LOXOSCHELES RECLUSA: CHARACTERISTICS, STING, EFFECTS, TREATMENT - BIOLOGY - 2025

Loxoscheles reclusa, also known as the fiddler spider or brown recluse spider, is an arachnid of the Sicariidae family that reaches up to 12 mm in length. Its body is densely covered with a short setation and its second pair of legs is longer than the other legs. Its color varies from yellowish brown to very dark reddish brown.

This spider is of sexual reproduction with internal fertilization, oviparous, the female depositing up to 50 eggs in an ootheca. After a month, the young hatch as juveniles and can take up to a year to reach sexual maturity. They can live up to one more year after they mature.

Loxoscheles recluse adult female. Taken and edited from: Insects Unlocked.

Loxoscheles reclusa is carnivorous, basically insectivorous. It catches its prey with the help of its net or by actively hunting it at night. To kill her, he injects her with a powerful poison. This toxin, in case of attacking a human being, produces a syndrome called loxoscelism, however, this species only attacks man if it feels threatened.

Loxoscelism can be cutaneous or visceral and can cause necrotic wounds to systemic damage to the body that can even lead to death.

There is an antidote against the venom of the brown recluse spider, but it must be administered in the first hours after the bite, with the aggravation that the symptoms take time to manifest.

characteristics

Apart from the characteristics of the genus Loxocheles, such as the piriform body, eyes arranged in three dyads, the presence of a violin-shaped spot on the cephalothorax, chelicerae joined by a membrane up to half their length and the shape of the sexual organs, Loxosceles reclusa has a number of specific characteristics.

Although their eyes are present in numbers of six and arranged in three pairs, the arrangement of these in the brown recluse spider is more semicircular than triangular, as is the case in most of the other species of the genus.

The adults of this species can reach 12 mm in length, with the female being larger than the male, as is characteristic of violin spiders in general.

The body color varies from pale yellowish brown to dark reddish brown, but generally tends to be light. Additionally, the body is covered by a dense short setation, while in other species of Loxosceles both short and long setae can be present, or they can be practically absent.

Taxonomy

The brown recluse spider is taxonomically located in the class Arachnida (spiders), order Areneae and the family Sicariidae, which is also called Loxoscelidae. However, due to age criteria, the name Sicariidae should prevail.

This family is made up of three genera, Sicarius, Hexophthalma and Loxoscheles, to which the brown recluse spider belongs. This last genus was described for the first time by Heineken and Lowe in 1832. In addition to Loxoscheles reclusa, it is made up of 115 other validly described species.

The Loxoscheles reclusa species was described in 1940 by American researchers Willis John Gertsch (arachnologist) and Stanley B. Mulaik (zoologist).

Reproduction

Like all other fiddler spiders, the brown recluse spider is a sexually reproducing species. The sexes are separated (dioecious) and are haplogin type, that is, the external sexual organs are absent, the genital orifice being a simple cleft covered with mushrooms.

The copulatory organs of males are simple, so the pedipalps are modified to act as secondary copulatory organs. Sperm are not free, but are packed into a structure known as a spermatophore.

The spermatophores are placed by the males in the spermathecae (sperm receptacles) of the females with the help of the pedipalps and the sperm are released as the eggs of the females mature and go down the gonducts.

A female lays between 30 and 50 eggs in a capsule or sac called an ootheca. The eggs develop during a month and youngsters hatch that must undergo six or seven molts in a period of a year to reach sexual maturity.

Females generally lay ootheca between May and July, although the reproductive season may extend from February to September in some locations.

The brown recluse spider can live for up to two years under laboratory conditions, although some researchers believe that under favorable conditions this species can actually live between 5 and 10 years.

Anterodorsal view of a brown recluse spider Loxoscheles reclusa. Taken and edited from: Insects Unlocked.

Habitat and distribution

Loxoscheles reclusa prefers warm, dry areas such as bits of tree bark, crevices between rocks, or under rocks and fallen logs. They adapt very well to anthropic environments, preferring basements, attics, garages, closets, in cracks in walls, abandoned houses and warehouses.

Although they give priority to the designated places, they take advantage of practically any small space where they can live hidden, even inside shoes, clothes, behind picture frames, between books or stacked papers, etc.

This species is native to North America, being distributed by several states of the United States and northern Mexico. This spider lives from Texas to Alabama, Ohio, Nebraska, Kansas, and Oklahoma, but is absent in California.

Feeding

Loxoscheles reclusa is carnivorous, its main food is made up of small insects, although it can also feed on other arthropods, including other spiders. The capture of their prey is done passively, waiting for them to fall into the net, or actively during hours of the night.

The net is irregular in shape, usually with a thicker and denser portion, almost tubular, in a protected place where it is hidden. The shape of the net is not very effective, but on the other hand it is very sticky when freshly made; dust causes this condition to fade over time.

When a prey falls into the net, or when he catches it on his hunting trips, he quickly injects the venom into it, but does not wrap it in a spider web. On the contrary, it keeps it trapped with its chelicerae until the poison acts and it dies.

Subsequently, he injects his gastric juices to pre-digest it. The gastric juices initiate the digestion of the prey's tissues and then the spider absorbs this predigested substance to continue the digestive process inside.

Sting and effect

Bite

The brown recluse spider is a shy and withdrawn species that will usually not bite a human unless it feels threatened. In these cases, the wound is not initially painful and may even go unnoticed. About half the time, the spider bite will not produce any symptoms.

Effect

In some cases, the discomfort caused by the venom begins to manifest itself between two and eight hours after the bite. In these cases, a clinical picture that receives the name of loxoscelism develops. The most common form of loxocelism is dermally, and in 14% of cases the visceral or systemic form may develop.

The cause of loxocelism is the proteolytic and necrotic nature of the venom of the brown recluse and other fiddler spiders. This venom has at least nine protein fractions with biological activity.

The main agent responsible for tissue necrosis and hemolysis is sphingomyelinase D. Other components include sphingomyelinases, metalloproteinases, and alkaline phosphatase.

Symptoms begin with pain and itching in the area around the wound. Within 36 hours, the pain worsens and an ulceration appears at the injured site. Tissue necrosis appears later and, on occasions, can cause gangrene that warrants amputation of the affected limb.

In milder cases, the necrotic ulcer leaves only a deep scar as a result of the destruction of the soft tissues and that can take months to heal.

Visceral or systemic loxocelism occurs in 14% of those affected. In these cases, the poison enters the bloodstream and is dispersed causing systemic damage in the body. The first symptoms include nausea, vomiting, increased body temperature, rashes, and body aches.

Severe vasculitis can sometimes occur, with occlusion of the local microcirculation. Hemolysis, decreased number of thrombocytes, disseminated intravascular coagulation, kidney failure, and even death can also occur.

Treatment

Specific

There are antidotes on the market against the venom of spiders of the genus Loxoscheles. However, their effectiveness is controversial. Some authors suggest that for the antidote to take effect it must be administered within 36 hours of the sting, while others shorten the time more and place it at 24 hours after the accident.

After that time, the antidote loses its effect. The doses to be applied depend on the antidote used and the clinical picture presented after poisoning.

Loxoscheles reclusa adult male. Taken and edited from: mattbpennywisdom2099.

Nonspecific

The administration of various medications such as antihistamines, corticosteroids, and dapsones has presented contradictory results in the treatment of loxoscelism. Anihistamines are not effective in this treatment while the remaining two only help to reduce the inflammatory response.

Anti-tetanus, analgesics, antibiotics, ice, hyperbaric oxygen, electricity, transfusions, transplants, and surgical removal of the affected area are also used.

References

1. Brown recluse spider. On Wikipedia. Recovered from: en.wikipedia.org
2. Brown Recluse (Loxosceles reclusa). On Spidapedia Wiki. Recovered from: spidapedia.fandom.com
3. AR de Roodt, OD Salomón, SC Lloveras, TA Orduna (2002). Poisoning by spiders of the genus Loxosceles. Medicine.
4. KM Vail, H. Williams & JA Watson (nd). Brown Recluse Spider. Agricultural Extension Service. The University of Tennessee.
5. Recluse spider. On Wikipedia. Recovered from: en.wikipedia.org.
6. JJ Manríquez & S. Silva (2009). Cutaneous and cutaneous-visceral loxoscelism: A systematic review. Chilean Journal of Infectology.