Dear Cecil: 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 candirú fish, which allegedly does just this. Please gimme the straight poop. Chase Kimball, via the Internet

Cecil replies:

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 candirú [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!

Yeah, I know. I crossed my legs too.

Herman’s article is titled, “Candirú: 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-candirú folk remedy useful in treating bladder and kidney problems. More on this below.

Are stories about the candirú true? Although many mentions of the candirú can be found online 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 Candirú 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 (Lins, Journal of Urology, 1945) claims a U.S. navy surgeon named Charles Ammerman operated on three candirú victims, in one case slicing into the bladder to extract the fish.

Whatever the truth may be, there’s little doubt the candirú, formally known as Vandellia cirrhosa, is capable of the attacks described. A type of catfish, the candirú 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 fishes 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 candirú victims due to the greater dimensions of the female 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 in 1945 urologist Eugenio 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 candirú 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 candirú 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’m not peeing over the side.

One last thing. Lest you think the candirú 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 this report. The idea is to dig a moat around your house and stock it with candirú, piranha, and electric eels. “Should the housebreaker fortuitously not be attacked by the electric eels or the piranha,” we read, “then there is a good chance that he will suffer the invasive penetration of the candirú into the urethra.” OK, you might lose a few pets or small children, but at least your silverware will be safe.

Maybe not THAT serious

Dear Cecil:

Thanks for the plug. You linked to one of our Web pages at the end of your piece on “Can the candirú fish swim upstream into your urethra?” on 19th May and the monthly hit-count for our whole site went up by 100%.

Just one complaint. You say, “One last thing. Lest you think the candirú is all bad news, one visionary has proposed them, apparently seriously, as a key prong in a ‘fish-based security system.'” Did you really think that an article credited to the authorship of “Hugh Dunnit & Hans Kneesun-Boompsadaisy” was SERIOUS?

Best wishes, and keep up the good work.

— Tim Adams (no relation), Secretariat of the Pacific Community, Noumea

Cecil replies:

I said apparently seriously. I didn’t say it was serious — a fine distinction, but under the circumstances one grabs for what fig leaves one can. The fact the authors listed their place of residence as “Upper Choirboy, Hampshire, England” should also have been a clue.

Click here for an update on this column.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.