Vipera (/ˈvɪpərə/; commonly known as the palaearctic vipers[2] and Eurasian vipers[3]) is a genus of snakes in the subfamilyViperinae of the familyViperidae. The genus has a very wide range, being found from North Africa to just within the Arctic Circle, and from Great Britain to Pacific Asia.[3] The Latin name vīpera is possibly derived from the Latin words vivus and pario, meaning "alive" and "bear" or "bring forth"; likely a reference to the fact that most vipers bear live young.[4] 21 species are recognized as being valid.[5] Like all other vipers, the members of this genus are venomous.
Description
Members of the genus Vipera tend to be stout and small in size. The largest of them, V. ammodytes, can reach a maximum total length (including tail) of 95 cm (37 in), and the smallest, V. monticola, reaches a maximum total length of 40 cm (16 in).
The head of the members of this genus is clearly separated from the body, triangular in shape, and in most species covered in small scales. However, some species, notably V. berus, have small plates on the top of the head. Most species have large supraocular scales that tend to extend beyond the posterior margin of the eye. Some species also have some sort of "horn" on the head, either right behind the nasal scale, or behind the supraocular scales.
The color scheme and camouflage of the members of this genus vary widely, from a grayish ground color with dark brown transverse bands to browner colors with grey transverse bands edged with black in the case of V. ammodytes.[3]
Most Vipera species prefer cooler environments. Those found at lower latitudes tend to prefer higher altitudes and dryer, rocky habitats, while the species that occur at more northern latitudes prefer lower elevations and environments that have more vegetation and moisture.[3]
All Vipera species are viviparous, giving birth to live young.[3]
Venom
Most Vipera species have venom that contains both neurotoxic and haemotoxic components. Bites vary widely in severity.
V. ammodytes is most likely the species with the most toxic venom. In a study solely involving mice, John Haynes Brown (1973) showed that the LD50 is about 1.2/mg/kg through an IV, 1.5 mg/Kg when injected in the peritoneum (IP), and 2.0 mg/kg when administered subcutaneously (SC).[6]
V. berus venom is considered to be on the lower end of the scale when it comes to toxicity. Minton (1974) suggests that the LD50 values for mice are about 0.55 mg/kg IV, 0.80 mg/kg IP, and 6.45 mg SC.[7] Venom yield tends to be lower in this species with Minton citing 10–18 mg per bite in specimens 48–62 cm (19–24 in), while Brown suggest only 6 mg for the same sized specimens.
However, bites from Vipera species are rarely as severe as those from larger Macrovipera or Daboia.[3]
Fossil record
The oldest species of the genus Vipera is the Early MioceneV. antiqua from Southern Germany.[8] The earliest known V. antiqua fossil has been dated to 22.5 million years ago.[9] A very large indeterminate Vipera was found in the Early Pliocene deposits of Mallorca. This species surpassed in size all modern relatives, with a length of nearly 2 m (6 ft 7 in), and was one of the biggest predators of its ecosystem.[10]
Southeastern France, eastern Austria (extinct), Hungary, central Italy, Croatia, Bosnia-Herzegovina, northern and northeastern Albania, Romania, northern Bulgaria, Greece, Turkey, northwestern Iran, Armenia, Azerbaijan, Georgia, Russia and across the Kazakhstan, Kirgizia and eastern Uzbekistan steppes to China (Xinjiang).
^Spawls S, Branch B (1995). The Dangerous Snakes of Africa: Natural History, Species Directory, Venoms and Snakebite. Sanibel Island, Florida: Ralph Curtis Books / Dubai: Oriental Press. 192 pp. ISBN0-88359-029-8.
^Brown, John Haynes (1973). Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. 184 pp. LCCCN 73-229. ISBN0-398-02808-7.
Arnold EN, Burton JA (1978). A Field Guide to the Reptiles and Amphibians of Britain and Europe. London: Collins. 272 pp. ISBN0-00-219318-3. (Genus Vipera, pp. 211, 214).
Boulenger GA (1896). Catalogue of the Snakes in the British Museum (Natural History). Volume II., Containing the ... Viperidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiv + 727 pp. + Plates I–XXV. (Genus Vipera, pp. 471–472.)
Laurenti JN (1768). Specimen medicum, exhibens synopsin reptilium emendatam cum experimentis circa venena et antidota reptilium austriacorum. Vienna: Joan. Thom. Nob. de Trattnern. 214 pp. + Plates I–V. (Genus Vipera, p. 99). (in Latin).