Candiru
Candiru (candiru without an accent in official Portuguese spelling; also canero, toothpick fish, or willy fish) refers to parasitic freshwater catfish of a number of genera in the family Trichomycteridae. They are found in the Amazon River and have a reputation among the natives as the most feared fish in its waters, even over the piranha. They are eel-shaped and translucent, making them almost impossible to see in the water. Some species have been known to grow to a size of 6 inches (~15 cm) in length.
The definition of candiru differs between authors. The word has been used to refer to only Vandellia cirrhosa, the entire genus Vandellia, the subfamily Vandelliinae, or even the two subfamilies Vandelliinae and Stegophilinae.

# Parasitism
While the members of the subfamily Vandelliinae feed on blood, members of Stegophilinae may feed on scales, mucus, or carrion.
This fish is feared to attack humans and swim into an orifice (the vagina, anus, or even the penisand deep into the urethra). Because of spines protruding from the fish, it is almost impossible to remove except through surgery. The fish locates its host by following a water flow to its source and thus urinating while bathing increases the chance of a candiru homing in on a human urethra. Natives have also been known to bathe facing the current, as doing so would decrease the chances of the organism lodging itself in the rectum. Other orifices such as the penis or vagina are covered up with the use of hands.
Though there have been documented candiru attacks on humans, there is no evidence the fish can survive once inside a human. A traditional cure involves the use of two plants, the Jagua plant (Genipa americana) and the Buitach apple which are inserted (or their extract in the case of tight spaces) into the affected area. In theory, these two plants together will kill and then dissolve the fish. More often, infection causes shock and death in the victim before the candiru can be removed.
A well-circulated myth is that the candiru is capable of swimming up the stream of urine in mid-air to a victim standing on shore or a boat. This is physically impossible as the maximum swimming velocity of the fish is opposed by the downward velocity of the urine stream, and the further impossible act of the 5-14 mm wide fish maintaining position and thrust within a 27 mm wide column of fluid. They are also probably not attracted to urine as commonly thought.

# Popular culture
- The candiru has been featured on the television shows Grey's Anatomy (where it was called the "penis fish"), The Venture Bros., and Law & Order: Special Victims Unit.  Dr. Oz discussed the candiru on The Oprah Winfrey Show on May 21, 2007. It was sought after in Nick Baker's Weird Creatures, a British TV series about the world's strangest animals.
- It has also been mentioned in the films Anaconda, The Rundown, Medicine Man, Sniper and the Rifftrax version of Predator
- It is also mentioned in the books Amazonia by James Rollins, The Codex by Douglas Preston, Born Survivor by Bear Grylls, Naked Lunch by William S. Burroughs, and is referred to in A History of the World in 1012 Chapters by Julian Barnes. It is mentioned in the afterword to Peeps by Scott Westerfeld, and is misrepresented in Ted Bell's novel Spy as swimming up the urine stream of someone standing knee-deep in water, then living inside the person.
- The Candiru was featured in a recent episode of Weird Nature, which runs on The Science Channel.