Neon Tetra

• Its blue stripe is not a pigment but a structure: reflective cells holding plates of guanine crystals that split the light, and the fish can change their angle, so the colour fades at night or when it is unwell.
• In the gloom of the blackwater streams that stripe works as a recognition signal that holds the shoal together.
• It is one of the most heavily traded ornamental fish on the planet, today bred almost entirely on farms in South-East Asia.
• It does not occur in the white-water rivers of Andean origin, only in black or clear waters stained by the humic acids of leaf litter.
• Its bright blue stripe may be a defence: in black water it is barely visible except from one particular angle, and it casts reflections on the underside of the surface that would confuse predators.
• It is one of the best-selling aquarium fish in the world, at close to two million individuals a month in the United States alone.
• In darkness or at rest the colours fade strikingly, because the reflective plates in its cells change state.

Skeleton type

Vertebrate - internal bony skeleton (bony fish)

Habitat and environment

Shaded blackwater streams of the western Amazon basin

Gestation / incubation

The eggs hatch in around 24 hours

Sources consulted: Wikipedia (es): Paracheirodon innesi