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Removed bogus statement " Laboratory mice subjected to ''P. nigriventer'' venom experienced intense penile erections before succumbing to the toxin" added at 10:02 on 11 October 2009‎ by 218.111.4.226.
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Aside from causing intense pain, the venom of the spider can also cause [[priapism]] in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence. A component of the venom ([[Tx2-6]]) is being studied for use in [[erectile dysfunction]] treatments.<ref>[http://www.foxnews.com/story/0,2933,269455,00.html "Natural Viagra: Brazilian Spider Bite Causes Hours-Long Erection"]. ''[[FoxNews]]'', May 1, 2007. Accessed May 6, 2007.</ref><ref>[http://www.livescience.com/4429-natural-viagra-spider-bite-erection.html Natural Viagra: Spider bite causes prolonged erection]. ''Live Science'', April 30, 2007. Accessed March 30, 2012.</ref><ref>{{cite web|author=Pat Hagan |url=http://www.dailymail.co.uk/health/article-2195208/Venom-worlds-deadliest-spider-cure-erectile-dysfunction-20-minutes.html |title=Venom from world's deadliest spider could cure erectile dysfunction within 20 minutes &#124; Mail Online |publisher=Dailymail.co.uk |date=2012-08-29 |accessdate=2012-10-16}}</ref>
Aside from causing intense pain, the venom of the spider can also cause [[priapism]] in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence. A component of the venom ([[Tx2-6]]) is being studied for use in [[erectile dysfunction]] treatments.<ref>[http://www.foxnews.com/story/0,2933,269455,00.html "Natural Viagra: Brazilian Spider Bite Causes Hours-Long Erection"]. ''[[FoxNews]]'', May 1, 2007. Accessed May 6, 2007.</ref><ref>[http://www.livescience.com/4429-natural-viagra-spider-bite-erection.html Natural Viagra: Spider bite causes prolonged erection]. ''Live Science'', April 30, 2007. Accessed March 30, 2012.</ref><ref>{{cite web|author=Pat Hagan |url=http://www.dailymail.co.uk/health/article-2195208/Venom-worlds-deadliest-spider-cure-erectile-dysfunction-20-minutes.html |title=Venom from world's deadliest spider could cure erectile dysfunction within 20 minutes &#124; Mail Online |publisher=Dailymail.co.uk |date=2012-08-29 |accessdate=2012-10-16}}</ref>


The amount of ''P. nigriventer'' venom necessary to kill a 20&nbsp;g mouse has been shown to be only 6&nbsp;μg [[Intravenous therapy|intravenously]] and 134&nbsp;μg [[Subcutaneous tissue|subcutaneously]] as compared to 110&nbsp;μg and 200&nbsp;μg respectively for ''[[Latrodectus mactans]]'' (Southern black widow). This ranks ''Phoneutria'' venom among the most deadly spider venoms to mice. Laboratory mice subjected to ''P. nigriventer'' venom experienced intense penile erections before succumbing to the toxin.<ref name="ReferenceA">Venomous Animals and their Venoms'', vol. III, ed. Wolfgang Bücherl and Eleanor Buckley</ref>
The amount of ''P. nigriventer'' venom necessary to kill a 20&nbsp;g mouse has been shown to be only 6&nbsp;μg [[Intravenous therapy|intravenously]] and 134&nbsp;μg [[Subcutaneous tissue|subcutaneously]] as compared to 110&nbsp;μg and 200&nbsp;μg respectively for ''[[Latrodectus mactans]]'' (Southern black widow). This ranks ''Phoneutria'' venom among the most deadly spider venoms to mice.<ref name="ReferenceA">Venomous Animals and their Venoms'', vol. III, ed. Wolfgang Bücherl and Eleanor Buckley</ref>


==Danger to humans==
==Danger to humans==

Revision as of 18:13, 10 January 2013

Phoneutria
Phoneutria nigriventer
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Arachnida
Order:
Araneae
Family:
Ctenidae
Genus:
Phoneutria

Perty, 1833
Type species
Phoneutria fera
Perty, 1833
Species

P. bahiensis Simó & Brescovit, 2001
P. boliviensis (F. O. Pickard-Cambridge, 1897)
P. eickstedtae Martins & Bertani, 2007
P. fera Perty, 1833
P. keyserlingi (F. O. Pickard-Cambridge], 1897)
P. nigriventer (Keyserling, 1891)
P. pertyi (F. O. Pickard-Cambridge, 1897)
P. reidyi (F. O. Pickard-Cambridge, 1897)

Diversity
8 species

Phoneutria, commonly known as Brazilian wandering spiders, armed spiders ("armadeiras", as they are known in Portuguese), or banana spiders (not to be confused with the relatively harmless Nephila), are a genus of defensive and venomous spiders of potential medical significance to humans. They are mainly found in tropical South America, with one species in Central America.[1] These spiders are members of the Ctenidae family of wandering spiders.

The Brazilian wandering spiders appear in Guinness World Records from 2010 to present as the world's most venomous spider.[2][3]

Description

The genus Phoneutria (Greek for "Murderess") contains eight scientifically described species; the most notorious being P. fera and P. nigriventer. The spiders in the genus can grow to have a leg span of 13 to 15 cm (5.1 to 5.9 in). Their body length ranges from 17 to 48 mm (0.67 to 1.89 in).[4][5] The genus is distinguished from other related genera such as Ctenus by the presence of dense prolateral scopulae (=a dense brush of fine hairs) on the pedipalp tibiae and tarsi in both sexes.[4] Phoneutria are easily confused with several other non-medically significant ctenids, especially Cupiennius, in which the recently described C. chiapanensis also has bright red hairs on the chelicerae.[6][7] Additionally, some Phoneutria species lack red hairs on the chelicerae, making it an unreliable identification feature.[7] The presence of a dark linear stripe or stripes on the frontal (=dorsal) palps and presence of a single thin black line running anterior-posterior along the dorsal carapace may help diagnose Phoneutria. Other useful features are the strong ventral marking on the underside of the legs with contrasting dark mid-segments and lighter joints, and the pattern on the ventral (underside) of the abdomen with several rows of black dots, or an overall reddish colour.[7]

The characteristic defensive posture with frontal legs held high is an especially good diagnostic to confirm Phoneutria,[4] especially alongside correct colour patterns. During the defensive display the body is lifted up into an erect position, the first two pairs of legs are lifted high (revealing the conspicuous black/light-banded pattern on the leg underside), while the spider sways from side to side with hind legs in a cocked position.[4]

Behavior

Wandering spiders are so-called because they wander the jungle floor at night, rather than residing in a lair or maintaining a web. During the day they hide inside termite mounds, under fallen logs and rocks, and in banana plants and bromeliads. P. nigriventer is known to hide in dark and moist places in or near human dwellings.

P. nigriventer mates during the dry season from April to June, which leads to frequent observations of the species during this time.[4]

Distribution

Phoneutria are found in forests from Costa Rica, and throughout South America east of the Andes into northern Argentina, including Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil and Paraguay. Three species (P. reidyi, P. boliviensis and P. fera) are found in the Amazon region, one species (P. fera) is restricted to the Amazon, and one (P. boliviensis) ranges into Central America in Panama and Costa Rica. The remaining species are restricted to Atlantic Forest of Argentina, Paraguay and Brazil, including forest fragments in the Cerrado savanna. In Brazil, Phoneutria is only absent in the northeastern region north of Salvador, Bahia.[4]

Phoneutria has been introduced to Chile and Uruguay.[4]

Species

Female of P. cf nigriventer: WARNING: This and other species of the genus Phoneutria have medically significant venom and should generally not be handled

As of early 2012, this genus contains eight species:[8]

  • Phoneutria bahiensis Simó & Brescovit, 2001 — Atlantic rainforest of Brazil.
  • Phoneutria boliviensis (F. O. Pickard-Cambridge, 1897) — Central, South America.

[Officially reported in Costa Rica, Panama, Colombia, Peru, Ecuador Bolivia]

  • Phoneutria eickstedtae Martins & Bertani, 2007 — Brazil
  • Phoneutria fera Perty, 1833 — Ecuador, Peru, Brazil, Surinam, Guyana.
  • Phoneutria keyserlingi (F. O. Pickard-Cambridge], 1897) — Atlantic rainforest of Brazil.
  • Phoneutria nigriventer (Keyserling, 1891) — Brazil, northern Argentina; introduced to Uruguay.
  • Phoneutria pertyi (F. O. Pickard-Cambridge, 1897) — Atlantic rainforest of Brazil.
  • Phoneutria reidyi (F. O. Pickard-Cambridge, 1897) — Venezuela, Peru, Brazil, Guyana.

Toxicity

P. fera and P. nigriventer are widely considered the most venomous species of spider.[2][3] Its venom contains a potent neurotoxin, known as PhTx3, which acts as a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in neural synapses. At deadly concentrations, this neurotoxin causes loss of muscle control and breathing problems, resulting in paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following a bite due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves. This sensory nerve stimulation causes a release of neuropeptides such as substance P which triggers inflammation and pain.[9]

Aside from causing intense pain, the venom of the spider can also cause priapism in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence. A component of the venom (Tx2-6) is being studied for use in erectile dysfunction treatments.[10][11][12]

The amount of P. nigriventer venom necessary to kill a 20 g mouse has been shown to be only 6 μg intravenously and 134 μg subcutaneously as compared to 110 μg and 200 μg respectively for Latrodectus mactans (Southern black widow). This ranks Phoneutria venom among the most deadly spider venoms to mice.[13]

Danger to humans

File:Banana Spider in Bundle of Bananas.jpg
A Brazilian Banana Spider found packaged with a bundle of bananas at a grocery store

Phoneutria includes some of the relatively few species of spiders known to present a threat to human beings. Danger to humans is not merely a question of toxicity, but requires the capacity to deliver the venom, a sufficient quantity of venom, a disposition that makes a bite likely and proximity to human habitation. The actual incidence of death or serious injury must also be considered.

Spider mouthparts are adapted to envenom very small prey; they are not well-adapted to attacking large mammals such as humans. A study in March 2009 suggests that Phoneutria inject venom in approximately one-third of their bites, and only a small quantity in one-third of those cases. Research in this area is hindered by the difficulty of identifying particular species. These spiders, however, almost never deliver dry bites, with 9 bites out of 10 being venomous[citation needed]. The aggressiveness of the spider is another issue, as it can bite several times in a row before fleeing.[citation needed]

Of the eight-described species, P. nigriventer and P. fera most frequently receive mention in mass-media publications. P. nigriventer is the species responsible for most cases of venom intoxication in Brazil because it is commonly found in highly populated areas of southeastern Brazil, such as the states of São Paulo, Minas Gerais, Rio de Janeiro and Espírito Santo. The species P. fera is native to the northern portion of South America in the Amazon of Brazil, Venezuela, Ecuador, Peru and the Guyanas.

The spider's wandering nature is another reason it is considered so dangerous. In densely populated areas, Phoneutria species usually search for cover and dark places to hide during daytime, leading it to hide within houses, clothes, cars, boots, boxes and log piles, thus generating accidents when people disturb it. Its other common name, "banana spider", comes from its tendency to hide in banana bunches or plantations, and it is occasionally found as a stowaway within shipments of bananas. These spiders can also appear in banana crates sent to grocery stores and bulk food centers around the world. One such instance happened in 2005 with a shipment of bananas arriving at Bridgwater, England, when a man was bitten by a P. fera; however, due to quick medical care he survived, taking nearly a week to recover from the bite following treatment.[14]

Despite their reputation as the world's deadliest spiders, there are multiple studies that call into question their capacity for fatal human envenomation, though some of these are labeled with a level of uncertainty, as Phoneutrias are often confused with other genera of ctenids or the lycosids or other large labidognatha spiders. One study suggested that only 2.3 percent of bites (mainly in children) were serious enough to require antivenom.[15] However, other studies, as cited in the Wolfgang Bücherl studies, showed that the toxicity of Phoneutria venom was clearly more virulent than both Latrodectus and Atrax. Many experts believe that various spiders like Phoneutria can deliver a "dry" bite to purposely conserve their venom, as opposed to a more primitive spider like Atrax that usually delivers a full load. Nevertheless, there are well-attested instances of death. In one case, a single spider killed two children in São Sebastião. The spider was positively identified as a Phoneutria by Wolfgang Bücherl.[13]

Footnotes

  1. ^ Valerio, C.E. (1983). "Sobre la presencia de "Phoneutria boliviensis" (F.O.P Cambridge) (Araneae: Ctenidae) en Costa Rica" (PDF). Journal of Arachnology. 11 (1): 101–102.
  2. ^ a b Several venomous species of arachnid are far more likely to attack a human, and the Guinness book of World Records actually states that although the Brazilian wandering spider is the most toxic, more deaths actually occur from black widow and brown recluse spider bites, due to the rarity of the Wandering spider actually biting anyone.[citation needed]
  3. ^ a b Herzig V, John Ward R, Ferreira dos Santos W (2002). "Intersexual variations in the venom of the Brazilian "armed" spider Phoneutria nigriventer (Keyserling, 1891)". Toxicon. 40 (10): 1399–406. doi:10.1016/S0041-0101(02)00136-8. PMID 12368110.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ a b c d e f g Martins, R. and Bertani, R. (2007). "The non-Amazonian species of the Brazilian wandering spiders of the genus Phoneutria Perty, 1833 (Araneae: Ctenidae), with the description of a new species". Zootaxa. 1526 (5): 1–36.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ Simó, M. (2001). "Revision and cladistic analysis of the Neotropical spider genus Phoneutria Perty, 1833 (Araneae, Ctenidae), with notes on related Cteninae". Bulletin British Arachnological Society. 12 (2): 67–82.
  6. ^ Medina Soriano, F. M. (2006). "A new species of Cupiennius (Araneae, Ctenidae) coexisting with Cupiennius salei in a Mexican mangrove forest" (PDF). Journal of Arachnology. 34 (2): 135–141.
  7. ^ a b c Vetter, R. & Hillebrecht, S. (2008). "On distinguishing two often-misidentified genera (Cupiennius, Phoneutria) (Araneae: Ctenidae) of large spiders found in Central and South American cargo shipments" (PDF). American Entomology. 54 (2): 88–93.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ The world spider catalog, version 12.5. American Museum of Natural History. Accessed March 30, 2012.
  9. ^ "Phoneutria nigriventer spider venom activates 5-HT4 receptors in rat-isolated vagus nerve". Nature.com. Retrieved 2012-10-16.
  10. ^ "Natural Viagra: Brazilian Spider Bite Causes Hours-Long Erection". FoxNews, May 1, 2007. Accessed May 6, 2007.
  11. ^ Natural Viagra: Spider bite causes prolonged erection. Live Science, April 30, 2007. Accessed March 30, 2012.
  12. ^ Pat Hagan (2012-08-29). "Venom from world's deadliest spider could cure erectile dysfunction within 20 minutes | Mail Online". Dailymail.co.uk. Retrieved 2012-10-16.
  13. ^ a b Venomous Animals and their Venoms, vol. III, ed. Wolfgang Bücherl and Eleanor Buckley
  14. ^ "BBC, 2005". BBC News. 2005-04-27. Retrieved 2012-10-16.
  15. ^ Bucaretchi et al., 2000
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