X-Ray Tetra

Pristella maxillaris

Last updated: April 4, 2023
Verified by: AZ Animals Staff
© Richard Bartz / Creative Commons / Original

Yellow, black and white striped fins!


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X-Ray Tetra Scientific Classification

Kingdom
Animalia
Phylum
Chordata
Class
Actinopterygii
Order
Characiformes
Family
Characidae
Genus
Pristella
Scientific Name
Pristella maxillaris

Read our Complete Guide to Classification of Animals.

X-Ray Tetra Conservation Status

X-Ray Tetra Locations

X-Ray Tetra Locations

X-Ray Tetra Facts

Prey
Worms, Insects, Small Crustaceans
Name Of Young
Fry
Group Behavior
  • School
Fun Fact
Yellow, black and white striped fins!
Estimated Population Size
Abundant
Biggest Threat
Water Pollution
Distinctive Feature
Striped fins and translucent skin
Other Name(s)
Golden Pristella Tetra, Water Goldfinch
Optimum pH Level
6.0 - 7.0
Incubation Period
24 hours
Age Of Independence
Immediately
Average Spawn Size
350
Habitat
Amazon coastal waters
Predators
Larger Fish, Frogs, Birds
Diet
Omnivore
Lifestyle
  • Diurnal
Common Name
X-Ray Tetra
Number Of Species
1
Location
Brazil, Guiana, Guyana, and Venezuela
Slogan
Yellow, black and white striped fins!
Group
Fish

X-Ray Tetra Physical Characteristics

Color
  • Yellow
  • Black
  • White
  • Silver
Skin Type
Scales
Lifespan
2 - 5 years
Height
3.2cm - 5cm (1.6in - 1.9in)
Age of Sexual Maturity
5 - 8 months

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The X-Ray Tetra is a small species of schooling fish that is naturally found in the Amazon River’s coastal waters in South America. The X-Ray Tetra fish is also known as the Golden Pristella Tetra and the Water Goldfinch beacuse of the faint golden coloration of their translucent skin.

Scientific Name and Classification

The X-Ray tetra was first described by Albert Ulrey in 1894 and has since become one of the most popular freshwater fish kept in aquariums today. Although the X-Ray tetra (Pristella maxillaris) is the only known species in its genus, it is closely related to other small and colorful South American fish, including the nearly 150 other tetra species. Among these other types of tetra are:

  • Neon Tetra (Paracheirodon innesi)
  • Rainbow Tetra (Nematobrycon lacortei)
  • Bloodfin Tetra (Aphyocharax anisitsi)
  • Emperor Tetra (Nematobrycon palmeri)
  • Buenos Aires Tetra (Hyphessobrycon anisitsi)
  • Lemon Tetra (Hyphessobrycon pulchripinnis)
  • Ember Tetra (Hyphessobrycon amandae)
  • Congo Tetra (Phenacogrammus interruptus)
  • Black Neon Tetra (Hyphessobrycon herbertaxelrodi)
  • Ruby Tetra (Axelrodia riesei)

For a description and pictures of these ten species, click here.

Anatomy and Appearance

The most distinctive feature of the X-Ray Tetra fish is the translucent layer of skin that covers its small body, which allows the fish’s backbone to be clearly seen. The scales of the X-Ray Tetra are a silvery-yellowish color that is very faint, looking almost golden in some lights. The X-Ray Tetra also has a red-tipped tail and strikingly striped dorsal and anal fins that are yellow, black, and white in color.

This is a relatively small species of fish (1.5 inches) that actually has a bony internal structure known as the Weberian apparatus, which is used in picking up sound waves and contributes to the X-Ray fish’s acute sense of hearing (this bony structure is also found in many of their relatives).

Females are generally slightly larger and rounder than the more slender males, although the two are very similar in appearance.

Distribution and Habitat

The X-Ray Tetra is found in the Amazonian coastal waters of Brazil, Guyana, and Venezuela in South America. They differ greatly from other Tetra species as they are able to tolerate the harder brackish water closer to the coast, as well as their usual freshwater environments. They inhabit clear-water streams and tributaries during the dry season, and with the coming of the rains, the X Ray fish then move into the flooded marshlands where the water is softer and more acidic. It is during the wet season that the X-Ray Tetra breed as they have better water conditions and a higher abundance of food.

Behavior and Lifestyle

Like many other small, colorful fish, the X-Ray Tetra is a schooling species inhabiting the region between the bottom and middle of the water as a group. They are incredibly peaceful and tolerant of other species in their habitats. The X-Ray Tetra is one of the most adaptable species of Tetra as it can inhabit both fresh and brackish water, in both acidic and alkaline conditions. It is widely observed that those X-Ray fish that are kept in tanks can change quickly from being peaceful to becoming skittish in the presence of larger, predatory fish, with the same behavior known to be displayed if the school size is not big enough.

Interesting Facts and Features

The Weberian apparatus (the bony structure) in the X-Ray Tetra’s body works by transmitting sound waves that have been received by the swim bladder, sending them through its vertebrae, and then taking them to the inner ear. The end result is that the X-Ray Tetra has excellent hearing.

The transparency of the skin is thought to be a form of protection as predators find it much harder to spot them (along with their light yellow markings) amongst the dense vegetation and shimmering water. Not only is the yellowish X-Ray Tetra popular in tanks, but an albino version of the species is also now commonly found in artificial communities worldwide.

Reproduction and Life Cycles

During the rainy season, the X-Ray Tetra return to the flood-lands to spawn. Unlike many similar fish who give birth to live young, the female X-Ray Tetra lays between 300-400 eggs by scattering them among the vegetation. When it is ready to spawn, the see-through skin means that the eggs can also be easily seen. X-Ray Tetra fry begin to hatch as early as 24 hours later and become free swimming within a few days. Once able to swim, the small and dull white young are able to find better food sources and soon develop their characteristic adult markings. X-Ray fish usually live for three or four years in the wild but can get to older ages in captivity.

Diet and Prey

Like many other small species of fish that live in the Amazon River, the X-Ray Tetra is an omnivorous animal whose diet is made up of both animals and plants. X-Ray Tetra primarily hunt worms, insects, and small crustaceans that live close to the river bed. Its fry feed on insect larvae. Although it is also known to supplement tits diet with aquatic plants, it is predominantly a micro-predator that feeds on small invertebrates. In artificial communities, X-Ray Tetra needs a variety of food sources, including brine shrimp and bloodworms alongside the standard flakes and pellets to ensure that it has a fully nutritious diet.

Predators and Threats

The small size of the X-Ray Tetra means that it should not be kept in the same aquarium as larger, predatory fish, but it can co-inhabit the tank peacefully with other small, schooling fish that pose no threat. In the wild, X-Ray Tetra are preyed upon by a number of aquatic predators, including larger fish and frogs, and it is threatened by birds and snakes if close to the water’s surface. Its populations are thought to be the most under threat from rising pollution and habitat loss in general.

Relationship with Humans

Since it was first described in 1894, this unique animal has been the subject of much fascination because of its nearly transparent body. The X-Ray Tetra is now one of the most popular species of tropical fish to be kept in household tanks, mainly due to the ease of care since they are hardy, adaptable and undemanding. The fast breeding rate is also thought to be one of the reasons why this fish has become so popular. Today, aquarium X-Ray Tetra do not come from the wild but are commercially farmed for the trade, mainly in Eastern Europe and in the Far East.

Conservation Status and Life Today

The X-Ray Tetra has not been listed on the IUCN Red List as a species that is under threat in its environment. However, increasing industry in the Amazon Basin means that there has been an increase in the levels of pollution in the water and therefore a decrease in water quality, leading to slight population declines in certain areas.

View all 13 animals that start with X

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X-Ray Tetra FAQs (Frequently Asked Questions) 

Are X-Ray Tetras herbivores, carnivores, or omnivores?

X-Ray Tetras are Omnivores, meaning they eat both plants and other animals.

What Kingdom do X-Ray Tetras belong to?

X-Ray Tetras belong to the Kingdom Animalia.

What phylum to X-Ray Tetras belong to?

X-Ray Tetras belong to the phylum Chordata.

What family do X-Ray Tetras belong to?

X-Ray Tetras belong to the family Characidae.

What order do X-Ray Tetras belong to?

X-Ray Tetras belong to the order Characiformes.

What is another name for the X-Ray Tetra?

The X-Ray Tetra is also called the golden pristella tetra or water goldfinch.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.

Sources
  1. David Burnie, Dorling Kindersley (2011) Animal, The Definitive Visual Guide To The World's Wildlife
  2. Tom Jackson, Lorenz Books (2007) The World Encyclopedia Of Animals
  3. David Burnie, Kingfisher (2011) The Kingfisher Animal Encyclopedia
  4. Richard Mackay, University of California Press (2009) The Atlas Of Endangered Species
  5. David Burnie, Dorling Kindersley (2008) Illustrated Encyclopedia Of Animals
  6. Dorling Kindersley (2006) Dorling Kindersley Encyclopedia Of Animals
  7. About X-Ray Tetra, Available here: http://animal-world.com/encyclo/fresh/characins/pristella.php
  8. Keeping X-Ray Tetra, Available here: http://www.aboutfishonline.com/articles/xraytetra.html
  9. X-Ray Tetra Information, Available here: http://www.seriouslyfish.com/profile.php?genus=Pristella&species=maxillaris&id=496

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