In this particular genus, there are five known similar species whose members are also highly venomous. They include some of the relatively few species of spiders that present a threat to human beings. The Brazilian wandering spider can grow to have a leg span of up to 4 — 5 inches. They are large hairy spindly-looking spiders who have eight eyes, two of which are large. Brazilian wandering spiders are fast-moving spiders, their legs are strong and spiny and they have distinctive red jaws which they display when angered.
The Brazilian wandering spider is not a Tarantula. Brazilian wandering spiders are not even in the same family group. Tarantulas are harmless to humans and are mostly ambush killers who wait for prey to come to them. Brazilian wandering spiders are active hunters. Brazilian wandering spiders and Tarantulas do have one thing in common, however, they do not eat bananas. The Brazilian Wandering spider is so-called because it wanders the jungle floor, rather than residing in a lair or maintaining a web.
This behaviour is a "back-off"-signal that if being ignored will sooner or later lead to a biting attempt of the spider. However, it should be emphasised here, that this behaviour is primarily defensive, although often mistaken for aggression. In rational terms, Phoneutria spiders only do the same as many other animals: They try to defend themselves when being threatened. At most some have a very low threshold to feel disturbed or threatened. Important is that the spiders do not attempt to bite people by chance.
Rather the opposite - from a spider's perspective it is quite costly to "waste" venom on humans. It takes time and energy to produce the venom which primarily serves to immobilize and eventually kill the prey and a spider that spent its venom on uneatable things may be unable to overcome prey soon after and may therefore have to hunger for a while. The majority of encounters between humans and this spider are caused by humans accidentally coming across a spider hidden somewhere in their home, at the market, or even in the streets.
Bites by the P. However if a full amount of venom is injected it can cause death if an anti-venom cannot be reached. Although these spiders can be very dangerous to humans, the venom of these spiders is believed to have a great medical importance and is currently being researched.
When males are attacked by this spider they will often get hour long and usually painful erections, also known as priapism. A team of Brazilian and American scientists found that one of the toxins in the venom, PnTx, has been found to improve erectile function in aged rats.
Bucherl reported that mating occurs in April and May. Subsequently, eggs are laid and deposited into sacs that are carried by the female. Female spiders may carry up to four egg sacs, collectively containing over 3, eggs. Immature Phoneutria nigriventer can capture prey immediately after leaving the egg sac. As the spiderlings grow, they must molt or shed their exoskeleton to allow for further growth. In their first year, an immature spider will undergo between five and ten molts, depending on temperature and the amount of food consumed.
As they mature, the frequency of molting decreases. In their second year, the growing spiders will molt three to seven times.
During their third year, Phoneutria nigriventer molts only two to three times. Following one of these molts, the spiders typically become sexually mature. In captivity, Phoneutria nigriventer has a lifespan of up to six years Bucherl As Phoneutria spiders mature, the proteins present in their venom change, becoming increasingly lethal to vertebrates Herzig et al.
When confronted by a potential predator, all members of the genus exhibit a characteristic threat display Martins and Bertani Figure 8.
Phoneutria spiders are more prone to holding their ground with this defensive display than to retreating Lucas The spider stands on the two posterior pairs of legs, with the body oriented nearly perpendicular to the ground. The two pairs of forelegs are thrust upwards and held above the body, displaying the brightly colored underside of the legs. The spider sways its legs laterally and shifts towards the movements of the threat, while displaying the fangs and bristling spines on the legs.
Figure 8. Characteristic threat display of Phoneutria species. When confronted by a potential predator, Phoneutria spiders assume a pose that makes the spider seem much larger, while displaying the contrasting colors on the underside of the forelegs. Phoneutria spiders are nocturnal hunters that do not construct webs to capture prey. They feed on other invertebrates and small vertebrates such as frogs Pacheco et al. Phoneutria boliviensis sometimes wraps captured prey in silk, affixing it to the substrate, usually a vertical perch Hazzi During the day, Phoneutria spiders seek shelter within vegetation, crevices in trees or inside termite mounds.
Species in the genus actively forage for arthropod and small vertebrate prey in the understory vegetation and on the ground. Some species often utilize large-leaved plants such as palms as a substrate for hunting. Torres-Sanchez and Gasnier hypothesize that doing so allows immature spiders to avoid larger spiders that are potential predators on the ground, while providing the ability to better sense the vibrations of an approaching predator.
Worldwide, there are approximately 40, described spider species, most of which use venom to subdue prey. Of these, very few are medically important to people. Before , spiders were estimated to be responsible for fewer than deaths per year globally Nentwig and Kuhn-Nentwig Per million people, spiders killed between 0.
In comparison, snakes and scorpions respectively caused 20 and 0. The most medically important spiders include the widow spiders Latrodectus , Theridiidae , the recluse spiders Loxosceles , Sicariidae , the Australian funnel-web spiders Atrax and Hadronyche , Hexathelidae and armed spiders Phoneutria , Ctenidae Vetter and Isbister In the past three decades, there have not been any confirmed fatalities due to envenomation by widow spiders, Australian funnel-web spiders or armed spiders Nentwig and Kuhn-Nentwig Among the recluse spiders, bites are easily misdiagnosed, making it difficult to determine figures regarding their bites.
Despite the low frequency of fatalities attributed to these taxa around the world, bites from species in these groups, including Phoneutria, can be serious and often require medical treatment. As with other spiders of medical importance, venom is injected into prey or defensively into potential predators through the fangs Figure 9.
Venom is produced by glands located in the chelicerae structures on the face, immediately above the fangs. The venom of Phoneutria spiders consists of a mixture of proteins and peptides that are active against the nervous systems of both invertebrates and vertebrates Gomez et al. Among species in the genus, venom composition and potency vary, with Phoneutria nigriventer and Phoneutria keyserlingi having particularly potent venoms Vetter and Hillebrecht
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