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Mamba

For other uses, see Mamba (disambiguation).

Mambas are fast-moving, highly venomous snakes of the genus Dendroaspis (which literally means "tree asp") in the family Elapidae. Four extant species are recognised currently; three of those four species are essentially arboreal and green in colour, whereas the black mamba, Dendroaspis polylepis, is largely terrestrial and generally brown or grey in colour. All are native to various regions in sub-Saharan Africa and all are feared throughout their ranges, especially the black mamba. In Africa there are many legends and stories about mambas.[2][3][4]

Mamba
Black mamba
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Subfamily: Elapinae
Genus: Dendroaspis
Schlegel, 1848[1]
Species
  D. polylepis   
  D. angusticeps
  D. viridis

Behaviour

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The three green species of mambas are arboreal, whereas the black mamba is largely terrestrial. All four species are active diurnal hunters, preying on birds, lizards, and small mammals. At nightfall some species, especially the terrestrial black mamba, shelter in a lair. A mamba may retain the same lair for years. Resembling a cobra, the threat display of a mamba includes rearing, opening the mouth and hissing. The black mamba's mouth is black within, which renders the threat more conspicuous. A rearing mamba has a narrower yet longer hood and tends to lean well forward, instead of standing erect as a cobra does.

Stories of black mambas that chase and attack humans are common, but in fact the snakes generally avoid contact with humans.[5] The black mamba (Dendroaspis polylepis) is a highly venomous snake species native to various parts of sub-Saharan Africa. Black mambas are fast-moving, nervous snakes that will strike when threatened. According to findings by Branch (2016), their venom comprises neurotoxins and cardiotoxins that can rapidly induce symptoms, including dizziness, extreme fatigue, vision problems, foaming at the mouth, paralysis, convulsions, and eventual death from respiratory or cardiac failure if untreated. Although black mamba venom is highly toxic, antivenom is available and can treat envenomation promptly.

Most apparent cases of pursuit probably are examples of where witnesses have mistaken the snake's attempt to retreat to its lair when a human happens to be in the way.[6] The black mamba usually uses its speed to escape from threats, and humans actually are their main predators, rather than prey.[2]

Venom

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All mambas have medically significant venom, with dendrotoxins, short chain alpha-neurotoxins, cardiotoxins and fasciculins.[7][2][8] All mambas are classified as snakes of medical importance by the World Health Organization.[9][a]

There are multiple components in dendrotoxins with different targets:

  • Dendrotoxin 1, which inhibits the K+ channels at the pre and post-synaptic level in the intestinal smooth muscle. It also inhibits Ca2+-sensitive K+ channels from rat skeletal muscle‚ incorporated into planar bilayers (Kd = 90 nM in 50 mM KCl).[10])
  • Dendrotoxin 3, which inhibits acetylcholine M4 receptors.[11]
  • Dendrotoxin 7, commonly referred to as muscarinic toxin 7 (MT7) inhibits acetylcholine M1 receptors.[11]
  • Dendrotoxin K, structurally homologous to Kunitz-type proteinase inhibitors[12] with activity as a selective blocker of voltage-gated potassium channels[13]

Toxicity alone does not determine severity of envenomation; other factors include the snake's temperament, venom yields, proximity of wounds to the CNS and depth of punctures.[14] Bites by all members of this genus are capable of causing rapid onsets of symptoms, but it is the black mamba whose bite has the worst prognosis, possibly as a result of its more terrestrial nature (having more potential for human contact), high defensiveness (having a higher possibility to deliver fatal bites instead of dry bites), large size (giving it a higher strike position proximal to the victim's brain), and higher average venom yields and potential toxicity (based on experimental results).[15][16] A lethality rate of near 100% for untreated black mamba bites has been circulating between various sources,[16] which is probably based on a single medical record made in a single district between 1957 and 1963 when specific antivenom had yet to be introduced. Seven out of seven victims of this species who received non-specific polyvalent antivenom, that had no effect on the species' toxins, succumbed to its bites.[5] However, another snakebite survey in South Africa reported a death rate of approximately 43% among those who received ineffective treatments (15 fatal cases out of 35 patients).[17] A mamba-specific antivenom was introduced in 1962, followed by a fully polyvalent antivenom in 1971; over this period, 5 out of 38 people in South Africa bitten by black mambas who received the antivenom died, according to the same report.[17] Since then, the number has significantly dropped with the widespread use of specific antivenom.[18][17]

Despite their fearsome reputation and often exaggerated notoriety, mamba envenomation occurs far less frequently than some other snakes', for instance the puff adder.[16][5] Besides proximity to residences, behaviour of a given species is also a critical aspect when it comes to snakebite morbidities. Mambas are agile, usually fleeing from any confrontation with unambiguous threat display which allows early recognition of the serpent, avoiding escalation in tension.[17]

Taxonomy

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Dendroaspis, is derived from Ancient Greek déndron (δένδρον), meaning "tree",[19] and aspis (ασπίς), which is understood to mean "shield",[20] but also denotes "cobra" or simply "snake", in particular "snake with hood (shield)". Via Latin aspis, it is the source of the English word "asp". In ancient texts, aspis or asp often referred to the Egyptian cobra (Naja haje), in reference to its shield-like hood.[21] The genus was first described by the German naturalist Hermann Schlegel in 1848,[22] with Elaps jamesonii as the type species. It was misspelt as Dendraspis by Dumeril in 1856, and generally uncorrected by subsequent authors. In 1936, Dutch herpetologist Leo Brongersma pointed out that the correct spelling was Dendroaspis but added that the name was invalid as Fitzinger had coined Dendraspis in 1843 for the king cobra and hence had priority.[23] However, in 1962 German herpetologist Robert Mertens proposed that the 1843 description of Dendraspis by Fitzinger be suppressed due to its similarity to Dendroaspis, and the confusion it would cause by its use.[24]

Range and characteristics

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Black mambas live in the savannas and rocky hills of southern and eastern Africa. They are Africa's longest venomous snake, reaching up to 14 feet in length, although 8.2 feet is more the average. They are also among the fastest snakes in the world, slithering at speeds of up to 12.5 miles per hour.[2][6]

Species[25] Authority[25][b] Image Subsp.*[25] Common name Geographic range
Dendroaspis angusticeps (Smith, 1849)   0 Eastern green mamba Found in Kenya, Tanzania, Malawi, Mozambique, Zimbabwe, Eswatini, eastern South Africa
Dendroaspis jamesoniT (Traill, 1843)   2 Jameson's mamba Found in Central Africa in South Sudan, Gabon, Angola, Zambia, Republic of the Congo, Democratic Republic of the Congo, Cameroon, Equatorial Guinea, Nigeria, Kenya, Uganda, Rwanda, Burundi, Tanzania, Central African Republic, Benin, Togo, Ghana
Dendroaspis polylepis Günther, 1864   0 Black mamba Found in northern Central Africa to eastern Africa and southern Africa in Cameroon, northern Republic of the Congo, Central African Republic, northeast Democratic Republic of the Congo, and southwestern Sudan to Ethiopia, Eritrea, Djibouti, Somalia, Kenya, eastern Uganda, Rwanda, Burundi, Tanzania, southwards to Mozambique, Eswatini, Malawi, Zambia, Zimbabwe, Lesotho, and Botswana to KwaZulu-Natal in South Africa, and Namibia; then northeasterly through Angola to the southeastern part of the Democratic Republic of Congo
Dendroaspis viridis (Hallowell, 1844)   0 Western green mamba Found only in western Africa in southern Senegal, Gambia, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Côte d’Ivoire, Ghana, Togo, Benin, and southwest Nigeria

* Including the nominate subspecies.
T Type species.

Phylogeny

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A 2018 analysis of the venom of the mambas, as well as a 2016 genetic analysis, found the following cladogram representative of the relationship between the species.[26][27]

Notes

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  1. ^ Snakes of medical importance include those with highly dangerous venom resulting in high rates of morbidity and mortality, or those that are common agents in snakebite.[9]
  2. ^ A binomial authority in parentheses indicates that the species was originally described in a genus other than Dendroaspis.

References

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  1. ^ "Dendroaspis". Integrated Taxonomic Information System. Retrieved 30 October 2012.
  2. ^ a b c d "National Geographic (Black Mamba, Dendroaspis polylepis)". National Geographic Society. 10 September 2010. Archived from the original on May 30, 2017. Retrieved 17 October 2020. African myths exaggerate their capabilities to legendary proportions; Black mambas are shy and will almost always seek to escape when confronted.
  3. ^ Jan Knappert (1 January 1985). Myths and Legends of Botswana, Lesotho, and Eswatini. Brill Archive. pp. 53–. ISBN 90-04-07455-4.
  4. ^ Alfred Burdon Ellis (1887). South African Sketches. Chapman and Hall, Limited. also at: [1]
  5. ^ a b c O'Shea, Mark (2005). VENOMOUS SNAKES OF THE WORLD. multiple places: US and Canada: Princeton University Press; Europe: New Holland (UK) Ltd. pp. 78–79. ISBN 978-0-691-15023-9. ...in common with other snakes they prefer to avoid contact;...Of the three species of green mambas...;...from 1957 to 1963...including all seven black mamba bites - a 100 per cent fatality rate
  6. ^ a b The new encyclopedia of Reptiles (Serpent). Time Book Ltd. 2002.
  7. ^ "Neurotoxins in Snake Venom". Retrieved 2019-12-26.
  8. ^ van Aswegen G, van Rooyen JM, Fourie C, Oberholzer G (May 1996). "Putative cardiotoxicity of the venoms of three mamba species". Wilderness & Environmental Medicine. 7 (2): 115–21. doi:10.1580/1080-6032(1996)007[0115:PCOTVO]2.3.CO;2. PMID 11990104.
  9. ^ a b WHO Expert Committee on Biological Standardization. "Guidelines for the production, control and regulation of snake antivenom immunoglobulins" (PDF). WHO Technical Report Series, No. 964. pp. 224–226. Retrieved 1 January 2019.
  10. ^ Newitt RA, Houamed KM, Rehm H, Tempel BL (1991). "[Potassium channels and epilepsy: evidence that the epileptogenic toxin, dendrotoxin, binds to potassium channel proteins.]". Epilepsy Research Supplement. 4: 263–73. PMID 1815606.
  11. ^ a b Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. p. 139. ISBN 0-443-07145-4.
  12. ^ Berndt KD, Güntert P, Wüthrich K (5 December 1993). "[Nuclear magnetic resonance solution structure of dendrotoxin K from the venom of Dendroaspis polylepis polylepis.]". Journal of Molecular Biology. 234 (3): 735–50. doi:10.1006/jmbi.1993.1623. PMID 8254670.
  13. ^ Harvey AL, Robertson B (2004). "Dendrotoxins: structure-activity relationships and effects on potassium ion channels". Curr. Med. Chem. 11 (23): 3065–72. doi:10.2174/0929867043363820. PMID 15579000.
  14. ^ Warrell, DA (1995). Meier, J; White, J (eds.). Handbook of Clinical Toxicology of Animal Venoms and Poisons (1 ed.). Boca Raton: CRC Press. pp. 433–492. ISBN 9781351443142.
  15. ^ Séan Thomas & Eugene Griessel – Dec 1999. "LD50 (Archived)". Archived from the original on 1 February 2012.{{cite web}}: CS1 maint: numeric names: authors list (link)
  16. ^ a b c Branch, W (January 1979). "The venomous snakes of Southern Africa Part 2. Elapidae and Hydrophidae". The Snake. 11 (2): 199–225. Retrieved 1 July 2021.
  17. ^ a b c d Christensen, P.A. (1981). "Snakebite and the use of antivenom in southern Africa" (PDF). South African Medical Journal. 59 (26): 934–938. PMID 7244896.
  18. ^ Nhachi, Charles FB; Kasilo, Ossy M. (1994). "Snake poisoning in rural Zimbabwe – A prospective study". Journal of Applied Toxicology. 14 (3): 191–193. doi:10.1002/jat.2550140308. PMID 8083480. S2CID 40171925.
  19. ^ "dendro-". Collins English Dictionary - Complete & Unabridged 10th Edition. HarperCollins Publishers. Retrieved 4 March 2014.
  20. ^ "Definition of "aspis" - Collins English Dictionary". collinsdictionary.com. Retrieved 15 February 2015.
  21. ^ "aspis, asp". Dictionary.com Unabridged. Random House. Retrieved 4 March 2014.
  22. ^ "Dendroaspis". Integrated Taxonomic Information System. Retrieved 9 December 2013.
  23. ^ Brongersma, Leo Daniel (1936). "Herpetological note XIII". Zoo. Mededeel. 19: 135.
  24. ^ Mertens, Robert (1962). "Dendraspis Fitzinger, 1843 (Reptilia, Serpentes); Proposed Suppression under the Plenary Powers. Z.N. (S.) 1500" (PDF). Bulletin of Zoological Nomenclature. 19: 189–190.
  25. ^ a b c "Dendroaspis". Integrated Taxonomic Information System. Archived from the original on 12 March 2009. Retrieved 5 July 2013.
  26. ^ Ainsworth, Stuart; Petras, Daniel; Engmark, Mikael; Süssmuth, Roderich D.; Whiteley, Gareth; Albulescu, Laura-Oana; Kazandjian, Taline D.; Wagstaff, Simon C.; Rowley, Paul; Wüster, Wolfgang; Dorrestein, Pieter C.; Arias, Ana Silvia; Gutiérrez, José M.; Harrison, Robert A.; Casewell, Nicholas R.; Calvete, Juan J. (2018). "The medical threat of mamba envenoming in sub-Saharan Africa revealed by genus-wide analysis of venom composition, toxicity and antivenomics profiling of available antivenoms". Journal of Proteomics. 172: 173–189. doi:10.1016/j.jprot.2017.08.016. hdl:10261/279110. PMID 28843532. S2CID 217018550.
  27. ^ Figueroa, A.; McKelvy, A. D.; Grismer, L. L.; Bell, C. D.; Lailvaux, S. P. (2016). "A species-level phylogeny of extant snakes with description of a new colubrid subfamily and genus". PLOS ONE. 11 (9): e0161070. Bibcode:2016PLoSO..1161070F. doi:10.1371/journal.pone.0161070. PMC 5014348. PMID 27603205.

Further reading

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