Chilean recluse

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Chilean recluse spider

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Family:	Sicariidae
Genus:	Loxosceles
Species:	L. laeta

Binomial name

Loxosceles laeta
(Nicolet, 1849)

The Chilean recluse spider is a venomous spider, Loxosceles laeta, of the family Sicariidae (formerly of the family Loxoscelidae). In Spanish, it (and other South American recluse spiders) is known as araña de rincón, or "spider of the corner"; in Portuguese, as Aranha-marrom or "brown spider". This spider is considered by many to be the most dangerous of the recluse spiders, and its bite is known to frequently result in severe systemic reactions, including death.

1 Description and habitat
2 Medical significance
3 Notes
4 External links

[edit] Description and habitat

The Chilean recluse is one of the larger species of recluse spiders, generally ranging from 8-30 mm in size (including legs). Like most recluses, it is brown and usually has markings on the dorsal side of its thorax, with a black line coming from it that looks like a violin with the neck of the violin pointing to the rear of the spider resulting in the nickname "fiddleback spider" or "violin spider" in English-speaking areas. Coloring varies from light tan to brown and the violin marking may not be visible. Since the "violin pattern" is not diagnostic, it is far more important, for purposes of identification, to examine the eyes. Contrary to most spiders, which have 8 eyes, recluse spiders have 6 eyes arranged in pairs (dyads) with one median pair and 2 lateral pairs.

The Chilean recluse spider is native to South America (it is common Chile, but is found throughout South America), but is found in many places worldwide, including the North and Central America, Finland, and Australia. The spider is known to have established itself in the Los Angeles area, and infestations have been reported in Vancouver, British Columbia, Cambridge, Massachusetts, and Florida.^[1]^[2]

Like other recluse spiders, the Chilean recluse build irregular webs that frequently include a shelter consisting of disorderly threads. Unlike most web weavers, they leave these webs at night to hunt. People get bitten when they unintentionally squeeze them in clothing and bedding. These spiders frequently build their webs in woodpiles and sheds, closets, garages, and other places that are dry and generally undisturbed. The spider frequently is found in dwellings, in parts of its range where humans are found. The spiders can last a long time without food or water ^[3], a fact which encourages their worldwide distribution.

[edit] Medical significance

As indicated by its name, this spider is not aggressive and usually bites only when pressed against human skin, such as when putting on an article of clothing. Like all Sicariidae spiders, the venom of the Chilean recluse contains the dermonecrotic agent, sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. According to one study, the venom of the Chilean recluse (along with the six-eyed sand spider), contains an order of magnitude more of this substance than do other Sicariidae spiders such as the brown recluse^[4].

Some bites are minor with no necrosis, but a small number produce severe dermonecrotic lesions (cutaneous loxoscelism) or even systemic conditions (viscerocutaneous loxoscelism); sometimes resulting in renal failure and in 3-4% of cases in a recent clinincal study in Chile, death. ^[5] (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)

The serious bites form a necrotising ulcer that destroys soft tissue and may take months and very rarely years to heal, leaving deep scars. The damaged tissue will become gangrenous and eventually slough away. Initially there may be no pain from a bite, but over time the wound may grow to as large as 10 inches (25 cm) in extreme cases. Bites may take up to seven hours to cause visible damage; more serious systemic effects may occur before this time, as venom of any kind spreads throughout the body in minutes. Deaths have been reported for the related South American species L. intermedia. A longstanding medical condition known by travellers and residents to Chile, the gangrenous spot of Chile, is now believed to be caused by recluse spider bites.

First aid involves the application of an ice pack to control inflammation, the application of aloe vera to soothe and help control the pain, and prompt medical care. If it can be easily captured, the spider should be brought with the patient in a clear, tightly closed container so it may be identified. However, by the time the bite is noticed any spider found nearby is not likely to be the culprit.

[edit] Notes

^ Gertsch WJ. The spider genus Loxosceles in South America (Araneae: Scytodidae). Bulletin of American Museum of Natural History 136:119-183, 1967.
^ Gertsch WJ, Ennik F. The spider genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae). Bulletin of American Museum of Natural History 175: 264-360, 1983.
^ Lowrie DC. Starvation longevity of Loxosceles laeta (Nicolet) (Araneae). Entomology News 91: 130-132, 1980.
^ http://www.lclark.edu/~binford/SMDDistribution%20copy.pdf Greta J. Binford abd Michael A. Wells, "The phylogenetic distribution of sphingomyelinase D activity in venoms of Haplogyne spiders", Comparative Biochemistry and Physiology Part B 135 (2003) 25–33
^ http://bases.bireme.br/cgi-bin/wxislind.exe/iah/online/?IsisScript=iah/iah.xis&nextAction=lnk&base=MEDLINE_1966-1995&exprSearch=2577020&indexSearch=UI&lang=i Schenone H, Saavedra T, Rojas A, Villarroel F. "Loxoscelism in Chile. Epidemiologic, clinical and experimental studies". Revista do Instituto de Medicina Tropical de São Paulo 31:403-415, 1989