Two bind fish can make a sighted one, according to research published in the latest issue of the journal Current Biology.
The study by Richard Borowsky studied the genetics of eye development by crossing natural populations of Blind cave fish (Astyanax mexicanus) from different caves in Mexico with each other and testing the vision of the offspring using the optokinetic response: the reflexive following of moving stripes by the subject's eyes.
The author found that not all offspring of the inter-cave crosses are blind, with as many as 39% of the offspring from the crosses developing vision.
The results of this study support previous research that has shown that eye loss in the blind cave fish is the result of mutations at multiple gene sites (up to 12 in some populations), and that eye loss has evolved independently at least three times.
Using results from crosses between cave and surface populations, the author found that the loss of function at three or four out of the 12 gene sites is enough to abolish vision.
For more information, see the paper: Borowsky, R (2008) Restoring sight in blind cavefish. Current Biology 18, pp. R23"R24.