Flounders’ Eyes Face Skyward. How Do They See the Ocean Floor?

All flatfish have eyes on the end of stalks, so they pop out of the head “kind of like the eyes we saw in cartoons—ba-boing!” says George Burgess of the Florida Museum of Natural History.

Thanks to those pop-up peepers, “they can’t see the bottom directly underneath them, but they can see the bottom around them,” notes Jackie Cooper of the National Aquarium in Baltimore.

Their eyes can also move independently, widening their field of vision, Cooper says.

Once flatfish eyes get the lay of the land, they message the brain, which in turn sends signals back to the skin. This organ contains color-changing cells such as melanophores, which either expand or contract according to the background the fish is trying to match, Burgess says. (See pictures of fish glowing in neon colors.)

For instance, expanding their cells would make their color darker.