''Loxosceles gaucho'' commonly known in English as the gaucho spider. is a highly venomous

recluse spider 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 ...

endemic to South America.

Description and behavior

Adult females grow up to 7–12 mm, the maximum reported is 14 mm. They are mainly characterized by their brown color, leading to them be colloquially referred to as ''''Aranha marrom'''' (Portuguese for brown spider) in Brazil, the body is characterized by a pale to dark brown color (often reddish), with a dorsal violin-shaped mark, slightly darker on the carapace, with long and slender legs, without dark marks or stripes. Males have the thoracic region with the clearest impression, consisting of bands, with the anterior portion of the cephalothorax forming in the rear direction a '' V '' design, while pedipalps have the last short articles and curved stylus. Females have the anterior portion of the cephalothorax forming a '' U '' shape backwards. Like many recluse spiders, It is

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

, hunting preys such as insects and

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s with their strong webs, and is more active in the hottest seasons of the year.

Range and habitat

They usually spin irregular webs in cracks, crevices and corners (which is why some people call them the corner spider), along or under large rocks. It often can be found in human's houses, in dark places, like clothes, shoes, socks and other parts of the house, this species mainly occurs in Central and

Southern Brazil The South Region of Brazil (; ) is one of the five regions of Brazil. It includes the states of Paraná, Rio Grande do Sul, and Santa Catarina, and covers , being the smallest region of the country, occupying only about 6.76% of the territory ...

, but have been introduced to

Tunisia ) , image_map = Tunisia location (orthographic projection).svg , map_caption = Location of Tunisia in northern Africa , image_map2 = , capital = Tunis , largest_city = capital , ...

Medical significance

One study of 81 cases of

cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...

and cutaneous-hemolytic loxoscelism, from a geographical area where most accidents are caused by ''L. gaucho'', reported bite-related symptoms such as massive

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 o ...

and acute kidney injury (in two cases). In 25 cases, an increase in serum

bilirubin Bilirubin (BR) (Latin for "red bile") is a red-orange compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the ...

and LDH was observed, suggestive of hemolysis.

anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...

(14.7%),

reticulocytosis Reticulocytosis is a condition where there is an increase in reticulocytes, immature red blood cells. It is commonly seen in anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry ...

(56%),

thrombocytopenia Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients an ...

(17.6%), an increase in

D-dimer D-dimer (or D dimer) is a fibrin degradation product (or FDP), a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis. It is so named because it contains two D fragments of the fibrin protein joined by a cross ...

and

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

were also reported. A study with the venom of ''L. gaucho'' showed the main local bite reactions, such as pain, edema,

erythema Erythema (from the Greek , meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not assoc ...

ecchymosis A bruise, also known as a contusion, is a type of hematoma of tissue, the most common cause being capillaries damaged by trauma, causing localized bleeding that extravasates into the surrounding interstitial tissues. Most bruises occur close e ...

, pallor and dermonecrosis, and systemic like Hemolysis. In the state of São Paulo alone, Brazil, it is responsible for causing viscerocutaneous loxoscelism in 3.1% of cases.

References

{{Taxonbar, from=Q2461127 Spiders of Brazil Spiders described in 1832 Sicariidae