Viper

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Viper
Viperidae-01.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Clade: Colubroides
Family: Viperidae
Oppel, 1811
Synonyms [1]
  • Viperae Laurenti, 1768
  • Viperini Oppel, 1811
  • Viperidae Gray, 1825

The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, [2] Hawaii, Madagascar, New Zealand, Ireland, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs that permit deep penetration and injection of their venom. [3] Three subfamilies are currently recognized. [4] They are also known as viperids. The name "viper" is derived from the Latin word vipera, -ae, also meaning viper, possibly from vivus ("living") and parere ("to beget"), referring to the trait viviparity (giving live birth) common in vipers like most of the species of Boidae. [5]

Contents

Description

A rattlesnake skull, showing the long fangs used to inject venom Crotalus skull.jpg
A rattlesnake skull, showing the long fangs used to inject venom

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, just behind the eyes. Each of the two fangs is 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. This rotating mechanism allows for very long fangs to be contained in a relatively small mouth. The left and right fangs can be rotated together or independently. During a strike, the mouth can open nearly 180° and the maxilla rotates forward, erecting the fangs as late as possible so that the fangs do not become damaged, as they are brittle. The jaws close upon impact and the muscular sheaths encapsulating the venom glands contract, injecting the venom as the fangs penetrate the target. This action is very fast; in defensive strikes, it will be more a stab than a bite. Viperids use this mechanism primarily for immobilization and digestion of prey. Pre-digestion occurs as the venom contains proteases, which degrade tissues. Secondarily, it is used for self defense, though in cases with nonprey, such as humans, they may give a dry bite (not inject any venom). A dry bite allows the snake to conserve its precious reserve of venom, because once it has been depleted, time is needed to replenish it, leaving the snake vulnerable. In addition to being able to deliver dry bites, vipers can inject larger quantities of venom into larger prey targets, and smaller amounts into small prey. This causes the ideal amount of predigestion for the lowest amount of venom.

Almost all vipers have keeled scales, a stocky build with a short tail, and a triangle-shaped head distinct from the neck, owing to the location of the venom glands. The great majority 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 and ambush their prey.

Arabian Horned Viper from Arabian Peninsula Arabian Horned viper.jpg
Arabian Horned Viper from Arabian Peninsula

Compared to many other snakes, vipers often appear rather sluggish. Most are ovoviviparous: the eggs are retained inside the mother's body, and the young emerge living. However, a few lay eggs in nests. Typically, the number of young in a clutch remains constant, but as the weight of the mother increases, larger eggs are produced, yielding larger young.

Geographic range

Vipera berus pictured in Laukaa, Finland, in May 2020 Vipera berus in Finland.jpg
Vipera berus pictured in Laukaa, Finland, in May 2020

Viperid snakes are found in the Americas, Africa, Eurasia, and South Asia. In the Americas, they are native from south of 48°N. In the Old World, viperids are located everywhere except Siberia, Ireland, and north of the Arctic Circle in Norway and Sweden. [1] Wild viperids are not found in Australia. The common adder, a viperid, is the only venomous snake found in Great Britain.

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. Also being vasculotoxic in nature, viperine venom causes vascular endothelial damage and hemolysis. Death is usually caused by collapse in blood pressure. This is in contrast to elapid venoms, which 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, but this rule does not always apply; some elapid bites include proteolytic symptoms typical of viperid bites, while some viperid bites produce neurotoxic symptoms. [3]

Proteolytic venom is also dual-purpose: first, it is used for defense and to immobilize prey, as with neurotoxic venoms; second, many of the venom's enzymes have a digestive function, breaking down molecules such as lipids, nucleic acids, and proteins. [6] This is an important adaptation, as many vipers have inefficient digestive systems. [7]

Due to the nature of proteolytic venom, a viperid bite is often a very painful experience and should always be taken seriously, though it may not necessarily prove 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 fate is impossible to predict, as this depends on many factors, including the species and size of the snake involved, how much venom was injected (if any), and the size and condition of the patient before being bitten. Viper bite victims may also be allergic to the venom or the antivenom.

Behavior

These snakes can decide how much venom to inject depending on the circumstances. The most important determinant of venom expenditure is generally the size of the snake; larger specimens can deliver much more venom. The species is also important, since some are likely to inject more venom than others, may have more venom available, strike more accurately, or deliver a number of bites in a short time. In predatory bites, factors that influence the amount of venom injected include the size of the prey, the species of prey, and whether the prey item is held or released. The need to label prey for chemosensory relocation after a bite and release may also play a role. In defensive bites, the amount of venom injected may be determined by the size or species of the predator (or antagonist), as well as the assessed level of threat, although larger assailants and higher threat levels may not necessarily lead to larger amounts of venom being injected. [8]

Prey tracking

The western diamondback rattlesnake Crotalus atrox, the venom of which contains proteins allowing the snake to track down bitten prey (Westliche Diamantklapperschlange) Crotalus atrox.jpg
The western diamondback rattlesnake Crotalus atrox , the venom of which contains proteins allowing the snake to track down bitten prey

Hemotoxic venom takes more time than neurotoxic venom to immobilize prey, so viperid snakes need to track down prey animals after they have been bitten, [8] in a process known as "prey relocalization". Vipers are able to do this via certain proteins contained in their venom. This important adaptation allowed rattlesnakes to evolve the strike-and-release bite mechanism, which provided a huge benefit to snakes by minimizing contact with potentially dangerous prey animals. [9] This adaptation, then, requires the snake to track down the bitten animal to eat it, in an environment full of other animals of the same species. Western diamondback rattlesnakes respond more actively to mouse carcasses that have been injected with crude rattlesnake venom. When the various components of the venom were separated out, the snakes responded to mice injected with two kinds of disintegrins, which are responsible for allowing the snakes to track down their prey. [9]

Subfamilies

Subfamily [4] Taxon author [4] Genera [4] Common nameGeographic range [1]
Azemiopinae Liem, Marx & Rabb, 19711Fea's vipers Myanmar, southeastern Tibet across South China (Fujian, Guangxi, Jiangxi, Guizhou, Sichuan, Yunnan, Zhejiang) to Northern Vietnam
Crotalinae Oppel, 181122Pit vipersIn 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, 181113True or pitless vipers Europe, Asia, and Africa

Type genus = Vipera Laurenti, 1768 [1]

Sensory organs

Heat-sensing pits

Pit vipers have specialized sensory organs near the nostrils called heat-sensing pits. [10] The location of this organ is unique to pit vipers. These pits have the ability to detect thermal radiation emitted by warm-blooded animals, helping them better understand their environment. [11] Internally the organ forms a small pit lined with membranes, external and internal, attached to the trigeminal nerve. [10] [12] Infrared light signals the internal membranes, which in turn signal the trigeminal nerve and send the infrared signals to the brain, where they are overlaid onto the visual image created by the eyes. [13]

Taxonomy

Whether family Viperidae is attributed to Oppel (1811), as opposed to Laurenti (1768) or Gray (1825), is subject to some interpretation. The consensus among leading experts, though, is that Laurenti used viperae as the plural of vipera (Latin for "viper", "adder", or "snake") and did not intend for it to indicate 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. [1]

See also

Related Research Articles

<span class="mw-page-title-main">Elapidae</span> Family of venomous snakes

Elapidae is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus Emydocephalus. Many members of this family exhibit a threat display of rearing upwards while spreading out a neck flap. Elapids are endemic to tropical and subtropical regions around the world, with terrestrial forms in Asia, Australia, Africa, and the Americas and marine forms in the Pacific and Indian Oceans. Members of the family have a wide range of sizes, from the 18 cm (7.1 in) white-lipped snake to the 5.85 m king cobra. Most species have neurotoxic venom that is channeled by their hollow fangs, and some may contain other toxic components in various proportions. The family includes 55 genera with around 360 species and over 170 subspecies.

<span class="mw-page-title-main">Rattlesnake</span> Group of venomous snakes of the genera Crotalus and Sistrurus

Rattlesnakes are venomous snakes that form the genera Crotalus and Sistrurus of the subfamily Crotalinae. All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small animals such as birds and rodents.

Haemotoxins, hemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term haemotoxin is to some degree a misnomer since toxins that damage the blood also damage other tissues. Injury from a haemotoxic agent is often very painful and can cause permanent damage and in severe cases death. Loss of an affected limb is possible even with prompt treatment.

<span class="mw-page-title-main">Pit viper</span> Subfamily of snakes

The Crotalinae, commonly known as pit vipers, or pit adders, are a subfamily of vipers found in Asia and the Americas. Like all other vipers, they are venomous. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on both sides of the head. Currently, 23 genera and 155 species are recognized: These are also the only viperids found in the Americas. The groups of snakes represented here include rattlesnakes, lanceheads, and Asian pit vipers. The type genus for this subfamily is Crotalus, of which the type species is the timber rattlesnake, C. horridus.

<i>Agkistrodon</i> Genus of snakes

Agkistrodon is a genus of venomous pit vipers commonly known as American moccasins. The genus is endemic to North America, ranging from the Southern United States to northern Costa Rica. Eight species are currently recognized, all of them monotypic and closely related. Common names include: cottonmouths, copperheads, and cantils.

<span class="mw-page-title-main">Snakebite</span> Injury caused by bite from snakes

A snakebite is an injury caused by the bite of a snake, especially a venomous snake. A common sign of a bite from a venomous snake is the presence of two puncture wounds from the animal's fangs. Sometimes venom injection from the bite may occur. This may result in redness, swelling, and severe pain at the area, which may take up to an hour to appear. Vomiting, blurred vision, tingling of the limbs, and sweating may result. Most bites are on the hands, arms, or legs. Fear following a bite is common with symptoms of a racing heart and feeling faint. The venom may cause bleeding, kidney failure, a severe allergic reaction, tissue death around the bite, or breathing problems. Bites may result in the loss of a limb or other chronic problems or even death.

<span class="mw-page-title-main">Snake venom</span> Highly modified saliva containing zootoxins

Snake venom is a highly toxic saliva containing zootoxins that facilitates in the immobilization and digestion of prey. This also provides defense against threats. Snake venom is usually injected by unique fangs during a bite, though some species are also able to spit venom.

<span class="mw-page-title-main">Snake skeleton</span> Skeleton of a snake

A snake skeleton consists primarily of the skull, vertebrae, and ribs, with only vestigial remnants of the limbs.

<span class="mw-page-title-main">Envenomation</span> Process of venom injection

Envenomation is the process by which venom is injected by the bite or sting of a venomous animal.

<i>Bitis</i> Genus of snakes

Bitis is a genus of venomous vipers found in Africa and the southern Arabian Peninsula. It includes the largest and the smallest vipers in the world. Members are known for their characteristic threat displays that involve inflating and deflating their bodies while hissing and puffing loudly. The type species for this genus is B. arietans, which is also the most widely distributed viper in Africa. Currently, 18 species are recognized.

<span class="mw-page-title-main">Venomous snake</span> Species of the suborder Serpentes that produce venom

Venomous snakes are species of the suborder Serpentes that are capable of producing venom, which they use for killing prey, for defense, and to assist with digestion of their prey. The venom is typically delivered by injection using hollow or grooved fangs, although some venomous snakes lack well-developed fangs. Common venomous snakes include the families Elapidae, Viperidae, Atractaspididae, and some of the Colubridae. The toxicity of venom is mainly indicated by murine LD50, while multiple factors are considered to judge the potential danger to humans. Other important factors for risk assessment include the likelihood that a snake will bite, the quantity of venom delivered with the bite, the efficiency of the delivery mechanism, and the location of a bite on the body of the victim. Snake venom may have both neurotoxic and hemotoxic properties. There are about 600 venomous snake species in the world.

<i>Causus</i> Genus of snakes

Causus is a genus of vipers found only in sub-Saharan Africa. It is a group considered to be among the most primitive members of the family Viperidae based on head scalation, oviparity, venom apparatus, and because they have round pupils. However, this is contradicted by recent molecular studies. Seven species are currently recognized. They are commonly known as night adders. Like all other vipers, they are venomous.

<i>Azemiops</i> Genus of snakes

Azemiopinae is a monogeneric subfamily created for the genus Azemiops that contains the viper species A. feae and A. kharini. They are commonly known as Fea's vipers. No subspecies are recognized. The first specimen was collected by Italian explorer Leonardo Fea, and was described as a new genus and new species by Boulenger in 1888. Formerly considered to be one of the most primitive vipers, molecular studies have shown that it is the sister taxon to the pit vipers, Crotalinae. It is found in the mountains of Southeast Asia, in China, southeastern Tibet, and Vietnam. Like all other vipers, they are venomous.

<i>Vipera</i> Genus of snakes

Vipera is a genus of vipers. It has a very wide range, being found from North Africa to just within the Arctic Circle and from Great Britain to Pacific Asia. 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. Currently, 21 species are recognized. Like all other vipers, the members of this genus are venomous.

<i>Vipera ammodytes</i> Species of snake

Vipera ammodytes, commonly known as horned viper, long-nosed viper, nose-horned viper, and sand viper, poskok is a species of viper found in southern Europe, mainly northern Italy, the Balkans, and parts of Asia Minor. Like all other vipers, it is venomous. It is reputed to be the most dangerous of the European vipers due to its large size, long fangs and high venom toxicity. The specific name, ammodytes, is derived from the Greek words ammos, meaning "sand", and dutes, meaning "burrower" or "diver", despite its preference for rocky habitats. Five subspecies are currently recognized, including the nominate subspecies described here.

<span class="mw-page-title-main">Tiger rattlesnake</span> Species of snake

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<span class="mw-page-title-main">Evolution of snake venom</span> Origin and diversification of snake venom through geologic time

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<span class="mw-page-title-main">Snakebite in Latin America</span> Snake Attacks Causing Health Concern

Snakebite envenomation is considered a public health problem in Latin America, with an estimated 70,000 cases annually, but due to underreporting, these numbers may be even higher.

References

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  2. Fender-Barnett, Arli (27 May 2019). "Are Australian snakes really the most dangerous in the world?". CSIRO. Archived from the original on 9 December 2023. Yes, we have some scary snakes in Australia but none are close to what's happening in tropical parts of Asia, Africa and South America – they have a group of snakes called Vipers (which we don't have, phew!).
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  12. Newman, Eric A. (1982). "The Infrared "Vision" of Snakes". Scientific American. 243 (3): 116–127. Bibcode:1982SciAm.246c.116N. doi:10.1038/scientificamerican0382-116.
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Further reading