''Sicarius ornatus'' is a species of venomous spider found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

(

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

). It has a highly toxic venom like the other South American sicariid, ''

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 the African '' Hexophthalma hahni'', but there are few human bites recorded. Its venom has active

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 ...

, and can lead to a severe pathology. The venom of ''Sicarius ornatus'' contains active sphingomyelinase D, the main toxin responsible for local and systemic effects, the venom of ''S. ornatus'' is endowed with all toxic properties in vitro and ex vivo, and like ''

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 ...

'', it is capable and hydrolyzes sphingomyelin , induce cell death of

keratinocytes Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells. Basal cells in the basal layer (''stratum basale'') of the skin are sometimes referre ...

and complement-dependent

hemolysis 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 ...

, harmful events that have been associated with the presence of active sphingomyelinase D and pathologies in vivo, these studies indicate that the venom of ''S. ornatus'' can potentially lead to a pathology similar to that of Loxosceles. Its venom can induce more than 60% of hemolysis with only 5 micrograms, while '' Sicarius tropicus'' causes 50% of hemolysis even at higher concentrations.

References

{{Taxonbar, from=Q2736501 Sicariidae Spiders of Brazil Spiders described in 2013