The Fish With a Window in Its Head Says Hello

The lab was dark except for one soft blue glow — Professor Pip's biggest aquarium, bubbling gently in the corner.

"Oh my whiskers!" Pip whispered, tail swishing so hard it thumped a table. "You are going to LOVE this."

He tumbled two cardboard tubes and a little tealight candle out of his lab-coat pockets. Mia, Leo, and Theo tiptoed up to the aquarium, noses squished right against the glass.

"Today," Pip said softly, "we're learning how creatures see in the deep, deep sea."

"How deep?" asked Theo.

"Deep enough that no sunshine reaches. If you swam down that far, everything would be pitch black — except for tiny sparkles of light that some fish make with their own bodies. That's called bioluminescence."

He handed a tube to each child. "Hold it up to one eye. Look at the candle."

The kids peered through — the candle looked normal enough. But then Pip cupped his paws around the flame so almost no light leaked out sideways. Suddenly the tubes felt useful. The tiny bit of light coming from above was easier to catch when you were looking straight up through a narrow tube.

"WHOOSH!" said Leo. "It's like a spyglass!"

"PRECISELY!" cried Pip. "That is what tubular eyes do. Instead of round eyeballs like ours, some deep-sea fish have eyes shaped like little telescopes, pointed straight up toward whatever faint light is drifting down from above."

He waved a paw at the aquarium. "Now. In the Atlantic Ocean off Brazil, scientists sent a robot named SuBastian 700 meters down — deeper than 40 blue whales stacked nose-to-tail. And there, floating in the darkness, was a barreleye fish. Its whole HEAD is see-through, like a little glass dome full of clear jelly! Inside the dome, two bright green tubular eyes swiveled around, looking straight up. Nobody had ever filmed one alive before — the fish is so delicate that when nets pull it up, its glass head pops."

"Like a periscope on a submarine!" said Theo, eyes huge.

"Exactly right! And the same expedition found thirty-one brand-new deep-sea creatures — jellyfish, comb jellies, and two giant single-celled animals as big as a marble."

Pip padded over to the arched window and looked up at the darkening sky. "The deep ocean has more space to explore than any other place on Earth. Every time we go down, we find creatures nobody has ever seen. Nobody!"

He tapped each child's tube. "Take these home. Tonight, try looking up through one at a very faint star. Then I wonder — what would you invent, if you had to see in the dark?"