Species of Thailand
Malayan pit viper
Calloselasma rhodostoma, Heinrich Kuhl, 1824
(In Thai: งูกะปะ, ngu ga pha)
Calloselasma is a monotypic genus created for a venomous pit viper species, C. rhodostoma, which is endemic to Southeast Asia from Thailand to northern Malaysia and on the island of Java. No subspecies are currently recognized.
Attains an average total length of 76 cm, with females being slightly longer than males. Occasionally, they may grow as long as 91 cm.
A specimen with a total length of 81 cm has a tail 9 cm long.
Dorsally it is reddish, grayish, or pale brown, with two series of large, dark brown, black-edged triangular blotches, which are alternating or opposite. There is also a thin dark brown vertebral stripe, which may be interrupted or indistinct in some specimens. The upper labials are pink or yellowish, and powdered with brown. There is a broad, dark brown, black-edged diagonal stripe from the eye to the corner of the mouth, with a narrower light-colored stripe above it. Ventrally it is yellowish, uniform or powdered or spotted with grayish brown.
The smooth dorsal scales are arranged in 21 rows at midbody. Ventrals 138-157; anal plate entire; subcaudals 34-54 pairs.
Snout pointed and upturned. Rostral as deep as broad. Two internasals and two prefrontals. Frontal as long as or slightly longer than its distance from tip of snout, as long as or slightly shorter than the parietals. 7-9 upper labials. Loreal pit not in contact with the upper labials.
This is the only Asian pit viper with large crown scales and smooth dorsal scales.
Found in Nepal, Thailand, Cambodia, Laos, Vietnam, northern West Malaysia and on the Indonesian island of Java. The type locality is listed as "Java". There are unconfirmed, but credible reports from southern Myanmar (Burma), northern Sumatra and northern Borneo.
Habitat and diet
Prefers coastal forests, bamboo thickets, unused and overgrown farmland, orchards, plantations as well as forests around plantations, where it searches for rats and mice.
This species is oviparous and the eggs are guarded by the female after deposition.
This species has a reputation for being bad-tempered and quick to strike. In northern Malaysia it is responsible for some 700 incidents of snakebite annually with a mortality rate of about 2 percent. Remarkably sedentary, it has often been found in the same spot several hours after an incident involving humans. Its venom causes severe pain and local swelling and sometimes tissue necrosis, but deaths are not common. Many victims are left with dysfunctional or amputated limbs due to the lack of antivenom and early treatment. In a 2005 study of 225 Malayan pit viper (Calloselasma rhodostoma) bites in Thailand, most victims had mild to moderate symptoms, but 27 of 145 patients (18.6%) developed permanently swollen limbs. There were only two deaths (related to intracerebral hemorrhage) and no amputations. The antivenin manufactured in Thailand seemed effective in reversing the blood clotting caused by the venom. Most patients remained stable and did not require antivenin. The authors suggested that victims not use traditional healers and avoid overuse of tourniquets. In a prospective phase of the study, bites occurred throughout the year but mostly early in the monsoon season (May and June).
Venom and thrombosis treatment
The venom of this species is used to isolate a thrombin-like enzyme called ancrod. This enzyme is used clinically to break down and dissolve thrombi (blood clots) in patients and lower blood viscosity to help prevent heart attack and stroke.
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- Calloselasma rhodostoma
- German: Malaiische Mokassin-Grubenotter
- Malayan pit viper
- Malayan grond pit viper
- Malayan ground snake
- Malayan moccasin
- Thai: งูกะปะ, ngu ga pha
Calloselasma rhodostoma annamensis, Fernand Angel, 1933
Range: Southeast Cambodia and Vietnam
Calloselasma rhodostoma rhodostoma, Friedrich Boie, 1827
Range: South Vietnam (Binh Thuan etc.), Cambodia, Thailand, Laos, West Malaysia and Indonesia (Java).
- Calloselasma rhodostoma, Van Stanley Bartholomew Wallach et al. (2014)
- Calloselasma rhodostoma, Nguyen Van Sang et al. (2009)
- Calloselasma rhodostoma, Roy W. McDiarmid, Jonathan A. Campbell & T'Shaka A. Touré (1999)
- Calloselasma rhodostoma, Merel J. Cox et al. (1998)
- Calloselasma rhodostoma, Ulrich Manthey & Wolfgang Grossmann (1997)
- Calloselasma rhodostoma, Kenneth Welsh (1994)
- Calloselasma rhodostoma, Simon M Campden-Main (1970)
- Ancistrodon rhodostoma, Malcolm Arthur Smith (1943)
- Agkistrodon annamensis, René Léon Bourret (1936)
- [Agkistrodon] annamensis, Clifford H. Pope (1935)
- Agkistrodon rhodostoma, Sworder (1933)
- Ancistrodon annamensis, F. Angel (1933)
- Agkistrodon rhodostoma, Doris Mable Cochran (1930)
- Ancistrodon (Calloselasma) rhodostoma, René Léon Bourret (1927)
- Agkistrodon rhodostoma, Nelly de Rooij (1917)
- Agkistrodon rhodostoma, Thomas Barbour (1912)
- Ancistrodon rhodostoma, George Albert Boulenger (1896)
- Ancistrodon rhodostoma, Oskar Boettger (1892)
- Calloselma rhodostoma, Jean-Claude Albert Morice (1875)
- Calloselasma rhodostoma, Albert Charles Lewis Günther (1864)
- Trigonocephalus (Tisiphone) rhodostoma, Giorgio Jan (1863)
- Tisiphone rhodostoma, Wilhelm Karl Hartwich Peters (1862)
- Calloselasma, Edward Drinker Cope (1860)
- Calloselasma rhodostomus, Edward Drinker Cope (1860)
- Leiolepis rhodostoma, André Marie Constant Duméril & Gabriel Bibron (1854)
- Ancistrodon, Spencer Fullerton Baird (1854)
- L[eiolepis] rhodostoma, André Marie Constant Duméril (1853)
- Leiolepis, André Marie Constant Duméril (1853)
- Tisiphone rhodostoma, Leopold Fitzinger (1843)
- Tisiphone, Leopold Fitzinger (1843)
- Trigonocephalus praetextatus, Johann Ludwig Christian Gravenhorst (1832)
- [Trigonocephalus] praetextatus, Johann Ludwig Christian Gravenhorst (1832)
- Trigonocephalus rhodostoma, Friedrich Boie (1827)
- Trigonocephalus rhodostoma, Heinrich Kuhl (1824)
- Trigonocephalus, Heinrich Kuhl (1822)
- Agkistrodon, Palisot de Beauvois (1799)
Least Concern (IUCN3.1)