Deep in the warm blue ocean lived Tiko the Tuna .Tiko belonged to a group called bony fish, also known as Osteichthyes. He loved swimming faster than anyone else in the sea.

Unlike many fish, tuna must keep swimming almost all the time.
Tiko used his powerful muscles and special gills to pull oxygen from the water while he swam.

“If I stop,” Tiko worried, “will I still get enough oxygen?”

One day, Tiko tried to rest like the reef fish did.
He slowed down… then slowed even more.

Suddenly, he felt tired and scared.

Tiko remembered something from fish school:
Some fast swimmers need ram ventilation, meaning water must move over their gills while they swim!

A wise old shark swam by.

“You’re built for speed,” said the shark.
“Your streamlined body helps you move quickly through water.
You are an open-ocean predator, not a resting reef fish.”

Tiko realized his body was perfectly designed for constant motion.