Dangerous Candirus are native to the Amazon River region of South America.
The candiru, also known as Vandellia cirrhosa or toothpick, is a small, parasitic, scaleless freshwater catfish native to the Amazon River region of South America. Candiru belongs to the family Trichomycteridae, which includes 207 species of parasitic catfish. For some, the term ‘candiru’ refers not just to one fish, but to the entire genus Vandellia. Many sources, however, use the term to refer only to Vandellia cirrhosa.
During urination, the urethra expands enough to allow a parasite to enter.
The eel-like fish can grow up to six inches long and has a translucent body with a small head. Not much is known about the breeding habits of this fish. It feeds on larger fish by drinking their blood, and after feeding, its belly may look swollen and distended.
Its eating habits have given the candiru an infamous reputation, even more infamous than the piranha. The fish literally hunts by testing the water. It searches its prey for ammonia, a by-product that is expelled by the gills of other fish. When the parasite locates a victim, it forces itself into the victim’s gill cavity. Once inside, it closes by raising spikes on its own gills.
When people swim or lounge in the waters these fish inhabit, they must be very careful not to urinate while doing so. Human urine contains ammonia, the chemical used by candirus to locate prey. During urination, the urethra expands enough to allow urine to flow out and the parasite to enter.
These fish are known to follow the path of urine into the urethra of unsuspecting people. For example, there is a well-known case of a man who had to surgically remove a six-inch fish from his penis after it had been lodged there for a few days. The fish must be removed surgically because the spines on the gills make it impossible to remove by pulling.
Another fish known simply as the candiru is the candiru asu, which is often mistaken for the parasite that feeds on blood. This type feeds mainly on organs and meat. It has a small, circular mouth filled with sharp teeth, which it uses to make a hole in the victim. Once the hole is made, the fish penetrates the body and consumes it from the inside. These fish not only eat carcasses, but any body that is incapacitated in the water.
When bodies are recovered from the Amazon River, forensic doctors often discover bullet holes in them. Upon closer inspection, an inspector may find that the body is actually teeming with these parasites. Some carcasses were found to contain hundreds of these fish.