When first discovered in the 1930s, these eyeless, pigmentless fish were assigned their own genus, Anoptichthys. Since then, ichthyologists have determined they are at least 30 genetically isolated populations of the Mexican tetra, which is normally a silvery fish with well-developed eyes that is found north to the Rio Grande Valley in Texas. Fish collected in one cave, la Cueva Chica, in San Luis Potosi in the 1940s, are the ancestors of the fishes made available by commercial breeders to home aquarists, public aquariums and zoos.
This popular aquarium fish was unknown to science until 1956, when ichthyologists at the Smithsonian Institution and Stanford University published descriptions a day apart. It took a meeting of the International Commission on Zoological Nomenclature to determine the Smithsonian had published first. Found only in the Rio Negro and Orinoco Rivers, they are provided both through ecologically sustainable collecting in Brazil and fish farms in Asia and Europe.