The World's Biggest Glowing Animal — and Why It's Sparkly

"Everyone, into the dark corner of the lab!" cried Professor Pip. He turned off the overhead light and pulled out his pocket notebook, a glow-stick, and a paper shark he'd cut out that morning.

Mia, Leo, and Beatrix shuffled into the shadows, giggling.

"Today," Pip announced, spectacles flashing, "we're solving a shark mystery. Deep in the ocean lives the kitefin shark. It's as long as a grown-up — the largest glow-in-the-dark animal with a backbone we know of. But why would a shark want to shine?"

"So its friends can find it?" Leo guessed.

"A lovely guess! But watch." Pip held the paper shark up on a string and clicked on a small flashlight above it, pointing down. "Pretend this flashlight is the Sun shining down into the ocean." He tilted his head. "Now, look up at the shark from below."

The children lay on the floor and peered up. Against the light, the paper shark was a big dark silhouette — an easy shape to spot.

"A yummy shape for a fish to see and swim away from," Pip said. "Now — my whiskers! — watch this trick." He snapped the glow-stick. CRACK! A soft green glow spread across the paper shark's belly.

"It disappeared!" gasped Beatrix.

"Precisely!" Pip clapped. "The glow from below matches the light from above. From a little fish looking up, there is no shadowy shark shape at all. That trick is called counter-illumination. The kitefin shark's belly has millions of teeny lights called photophores that glow at just the right brightness."

"Oh!" said Mia. "It's like camouflage — but with light instead of paint!"

"Exactly right!" Pip's tail thumped. "And here is the marvelous twist scientists just discovered: the shark's glow is extra bright out to the sides. That side-glow acts like a soft searchlight, helping the shark spot yummy squid and fish. So its light hides and hunts, all at once."

Pip looked at his glow-stick and sighed happily. "Nature is such a clever inventor. Every problem — being seen, finding food — has a beautiful solution somewhere."

He handed each child a small glow-stick to take home. "Now you try, in your own dark room tonight. And I wonder… what other animals do you know that light up?"