Venom

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. 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), fishes (stingrays, scorpionfish, along with many others), jellyfish, mollusk (such as cone snails), and even some mammals (such as the male platypus or slow loris). Venomous fish (not to be confused with poisonous fish) are believed to far outnumber all other venomous vertebrates combined (Handwerk 2006).

value of venom...

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. In other words, toxin is a subcategory of poison, referring to a substance produced by a living organism. However, when used non-technically, the term is often 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 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.

While venom may be considered a type of poison, the term usually is ... here put the fact that venom for organisms with mechanical means, only speak of poisonous plants, but animals may be venomous or poisonous

venom is type of poison, but greater specific for those wit delivery system, and of biological nature.

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.

snake venoms are generally not dangerous when ingested, and are therefore not technically poisons.

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, 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. 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. One species of bird, the 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.

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).

The derivative forms "toxic" and "poisonous" are synonymous.

Examples

The animals most widely known to use venom are snakes, some species of which inject venom into their prey through hollow fangs; spiders and centipedes, which also inject venom through fangs; 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 (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 true bugs [1] and many ants, also produce venom. Venom can also be found in some fish, such as the cartilaginous fishes – stingrays, sharks, and chimaeras – and the teleost fishes including monognathus eels, catfishes, stonefishes and waspfishes, scorpionfishes and lionfishes, gurnard perches, rabbitfishes, surgeonfishes, scats, stargazers, weevers, carangids, saber-toothed blenny, and toadfish. In fact, recent studies have shown that there are more venomous ray-finned fishes than all other venomous vertebrates 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.[2] Some mammals are also venomous, including solenodons, shrews, the slow loris, and the male platypus.

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.

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.

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.

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.

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.

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.

Snake venom

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).

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).

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).

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.

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).^{[citation needed]} 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.

See also

• Toxin
• Poison
• Toxinology
• Schmidt Sting Pain Index
• Venomous mammals
• Venomous fish
• Big Four (Indian snakes)
• Envenomation
• Venomous animals (category)

Notes

• Freiberg, M., and J. Walls. 1984. The World of Venomous Animals. New Jersey: TFH Publications. ISBN 0876665679.

• Holland, J. S. 2008. Living color: Toxic nudibranchs—soft, seagoing slugs—produce a brilliant defense National Geographic, June 2008. Retrieved July 23, 2008.

• Klauber, L. M. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind, 2nd edition. Berkeley, CA: University of California Press. ISBN 0520210565.

• Mehrtens, J. 1987. Living Snakes of the World in Color. New York: Sterling. ISBN 0806964618.

Bibliography

• 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.
• 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

http://www.bartleby.com/68/33/6333.html Bartleby

Template:Poisoning and toxicity

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