Candiru

The candiru, or toothpick fish, Vandellia cirrhosa is a tiny parasitic catfish of tropical South America.

Normally the candiru lives an ectoparasitic existence, entering the gill cavities of larger fish to bite off scraps of tissue or drink their blood.

Although it is only a tiny, translucent eel-like creature no more than six inches long at most, the candiru is widely feared, perhaps even more so than the piranha, for its habit of entering the human urethra, which it is popularly believed to locate by following a scent trail. Erectile spines on its head, used to attach to the fish it feeds upon, make it almost impossible to extract without surgery; given the paucity of medical facilities in the Amazon region, most persons so afflicted die in horrific agony.

Stories about the candiru swimming up a stream of urine were thought to be false, until one recent well-documented case.