In the past I have heard tell that you should never pee in the Amazon River lest a certain fish swim upstream into your penis and lock its fins in place in your urethra. Of course I always dismissed this as a tall tale spread by the natives to scare tourists. However, I read recently in the newspaper about the candiru fish, which allegedly does just this. Please gimme the straight poop. –Chase Kimball, via the Internet

Can’t blame you for your skepticism–this is one of those stories you want desperately not to believe. Here’s a description from a 1973 article in Urology by John Herman:

“One of the strangest [stories from the Amazon concerned] a fish that was urinophilic and could swim up the urethra or into the vagina of the unwary native who urinated while bathing in the Amazon. It was said that this fish, known as candiru [in Brazil; as carnero in Spanish-speaking countries], was long, thin, and capable of forcing its way into the body’s passageways following the trail of urine. Once inside it would eat away the mucous membranes and tissues until hemorrhage would kill it or the host. It was also said that even if one caught the fish by the tail, once in the urethra it could not be pulled out because it would spread itself like an umbrella. Indeed, rumors had it that penectomy was preferred to the misery and pain associated with leaving the fish in the urethra!” One imagines that this column’s male readership is now crossing its legs en masse.

Herman’s article is titled, “Candiru: Urinophilic Catfish, Its Gift to Urology,” which doesn’t seem like the world’s most sensitive take on the subject. However, the author refers not to the financial opportunities for urologists but to an anti-candiru folk remedy useful in treating bladder and kidney problems. More on this below.

Are stories about the candiru true? Although many mentions of the candiru can be found on-line and in popular books and magazines, scientific accounts of the fish and its unfortunate habits are old and suspiciously few. Most of what we know comes from the 1930 book The Candiru by Dr. Eugene W. Gudger of the American Museum of Natural History, plus a couple additional articles published in the ’40s. All sources insist that the incredible story is true, but for evidence they rely mostly on vague second- or thirdhand reports from missionaries, doctors, natives, and the like. Even the doctors’ accounts tend to lack persuasive detail, although one article (Eugenio Lins, Journal of Urology, 1945) claims a U.S. navy surgeon named Charles Ammerman operated on three candiru victims, in one case slicing into the bladder to extract the fish.

Whatever the truth may be, there’s little doubt that the candiru, formally known as Vandellia cirrhosa, is capable of attacking humans in the manner described. A type of catfish, the candiru is known to lodge in the gill cavities of larger fish, where it subsists by sucking the blood of its host. Specimens average three inches in length and a quarter inch in diameter. A fast, powerful swimmer, the fish is smooth and slimy, with sharp teeth and backward-pointing spines on its gill covers that make it virtually impossible to remove. Still, it’s difficult to imagine how even the most agile of fish could squirm into someone’s penis during a brief dip in the water, and in fact one account says women are much more likely to be candiru victims due to the greater dimensions of the relevant aperture.

One suggestive bit of evidence is a folk remedy used by Amazon natives, namely the green fruit of the jagua tree, Genipa americana L. The juice of this fruit is brewed into a tea and drunk hot, supposedly causing the skeleton of the fish to dissolve and resulting in its expulsion from the victim within a couple hours. Early observers scoffed at the effectiveness of this concoction, but Lins reported that a synthetic version of the brew had dissolved bladder “incrustations” in a dozen patients and suggested that it might do the same for kidney stones.

Some elements of the candiru legend are clearly exaggerated. There are no confirmed reports of deaths or penectomies–several cases of the latter are thought to have run afoul of piranha. It’s uncertain whether the candiru is actually “urinophilic,” and as far as I know, no one seriously maintains that it can swim out of the water and up a urine stream. Just the same, next time my yacht cruises down the Amazon, I ain’t peeing over the side.

Lest you think the candiru is all bad news, one visionary has proposed them, apparently seriously, as a key prong in a “fish-based security system” for the South Pacific–see You dig a moat around your house, see, and stock it with candiru, piranha, and electric eels. “Should the housebreaker fortuitously not be attacked by the electric eels or the piranha then there is a good chance that he will suffer the invasive penetration of the candiru into the urethra.” Is that brilliant or what? I mean, OK, you might lose a few pets or small children, too, but at least your silverware will be safe.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.