Holding Your Breath: Surviving the Heart of Marine Darkness

As you swim through a coral reef, you see parrot fish, clams and other colorful aquatic creatures swimming elegantly and going about their lives. While you, with your snorkel, are confined to the surface of the water and the occasional dive for as long and as deep as you can hold your breath, the fish “breathe” easily with their gills (or lungs in the cases of some evolutionarily interesting fish). But do they breathe that easily? Living in and getting oxygen from a high-pressure aquatic environment is difficult and metabolically demanding, and some fish have found special ways to make it easier.

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