The banana spider (Phoneutria nigriventer), also known as the banana spider or Brazilian wandering spider, is a fairly poisonous arachnid of the Ctenidae family. Together with seven other species make up the genus Phoneutria. These spiders are the main responsible for the majority of the cases of accidents with spiders in Brazil and other South American countries..
They receive the name of banana spider because of the tendency of these arachnids to take shelter in the banana bunches. Due to this custom and the export of bananas to other countries outside the area inhabited by these spiders, several specimens have been recorded in atypical areas..
Other common names for this spider are “armadeira” or armed spider (Brazil), due to the defensive position it adopts when irritated, or red beak (Argentina) due to the reddish coloration of its chelicerae.
They cause more than 800 accidents a year, with growing trends, only in Brazil. It is considered one of the most medically important spider species worldwide, despite the fact that other species of the genus Phoneutria, What P. fera are potentially more poisonous.
Despite the negative effects of the poison and the high incidence of accidents, many properties have been discovered in it, from which new drugs can be developed for the treatment of various pathologies of neurological origin.
Like other spiders in natural ecosystems, they have countless natural enemies, including other arachnids, birds, omnivorous mammals, and parasitoid insects such as wasps in the Pompilidae family..
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They are large spiders. The cephalothorax can measure up to 4.5 cm wide and a total length (including the legs) of up to 16 cm. Like the representatives of the family Ctenidae, it consists of three rows of eyes arranged in a 2-4-2 configuration.
One front row with two small central eyes; a middle row with four eyes of which the two central ones are the largest; and a back row with two small, widely spaced eyes.
The coloration of these spiders is usually light brown on the back, with some scattered black linear spots in the midline and anterior edges of the cephalothorax. The legs are dark brown with black bands in the distal region of the femurs, tibiae and tarsi..
Ventrally, the coloration varies from light brown to black and the femurs have light bands in the distal region. The chelicerae have a characteristic reddish-brown coloration that stands out when the banana spider assumes defensive positions. The legs have numerous spines.
The longevity of these spiders in the wild is usually variable. However, on average, females can live for about five years and males for about two and a half..
Phoneutria nigriventer It is the main culprit for most spider accidents in southeastern Brazil, which is why the species is of great medical relevance.
It has a poison with highly toxic characteristics that mainly affects ion channels and also induces the release of neurotransmitters. The voltage-gated sodium, potassium and calcium channels are the most affected by these toxins with evident neurotoxic action.
More than 17 peptides have been determined that have direct action on ion channels. The TX1, TX2 and TX3 fractions have direct effects on the Na + and Ca channels+.
In addition, the TX3 fraction, which contains six toxic peptides that generate the release of neurotransmitters such as acetylcholine and glutamate, act on the Ca + channels that control the exocytosis of synaptic vesicles..
The symptoms associated with the venom of this spider and its effects on man are quite varied..
The venom has neurotoxic characteristics that mainly affect voltage-gated Na + channels. These toxins induce uncontrolled continuous discharges in nerve and muscle cells. The venom depolarizes the membrane of these cells and increases the frequency of nerve impulses (PA).
On the other hand, the venom can cause morphological alterations in the nerve fibers that enhance the action of the venom in the Ca + channels. In fact, several lines of research suggest the interaction of fractions of the venom components with Ca channels.+.
In general, after the "bite" a localized intense and radiating pain begins in addition to various toxic symptoms characterized by the existence of cramps, tremors, tonic seizures, spastic paralysis, priapism, hypersalivation, cardiac and respiratory arrhythmias, visual disturbances and cold sweats.
The effect of the poison is especially dangerous in children and the elderly. In men, it causes continuous painful erections or priapism, which can last for more than four hours and cause damage to the erectile tissue. Due to this, the venom is studied as an alternative to combat erectile dysfunction.
Phoneutria nigriventer It is widely spread in central and southeastern Brazil, occupying a large part of the Atlantic Forest. In addition to the south of South America it is recorded in Paraguay, Uruguay and North Argentina (Misiones, Chaco, Formosa, Salta and Jujuy Province).
The specimens recorded in Montevideo (Uruguay) and Buenos Aires (Argentina), in addition to some European cities, were probably introduced with bananas imported from Brazil.
Under natural conditions, this spider basically thrives at ground level. However, it is capable of exploiting elevated microhabitats of it, such as shrub vegetation. During the day they take refuge under tree bark, banana fruits, epiphytic plants such as bromeliads, palm trees, under trunks on the ground or in leaf litter..
On the other hand, they can also adapt very well to urban and suburban ecosystems, which is why it is usually common in banana crops and has adopted the common name of the Brazilian banana spider..
They can be seen inside human dwellings, where they look for damp and dark places to take refuge (shoes, wardrobes, furniture, curtains in among others).
In addition, due to its plasticity and powerful poison, it has managed to establish itself outside its natural range in other South American and Central American countries..
Much of the species of the genus Phoneutria are easily distinguished from other genera of the family Ctenidae very similar) as Cupennius and ctenus) by the presence of a dense scopula on the tibiae and tarsi of the first pair of legs.
There are few species of Phoneutria described, however, there is often confusion in the identification in several of them.
P. nigriventer was considered a synonym of P. fera. but, after an exhaustive taxonomic revision, clear differences were found in the proportions of length and width of the epiginium of the female and the proportions of length and width of the tibia of the pedipalp in the male specimens..
On the other hand, differences in the coloring patterns were also determined.
These spiders prefer warm, tropical and subtropical environments. Although its conservation status has not been evaluated, the disappearance of its natural habitats as a result of deforestation and other human activities, can endanger many of the populations of this species.
On the other hand, being dangerous spiders due to the power and strong effects of their venom, they are constantly eliminated by the inhabitants of the areas where this spider is distributed..
Fortunately, it is a species widely adaptable to habitat intervention and survives well in urban and suburban environments..
Banana spiders Phoneutria nigriventer have a reproductive period between April and July, which coincides with an increase in the number of accidents with humans.
During mating, a courtship behavior of the males as described for other species and genera of the Ctenidae family has not been observed, such as the movement of the front legs and drumming of the pedipalps that transmit vibrations through the substrate..
In this sense, it seems that the female recognizes the male when he contacts her. If the female is receptive, she adopts a passive posture. If the female accepts, mating is usually quick; if it shows no interest in reproducing, the male is likely to be preyed upon or flee quickly, although the rate of cannibalism in adults is not well understood.
The male rises to the female's prosoma and turns to the left or right side of the female's opistosome according to the pedipalp used for copulation. During the process, he picks up the female's legs, which are very close to the body with the femurs in an upright position. The female rotates her abdomen for the male to insert the sperm.
After mating, the female can build 1 to 3 flattened white egg sacs in succession. These can measure up to 3 cm in diameter and contain between 900 and 2760 small eggs depending on the reproductive condition of the female..
The female tends to actively care for the cocoon. After hatching, the young build a communal network in which they disperse until they molt twice. During this period, the female is generally vigilant. Once the little spiders begin to leave the web, after two weeks, the female also leaves.
During the first year of life, they molt about 5 times, 3 to 4 times during the second year, and mature sexually in the third or fourth year of life..
This spider is extremely aggressive, its prey is very varied and it is only limited in its feeding activities by the size of the prey. Its success as a great predator is mainly due to the powerful toxins that its venom presents.
Brazilian banana spiders prey on various species of invertebrates including other species of spiders and even small vertebrates such as amphibians and rodents. Being a ground-dwelling or cursorial spider, it can hunt and consume almost anything in its path and can capture..
They also have cannibalistic behavior in the early stages of their development and when non-receptive females capture males with reproductive intentions..
Amphibian species like Crossodactylus schmidti Y Dendropsophus elegans have been reported as prey of P. nigriventer. Probably due to the mostly nocturnal habits of these spiders, the amount of amphibian species that they consume is very high, especially those that inhabit the litter.
This spider is extremely aggressive, even with animals several times the size of a human when intimidated..
When disturbed or encountering a possible predator or any other threat, it assumes a defensive posture that is characteristic of all recognized species of the genus. Phoneutria.
They usually "stand" or assume an almost vertical position on their two pairs of hind legs, based on the dorsoposterior region of the abdomen. The two pairs of front legs are upright and stretched perpendicular and together on each side.
In this way they display their reddish-brown chelicerae as a measure of intimidation. Additionally, they show off cheliceral nails (“fangs”) and perform warning lunges. When they attack they can attack at distances that range between 20 and 40 cm, so it is advisable to move away from them at this point.
Despite their aggressiveness and dangerousness, before assuming any defensive posture or attacking, these spiders are generally shy and flee from danger quickly in search of refuge..
Juveniles, after emerging from the egg sac, begin dispersal after the fifth or sixth week, probably due to the increased frequency of cannibalism among juveniles..
Juveniles are usually more active than adults, due to their dispersive behavior during these stages. For this reason, they are exposed to many dangers and very few individuals tend to survive..
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