Editing Candiru (fish)

{{Short description|Species of ray-finned fish}}
{{For|the scavenging species known as candiru-açu|Cetopsis candiru|Cetopsis coecutiens}}
{{Pp|small=yes}}
{{Speciesbox
| name = Candiru
| image = Vandellia cirrhosa after a full meal of blood.jpg
| image_caption = A candiru after a full meal of blood
| status =
| status_system =
| genus = Vandellia (fish)
| species = cirrhosa
| authority = [[Achille Valenciennes|Valenciennes]], 1846
}}

'''Candiru''' ('''''Vandellia cirrhosa'''''), also known as '''cañero''', '''toothpick fish''', or '''vampire fish''', is a species of [[parasite|parasitic]] freshwater [[catfish]] in the [[family (biology)|family]] [[Trichomycteridae]] native to the [[Amazon basin]] where it is found in the countries of Bolivia, Brazil, Colombia, Ecuador, and Peru. The name "candiru" is also used to refer to the entire genus ''[[Vandellia (fish)|Vandellia]]''.

This species is known for an alleged tendency to invade and parasitize the human [[urethra]] and other bodily openings; however, despite ethnological reports dating back to the late 19th century,<ref>{{cite book|title=Killers of the Seas: The Dangerous Creatures That Threaten Man in an Alien Environment|last=Ricciuti|first=Edward R.|author2=Bird, Jonathan|publisher=The Lyons Press|year=2003|isbn=978-1-58574-869-3}}</ref> the first documented case of the removal of a candiru from a human urethra did not occur until 1997, and even that incident has remained a matter of controversy.

==Description==
[[File:Kandiru (Vandellia cirrhosa)..png|thumb|An artistic rendition of ''Vandellia cirrhosa''.]]
''Vandellia cirrhosa'' is a small, freshwater catfish. Members of the genus ''Vandellia'' can reach up to {{cvt|17|cm|0}} in [[standard length]],<ref>{{FishBase genus|genus=Vandellia|year=2017|month=May}}</ref> but some others can grow to around {{cvt|40|cm}}. The fish has an elongated body with an anterior [[dorsal fin]] and [[pelvic fin]], and an [[anal fin]] slightly larger than the dorsal fin. The [[caudal fin]] is fairly small with a truncated shape. Each has 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. Blood is often visible through the translucent body after feeding.<ref name=":3">{{cite journal |last1=Zuanon |first1=Jansen |last2=Sazima |first2=Ivan |year=2003 |title=Vampire catfishes seek the aorta not the jugular: candirus of the genus ''Vandellia'' (Trichomycteridae) feed on major gill arteries of host fishes |journal=Journal of Ichthyology and Aquatic Biology |pages=31–36 |url=https://ecoevo.com.br/publicacoes/pesquisadores/ivan_sazima/2004_Vampirecatfishesseektheaorta.pdf}}</ref> The fish has small eyes with yellow irises.<ref name=":1">{{cite journal |last1=Breault |first1=J.L. |year=1991 |title=Candiru: Amazonian parasitic catfish |journal=Journal of Wilderness Medicine |volume=2 |issue=4 |pages=304–312 |doi=10.1580/0953-9859-2.4.304}}</ref> There are short sensory [[Barbel (anatomy)|barbels]] around the head, together with short, backward pointing spines on the gill covers.<ref>{{cite book |author-link=Ross Piper |last1=Piper |first1=Ross |year=2007 |title=Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals |publisher=Greenwood Press |isbn=978-0-313-33922-6}}</ref> These spines have been described as popping out in an umbrella-like fashion, which could be used to help lodge the fish into its host.<ref name=":1"/>

All members of the subfamily [[Vandelliinae]] share the traits of blood [[parasitism]], with parasitism in general being a shared ancestral trait of all members of [[Trichomycteridae]]. They have individual claw-like teeth for this purpose.<ref name=":2">{{cite journal |last1=Fernandez |first1=Luis |last2=Schaefer |first2=Scot A. |year=2009 |title=Relationships among the Neotropical Candirus (Trichomycteridae, Siluriformes) and the evolution of parasitism based on analysis of mitochondrial and nuclear gene sequences |journal=Molecular Phylogenetics and Evolution |volume=52 |issue=2 |pages=416–423 |doi=10.1016/j.ympev.2009.02.016|hdl=11336/76532 |hdl-access=free }}</ref> Their bodies are very small and elongated to easily slip into the gills of host fish.<ref>{{cite book |last1=Adriaens |first1=Dominique |last2=Baskin |first2=Jonathan N. |last3=Coppens |first3=Hendrik |last4=Ledeganckstraat |first4=K L |year=2011 |chapter=Evolutionary morphology of trichomycterid catfishes: about hanging on and digging in |editor1-first=Joseph S. |editor1-last=Nelson |editor2-first=Hans-Peter |editor2-last=Schultze |editor3-first=Mark V. H. |editor3-last=Wilson |title=Origin and Phylogenetic Interrelationships of Teleosts |pages=337–362 |url=https://www.researchgate.net/publication/228500129}}</ref>

==Habitat and distribution==
Candiru inhabits the [[Amazon Basin|Amazon]] and [[Orinoco]] basins of lowland [[Amazon biome|Amazonia]]. 

This fish lives in shallow water with muddy, sandy, or rocky bottoms.<ref name=":3"/> It can be found in [[riffle]]s.<ref>{{cite journal |last1=Teresa |first1=Fabricio Barreto |last2=de Souza |first2=Luzia Shirlei |last3=da Silva |first3=Dianne Michelle Alves |last4=Barbosa |first4=Hugo de Oliveria |last5=Lima |first5=Jane Dilvana |last6=Nabout |first6=Joao Carlos |year=2016 |title=Environmental constraints structuring fish assemblages in riffles: evidences from a tropical stream |journal=Neotropical Ichthyology |volume=14 |issue=3 |doi=10.1590/1982-0224-20150185|doi-access=free }}</ref> Its distribution is patchy and it does not seem to move very far from its spawning sites.<ref name=":3" />

One location that ''Vandellia cirrhosa'' is specifically known to inhabit is the [[Purus River]] of Brazil. This location is hard to study due to its geographic isolation, something that is common among the habitats of candiru.<ref name=":4">{{cite journal |last1=dos Anjos |first1=HB |last2=Zuanon |first2=J |last3=Braga |first3=TP |last4=Sousa |first4=KS |year=2008 |title=Fish, upper Purus River, state of Acre, Brazil |journal=Check List |volume=4 |issue=2 |pages=198–213 |doi=10.15560/4.2.198|doi-access=free }}</ref>

== Diet ==
[[File:Vandellia cirrhosa taking blood from a host.jpg|thumb|right|A candiru taking blood from the gills of a fish host.]]
[[File:Vandellia cirrhosa.png|thumb|A closeup of a feeding candiru as it begins to swell with blood.]]
Candiru is [[hematophagous]] and parasitizes the gills of larger Amazonian fish, especially catfish of the family [[Pimelodidae]] ([[Siluriformes]]) and members of the family [[Characidae]].<ref name=":3" /> However, it has been known to parasitize many species in the same location, suggesting that its feeding habit is based more on availability than species preference. Vandellinae is one of only two groups of jawed vertebrates that exclusively feed on blood.<ref name=":5">{{cite journal |last1=Bonato |first1=Karine Orlandi |last2=Silva |first2=Priscilla Caroline |last3=Carvalho |first3=Fernando Rogerio |last4=Malabarba |first4=Luiz Roberto |year=2021 |title=Trophic interactions of vampire catfishes (Siluriformes: Vandellinae) revealed by metabarcoding analysis of stomach contents |journal=Freshwater Biology |pages=1–7 |url=https://www.researchgate.net/publication/356732468}}</ref>

The feeding mechanism of the candiru was not understood until fairly recently, but many theories had been proposed before. Some suggested that it uses its sharp teeth to latch onto an artery or vein and stays attached to the host until it has ingested enough blood. It then lets go of the host and continues swimming.<ref name=":2" /> Others suggested that it extracts blood from its hosts by latching onto the [[gill filament]]s, which bleed freely into the [[alimentary tract]] of the candiru. In one experiment involving ''Vandellia cirrhosa'', no evidence of gill damage was found on the fish hosts. 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.<ref name=":3" />

Modern experiments have shown that the candiru feeds by approaching a host fish and swimming alongside it until close to the gill cover. It then attempts to penetrate the gill chamber by forcing itself underneath. The candiru has also been seen entering the host through its mouth, though this behavior seems to be rare. While latched onto the host fish's gill chamber with sharp teeth, the candiru goes limp and quickly swells up with blood. 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. The lack of any protrusible jaw supports the theory that this species does not suck blood, but rather bites into a blood vessel and ingests the fluid that flows freely into the mouth.<ref name=":3" /> Because the candiru relies on the blood pressure of the host to ingest blood from the ventral or dorsal arteries, host fish must be selected by size.<ref name=":5" />

The time taken to get its fill of blood depends on the size of the candiru and whether it has attached to a large or small blood vessel. Because of the small size of ''Vandellia cirrhosa'', it generally seems to take no more than two minutes to ingest the required amount of blood from the host fish. This short duration is theoretically beneficial to the candiru because it is only vulnerable to predators for a short period of time.<ref name=":3" />

In most cases, the host fish do not seem to be badly wounded by this process. There is generally no observable damage to the gill filaments. However, relatively deep crescent or elliptical-shaped wounds with coagulated blood inside can be found beneath the gill cover.<ref name=":3" />

When starving, the candiru may resort to entering unusual orifices such as the nostril of a host fish. This behavior may relate to reported cases of these fish penetrating human orifices such as the urethra.<ref name=":3" />

==Alleged attacks on humans==
Although lurid [[anecdotal evidence|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. It is likely that, while the fish's spines can cause physical trauma, it merely poses as much danger of actually entering a human as any other fish of its size.{{cn|date=November 2024}}

===Historical accounts===
The earliest published report of candiru attacking a human host comes from German biologist [[Carl Friedrich Philipp von Martius|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.<ref>{{Cite web |last=Gonzalez |first=Alyssa |date=2023-03-20 |title=The Candiru: A Six-Inch SciCom Failure |url=https://www.talksciencetome.com/2023/03/20/the-candiru-a-six-inch-scicom-failure/ |access-date=2024-04-16 |website=Talk Science to Me |language=en-US}}</ref> 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.<ref>von Martius, C. F. P. 1829.Preface, p. viii, of van Spix, J. B., and Agassiz, L. Selecta Genera et Species Piscium ouos in Itinere ocr Brnsiliam annis 1817-20 Collcgit ... Dr. J. B. de Spix, etc. Monachii, 1829.</ref> Later experimental evidence has shown this to be false, as the fish actually hunt by sight and have no attraction to urine at all.<ref name="Spotte-etal">{{Cite journal |last1=Spotte |first1=Stephen |last2=Petry |first2=Paulo |last3=Zuanon |first3=Jansen A.S. |year=2001 |title=Experiments on the feeding behavior of the hematophagous candiru |journal=Environmental Biology of Fishes |volume=60 |issue=4 |pages=459–464 |doi=10.1023/A:1011081027565|s2cid=40239152 }}</ref>

Another report, from French naturalist [[Francis de Laporte de Castelnau|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."<ref>CASTELNAU, FRANCIS DE. 1855. Expedition dans les Partics Cent&es de I'AmPrique du Sud, 1843 a 1847. Animaux Nouveaux ou Rares-Zoology. Paris, 3: 50, p1. 24, fig. 4.</ref> 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.<ref name=Gudger/>

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. However, it was lodged in a native woman's vagina, rather than a [[male urethra]]. 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. Bach believed this was a remedy performed because of parasitism by candiru, but he was merely speculating, as he did not speak his patients' language.<ref>BWLENGER, G. A. 1898a. Exhibition of specimens, and remarks upon the habits of the siluroid fish, Vandellia cirrhosu. Proc. Zool. Sot. London [1897], p. 90 I.</ref> 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.<ref name=Gudger/>

In 1891, naturalist Paul Le Cointe provides a rare first-hand account of a candiru entering a human body, and like Lacerda's account, it involved the fish being lodged in the vaginal canal, not the urethra. Le Cointe supposedly removed the fish himself, by pushing it forward to disengage the spines, turning it around and removing it head-first.<ref>Le Cointe, Paul. 1922. L'Amazonie Bresilienne: Le Pays; Ses Inhabitants, scs Ressources. Notes et Statistiques jusqu'en 1920. Paris, II: 365.</ref>

However, the veracity of both Le Cointe's<ref>{{Cite web |date=2023-09-14 |title=What can the candiru (Vandellia cirrhosa) do? - Hektoen International |url=https://hekint.org/2023/09/14/what-can-the-candiru-vandellia-cirrhosa-do/ |access-date=2024-04-16 |website=hekint.org |language=en-US}}</ref> 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.<ref name=":0">{{Cite journal |last=Bauer |first=Irmgard L. |date=2013-03-01 |title=Candiru—A Little Fish With Bad Habits: Need Travel Health Professionals Worry? A Review |url=https://doi.org/10.1111/jtm.12005 |journal=Journal of Travel Medicine |publisher=International Society of Travel Medicine |volume=20 |issue=2 |pages=119–124 |doi=10.1111/jtm.12005 |pmid=23464720 |issn=1195-1982}}</ref>

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.<ref name="Gudger">{{cite journal|last= Gudger |first= E.W. |date=January 1930 |title= On the alleged penetration of the human urethra by an Amazonian catfish called candiru with a review of the allied habits of other members of the family pygidiidae |journal= The American Journal of Surgery |volume= 8 |issue= 1 |pages= 170–188 |publisher= Elsevier Inc. |type= Print |issn= 0002-9610|doi= 10.1016/S0002-9610(30)90912-9}}</ref>

===Modern cases===
To date, there is only one documented case of a candiru entering a human urethra, which took place in [[Itacoatiara, Amazonas|Itacoatiara]], [[Brazil]], in 1997.<ref name=Spotte-2002>{{Cite book |last1= Spotte |first1= Stephen |title= Candiru: life and legend of the bloodsucking catfishes |year= 2002 |publisher= Creative Arts Book Co. |location= Berkeley, Calif. |isbn= 0-88739-469-8 }}</ref> 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.<ref name=cecil>{{cite web |url= https://www.straightdope.com/21343429/can-the-candiru-fish-swim-upstream-into-your-urethra-revisited|title=Can the candiru fish swim upstream into your urethra (revisited)? |work=The Straight Dope |date=7 September 2001}}</ref> After traveling to [[Manaus]] on October 28, 1997, the victim underwent a two-hour [[urology|urological]] surgery by Dr. Anoar Samad to remove the fish from his body.{{cn|date=November 2024}}

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''.<ref name=Spotte-2002/> Spotte met Dr. Samad in person and interviewed him at his practice and home. 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]].<ref name=Spotte-2002/>{{rp|217}} Spotte and his colleague Paulo Petry took these materials and examined them at the institute, comparing them with Samad's formal paper. While Spotte did not overtly express any conclusions as to the veracity of the incident, he did remark on several observations that were suspicious about the claims of the patient and/or Samad himself.

* According to Samad, the patient claimed "the fish had darted out of the water, up the urine stream, and into his urethra." While this is the most popularly known legendary trait of the candiru, according to Spotte it has been known conclusively to be a myth for more than a century, as it is impossible because of simple fluid physics.<ref name=Spotte-2002/>{{rp|216}}
* The documentation and specimen provided indicate a fish that was 133.5&nbsp;mm in length and had a head with a diameter of 11.5&nbsp;mm. This would have required significant force to pry the urethra open to this extent. The candiru has no appendages or other apparatus that would have been necessary to accomplish this, and if it were leaping out of the water as the patient claimed, it would not have had sufficient leverage to force its way inside.<ref name=Spotte-2002/>{{rp|218}}
* Samad's paper claims the fish must have been attracted by the urine.{{cn|date=November 2024}} This belief about the fish has been held for centuries, but was discredited in 2001.<ref name="Spotte-etal" /> While this was merely speculation on Samad's part based on the prevailing scientific knowledge at the time, it somewhat erodes the patient's story by eliminating the motivation for the fish to have attacked him in the first place.
* Samad claimed the fish had "chewed" its way through the ventral wall of the urethra into the patient's [[scrotum]]. Spotte notes that the candiru does not possess the right teeth or strong enough dentition to have been capable of this.<ref name=Spotte-2002/>{{rp|214}} Additionally, the fish would most likely have died<ref name=":0" /> before it could have chewed even a somewhat large part of what was needed to reach it.
* Samad claimed he had to snip the candiru's grasping spikes off in order to extract it, yet the specimen provided had all its spikes intact.<ref name=Spotte-2002/>{{rp|218}}
* The cystoscopy video depicts traveling into a tubular space (presumed to be the patient's urethra) containing the fish's carcass and then pulling it out backwards through the urethral opening,<ref name=Spotte-2002/>{{rp|217}} something that would have been almost impossible with the fish's spikes intact.<ref name=Spotte-2002/>{{rp|215}}

When subsequently interviewed, Spotte stated that even if a person were to urinate while "submerged in a stream where candiru live", the odds of that person being attacked by candiru are "(a)bout the same as being struck by lightning while simultaneously being eaten by a shark."<ref>[https://books.google.com/books?id=G03t9cWFRSsC&pg=PA281&dq=%22simultaneously+being+eaten+by+a+shark%22 ''Dark Banquet: Blood and the Curious Lives of Blood-Feeding Creatures''] (via [[Google Books]]), by Bill Schutt, published by [[Random House]], 2008</ref>

== Taxonomy ==
Candiru belong to the family Trichomycteridae, which is monophyletic and contains 207 species. The taxonomic placement of this fish has long been debated, with the first proposed phylogenetic relationships of Trichomycteridae being proposed by [[Jonathan N. Baskin]] in 1973. Most proposed phylogenies have relied on morphological data, often placing ''Vandellinae'' and ''Stegophilinae'' as sister taxa among the subfamilies. 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. Relationships among ''Vandelliinae'' were strongly supported, and ''Vandellia'' was found to be the sister group of ''Plectrochilus''. The results of Fernández and Schaefer were fully congruent with previous statements based on morphological data.<ref name=":2" /> Nonetheless, the taxonomy of the Vandellia genus is still incomplete and hindered by the fact that several species within the genus have often been attributed the same name.<ref>{{cite journal |last1=Henschel |first1=Elisabeth |last2=Baskin |first2=Jonathan N. |last3=Collins |first3=Rupert |last4=Lujan |first4=Nathan K. |year=2024 |title=A Revised Diagnosis of the Blood-Feeding Candiru Genus ''Paravandellia'' (Siluriformes: Trichomycteridae: Vandelliinae) with Descriptions of Three New Species |journal=American Museum Novitates |issue=4024 |pages=1–36 |doi=10.1206/4024.1}}</ref>

== Discovery ==
''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. The Spanish name ''cañero'' is a derivative of ''carnero'', meaning flesh-eater.<ref>{{cite journal |last1=Myers |first1=George S. |year=1964 |title=A Brief Sketch of the History of Ichthyology in America to the Year 1850 |journal=American Society of Ichthyologists and Herpetologists |issue=1 |pages=33–41 |doi=10.2307/1440830|jstor=1440830 }}</ref>

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.<ref name=":1" />

== Conservation status ==
The remote habitat of the candiru, as well as the indigenous cultural customs surrounding its location, makes it difficult to study. The number of ''Vandellia cirrhosa'' in the wild is unknown, but there are no conservation efforts in place to protect these fish.{{cn|date=November 2024}}

One of its main habitats, the Purus River, is currently the main source of fish for human consumption in the most populous city of the Central Amazon, [[Manaus]]. This creates a huge pressure on fish stocks, which may be indirectly affecting the candiru by depleting its population of potential host fish.<ref name=":4" />

== References ==
{{Reflist}}

{{Taxonbar|from=Q1461873}}

[[Category:Fish of the Amazon basin]]
[[Category:Fish described in 1846]]
[[Category:Fish of Bolivia]]
[[Category:Pencil catfish of Brazil]]
[[Category:Freshwater fish of Colombia]]
[[Category:Freshwater fish of Ecuador]]
[[Category:Freshwater fish of Peru]]
[[Category:Parasites of fish]]
[[Category:Parasitic vertebrates]]
[[Category:Taxa named by Achille Valenciennes]]
[[Category:Trichomycteridae]]