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 Have
you ever seen a goldfish blink its eyes? Your answer
is probably no. Don’t goldfish
have eyelids? If not, why not?
In fact, all kinds of fish don’t have eyelids. That means goldfish
also doesn’t have eyelids. Eyelids protect eyes from dust in the air. They also
prevent eyes from getting dry. The reason that
fish don’t have eyelids is that they don’t need them underwater. Why is that?
Fish’s eyes are moist all the time because they live in water. And
they don’t need to protect their eyes from dust in the air!
 For a goldfish,
if it has eyelids, it will be a big obstacle to see far ahead
in water. Goldfish are pretty low down on the food chain, so many other
fish and sea creatures want to eat them.
Therefore, it is important for goldfish to keep watch and avoid enemies. That is why it evolved
over time to not have eyelids.
So how do goldfish protect its eyes? If you look its eyes very closely,
it has a very thin membrane over them. The membrane
plays an important role in protecting a goldfish’s eyes, instead of eyelids.
By now you are probably curious: how do goldfish
sleep if they don’t have eyelids? Don’t be surprised. Goldfish sleep
with their eyes open! |
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