• Question: Why do fish sleep with their eyes? Or they don't sleep at all?

    Asked by SofiaS.05 to Ines, Carrie on 7 Mar 2017.
    • Photo: Carrie Ijichi

      Carrie Ijichi answered on 7 Mar 2017:

      Sleep in animals is quite a new area of scientific research so this will be hard to answer. Fish don’t have eyelids the way we do so they don’t close their eyes. most animals that live in water and have to be alert for predators probably let one half of their brain go to sleep and then the other. How cool is that?!

    • Photo: Ines Goncalves

      Ines Goncalves answered on 7 Mar 2017:

      hahaha, because fish don’t have eyelids. The closest to an eyelid in fish is what you can find in some shark species. They have a thin membrane (nictitating membranes) they pull over the eye just before they attack a prey, to make sure their eyes are protected. Fish sleep, ust not as profoundly as we do (poor them!) because at least a part of their brain needs to be active and on the look out for predators. Also, in bodies of water without currents, many fish need to keep swimming to make sure water flows through their gills and take up oxygen, otherwise they literally suffocate without air. Living under water is tough!

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