Monocled cobra

Monocled cobra
Monocled cobra
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Naja
Species: N. kaouthia
Binomial name
Naja kaouthia
Lesson, 1831
Naja kaouthia distribution

The monocled cobra (Naja kaouthia), also called monocellate cobra, is a cobra species, which is widespread across South and South East Asia and listed as Least Concern by IUCN.[1]

Taxonomic history

In 1831, René Lesson first described the monocled cobra as a beautiful snake that is well distinct from the spectacled cobra, with 188 ventral scales and 53 pairs of caudal scales.[2]

Since then, several monocled cobras were described under different scientific names:

Several varieties of monocled cobras were described under the binomial Naja tripudians between 1895 and 1913.

In 1940, Malcolm Arthur Smith classified the monocled cobra as a subspecies of the spectacled cobra under the trinomial Naja naja kaouthia.[5]

Characteristics

A young monocled cobra

The monocled cobra has an O-shaped, or monocellate hood pattern, unlike that of the Indian cobra which has the "spectacle" pattern (2 circular ocelli connected by a curved line) on the rear of its hood. Coloration in the young is more constant. The dorsal surface may be yellow, brown, gray, or blackish, with or without ragged or clearly defined cross bands. It can be olivaceous or brownish to black above with or without a yellow or orange-colored, O-shaped mark on the hood. It has a black spot on the lower surface of the hood on either side, and one or two black cross-bars on the belly behind it. The rest of the belly is usually of the same color as the back, but paler. As age advances, the snake becomes paler, wherein the adult is brownish or olivaceous. The elongated nuchal ribs enable a cobra to expand the anterior of the neck into a “hood”. A pair of fixed anterior fangs is present. The largest fang recorded measured 6.78 mm (0.678 cm). Fangs are moderately adapted for spitting.[6] Adult monocled cobras reach a length of 1.35 to 1.5 m (4.4 to 4.9 ft) with a tail length of 23 cm (9.1 in). Many larger specimens have been recorded, but they are rare. Adults can reach a maximum of 2.3 m (7.5 ft) in length.[7][8]

Scalation

They have 25 to 31 scales on the neck, 19 to 21, usually 21, on the body, and 17 or 15 on the front of the vent. They have 164 to 197 ventral scales and 43 to 58 subcaudal scales.[7]

Monocled cobras tend to have more than one cuneate scale on each side. The shape of the frontal scale is short and square. Ventrals in males range from 170 to 192, in females from 178 to 197. Subcaudals in males range from 48 to 61, in females from 46 to 59.[6]

Distribution and habitat

Monocled cobras are distributed from India in the west through to China, Vietnam and Cambodia. They are also found on the Malay Peninsula and are native to Bangladesh, Bhutan, Myanmar, Laos, Nepal, and Thailand.

These cobras can adapt to a range of habitats, from natural to anthropogenically impacted environments. They prefer habitats associated with water, such as paddy fields, swamps, and mangroves, but can also be found in grasslands, shrublands, and forests. The species also occurs in agricultural land and human settlements, including cities. They can be found at elevations of up to 1,000 m (3,300 ft) above sea level.[1]

Ecology and behaviour

Monocled cobras are terrestrial and most active at dusk and in the evening. In rice-growing areas, they hide in rodent burrows in the dykes between fields and have become semi-aquatic in this type of habitat. Juveniles feed mostly on amphibians, and adults prey on small mammals, snakes and fish. When disturbed they prefer to take flight.[6] However, when threatened, they will raise the anterior portions of their bodies, spread their hood, usually hiss loudly, and strike in an attempt to bite and defend themselves.[8]

They are often found in tree holes and areas where rodents are plentiful.[9]

Reproduction

This is an oviparous species. Females lay between 16 and 33 eggs per clutch. Incubation periods range from 55 to 73 days.[10] Egg-laying takes place in January to March. The females usually stay with the eggs. Some collaboration between males and females has been reported in Naja naja x Naja kaouthia - hybrids.[6]

Conservation status

This species has been assessed as Least Concern by IUCN owing to its large distribution, tolerance of a broad range of habitats, including anthropogenically altered environments, and its reported abundance. No major threats have been reported, and the species is not thought to be undergoing a significant population decline. In places the distribution of this species coincides with protected areas, probably providing small safeguards. Monocled cobras are harvested for the skin trade, however, collection from the wild is minimal and not likely to be causing significant population declines.[1] Naja kaouthia is listed on CITES Appendix II.[11]

Venom

Monocled cobras at Snake Farm in Bangkok

The Naja kaouthia venom sources from three different localities were reported to exhibit different intravenous and subcutaneous median lethal dose: Thailand, 0.18-0.22 µg/g; Malaysia, 0.90-1.11 µg/g; and Vietnam, 0.90-1.00 µg/g, of mouse body weight.[12] The proteomics finding revealed that the neurotoxin profiles of these Naja kaouthia were substantially different, reflecting the distinct difference in their lethal potency and response to antivenom neutralization.

The major toxic components in cobra venoms are postsynaptic neurotoxins, which block the nerve transmission by binding specifically to the nicotinic acetylcholine receptor, leading to flaccid paralysis and even death by respiratory failure. The major α-neurotoxin in Naja kaouthia venom is a long neurotoxin, α-cobratoxin; the minor α-neurotoxin is different from cobrotoxin in one residue.[13] The neurotoxins of this particular species are weak.[14] The venom of this species also contains myotoxins and cardiotoxins.[15][16]

In case of intravenous injection the LD50 tested in mice is 0.373 mg/kg, and 0.225 mg/kg in case of intraperitoneal injection.[17] The average venom yield per bite is approximately 263 mg (dry weight).[18]

The monocled cobra causes the highest fatality due to snake venom poisoning in Thailand.[19] Envenomation usually presents predominantly with extensive local necrosis and systemic manifestations to a lesser degree. Drowsiness, neurological and neuromuscular symptoms will usually manifest earliest; hypotension, flushing of the face, warm skin, and pain around bite site typically manifest within one to four hours following the bite; paralysis, ventilatory failure or death could ensue rapidly, possibly as early as 60 minutes in very severe cases of envenomation. However, the presence of fang marks does not always imply that envenomation actually occurred.[20]

Extract of Mimosa pudica plant has been shown, in a preliminary study, to possibly have neutralizing effects on the toxins present in this venom.[21]

See also

References

  1. 1 2 3 4 Stuart, B. & Wogan, G. (2012). "Naja kaouthia". IUCN Red List of Threatened Species. Version 2016.2. International Union for Conservation of Nature.
  2. ↑ Lesson, R.-P. (1831). Catalogue des Reptiles qui font partie d’une Collection zoologique recueillie dans l’Inde continental ou en Afrique, et apportée en France par M. Lamare-Piqout. Catalogue dressé (juillet 1831). 25. Le Naja Kaouthia, Naja kaouthia, Less.. Bulletin des Sciences Naturelles et de Géologie, Tome XXV: 122.
  3. ↑ Gray, J. E. (ed.) (1834). Cobra Capella. Illustrations of Indian zoology chiefly selected from the collection of Maj.-Gen. Hardwicke. Vol. II: Plate 78.
  4. ↑ Cantor, T. (1839) Naja larvata. Proceedings of the Zoological Society of London. Vol. VII: 32–33.
  5. ↑ Smith, M. A. (1940). Naja naja kaouthia. Records of the Indian Museum. Volume XLII: 485.
  6. 1 2 3 4 Wüster, W (1998). "The cobras of the genus Naja in India" (PDF). Hamadryad. 23 (1): 15–32.
  7. 1 2 Smith, M. A. (1943) Naja naja kaouthia In: The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-Region. Reptilia and Amphibia. Volume III (Serpentes). Taylor and Francis, London. Pages 428–432.
  8. 1 2 Chanhome, L.; Cox, M. J.; Vasaruchaponga, T.; Chaiyabutra, N. Sitprija (2011). "Characterization of venomous snakes of Thailand". Asian Biomedicine. 5 (3): 311–328.
  9. ↑ "Naja kaouthia: General Details and Information". WCH Clinical Toxinology Resource. University of Adelaide. Retrieved 3 February 2012.
  10. ↑ Chanhome, L; Jintkune, P.; Wilde, H.; Cox, M. J. (2001). "Venomous snake husbandry in Thailand" (PDF). Wilderness and Environmental Medicine. 12: 17–23. doi:10.1580/1080-6032(2001)012[0017:vshit]2.0.co;2.
  11. ↑ "Status of Naja kaouthia". CITES species database. CITES. Retrieved 3 February 2012.
  12. ↑ Tan, K. Y.; Tan, C. H.; Fung, S. Y.; Tan, N. H. (2015). "Venomics, lethality and neutralization of Naja kaouthia (monocled cobra) venoms from three different geographical regions of Southeast Asia". Journal of proteomics. 120: 105–125. doi:10.1016/j.jprot.2015.02.012.
  13. ↑ Wei, J.-F.; Lü, Q.-M.; Jin, Y.; Li, D.-S.; Xiong, Y.-L.; Wang, W.-Y. (2003). "α-Neurotoxins of Naja atra and Naja kaouthia Snakes in Different Regions". Acta Biochimica et Biophysica Sinica. 35 (8): 683–688.
  14. ↑ Ogay, A.; Rzhevskya, D. I.; Murasheva, A. N.; Tsetlinb, V. I.; Utkin, Y. N. (2005). "Weak neurotoxin from Naja kaouthia cobra venom affects haemodynamic regulation by acting on acetylcholine receptors". Toxicon. 45 (1): 93–99. doi:10.1016/j.toxicon.2004.09.014. PMID 15581687. Retrieved 25 December 2011.
  15. ↑ Mahanta, M.; Mukherjee, A. K. (2001). "Neutralisation of lethality, myotoxicity and toxic enzymes of Naja kaouthia venom by Mimosa pudica root extracts". Journal of Ethnopharmacology. 75 (1): 55–60. doi:10.1016/S03788741(00)003731. Retrieved 25 December 2011.
  16. ↑ Fletcher, J. E.; Jiang, M.-S.; Gong, Q.-H.; Yudkowsky, M. L.; Wieland, S. J. (1991). "Effects of a cardiotoxin from Naja naja kaouthia venom on skeletal muscle: Involvement of calcium-induced calcium release, sodium ion currents and phospholipases A2 and C". Toxicon. 29 (12): 1489–1500. doi:10.1016/0041-0101(91)90005-C. PMID 1666202. Retrieved 25 December 2011.
  17. ↑ Fry, Dr. Bryan Grieg. "LD50 Menu". Australian Venom Research Unit. University of Queensland. Retrieved 25 December 2011.
  18. ↑ Engelmann, W.-E. (1981). Snakes: Biology, Behavior, and Relationship to Man. Leipzig; English version NY, USA: Leipzig Publishing; English version published by Exeter Books (1982). p. 51. ISBN 0-89673-110-3.
  19. ↑ Pratanaphon, R.; Akesowan, S.; Khow, O.; Sriprapat, S.; Ratanabanangkoon, K. (1997). "Production of highly potent horse antivenom against the Thai cobra (Naja kaouthia)". Vaccine. 15 (14): 1523–1528. doi:10.1016/S0264-410X(97)00098-4. PMID 9330463. Retrieved 25 December 2011.
  20. ↑ Davidson, T. "Snakebite Protocols: Summary for Human Bite by Monocellate Cobra (Naja naja kaouthia)".
  21. ↑ "Neutralisation of lethality, myotoxicity and toxic enzymes of Naja kaouthia venom by Mimosa pudica root extracts". Journal of Ethnopharmacology. 75: 55–60. Apr 2001. doi:10.1016/S0378-8741(00)00373-1. PMID 11282444.

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