X Ray fish – Reproduction, Habitat, Diet, Anatomy

SpeciesP. maxillaris
NicheAquatic fish
Length1.6-1.9 in (3.2-5 cm)
Lifespan2-5 years
Social StructureSchooling
Conservation StatusNot listed (common)
Preferred HabitatFreshwater ponds and lakes in South America
Average Spawn Size350
Main Prey SpeciesWorms, insects, small crustaceans
PredatorsLarger fish
  • The X-Ray Fish is a small fish that lives in the Amazon basin in South America. It swims in groups.
  • They are also called the Golden Pristella Tetra, the X-Ray Tetra, and the Water Goldfinch. Their skin is clear, like an X-ray, so you can see their organs and skeleton.
  • The largest size of an X-Ray Fish is 1.9 inches, and females are slightly bigger than males.
  • It has black, white, and yellow stripes on its dorsal and anal fins that make it stand out. Its skin is see-through, so you can see how its bones are arranged inside.
  • Even though it is the only member of its genus, the X-ray fish is very similar to about 100 other South American Tetra species.
  • It is also one of the most popular freshwater aquarium fish around the world.

X-Ray Tetra Anatomy and Appearance

  • The X-Ray Tetra fish stands out from the crowd due to its transparent skin, which makes the fish’s vertebrae easily discernible.
  • X-Ray Tetras have scales that are a very pale silvery yellow, almost a golden hue in certain lighting.
  • Besides its re-tipped tail, the X-Ray Tetra is easily recognisable by its contrasting yellow, black, and white striped dorsal and anal fins.
  • Small as they are, these fish have an impressively sensitive sense of hearing because to a bone internal device called the Weberian apparatus (this bony structure is also found in many of their relatives).
  • Females are slightly larger and more rounded than the more slender males, but otherwise the sexes look identical.

Behaviour and Lifestyle

  • The X-Ray Tetra, like many other small, brightly coloured fish, lives in schools in the water’s zone halfway between the bottom and the middle.
  • They are remarkably tranquil, and their coexistence with other species is generally tolerated.
  • Among Tetra species, the X-Ray Tetra is among the most flexible since it thrives in a wide range of water conditions, from acidic to alkaline, in both fresh and brackish water.
  • Tank-kept X-Ray Tetra have been seen to rapidly shift from calm to fearful in the presence of larger, predatory fish, with the same behaviour being seen when the school size is inadequate.

Distribution and Habitat of X Ray fish

  • X-Ray fish are indigenous to the coastal Amazon regions of Brazil, Guyana, and Venezuela.
  • In contrast to most other tetras, these fish can survive in the brackish waters that are common in this area.
  • On the other hand, they can also flourish in more typical freshwater settings, such as streams and rivers during the dry season and flooded marshlands during the wet.

Diet and Predators of X Ray fish

  • The X-ray fish’s diet includes both animal and plant matter. The tetra’s diet consists primarily of small crustaceans, such as a variety of worms, aquatic bug larvae, and shrimp-like creatures.
  • They are mostly carnivorous, but will supplement their diet with plants and algae if necessary.
  • They are easy prey for a wide variety of predators because of their small size.
  • Even the X-ray tetra is vulnerable to larger predatory fish. Amphibians like frogs, as well as some birds and snakes, provide a similar danger.
  • Many predatory species require their prey to be swimming near the water’s surface before they can catch them, hence X-Ray fish and other similar species are typically located at the upper or bottom of the water column.


  • The X-Ray fish is able to enter areas that would normally be inaccessible to it due to the flooding that occurs during the rainy season.
  • This boosts food availability and provides easier access to breeding grounds. The X-Ray fish has adapted to breed during this time of year.

Courtship and Copulation

  • The X-ray fish lays eggs rather than having live births like some of its relatives.
  • As the floodwaters cover the grasslands and marshes, the X-ray fish will release 300 to 400 eggs among the individual grass blades and other plants.
  • Within a day, the eggs will have hatched, and the fry will be able to swim freely. By the time they’re able to get their hands on more and more food, they’ve reached sexual maturity and are marked as adults.
  • In the wild, the average lifespan is only three to four years.
  • The average lifespan of a fish in the wild is 5-7 years, but in an aquarium it can be as much as 7-8 years. One of the reasons these fish are so common in aquariums is their rapid rate of reproduction.


  • The X-ray fish is still around, and rather widespread, but it and its ecosystem are in danger due to the rapid destruction of its natural environment.
  • The widespread adoption of illicit forestry activities, typically to provide pasture for livestock, is largely to blame.
  • Along with pollution, this poses a serious risk to the X-ray fish’s native environments in the Amazon Rainforest.

Facts about the X-Ray Fish

The X-Ray fish has quickly become a top pick for aquarium keepers everywhere thanks to its unusual look and rapid reproduction rate. Aside from the species’ illustrious skin transparency, however, there are many more interesting biological ideas to investigate.

Weberian Apparatus

  • The Weberian apparatus, an internal bony structure, is one of the most interesting aspects of this tiny fish.
  • This is similar to the way in which the vertebrae of closely related species function, allowing sound to be transmitted through the body and picked up by the inner ear.
  • In general, the Weberian apparatus has two components, the pars sustentaculum, which consists of many specially modified anterior vertebrae, and the pars auditum, which is the moveable section and is also known as the Weberian ossicles.
  • This unusual anatomy, in conjunction with the air in the X-Ray fish’s swim bladder, provides the fish with exceptional hearing, which helps them escape predators and locate prey.

Invisibility Cloak

  • The X-ray fish gets its common name from the fact that it can be seen through. However, it serves a specific function because, like many other aspects of our anatomy, it has evolved over time.
  • Given that it makes them less visible to most of their predators, it probably helps them avoid being eaten.
  • This is because their skin is translucent and shimmers in the light, just like the water in which they live.
  • Because of this and the fact that parts of their fins are marked with yellow, black, and white, these fish can be easy to miss, especially when they are hiding among the grasses and other flora at the bottom of the bodies of water in which they often live.

World Traveller

  • Tetras are a standard aquarium fish. Some of them are distinguished from others by special characteristics, such as ‘neon’ strips of iridescence along their sides.
  • However, some species, like the X-Ray fish, have transparent skin. They are also exceptionally productive.
  • They also have a lengthy lifespan and high durability. They can live for up to 8 years with minimum maintenance and attention if given a large fish tank free of predatory species and a few companions with which to socialise.
  • This is how this tiny fish, originally from the streams and marshes of the South American coast, has spread all over the world.

Relationship with Humans of X-Ray fish

  • Among aquarium fish, tetras are among the most common. Some of them have distinctive markings, such ‘neon’ streaks of iridescence down their sides.
  • The skin of the X-Ray fish, for example, is so thin that it can be seen through using X-ray equipment. As an added bonus, their production is through the roof.
  • As an added bonus, they have a decent lifespan and resilience. They can live for up to eight years with only minimal maintenance and attention if given a large enough fish tank free of predatory species and a few others to socialise with.
  • As a result, this little fish, which is endemic to the streams and marshes of South America’s coast, has spread all over the globe.

Predators and Threats of X-Ray fish

  • X-Ray Tetras should not be housed with larger, predatory fish due to their small size, but they will happily coexist with other small, schooling fish in an aquarium.
  • While larger fish and frogs are the primary predators of X-Ray Tetra in the wild, birds and snakes pose a hazard to those that swim near the water’s surface.
  • Some believe that rising water pollution and habitat loss pose the greatest threat to populations.

1 thought on “X Ray fish – Reproduction, Habitat, Diet, Anatomy”

  1. While larger fish and frogs are the primary predators of X-Ray Tetra in the wild, birds and snakes pose a hazard to those that swim near the water’s surface.


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