Chilean recluse

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)
Synonyms
Scytodes laeta Scytodes rufipes Scytodes nigella Omosita bicolor Loxosceles similis Loxosceles longipalpis Loxosceles nesophila Loxosceles yura Loxosceles rufipes

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 "corner spider"; 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.

Description and habitat

The Chilean recluse is one of the larger species of recluse spiders, generally ranging from 8–40 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. Most spiders have eight eyes, but 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 in Chile, and can be found throughout South America), and can now be found worldwide, including in 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 builds 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 human dwellings. The spiders can last a long time without food or water,^[3] a fact that encourages their worldwide spread.

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 sicariid 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 that of other sicariid 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 clinical 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.^{[citation needed]}

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 captured, the spider should be brought with the patient in a clear, tightly closed container for identification. However, by the time the bite is noticed any spider found nearby is not likely to be the culprit.

References

1. ^ Willis John Gertsch (1967). "The spider genus Loxosceles in South America (Araneae: Scytodidae)" (PDF). Bulletin of the American Museum of Natural History 136 (3): 119–183. http://digitallibrary.amnh.org/dspace/bitstream/2246/1989/1/B136a03.pdf. 
2. ^ Willis John Gertsch & Franklin Ennik (1983). "The spider genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae)" (PDF). Bulletin of the American Museum of Natural History 175: 264–360. http://digitallibrary.amnh.org/dspace/bitstream/2246/981/1/B175a03.pdf. 
3. ^ D. C. Lowrie (1983). "Starvation longevity of Loxosceles laeta (Nicolet) (Araneae)". Entomology News 91 (4): 130–132. 
4. ^ Greta J. Binford & Michael A. Wells (2003). "The phylogenetic distribution of sphingomyelinase D activity in venoms of haplogyne spiders" (PDF). Comparative Biochemistry and Physiology Part B 135: 25–33. http://www.lclark.edu/~binford/SMDDistribution%20copy.pdf. 
5. ^ H. Schenone, T. Saavedra, A. Rojas & F. Villarroel (1989). "Loxoscelism in Chile. Epidemiologic, clinical and experimental studies". Revista do Instituto de Medicina Tropical de São Paulo 31: 403–415. PMID 2577020. 

Further reading

Arthropods portal

• Ulisses Marion Sezerino, Marlene Zannin, Luciano Kowlaski Coelho, João Gonçalves Jr., Margareth Grando, Suely Grossemann Mattosinho, João Luiz Costa Cardoso, Vera Regina von Eickstedt, Francisco Oscar Siqueira França, Kátia Cristina Barbaro & Hui Wen Fan (1998). "A clinical and epidemiological study of Loxosceles spider envenoming in Santa Catarina, Brazil". Transactions of the Royal Society of Tropical Medicine and Hygiene 92 (5): 546–548. PMID 9861376. 
• Norman I. Platnick (2007). "The World Spider Catalog, version 8.0". American Museum of Natural History. http://research.amnh.org/entomology/spiders/catalog/index.html. Retrieved April 12, 2011. 

External links

• Brown Recluse Spider Bites
• Alejandro Palma, "Loxoscelismo" Universidad de Concepción (in Spanish, contains graphic images)