How do animals breathe underwater?

A fish gill under a microscope. (Courtesy of Nick Phelps | University of Minnesota)

A fish gill under a microscope. (Courtesy of Nick Phelps | University of Minnesota)

Our lungs are great at getting oxygen out of the air, but if we needed to do that underwater, we’d be sunk. So how do fish, shrimp, jellyfish and other marine animals breathe underwater? And what happens when there is no oxygen in the water for them to breathe?

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An aquaponic system at work:

An aquaponic system at the University of Minnesota. Water from the fish tank, which is full of nutrients, is used to feed the plants. The plants filter the water, which is then sent back to the fish tank. (Courtesy of Nick Phelps | University of Minnesota)

An aquaponic system at the University of Minnesota. Water from the fish tank, which is full of nutrients, is used to feed the plants. The plants filter the water, which is then sent back to the fish tank. (Courtesy of Nick Phelps | University of Minnesota)

Music in this episode from Good Old Neon.