Naked Lunch: "the candiru is a small eel-like fish or worm about one-quarter inch through and two inches long patronizing certain rivers of ill repute in the Greater Amazon Basin, will dart up your prick or your asshole or a woman's cunt faute de mieux, and hold himself there by sharp spines with precisely what motives is not known since no one has stepped forward to observe the candiru's life-cycle in situ..."
This is just one of several mentions of the candiru in NL. As is so often the case, Burroughs knew what he was talking about:http://scienceblogs.com.br/uoleo/2009/03/candiru.php
Candiru (or the-fish-you-don't-want-to-know-about)
Two fish are subject of nightmares in the Amazon region: the piranha and the candiru. The former is the carnivore that has sharp teeth and is attracted to blood, like small river sharks, while the later is a parasite that is attracted to urea and has a head that works like a hook.
While the piranhas kill in the classical way: chewing your meat until there are only cleaned bones and a temporally satisfied school. The candiru kills in an innovative way: using agony. But not the agony you feel when people rhyme honey with money, this is much worse.
This fish, which is thicker than it should be, enters the urethra of the ones that try to relieve themselves in the river. Why would this animal do such an evil thing?
The candiru´s agonizing rise throught the urethra is actually an accident. The fish does not really cares about it. This fish is a parasite that attaches itself for a few minutes to other fishes in order to feed of their blood. Those fishes excrete ammonia and urea from their gills, which attract the pseudovampire. When the candiru reaches the gills, it uses its hook to get stuck to an artery, where it will have blood pumped into itself using the prey's blood pressure. Clever, ay? The fish smell urea and ammonia dissolved in the river, like piranhas smell blood and my dog smells fear.
However, when Candiru goes into the human urethra, nothing happens as it is not able to suck blood like mosquitoes do. Unless there is positive pressure pushing blood down its throat, it cannot feed. For the candiru, the human urethra is like a soup bowl for a crane.
When the candiru notices that it cannot feed, it relaxes and tries to get out However, that´s inevitably too late: by the time, the owner of the urinary tract is already running through the forest with his member in his hands and crying a lot.