Mexican Tetra

• adaptaciónIt is born with eyes that stop developing and end up covered by skin, since in the total darkness of the caves they confer no advantage.
• GeneralThe same species has sighted populations in the rivers and blind ones in the caves.
• Cave and surface individuals can interbreed and produce fertile offspring: they are the same species, separated by a few hundred thousand years.
• The blind form makes up for the lack of sight with more taste buds over its body and a hypersensitive lateral line that lets it map the cave from pressure waves.
• They sleep far less than their surface relatives and tolerate very long fasts.
• It has two forms within the same species: a surface one with eyes and pigment and a cave one, blind and unpigmented; the two remain fully interfertile.
• Some 35 cave populations are known with no eyes or greatly reduced ones, and the loss of sight has happened independently several times.
• A study at Lund University calculated that keeping its sight costs a juvenile 15% more energy, which would explain the advantage of losing it where there is no light and food is scarce.
• The cave form has taste buds on the outside of its lower jaw and barely sleeps.

Skeleton type

Vertebrate - internal bony skeleton (bony fish)

Habitat and environment

Underground caves and surface rivers

Sources consulted: Wikipedia (es): Astyanax mexicanus

The pins mark the parks where its presence is documented.