A See-Through Fish Was Just Filmed Alive in the Deep Sea

Professor Pip’s fluffy tail was bouncing so much it nearly knocked over a lantern. On the deck of the Little Compass, a sturdy little research boat, he cradled a large glass jar of seawater against the pink twilight sky.

“Oh my whiskers, Mia, come look, come look!” he cried.

Mia and Leo scampered over. Inside the jar, something tiny and jellylike floated: a delicate fish shape with a completely see-through, dome-shaped head — like a little glass helmet. Two glowing green eyes peered up through the dome.

“Its head is… clear?” Leo whispered.

“Not just clear,” Pip said, “transparent. This is a barreleye fish. Scientists just filmed a real one, alive, deep in the Atlantic Ocean — the first time we’ve ever seen this shy little creature in its own home.”

Mia leaned so close her breath fogged the jar. “Why is it see-through?!”

Pip patted his lab coat and pulled out his tiny brass telescope. “Because down deep — thousands of feet below the waves — there is almost no light. Only faint, faint glimmers from far above.” He pointed the telescope straight up. “The barreleye looks up with those tube-shaped eyes to spot the tiny shadow of dinner passing overhead.”

He held up the jar so the last sunset light shone through it.

“But here’s the tricky bit,” Pip said. “If its eyes stuck out of its head like ours do, they’d be easy for a bigger fish to nibble on. So — very clever — the barreleye tucks its eyes inside its own see-through skull. The skull is like a little window, protecting the eyes while still letting light in from every direction.”

Leo’s mouth hung open. “So it’s… wearing safety goggles made out of its own head?”

“Exactly right!” Pip laughed. “You could say the barreleye invented safety goggles a hundred million years before we did.” His tail swished. “This is called an adaptation — a special feature that helps a creature live in a hard-to-live-in place.”

Mia looked out over the dark water. “There must be so many weird things down there.”

Pip nodded slowly and set the jar on the deck. “Every single dive, we meet a new neighbor we didn’t know we had. Now I wonder…” He tapped the jar softly. “What sort of window would you invent, if you had to live somewhere brand new?”