Viperidae

From Wikipedia, the free encyclopedia

iViperidae

Asp viper, Vipera aspis

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae Oppel, 1811

Synonyms

Viperae - Laurenti, 1768
Viperini - Oppel, 1811
Viperidae - Gray, 1825<ref name="McD99">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).</ref>

The Viperidae are a family of venomous snakes commonly referred to as vipers, although the term viperids is more specific and distinguishes them from the viperines (subfamily Viperinae). These snakes are found all over the world, except in Australia and Madagascar. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four subfamilies are currently recognized.<ref name="ITIS">Viperidae (TSN 174294). Integrated Taxonomic Information System. Accessed on 10 August 2006.</ref>

1 Description
2 Venom
3 Subfamilies
4 Taxonomy
5 Cited references
6 External links

[edit] Description

All viperids have a pair of relatively long, solenoglyphous (hollow) fangs, that are used to inject venom from glands located towards the rear of the upper jaws. Each of the two fangs is located at the front of the mouth on a short maxillary bone that can rotate back and forth. When not in use, the fangs fold back against the roof of the mouth and are enclosed in a membranous sheath. The left and right fangs can be rotated together or independently. During a strike, the mouth can open nearly 180 degrees and the maxilla rotates forward, erecting the fang. The jaws close on impact and powerful muscles that surround the venom glands contract to inject the venom as the fangs penetrate. This action is lightning-fast and is more a stab than a bite. Viperids use this mechanism both to immobilize their prey and in self-defense.

Almost all vipers have keeled scales, a stocky build with a short tail and, due to the location of the venom glands, a triangular-shaped head distinct from the neck. Their eyes have vertically elliptical, or slit-shaped, pupils that can open wide to cover most of the eye or close almost completely, which helps them to see in a wide range of light levels. Typically, vipers are nocturnal, ambush predators.

Compared to many other snakes, vipers often appear rather sluggish. Most are ovoviviparous, giving birth to live young, but a few lay eggs. Indeed, the name of this group is derived from Latin (vivo = live, parthus = birth) and is in reference to the more common of these two reproductive modes.<ref name="Sch02">Schuett GW, Höggren M, Douglas ME, Greene HW. 2002. Biology of the Vipers. Eagle Mountain Publishing, LC. 580 pp. 16 plates. ISBN 0-9720154-0-X.</ref>

[edit] Venom

Viperid venoms typically contain an abundance of protein-degrading enzymes, called proteases, that produce symptoms such as pain, strong local swelling and necrosis, blood loss from cardiovascular damage complicated by coagulopathy, and disruption of the blood clotting system. Death is usually the result of a collapse in blood pressure. This is in contrast to elapid venoms that generally contain neurotoxins that disable muscle contraction and cause paralysis. Death from elapid bites usually results from asphyxiation because the diaphragm can no longer contract. However, this rule does not always apply: some elapid bites include proteolytic symptoms typical of viperid bites, while some viperid bites produce neurotoxic symptoms.<ref name="Slo00">Slowinski J. 2000. Striking Beauties: Venomous Snakes at California Wild. Vol. 53:2. Accessed 2 December 2006.</ref>

Proteolytic venom is also dual-purpose. Not only is it used for defensive purposes and the immobilization of prey, the same as with neurotoxic venoms, but many of the enzymes have a digestive function, breaking down molecules in prey items, such as lipids, nucleic acids, and proteins.<ref name="Slo00"/> This is important, as many vipers have weak digestive systems.<ref name="Smi04">Smith SA. 2004. Did Someone Say... SSSSnakes? at Maryland Dept. of Natural Resources. Accessed 2 December 2006.</ref>

Due to the nature of proteolytic venom, a viperid bite is often a very painful experience and should always be taken seriously, even though it is not necessarily fatal. Even with prompt and proper treatment, a bite can still result in a permanent scar, and in the worst cases the affected limb may even have to be amputated. A victim's actual fate is impossible to predict as this depends on many factors, including (but not limited to) the species and size of the snake involved, how much venom was injected (if any) and the size and condition of the patient prior to being bitten. The patient may also be allergic to the venom and/or the antivenin.

[edit] Subfamilies

Subfamily<ref name="ITIS"/>	Authority<ref name="ITIS"/>	Genera<ref name="ITIS"/>	Species<ref name="ITIS"/>	Common name	Geographic range<ref name="McD99"/>
Azemiopinae	Liem, Marx & Rabb, 1971	1	1	Fea's viper	Myanmar, southeastern Tibet across southern China (Fujien,Guangxi,Jiangxi,Kweichow,Sichuan,Yunnan,Zhejiang) to northern Vietnam.
Causinae	Cope, 1859	1	6	Night adders	Subsaharan Africa
Crotalinae	Oppel, 1811	18	151	Pit vipers	In the Old World from eastern Europe eastward through Asia to Japan, Taiwan, Indonesia, peninsular India and Sri Lanka. In the New World from southern Canada southward through Mexico and Central America to southern South America.
Viperinae	Oppel, 1811	12	66	True or pitless vipers	Europe, Asia and Africa.

Type genus = Vipera - Laurenti, 1768<ref name="McD99"/>

[edit] Taxonomy

That Viperidae is attributed to Oppel (1811), as opposed to Laurenti (1768) or Gray (1825), is subject to some interpretation. However, the consensus among leading experts is that Laurenti used viperae as the plural form of vipera (Latin for viper, adder or snake) and did not intend for it to indicate a a family group taxon. Rather, it is attributed to Oppel, based on his Viperini as a distinct family group name, despite the fact that Gray was the first to use the form Viperinae.<ref name="McD99"/>