Saw-scaled viper (Echis carinatus)
Common names: saw-scaled vipers, carpet vipers.
Echis is a genus of venomous vipers found in the dry regions of Africa, the Middle East, India and Sri Lanka. These snakes are quick-tempered and strike readily, which, combined with a virulent hemotoxic venom, makes them very dangerous, despite their small size. They also have a characteristic threat display, rubbing sections of their body together to produce a "sizzling" warning sound. Eight species are currently recognized.
The head is short, wide, pear-shaped and distinct from the neck. The snout is short and rounded, while the eyes are relatively large and set well forward. The crown is covered with small, irregular, imbricate scales, which may be either smooth or keeled.
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-degree angle and have a central ridge, or keel, that is serrated (hence the common name). The tail is short and the subcaudals single.
Found in India and Sri Lanka, parts of the Middle East and Africa north of the equator.
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. The proper proper term for this is "stridulation." As they become more agitated, this stridulating behavior becomes faster and louder. It is postulated that this display evolved as a means of limiting water loss, such as might occur when hissing. However, some authors describe this display as being accompanied by loud hissing.
These snakes are very aggressive and will strike vigorously from the position described above. When doing so, they may overbalance and end up moving towards their aggressor as a result; most unusual behavior for a snake.
Little is known about the eating habits of some species, but of others the diet is 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.
Bites from Echis species probably result in more deaths than from any other species. The genus is recognized as medically significant in many tropical rural areas. They may be small, but they are very aggressive, quick to strike and possess an extremely virulent hemotoxic venom. There seems to be no significant correlation between the length of the specimen and the symptomology signs that occur in humans. Most victims are bitten after dark when these snakes are active.
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.
Venom toxicity varies among the different species, geographic locations, individual specimens, sexes, over the seasons, different milkings, and of course the method of injection (SC, IM, IP, IV). Consequently, the LD50 values for Echis venom 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). Latifi (1991) notes that venom from females was more than twice as toxic on average than venom from males.
The amount of venom produced also varies. Reported yields include 20-35 mg of dried venom from specimens 41-56 cm in length (Minton 1974, U.S. Navy, 1991), 6-48 mg (16 mg average) from Iranian specimens (Latifi, 1991) and 13-35 mg of dried venom from animals from various other localities (Boquet, 1967). Yield varies seasonally, as well as between the sexes: the most venom is produced during the summer months and males produce more than females.
|Species||Authority||Subsp.*||Common name||Geographic range|
|E. carinatusT||(Schneider, 1801)||4||Saw-scaled viper||Southeastern Arabian Peninsula (Oman, Masirah and eastern United Arab Emirates), southwestern Iran, Afghanistan, Uzbekistan, Turkmenistan, Tadzikhistan, 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 Saudia 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 north-west 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||In northeastern Africa: northern Egypt and central Sudan, Eritrea, Ethiopia, Somalia and northern Kenya. In the southwestern Arabian Peninsula: scattered populations in western Saudi Arabia (south of the 18th parallel), Yemen, South Yemen (Hadhramaut) and Oman (Dhofar). Disjunct populations apparently also occur in the northern regions of Libya, Tunisia and Algeria.|
*) Not including the nominate subspecies (typical form).
T) Type species.
Some sources also mention several other species:
- E. omanensis, Babocsay 2004. A new species found in the United Arab Emirates and east Oman.
- E. khosatzkii, Cherlin 1990. Found in Oman and Yemen. Considered a synonym of E. pyramidum.
- E. multisquamatus, Cherlin 1981. Described here as E. carinatus multisquamatus.
- List of viperine species and subspecies.
- True vipers - Common names.
- True vipers - Synonymy.
- McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
- Spawls S, Branch B. 1995. The Dangerous Snakes of Africa. Ralph Curtis Books. Dubai: Oriental Press. 192 pp. ISBN 0-88359-029-8.
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- Echis (TSN 634423) at Integrated Taxonomic Information System. Accessed 21 March.
- Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. ISBN 0-8069-6460-X.
- 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.
- 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. Taylor & Francis, London, xviii, 541 pp.
- 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 24:32-3.
- Latifi M. 1991. The snakes of Iran. Published by the Department of the Environment and the Society for the Study of Amphibians and Reptiles, 2nd edition. 156 pp.
- Minton SA Jr. 1967. Snakebite. In: Beeson PB, McDermott W, editors. Cecil and Loeb Textbook of Medicine. Philadelphia: Saunders. 420 pp.
- Minton SA Jr. 1974. Venom Diseases. Springfield (IL): CC Thomas Publ. 386 pp.
- U.S. Navy. 1991. Poisonous Snakes of the World. US Govt. New York: Dover Publications Inc. 203 pp. ISBN 0-486-26629-X.