Dear Nghi,

When you and I take a deep breath, we pull air into our lungs. That’s because humans and cats are mammals. But fish aren’t mammals. They usually don’t breathe air. They usually don’t have lungs.

That’s what I found out from my friend Michael Berger. He’s a biologist at Washington State University.

He told me that you can actually see a fish breathe water. Its face gets bigger when it takes in a big gulp of water. Just like when you take a big bite of food.

When you look at a fish, you can usually see the gill openings—called gill slits. … » More …

Dear Nghi,

When you and I take a deep breath, we pull air into our lungs. That’s because humans and cats are mammals. But fish aren’t mammals. They usually don’t breathe air. They usually don’t have lungs.

That’s what I found out from my friend Michael Berger. He’s a biologist at Washington State University.

He told me that you can actually see a fish breathe water. Its face gets bigger when it takes in a big gulp of water. Just like when you take a big bite of food.

When you look at a fish, you can usually see the gill openings—called gill slits. … » More …