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The Mexican tetra (Astyanax mexicanus), also known as the blind cave fish, blind cave characin or the blind cave tetra, is a species of freshwater ray-finned fish belonging to the family Acestrorhamphidae, the American characins. This fish is found in the lower Rio Grande, and the Nueces and Pecos Rivers in Texas, into the Central Plateau and eastern states of Mexico. Maturing at a total length of about 12 cm (4.7 in), the Mexican tetra is of typical characin form, albeit with silvery, unremarkable scalation, likely an evolutionary adaptation to its natural environment.