| Echis | |
|---|---|
_Photographed_By_Shantanu_Kuveskar.jpg) | |
| Echis carinatus inMangaon (Maharashtra,India) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Viperidae |
| Subfamily: | Viperinae |
| Genus: | Echis Merrem, 1820 |
| Synonyms[1] | |
Echis (common names:saw-scaled vipers,carpet vipers[2]) is agenus ofvipers found in the dry regions ofAfrica, theMiddle East,India,Sri Lanka andPakistan. They have a characteristic threat display, rubbing sections of their body together to produce a "sizzling" warning sound.[3] The nameEchis is the Latin transliteration of theGreek word for "viper" (ἔχις). Like all vipers, they arevenomous. Their common name is "saw-scaled vipers" and they include some of the species responsible for causing the mostsnakebite cases and deaths in the world.[4][5] Twelvespecies are currently recognized.[6]
Saw-scaled vipers are relatively small snakes, the largest species (E. leucogaster,E. pyramidum) usually below 90 cm (35 in) long, and the smallest (E. hughesi,E. jogeri) being around 30 cm (12 in).
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. Thedorsal scales are mostlykeeled. 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 thesubcaudals are single.[3]
A saw-scaled viper of the genusEchis may be responsible for biblical claims of afiery flying serpent.[7]
Species of this genus are found inPakistan, India (in rocky regions ofMaharashtra,Rajasthan,Uttar Pradesh, andPunjab) andSri Lanka, parts of theMiddle East, andAfrica north of the equator.[1]
All members of this genus have a distinctive threat display, which involves forming a series of parallel, C-shaped coils and rubbing their scales together to produce a sizzling sound, rather like water on a hot plate.[2][3] The proper term for this isstridulation.[8] 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.[8]
These snakes can be fierce and are quick to strike. They 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]
Saw-scaled vipers are highly defensive compared to many of their cousins and they are very easy to provoke, so they might strike quickly.[citation needed]
Little is known about the diets of someEchis species. For others, their diets are reported to be extremely varied, and may include items such aslocusts,beetles,worms,slugs,spiders,scorpions,centipedes,solifugids,frogs,toads,reptiles (including othersnakes), smallmammals, andbirds.[2][3]
MostEchis species, such as those found inAfrica, areoviparous, while others, such as those in India, areviviparous.[2][3]
Thesnake venom ofEchis species consists mostly of four types of toxins:neurotoxins,cardiotoxins,hemotoxins, andcytotoxins. 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.[3]
Most of these species have venom that contains factors that can cause a consumptioncoagulopathy anddefibrination, which may persist for days to weeks. This may result in bleeding anywhere in the body, including the possibility of an intracranialhemorrhage. The latter classically occurs a few days following the bite.[9]
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, theLD50 values forEchis 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 up to 5 mg in some subspecies (Daniels, J. C. 2002).[10] Venom from females was more than twice as toxic on average as 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,[11] 6–48 mg (16 mg average) from Iranian specimens[12] and 13–35 mg of dried venom from animals from various other localities.[13] 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]
| Image | Species[1] | Taxon author[1] | Subsp.*[6] | Common name | Geographic range[1] |
|---|---|---|---|---|---|
| E. borkini | Cherlin, 1990 | 0 | SouthwesternArabian Peninsula (westernYemen, southernSaudi Arabia) | ||
.jpg) | E. carinatusT | (Schneider, 1801) | 4 | Saw-scaled viper | SoutheasternArabian Peninsula (Oman,Masirah and easternUAE), southwesternIran,Iraq,Afghanistan,Uzbekistan,Turkmenistan,Tajikistan, Pakistan (including Urak nearQuetta andAstola Island off theMakran Coast), India,Sri Lanka |
 | E. coloratus | Günther, 1878 | 0 | Painted saw-scaled viper | SoutheasternEgypt east of theNile and as far south as the 24th parallel,Sinai,Israel,Jordan, and the Arabian Peninsula inSaudi 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 centralMali,Senegal | |
| E. khosatzkii | Cherlin, 1990 | 0 | Khosatzki's saw-scaled viper | Eastern Yemen and Oman | |
| E. leucogaster | Roman, 1972 | 0 | White-bellied carpet viper | West and northwestAfrica: extreme southernMorocco,Western Sahara,Algeria (Ahaggar), the southern region ofMauritania,Senegal, northernGuinea, central Mali,Burkina Faso, westernNiger and northernNigeria | |
| E. megalocephalus | Cherlin, 1990 | 0 | Cherlin's saw-scaled viper | Red Sea island between Yemen andEritrea (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 | |
| E. omanensis | Babocsay, 2004 | 0 | Oman saw-scaled viper | United Arab Emirates, Eastern Oman | |
 | E. pyramidum | (Geoffroy Saint-Hilaire, 1827) | 2 | Egyptian saw-scaled viper | Northeastern Africa: northern Egypt and centralSudan, Eritrea,Ethiopia, Somalia and northernKenya; disjunct populations in the northern regions ofLibya,Tunisia and Algeria |
| E. romani | Trape, 2018 | 0 | Roman's carpet viper | Southwestern Chad, southern Niger, Nigeria, northern Cameroon, northwestern Central African Republic |
*) Not including the nominate subspecies
T)Type species
The taxonomy of the group was long confused, with a plethora of species of uncertain status. Several recent studies have clarified the diversity within the genus. This included the descriptions ofE. omanensis[14] andE. romani.[15]
A mitochondrial DNA phylogeny for the genus[16] demonstrated the distinctiveness ofE. borkini,E. jogeri andE. khosatzkii, but showedE. multisquamatus to be a synonym ofE. carinatus.
