The blind cave tetra Astyanax mexicanus has developed without eyes or pigment after countless
years of the species living and reproducing in total darkness.
They aren’t truly aggressive, but they are a tiger barbs. The species is found in caves in
little too tough to be kept with the smaller, Mexico and Texas, where it thrives in the
more peaceful tetras. They can be kept with dark waters.
jewel tetras and Buenos Aires tetras, and So why did the fish go blind? Not only
they are about at the aggression level of are they blind, but they lack pigment,
and that is quite typical of other eyeless
species that are descended from countless
ancestors that found their niche in areas
of total darkness. The eyes and pigment
aren’t needed, of course, in such dark
habitats, but why do the fish actually lose
these features? The usual theory is that
eyes and pigment are expensive to produce
from a perspective of energy resources,
which are typically quite limited in caves.
The individuals that didn’t waste such
energy on useless structures had a slight
advantage over the ones who did. And a
slight advantage is all that it takes to drive
adaptive change in species.
What’s the ideal temperature for
tropical tanks? Different species
seem to come from areas in
which the water temperature is different.
We all go through different
phases. I was a heat fanatic in
the beginning, as I noticed that
my Betta splendens looked his