Venom

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This article is about the class of biotoxins. For other uses, see Venom (disambiguation).
Image:Waspstinger1658-2.jpg
Wasp sting, with droplet of venom

Venom or zootoxin (literally, animal poison) is any of a variety of toxins used by several groups of animal species, for the purpose of defense and hunting prey. Though subjective, the definition of a venom differs from a poison (as used in most zoology and medicine texts). Generally, a venom is defined as a biologic toxin that is injected to cause its effect while a poison is a biologic toxin which is absorbed through epithelial linings (either of the gut or through the skin).

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 is a modified egg-laying device - the ovipositor). There are also many caterpillars that have defensive venom glands associated with specialized bristles on the body, known as urticating hairs, some of which can be lethal to humans (e.g., the Lonomia moth). Venom is also found in other reptiles besides snakes such as the gila monster, and mexican beaded lizard. Other insects, such as true bugs [1], also produce venom. However, venom can also be found in some fish, such as the cartilaginous fishes: stingrays, sharks, and chimaeras and the teleost fishes, which include: 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. Additionally, there are many other venomous animals, including jellyfishes, cone snails, bees, wasps, ants, solenodons, shrews, the slow loris, and the male platypus. The Box jellyfish is widely considered the most venomous creature in the world.[2]

Bees use an acidic venom (apitoxin) designed to cause pain to the stung, because their purpose is to defend their home and food stores, while wasps use a chemically different venom designed to paralyze the 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.

It is important to note the difference between "venomous" and "poisonous", which are two commonly confused terms with regards to plant and animal life. Venomous, as stated above, refers to animals who inject venom into their prey or as a self-defence mechanism while the organism is still alive. Poisonous, on the other hand, refers to plants or animals that are harmful when consumed or touched. One bird species the hooded pitohui, although not venomous, is poisonous, secreting a neurotoxin on to 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.

[edit] Snake venom

Main article: Snake venom

Snake venom is produced by glands below the eye and delivered to the victim through tubular or channelled fangs. Snake poisons contain a variety of peptide toxins. Snakes use their venom principally for hunting, though the threat of being bitten is used for defense. Snake bites cause a variety of symptoms including pain, swelling, tissue damage, low blood pressure, convulsions, and hemorrhaging (varying by the species of snake).

Antivenin is used in the treatment of venomous bites. It is created by injecting a small amount of the targeted venom into an animal such as a sheep, horse, goat, or rabbit; the subject animal will suffer an immune response to the venom, producing antibodies against the venom's active molecule which can then be harvested from the animal's blood and used to treat envenomation in others. This treatment may only be used on a given person a certain number of times, however, as that person will develop their own antibodies against the foreign animal antibodies injected into them. Even if that person doesn't have a serious allergic reaction to the antivenin, his or her own immune system can destroy the antivenin before the antivenin can destroy the venom. Though most people never require one treatment of antivenin in their lifetime, let alone several, people who work with snakes or other venomous animals may. Luckily, these people often develop enough antibodies of their own against the venom of whatever animals they handle to become immune themselves, without needing the help of non-human antibodies.

[edit] See also

[edit] References

1. Wm. 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.

2. http://en.wikipedia.org/wiki/Box_jellyfishfr:Venom he:ארס (רעל) id:Bisa pl:Jad

Venom

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