This fish is called the candiru and is a member of the genus Vandellia. The candiru is found in the Amazon region of South America and is a type of catfish. The fish is actually parasitic. It uses spines located on the covers of its gills to attach itself to the gills of other, larger fish. They can be traced back to the 19th and early 20th centuries.
Meet The Candiru: The Penis Probing Fish Of Your Nightmares
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. These smaller species are known for an alleged tendency to invade and parasitise the human urethra ; however, despite ethnological reports dating back to the late 19th century,  the first documented case of the removal of a candiru from a human urethra did not occur until , and even that incident has remained a matter of controversy. Candirus are small fish. They have a rather small head and a belly that can appear distended, especially after a large blood meal. The body is translucent, making it quite difficult to spot in the turbid waters of its home. There are short sensory barbels around the head, together with short, backward pointing spines on the gill covers.
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? 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.
Wikimedia Commons The candiru fish, in an drawing. Of all of the beasts that prowl the Amazon , none is more feared by the locals than the candiru. A river monster feared even above the dreaded piranha; the candiru waits for its unsuspecting prey to step into the river before latching onto it. This little fishy packs a punch. Rather than go for an outward attack, the candiru implants itself inside the human body through a rather unusual entryway — the human penis.