Candiru are found exclusively in the upper Amazon River and Orinoco River basins in northern South America. ("Vandellia cirrhosa: Candiru", 2012; Berra, 2007; Cheng, 1986; Spotte, 2002; Uhlenbroek, 2011)
Candiru live in shallow, slow moving, acidic waterways with muddy or sandy bottoms. These demersal fish can be found burrowed in the riverbed most of the time, only emerging to feed or mate. (Froese and Torres, 2012; Piper, 2007; Spotte, 2002; Uhlenbroek, 2011)
- Aquatic Biomes
- rivers and streams
Candiru are small, thin catfish. They have no scales and their bodies are transluscent, becoming colored only after feeding. These fish have barbels near their mouths, which are lined with minute, needle-like teeth. Maximum total length for this species is 17 cm, though most specimens are much smaller. The body is narrow and cylindrical, with a slightly flattened head. Candiru have short, backward facing spines on their gill covers, which help to prevent it from being dislodged while feeding, and large black eyes (relative to body size), which are placed on top of the head. (Breault, 1991; Cheng, 1986; Harvey, 2008; Helfman and Collette, 2011; Piper, 2007; Uhlenbroek, 2011; de Pínna and Wosiacki, 2003)
- Range length
- 17 (high) cm
- 6.69 (high) in
- Average length
- 5 cm
- 1.97 in
There is currently no information available regarding development in this species. Generally speaking, catfish eggs are spherical in shape and are externally fertilized. Once sperm enters an egg, cell cleavage begins and the embryo starts to develop. Gestation time is unknown for this species. Young hatch with a visible yolk-sac, which acts as a food source during early development and is gradually absorbed, with post-yolk sac individuals resembling small adults. (Adriaens and Vandewalle, 2003; Piper, 2007)
Mating behaviors of candiru have not been observed in the wild. There is only one recorded instance of these fish spawning in captivity. In this record, a male fish swam around a female, driving her down toward the substrate. Eggs and sperm were released when the fish were in direct lateral contact with each other. (Kik, 2010; Spotte, 2002)
- Mating System
- polygynandrous (promiscuous)
There is very little information regarding the general reproductive behavior of this species. The only indication of a breeding season is the record of capture of a candiru in late December with ripe ovaries. In captive spawning, 4-5 eggs were released by the female at a time, with breeding taking place multiple times over the span of 3 days. None of the eggs produced were viable, however. There is also currently no information available regarding gestation time or size of young at birth. (Adriaens and Vandewalle, 2003; Kik, 2010; Spotte, 2002)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- It is assumed that candiru breed multiple times during their breeding season.
- Breeding season
- Breeding season for this species is unknown but females with ripe ovaries have been collected in December.
- Range number of offspring
- 4 to 15
There is no information regarding parental investment in this species. In captivity, eggs were laid with no nesting behavior and seemingly with no preference for substrate. Parents did not provide any investment beyond fertilization. (Kik, 2010; Spotte, 2002)
- Parental Investment
- no parental involvement
There is no information available regarding the lifespan of candiru, either in captivity or in the wild.
Outside of a wide breadth of knowledge on the feeding behavior of this species, little is known. Although they are often found buried in substrate, they actively feed during the day as well as at night. (Piper, 2007; Zuanon and Sazima, 2004)
There is no information currently available on the home range of this species.
Communication and Perception
Candiru likely use a combination of chemical and visual cues to locate hosts. It is hypothesized that candiru track the scent of ammonia and other excretions from potential prey, although this has not been definitively proven. Their eyes are quite large, which may indicate high visual acuity; however, candiru are typically found in turbid water where vision is limited, so eyesight is probably not the primary mode of host detection. Like most fish, candiru have a lateral line system which helps to alert them to movements in the water around them. (Froese and Torres, 2012; Spotte, 2002; Spotte, et al., 2001)
Candiru are parasites, feeding on the blood of other fish. When a candiru locates a host (through visual and chemical cues), it heads towards the gills, where it either forces itself under the operculum or waits for it to open naturally. Once past the operculum, these parasites latch onto the ventral or dorsal aortal arteries. Opercular spines help candiru stay attached to hosts' gills and aid in releasing blood. The host's blood pressure pumps blood straight into the candiru's mouth; these parasites do not "suck" blood as has been previously hypothesized. The length of a single blood meal is usually short, from 30-145 seconds. After feeding, candiru sink and burrow into the river bottom. Other species of larger catfish (Brachyplatystoma vaillantii, Pseudoplatystoma sp.) and characins (Piaractus brachypomus, Pygocentrus nattereri, Salminus brasiliensis, Colossoma macropomum, Brycon spp.) are also known to be hosts for candiru. Colossoma macropomum have been observed to exhibit defense mechanisms against candiru attacks, such as tightening their operculum and using their fins to sweep the parasites away. (Kelley and Atz, 1964; Spotte, 2002; Uhlenbroek, 2011; Zuanon and Sazima, 2004)
- Animal Foods
Although there are no reports of candiru predators, it is very likely that larger carnivorous fish may feed on them.
- Ecosystem Impact
- Tambaqui (Colossoma macropomum)
- Amazonian pacu (Piaractus brachypomus)
- Red-bellied piranha (Pygocentrus nattereri)
- Golden dorado (Salminus brasiliensis)
- Brachyplatystoma vaillantii (Order Siluriformes, Class Actinopterygii)
- Brycon sp. (Order Characiformes, Class Actinopterygii)
- Pseudoplatystoma sp. (Order Siluriformes, Class Actinopterygii)
Economic Importance for Humans: Positive
There are no known positive effects of candiru to humans outside of scientific research. (de Pínna and Wosiacki, 2003)
- Positive Impacts
- research and education
Economic Importance for Humans: Negative
It is possible for candiru to parasitize humans, though this is very rare. There have been reports of Candiru swimming up the urethra of men and women who urinate while in the water. It is believed that attacks are accidental, as they die once inside the urethra. Although there are many stories published, it is difficult to assess their accuracy and validity, as candiru are only found in a region where scientific researchers and qualified doctors are not always available. (Berra, 2007; Brealt, 1991)
- Negative Impacts
- bites or stings
Numbers of candiru are unknown, but there are no conservation efforts to evaluate or maintain current population levels. (IUCN, 2012)
Kiersten Newtoff (author), Radford University, Jeremy Wright (editor), University of Michigan-Ann Arbor.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
active at dawn and dusk
- active during the day, 2. lasting for one day.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- external fertilization
fertilization takes place outside the female's body
union of egg and spermatozoan
mainly lives in water that is not salty.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
an animal that mainly eats blood
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
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Berra, T. 2007. Freshwater Fish Distribution. Chicago, IL: The University of Chicago Press.
Brealt, J. 1991. Candiru: Amazonian parasitic catfish. Journal of Wilderness Medicine, 2: 304-312.
Breault, J. 1991. Candiru: Amazonian parasitic catfish. Journal of Wilderness Medicine, 2: 304-312.
Cheng, T. 1986. General Parasitology. Orlando, FL: Academic Press.
Froese, R., A. Torres. 2012. "Vandellia cirrhosa (Valenciennes, 1846): Candiru" (On-line). Fishbase. Accessed March 01, 2013 at http://www.fishbase.org/summary/Vandellia-cirrhosa.html.
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IUCN, 2012. "The IUCN Red List of Threatened Species" (On-line). Accessed March 01, 2013 at http://www.iucnredlist.org/search.
Kelley, W., J. Atz. 1964. A pygidiid catfish that can suck blood from goldfish. Copeia, 1964/4: 702-704.
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Piper, R. 2007. Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Westport, CT: Greenwood Press.
Spotte, S. 2002. Candiru: Life and Legend of the Bloodsucking Catfishes. Berkeley, CA: Creative Art Books Company.
Spotte, S., P. Petry, J. Zuanon. 2001. Experiments on the feeding behavior of the hematophagous candiru, Vandellia cf. plazaii. Environmental Biology of Fishes, 60/4: 459-464.
Uhlenbroek, C. 2011. Animal Life: Secrets of the Animal World Revealed. New York, NY: DK Publishing.
Zuanon, J., F. Bockmann, I. Sazima. 2006. A remarkable sand-dwelling fish assemblage from central Amazonia, with comments on the evolution of psammophily in South American freshwater fishes. Neotropical Ichthyology, 4/1: 107-118.
Zuanon, J., I. Sazima. 2004. Vampire catfishes seek the aorta not the jugular: Candirus of the genus Vandellia (Trichomycteridae) feed on major gill arteries of host fishes. Journal of Ichthyology and Aquatic Biology, 8/1: 31-36. Accessed March 01, 2013 at http://www.ecoevo.com.br/publicacoes/pesquisadores/ivan_sazima/vampirecatfish_2004.pdf.
de Pínna, M., W. Wosiacki. 2003. Trichomycteridae (pencil or parasitic catfishes). Pp. 270-290 in R Reis, S Kullander, C Ferraris, eds. Checklist of the Freshwater Fishes of South and Central America. Brazil: EDIPUCRS.