Thus, the experimenter suggested a hypothetical blood-pumping mechanism in which the candiru is able to quickly ingest large amounts of blood without permanently damaging the host.

[3] Modern experiments have shown that the candiru feeds by approaching a host fish and swimming alongside it until close to the gill cover.

The gut of this species is a straight tube with loosely-spaced fibers lining the walls of the connective tissue, most likely facilitating the swelling of the belly that is associated with the candiru.

[3] Although lurid anecdotes of attacks on humans abound, only one somewhat questionable case has evidence behind it, and some alleged traits of the fish have been discredited as myth or superstition.

The biologist never actually observed this; rather, von Martius was told about it by an interpreter relaying the speech of the native people of the area, who reported that men would tie ligatures around their penises while going into the river to prevent this from happening.

[13] Another report, from French naturalist Francis de Castelnau in 1855, relates an allegation by local Araguay fisherman, saying that it is dangerous to urinate in the river as the fish "springs out of the water and penetrates into the urethra by ascending the length of the liquid column.

"[14] While Castelnau himself dismissed this claim as "absolutely preposterous", and the fluid mechanics of such a maneuver defy the laws of physics, it remains one of the more stubborn myths about the candiru.

It has been suggested this claim evolved out of the real observation that certain species of fish in the Amazon will gather at the surface near the point where a urine stream enters, having been attracted by the noise and agitation of the water.

[15] In 1836, Eduard Poeppig documented a statement by a local physician in Pará, known only as Dr. Lacerda, who offered an eyewitness account of a case where a candiru had entered a human orifice.

He relates that the fish was extracted after external and internal application of the juice from a Xagua plant (believed to be a name for Genipa americana).

Another account was documented by biologist George A. Boulenger from a Brazilian physician, named Dr. Bach, who had examined a man and several boys whose penises had been amputated.

[16] American biologist Eugene Willis Gudger noted that the area which the patients were from did not have candiru in its rivers, and suggested the amputations were much more likely the result of having been attacked by piranha.

According to Gudger, this lends credence to the unlikelihood of the fish entering the male urethra, based on the comparatively small opening that would accommodate only the most immature members of the species.

[21] After traveling to Manaus on October 28, 1997, the victim underwent a two-hour urological surgery by Dr. Anoar Samad to remove the fish from his body.

Samad gave him photos, the original VHS tape of the cystoscopy procedure, and the actual fish's body preserved in formalin as his donation to the National Institute of Amazonian Research.

A study conducted by Luis Fernández and Scott A. Schaefer, published in 2009, used DNA sequence data to create the first comprehensive treatment of phylogenetic relationships of trichomycterid catfish.

[23] Vandellia cirrhosa was discovered in the early 1800s by Alexandre Rodrigues Ferreira, a Native Brazilian scholar studying under the Italian naturalist Professor Domingos Vandelli, of which the fish would be named after.

[24] One of the most well known scientific mentions of the candiru appeared in The American Journal of Surgery published in 1930, summarizing the supposedly centuries old tale of a fish that penetrates the urethras of nude bathers in the Amazon.