Mexican Cave Fish (Astyanax mexicanus) – Profile | Facts

Mexican cave fish
(Last Updated On: April 13, 2021)

The Mexican tetra, or Mexican cave fish, scientific name  Astyanax mexicanus, is a fish having many names. The Mexican cave fish is also referred to as the blind cave fish, blind cave characin, and blind cave tetra is a freshwater fish. The species belongs to the family Characidae of the order Characiformes.

Mexican Cave Fish profile

The Mexican cave fish species of its genus, it’s naive to the Nearctic ecozone, originating within the decrease the Rio Grande and the Nueces and Pecos Rivers in Texas, in addition to the central and jap elements of Mexico.

A blind cave fish and two-floor fish from the identical species (Astyanax mexicanus) seek meals on the backside of an aquarium.

A minimum of this seems to be the case for a Mexican cave fish present in Mexico and the southern U.S. referred to as Astyanax mexicanus.

Descended from an eyed floor fish, over lengthy intervals of time the subterranean type of the identical species has tailored to darkness, accumulating new mutations that make them blind.

Consequently, Astyanax mexicanus is a freshwater fish that’s presently present in two varieties: cave and floor fish.

Each variety of Mexican cave fish is omnivores and roughly the identical dimension, round three inches lengthy (7.5 centimeters).

However, not like the floor fish, the cavefish are blind, albino, insomniacs, and have style buds on the skin of the decrease jaw. freshwater species of the week

The cave and floor fish can interbreed, which makes them a superspecies to research the genetic foundation of their variations.

Rising to a most whole size of Mexican cave fish of 12 cm (4.7 in), the Mexican tetra is of typical characin form, with unremarkable, drab coloration.

Its blind cave kind, nonetheless, is notable for having no eyes or pigment; it has a pinkish-white coloration to its physique (resembling an albino).

This Mexican cave fish, particularly the blind variant, in all fairness widespread amongst aquarists.

A. mexicanus is a peaceable species that spends most of its time in midlevel water above the rocky and sandy bottoms of swimming pools and backwaters of creeks and rivers of its native surroundings.

Coming from subtropical local weather, Mexican cavefish prefers water with 6.5–eight pH, a hardness of as much as 30 dB, and temperature variations of 20 to 25 °C (68 to 77 °F).

Within the winter, some populations of Mexican cavefish migrate to hotter waters. Its pure food regimen consists of crustaceans, bugs, and annelids, though in captivity it’s omnivorous.

The Mexican tetra has been handled as a subspecies of A. fasciatus, however this isn’t broadly accepted.

Moreover, the Mexican cave fish is usually acknowledged as a separate species, A. jordani, however, this straight contradicts phylogenetic proof.

Mexican cave fish

Mexican cave fish research

Mexican tetra in blind cave fish kind. A. mexicanus is legendary for its blind cave kind, which is thought by such names as blind cave tetra, Mexican cavefish (resulting in simple confusion with the Brazilian Stygichthys typhlops), blind cave characin, and blind cavefish.

Relying on the precise inhabitants, cave varieties can have degenerated sight or have a whole lack of sight and even their eyes.

The fish within the Pachón caves have misplaced their eyes utterly while the fish from the Micos cave solely have restricted sight. Mexican cave fish and floor fish are in a position to produce fertile offspring.

These fish can nonetheless, nonetheless, discover their method round by the use of their lateral traces, which are extremely delicate to fluctuating water strain.

Blindness in A. mexicanus induces disruption of early neuromast patterning, which additional causes asymmetries in cranial bone construction.

One such asymmetry is a bend within the dorsal area of their cranium, which is propounded to extend water to move to the other aspect of the face, functionally enhancing sensory enter and spatial mapping in the dead of night waters of caves.

At the moment, about 30 Mexican cave fish populations are identified, dispersed over three geographically distinct areas in a karst area of San Luis Potosí and much southern Tamaulipas, northeastern Mexico.

Among the many varied caves, inhabitants are a minimum of three with solely full cave varieties (blind and without pigment), a minimum of eleven with the cave, “regular” and intermediate varieties, and a minimum of one with each cave and “regular” varieties however no intermediates.

Research recommends a minimum of two distinct genetic lineages happen among the many blind populations, and the present distribution of populations arose by a minimum of 5 impartial invasions.

The eyed and eyeless types of A. mexicanus, being members of the identical species, are carefully associated and might interbreed making this species a wonderful mannequin organism for analyzing convergent and parallel evolution, regressive evolution in cave animals, and the genetic foundation of regressive traits.

Mexican cave fish

This, mixed with the benefit of sustaining the species in captivity, has made it probably the most studied cavefish and certain additionally probably the most studied cave organism total.

The blind and colorless cave type of A. mexicanus is usually acknowledged as a separate species, A. jordani, however, this leaves the remaining A. mexicanus as a paraphyletic species and A. jordani as polyphyletic.

The Cueva Chica Cave within the southern part of the Sierra del Abra system is the sort locality for A. jordani.

Different blind populations have been initially additionally acknowledged as separate species, together with antrobius described in 1946 from the Pachón Cave and hubbsi described in 1947 from the Los Sabinos Cave (each subsequently merged into jordani/mexicanus).

Probably the most divergent cave inhabitants of the Mexican cave fish are the ones in Los Sabinos.

One other cave-adapted inhabitants of Astyanax, various from the blind and depigmented to people exhibiting intermediate options, is thought from the Granadas Cave, a part of the Balsas River drainage in Guerrero, southern Mexico, however, it is part of A. aeneus (itself generally included in A. mexicanus).


The blind cave tetras seen within the aquarium commerce are all primarily based on inventory collected within the Cueva Chica Cave within the southern part of the Sierra del Abra system in 1936.

These have been despatched to an aquarium firm in Texas, who quickly began to distribute them to aquarists.

Since then, these have been selectively bred for his or her troglomorphic traits. As we speak giant numbers are bred at business services, particularly in Asia.

The blind cave tetra is a hardy species. Their lack of sight doesn’t hinder their skill to get meals.

They like subdued lighting with a rocky substrate, like gravel, mimicking their pure surroundings. They develop into semi-aggressive as they age, and are by nature educated fish.

Experiments have proven that conserving these fish in brilliant aquarium set-ups has no impact on the event of the pores and skin flaps that varieties over their eyes as they develop.

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