Philippine cobra: Difference between revisions
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==Venom== |
==Venom== |
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The [[Venom (poison)|venom]] of the Philippine cobra is a potent postsynaptic [[neurotoxin]] which affects respiratory function and can cause [[neurotoxicity]] and respiratory paralysis, as the neurotoxins interrupt the transmission of nerve signals by binding to the neuro-muscular junctions near the muscles. They are capable of accurately spitting their venom at a target that is up to {{convert|3|m|ft}} away from where they are. The symptoms of a bite might include headache, nausea, vomiting, abdominal pain, diarrhea, dizziness, and difficulty breathing.<ref>[http://emedicine.medscape.com/article/771918-treatment#a1125 Envenomation and Treatment]</ref> |
The [[Venom (poison)|venom]] of the Philippine cobra is a potent postsynaptic [[neurotoxin]] which affects respiratory function and can cause [[neurotoxicity]] and respiratory paralysis, as the neurotoxins interrupt the transmission of nerve signals by binding to the neuro-muscular junctions near the muscles. Research done on the venom of this species has shown that its venom is purely a neurotoxin, with no apparent necrotizing components and no [[cardiotoxicity|cardiotoxins]].<ref name=Toxicity/> They are capable of accurately spitting their venom at a target that is up to {{convert|3|m|ft}} away from where they are. The symptoms of a bite might include headache, nausea, vomiting, abdominal pain, diarrhea, dizziness, and difficulty breathing.<ref>[http://emedicine.medscape.com/article/771918-treatment#a1125 Envenomation and Treatment]</ref> Bites by the Philippine cobra produce prominent neurotoxicity with minimal to no local signs. A study of 39 patients envenomed by the Philippine cobra (''Naja philippinensis'') was conducted in 1988. Neurotoxicity occurred in 38 cases and was the predominant clinical feature. Respiratory paralysis developed in 19 patients, and was often rapid in onset-in 3 cases apnea occurred within 30 minutes of the bite. There were 2 deaths, both in patients who were moribund upon arrival at the hospital. Three patients developed necrosis, and 14 individuals with systemic symptoms had no local swelling at all. Both cardiotoxicity and reliable nonspecific signs of envenoming were absent. Bites by the Philippine cobra produce a distinctive clinical picture characterized by severe neurotoxicity of rapid onset and minimal local tissue damage.<ref name=Toxicity>{{cite journal|last=Watt|first=G.|coauthors=Padre L, Tuazon L, Theakston RD, Laughlin L.|title=Bites by the Philippine cobra (Naja naja philippinensis): prominent neurotoxicity with minimal local signs.|journal=The American Journal of Tropical Medicine and Hygeine|year=1988|month=September|volume=39|issue=3|pages=306-11|pmid=3177741|url=http://www.ncbi.nlm.nih.gov/pubmed/3177741|accessdate=1 December 2011}}</ref> |
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Although venom toxicity values can vary greatly even among specimens of the same species, the Philippine cobra has the most toxic venom among all of the ''Naja'' (cobra) species according to all known toxicological studies which give the species a value, thus making it the most venomous cobra species in the world.<ref name=Brown73/> The [[Subcutis|subcutaneous]] {{LD50}} for this species is around 0.20 mg/kg, the average venom yield per bite is 90-100 mg (with a maximum yield of 250 mg - dry weight), while 20-25 mg being the approximate lethal human dose.<ref name=Brown73/> The mortality rate for untreated bites is moderate at 30-35%.<ref name=Brown73/><ref name=Toxicity/><ref name="ErZug">{{cite book|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> In comparison, the corresponding {{LD50}} for ''Naja naja'' ([[Indian cobra]]) venom is 0.85 mg/kg according to both Brown<ref name=Brown73>{{cite book|last=Brown|first=JH|title=Toxicology and Pharmacology of Venoms from Poisonous Snakes.|year=1973|publisher=Charles C. Thomas|location=Springfield, Illinois|isbn=0-398-02808-7|lcccn=73-229|pages=184}}</ref> and Ernst and Zug et al. 1996.<ref name="ErZug"/> Dr. Bryan Grieg Fry gives the Indian cobra a value of 0.45 mg/kg, but this isn't consistent with most toxicology studies.<ref name=VenDoc/> [[Subcutis|SC]] {{LD50}} values for other cobra's include 1.15 mg/kg for ''Naja haje'' ([[Egyptian cobra]]),<ref name=VenDoc>{{cite web|last=Fry|first=Bryan Grieg|title=Subcutaneous LD50|url=http://www.venomdoc.com/LD50/ld50sc.html|work=Australian Venom Research Unit|publisher=University of Queensland|accessdate=1 December 2011}}</ref> 2 mg/kg for ''Naja nigricollis'' ([[Naja nigricollis|Black-necked spitting cobra]])<ref name=VenDoc/>, 0.72 mg/kg for ''Naja nivea'' ([[Cape cobra]])<ref name=VenDoc/>, and 0.53 mg/kg for ''Naja atra'' ([[Naja atra|Chinese cobra]]).<ref name=Brown73/> |
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==External links== |
==External links== |
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Revision as of 22:44, 1 December 2011
| Philippine Cobra | |
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| Scientific classification | |
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| Species: | N. philippinensis
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| Binomial name | |
| Naja philippinensis (Taylor, 1922)[verification needed]
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The Philippine Cobra (Naja philippinensis) is a stocky, highly venomous spitting cobra native to the Philippines. The Philippine Cobra is called "ulupong" in Tagalog and "Agwason" in Cebuano-Bisaya.
Description
The Philippine cobra is a stocky snake of medium length that has long cervical ribs capable of expanding, so that when threatened a hood can be formed. The average length of this species is 1.0 metre (3.3 ft).[1] The species can grow to lengths of 1.6 metres (5.2 ft)[1] However, sub-populations of the species, particularly specimens from Mindoro Island, are said to attain lengths of 2 metres (6.6 ft), but these are unverified and unconfirmed claims. If true, however, 2 metres (6.6 ft) would be very rare and would be considered the absolute maximum for this species.[2] The head is elliptical, depressed, slightly distinct from neck with a short, rounded snout and large nostrils. The eyes are moderate in size with dark brown and round pupils, typical of other cobra species and similar to other elapids in general. It has a fairly stocky build for an elapid and adult snakes are uniformly light to medium brown, while the juveniles tend to be a darker brown in color.[1] They have 23-27 scale rows around the neck and 21 just above the middle part of the body; 182-193 ventrals, 36-49 subcaudals, and basal pairs are sometimes undivided.[1][3]
Distribution
The Philippine cobra occurs in the Philippines. They can be found on the islands of Luzon, Mindoro, Catanduanes, Samar, Eastern Samar, Southern Leyte and Masbate. It is also likely that this species may occur in other neighboring islands, but this remains unconfirmed. Records from the Calamianes group and Palawan require confirmation.[4]
Habitat
Philippine cobra’s habitat include low-lying plains and forested regions,[1] along with open fields, grasslands, dense jungle, agricultural fields, and human settlements. This species of cobra is particularly fond of water and it can always be found very close to ponds, rivers, or large puddles of water.[1][5]
Diet
This species feeds predominantly on small mammals, frogs, and even other snakes.[1] Small rodents such as mice and small rats are their preferred prey and makeup the majority of their diet. However, they will also eat other snakes, including juvenile King cobra's, small lizards, frogs, eggs, and when the opportunity arises, small birds are taken aswell.[3][2]
Predators
Predators of this species of cobra include humans, birds of prey, the King cobra, and the mongoose.[5] Large rats that have been bitten by this snake who are in a position to fight back, often do so. Although rare, large rats have been known to fatally wound the snake by scratching, biting, or even poking one or both of the snakes eyes out. Of course, the rat ends up succumbing to the venom, but the snake will often end up being blind in one or usually both eyes and severe bites to the snout region leaves the snake vulnerable to all sorts of infections and diseases.[2]
Venom
The venom of the Philippine cobra is a potent postsynaptic neurotoxin which affects respiratory function and can cause neurotoxicity and respiratory paralysis, as the neurotoxins interrupt the transmission of nerve signals by binding to the neuro-muscular junctions near the muscles. Research done on the venom of this species has shown that its venom is purely a neurotoxin, with no apparent necrotizing components and no cardiotoxins.[6] They are capable of accurately spitting their venom at a target that is up to 3 metres (9.8 ft) away from where they are. The symptoms of a bite might include headache, nausea, vomiting, abdominal pain, diarrhea, dizziness, and difficulty breathing.[7] Bites by the Philippine cobra produce prominent neurotoxicity with minimal to no local signs. A study of 39 patients envenomed by the Philippine cobra (Naja philippinensis) was conducted in 1988. Neurotoxicity occurred in 38 cases and was the predominant clinical feature. Respiratory paralysis developed in 19 patients, and was often rapid in onset-in 3 cases apnea occurred within 30 minutes of the bite. There were 2 deaths, both in patients who were moribund upon arrival at the hospital. Three patients developed necrosis, and 14 individuals with systemic symptoms had no local swelling at all. Both cardiotoxicity and reliable nonspecific signs of envenoming were absent. Bites by the Philippine cobra produce a distinctive clinical picture characterized by severe neurotoxicity of rapid onset and minimal local tissue damage.[6]
Although venom toxicity values can vary greatly even among specimens of the same species, the Philippine cobra has the most toxic venom among all of the Naja (cobra) species according to all known toxicological studies which give the species a value, thus making it the most venomous cobra species in the world.[8] The subcutaneous LD50 for this species is around 0.20 mg/kg, the average venom yield per bite is 90-100 mg (with a maximum yield of 250 mg - dry weight), while 20-25 mg being the approximate lethal human dose.[8] The mortality rate for untreated bites is moderate at 30-35%.[8][6][9] In comparison, the corresponding LD50 for Naja naja (Indian cobra) venom is 0.85 mg/kg according to both Brown[8] and Ernst and Zug et al. 1996.[9] Dr. Bryan Grieg Fry gives the Indian cobra a value of 0.45 mg/kg, but this isn't consistent with most toxicology studies.[10] SC LD50 values for other cobra's include 1.15 mg/kg for Naja haje (Egyptian cobra),[10] 2 mg/kg for Naja nigricollis (Black-necked spitting cobra)[10], 0.72 mg/kg for Naja nivea (Cape cobra)[10], and 0.53 mg/kg for Naja atra (Chinese cobra).[8]
External links
- U.S. Naval Medical Research
- Naja philippinensis
- "Naja philippinensis - Mario Lutz`s HerpaWorld Institute"
- "Wolfgang Wüster's - Asiatic Cobra Page"
- LUTZ, M . (2006) Die Kobras des philippinischen Archipels - Teil I: Die Philippinen-Kobra, Naja philippinensis TAYLOR, 1922, SAURIA, Berlin, 28 (3): 31-37
References
- ^ a b c d e f g "Naja philippinensis". Clinical Toxinology Resource. The University of Adelaide. Retrieved 1 December 2011.
- ^ a b c Lutz, M. 2006. Die Kobras des philippinischen Archipels, Teil I: Die Philippinen-Kobra, Naja philippinensis TAYLOR 1922. Sauria 28 (3): 5-11
- ^ a b Wüster, Wolfgang (1993). "A century of confusion: Asiatic cobras revisited" (PDF). Vivarium. 4 (4): 14–18. Retrieved 1 December 2011.
- ^ WÜSTER, Wolfgang (1996). Toxicon. 34 (4): 399–406. doi:0041-0101(95)00139-5 http://pages.bangor.ac.uk/~bss166/Publications/ToxiconCobras.pdf. Retrieved 1 December 2011.
{{cite journal}}: Check|doi=value (help); Missing or empty|title=(help) - ^ a b WÜSTER , W. & R.S. THORPE (1990) Systematics and biogeography of the Asiatic cobra (Naja naja) species complex in the Philippine Islands. In G. Peters & R. Hutterer (Eds.), Vertebrates in the Tropics: 333-344. Museum A. Koenig, Bonn (Naja naja) species complex in the Philippine Islands
- ^ a b c Watt, G. (1988). "Bites by the Philippine cobra (Naja naja philippinensis): prominent neurotoxicity with minimal local signs". The American Journal of Tropical Medicine and Hygeine. 39 (3): 306–11. PMID 3177741. Retrieved 1 December 2011.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help); Unknown parameter|month=ignored (help) - ^ Envenomation and Treatment
- ^ a b c d e Brown, JH (1973). Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. p. 184. ISBN 0-398-02808-7.
{{cite book}}: Unknown parameter|lcccn=ignored (help) - ^ a b Zug, George R. (1996). Snakes in Question: The Smithsonian Answer Book. Washington D.C., USA: Smithsonian Institution Scholarly Press. ISBN 1560986484.
- ^ a b c d Fry, Bryan Grieg. "Subcutaneous LD50". Australian Venom Research Unit. University of Queensland. Retrieved 1 December 2011.