Blind cavefish
Astyanax mexicanus jordani
FAMILY
Characidae
TAXONOMY
Astyanax mexicanus jordani Hubbs and Innes, 1936, San Luis Potosí, Mexico.
OTHER COMMON NAMES
English: Blind cave characin, blind cave tetra; German: Blinder Höhlensalmler; Spanish: Sardina ciega; Portuguese: Peixecaverna, Peixe-cego.
PHYSICAL CHARACTERISTICS
Maximum length 3.5 in (8.9 cm). The species evolved in the darkness of caves. Perhaps because of the absence of light in the environment, the body lacks pigments; instead, it is peachcolored with a silvery sheen. Has a complete lateral line along the body. Fins are colorless and transparent. Another characteristic attributed to the dark environment are vestigial eyes; the eye depressions are covered by skin and other tissue.
DISTRIBUTION
HABITAT
Subterranean lakes, streams, and pools of underground caves.
BEHAVIOR
Despite a lack of vision, this species exhibits exceptional navigation abilities. The lateral line is highly sensitive to vibrations, which allows the fish to find food and avoid obstacles as they swim. A solitary species, there is little interaction between individuals.
FEEDING ECOLOGY AND DIET
General, omnivorous feeders that primarily consume benthic invertebrates and algae. Use their excellent sense of smell to locate food items.
REPRODUCTIVE BIOLOGY
Spawns by broadcasting eggs. The male and female swim alongside each other near the surface of the water, with their ventral surfaces pressed together; the female scatters eggs, which are then fertilized by the male. The eggs fall to the bottom and hatch in two to three days. The larvae have normal eyes when they hatch, but these become enclosed in tissue after a few weeks.
CONSERVATION STATUS
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
Commonly kept in aquaria, but not as popular as most other characins. Studies of this species have provided useful insights into the evolution of eyes and sight, which can also help improve scientific understanding of human vision.
