Cardinal Tetra (Paracheirodon axelrodi)

Cardinal tetras, and their relatives the neon tetra, are a species of freshwater schooling fish native to South America. Their iridescent blue stripe is thought to work as a defense mechanism to avoid being eaten. The reflective stripe may disorientate predators, especially when many fish are swimming together, making it harder to pick out a single fish.

vii_genau on Flickr, Joachim S Muller on Flickr

Cardinal Tetra (Paracheirodon axelrodi)

Cardinal tetras are a species of freshwater fish native to the upper Orinoco and Negro Rivers of South America. Similarly to the popular neon tetra, they have an iridescent blue line running across the length of its body. 

Cardinal tetras are shoaling fish. This serves as a protective measure, as it is harder for predators to single out an individual. The flashing neon blues may act to further confuse predators.

Mike Kamermans on Flickr, Kristof Borkowski on Flickr

Cardinal Tetra (Paracheirodon axelrodi)
The reflective neon-blue stripe of the cardinal tetra, combined with its schooling tendency, confuses predators by making it hard to single out a fish.
Joachim S Mueller on Flickr

Cardinal Tetra (Paracheirodon axelrodi)

The reflective neon-blue stripe of the cardinal tetra, combined with its schooling tendency, confuses predators by making it hard to single out a fish.

Joachim S Mueller on Flickr

Cardinal tetra (Paracheirodon axelrodi)

Along with the closely related neon tetra, this small, shoaling amazon fish is brightly coloured with a band of electric blue and red. It is thought that the reflective stripe disorientates predators, making it harder to pick out a single fish.

Images: JJPhoto; National Geographic