Do fish have eyelids?

The simple answer is no!  That’s why you will never get a nod and a wink from a fish.  They have a thin transparent layer that covers the eye, similar to our cornea, to protect it from nasty particles.  A lot of people think that fish have poor eyesight.

Image Credit Flickr User Benson Kua

In fact, it’s wonderful and they can see some of the color spectrum that we can’t.  Their eyesight is important to them because they rely on it to recognize other members of their own species.  Which raises another question – fish don’t have mirrors, so how do they know which fish is a fish like them?  All in the genes, the recognition factor is not learned behavior; it is something with which they are all born. No surprises there, then.