Echis

Echis
Echis carinatus in Mangaon, (Maharashtra, India)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Subfamily: Viperinae
Genus: Echis
Merrem, 1820
Synonyms
  • Echis Merrem, 1820
  • Toxicoa Gray, 1849
  • Turanechis Cherlin, 1990[1]

Echis (сommon names: saw-scaled vipers, carpet vipers[2]) is a genus of venomous vipers found in the dry regions of Africa, the Middle East, Pakistan, India, and Sri Lanka. They have a characteristic threat display, rubbing sections of their body together to produce a "sizzling" warning sound.[3] The name Echis is a Greek word for "viper." Their common name is "saw-scaled vipers" and they include some of the species responsible for causing the most snakebite cases and deaths in the world.[4] Eight species are currently recognized.[5]

Description

Closeup: scales with serrated keels

Saw-scaled vipers are relatively small snakes, the largest species (E. leucogaster, E. pyramidum) staying slightly below 90 cm (35 in) in total length (body + tail), and the smallest (E. hughesi, E. jogeri) being around 30 cm (12 in) in total length.

The head is relatively small and is short, wide, pear-shaped and distinct from the neck. The snout is short and rounded, while the eyes are relatively large and the body is moderately slender and cylindrical. The dorsal scales are mostly keeled. However, the scales on the lower flanks stick out at a distinct 45° angle and have a central ridge, or keel, that is serrated (hence the common name). The tail is short and the subcaudals are single.[3]

A saw scaled viper of the genus Echis may be responsible for biblical claims of a fiery flying serpent.[6]

Geographic range

Species of this genus are found in Pakistan, India (in rocky regions of Maharashtra, Rajasthan, Uttar Pradesh, and Punjab) and Sri Lanka, parts of the Middle East, and Africa north of the equator.[1]

Behaviour

All members of this genus have a distinctive threat display, which involves forming a series of parallel, C-shaped coils and rubbing them together to produce a sizzling sound, rather like water on a hot plate.[2][3] The proper term for this is stridulation.[7] As they become more agitated, this stridulating behavior becomes faster and louder. This display is thought to have evolved as a means of limiting water loss, such as might occur when hissing.[3] However, some authors describe this display as being accompanied by loud hissing.[7]

These snakes can be fierce and will strike from the position described above. When doing so, they may overbalance and end up moving towards their aggressor (an unusual behavior for snakes).[2]

Diet

Little is known about the diets of some Echis species. For others, their diets are reported to be extremely varied, and may include items such as locusts, beetles, worms, slugs, spiders, scorpions, centipedes, solifugids, frogs, toads, reptiles (including other snakes), small mammals, and birds.[2][3]

Reproduction

Most Echis species, such as those found in Africa, are oviparous, while others, such as those in India, are viviparous.[2][3]

Venom

The venom of Echis species consists mostly of hemotoxin. The genus is recognized as medically significant in many tropical rural areas. They are widespread and live in areas lacking modern medical facilities. Most victims are bitten after dark when these snakes are active.<ref name="Mal03

Most of these species have venom that contains factors that can cause a consumption coagulopathy and defibrination, which may persist for days to weeks. This may result in bleeding anywhere in the body, including the possibility of an intracranial hemorrhage. The latter classically occurs a few days following the bite.[8]

Venom toxicity varies among the different species, geographic locations, individual specimens, sexes, over the seasons, different milkings, and, of course, the method of injection (subcutaneous, intramuscular, or intravenous). Consequently, the LD50 values for Echis venoms differ significantly. In mice, the intravenous LD50 ranges from 2.3 mg/kg (U.S. Navy, 1991) to 24.1 mg/kg (Christensen, 1955) to 0.44-0.48 mg/kg (Cloudsley-Thompson, 1988). In humans, the lethal dose is estimated to be 3–5 mg (Minton, 1967). Venom from females was more than twice as toxic on average than venom from males.[3]

The amount of venom produced also varies. Reported yields include 20–35 mg of dried venom from specimens 41–56 cm in length,[9] 6–48 mg (16 mg average) from Iranian specimens[10] and 13–35 mg of dried venom from animals from various other localities.[11] Yield varies seasonally, as well as between the sexes: the most venom is produced during the summer months and males produce more than females.[3]

Species

Species[1] Taxon author[1] Subsp.*[5] Common name Geographic range[1]
E. carinatusT (Schneider, 1801) 4 Saw-scaled viper Southeastern Arabian Peninsula (Oman, Masirah and eastern UAE), southwestern Iran, Afghanistan, Uzbekistan, Turkmenistan, Tajikistan, Pakistan (including Urak near Quetta and Astola Island off the Makran Coast), India, Sri Lanka and Bangladesh
E. coloratus Günther, 1878 0 Palestine saw-scaled viper Southeastern Egypt east of the Nile and as far south as the 24th parallel, Sinai, Israel, Jordan, and the Arabian Peninsula in Saudi Arabia, Yemen and Oman
E. hughesi Cherlin, 1990 0 Hughes' saw-scaled viper Somalia: northern Migiurtinia, near Meledin
E. jogeri Cherlin, 1990 0 Joger's saw-scaled viper Western and central Mali
E. leucogaster Roman, 1972 0 White-bellied carpet viper West and northwest Africa: extreme southern Morocco, Western Sahara, Algeria (Ahaggar), the southern region of Mauritania, Senegal, northern Guinea, central Mali, Burkina Faso, western Niger and northern Nigeria
E. megalocephalus Cherlin, 1990 0 Cherlin's saw-scaled viper Red Sea island between Yemen and Eritrea (Dahlak Archipelago)
E. ocellatus Stemmler, 1970 0 African saw-scaled viper Northwest Africa: Mauritania, Senegal, Mali, Guinea, Ivory Coast, Burkina Faso, Ghana, Togo, Benin, southern Niger, Nigeria, northern Cameroon and southern Chad
E. pyramidum (Geoffroy Saint-Hilaire, 1827) 2 Egyptian saw-scaled viper Northeastern Africa: northern Egypt and central Sudan, Eritrea, Ethiopia, Somalia and northern Kenya; the southwestern Arabian Peninsula: scattered populations in western Saudi Arabia (south of the 18th parallel), Yemen, South Yemen (Hadhramaut) and Oman (Dhofar); disjunct populations in the northern regions of Libya, Tunisia and Algeria

*) Not including the nominate subspecies
T) Type species

Taxonomy

Some sources also mention several other species:[3][12][13]

See also

References

  1. 1 2 3 4 5 McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, Volume 1. Washington, District of Columbia: Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
  2. 1 2 3 4 5 Spawls S, Branch B. 1995. The Dangerous Snakes of Africa. Dubai: Ralph Curtis Books. Oriental Press. 192 pp. ISBN 0-88359-029-8.
  3. 1 2 3 4 5 6 7 8 9 Mallow D, Ludwig D, Nilson G. 2003. True Vipers: Natural History and Toxinology of Old World Vipers. Malabar, Florida: Krieger Publishing Company. 359 pp. ISBN 0-89464-877-2.
  4. ↑ Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Ithaca and London: Comstock Publishing Associates. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
  5. 1 2 "Echis". Integrated Taxonomic Information System. Retrieved 31 July 2006.
  6. ↑ What Fiery Flying Serpent Symbolized Christ? at Meridian. Accessed 22 June 2007.
  7. 1 2 Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. ISBN 0-8069-6460-X.
  8. ↑ Campbell CH. 1995. "Snake bite and snake venoms: their effects on the nervous system". In: de Wolff FA, editor. Handbook of clinical neurology, vol 21 (65). Intoxications of the nervous system, part II. Amsterdam: Elsevier Science Publications.
  9. ↑ Minton 1974. U.S. Navy. 1991.
  10. ↑ Latifi 1991.
  11. ↑ Boquet 1967.
  12. ↑ Echis at the Reptarium.cz Reptile Database. Accessed 2 August 2007.
  13. ↑ Echis omanensis, Oman saw-scaled viper at Wolfgang Wüster's homepage. Accessed 7 June 2007.

Further reading

  • Boquet P. 1967. "Pharmacology and toxicology of snake venoms of Europe and the Mediterranean regions". In: Bucherl W, editor. 1967. Venomous Animals and their Venoms. Vol. I. Paris: Masson. pp 340–58.
  • Boulenger GA. 1890. The Fauna of British India, Including Ceylon and Burma. Reptilia and Batrachia. London: Secretary of State for India in Council. (Taylor & Francis, printers). xviii + 541 pp.
  • Boulenger GA. 1896. Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the ... Viperidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiv + 727 pp. + Plates I.- XXV. (Genus Echis, p. 504).
  • Cherlin, VA. 1990. Taxonomic revision of the snake genus Echis (Viperidae). II. An analysis of taxonomy and description of new forms. Proceedings of the Zoological Institute, Leningrad, USSR Academy of Schience 207: 193-223. [202]. (in Russian).
  • Christensen PA. 1955. South African Snake Venoms and Antivenins. Johannesburg: South African Institute of Medical Research. 35 pp.
  • Cloudsley-Thompson JL. 1988. The saw-scaled viper Echis carinatus. British Herpetological Society Bulletin 24:32-33.
  • Gray JE. 1849. Catalogue of the Specimens of Snakes in the Collection of the British Museum. London: Trustees of the British Museum. (Edward Newman, printer). xv + 125 pp. [29].
  • Latifi M. 1991. The Snakes of Iran. Second Edition. Oxford, Ohio: Published by the Department of the Environment and the Society for the Study of Amphibians and Reptiles. 156 pp. ISBN 0-916984-22-2.
  • Merrem B. 1820. Versuch eines Systems der Amphibien. Tentamen Systematis Amphibiorum. Marburg: J.C. Krieger. xv + 191 pp. + 1 plate. [149].
  • Minton SA Jr. 1967. "Snakebite". In: Beeson PB, McDermott W, editors. 1967. Cecil and Loeb Textbook of Medicine. Philadelphia: Saunders. 420 pp.
  • Minton SA Jr. 1974. Venom Diseases. Springfield, Illinois: CC Thomas. 386 pp.
  • U.S. Navy. 1991. Poisonous Snakes of the World. United States Government. New York: Dover Publications Inc. 203 pp. ISBN 0-486-26629-X.

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