The fish is attracted by the smell of human urine. After tasting the urine the candiru may follow the urine stream back to the human. It then swims up the urethra and uses its spines to manifest itself somewhere in the urinary tract. After having spread the spines like an umbrella the candiru finally starts to draw blood and may grow by the amount of blood that is consumed. It eats away the muscous membranes and tissues until it is stopped either by hemorrhage or the host. Every attempt to catch the fish by the tail will fail since once in the urethra, it cannot be pulled out because the spines are spread like an umbrella. Men as well as women can be attacked by the candiru.
The candiru refers to parasitic freshwater catfish in the family Trichomycteridae. They can be found in the Amazon River and are almost impossible to see through being translucent. They are eel shaped and can grow up to a size of 6 inches (15cm) in length. Furthermore the candiru is a parasite. They can detect respiratory currents in the water. If detected they can swim into the gill openings of other aquatic species and start feeding on their prey’s blood. The spines around the head pierce the scales of the prey and draws blood while anchoring the candiru in place. The candiru uses its mouth to slurp the blood of the prey while rasping the ling teeth on its top jaw. After having sucked enough blood it thinks to the bottom of the river to digest its meal. The blood sucking is the reason the candiru is often called the vampire fish of Brazil.
Native Amazonias tell stories about the candiru to their relatives for ages already. They warn their children to never urinate into the Amazon River which may be seen by some scientists as the whole point of the story. They believe that the story about the urine smelling candiru is just told to prevent people to urinate into the river streams in order to keep them unpolluted since they represent a major drinking source for the locals.On the other hand there are real stories of people claiming that they have actually been paralyzed by the candiru.