The Viperidae (vipers) are a family of
snake
Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...
s found in most parts of the world, except for
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
,
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
,
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
,
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, and various other isolated islands. They are
venomous
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
and have long (relative to non-vipers), hinged
fang
A fang is a long, pointed tooth. In mammals, a fang is a modified maxillary tooth, used for biting and tearing flesh. In snakes, it is a specialized tooth that is associated with a venom gland (see snake venom). Spiders also have external fang ...
s that permit deep penetration and
injection of their venom. Four subfamilies are currently recognized.
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
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...
(giving live birth) common in vipers like most of the species of
Boidae
The Boidae, commonly known as boas or boids, are a family of nonvenomous snakes primarily found in the Americas, as well as Africa, Europe, Asia, and some Pacific Islands. Boas include some of the world's largest snakes, with the green anacond ...
.
Description
![Crotalus skull](https://upload.wikimedia.org/wikipedia/commons/f/ff/Crotalus_skull.jpg)
All viperids have a pair of relatively long
solenoglyphous
A snake skeleton consists primarily of the skull, vertebrae, and ribs, with only vestigial remnants of the limbs.
Skull
The skull of a snake is a very complex structure, with numerous joints to allow the snake to swallow prey far larger than it ...
(hollow) fangs that are used to inject
venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
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
maxilla
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
ry 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
protease
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s, which degrade tissues. Secondarily, it is used for self defense, though in cases with nonprey, such as humans, they may give a
dry bite A dry bite is a bite by a venomous animal in which no venom is released. Dry snake bites are called "venomous snake bite without envenoming". A dry bite from a snake can still be painful, and be accompanied by bleeding, inflammation, swelling and/o ...
(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
Keeled scales refer to reptile scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale, Campbell, J. A., Lamar, W. W. (2004). ''The Venomous Reptiles of the Western Hemisphere''. Itha ...
, 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,
pupil
The pupil is a black hole located in the center of the Iris (anatomy), iris of the Human eye, eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing ...
s 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.
Compared to many other snakes, vipers often appear rather sluggish. Most are
ovoviviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...
: 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 in Finland](https://upload.wikimedia.org/wikipedia/commons/2/28/Vipera_berus_in_Finland.jpg)
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
The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by the ...
, viperids are located everywhere except
Siberia
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...
, Ireland, and north of the Arctic Circle in Norway and Sweden.
Wild viperids are not found in
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
. The
common adder
''Vipera berus'', the common European adderMallow D, Ludwig D, Nilson G. (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. . or common European viper,Stidworthy J. (1974). ...
, a viperid, is the only venomous snake found in
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
.
Venom
Viperid venoms typically contain an abundance of
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
-degrading enzymes, called
proteases
A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the for ...
, that produce symptoms such as pain, strong local swelling and
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
, 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
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
damage and
hemolysis
Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
. Death is usually caused by collapse in blood pressure. This is in contrast to
elapid
Elapidae (, commonly known as elapids ; grc, ἔλλοψ ''éllops'' "sea-fish") 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 Emydoce ...
venoms, which generally contain
neurotoxins that disable muscle contraction and cause paralysis. Death from elapid bites usually results from
asphyxiation
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that ca ...
because the diaphragm can no longer contract, but this rule does not always apply; some elapid bites include
proteolytic
Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called protease ...
symptoms typical of viperid bites, while some viperid bites produce
neurotoxic
Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specificall ...
symptoms.
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
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
s,
nucleic acid
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...
s, and proteins.
This is an important adaptation, as many vipers have inefficient digestive systems.
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
A scar (or scar tissue) is an area of fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other organs, and tissues of the body. Thus, scarring is a na ...
, and in the worst cases, the affected limb may even have to be
amputated
Amputation is the removal of a limb by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on indiv ...
. 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
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic der ...
to the venom or the
antivenom
Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...
.
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.
[Hayes WK, Herbert SS, Rehling GC, Gennaro JF. 2002. Factors that influence venom expenditure in viperids and other snake species during predatory and defensive contexts. ''In'' Schuett GW, Höggren M, Douglas ME, Greene HW. 2002. Biology of the Vipers. Eagle Mountain Publishing, LC. 580 pp. 16 plates. .]
Prey tracking
Hemotoxic
Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''hemotoxin'' is to some degree a misnomer since toxins that damage t ...
venom takes more time than neurotoxic venom to immobilize prey, so viperid snakes need to track down prey animals after they have been bitten,
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
Rattlesnakes are venomous snakes that form the genera '' Crotalus'' and '' Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small an ...
to evolve the strike-and-release bite mechanism, which provided a huge benefit to snakes by minimizing contact with potentially dangerous prey animals.
[ 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 ]disintegrin
Disintegrins are a family of small proteins (45–84 amino acids in length) from viper venoms that function as potent inhibitors of both platelet aggregation and integrin-dependent cell adhesion.
Operation
Disintegrins work by countering the bl ...
s, which are responsible for allowing the snakes to track down their prey.
Subfamilies
Type genus
In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name.
Zoological nomenclature
According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...
= '' Vipera'' Laurenti, 1768
Sensory organs
Heat-sensing pits
Pit vipers have specialized sensory organs near the nostrils called heat-sensing pits. The location of this organ is unique to pit vipers. These pits have the ability to detect thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) i ...
emitted by warm-blooded animals, helping them better understand their environment. Internally the organ
Organ may refer to:
Biology
* Organ (biology), a part of an organism
Musical instruments
* Organ (music), a family of keyboard musical instruments characterized by sustained tone
** Electronic organ, an electronic keyboard instrument
** Hammond ...
forms a small pit lined with membranes, external and internal, attached to the trigeminal nerve
In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chew ...
. Infrared light
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...
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.
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
The plural (sometimes abbreviated pl., pl, or ), in many languages, is one of the values of the grammatical category of number. The plural of a noun typically denotes a quantity greater than the default quantity represented by that noun. This de ...
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.
See also
* List of snakes
List of snakes refers to a variety of different articles and different criteria. these are listed below.
Lists General lists
*General lists:
** Snake#Taxonomy
** List of reptile genera#Order Squamata
** List of snakes by common name
**List of sn ...
, overview of all snake families and genera
* Snakebite
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 occu ...
References
Further reading
* Gray JE. 1825. A synopsis of the genera of reptiles and Amphibia, with a description of some new species. Annals of Philosophy
''Annals of Philosophy; or, Magazine of Chemistry, Mineralology, Mechanics, Natural History, Agriculture and the Arts'' was a learned journal founded in 1813 by the Scottish chemist Thomas Thomson. It shortly became a leader in its field of comme ...
, new ser., 10: 193–217.
* Laurenti JN. 1768. Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena et antidota reptilium Austriacorum. J.T. de Trattnern, Wien.
* Oppel M. 1811. Mémoire sur la classification des reptiles. Ordre II. Reptiles à écailles. Section II. Ophidiens. Annales du Musée National d'Histoire Naturelle, Paris 16: 254–295, 376–393.
External links
*
*
*
Pit vipers
{{Authority control
Snake families
Taxa named by Nicolaus Michael Oppel