Difference between revisions of "Venom" - New World Encyclopedia

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[[Image:Waspstinger1658-2.jpg|200px|right|thumb|[[Wasp]] [[stinger (organ)|sting]], with droplet of venom]]
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'''Venom''' is any of a variety of [[toxin]]s produced by certain [[animal]]s, such as snakes, stingrays, spiders, and scorpions, and capable of being delivered, usually by a bite, sting, or spine, to another organism, causing injury, illness, or death. Venom typically is used for the purpose of defense and hunting, although some venoms may have a digestive function as well.  
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[[Image:Waspstinger1658-2.jpg|200px|right|thumb|[[Wasp]] [[stinger (organ)|sting]], with droplet of venom.]]
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'''Venom''' is any of a variety of [[toxin]]s produced by certain [[animal]]s (such as [[snake]]s, [[stingray]]s, [[spider]]s, and [[scorpion]]s) for mechanical delivery (injection) into another organism, usually by a bite, sting, or spine, causing injury, illness, or death in the victim. Venom typically is used for the purpose of defense and predation, although some venoms may provide an additional digestive function.  
  
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:mechanical means
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Venom is differentiated from the more generic term, [[poison]], in that venom is necessarily produced by living [[cell(biology)|cells]] and involves some delivery system or apparatus for introduction into the [[tissue]]s and blood stream of another organism to cause its effect. Poison, on the other hand, is not necessarily produced by living cells and it may be absorbed by the body, such as through the skin or digestive system or even inhaled, rather than introduced by mechanical means by another organism. And poison tends to be widely distributed throughout the tissues of an animal, while venoms lack free distribution throughout the body and are produced, stored, and delivered by a very specific set of organs (Takacs 2001). Examples of venom delivery systems include injection through the hollow, hypodermic-like fangs of a [[rattlesnake]] or [[cobra]], the barbed stinger of a [[honeybee]], the thin, hollow spines in fins of lionfish, or the triggering of nematocysts by [[box jellyfish]]. The spitting cobras can shoot venom from the mouth  and a hit to the eyes of the victim can cause temporary shock and blindness.
  
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Venom is differentiated from the more generic term poison in that venom is necessarily produced by living [[cell(biology)|cells]] and involves some delivery system, typically subcutaneously, to cause its effect. Poison, on the other hand, may be absorbed by ingestion or through the skin. Examples of venom delivery systems included injection through the hollow, hypodermic-like fangs of a rattlesnake or cobra, the stinger of a bee, or the triggering of nematocysts by box jellyfish. The spitting cobras can shoot venom from the mouth  and a hit to the eyes of the victim can cause temporary shock and blindness.
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Among animals widely known to use venom are snakes (such as [[elapid]]s and [[viper]]s), [[lizard]]s (such as the [[Gila monster]]), [[spider]]s, [[centipede]]s, [[scorpion]]s, stinging insects (such as [[bee]]s and [[wasp]]s), fish ([[stingray]]s, scorpionfish, along with many others), [[jellyfish]], [[mollusk]]s (such as [[cone snail]]s), and even some mammals (such as the male [[platypus]] or slow loris).  
  
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: Poisons can be absorbed by the body, such as through the skin or digestive system, while venoms must first be introduced directly into tissues or the blood stream through mechanical means. It is, for example, therefore harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract (Klauber 1997). While the term "poisonous snake" is mostly incorrect—poison is inhaled or ingested whereas venom is injected (Freiberg 1984, 125)—there are, however, poisonous snakes known to exist.   Rhabdophis sequesters toxins from the toads it eats then secretes them from nuchal glands to ward off predators, and a small population of garter snakes in Oregon retains enough toxin in their liver from the newts they eat to be effectively poisonous to local small predators such as crows and foxes (Freiberg 1984, 123).
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A large number of venoms can disrupt the human [[nervous system|nervous]], cardiovascular, and muscular systems. However, despite the dangers that many venomous animals pose, venom also offers potential benefits. Research into snake venom has produced a number of potential [[stroke]] and [[cancer]] treatment drugs, and the venom of gila monsters offers promise for [[diabetes]] treatment (Handwek 2006). Among the attractions of venoms are their often staggering potency compared to plant compounds used for medicinal purposes and their often high specificity of action (Sprackland 2005).  
  
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==Overview and terminology: Toxin, poison, venom==
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The terms [[poison]], [[toxin]], and venom are generally used in different senses.
  
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Among animals widely known to use venom are snakes (such as [[elapid]]s and [[viper]]s), lizards (such as Gila monster), spiders, centipedes, scorpions, stinging insects (such as beeds adn wasps), fishes (stingrays, scorpionfish, along with many others), and jellyfish, and male platypus.  
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'''Poison''' is the most generic of the three terms. It refers to any substance that can result in infection, illness, injury, or death when ingested or brought into contact with the skin or bloodstream of a human being or an animal (Wilson 1993).  
  
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snake venoms are generally not dangerous when ingested, and are therefore not technically poisons.
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A '''toxin''' is a chemical substance that is capable of causing [[injury]], illness, infection, or death to an organism (poison) and that is produced by living [[cell (biology)|cells]] or another organism. Toxin is specific for being produced by a living organism, while poison lacks this specificity. However, when used non-technically, the term toxin often is applied to any poisonous substance.  
  
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Cnidarians take their name from a specialized cell, the cnidocyte (nettle cell). The cnida or nematocyst is secreted by the Golgi apparatus of a cell and is technically not an organelle but "the most complex secretory product known" (Waggoner and Collins 2000). Tentacles surrounding the mouth contain nematocysts. The nematocysts are the cnidarians' main form of offense or defense and function by a chemical or physical trigger that causes the specialized cell to eject a barbed and poisoned hook that can stick into, ensnare, or entangle prey or predators, killing or at least paralyzing its victim.
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Toxins are nearly always [[protein]]s that are capable of causing harm on contact or absorption with body [[tissue]]s by interacting with biological [[macromolecule]]s such as [[enzyme]]s or cellular receptors. Toxins vary greatly in their severity, ranging from usually minor and acute (as in a [[bee]] sting) to almost immediately deadly as in [[botulinum toxin]]). Biotoxins vary greatly in purpose and mechanism, and they can be highly complex (the venom of the cone snail contains dozens of small proteins, each targeting a specific nerve channel or receptor), or a single, relatively small protein.
  
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Mechanics of spitting Venom can be ejected otherwise than by a bite, as in the so-called spitting cobras of the genera Naja and Hemachatus. Some of these deadly snakes, when irritated, are capable of shooting venom from the mouth, at a distance of 4 to 8 feet. These snakes' fangs have been modified for the purposes of spitting: inside the fangs of a spitting cobra is a channel which makes a ninety degree bend to the lower front of the fang. When the snake is threatened the muscles of the venom gland squeeze the venom sack and as a result venom is projected forward. Spitters may spit thirty or forty times in succession, and even then the snake is still able to deliver a fatal bite.
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'''Venoms''' usually are defined as toxins secreted by certain animals that utilize an apparatus or delivery system to inject them into another organism, such as delivered subcutaneously by a bite, sting, spine, or other means.  
  
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Spitting is a defensive reaction only. The snake tends to aim for the eyes of a perceived threat; a direct hit can cause temporary shock and blindness through severe inflammation of the cornea and conjunctiva.
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While venom is occasionally, but rarely, used as a synonym of the more generic poison (Wilson 1993), in general there is a distinction made between "venomous organism" and "poisonous organism." ''Venomous,'' as stated above, refers to animals that deliver (often, inject) venom into their [[prey]] when hunting or as a defense mechanism. ''Poisonous,'' on the other hand, describes plants or animals that are harmful when consumed or touched (Wilson 1993). A poison also tends to be distributed over a large part of the body of the organism producing it, while venom is typically produced, stored, and delivered in organs specialized for this purpose and not distributed freely in other tissues (Takacs 2001). Poisonous animals lack localized or specific apparatuses for production, storage, or delivery of poisons, with the entire body, or a large part of it, poisonous (Takacs 2001).  
  
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Plants can be poisonous, not venomous. Animals can be venomous, poisonous, or both venomous and poisonous. The [[slow loris]], a primate, has poison-secreting patches on the inside of its elbows, which it is believed to smear on its young to prevent them from being eaten. However, it will also lick these patches, giving it a venomous bite. On the other hand, the [[Hooded Pitohui|hooded pitohui]], a type of bird, is not venomous, but is poisonous, secreting a [[neurotoxin]] onto its skin and feathers. Most snakes are venomous, but poisonous snakes are also known to exist. ''Rhabdophis tigrinus,'' a [[colubrid]] snake common in Japan, sequesters toxins from the toads it eats then secretes them from nuchal glands to ward off predators (Hutchinson et al. 2007).
  
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==Terminology: Toxin, poison, venom==
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The distinction between poison and venom can be seen in the fact that snake venoms are generally not dangerous when ingested, as long as there are no lacerations inside the mouth or digestive tract (Klauber 1997); thus, they are not called poisons.  
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A '''toxin''' is a chemical substance that is capable of causing [[injury]], illness, or death to an organism ([[poison]]) and that is produced by living [[cell (biology)|cells]] or another organism.
 
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Toxins are nearly always [[protein]]s that are capable of causing harm on contact or absorption with body [[tissue]]s by interacting with biological [[macromolecule]]s such as [[enzyme]]s or cellular receptors. Toxins vary greatly in their severity, ranging from usually minor and acute (as in a [[bee]] sting) to almost immediately deadly (as in [[botulinum toxin]]).
 
  
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Biotoxins vary greatly in purpose and mechanism, and they can be highly complex (the [[venom]] of the cone snail contains dozens of small proteins, each targeting a specific nerve channel or receptor), or a single, relatively small protein.
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==Examples of venomous animals==
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Venom is found among both [[vertebrate]]s and [[invertebrate]]s.  
  
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Among '''vertebrates,''' perhaps the most widely known venomous animals are the [[snake]]s, some species of which inject venom into their prey through hollow [[tooth|fang]]s. Over 2,000 species are known to be venomous (Fry et al. 2006; Zimmer 2005; UM 2005). This number has recently increased greatly from a few hundred as research has revealed venom toxins in what previously were thought to be non-venomous snakes, and although these snakes have small quantities of venom and lack fangs, the venom still can be delivered via their sharp teeth (UM 2003). Although venom is found in several families of snakes, the two most well-known families of venomous snakes are [[Elapidae]] (including the cobras, mambas, and sea snakes) and [[Viperidae]] (vipers, such as [[rattlesnake]]s and puff adders).
  
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The term toxin comes from the Greek {{polytonic|τοξικόν}} ''toxikon'', meaning "(poison) for use on arrows." In the context of [[biology]], '''poisons''' are substances that can cause damage, [[illness]], or [[death]] to [[organism]]s, usually by [[chemical reaction]] or other [[activity]] on the [[molecular]] scale, when a sufficient quantity is absorbed by an organism.
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The [[gila monster]] and [[bearded lizard]] are two lizards that have venom and venom delivery system, although similar venom toxins now have been found more widely in lizards (Fry et al. 2006).
  
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'''Toxin''' is a subcategory of poison, referring to a substance produced by a living organism. However, when used non-technically, the term "toxin" is often applied to any poisonous substance. Many non-technical and lifestyle journalists also follow this usage to refer to toxic substances in general, though some specialist journalists maintain the distinction that toxins are only those produced by living organisms. In the context of [[alternative medicine]] the term toxin often is used nonspecifically as well to refer to any substance claimed to cause ill health, ranging anywhere from trace amounts of pesticides to common [[food]] items like refined [[sugar]] or additives like [[artificial sweetener]]s and [[Monosodium glutamate|MSG]].  
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Some believe venomous fish (not to be confused with poisonous fish) outnumber all other venomous vertebrates combined (Handwerk 2006). Venom can also be found in some cartilaginous fish ([[stingrays]], [[shark]]s, and [[chimaera]]s) and in [[teleost]] fish, including [[monognathus]] eels, [[catfish]]es, [[stonefish]]es, [[scorpionfish]]es, [[lionfish]]es, gurnard perches, [[rabbitfish]]es, [[surgeonfish]]es, [[Scatophagidae|scats]], [[stargazers]], [[weever]]s, [[carangid]]s, [[saber-toothed blenny]], and [[toadfish]].  
  
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In pop [[psychology]], the term toxin sometimes is used to describe things that have an adverse effect on psychological health, such as a "toxic relationship," "toxic work environment," or "toxic shame."
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Although uncommon in mammals, two animals known to be venomous are the duck-billed [[platpus]], which has a spur on the heel behind each leg, and the slow loris ''(Nycticebus)'', species of primates that can have a venomous bite from licking toxins produced from glands on the insides of the elbows. Some [[solenodon]]s and [[shrew]]s also are venomous.  
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'''Venoms''' usually are defined as biologic toxins that are delivered subcutaneously, such as injected by a bite or sting, to cause their effect. In normal usage, a poisonous organism is one that is harmful to consume, but a venomous organism uses poison to defend itself while still alive. A single organism can be both venomous and poisonous.
 
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The derivative forms "toxic" and "poisonous" are synonymous.
 
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==Venomous vs. poisonous==
 
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There is a difference between organisms that are "venomous" and those that are "[[poisonous]]", two commonly confused terms applied to [[plant]] and [[animal]] life. ''Venomous'', as stated above, refers to animals that deliver (often, [[Wiktionary:inject|inject]]) venom into their [[prey]] when hunting or as a defense mechanism. ''Poisonous'', on the other hand, describes plants or animals that are harmful when consumed or touched.<ref>''E.g.'', Kenneth G. Wilson, ''The Columbia Guide to Standard American English''.  1993.</ref> A poison tends to be distributed over a large part of the body of the organism producing it, while venom is typically produced in organs specialized for the purpose.<ref>[http://www.fathom.com/course/10701017/session1.html Zoltan Takacs, The Biology of Venomous Animals. Session 1. Columbia University, 2001.]</ref>  One species of bird, the [[Hooded Pitohui|hooded pitohui]], although not venomous, is poisonous, secreting a [[neurotoxin]] onto its skin and feathers. The [[slow loris]], a primate, blurs the boundary between poisonous and venomous; it has poison-secreting patches on the inside of its elbows which it is believed to smear on its young to prevent them from being eaten. However, it will also lick these patches, giving it a venomous bite.
 
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venom is type of poison, but greater specific for those wit delivery system, and of biological nature.
 
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or, better still, poison more general term and venom is a specific type of poison.. This seems most common that it is aposion with an active component. Poison is either seen as a more general term, of which venom is a subcategory, or is itself viewed as.. In this sense, plants are poisionous, snakes generally venomous, though some are poisonous as well.
 
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==Examples==
 
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The animals most widely known to use venom are [[snake]]s, some species of which inject venom into their prey through hollow [[tooth|fang]]s; [[spider (animal)|spiders]] and [[centipede]]s, which also inject venom through fangs; [[scorpion]]s and stinging [[insect]]s, which inject venom with a sting (which, in insects such as [[bees]] and [[wasps]], is a modified egg-laying device – the [[ovipositor]]). Many [[caterpillar]]s have defensive venom glands associated with specialized bristles on the body, known as [[urtication|urticating hairs]], and can be lethal to humans (e.g., that of the ''[[Lonomia]]'' moth).  Venom is also found in a few reptiles besides snakes, such as the [[gila monster]] and [[Mexican beaded lizard]]. Other insects, such as [[Hemiptera|true bug]]s [http://ufbir.ifas.ufl.edu/Chap23.htm] and many [[ants]], also produce venom. Venom can also be found in some [[fish]], such as the cartilaginous fishes – [[stingrays]], [[shark]]s, and [[chimaera]]s – and the [[teleost]] fishes including [[monognathus]] eels, [[catfishes]], [[stonefish]]es and waspfishes, [[scorpionfish]]es and [[lionfish]]es, gurnard perches, [[rabbitfishes]], [[surgeonfish]]es, [[Scatophagidae|scats]], [[stargazers]], [[weever]]s, [[carangid]]s, [[saber-toothed blenny]], and [[toadfish]].  In fact, recent studies have shown that there are more venomous ray-finned fishes than all other venomous [[vertebrate]]s combined. There are many other venomous invertebrates, including [[jellyfish]] and [[cone snails]]. The [[box jellyfish]] is widely considered the most venomous creature in the world.[http://en.wikipedia.org/wiki/Box_jellyfish#treatmentofstings]  Some mammals are also venomous, including [[solenodon]]s, [[shrews]], the [[slow loris]], and the male [[platypus]].
 
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Because they are tasked to defend their hives and food stores, bees synthesize and employ an acidic venom ([[apitoxin]]) to cause pain in those that they sting, whereas wasps use a chemically different venom designed to paralyze prey, so it can be stored alive in the food chambers of their young. The use of venom is much more widespread than just these examples, of course.
 
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Mechanics of spitting Venom can be ejected otherwise than by a bite, as in the so-called spitting cobras of the genera Naja and Hemachatus. Some of these deadly snakes, when irritated, are capable of shooting venom from the mouth, at a distance of 4 to 8 feet. These snakes' fangs have been modified for the purposes of spitting: inside the fangs of a spitting cobra is a channel which makes a ninety degree bend to the lower front of the fang. When the snake is threatened the muscles of the venom gland squeeze the venom sack and as a result venom is projected forward. Spitters may spit thirty or forty times in succession, and even then the snake is still able to deliver a fatal bite.
 
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Spitting is a defensive reaction only. The snake tends to aim for the eyes of a perceived threat; a direct hit can cause temporary shock and blindness through severe inflammation of the cornea and conjunctiva. While there are no serious results if the venom is washed away at once with plenty of water, the blindness caused by a successful spit can become permanent if left untreated. Contact with the skin is not in itself dangerous, but open wounds may become envenomed.
 
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spitting cobras of the genera Naja and Hemachatus. Some of these deadly snakes, when irritated, are capable of shooting venom from the mouth, at a distance of 4 to 8 feet. These snakes' fangs have been modified for the purposes of spitting: inside the fangs of a spitting cobra is a channel which makes a ninety degree bend to the lower front of the fang. When the snake is threatened the muscles of the venom gland squeeze the venom sack and as a result venom is projected forward. Spitters may spit thirty or forty times in succession, and even then the snake is still able to deliver a fatal bite.
 
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Spitting is a defensive reaction only. The snake tends to aim for the eyes of a perceived threat; a direct hit can cause temporary shock and blindness through severe inflammation of the cornea and conjunctiva.
 
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nematocyst is secreted by the Golgi apparatus of a cell and is technically not an organelle but "the most complex secretory product known" (Waggoner and Collins 2000). Tentacles surrounding the mouth contain nematocysts. The nematocysts are the cnidarians' main form of offense or defense and function by a chemical or physical trigger that causes the specialized cell to eject a barbed and poisoned hook that can stick into, ensnare, or entangle prey or predators, killing or at least paralyzing its victim.
 
  
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Among '''invertebrates,''' animals widely known to use venom are [[spider (animal)|spiders]] and [[centipede]]s, which inject venom through fangs; and [[scorpion]]s and stinging [[insect]]s, which inject venom with a sting (which, in insects such as [[bees]] and [[wasps]], is a modified egg-laying device&mdash;the [[ovipositor]]). Many [[caterpillar]]s have defensive venom glands associated with specialized bristles on the body, known as [[urtication|urticating hairs]], and can be lethal to humans (for example, that of the ''[[Lonomia]]'' moth). The stinging hairs or spines of caterpillars of some moths may be hollow and connected to poison glands, with the venom flowing on contact (Lyon 2000). Various ants and true bugs produce venom as well. Other invertebrates that produce venom include [[jellyfish]] and [[cone snail]]s. The [[box jellyfish]] is widely considered the most venomous creature in the world. Nematocysts, a venomous secretory product, are the [[cnidarian]]s' main form of offense or defense. They function by a chemical or physical trigger that causes the specialized cell to eject a barbed and poisoned hook that can stick into, ensnare, or entangle prey or predators, killing or at least paralyzing its victim.
  
 
==Snake venom==
 
==Snake venom==
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Snake venoms are complex mixtures of proteins and are stored in poison glands at the back of the head (Freiberg 1984, 123). In all venomous snakes, these glands open through ducts into grooved or hollow teeth in the upper jaw (Mehrtens 1987, 243; Freiberg 1984, 5). These proteins can potentially be a mix of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins, and many other toxins that affect the body in different ways (Frieberg 1984, 125). Almost all snake venom contains hyaluronidase, an enzyme that ensures rapid diffusion of the venom (Mehrtens 1987, 243).
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Snake venoms are complex mixtures of proteins and are stored in glands at the back of the head (Freiberg 1984, 123). Typically, these glands open through ducts into grooved or hollow teeth in the upper jaw (Mehrtens 1987, 243; Freiberg 1984, 5). These proteins can potentially be a mix of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins, and many other toxins that affect the body in different ways (Frieberg 1984, 125). Almost all snake venom contains hyaluronidase, an enzyme that ensures rapid diffusion of the venom (Mehrtens 1987, 243).
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Venomous snakes that use hemotoxins usually have the fangs that secrete the venom in the front of their mouths, making it easier for them to inject the venom into their victims (Frieberg 1984, 125). Some snakes that use neurotoxins, such as the mangrove snake, have their fangs located in the back of their mouths, with the fangs curled backwards. This makes it both difficult for the snake to use its venom and for scientists to milk them (Frieberg 1984, 125). Elapid snakes, however, such as cobras and kraits, are proteroglyphous, possessing hollow fangs that cannot be erected toward the front of their mouths and cannot "stab" like a viper; they must actually bite the victim (Mehrtens 1987, 242).
 
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Snake venom is produced by glands below the eye and delivered to the victim through tubular or channeled fangs. Snake poisons contain a variety of [[peptide]] toxins. Snakes use their venom principally for hunting, though the threat of being bitten serves also as a defense. Snake bites cause a variety of symptoms including pain, swelling, tissue damage, low blood pressure, convulsions, and hemorrhaging (varying by species of snake).
 
  
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Doctors treat victims of a venomous bite with [[antivenin]], which is created by dosing an animal such as a [[sheep]], [[horse]], [[goat]], or [[rabbit]] with a small amount of the targeted venom. The immune system of the subject animal responds to the dose, producing [[antibodies]] to the venom's active molecule; the antibodies can then be harvested from the animal's blood and applied to treat envenomation in others. This treatment can be used effectively only a limited number of times  for a given person, however, as that person will ultimately develop antibodies to neutralize the foreign animal antibodies injected into him (anti-antibody antibodies). Even if that person does not suffer a serious allergic reaction to the antivenom, his own immune system can destroy the antivenin before the antivenin can destroy the venom. Though most people never require even one treatment of antivenin in their lifetime, let alone several, people who work with snakes or other venomous animals may. Fortunately, these people often develop antibodies of their own against the venom of whatever animals they handle, and thereby are protected without the  assistance of exogenous antibodies.
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Venomous snakes that use hemotoxins usually have the fangs that secrete the venom in the front of their mouths, making it easier for them to inject the venom into their victims (Frieberg 1984, 125). Some snakes that use neurotoxins, such as the mangrove snake, have their fangs located in the back of their mouths, with the fangs curled backwards. This makes it both difficult for the snake to use its venom and for scientists to milk them (Frieberg 1984, 125). Vipers (Viperidae) have a single pair of long, hollow, venom-injecting fangs that can be folded back against the top of the mouth, tip inward, when the mouth is closed. Elapid snakes, however, such as cobras and kraits, are proteroglyphous, possessing hollow fangs that cannot be folded toward the roof of their mouths and cannot "stab" like a viper; they must actually bite the victim (Mehrtens 1987, 242).
  
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[[Aristolochia rugosa]] and [[Aristolochia trilobata]], or "Dutchman's Pipe," are recorded in a list of plants used worldwide and in the West Indies, South and Central America against snakebites and scorpion stings. [[Aristolochic acid]] inhibits inflammation induced by immune complexes, and nonimmunological agents (carrageenan or croton oil).{{Fact|date=January 2008}} Aristolochic acid inhibits the activity of snake venom phospholipase (PLA2) by forming a 1:1 complex with the enzyme. Since phospholipase enzymes play a significant part in the cascade leading to the inflammatory and pain response, their inhibition could lead to relief of problems from scorpion envenomation.
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Snake bites cause a variety of symptoms including pain, swelling, tissue damage, low blood pressure, convulsions, and hemorrhaging (varying by species of snake).
  
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==See also==
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Doctors treat victims of a venomous bite with [[antivenin]], which can be created by dosing an animal such as a [[sheep]], [[horse]], [[goat]], or [[rabbit]] with a small amount of the targeted venom. The immune system of the subject animal responds to the dose, producing [[antibody|antibodies]] to the venom's active molecule; the antibodies can then be harvested from the animal's blood and applied to treat envenomation in others. This treatment can be used effectively only a limited number of times for a given person, however, as that person will ultimately develop antibodies to neutralize the foreign animal antibodies injected into him ([[anti-antibody antibodies]]). Even if that person does not suffer a serious allergic reaction to the antivenom, his own immune system can destroy the antivenin before the antivenin can destroy the venom. Though most people never require even one treatment of antivenin in their lifetime, let alone several, people who work with snakes or other venomous animals may. Fortunately, these people may develop antibodies of their own against the venom of whatever animals they handle, and thereby are protected without the  assistance of exogenous antibodies.
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* [[Toxin]]
 
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* [[Poison]]  
 
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* [[Toxinology]]
 
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* [[Schmidt Sting Pain Index]]
 
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* [[Venomous mammals]]
 
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* [[Venomous fish]]
 
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* [[Big Four (Indian snakes)]]
 
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* [[Envenomation]]
 
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* [[:Category:Venomous animals|Venomous animals]] (category)
 
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==Notes==
 
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{{reflist}}
 
  
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==References==
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* Farmer, S. 2004. [http://ohioline.osu.edu/hyg-fact/2000/2130.html Poisonous and venomous species of the Caribbean: Final paper.] ''Miami University''. Retrieved July 29, 2008.
 
* Freiberg, M., and J. Walls. 1984. ''The World of Venomous Animals''. New Jersey: TFH Publications. ISBN 0876665679.
 
* Freiberg, M., and J. Walls. 1984. ''The World of Venomous Animals''. New Jersey: TFH Publications. ISBN 0876665679.
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* Fry, B.G., N. Vidal, J.A. Norman, F.J. Vonk, H. Scheib, R. Ramjan, and S. Kuruppu. 2006. [http://www.nature.com/nature/journal/v439/n7076/abs/nature04328.html Early evolution of the venom system in lizards and snakes.] ''Nature'' (Letters) 439: 584-588. Retrieved July 27, 2008.
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* Handwerk, B. 2006. [http://news.nationalgeographic.com/news/2006/09/060901-fish-venom_2.html Venomous fish far outnumber snakes, other vertebrates, study says.] ''National Geographic News'' September 1, 2006. Retrieved July 29, 2008.
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* Klauber, L. M. 1997. ''Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind'', 2nd edition. Berkeley, CA: University of California Press. ISBN 0520210565.
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* Holland, J.S. 2008. [http://ngm.nationalgeographic.com/2008/06/nudibranchs/holland-text Living color: Toxic nudibranchs&mdash;soft, seagoing slugs&mdash;produce a brilliant defense.] ''National Geographic'' June 2008. Retrieved July 23, 2008.
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* Hutchinson, D.A., A. Mori, A.H. Savitzky, G.M. Burghardt, X. Wu, J. Meinwald, and F.C. Schroeder. 2007. [http://www.pnas.org/content/104/7/2265.full.pdf Dietary sequestration of defensive steroids in nuchal glands of the Asian snake ''Rhabdophis tigrinus.''] ''PNAS'' 104(7): 2265-2270. Retrieved July 29, 2008.
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* Klauber, L.M. 1997. ''Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind,'' 2nd edition. Berkeley, CA: University of California Press. ISBN 0520210565.
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* Lyon, W.F. 2000. [http://ohioline.osu.edu/hyg-fact/2000/2130.html Stinging hair caterpillars.] ''Ohio State University Extension Fact Sheet''. Retrieved July 29, 2008.
 
* Mehrtens, J. 1987. ''Living Snakes of the World in Color''. New York: Sterling. ISBN 0806964618.
 
* Mehrtens, J. 1987. ''Living Snakes of the World in Color''. New York: Sterling. ISBN 0806964618.
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* Smith, L., and W.C. Wheeler. 2006. Venom evolution widespread in fishes: A phylogenetic road map for the bioprospecting of piscine venoms. ''Journal of Heredity'' 97(3): 206-217.
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==Bibliography==
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* Sprackland, R.G. 2005. [http://www.naturalhistorymag.com/1005/1005_feature.html Toxic treasure.] ''Natural History Magazine'' October 2005. Retrieved July 29, 2008.
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* Leo Smith and Ward C. Wheeler. 2006. Venom evolution widespread in fishes: A phylogenetic road map for the bioprospecting of piscine venoms. Journal of Heredity 97(3): 206-217.
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* Takacs, Z. 2001. [http://www.fathom.com/course/10701017/session1.html The biology of venomous animals. Session 1. Venomous and poisonous creatures.] ''Columbia University''. Retrieved July 29, 2008.
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* Lans C, Harper T, Georges K, Bridgewater E. 2001. Medicinal and ethnoveterinary remedies of hunters in Trinidad. BMC Complement Altern Med. 2001;1:10. Epub 2001 Nov 30. http://www.biomedcentral.com/1472-6882/1/10
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* University of Melbourne (UM). 2003. [http://www.sciencedaily.com/releases/2003/12/031216075937.htm Venom hunt finds "harmless" snakes a potential danger.] ''ScienceDaily'' December 16, 2003. Retrieved July 27, 2008.
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* Wilson, K.G. 1993. [http://www.bartleby.com/68/33/6333.html venom, poison (nn.), poisonous, venomous (adjs.).] ''Columbia Guide to Standard American English''. Retrieved July 29, 2008.
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* Zimmer, C. 2005. [http://www.nytimes.com/2005/11/22/science/22venom.html Clues to the origin of snake venom.] ''New York Times'' November 22, 2005. Retrieved July 27, 2008.
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http://www.bartleby.com/68/33/6333.html Bartleby
 
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{{Poisoning and toxicity}}
 
  
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]

Latest revision as of 12:41, 13 August 2008

Wasp sting, with droplet of venom.

Venom is any of a variety of toxins produced by certain animals (such as snakes, stingrays, spiders, and scorpions) for mechanical delivery (injection) into another organism, usually by a bite, sting, or spine, causing injury, illness, or death in the victim. Venom typically is used for the purpose of defense and predation, although some venoms may provide an additional digestive function.

Venom is differentiated from the more generic term, poison, in that venom is necessarily produced by living cells and involves some delivery system or apparatus for introduction into the tissues and blood stream of another organism to cause its effect. Poison, on the other hand, is not necessarily produced by living cells and it may be absorbed by the body, such as through the skin or digestive system or even inhaled, rather than introduced by mechanical means by another organism. And poison tends to be widely distributed throughout the tissues of an animal, while venoms lack free distribution throughout the body and are produced, stored, and delivered by a very specific set of organs (Takacs 2001). Examples of venom delivery systems include injection through the hollow, hypodermic-like fangs of a rattlesnake or cobra, the barbed stinger of a honeybee, the thin, hollow spines in fins of lionfish, or the triggering of nematocysts by box jellyfish. The spitting cobras can shoot venom from the mouth and a hit to the eyes of the victim can cause temporary shock and blindness.

Among animals widely known to use venom are snakes (such as elapids and vipers), lizards (such as the Gila monster), spiders, centipedes, scorpions, stinging insects (such as bees and wasps), fish (stingrays, scorpionfish, along with many others), jellyfish, mollusks (such as cone snails), and even some mammals (such as the male platypus or slow loris).

A large number of venoms can disrupt the human nervous, cardiovascular, and muscular systems. However, despite the dangers that many venomous animals pose, venom also offers potential benefits. Research into snake venom has produced a number of potential stroke and cancer treatment drugs, and the venom of gila monsters offers promise for diabetes treatment (Handwek 2006). Among the attractions of venoms are their often staggering potency compared to plant compounds used for medicinal purposes and their often high specificity of action (Sprackland 2005).

Overview and terminology: Toxin, poison, venom

The terms poison, toxin, and venom are generally used in different senses.

Poison is the most generic of the three terms. It refers to any substance that can result in infection, illness, injury, or death when ingested or brought into contact with the skin or bloodstream of a human being or an animal (Wilson 1993).

A toxin is a chemical substance that is capable of causing injury, illness, infection, or death to an organism (poison) and that is produced by living cells or another organism. Toxin is specific for being produced by a living organism, while poison lacks this specificity. However, when used non-technically, the term toxin often is applied to any poisonous substance.

Toxins are nearly always proteins that are capable of causing harm on contact or absorption with body tissues by interacting with biological macromolecules such as enzymes or cellular receptors. Toxins vary greatly in their severity, ranging from usually minor and acute (as in a bee sting) to almost immediately deadly as in botulinum toxin). Biotoxins vary greatly in purpose and mechanism, and they can be highly complex (the venom of the cone snail contains dozens of small proteins, each targeting a specific nerve channel or receptor), or a single, relatively small protein.

Venoms usually are defined as toxins secreted by certain animals that utilize an apparatus or delivery system to inject them into another organism, such as delivered subcutaneously by a bite, sting, spine, or other means.

While venom is occasionally, but rarely, used as a synonym of the more generic poison (Wilson 1993), in general there is a distinction made between "venomous organism" and "poisonous organism." Venomous, as stated above, refers to animals that deliver (often, inject) venom into their prey when hunting or as a defense mechanism. Poisonous, on the other hand, describes plants or animals that are harmful when consumed or touched (Wilson 1993). A poison also tends to be distributed over a large part of the body of the organism producing it, while venom is typically produced, stored, and delivered in organs specialized for this purpose and not distributed freely in other tissues (Takacs 2001). Poisonous animals lack localized or specific apparatuses for production, storage, or delivery of poisons, with the entire body, or a large part of it, poisonous (Takacs 2001).

Plants can be poisonous, not venomous. Animals can be venomous, poisonous, or both venomous and poisonous. The slow loris, a primate, has poison-secreting patches on the inside of its elbows, which it is believed to smear on its young to prevent them from being eaten. However, it will also lick these patches, giving it a venomous bite. On the other hand, the hooded pitohui, a type of bird, is not venomous, but is poisonous, secreting a neurotoxin onto its skin and feathers. Most snakes are venomous, but poisonous snakes are also known to exist. Rhabdophis tigrinus, a colubrid snake common in Japan, sequesters toxins from the toads it eats then secretes them from nuchal glands to ward off predators (Hutchinson et al. 2007).

The distinction between poison and venom can be seen in the fact that snake venoms are generally not dangerous when ingested, as long as there are no lacerations inside the mouth or digestive tract (Klauber 1997); thus, they are not called poisons.

Examples of venomous animals

Venom is found among both vertebrates and invertebrates.

Among vertebrates, perhaps the most widely known venomous animals are the snakes, some species of which inject venom into their prey through hollow fangs. Over 2,000 species are known to be venomous (Fry et al. 2006; Zimmer 2005; UM 2005). This number has recently increased greatly from a few hundred as research has revealed venom toxins in what previously were thought to be non-venomous snakes, and although these snakes have small quantities of venom and lack fangs, the venom still can be delivered via their sharp teeth (UM 2003). Although venom is found in several families of snakes, the two most well-known families of venomous snakes are Elapidae (including the cobras, mambas, and sea snakes) and Viperidae (vipers, such as rattlesnakes and puff adders).

The gila monster and bearded lizard are two lizards that have venom and venom delivery system, although similar venom toxins now have been found more widely in lizards (Fry et al. 2006).

Some believe venomous fish (not to be confused with poisonous fish) outnumber all other venomous vertebrates combined (Handwerk 2006). Venom can also be found in some cartilaginous fish (stingrays, sharks, and chimaeras) and in teleost fish, including monognathus eels, catfishes, stonefishes, scorpionfishes, lionfishes, gurnard perches, rabbitfishes, surgeonfishes, scats, stargazers, weevers, carangids, saber-toothed blenny, and toadfish.

Although uncommon in mammals, two animals known to be venomous are the duck-billed platpus, which has a spur on the heel behind each leg, and the slow loris (Nycticebus), species of primates that can have a venomous bite from licking toxins produced from glands on the insides of the elbows. Some solenodons and shrews also are venomous.

Among invertebrates, animals widely known to use venom are spiders and centipedes, which inject venom through fangs; and scorpions and stinging insects, which inject venom with a sting (which, in insects such as bees and wasps, is a modified egg-laying device—the ovipositor). Many caterpillars have defensive venom glands associated with specialized bristles on the body, known as urticating hairs, and can be lethal to humans (for example, that of the Lonomia moth). The stinging hairs or spines of caterpillars of some moths may be hollow and connected to poison glands, with the venom flowing on contact (Lyon 2000). Various ants and true bugs produce venom as well. Other invertebrates that produce venom include jellyfish and cone snails. The box jellyfish is widely considered the most venomous creature in the world. Nematocysts, a venomous secretory product, are the cnidarians' main form of offense or defense. They function by a chemical or physical trigger that causes the specialized cell to eject a barbed and poisoned hook that can stick into, ensnare, or entangle prey or predators, killing or at least paralyzing its victim.

Snake venom

Snake venoms are complex mixtures of proteins and are stored in glands at the back of the head (Freiberg 1984, 123). Typically, these glands open through ducts into grooved or hollow teeth in the upper jaw (Mehrtens 1987, 243; Freiberg 1984, 5). These proteins can potentially be a mix of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins, and many other toxins that affect the body in different ways (Frieberg 1984, 125). Almost all snake venom contains hyaluronidase, an enzyme that ensures rapid diffusion of the venom (Mehrtens 1987, 243).

Venomous snakes that use hemotoxins usually have the fangs that secrete the venom in the front of their mouths, making it easier for them to inject the venom into their victims (Frieberg 1984, 125). Some snakes that use neurotoxins, such as the mangrove snake, have their fangs located in the back of their mouths, with the fangs curled backwards. This makes it both difficult for the snake to use its venom and for scientists to milk them (Frieberg 1984, 125). Vipers (Viperidae) have a single pair of long, hollow, venom-injecting fangs that can be folded back against the top of the mouth, tip inward, when the mouth is closed. Elapid snakes, however, such as cobras and kraits, are proteroglyphous, possessing hollow fangs that cannot be folded toward the roof of their mouths and cannot "stab" like a viper; they must actually bite the victim (Mehrtens 1987, 242).

Snake bites cause a variety of symptoms including pain, swelling, tissue damage, low blood pressure, convulsions, and hemorrhaging (varying by species of snake).

Doctors treat victims of a venomous bite with antivenin, which can be created by dosing an animal such as a sheep, horse, goat, or rabbit with a small amount of the targeted venom. The immune system of the subject animal responds to the dose, producing antibodies to the venom's active molecule; the antibodies can then be harvested from the animal's blood and applied to treat envenomation in others. This treatment can be used effectively only a limited number of times for a given person, however, as that person will ultimately develop antibodies to neutralize the foreign animal antibodies injected into him (anti-antibody antibodies). Even if that person does not suffer a serious allergic reaction to the antivenom, his own immune system can destroy the antivenin before the antivenin can destroy the venom. Though most people never require even one treatment of antivenin in their lifetime, let alone several, people who work with snakes or other venomous animals may. Fortunately, these people may develop antibodies of their own against the venom of whatever animals they handle, and thereby are protected without the assistance of exogenous antibodies.

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