Cardinal tetras are small fish, males grow to about 2.5 cm in length in the wild, but can attain lengths of 5 cm in an aquarium. This species is characterized by a horizontal neon blue stripe and deep red markings. The neon stripe of (Butler, 2003; "Tempting Terrific - The Tetras", 2004; "Poisson : Paracheirodon axelrodi", 2004; Butler, 2003; Bydzovsky, 2000; Fink and Weitzman, 1983; Froese, et al., 2004; Lundie, 2004)becomes iridescent because of external lighting. As the angle of light that strikes them changes, the color of the neon stripe turns from green to blue or vice versa. During the night, when no light hits the stripe, cardinal tetras are a transparent, brownish color. Cardinal tetras, as well as many other tetras, have a small adipose fin on their dorsal side at the tail end of their bodies. Cardinal tetras have a single row of dentary teeth.
Eggs hatch within 24 to 30 hours of fertilization. Fertilized fish eggs, in general divide by discoidal meroblastic cleavage. Because fish eggs are telolecithal (have a large percentage of yolk) cleavage can only take place in a small part of the egg. (Gilbert, 2003)
Female cardinal tetras release their eggs during the rainy season. The eggs become fertilized by the milt (sperm) of males in close proximity. Mating takes place at twilight during the rainy season. The male embraces the female while swimming. Fertilization is external. As the female scatters about 500 eggs into the water, males fertilize the eggs. ("Tempting Terrific - The Tetras", 2004; Norris and Chao, 2002)
Female cardinal tetras may release about 500 eggs. Once the eggs have been laid, they sink and some adhere to plants. Because cardinal tetra eggs are light sensitive, the only eggs that can develop into adult fish are released in a shaded river habitat. To breed cardinal tetras successfully in captivity, the pH should be between 5.5 and 6, the temperature should be at 24°C and the light should be dim. Fry are independent within 3 to 4 days of hatching. Both males and females reach sexual maturity by approximately 9 months of age. (Froese, et al., 2004; "Cardinal Tetra", 2002; "Tempting Terrific - The Tetras", 2004; "Poisson : Paracheirodon axelrodi", 2004; Butler, 2003; Froese, et al., 2004; Norris and Chao, 2002; "Cardinal Tetra", 2002)
Parent cardinal tetras take no care of their eggs or young. After eggs are released, some parent cardinal tetras may even eat some of their spawn. ("Tempting Terrific - The Tetras", 2004)
Cardinal tetras are able to live longer in captivity than in the wild. In the wild, they are expected to live about 1 year. In captivity, the life expectancy is about 5 years, although individuals may live as long as 10 years. ("Poisson : Paracheirodon axelrodi", 2004; "Cardinal Tetra", 2002)
Cardinal tetras are known to make small scale seasonal migrations upstream or downstream depending on the height of water during a particular season. (Bydzovsky, 2000)
The home range of these fish has not been reported.
Communication has not been described in this species. However, tactile communication occurs during mating. It is likely that these fish use tactile and visual cues as part of their communication, since they seem aware of the number of other cardinal tetras in a tank in captivity. ("Poisson : Paracheirodon axelrodi", 2004; Froese, et al., 2004; "Cardinal Tetra", 2002)
Little is known about how cardinal tetras perceive their environment. They use their eyesight and tactile cues and are able to perceive sound through the water.
The diet of cladocera (small, spherical moinids, daphnids, and macrothricids), as well as some copepods (benthonic Harpacticidae). Rotifera and Thecamoebae are included in the mesofauna that cardinal tetras eat. The types of algae that they eat include unicellular diatoms (Navicularia and Pinnularia), and some green algae (Chlamydomonas, Conjugatophyta, and Volvocaceae). Cardinal tetras sometimes feed on dead fish, eating the detritus of their muscular, proteinous, and membraneous tissues. individuals may also eat ants, Diptera larvae or pupae, mites, newly hatched shrimp, fungus, pieces of fruit, and fish larvae. ("The food spectrum of the cardinal - tetra (Paracheirodon axelrodi, Characidae) in its natural habitat", 2004)consists of very small crustaceans, mesofauna, eggs, algae, detritus, and some other types of prey. Most types of small crustaceans eaten are
The bright, neon, lateral stripe of cardinal tetras makes it difficult for predators to single out and attack an individual. Their schooling behavior also helps to protect individuals from predators. Although little is known on the specific predators of cardinal tetras, they likely fall prey to larger fish and other small to medium aquatic predators as adults, fry, and eggs. (Sharpie, 2004)
In relatively few cardinal tetras (6.3% of 80 dissected), existence of parasitic nematodes was found in the coelom, or stomach. Cardinal tetras serve as important predators of their small, invertebrate and zooplanktonic prey. They are important food sources, in all life stages, for larger predators. ("The food spectrum of the cardinal - tetra (Paracheirodon axelrodi, Characidae) in its natural habitat", 2004)
Cardinal tetras are often kept and enjoyed as a beautiful aquarium fish. Because of their peaceful nature, cardinal tetras are highly recommended for tanks with more than one species of fish. Most of the cardinal tetras sold come straight from South America because of the difficulty of breeding them in nature; between the years 1977 and 1981, an average of 12 to 17 million cardinal tetras were exported annually. (Bydzovsky, 2000; Froese, et al., 2004; Lundie, 2004)
has no known negative affect on humans.
Cardinal tetras are common in their native range, they are not considered threatened.
Tanya Dewey (editor), Animal Diversity Web.
Sarah Fintushel (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor.
living in the southern part of the New World. In other words, Central and South America.
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
flesh of dead animals.
uses smells or other chemicals to communicate
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the business of buying and selling animals for people to keep in their homes as pets.
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
an animal that mainly eats plankton
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
remains in the same area
offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
Oregon Zoo. 2002. "Cardinal Tetra" (On-line). Oregon Zoo Animal Fact Sheets. Accessed September 02, 2006 at http://www.oregonzoo.org/Cards/Amazon/cardinal.tetra.htm.
AquaBase.org. 2004. "Poisson : Paracheirodon axelrodi" (On-line). AquaBase.org. Accessed October 22, 2004 at http://www.aquabase.org/fish/view.php3?id=3.
2004. "Tempting Terrific - The Tetras" (On-line). The Goldfish Bowl. Accessed November 11, 2004 at http://www.thegoldfishbowl.co.uk/temptingtetras.html.
Instituto Nacional de Pesquisas da Amazônia. 2004. "The food spectrum of the cardinal - tetra (Paracheirodon axelrodi, Characidae) in its natural habitat" (On-line). Accessed October 24, 2004 at http://www.scielo.br/scielo.php?pid=S0044-59672004000100009&script=sci_arttext&tlng=en.
Butler, R. 2003. "Cardinal Tetra, Cardinal Neon http://fish.mongabay.com/species/Paracheirodon_axelrodi.html." (On-line). mongabay.com. Accessed October 23, 2004 at
Fink, W., S. Weitzman. 1983. Relationships of the Neon Tetras, A Group of South American Freshwater Fishes (Teleostei, Characidae), with Comments on the Phylogeny of New World Characiforms. Bulletin of the Museum of Comparative Zoology, 150: 339-395.
Froese, R., L. Malabarba, C. Binohlan. 2004. "Paracheirodon axelrodi" (On-line). fishbase.org. Accessed October 01, 2004 at http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=8195&genusname=Paracheirodon&speciesname=axelrodi.
Gilbert, S. 2003. Developmental Biology. 7th ed. Sunderland, Ma: Sinauer Associates, Inc.
Lundie, A. 2004. "Paracheirodon axelrodi" (On-line). FishProfiles.com. Accessed October 22, 2004 at http://www.fishprofiles.com/files/profiles/cardinal.xml.
Norris, S., N. Chao. 2002. Buy a Fish Save a Tree?. Conservation In Practice, 3: 30-35. Accessed November 11, 2004 at www.ufam.edu.br/~piaba/ arquivos/ProjectPiabaSummer02.pdf.
Sharpie, S. 2004. "Freshwater Aquariums Fish Trivia #1" (On-line). freshaquarium.about.com. Accessed October 24, 2004 at http://freshaquarium.about.com/library/weekly/aa011899a.htm.
Walker, I. 2004. The food spectrum of the cardinal - tetra (Paracheirodon axelrodi, Characidae) in its natural habitat. Acta Amazonia, 34/1: 69-73. Accessed November 07, 2004 at http://www.scielo.br/scielo.php?pid=S0044-59672004000100009&script=sci_arttext&tlng=en.