Mexican cave tetra are interesting, but even the blind ones are less evolutionarily along the path to blindness than most North American species, which is why they so easily revert when crossbred.
What is really interesting are Amblyopsis rosae and Typhlichthys subterraneus. A. rosae not only lacks eyes, it lacks an optic nerve. T. sub has a vestigial optic nerve. You can play 'light games' with both... they will move away from the 'bright spot' of an incandescent headlight, although the outer 'darker circle' of a typical flashlight doesn't seem to faze them. (This is anecdotal evidence by multiple reliable observers-- darned if I know why.)
The journey from sighted to blind also happens in single specimens of Eurycea speleaus -- the pink Ozark grotto salamander. As larva, they have eyes and pigment; by adulthood they lose pigmentation and the eyelids have fused shut, and although they are still sensitive to light, they cannot 'see' in any real sense.
Last Edit: Jan 7, 2008 20:25:06 GMT -5 by Azurerana