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About|the class of biotoxin sCitations missing|date=February 2008Expert-subject|date=March 2011 Venom is the general term referring to any variety of toxin sDorlandsDict|eight/000115553|venom used by certain types of animal s that inject it into their victims by the means of a bite, sting or other sharp body feature.cite web |url= http://www.merriam-webster.com/dictionary/venom |title=venom - Definition from the Merriam-Webster Online Dictionary |format= |work= |accessdate=2008-12-13 Unlike poison , which is ingested or inhaled, administration of venom is usually directed into the lymphatic system itself for faster action.
Diversity
Invertebrates
Among animals using venom are spider (animal)|spiders (see spider bite ) 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).
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. Other insects, such as Hemiptera|true bug s and many ants also produce venom. At least one ant species ( Polyrhachis dives ) has been shown to use venom topically for the sterilisation of pathogens.cite journal|last=Graystock|first=Peter|coauthors=Hughes, William O. H.|title=Disease resistance in a weaver ant, Polyrhachis dives, and the role of antibiotic-producing glands|journal=Behavioral Ecology and Sociobiology|date=2011|doi=10.1007/s00265-011-1242-y
There are many other venomous invertebrates, including jellyfish and cone snails . The Box_jellyfish#Treatment_of_stings|box jellyfish is the most venomous jellyfish in the world.
Fish
main|Venomous fishVenom 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 waspfish es, scorpionfish es and Pterois|lionfish es, gurnard (disambiguation)|gurnard s, rabbitfishes , surgeonfish es, Scatophagidae|scats , stargazers , weever , swarmfish .
Snakes and other reptiles
main|Snake venomThe reptiles most known to use venom are snake s, some species of which inject venom into their prey via tooth|fang s.
Snake venom is produced by glands below the eye (the mandibular gland ) and delivered to the victim through tubular or channeled fangs. Snake venoms contain a variety of peptide toxins, including Proteases , which hydrolysis|hydrolyze protein peptide bonds, nucleases , which hydrolyze the phosphodiester bonds of DNA , and neurotoxins, which disable signalling in the nervous system. Snakes use their venom principally for hunting, though they do not hesitate to employ it defensively. Venomous snake bites may cause a variety of symptoms, including pain, swelling, tissue necrosis, low blood pressure, convulsions, hemorrhage (varying by species of snake), respiratory paralysis, kidney failure, coma and death.
The Gila Monster ( Heloderma suspectum ) and the beaded lizard ( Heloderma horridum ) are also known to be venomous.
Prophylaxis
Doctors treat victims of a venomous bite with antivenom , 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 molecules; the antibodies can then be harvested from the animal's blood and injected into bite victims to treat envenomation. This treatment can be used effectively only a limited number of times for a given individual, however, as a bite victim will ultimately develop antibodies to neutralize the foreign animal antigens injected into them as components of the antivenin. This is called sensitization. Even if a bite victim does not suffer a serious allergic reaction to the antivenom, his own, sensitized, immune system may destroy the antivenom before the antivenom can destroy the venom. Though most individuals never require even one treatment of anti-venom in their lifetime, let alone several, those routinely exposed to snakes or other venomous animals may become sensitized to antivenom due to previous exposure.
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|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.
Other reptiles
Aside from snakes, venom is found in a few other reptiles such as the Mexican beaded lizard and Gila monster ,and may be present in a few species of monitor lizard s.
One such reptile that was previously thought of as being nonvenomous is the Komodo Dragon , Varanus komodoensis . It was then demonstrated through magnetic resonance imaging that the Komodo Dragon possess a mandibular gland with a major posterior compartment and 5 smaller anterior compartments.Bryan G. Fry, Stephen Wroec, Wouter Teeuwissed, et al., (University of Melbourne): PNAS, publisched online, DOI|10.1073/pnas.0810883106, A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus ( Megalania ) priscus' The scientists used mass spectrometry to show that the mixture of proteins present in the venom was as complex as the proteins found in snake venom.Fry, B. G., W. Wuster, S. F. R. Ramjan, T. Jackson, P. Martelli, and R. M. Kini. 2003c. Analysis of Colubroidea snake venoms by liquid chromatography with mass spectrometry: Evolutionary and toxinological implications. Rapid Communications in Mass Spectrometry 17:2047-2062.
Due to these recent studies investigating venom glands in squamates , lizards that were previously thought of as being nonvenomous are now being classified by some scientists as venomous because they possess a venom gland. This hypothetical clade, Toxicofera , includes all venomous squamates: the suborders Serpentes and Iguania and the families Varanidae , Anguidae , and Helodermatidae .cite journal|author = Fry, B. et al.|year= 2006 |month= February|title= Early evolution of the venom system in lizards and snakes|journal= Nature|volume= 439|pages= 584–588|url= http://www.nature.com/nature/journal/v439/n7076/abs/nature04328.html|doi = 10.1038/nature04328|format = http://www.naherpetology.org/pdf_files/467.pdf PDF|pmid = 16292255|last1 = Fry|first1 = BG|last2 = Vidal|first2 = N|last3 = Norman|first3 = JA|last4 = Vonk|first4 = FJ|last5 = Scheib|first5 = H|last6 = Ramjan|first6 = SF|last7 = Kuruppu|first7 = S|last8 = Fung|first8 = K|last9 = Hedges|first9 = SB|issue = 7076|issn = 0028-0836
Mammals
main|Venomous mammalsSome mammals are also venomous, including solenodon s, shrews , the slow loris , and the male platypus .
Amphibians
There are only a few species of venomous amphibians; certain salamandridae|salamandrid salamanders can extrude sharp venom-tipped ribs. http://www.askabiologist.org.uk/punbb/viewtopic.php? id=1494Cite doi | 10.2307/1443606
Dinosaurs
Sinornithosaurus , a genus of feathered dromaeosauridae|dromaeosaurid dinosaur, may have had a venomous bite. This hypothesis is still being disputed. The theropoda|theropod Dilophosaurus is commonly depicted in popular culture as being venomous, but this portrayal is not considered likely by the scientific community.
Therapsida
Euchambersia a genus of Therocephalia (animals close to the evolution of mammals) is known to have had venom glands attached to its canine teeth, used to help subdue and kill its prey. The potency of its venom is unknown.
See also
Envenomation
Schmidt Sting Pain Index
Big Four (Indian snakes)
List of venomous animals
References
reflist
Bibliography
cite journal |author=Smith WL, Wheeler WC |title=Venom evolution widespread in fishes: a phylogenetic road map for the bioprospecting of piscine venoms |journal=J. Hered. |volume=97 |issue=3 |pages=206–17 |year=2006 |pmid=16740627 |doi=10.1093/jhered/esj034 |url= http://jhered.oxfordjournals.org/cgi/pmidlookup? view=long& pmid=16740627
cite journal |author=Lans C, Harper T, Georges K, Bridgewater E |title=Medicinal and ethnoveterinary remedies of hunters in Trinidad |journal=BMC Complement Altern Med |volume=1|pages=10 |year=2001 |pmid=11737880 |pmc=60997 |doi= 10.1186/1472-6882-1-10|url= http://www.biomedcentral.com/1472-6882/1/10
Fry, B. G., N. Vidal, J. A. Norman, F. J. Vonk, H. Scheib, S. F. R. Ramjan, S. Kuruppu, K. Fung, S. B. Hedges, M. K. Richardson, W. C. Hodgson, V. Ignjatovic, R. Summerhayes, and E. Kochva. 2006. Early evolution of the venom system in lizards and snakes. Nature (London) 439:584-588.
Fry, B. G., S. Wroe, W. Teeuwisse, M. J. P. van Osch, K. Moreno, J. Ingle, C. McHenry, T. Ferrara, P. Clausen, H. Scheib, K. L. Winter, L. Greisman, K. Roelants, L. van der Weerd, C. J. Clemente, E. Giannakis, W. C. Hodgson, S. Luz, P. Martelli, K. Krishnasamy, E. Kochva, H. F. Kwok, D. Scanlon, J. Karas, D. M. Citron, E. J. C. Goldstein, J. E. Mcnaughtan, and J. A. Norman. 2009b. A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus. Proceedings of the National Academy of Sciences of the United States of America 106:8969-8974.
Fry, B. G., W. Wuster, S. F. R. Ramjan, T. Jackson, P. Martelli, and R. M. Kini. 2003c. Analysis of Colubroidea snake venoms by liquid chromatography with mass spectrometry: Evolutionary and toxinological implications. Rapid Communications in Mass Spectrometry 17:2047-2062.