Mexican tetra
Channel: 宇宙のすべての知識 プリンシピア
Date: 2019-01-18

Mexican tetra, by Wikipedia https://en.wikipedia.org/wiki?curid=3209 / CC BY SA 3.0

#IUCN Red List least concern species
#Tetras
#Astyanax (fish)
#Freshwater fish of Mexico
#Freshwater fish of the United States
#Cave fish
#Blind animals
#Least concern biota of the United States
#Fish described in 1853
Mexican tetra

The Mexican tetra or blind cave fish ("Astyanax mexicanus") is a freshwater fish of the family Characidae of the order Characiformes. The type species of its genus, it is native to the Nearctic ecozone, originating in the lower Rio Grande and the Neueces and Pecos Rivers in Texas, as well as the central and eastern parts of Mexico.

Growing to a maximum total length of , the Mexican tetra is of typical characin shape, with unremarkable, drab coloration. Its blind cave form, however, is notable for having no eyes or pigment; it has a pinkish-white color to its body (resembling an albino).

This fish, especially the blind variant, is reasonably popular among aquarists.

"A. mexicanus" is a peaceful species that spends most of its time in midlevel water above the rocky and sandy bottoms of pools and backwaters of creeks and rivers of its native environment. Coming from a subtropical climate, it prefers water with 6.5–8 pH, a hardness of up to 30 dGH, and a temperature range of . In the winter, some populations migrates to warmer waters. Its natural diet consists of crustaceans, insects, and annelids, although in captivity it is omnivorous.

The Mexican tetra has been treated as a subspecies of "A. fasciatus", but this is not widely accepted. Additionally, the blind cave form is sometimes recognized as a separate species, "A. jordani", but this directly contradicts phylogenetic evidence.

"A. mexicanus" is famous for its blind cave form, which is known by such names as blind cave tetra, blind tetra (leading to easy confusion with the Brazilian "Stygichthys typhlops"), blind cave characin and blind cavefish. Depending on the exact population, cave forms can ...