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The Brazilian wandering spider. Photo: Techuser

A bite from the banana spider (also known as the Brazilian wandering spider) of Central and South American rain forests causes shortness of breath, excessive salivation, tremors and—for men—a persistent, intensely painful erection, known as priapism in the medical community.

So potent is this spider’s ability to command an erection that researchers wondered if it couldn’t be somehow transformed and used for good. According to WebMD, erectile dysfunction affects around 18 million men in the U.S. alone, and common treatments like Viagra, Levitra and Cialis fall short of providing results for one in three men with ED.

Scientists write in the Journal of Sexual Medicine that one of the banana spider’s toxins, PnTx2-6, helped elderly rodents with their ER, reports National Geographic News. The toxin triggered the release of nitric oxide, which increased circulation in the rats’ genitals and relaxed the relevant blood vessel walls. If rats and human men are anything alike, the researchers suspect treatments eventually derived from the toxin might help patients who fail to respond to drugs like Viagra, which relies on a different mechanism.

Banana spiders are not the only organisms found in nature with a particular penchant for bringing on unwanted erections. Rabies, too, sometimes has this effect. In 1988, doctors described the case of one such affliction in the Postgraduate Journal of Medicine:

A 47 year old male was admitted with the chief complaints of recurrent ejaculation and hydrophobia. The patient, who was fully conscious and lucid at the time of admission and gave us his own history, confirmed that that morning he had hypersensitivity of the penis manifesting as recurrent erection and ejaculation occurring at the slightest touch. The hypersensitivity was so exquisite that the mere touch of his underwear against his penis was enough to trigger off spontaneous erection and ejaculation.

The patient died, however, and fortunately there’s no talk in the scientific community of treating no-show erections with rabies.

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