''Bungarus'' is a genus of venomous elapid snakes, the kraits ("krait" is pronounced , rhyming with "kite"), found in

South South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...

and Southeast Asia. The genus ''Bungarus'' has 16 species.

Distribution

Kraits are found in tropical Asia, from near Iran, through the Indian subcontinent (including

Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

and Bangladesh) and on to Southeast Asia (including Indonesia and Borneo).

Description

Kraits usually range between in total length (including tail), although specimens as large as have been observed. The banded krait (''B. fasciatus'') may grow as large as . 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). Most species of kraits are covered in smooth, glossy

scale Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...

s 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

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s have round pupils. Kraits have pronounced dorsolateral flattening, which causes them to be triangular in cross section.

Diet and behavior

Kraits are ophiophagous, preying primarily upon other snakes (including venomous varieties) and are cannibalistic, feeding on other kraits. They also eat mice and small

lizards Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia althou ...

. All kraits are

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

. They are more docile during the daylight; at night, they become very active, but are not very aggressive even when provoked. They are actually rather timid, and often hide their heads within their coiled bodies for protection. When in this posture, they sometimes whip their tails around as a type of distraction.

Reproduction

Kraits are

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

. The female lays a

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

of 12 to 14 eggs in piles of leaf litter, and stays with them until they hatch.

Venom

''Bungarus'' contains some species which are among the most venomous land snakes in the world to mice based on their . They have a highly potent neurotoxic venom, which can induce muscle paralysis. Clinically, their venom contains mostly presynaptic

neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...

s. These affect the ability of neuron endings to properly release the chemical that sends the message to the next neuron. Following envenomation with

bungarotoxin Bungarotoxins are toxins found in the venom of snakes and kraits. Bites from these animals can result in severe symptoms including bleeding or hemorrhage, paralysis and tissue damage that can result in amputation. The paralytic effects of venom are ...

s, transmitter release is initially blocked (leading to a brief paralysis), followed by a period of massive overexcitation (cramps, tremors, spasms), which finally tails off to paralysis. These phases may not be seen in all parts of the body at the same time. Since kraits are nocturnal, encounters with humans are rare during daylight. Bites mainly occur during night. Bites are often initially painless, and thus may get unnoticed if the victim is sleeping. A bite from a krait is life-threatening, and should be regarded as a medical emergency. Typically, victims start to complain of severe abdominal cramps accompanied by progressive muscular paralysis, frequently starting with

ptosis Ptosis (from the Greek: πτῶσις 'falling', 'a fall', 'dropped') refers to droopiness or abnormal downward displacement of a body part or organ. Particular cases include: * Ptosis (eyelid) * Ptosis (chin) * Ptosis (breasts) * Visceroptosis, ...

. As no local symptoms are seen, a patient should be carefully observed for tell-tale signs of paralysis (e.g. the onset of bilateral ptosis, diplopia, and dysphagia), and treated urgently 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 the ineffectiveness of the antivenom. Once at a healthcare facility, support must be provided until the venom is metabolised and the victim can breathe unaided, especially if no species-specific antivenom is available. Given that the toxins alter acetylcholine transmission that 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. Cause of death is usually respiratory failure—

suffocation Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can i ...

by complete paralysis of the

diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...

. Even if patients make it to a hospital, subsequent permanent

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

and even brain death from

hypoxia Hypoxia means a lower than normal level of oxygen, and may refer to: Reduced or insufficient oxygen * Hypoxia (environmental), abnormally low oxygen content of the specific environment * Hypoxia (medical), abnormally low level of oxygen in the tis ...

may occur, given the potential for long transport times to get medical care. 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, while that of the common krait is 70–80%. 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.

Species

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

References

External links

* *
Detailed account of Joe Slowinski's death via krait bite
{{Taxonbar, from=Q752389 Reptiles of India Reptiles of Pakistan Reptiles of Sri Lanka Taxa named by François Marie Daudin