墨西哥盲鱼 · Blind Cave Tetra

Overview

Astyanax mexicanus includes both a normally sighted surface form and the pale, eyeless cave form familiar in aquariums. The latter navigates and feeds effectively without vision. It is generally hardy and manageable, although very timid or slow companions are poor choices.

Distribution & habitat

The species ranges from Texas and New Mexico through Mexico to Guatemala. Only Mexico supports the eyeless cave populations. Surface fish occupy diverse rivers, streams, ponds, and lakes, whereas the blind form lives underground.

Aquarium setup

The cave form needs no particular decoration or shelter arrangement and generally leaves plants undamaged. For a cave-inspired display, combine a dark bottom with taller rocks along the rear and sides and lower pieces toward the center. Subdued illumination can complete the effect. Ordinary aquarium layouts are also suitable.

Diet & feeding

Combine good dry foods with generous variety from small live and frozen items. The fish can locate food through senses other than sight. Occasional nips during feeding are associated with its searching behavior and need not indicate deliberate aggression.

Behaviour & compatibility

It fits many community aquariums, provided exceptionally shy or sluggish fishes are excluded. It is not strongly schooling, but usually fares better with company; maintain at least four individuals.

Sexual dimorphism

Females tend to grow larger and have a fuller abdomen. Their anal fin margin is straight, while the male's is slightly curved.

Breeding

Protect eggs with mesh raised roughly a centimeter above the bottom of a separate spawning aquarium, and install a sponge filter. Condition males and females apart, then move a well-prepared pair in during the evening. Spawning usually follows by morning. Remove adults as soon as eggs appear; if none are visible after about a day, try another pair.

A female can produce around a thousand white eggs, whose appearance can be mistaken for infertility. Hatching takes approximately one day. Another five to seven days pass before the yolk is absorbed and free swimming begins. Offer microscopic food for roughly the first week, then introduce newly hatched brine shrimp and suitably fine dry food. Some cannibalism can occur among the young. Early fry have visible eyes that subsequently fail to develop normally and recede beneath tissue.

Notes

The lateral line detects pressure changes and allows the blind form to learn its surroundings quickly. Faster swimming in a new layout may help it gather that information. Aquarium supplies largely come from farmed cave-form fish; surface populations are seldom represented in trade.