Each Sea Urchin Is One Big Eye

Studies suggest that sea urchins don’t have specialized eyes, the way people do. Instead, a sea urchin uses its entire body to see. A new study leads its research team to believe that sea urchins use their tube feet as retinas (the part of the eye that absorbs light), while pigmented cells in the rest of the animal’s body help block out extra light. Earlier studies had found that where and how many spines were on a sea urchin’s body affected how well it could see.

Read more about sea urchin eyes on National Geographic News.

Put together tidepool puzzles on National Geographic Kids.

Photograph by Paul Nicklen, National Geographic