Brainz reports the existence of at least 10 animals that are born without eyes, including the Kauai cave wolf spider, southern cave crayfish, Mexican tetra, blind legless lizard, Texas blind salamander, widemouth blindcat and fresh water hydra. Other animals born without eyes are the blind albino cave crab, Brazilian blind characid and the olm. Many of these animals live in environments with very little or no light.
Despite being blind, each of these animals has developed a way to interact with, or sense, the surrounding environment, according to Brainz. The widemouth blindcat, a fish native to the Edwards Aquifer in San Antonio, has a responsive lateral line that allows it to feel vibrations in the water. The blind legless lizard is believed to live primarily underground and use its sense of smell to lead it to food. Southern cave crayfish compensate for a lack of sight with heightened senses of touch and smell. A freshwater hydra is only 0.39 inches long, reports Brainz, and has stinging tentacles that it uses to capture prey. The stinging cells on the freshwater hydra's tentacles can sense and react to light. The olm is a European amphibian that is believed to eat, sleep and reproduce under water. Olms use sensory receptors on their heads to discern chemicals and movement.