''Hexophthalma'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s in the family

Sicariidae Sicariidae is a family of six-eyed venomous spiders known for their potentially necrotic bites. The family consists of three genera and about 160 species. Well known spiders in this family include the brown recluse spider and the six-eyed sand ...

. 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 2017, when it was discovered that the African species then placed in ''Sicarius'' were distinct. The English name six-eyed sand spiders is used for members of the genus, particularly ''

Hexophthalma hahni ''Hexophthalma hahni'' ( synonyms ''Sicarius hahni'' and ''Sicarius testaceus''), known along with other members of the genus as the six-eyed sand spider, is a member of the family Sicariidae, found in deserts and other sandy places in southern ...

''. Species in the genus have

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 ...

(dermonecrotic) venom, and can potentially cause serious or even life-threatening wounds.

Taxonomy

The genus was first created in 1878 by

Friedrich Karsch Ferdinand Anton Franz Karsch or Karsch-Haack (2 September 1853, in Münster – 20 December 1936, in Berlin) was a German arachnologist, entomologist and anthropologist. The son of a doctor, Karsch was educated at the Friedrich Wilhelm Unive ...

as ''Hexomma'', with the sole species '' Hexomma hahni''. By 1879, though, Karsch had realized that this name had already been used in 1877 for a species of

harvestman The Opiliones (formerly Phalangida) are an order of arachnids colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs. , over 6,650 species of harvestmen have been discovered worldwide, although the total number of ext ...

, so he published the

replacement name In biological nomenclature, a ''nomen novum'' (Latin for "new name"), new replacement name (or replacement name, new substitute name, substitute name) is a scientific name that is created specifically to replace another scientific name, but only w ...

''Hexophthalma''. In 1893,

Eugène Simon Eugène Louis Simon (; 30 April 1848 – 17 November 1924) was a French naturalist who worked particularly on insects and spiders, but also on birds and plants. He is by far the most prolific spider taxonomist in history, describing over 4, ...

transferred ''Hexophthalma hahni'' to the genus '' Sicarius'', and ''Hexophthalma'' fell out of use, until a phylogenetic study in 2017 showed that the African species of ''Sicarius'', including ''Sicarius hahni'', were distinct, and revived the genus ''Hexophthalma'' for them. ''Hexophthalma'' is one of three genera in the family

, . It is placed in the same subfamily, Sicariinae, as ''Sicarius'':

Species

Two new species were added to the genus in 2018, and one previously accepted species, ''H. testacea'', was synonymized with ''H. hahnii''. The number of species is expected to increase with further study. ''H. spatulata'' differs in a number of respects from other species in the genus, which thus may not be

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. , 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 ...

accepted these extant species: *'' Hexophthalma albospinosa'' (Purcell, 1908) – Namibia, South Africa *'' Hexophthalma binfordae'' Lotz, 2018 – Namibia *'' Hexophthalma damarensis'' (Lawrence, 1928) – Namibia *'' Hexophthalma dolichocephala'' (Lawrence, 1928) – Namibia *'' Hexophthalma goanikontesensis'' Lotz, 2018 – Namibia *''

'' (Karsch, 1878) (

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

) – Namibia, South Africa *'' Hexophthalma leroyi'' Lotz, 2018 – South Africa *'' Hexophthalma spatulata'' (Pocock, 1900) – South Africa

Venom

Species of ''Hexophthalma'' produce venom that can have

(dermonecrotic) effects, capable of causing serious or even life-threatening wounds, particularly if the wound becomes infected or the venom spreads in the body. The necrotic effects are caused by a family of proteins related to

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 ...

, present in the venom of all sicariid spiders. In this respect, the genus resembles ''

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 ...

'', the recluse spiders. However, most ''Hexophthalama'' species have only been studied ''in vitro'', and the detailed effects of their venom in humans and other vertebrates are unknown. One case was officially confirmed in South America in 1992, in a 17-year-old who developed a dermonecrotic lesion. There are two suspected cases in Africa, for which the spider has not been identified; however, according to the victim's description, the culprit could be '' Hexophthalma spatulata''. One of the two victims lost his arm due to extensive tissue necrosis.

References

External links

* – includes southern African ''Sicarius'', now ''Hexophthalma'' {{taxonbar, from=Q29042843 Sicariidae Araneomorphae genera