Candiru species are of medical importance to people inhabiting the areas where they are native, such as the
Amazon basin. The bites of whale candiru are strong enough to leave marks upon human bone; circular marks are often visible on the bones of the animal fed upon. The
undescribed human-biting candiru was first documented while
feeding on blood from a boy's
back, which is noted to be not dissimilar from the method other vandelliines use to feed off of fish blood. this alleged ability has been described in
ethnological reports dating back to the
19th century. However, these accounts of human parasitism are often
biased, arising from "imprecise,
second- and
third-hand accounts,
misconceptions, and
folk tales"; with
Plectrochilus machadoi specimens found embedded in the belly of a
surubí after apparently burrowing through its
body wall, and species of
Paracanthopoma such as
P. parva boring into the flanks of
armored Doras catfish,
piramutaba, and
gilded catfish (though these are apparently instances of
phoretic "hitchiking"), and all species in the subfamily are known to enter the
gill cavity of larger fish (such as
characins,
catfish, or
stingrays) to latch onto the
branchial artery which connects the gills to the
heart; Despite this known behavior, they may not comfortably fit the stricter definition of parasitism, leading some authors to use terms such as semi-parasitism, or more recently;
micropredation, where the parasite is not relying upon a single
host species or individual. Whatever the case, these fish are highly
specialized hematophagic parasites, mechanisms to obtain
vitamin B lacking in blood meals, and an
anti-coagulative agent to facilitate blood feeding and/or digestion. and most commonly,
Vandellia cirrhosa, which is the
type species of the
type genus of its subfamily. though experimental evidence disproves this; a 2001 study shows that these fish actually hunt by sight (the species studied being
Vandellia cf. plazaii) and displayed no attraction to urine (or other potential chemical attractants such as
ammonia, fish slime, or
amino acids) at all. Despite their names, candiru-açu are not parasitic on any animal. Organisations such as the
Florida Fish and Wildlife Conservation Commission (FFWCC) and
Texas Parks and Wildlife Department (TPWD) restricts the possession of all species of Trichomycteridae ("Parasitic Catfishes"), which limits the possession of all listed species to research, educational exhibition, aquaculture, and for control or eradication purposes only, and further limits the species eligible for these purposes.
Historical accounts The earliest published report of candiru attacking a human host comes from German biologist
C. F. P. von Martius in 1829. 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. Other sources also suggest that other tribes in the area used various forms of protective coverings for their genitals while bathing, though it was also suggested that these were to prevent bites from
piranha. Martius also speculated that the fish were attracted by the "odor" of urine. 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." 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. 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. However, the veracity of both Le Cointe's and Poeppig's accounts are questionable, due to a trend of Europeans from various careers residing in Brazil including scientists, "explorers, medical men, and missionaries" regularly using exaggerated accounts of native people to advance their economic and social status through writing and building rapport with others with similar positions. Gudger, in 1930, noted there have been several other cases reported wherein the fish was said to have entered the vaginal canal, but not a single case of a candiru entering the anus was ever documented. 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. The 1991 paper "
Candirú: Amazonian parasitic catfish" documents various means of defence and treatment against candiru parasitism, such as urinary protectors and herbal remedies. The paper claims a tight-fitting
bathing suit is proof against them, and
vitamin C "
megadose therapy" softens the candiru's fin spines enough to excrete the fish.
Modern cases To date, there is only one documented case of a candiru entering a human urethra, which took place in
Itacoatiara,
Brazil, in 1997. In this incident, the victim (a 23-year-old man named Silvio Barbossa, also known as "F.B.C.") claimed a candiru "jumped" from the water into his urethra as he urinated while thigh-deep in a river. After traveling to
Manaus on 28 October 1997, the victim underwent a two-hour
urological surgery by Dr. Anoar Samad to remove the fish from his body. In 1999, American
marine biologist Stephen Spotte traveled to Brazil to investigate this particular incident in detail. He recounts the events of his investigation in his book
Candiru: Life and Legend of the Bloodsucking Catfishes. ==References==