Sicariidae is a
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
of six-eyed
venomous spiders known for their potentially
necrotic
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
bites. The family consists of three
genera
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
and about 160
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
. Well known spiders in this family include the
brown recluse spider
The brown recluse (''Loxosceles reclusa''), Sicariidae (formerly placed in a family "Loxoscelidae") is a recluse spider with necrotic venom. Similar to those of other recluse spiders, their bites sometimes require medical attention. The brown r ...
and the
six-eyed sand spider.
Description
''
Loxosceles
The recluse spiders (''Loxosceles'' (), also known as brown spiders, fiddle-backs, violin spiders, and reapers, is a genus of spiders that was first described by R. T. Lowe in 1832. They are venomous spiders known for their bite, which sometimes ...
'', commonly known as "recluse spiders" or "violin spiders", is distributed nearly worldwide in warmer areas. ''
Hexophthalma
''Hexophthalma'' is a genus of spiders in the family Sicariidae. Although the genus was originally erected in 1878 (then with the name ''Hexomma''), it was merged into the genus '' Sicarius'' in the 1890s, and remained unused until revived in 2 ...
'' and ''
Sicarius'', commonly known as "sand spiders" or "assassin spiders", live in the
desert
A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...
s of southern
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
and
South
South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west.
Etymology
The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...
to
Central America
Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...
, respectively.
They are known for their self-burying behavior and the ability to go for long periods without food or water.
All members have six eyes arranged in three groups of two (dyads). Violin spiders are usually brownish with a darker brown characteristic violin marking on the cephalothorax. They are also
haplogyne
The Haplogynae or haplogynes are one of the two main groups into which araneomorph spiders have traditionally been divided, the other being the Entelegynae. Morphological phylogenetic studies suggested that the Haplogynae formed a clade; more recen ...
, meaning the females possessing unsclerotised genitals.
''Hexophthalma'' and ''Sicarius'' resemble
crab spiders and lack this marking. With the
tarantula
Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. , 1,040 species have been identified, with 156 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although ...
s, these are some of the longest living spiders, some living up to fifteen years old. Most ''Loxosceles'' can live for one and a half to two years.
Venom
All genera are able to produce
sphingomyelinase D
Sphingomyelin phosphodiesterase D (EC 3.1.4.41, sphingomyelinase D) is an enzyme of the sphingomyelin phosphodiesterase family with systematic name sphingomyelin ceramide-phosphohydrolase. These enzymes catalyse the hydrolysis of sphingomyelin, res ...
or a related tissue-destroying substance. It is unique to the family among spiders, and otherwise only found in a few
pathogenic bacteria
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often Probiotic, beneficial but others can cause infectious diseases. The n ...
. Bites from most of the Neotropical species of ''Sicarius'' are not known to display dermonecrotic or systemic activity, except the highly venomous ''
Sicarius ornatus
''Sicarius ornatus'' is a species of venomous spider found in South America (Brazil). It has a highly toxic venom like the other South American sicariid, ''Loxosceles laeta'' and the African '' Hexophthalma hahni'', but there are few human bites ...
'' which has active proteins of the sphingomyelinase D family found in the venom.
[ It has also recently been proven that '']Sicarius thomisoides
''Sicarius thomisoides'' is a species of spider in the family Sicariidae, found in Chile. It is the type species of the genus '' Sicarius''. Its correct name has been the source of confusion. It has often been known by the synonym ''Sicarius ter ...
'' contains active sphingomyelinase D, very similar to that of ''Loxosceles laeta
The Chilean recluse spider, ''Loxosceles laeta'', is a highly venomous spider of the family Sicariidae. In Spanish, it (and other South American recluse spiders) is known as ', or "corner spider"; in Brazilian Portuguese, as ' or "brown spider". ...
'' and ''Sicarius ornatus'', and that its bite can cause serious damage in humans, ''Sicarius tropicus
''Sicarius tropicus'' is a species of six-eyed sand spider ('' Sicarius'') endemic in South American caatinga in Brazil. Like related spiders, it is venomous, but only one medically-significant bite has been recorded, causing dermonecrotic lesio ...
'' have been also reported for having dermonecrotic and hemolytic
Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
venom
The venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
of many Sicariidae species is highly hemolytic
Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
and dermonecrotic
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
, capable of destroying red blood cells and causing lesion
A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals.
Types
There is no designated classifi ...
s as large as in diameter that take a long time to heal. Some require skin grafts and if the open wound gets infected, there can be even more serious consequences. Rarely, the venom is carried by the blood stream into internal organs causing systemic effects. Unlike spiders that use neurotoxins, many of the venoms used by these spiders do not have a known anti-venom.
Taxonomy
The family was first described by Eugen von Keyserling Eugen von Keyserling (22 March 1833 in Pockroy, Lithuania – 4 April 1889 in Dzierżoniów, Silesia) was a Baltic-German arachnologist.
He studied in the University of Tartu.
He was the author of ''Die Spinnen Amerikas'', and completed ''Die Ara ...
in 1880, and treated as a subfamily and synonym of "Loxoscelidae" in 1893, though this violates the rules of the International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the ...
; the publication of Sicariidae in 1880 predates the publication of Loxoscelidae in 1893, and the older name therefore has priority whenever the two are considered to be synonyms. The World Spider Catalog treats Loxoscelinae as a subfamily of Sicariidae, though some sources still recognize Loxoscelidae as a separate family (e.g.,).
A phylogenetic study in 2017 showed that the African species of ''Sicarius'' were distinct, and placed them in the revived genus ''Hexophthalma
''Hexophthalma'' is a genus of spiders in the family Sicariidae. Although the genus was originally erected in 1878 (then with the name ''Hexomma''), it was merged into the genus '' Sicarius'' in the 1890s, and remained unused until revived in 2 ...
''. The relationship found between the genera is shown in the following cladogram:
Genera
, the World Spider Catalog
The World Spider Catalog (WSC) is an online searchable database concerned with spider taxonomy. It aims to list all accepted families, genera and species, as well as provide access to the related taxonomic literature. The WSC began as a series of ...
accepts the following genera:
*''Hexophthalma
''Hexophthalma'' is a genus of spiders in the family Sicariidae. Although the genus was originally erected in 1878 (then with the name ''Hexomma''), it was merged into the genus '' Sicarius'' in the 1890s, and remained unused until revived in 2 ...
'' Karsch, 1879 – Namibia, South Africa
*''Loxosceles
The recluse spiders (''Loxosceles'' (), also known as brown spiders, fiddle-backs, violin spiders, and reapers, is a genus of spiders that was first described by R. T. Lowe in 1832. They are venomous spiders known for their bite, which sometimes ...
'' Heineken & Lowe, 1832 – South America, North America, Asia, Africa, Central America, Caribbean, Finland, Australia
*'' Sicarius'' Walckenaer, 1847 – South America, Central America
See also
* List of Sicariidae species
This page lists all described species of the spider family Sicariidae accepted by the World Spider Catalog :
''Hexophthalma''
''Hexophthalma'' Karsch, 1879
* '' H. albospinosa'' (Purcell, 1908) — Namibia, South Africa
* '' H. binfordae'' Lotz ...
References
External links
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*
{{Taxonbar, from=Q11717
Araneomorphae families
Taxa named by Eugen von Keyserling