Sicariidae
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The spider family Sicariidae is a family of venomous spiders known for their necrotic venom. The members of this family are unusual in that they have only six eyes, rather than eight (as is the norm for spider). The family consists of two genera, Loxosceles and Sicarius, and 122 species http://research.amnh.org/entomology/spiders/catalog/COUNTS.html World Spider Catalog. Well known spiders in this family include the brown recluse spider and the six-eyed sand spider.
Habitat and appearance
The genus Loxosceles, commonly known as recluse spiders or violin spiders, is distributed nearly worldwide in warmer areas, and are often known as violin spiders. The genus Sicarius, or six-eyed crab spiders, are desert spiders that live in the Southern Hemisphere, in (South America and Africa), known primarily for their self-burying behavior. All have six eyes arranged in three groups of two (diads) and the violin spiders are usually brownish with a darker brown characteristic violin marking on the cephalothorax. Sicarius resembles the crab spiders of the family Thomisidae and lacks this marking. Individual Sicarius can live for as much as 15 years, which makes these among the longest-lived araneomorphae spiders (some tarantulas can live well over 20-30 years.) 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.
Medical significance
Both genera have potent tissue-destroying venoms containing the dermonecrotic agent, sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. Thus, the venom of Sicariidae is highly necrotic in effect, capable of causing lesions (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 get infected there can be serious consequences. Rarely, the venom is carried by the blood stream to internal organs causing systemic effects. The Chilean recluse (Loxosceles laeta), along with the African species of Sicarius, reportedly have a more potent venom, which results in systemic involvement more often. http://www.lclark.edu/~binford/SMDDistribution%20copy.pdf Greta J. Binford and 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
Genera
- Loxosceles Heineken & Lowe, 1832 (worldwide)
- Sicarius Walckenaer, 1847 (South America, Africa, Galapagos)
See also
Notes
External links
- [Arachnology Home Pages: Loxosceles: Recluse spiders]
- [Biodiversity Explorer: Family Sicariidae] (Beautiful photos of Sicarius and Loxosceles!)
- [Platnick, N.I. 2003. World Spider Catalog.]
- [Vetter, R. 2003. Causes of Necrotic Wounds other than Brown Recluse Spider Bites.]
- [Vetter, R. 2003. Myth of the Brown Recluse Fact, Fear, and Loathing.]
- [Pictures of the Brown Recluse Spider]
See also
For pictures of many kinds of spiders, see [List of images/Nature/Animals/SpidersThe Spider Gallery]
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