Biology:Bungarus

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Short description: Genus of venomous snakes

Bungarus
Davidraju IMG 7334.jpg
Bungarus fasciatus (banded krait), the largest species of krait
Scientific classification e
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Bungarus
Daudin, 1803
Type species
Bungarus annularis
Daudin, 1803[1]
Synonyms[1]
  • Pseudoboa Oppel, 1811
  • Aspidoclonion Wagler, 1828
  • Megærophis Gray, 1849
  • Xenurelaps Günther, 1864

Bungarus (commonly known as kraits /krt/)[2][3] is a genus of elapids native to Asia. Often found on the floor of tropical forests in South Asia, Southeast Asia and Southern China, they are medium-sized, highly venomous snakes with a length typically not exceeding 2 metres (6 ft 7 in). These are nocturnal ophiophagious predators which prey primarily on other snakes at night, occasionally taking lizards, amphibians and rodents. Most species are with banded patterns acting as a warning sign to their predators. Despite being considered as generally docile and timid, kraits are capable of delivering highly potent neurotoxic venom which is medically significant with potential lethality to humans. The genus currently holds 16 species and 5 subspecies.

Distribution

Kraits are found in tropical and subtropical South and Southeast Asia and Indochina, ranging in the west from Iran, east through the Indian subcontinent (including Bangladesh, Nepal, Pakistan , & Sri Lanka) and into Southeast Asia (including the island of Borneo, Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Papua New Guinea, the Philippines , Thailand and Vietnam).[4]

Description

Kraits usually range between 1.0 and 1.5 m (3 ft 3 in and 4 ft 11 in) in total length (including tail), although specimens as large as 2.0 m (6 ft 7 in) have been observed. The banded krait (B. fasciatus) may grow as large as 2.125 m (6 ft 11.7 in).[5] Most species of kraits are covered in smooth, glossy scales arranged in bold, striped patterns of alternating black and light-colored areas. This may serve as aposematic colouration in its habitat of grassland and scrub jungle. The scales along the dorsal ridge of the back are hexagonal. The head is slender, and the eyes have round pupils. Kraits have pronounced dorsolateral flattening, which causes them to be triangular in cross section.

Ecology

Kraits are nocturnal and ophiophagous, preying chiefly upon other snakes including those of their kinds, although occasional hunt for small rodents and lizards has been observed.[6] They are seldom encountered during daytime while becoming highly alert at night. If disturbed, fleeing is usually their first choice; if failed, they tend to coil up with the head underneath the body for protection. In spite of being generally docile and timid, some species are known to thrash fiercely when caught for relocation. Repeated provocation may result in bites which are the last resort of the snakes.[7] Kraits are oviparous, releasing a clutch of 12 to 14 eggs in piles of leaf litter. The female usually stays with them until they hatch.

Venom

Bungarus contains some species that are among the most venomous land snakes in the world, to mice, based on their -1">50.[8][verification needed] They have a highly potent, neurotoxic venom, which can induce muscle paralysis. Clinically, their venom contains mostly presynaptic neurotoxins, which affect the ability of neuron endings to properly release a chemical communication mechanism to the next neuron. Following envenomation with bungarotoxins, transmitter release is initially blocked (leading to a brief paralysis), followed by a period of massive overexcitation (cramps, tremors, spasms), which finally tapers off to paralysis.

These phases of envenomation may or may not be experienced in all parts of the body; they may or may not be experienced simultaneously. The severity of the bite itself and the actual dosage of venom delivered plays a role in the intensity of symptoms. As kraits are mainly nocturnal, encounters with humans are rare during the daytime. Bites mainly occur after sunset, and are often (initially) painless; thus, a bite may go unnoticed if the victim is sleeping or otherwise does not see or notice the krait, further prolonging envenomation damage within the body. Still—whenever possible—medical treatment should be sought posthaste, as a bite from a krait is considered potentially life-threatening. All venomous snake bites must be taken seriously as an immediate medical emergency.

Typically, victims will start to notice severe abdominal cramps accompanied by progressive muscular paralysis, and frequently starting with ptosis. As no local symptoms are usually seen, a patient should be carefully observed for tell-tale signs of paralysis (e.g. the onset of bilateral ptosis, diplopia, and dysphagia), and subsequently treated (as quickly as possible) with antivenom. Frequently, little or no pain occurs at the site of a krait bite, which can provide false reassurance to the victim. The major medical difficulty of envenomated patients is the lack of medical resources (especially intubation supplies and mechanical ventilators in rural hospitals) and potential for ineffectiveness by the antivenom.

Upon arriving at a healthcare facility, support must be provided until the venom has metabolised and the victim can breathe unaided, especially if no species-specific antivenom is available. Given that the toxins alter acetylcholine transmission—which causes the paralysis—some patients have been successfully treated with cholinesterase inhibitors, such as physostigmine or neostigmine, but success is variable and may be species-dependent, as well. If death occurs, it typically takes place about 6-12 hours after the krait bite, but can be significantly delayed. The usual cause of death in that situation is respiratory failure—suffocation by complete paralysis of the diaphragm. Even if patients make it to a hospital, subsequently entering a permanent coma (and even brain death from hypoxia) may occur, given the potential for long transport times to get medical care, in some regions.

Mortality rates caused by bites from the members of this genus vary by species; according to University of Adelaide Department of Toxicology, bites from the banded krait have a mortality rate of 1–10% in untreated humans,[9] while that of the common krait is 70–80%.[10] In common with those of all other venomous snakes, the death time and fatality rate resulting from bites of kraits depend on numerous factors, such as the venom yield and the health status of the victim.

Polyvalent elapid antivenom is effective in neutralizing of the venoms of B. candidus and B. flaviceps, and rather effective for B. fasciatus, and the monovalent B. fasciatus antivenom is also moderately effective.[11]

Species

Image Species Authority Subsp.* Common name Geographic range
Andaman Krait.jpg Bungarus andamanensis Biswas & Sanyal, 1978 0 South Andaman krait India (Andaman Island)
Bungarus bungaroides.jpg Bungarus bungaroides (Cantor, 1839) 0 Northeastern hill krait Myanmar, India (Assam, Cachar, Sikkim), Nepal, Vietnam
Coomon Krait.jpg Bungarus caeruleusT (Schneider, 1801) 0 Common krait, Indian krait Afghanistan, Pakistan , India (Bengal, Maharashtra, Karnataka), Sri Lanka, Bangladesh, Nepal
Bungar candi 120608-0343 krw.jpg Bungarus candidus (Linnaeus, 1758) 0 Blue krait, Malayan krait Cambodia, Indonesia (Java, Sumatra, Bali, Sulawesi), Malaysia (Malaya), Singapore, Thailand, Vietnam
The Ceylon krait or Sri Lankan krait (Bungarus ceylonicus) is a species of venomous snake endemic to the island Sri Lanka.jpg Bungarus ceylonicus Günther, 1864 1 Ceylon krait, Sri Lankan krait Sri Lanka
Banded Krait, Bungarus fasciatus (24025894235).jpg Bungarus fasciatus (Schneider, 1801) 0 Banded krait Bangladesh, Brunei, Myanmar, Cambodia, south China (incl. Hong Kong, Hainan), north-east India , Bhutan, Nepal, Indonesia (Sumatra, Java, Borneo), Laos, Macau; Malaysia (Malaya and East Malaysia), Singapore, Thailand and Vietnam.
Red-headed Krait.jpg Bungarus flaviceps (Reinhardt, 1843) 1 Red-headed krait South Thailand, South Myanmar, Cambodia, Vietnam, Malaysian Peninsula, Pulau Tioman, Indonesia (Bangka, Sumatra, Java, Billiton, Borneo)
Bungarus lividus, Lesser Black Krait at Jalpaiguri, India.jpg Bungarus lividus Cantor, 1839 0 Lesser black krait India , Bangladesh, Nepal
Bungarus multicinctus 125204318.jpg Bungarus magnimaculatus Wall & Evans, 1901 0 Burmese krait Myanmar
Bungarus multicinctus Blyth, 1861 1 Many-banded krait Taiwan, south China (Hong Kong, Hainan), Myanmar, Laos, northern Vietnam, and Thailand
Bungarus niger 83013559.jpg Bungarus niger Wall, 1908 0 Black krait, Greater black krait India (Assam, Sikkim), Nepal, Bangladesh, Bhutan
Bungarus persicus Abtin, Nilson, Mobaraki, Hosseini & Dehgannejhad, 2014 0 Persian krait, Iranian krait Iran
Sind Krait.jpg Bungarus sindanus Boulenger, 1897 2 Sind krait Southeast Pakistan, India
Bungarus slowinskii[12] Kuch, Kizirian, Q. Nguyen, Lawson, Donnelly & Mebs, 2005 0 Red River krait Northern Vietnam, Thailand, Laos, Cambodia.
Paratype of Bungarus suzhenae in life - Oo 521379.jpg Bungarus suzhenae Chen, Shi, S. C., Vogel, Ding, & Shi, 2021 0 Suzhen's krait China (Yunnan), Myanmar (Kachin State)
Bungarus Walli Wall by Ganesh Sah.jpg Bungarus walli Wall, 1907 0 Wall's krait India (Uttar Pradesh), Nepal, Bangladesh

*) Not including the nominate subspecies (typical form).
T) Type species

See also

References

  1. 1.0 1.1 "Bungarus". RepFocus - A Survey of the Reptiles of the World. Rune Midtgaard. http://www.repfocus.dk/Bungarus.html. 
  2. "krait, n." Oxford English Dictionary Online. Oxford University Press (accessed June 30, 2014).
  3. "krait". American Heritage Dictionary. Accessed June 30, 2014.
  4. SurvivalIQ: Krait
  5. Smith, Malcolm A. (1943). The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region. Reptilia and Amphibia. Vol. III.—Serpentes. London: Secretary of State for India. (Taylor and Francis, printers). xii + 583 pp. (Bungarus, genus and species, pp. 407-418).
  6. Richard Mastenbroek's Elapid Pages: Kraits (Bungarus ssp.)
  7. "Living in Indonesia:Banded Krait". http://www.expat.or.id/medical/poisonoussnakes.html#. 
  8. Whitaker, Romulus; Captain, Ashok (2004). Snakes of India, The Field Guide. Chennai: Draco Books.. p. 495. ISBN 81-901873-0-9. 
  9. "Bungarus fasciatus ". WCH Clinical Toxinology Resources. http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0018. 
  10. "Bungarus caeruleus ". WCH Clinical Toxinology Resources. http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0015. 
  11. Nget Hong Tan. "Antivenoms against Malaysian poisonous snakes". University of Malaya. http://www.tanngethong.com/Antivenom.htm. 
  12. Kuch, Ulrich; Kizirian, David; Nguyen, Quang Truong; Lawson, Robin; Donnelly, Maureen A.; Mebs, Dietrich (2005). "A new species of krait (Squamata: Elapidae) from the Red River System of Northern Vietnam". Copeia 2005 (4): 818-833. (Bungarus slowinskii, new species).

Further reading

  • Boulenger GA (1896). Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the Colubridæ (Opisthoglyphæ and Proteroglyphæ) ... London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiv + 727 pp. + Plates I-XXV. (Genus Bungarus, pp. 365-366, Figure 26, three views of skull).
  • Daudin FM (1803). Histoire Naturelle, Génerale et Particulière des Reptiles; Ouvrage faisant suite aux Œuvres de Leclerc de Buffon, et partie de Cours complete d'Histoire naturelle rédigé par C.S. Sonnini, membre de plusieurs Sociétés savantes. Tome cinquième [Volume 5]. Paris: F. Dufart. 365 pp. (Bungarus, new genus, p. 263). (in French).

External links

Wikidata ☰ Q752389 entry