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==Venom components and effects==
==Venom components and effects==


''Loxosceles'' spiders, like their cousins in ''[[Sicarius (spider)|Sicarius]]'', have potent [[cytotoxic|tissue-destroying]] [[venom (poison)|venoms]] containing the dermonecrotic agent, '''sphingomyelinase D''', which is otherwise found only in a few pathogenic bacteria. This venom is highly [[necrotic]] in effect, capable of causing [[lesion]]s (open sores) as large as a US quarter. The wounds take a long time to heal and may require skin grafts. If these open wounds become infected there are often serious consequences. Rarely, the venom is carried by the blood stream to internal organs causing systemic effects.
''Loxosceles'' spiders, like their cousins in ''[[Sicarius (spider)|Sicarius]]'', have potent [[cytotoxic|tissue-destroying]] [[venom (poison)|venoms]] containing the dermonecrotic agent, '''sphingomyelinase D''', which is otherwise found only in a few pathogenic bacteria. This venom is highly [[necrotic]] in effect, capable of causing [[lesion]]s (open sores) as large as a bottle cap. The wounds take a long time to heal and may require skin grafts. If these open wounds become infected there are often serious consequences. Rarely, the venom is carried by the blood stream to internal organs causing systemic effects.


The [[Chilean recluse]] (''Loxosceles laeta'') supposedly has a more potent venom, which results in systemic involvement more often. This spider was accidentally introduced to the [[Los Angeles]] area ([[Alhambra, California|Alhambra]], [[Sierra Madre, California|Sierra Madre]], and [[Monterey Park, California|Monterey Park]]). This spider, however, seems to be confined to a very limited area, even though it has lived there for over 30 years. Other members of the genus that have been tested have venoms similar to the brown recluse and all members of this genus are best avoided. However, the brown recluse and its relatives are not very aggressive and huge populations have been found in houses where the human inhabitants remained unbitten after years of cohabitation.<ref name="JMedEntomol2002-Vetter">{{cite journal | author = Vetter R, Barger D | title = An infestation of 2,055 brown recluse spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas | journal = J Med Entomol | volume = 39 | issue = 6 | pages = 948–51 | year = 2002 | pmid = }}</ref>
The [[Chilean recluse]] (''Loxosceles laeta'') supposedly has a more potent venom, which results in systemic involvement more often. This spider was accidentally introduced to the [[Los Angeles]] area ([[Alhambra, California|Alhambra]], [[Sierra Madre, California|Sierra Madre]], and [[Monterey Park, California|Monterey Park]]). This spider, however, seems to be confined to a very limited area, even though it has lived there for over 30 years. Other members of the genus that have been tested have venoms similar to the brown recluse and all members of this genus are best avoided. However, the brown recluse and its relatives are not very aggressive and huge populations have been found in houses where the human inhabitants remained unbitten after years of cohabitation.<ref name="JMedEntomol2002-Vetter">{{cite journal | author = Vetter R, Barger D | title = An infestation of 2,055 brown recluse spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas | journal = J Med Entomol | volume = 39 | issue = 6 | pages = 948–51 | year = 2002 | pmid = }}</ref>

Revision as of 16:30, 13 February 2009

Recluse spiders
File:Aranhamarrom.jpg
Loxosceles amazonica spider
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Arachnida
Order:
Araneae
Family:
Sicariidae
Genus:
Loxosceles

Heineken & Lowe, 1832
Species

see article

Diversity
100 species

The recluse spiders (genus Loxosceles), also known as fiddle-back or violin spiders, are a venomous genus of spiders known for their necrotic bite. They are members of the family Sicariidae, having formerly been placed in their own family, "Loxoscelidae".

Habitat and appearance

Loxosceles is distributed nearly worldwide in warmer areas, and are often known as violin spiders or fiddlebacks. All have six eyes arranged in three groups of two (dyads) and are usually brownish with a darker brown characteristic violin marking on the cephalothorax. Most Loxosceles can live for one and a half to two years. Members of both genera can live for very long times without food or water.

The recluse spider family includes about 13 species in the United States, the brown recluse spider (Loxosceles reclusa) being the best known of these. It is found in a large area of the Midwest, west to Colorado and the New Mexico state line and east to Northern Georgia. Sporadic records from other locations only represent incidental introductions, not established populations.

Other notable members of this genus include the Chilean recluse (L. laeta) and the Mediterranean recluse (Loxosceles rufescens).

Venom components and effects

Loxosceles spiders, like their cousins in Sicarius, have potent tissue-destroying venoms containing the dermonecrotic agent, sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. This venom is highly necrotic in effect, capable of causing lesions (open sores) as large as a bottle cap. The wounds take a long time to heal and may require skin grafts. If these open wounds become infected there are often serious consequences. Rarely, the venom is carried by the blood stream to internal organs causing systemic effects.

The Chilean recluse (Loxosceles laeta) supposedly has a more potent venom, which results in systemic involvement more often. This spider was accidentally introduced to the Los Angeles area (Alhambra, Sierra Madre, and Monterey Park). This spider, however, seems to be confined to a very limited area, even though it has lived there for over 30 years. Other members of the genus that have been tested have venoms similar to the brown recluse and all members of this genus are best avoided. However, the brown recluse and its relatives are not very aggressive and huge populations have been found in houses where the human inhabitants remained unbitten after years of cohabitation.[1]

A possible problem with diagnosing a recluse spider bite is that the bite of these spiders is probably both underreported in some areas and over reported generally.[2] Unfortunately several diseases can mimic the lesions of a recluse spider bite, including Lyme disease, various fungal and bacterial infections and the first sore of syphilis([1]). Therefore it is extremely important to associate the spider directly with the bite, if at all possible, and consider alternative diagnoses if no spider was seen.

Recluse spiders are usually found in the center of space webs made of fungus-like silk, which often contains the remains of their recent meals. The most abundant food items for the Arizona recluse (Loxosceles arizonica) are night-active ants such as carpenter ants. The brown recluse feeds on whatever small prey is available. This is also true of all sicariids. Loxosceles reclusa have been shown in laboratory experiments to prefer scavenging than actively hunting.[3]

Species

See also

Footnotes

  1. ^ Vetter R, Barger D (2002). "An infestation of 2,055 brown recluse spiders (Araneae: Sicariidae) and no envenomations in a Kansas home: implications for bite diagnoses in nonendemic areas". J Med Entomol. 39 (6): 948–51.
  2. ^ Vetter R, Bush S (2002). "The diagnosis of brown recluse spider bite is overused for dermonecrotic wounds of uncertain etiology". Ann Emerg Med. 39 (5): 544–6. doi:10.1067/mem.2002.123594.
  3. ^ Sandidge J (2003). "Arachnology: Scavenging by brown recluse spiders". Nature. 426 (30). doi:10.1038/426030a.
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