|Echis carinatus in Mangaon, (Maharashtra, India)|
Echis (common names: saw-scaled vipers, carpet vipers) 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. The name Echis is the Latin transliteration of the Greek word for "viper" (ἔχις). 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. Eight species are currently recognized.
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.
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 term for this is stridulation. 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. However, some authors describe this display as being accompanied by loud hissing.
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).
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.
The venom of Echis species consists mostly of hemotoxins and cytotoxins. 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.
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 (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/kg (Minton, 1967). Venom from females was more than twice as toxic on average as 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, 6–48 mg (16 mg average) from Iranian specimens and 13–35 mg of dried venom from animals from various other localities. 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||Taxon author||Subsp.*||Common name||Geographic range|
|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
- 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, considered a subspecies here E. carinatus multisquamatus
- List of dangerous snakes
- List of viperine species and subspecies
- Viperinae by common name
- Viperinae by taxonomic synonyms
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|Wikimedia Commons has media related to Echis.|
- Echis photo gallery at Herpetology of Africa. Accessed 9 September 2006.
- Vipers of the genus Echis at Tomáš Mazuch. Accessed 24 November 2007.
- Photograph of a bite to the leg inflicted by saw-scaled viper