The story is that the fish swims up a stream of urine into a man's penis, then eats it from the inside. But is there any truth to it?
A candiru (Vandellia cirrhosa) (Credit: The Natural History Museum/Alamy Stock Photo)
Of all the denizens of the Amazon basin, there is none more feared than the tiny fish known as the candiru. Since coming to the attention of science in the early 19th century, this creature has occupied the very darkest recesses of the popular imagination.
The reason for this is the candiru's supposed habit of entering the human penis, lodging itself in place with sharp barbs, and feasting on it from the inside – a horror story that is enough to keep your legs firmly crossed for days.
This tale has been told everywhere: from documentaries on the BBC and Animal Planet to Grey's Anatomy; from William S. Burroughs' Naked Lunch to Chuck Palahniuk's Fight Club; and invariably it serves as shorthand for the worst thing that could possibly happen to a human being. Internet forums abound with references to the fish, as well as grisly embellishments concerning its activities – laying eggs in bladders and suchlike.
So far, so disgusting. But it is not at all clear that any of this is true...
BBC - Earth - Would the candiru fish really eat your genitals?