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May I ask how fish breathe? – Nghi, 11, Vietnam

July 10, 2025 melissamayer

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 …

How do animals breathe underwater? – Kinsley, 9, North Carolina

January 4, 2024 melissamayer

Dear Kinsley,

Have you ever seen a diving beetle? They’re one of my favorite animals. They live underwater and breathe air from a bubble attached to their butts.

I talked about all the ways animals breathe underwater with my friend Wes Dowd. He’s a marine biologist and animal physiologist. He studies how living things interact with the world around them.

Animals need oxygen. For air-breathers like us, oxygen is mixed into the air. For water-breathers, oxygen is mixed into the water. To get oxygen into our bodies, we all need organs and tissues made of very thin material with lots of surface area. That means lots of places that touch the air or water where oxygen can pass through. Like inside lungs or gills. Or the skin of frogs, toads, newts and salamanders that can live on land or underwater.

May I ask how fish breathe? - Nghi, 11, Vietnam

January 7, 2018 rcwebber

Dear Nghi,

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 …