Indochinese spitting cobra

Indochinese spitting cobra
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Reptilia
Order:Squamata
Suborder:Serpentes
Family:Elapidae
Genus:Naja
Species: N. siamensis
Binomial name
Naja siamensis
Laurenti, 1768
Naja siamensis distribution

The Indochinese spitting cobra (Naja siamensis) (Thai: งูเห่า, pronounced: nguu hao) also called the Thai spitting cobra, Siamese spitting cobra or black-and-white spitting cobra, is a species of spitting cobra found in Southeast Asia.

Description

This is a medium-sized cobra with a rather thin body compared to other cobras. The body color of this species is variable from grey to brown to black, with white spots or stripes. The white patterning can be so prolific that it covers the majority of the snake. The highly distinctive black and white colour phase is common in central Thailand, specimens from western Thailand are mostly black, whereas individuals from elsewhere are usually brown. The hood mark can be spectacle-shaped, irregular or missing altogether, especially in adults.[2] Adults average 0.9 to 1.2 metres (3.0 to 3.9 ft) long,[3] and can reach a maximum of 1.6 metres (5 ft) though this is very rare.[4]

This species should not be confused with the Monocled cobra (Naja kaouthia), which has similar habitat, size and appearance.

Scalation

There are 25-31 scale rows around the hood, 19-21 just ahead of midbody; 153-174 ventral scales, 45-54 subcaudal scales, and basal pairs are sometimes undivided.[5]

Distribution and habitat

It is found in Southeast Asia, including Thailand, Cambodia, Vietnam, and Laos. May occur in eastern Myanmar but no records are known.[2] It occupies a range of habitats including lowlands, hills, plains, and woodland.[4] It can also be found in jungle habitat and it is sometimes attracted to human settlements because of the abundant populations of rodents in and around these areas.[6]

Behavior and diet

It is a primarily nocturnal species.[6] It shows variable temperament depending on the time of day it is encountered. When threatened during daylight hours, the snake is generally timid and seeks refuge in the nearest burrow. However, when the snake is threatened at night, it is more aggressive and is more likely to stand its ground, rear up and display its hood and spit out its venom.[7] If spitting venom doesn't work, it will strike and bite as a last resort. When biting, this species tends to hold on and chew savagely. It usually feeds on rodents, toads, and other snakes.[3][6]

Reproduction

The snake is oviparous. The female will lay 13-19 eggs[3] 100 days after oviposition. Eggs will hatch after 48 to 70 days depending on the temperature of incubation. Offspring are independent as soon as they have hatched. Hatchlings are 12–20 cm long and, because they possess fully developed venom delivery systems, should be treated with the same respect as adults.[7]

Venom

Like most other spitting cobras, its venom is primarily a postsynaptic neurotoxin and cytotoxin (necrotizing or tissue-death).[3] The LD50 of its venom is 1.07-1.42 mg/gram of mouse body weight.[8] Bite symptoms include pain, swelling and necrosis around the wound. The bite of this snake is potentially lethal to an adult human. Deaths, which generally happen due to paralysis and consequent asphyxiation, mainly occur in rural areas where the procurement of antivenin is difficult.

If the snake spits venom into the eyes of an individual, the individual will experience immediate and severe pain as well as temporary and sometimes even permanent blindness.[2][7]

Taxonomy

This species was long confused with the monocled cobra (Naja kaouthia) and the Chinese cobra (Naja atra), and extensive variation in pattern and scalation contributed to this confusion. Detailed morphological and molecular analyses revealed it to be a distinct species during the 1990s.[2][9]

References

  1. ↑ Stuart, B.; Thy, N.; Chan-Ard, T.; Nguyen, T.Q. & Bain, R. (2012). "Naja siamensis". The IUCN Red List of Threatened Species. IUCN. 2012: e.T177488A1488437. doi:10.2305/IUCN.UK.2012-1.RLTS.T177488A1488437.en. Retrieved 14 January 2018.
  2. 1 2 3 4 Wüster, W.; D.A. Warrell; M.J. Cox; P. Jintakune & J. Nabhitabhata (1997). "Redescription of Naja siamensis Laurenti, 1768 (Serpentes: Elapidae), a widely overlooked spitting cobra from Southeast Asia: geographic variation, medical importance and designation of a neotype" (PDF). Journal of Zoology. 243: 771–788. doi:10.1111/j.1469-7998.1997.tb01975.x.
  3. 1 2 3 4 O'Shea, Mark (2005). Venomous Snakes of the World. United Kingdom: New Holland Publishers (UK) Ltd. p. 94. ISBN 0-691-12436-1.
  4. 1 2 "Naja siamensis - General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms". WCH Clinical Toxinology Resource. University of Adelaide. Retrieved 14 January 2012.
  5. ↑ "Naja siamensis - Indochinese spitting cobra". Asiatic Naja. Bangor University. Retrieved 5 November 2013.
  6. 1 2 3 "Naja siamensis". Armed Forces Pest Management Board. United States Department of Defense. Archived from the original on 11 January 2012. Retrieved 14 January 2012.
  7. 1 2 3 O'Shea, Halliday; Mark, Tim (2002). Reptiles and Amphibians. California, USA: Topeka Bindery. ISBN 0-613-53093-4.
  8. ↑ Chanhome, L., Cox, M. J., Vasaruchaponga, T., Chaiyabutra, N. Sitprija, V. (2011). Characterization of venomous snakes of Thailand. Asian Biomedicine 5 (3): 311–328.
  9. ↑ Wüster, W.; R.S. Thorpe; M.J. Cox; P. Jintakune & J. Nabhitabhata (1995). "Population systematics of the snake genus Naja (Reptilia: Serpentes: Elapidae) in Indochina: multivariate morphometrics and comparative mitochondrial DNA sequencing (cytochrome oxidase I)" (PDF). Journal of Evolutionary Biology. 8: 493–510. doi:10.1046/j.1420-9101.1995.8040493.x.
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