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 sitt svar finner du her. Det finnes en oppdatering på slutten av artikkelen, den kan være grei å få med seg.
Wikipedia har en artikkel om emnet.
Det var siden Damn Interesting som minnet meg på at jeg skulle poste noe om dette.