This is a good article. Follow the link for more information.

Black mamba

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Black mamba
Dendroaspis polylepis (14).jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Dendroaspis
Species:
D. polylepis
Binomial name
Dendroaspis polylepis
Black Mamba Range.svg
Distribution range of black mamba
Synonyms[3]

The black mamba (Dendroaspis polylepis) is an extremely venomous snake of the family Elapidae, and native to parts of sub-Saharan Africa. First described by Albert Günther in 1864, it is the longest species of venomous snake indigenous to the African continent; mature specimens generally exceed 2 metres (6.6 ft) and commonly attain 3 metres (10 ft). Specimens of 4.3 to 4.5 metres (14.1 to 14.8 ft) have been reported. Its skin colour varies from grey to dark brown. Juvenile black mambas tend to be paler than adults and darken with age.

Both terrestrial and arboreal, the black mamba inhabits savannah, woodlands, rocky slopes and, in some regions, dense forest. It is diurnal and is known to prey on hyrax, bushbabies and other small mammals, as well as birds. Over suitable surfaces, it is possibly the fastest species of snake, capable of at least 11 km/h (6.8 mph) over short distances. Adult mambas have few natural predators.

In a threat display, the mamba usually opens its inky-black mouth, spreads its narrow neck-flap and sometimes hisses. It is capable of striking at considerable range and may deliver a series of bites in rapid succession. Its venom is primarily composed of neurotoxins that often induce symptoms within ten minutes. Without antivenom, the bite is often fatal. Despite its reputation as formidable and highly aggressive, the black mamba usually attempts to flee from humans unless threatened or cornered. It is rated as least concern on the International Union for Conservation of Nature (IUCN)'s Red List of Endangered species.

Taxonomy[edit]

Although the black mamba had been known to missionaries[4] and residents,[5] before 1860, the first formal description was made by German-British zoologist Albert Günther in 1864.[2][3] A single specimen was one of many snake species collected by Dr John Kirk, a naturalist who accompanied Dr David Livingstone on the Second Zambesi expedition.[6] The specific epithet polylepis is derived from the Ancient Greek poly (πολύ) meaning "many" and lepis (λεπίς) meaning "scale".[7] The term "mamba" is derived from the Zulu word "imamba".[8] A local Ngindo name in Tanzania is ndemalunyayo "grass-cutter" as it supposedly clips grass.[9]

In 1873, German naturalist Wilhelm Peters described Dendraspis Antinorii from a specimen in the museum of Genoa, which had been killed by Italian explorer Orazio Antinori in what is now northern Eritrea.[10] This was subsequently regarded as a subspecies,[3] and is no longer held to be distinct.[2] In 1896, Belgian-British zoologist George Albert Boulenger combined the species (Dendroaspis polylepis) as a whole with the eastern green mamba (Dendroaspis angusticeps),[11] a lumping diagnosis that remained in force until 1946, when South African herpetologist Vivian FitzSimons split them again into separate species.[12]

The black mamba lies within the elapid genus Dendroaspis. A 2016 genetic analysis showed that the black and eastern green mambas were each others' closest relatives, and more distantly related to Jameson's mamba (Dendroaspis jamesoni).[13]

Description[edit]

The black interior of the mouth of a black mamba

The black mamba is a long, slender, cylindrical snake with a "coffin-shaped" head and a somewhat pronounced brow ridge and a medium-sized eye.[14][15] The adult snake's length typically ranges from 2 to 3 m (6 ft 7 in to 9 ft 10 in) but specimens have grown to lengths of 4.3 to 4.5 m (14.1 to 14.8 ft).[12][15] It is the second longest venomous snake species, exceeded in length only by the king cobra.[16] The black mamba is a proteroglyphous snake, with fangs up to 6.5 mm (0.26 in) in length.[17] located at the front of the maxilla.[16] The tail of the species is long and thin, making up 17–25% of its body length.[14] Black mambas weigh about 1.6 kg (3.5 lb) on average.[18]

Specimens vary considerably in colour; some may be olive, yellowish-brown, khaki or gunmetal, but are rarely black. Some individuals may a have a purplish glow to their scales. Occasionally they may display dark mottling towards the posterior, which may appear in the form of diagonal crossbands. They have greyish-white underbellies while the inside of the mouth is dark bluish-grey to nearly black. Mamba eyes are greyish brown to shades of black while the pupil is surrounded by silvery white or yellow colour. Juvenile snakes are lighter in colour than adults, typically grey or olive green in appearance, and get darker as they age.[17][12][14]

Scalation[edit]

The head, body and tail scalation of the black mamba:[15]

Distribution and habitat[edit]

Juvenile in a tree, Kruger National Park, South Africa

The black mamba has a wide range within sub-Saharan Africa. It has been observed in north east Democratic Republic of the Congo, south western Sudan to Ethiopia, Eritrea, Somalia, Kenya, eastern Uganda, Tanzania, Burundi, Rwanda, south to Mozambique, Swaziland, Malawi, Zambia, Zimbabwe and Botswana to KwaZulu-Natal in South Africa, and Namibia; then northeast across Angola to south eastern Democratic Republic of the Congo.[17][19]

The black mamba's distribution contains gaps within the Central African Republic, Chad, Nigeria and Mali. These gaps may lead physicians to misidentify black mamba bites and administer an inappropriate antivenom. In 1954 the black mamba was recorded in the Dakar region of Senegal. This observation, and a subsequent observation that identified a second specimen in the region in 1956, has not been confirmed and thus the snake's distribution in this area is inconclusive.[19]

The black mamba prefers moderately dry environments such as light woodland and scrub, rocky outcrops, and semi-arid savanna.[19] It also inhabits moist savanna and lowland forests.[15] It is not commonly found at altitudes above 1,000 metres (3,300 ft), although its distribution does include 1,800 metres (5,900 ft) in Kenya and 1,650 metres (5,410 ft) in Zambia.[19] It is rated as a species of least concern on the International Union for Conservation of Nature (IUCN)'s Red List of Endangered species, based on its huge range across sub-Saharan Africa and no documented decline.[1]

Behavior[edit]

A black mamba in defensive posture

The black mamba is both terrestrial and arboreal. It moves on the ground with its head and neck raised and typically uses termite mounds, abandoned burrows, rock crevices and tree cracks as shelter. It may share its lair with other snake species like the Egyptian cobra. Black mambas are diurnal and in South Africa, they are recorded to bask from 7–10 am and again from 2–4 pm. They may return to the same basking site daily.[15][14]

Skittish and often unpredictable, the black mamba is agile and can move quickly.[17][15] When it perceives a threat, it retreats into brush or a hole.[15] In the wild, a black mamba seldom tolerates humans approaching more closely than about 40 metres (130 ft).[15] When confronted it is likely to gape in a threat display, exposing its black mouth and flicking its tongue.[17] It also is likely to form a narrow hood by spreading its neck-flap. The threat display may be accompanied by hissing.[18][17][15]

During the threat display, any sudden movement by the intruder may provoke the mamba into a series of rapid strikes leading to severe envenomation.[15] Also, the size of the black mamba and its ability to raise its head well off the ground enable it to launch as much as 40% of its body length upwards, so mamba bites in humans may occur on the upper body.[17][15] The black mamba's reputation for being ready to attack is exaggerated. It is usually provoked by perceived threats, such as blocking its movements and ability to retreat, accidentally or otherwise.[17] The black mamba's reputed speed has also been exaggerated. It can slither at no more than 16 km/h (9.9 mph).[14]

Reproduction and lifespan[edit]

Male black mambas engaged in combat

Breeding season is from April to June,[12] during which time rival males compete by wrestling. Opponents attempt to subdue each other by intertwining their bodies and wrestling with their necks. Some observers have mistaken this for courtship.[15][14] During mating, the male will slither over the dorsal side of the female while flicking his tongue. The female will signal she is ready to mate by lifting her tail and staying still. The male will then coil around the posterior end of the female and align his tail with hers ventrolaterally. Intermission may last longer than two hours and the pair would stay motionless apart from occasional spasms from the male.[12]

The black mamba is oviparous, the female laying 6–17 eggs in a clutch.[15] The eggs are oval-shaped and enlongated, measuring 60–80 mm (2.4–3.1 in) long and 30–36 mm (1.2–1.4 in) in diameter. When hatched, the young range from 40–60 cm (16–24 in) in length. They may grow quickly, reaching 2 m (6 ft 7 in) after their first year. Like the adults, juvenile mambas can be deadly.[15][17] The black mamba is recorded to live up to 11 years, possibly longer.[18]

Feeding[edit]

The black mamba usually goes hunting from a permanent lair, to which it will regularly return if there is no disturbance. It mostly preys on birds, particularly nestlings and fledglings, and small mammals like rodents, bats, hyraxes and bushbabies. They generally prefer warm-blooded prey but will consume other snakes. The black mamba does not typically hold onto prey after biting, instead releasing its quarry and waiting for it to succumb to paralysis and die. It has a potent digestive system and has been recorded to fully digest prey between eight and ten hours.[15][17][12][14]

There are few predators of adult mambas, aside from birds of prey. Young snakes have been recorded as prey of the Cape file snake.[12] Mongooses, which have some immunity to the venom, and are often quick enough to evade a bite, will sometimes tackle a black mamba for prey.[20][21]

Venom[edit]

The black mamba is the most feared snake in Africa on account of its size, aggression, toxicity and speed of onset of symptoms.[22] [a] A survey of snakebites in South Africa from 1957 to 1963 recorded over 900 venomous snakebites, but only seven of these were confirmed black mamba bites, at a time when effective antivenom was not widely available. Out of more than 900 bites, only 21 ended in fatalities, including all seven black mamba bites.[24] The peak period for deaths is September to February during breeding season as black mambas are most irritable.[22] Bites are very rare outside Africa, with snake handlers and enthusiasts being the usual victims.[25]

Black mamba venom does not contain proteases, so there is generally no local swelling or necrosis at the bite site. Tingling of the bitten area might be the only symptom initially. The snake tends to bite repeatedly and let go, so there might be multiple puncture wounds.[22] Its bite can deliver about 100–120 mg of venom on average and the maximum dose recorded is 400 mg.[26] It is reported that before antivenom was widely available, bites were very often fatal.[27]

The venom is predominantly neurotoxic, with symptoms often becoming apparent within ten minutes.[22] Early neurological symptoms that indicate a severe course include metallic taste, ptosis and gradual bulbar palsy.[28] Other neurological symptoms include miosis, blurred or diminished vision, paresthesia, dysarthria, dysphagia, dyspnea, difficulty handling oral secretions, an absent gag reflex, fasciculations, ataxia, vertigo, drowsiness and loss of consciousness, and respiratory paralysis.[22] Other more general symptoms include nausea and vomiting, abdominal pain, diarrhoea, sweating, salivation, goosebumps, and red eyes.[27] The bite of a black mamba can cause collapse in humans within 45 minutes or less.[29] Without appropriate antivenom treatment, symptoms typically progress to respiratory failure, which leads to cardiovascular collapse and death.[22] This typically occurs in 7–15 hours.[26]

In 2015, the proteome (complete protein profile) was assessed and published, revealing 41 distinct proteins and one nucleoside.[27] The black mamba's venom is composed mainly of neurotoxins (alpha-neurotoxin and dendrotoxin), as well as other toxins such as cardiotoxins and fasciculins.[26][30] The most toxic components are the alpha-neurotoxins,[27] members of the three-finger toxin superfamily that bind nicotinic acetylcholine receptors and hence block the action of acetylcholine at the postsynaptic membrane and cause neuromuscular blockade and hence paralysis.[22][27] Dendrotoxins are akin to kunitz-type protease inhibitors that interact with voltage-dependent potassium channels, stimulating acetylcholine and causing an excitatory effect,[27] and are thought to cause the symptoms such as sweating.[22] Fasciculins are anticholinesterase inhibitors that cause muscle fasciculation.[22] The venom has little or no haemolytic, haemorrhagic or procoagulant activity.[22]

A black mamba swallowing prey

The murine median lethal dose (LD50) when administered subcutaneously has been calculated at 0.32 mg/kg,[31][32][33][34] 0.28 mg/kg.[31][23]

Reported bite cases[edit]

Danie Pienaar, now head of South African National Parks Scientific Services,[35] survived the bite of a black mamba without antivenom in 1998. Although no antivenom was administered, Pienaar was in a serious condition, despite the hospital physicians having declared it a "moderate" black mamba envenomation. At one point, Pienaar lapsed into a coma and his prognosis was declared "poor". Upon arrival at hospital Pienaar was immediately intubated, given supportive drug therapy, put on mechanical ventilation and placed on life support for three days, until the toxins were flushed out of his system. He was released from hospital on the fifth day. Pienaar believes he survived for several reasons. In an article in Kruger Park Times he said "Firstly, it was not my time to go." The article went on to state, "The fact that he stayed calm and moved slowly definitely helped. The tourniquet was also essential."[36]

Treatment[edit]

Standard first aid treatment for any suspected bite from a venomous snake is for a pressure bandage to the bite site, the victim to move as little as possible, and to be conveyed to a hospital or clinic as quickly as possible. The neurotoxic nature of the venom means that an arterial tourniquet may be of benefit due to the lethal nature of neurological symptoms.[28] Tetanus toxoid is given, though the mainstay of treatment is the administration of the appropriate antivenom.[37] There is a polyvalent antivenom produced by the South African Institute for Medical Research to treat black mamba bites from many localities,[38] and a new antivenom is being developed by the Universidad de Costa Rica's Instituto Clodomiro Picado.[39]

Pharmaceutical applications[edit]

Another member of the three-finger family, mambalgins, act as inhibitors for acid-sensing ion channels in the central and peripheral nervous system, causing a pain-inihibiting effect. This effect can be as strong as that of morphine; mambalgins do not have a resistance to naloxone, suffer less from induced tolerance, and cause no respiratory distress.[40]

Notes[edit]

  1. ^ The ocellated carpet viper is responsible for more human fatalities due to snakebite than all other African species combined.[23]

References[edit]

  1. ^ a b Spawls, Stephen (2010). "Dendroaspis polylepis". IUCN Red List of Threatened Species. 2010: e.T177584A7461853. doi:10.2305/IUCN.UK.2010-4.RLTS.T177584A7461853.en. Retrieved 28 November 2017.
  2. ^ a b c "Dendroaspis polylepis". Integrated Taxonomic Information System. Retrieved 12 December 2013.
  3. ^ a b c Uetz, Peter; Hallermann, Jakob. "Dendroaspis polylepis Günther, 1864". Reptile Database. Zoological Museum Hamburg. Retrieved 10 September 2018.
  4. ^ Mason, G.H. (1862). Zululand, a mission tour in South Afrika [Africa]. London: J.A.Nisbet. p. 183.
  5. ^ Hawes, William (1859). "On the Cape Colony, its products and resources". Journal of the Society of Arts. 7: 244–257 [252].
  6. ^ Günther, Albert (1864). "Report on a collection of reptiles and fishes made by Dr. Kirk in the Zambesi and Nyassa Regions". Proceedings of the Zoological Society of London. 1864: 303–14 [310].
  7. ^ Liddell, Henry George; Scott, Robert (1980). A Greek-English Lexicon (Abridged ed.). Oxford, United Kingdom: Oxford University Press. pp. 410, 575. ISBN 978-0-19-910207-5.
  8. ^ "Definition of mamba in English". Oxford Dictionaries. OED. Retrieved 11 January 2017.
  9. ^ Loveridge, Arthur (1951). "On reptiles and amphibians for Tanganyika Territory collected by C.J. P. Ionides". Bulletin of the Museum of Comparative Zoology at Harvard College. 106: 175–204 [201].
  10. ^ Peters, Wilhem Carl Hartwig (1873). "Über zwei Giftschlangen aus Afrika und über neue oder weniger bekannte Gattungen und Arten von Batrachiern". Monatsberichte der Königlichen Preussische Akademie des Wissenschaften zu Berlin. Jahre 1873 (1874): 411–18.
  11. ^ Boulenger, George Albert (1896). Catalogue of the snakes in the British Museum (Natural History). London, United Kingdom: Printed by order of the Trustees British Museum (Natural History). Department of Zoology. p. 437.
  12. ^ a b c d e f g Haagner, G.V.; Morgan, D.R. (1993). "The maintenance and propagation of the Black mamba Dendroaspis polylepis at the Manyeleti Reptile Centre, Eastern Transvaal". International Zoo Yearbook. 32 (1): 191–196. doi:10.1111/j.1748-1090.1993.tb03534.x.
  13. ^ 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. pp. e0161070. Bibcode:2016PLoSO..1161070F. doi:10.1371/journal.pone.0161070. ISBN 9780643106741. PMC 5014348. PMID 27603205.
  14. ^ a b c d e f g Spawls, Stephen; Howell, Kim; Drewes, Robert; Ashe, James (2017). A Field Guide to the Reptiles of East Africa (2nd ed.). Bloomsbury. pp. 1201–1202. ISBN 978-1-4729-3561-8.
  15. ^ a b c d e f g h i j k l m n o Marais, Johan (2004). A complete guide to the snakes of southern Africa (New ed.). Cape Town: Struik. pp. 95–97. ISBN 978-1-86872-932-6.
  16. ^ a b Mattison, Chris (1987). Snakes of the World. New York: Facts on File, Inc. pp. 84, 120. ISBN 978-0-8160-1082-0.
  17. ^ a b c d e f g h i j FitzSimons, Vivian F.M. (1970). A Field Guide to the Snakes of Southern Africa (Second ed.). HarperCollins. pp. 167–169. ISBN 978-0-00-212146-0.
  18. ^ a b c "Black mamba". National Geographic Society. 2010-09-10. Retrieved 2010-03-12.
  19. ^ a b c d Håkansson, Thomas; Madsen, Thomas (1983). "On the Distribution of the Black Mamba (Dendroaspis polylepis) in West Africa". Journal of Herpetology. 17 (2): 186–189. doi:10.2307/1563464. JSTOR 1563464.
  20. ^ "Watch a Mongoose Swing From a Deadly Snaked". National Geographic Society. 2017-10-03. Retrieved 7 September 2018.
  21. ^ "Mongoose Vs. Snake - Nat Geo Wild". Nat Geo Wild. Retrieved 7 September 2018.
  22. ^ a b c d e f g h i j Hodgson, Peter S.; Davidson, Terence M. (1996). "Biology and treatment of the mamba snakebite". Wilderness and Environmental Medicine. 2 (2): 133–45. PMID 11990107.
  23. ^ a b Walls, Jerry G. "The World's Deadliest Snakes". Reptiles. Retrieved 9 December 2018.
  24. ^ O'Shea, M. (2005). Venomous Snakes of the World. United Kingdom: New Holland Publishers. p. 78. ISBN 978-0-691-12436-0. ... in common with other snakes they prefer to avoid contact; ... from 1957 to 1963 ... including all seven black mamba bites - a 100 per cent fatality rate
  25. ^ Závada J.; Valenta J.; Kopecký O.; Stach Z.; Leden P. (2011). "Black Mamba Dendroaspis Polylepis Bite: A Case Report". Prague Medical Report. 112 (4): 298–304. PMID 22142525.
  26. ^ a b c Branch, Bill (1988). Field Guide to the Snakes and Other Reptiles of Southern Africa. London: New Holland. p. 95. ISBN 978-1-85368-112-7.
  27. ^ a b c d e f Laustsen, Andreas Hougaard; Lomonte, Bruno; Lohse, Brian; Fernandez, Julian; Maria Gutierrez, Jose (2015). "Unveiling the nature of black mamba (Dendroaspis polylepis) venom through venomics and antivenom immunoprofiling: Identification of key toxin targets for antivenom development". Journal of Proteomics. 119: 126–142. doi:10.1016/j.jprot.2015.02.002. PMID 25688917.
  28. ^ a b S.B. Dreyer; J.S. Dreyer (November 2013). "Snake Bite: A review of Current Literature". East and Central African Journal of Surgery. 18 (3): 45–52. ISSN 2073-9990.
  29. ^ Visser, J; Chapman, DS (1978). Snakes and Snakebite: Venomous snakes and management of snake bite in Southern Africa. Purnell. p. 52. ISBN 978-0-86843-011-9.
  30. ^ Müller, G.J.; Modler, H.; Wium, C.A.; Veale, D.J.H.; Marks, C. J. (2012). "Snake bite in southern Africa: diagnosis and management". CME. 30 (10): 362–381.
  31. ^ a b Spawls, S.; Branch, B. (1995). The dangerous snakes of Africa: natural history, species directory, venoms, and snakebite. Dubai: Oriental Press: Ralph Curtis-Books. pp. 49–51. ISBN 978-0-88359-029-4.
  32. ^ Fry, Bryan, Deputy Director, Australian Venom Research Unit, University of Melbourne (March 9, 2002). "Snakes Venom LD50 – list of the available data and sorted by route of injection ". venomdoc.com. (archived) Retrieved October 14, 2013.
  33. ^ Sherman A. Minton, (May 1, 1974) Venom diseases, Page 116
  34. ^ Philip Wexler, 2005, Encyclopedia of toxicology, Page 59
  35. ^ "Scientists gather in Kruger National Park for Savanna Science Network Meeting". South African Tourism. 5 March 2013. Retrieved 26 April 2014.
  36. ^ "Surviving a Black Mamba bite". Siyabona Africa - Kruger National Park. Siyabona Africa. Retrieved 26 April 2014.
  37. ^ Gutiérrez, José María; Calvete, Juan J.; Habib, Abdulrazaq G.; Harrison, Robert A.; Williams, David J.; Warrell, David A. (2017). "Snakebite envenoming". Nature Reviews Disease Primers. 3 (3): 17063. doi:10.1038/nrdp.2017.63. PMID 28905944.
  38. ^ Davidson, Terence. "Immediate First Aid". University of California, San Diego. Retrieved 12 May 2010.
  39. ^ Sánchez, Andrés (2017). "Expanding the neutralization scope of the EchiTAb-plus-ICP antivenom to include venoms of elapids from Southern Africa". Toxicon. 125: 59–64. doi:10.1016/j.toxicon.2016.11.259. PMID 27890775.
  40. ^ Diochot, Sylvie; Baron, Anne; Salinas, Miguel; Douguet, Dominique; Scarzello, Sabine; Dabert-Gay, Anne-Sophie; Debayle, Delphine; Friend, Valérie; Alloui, Abdelkrim (2012). "Black mamba venom peptides target acid-sensing ion channels to abolish pain". Nature. 490 (7421): 552–555. Bibcode:2012Natur.490..552D. doi:10.1038/nature11494. ISSN 0028-0836. PMID 23034652.

External links[edit]

Media related to Dendroaspis polylepis at Wikimedia Commons