# X-ray Tetra (*Pristella maxillaris*)

> The X-ray tetra is a small, translucent freshwater fish from the Amazon basin whose see-through body reveals its backbone and a silvery swim-bladder capsule. Hardy and peaceful, it lives in large schools, eats small invertebrates and plant matter, and usually lives 3 to 5 years.

- **Category:** Fish
- **Conservation status (IUCN):** Least Concern
- **Range:** Clearwater and coastal rivers and floodplains of the Amazon and Orinoco basins in South America.
- **Canonical page:** https://globalanimalguide.org/animals/x-ray-tetra/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Actinopterygii
- **Order:** Characiformes
- **Family:** Characidae
- **Genus:** Pristella

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Pristella maxillaris |
| Diet | Omnivore (small invertebrates, plant matter) |
| Habitat | Coastal Amazon rivers and floodplains |
| Lifespan | 3–5 years |
| Weight | Under 1 g |
| Length | Up to about 5 cm (2 in) |
| Conservation status | Least Concern (IUCN) |

## A transparent body

The X-ray tetra gets its name from its almost transparent body, through which you can see the spine and a silvery, bullet-shaped capsule that protects its swim bladder. The transparency works as camouflage in sunlit, open water, making the fish hard for predators to pick out.

## Safety in schools

X-ray tetras are shoaling fish that feel secure in groups, moving and turning together in loose schools. A school confuses predators and lets the fish spot danger sooner, which is why they are most comfortable and colorful when kept in numbers.

## A hardy survivor

Unusually for an Amazon tetra, this species tolerates a wide range of water conditions, including the slightly brackish coastal floodplains where many fish cannot live. That toughness has made it both a successful wild fish and a long-time favorite in home aquariums.

## Diet and range

X-ray tetras are omnivores that pick at tiny invertebrates, insect larvae, and bits of plant matter. They live in the rivers and seasonally flooded lowlands of the Amazon and Orinoco basins in northern South America and remain common in the wild.

## Frequently asked questions

### Why is it called an X-ray tetra?

The X-ray tetra has a nearly transparent body, so you can see its backbone and a silvery swim-bladder capsule through its skin, as if looking at an X-ray.

### How big do X-ray tetras get?

X-ray tetras are tiny, growing to only about 5 cm (2 in) in length.

### What do X-ray tetras eat?

They are omnivores that eat small invertebrates, insect larvae, and plant matter, foraging in open water and near the bottom.

### Where do X-ray tetras live?

X-ray tetras live in the Amazon and Orinoco river basins of South America, including slightly brackish coastal floodplains.

### Are X-ray tetras endangered?

No. X-ray tetras are hardy and widespread and are listed as Least Concern.

## Sources

- [IUCN Red List — Pristella maxillaris.](https://www.iucnredlist.org/search?query=Pristella%20maxillaris&searchType=species)
- [Animal Diversity Web — Pristella maxillaris. University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Pristella_maxillaris/)
- [Wikipedia — X-ray Tetra.](https://en.wikipedia.org/wiki/Pristella_maxillaris)

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Source: Global Animal Guide (https://globalanimalguide.org/animals/x-ray-tetra/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.