Cave shrimp and cave fish don't… because they don't have eyes. Energy-saving eye loss, or the expensive tissue hypothesis, is one of a number of theories to explain why sighted animals that took up life inside caves evolved to be blind.

Why do cavefish have no eyes?

The fact that cave fishes don't use their eyes has no effect on their genes. Instead, cave fishes are blind because something happened to the genes that control the development of their eyes. This change is passed on from parent to offspring. That explains why a blind fish would have blind offspring.

How do Cavefish see?

The Mexican blind cavefish does not have eyes, but it can "see" obstacles in dark caves by puckering its mouth and producing bursts of suction, according to a new study. The research describes this unique form of navigation for the first time.