Kraits

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Kraits
Yellow-banded krait (Bungarus fasciatus)

Yellow-banded krait ( Bungarus fasciatus )

Systematics
without rank: Toxicofera
Subordination : Snakes (serpentes)
Superfamily : Adder-like and viper-like (Colubroidea)
Family : Poison Snakes (Elapidae)
Subfamily : True poisonous snakes (Elapinae)
Genre : Kraits
Scientific name
Bungarus
Daudin , 1803

Kraits ( Bungarus ) are a species of snakes from the family of poisonous snakes (Elapidae) that is widespread in tropical Southeast Asia . The species have extremely potent neurotoxic venom, and a number of species are also common in human habitation. The more widespread species are therefore among the most medically relevant venomous snakes in Asia and cause numerous deaths every year.

features

anatomy

Kraits are medium-sized to large poisonous snakes, most species reach total lengths of 1.0 to 1.8 m, B. fasciatus also up to over 2.0 m. Males are significantly larger than females. The body is relatively slender and mostly approximately triangular in cross-section, it tapers towards the back. The head is narrow and barely set off from the neck. The eyes are small to medium in size and the pupil is round. The poison teeth are usually only 2-3 mm long and rigid.

Scaling

Like all venomous snakes, Kraits have nine large, symmetrical shields on the top of their head. The third supralabial does not touch the posterior nasal . The back scales are smooth. The animals have 13 to 19 dorsal rows of scales in the middle of the body. With the exception of B. lividus , the scales in the middle of the back are clearly enlarged and hexagonal in all species. The anal shield is divided, the subcaudalia are undivided or predominantly divided depending on the species.

coloring

Coloring and drawing are fairly uniform in most species; on a light, mostly whitish or slightly yellowish background there is a variable number of dark saddle spots, which have a steely sheen due to the very smooth scales.

distribution and habitat

The distribution area of ​​the genus covers large parts of tropical Southeast Asia including the Indian subcontinent and extends east to Sulawesi . The animals occur there from sea level up to 1700 m. They prefer open, moist habitats and are found mainly on the edge of fields and in low bush forests and grasslands near bodies of water.

Yellow-banded krait, neckline. The enlarged, hexagonal scales in the middle of the back are clearly visible

species

15 species are currently recognized:

Way of life

Kraits are predominantly crepuscular and nocturnal, the day is spent in earthworks or termite structures. The prey consists of small vertebrates , mostly other snakes. The animals lay eggs ( oviparous ), they lay their eggs in burrows or under piles of leaves. The clutch consists of 6-15 eggs, which are guarded by the females until the young snakes hatch.

Behavior towards people

Kraits are shy and not aggressive during the day. When threatened, they curl up, hide their heads under body loops and move the raised tail end to attract the attention of enemies. If the harassment continues, the animals will bite. Bite accidents mainly happen at dusk and at night when the kraits that are then active are accidentally stepped on. The bite often occurs while sleeping, as the animals often come into houses at night. The bite is no more painful than a sting through a thorn and is therefore often hardly noticed.

Poison

effect

All species produce a highly effective poison that is primarily nerve-damaging ( neurotoxic ). The main components are the polypeptide α-bungarotoxin , which occurs in at least 16 different shapes and enzymatically acting protein β-bungarotoxin. α-Bungarotoxin blocks the signal transmission from nerves to muscles postsynaptically and thus paralyzes the muscles. The β-bungarotoxins block presynaptic the signal transfer on the muscles and also cause so paralysis. Compared to α-bungarotoxin, β-bungarotoxins are larger and more complex molecules that take longer to reach the site of action. In severe poisoning, the result is a two-phase effect: rapid paralysis caused by α-bungarotoxin, and paralysis that occurs many hours after the bite and sometimes lasts for months, which is caused by β-bungarotoxins. Typical initial symptoms are severe abdominal cramps and paralysis of the facial muscles, which then spread to the entire skeletal and respiratory muscles.

In the Indian krait ( B. caeruleus ), 40–77% of the patients admitted to hospitals usually experience fatal respiratory arrest within 7 to 12 hours after the bite without treatment. Intensive care, especially artificial ventilation, can significantly reduce mortality. Up to a fifth of patients experience six hours to five days of unconsciousness despite ventilation. Up to 50% of surviving patients experience memory loss lasting twelve hours to eight days.

Epidemiology

Kraits are among the most medically relevant venomous snakes in Asia and cause numerous deaths every year. The relevant species differ depending on the region, most severe poisonings are caused by B. caeruleus , B. sindanus and B. walli in Pakistan, India and Nepal, B. caeruleus in Sri Lanka , B. caeruleus , B. niger and B. in Bangladesh .walli , in Thailand, Vietnam and Indonesia B. candidus and in China, Taiwan and Myanmar B. multicinctus s. l.

photos

  • B. caeruleus

  • B. fasciatus

  • Head of B. fasciatus

  • B. fasciatus

swell

Individual evidence

  1. ^ Bungarus in The Reptile Database ; accessed on March 1, 2015.
  2. ↑ Elham Abtin, Göran Nilson, Asghar Mobaraki, Ashraf Ali Hosseini, Mousa Dehgannejhad: A New Species of Krait, Bungarus (Reptilia, Elapidae, Bungarinae) and the First Record of that Genus in Iran . Russian Journal of Herpetology 21 (4), 2014, pp. 243-250 ( PDF; 1.42 MB ).
  3. ↑ K. Roemer and M. Mahyar-Roemer: Keeping, breeding and toxin of Indian Kraits, Bungarus caeruleus (Schneider, 1801). elaphe 14, issue 1, 2006: p. 32
  4. ↑ Christeine ​​A. Ariaratnam, MH Rezvi Sheriff, R. David G. Theakston and David A. Warrell: Distinctive Epidemiologic and Clinical Features of Common Krait (Bungarus caeruleus) Bites in Sri Lanka. At the. J. Trop. Med. Hyg. 79, No. 3, 2008: pp. 458-462

literature

  • MS Khan: The snakes of Pakistan. Frankfurt Contributions to Natural History, Volume 15, Edition Chimaira. Frankfurt am Main 2002, ISBN 3-930612-43-7 , pp. 133-136 and 160.
  • K. Roemer and M. Mahyar-Roemer: keeping, offspring and toxin of the Indian Kraits, Bungarus caeruleus (Schneider, 1801). elaphe 14, Issue 1, 2006, pp. 26-32.
  • RC Sharma: Fauna of India and the adjacent countries - Reptilia, Volume III (Serpentes). Kolkata, 2007, ISBN 978-81-8171-155-7 , pp. 289-297.

Web links

Commons : Kraits ( Bungarus )  - Collection of images, videos and audio files