorbed by the body, such as through the skin or digestive system, while venoms must first be introduced directly into tissues or the blood stream (envenomated) through mechanical means. It is, for example, harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract. The two exceptions are: the Rhabdophis keelback snakes secrete poison from glands they get from the poisonous toads they consume, and similarly, certain garter snakes from Oregon retain toxins in their livers from the newts they eat.[17]

Families of venomous snakes

Over 600 species are known to be venomous—about a quarter of all snake species. The following table lists some major species.

Family Description
Atractaspididae (atractaspidids) Burrowing asps, mole vipers, stiletto snakes
Colubridae (colubrids) Most are harmless, but others have toxic saliva and at least five species, including the boomslang (Dispholidus typus), have caused human fatalities.
Elapidae (elapids) Sea snakes, taipans, brown snakes, mambas, coral snakes, kraits, king cobra, death adders, tiger snakes, and cobras
Viperidae (viperids) True vipers, including the Russell's viper, saw-scaled vipers, puff adders and pit vipers, including rattlesnakes, lanceheads, and copperheads and cottonmouths.

See also

References

  1. ^ Zug, George R. (1996). Snakes in Question: The Smithsonian Answer Book. Washington D.C., USA: Smithsonian Institution Scholarly Press. ISBN 1560986484.
  2. ^ LD50 Toxicology Study (Dr. Bryan Grieg Fry)
  3. ^ a b Fry, Bryan Grieg. "Snake LD50 – discussion". Australian Venom & Toxin Database. Retrieved 2009-09-28. Subcutaneous is the most applicable to actual bites. Only large Bitis or extremely large Bothrops or Crotalus specimens would be able to deliver a bite that is truly intramuscular. IV injections are extremly rare in actual bites.
  4. ^ "What is an LD50 and LC50".
  5. ^ Mackessy, Stephen P. (2002). "Biochemistry and pharmacology of colubrid snake venoms" (PDF). Journal of Toxicology: Toxin Reviews. 21 (1–2): 43–83. doi:10.1081/TXR-120004741. Retrieved 2009-09-26. {{cite journal}}: Unknown parameter |month= ignored (help)
  6. ^ "Venom variability". Women's & Children's Hospital – Clinical Toxinology Resources. University of Adelaide. Retrieved 28 September 2009. The rough scaled snake, Tropidechis carinatus has a much less potent venom than the tiger snake, Notechis scutatus, on LD50 testing in mice. Yet clinically, the two venoms are virtually identical in the type and severity of effects on envenomed humans.
  7. ^ Brown, JH (1973). Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. p. 184. ISBN 0-398-02808-7. LCCN 73–229. {{cite book}}: Check |lccn= value (help)
  8. ^ "Black mamba". National Geographic Society. Retrieved 2010-03-12.
  9. ^ Mitchell, Deborah (September 2009). The Encyclopedia of Poisons and Antidotes. New York, USA: Facts on File, Inc. p. 324. ISBN 0816064016.
  10. ^ Davidson, Terence. "IMMEDIATE FIRST AID". University of California, San Diego. Retrieved 2011-12-01.
  11. ^ National Geographic – Black Mamba
  12. ^ a b Mortality rate
  13. ^ Nature-Black Mamba
  14. ^ Black Mamba Intro
  15. ^ Clinical Toxinology Resource (Pseudonaja textilis) Mortality Rate
  16. ^ "IMMEDIATE FIRST AID for bites by Australian Taipan or Coastal Taipan".
  17. ^ Klauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. University of California Press, Berkeley. ISBN 0-520-21056-5.
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