Why don’t fish have eyelids ?

Most fishes don’t have eyelids , and that’s because they really don’t need them . Eyelids help moisten eyes , so they don’t dry out . Eyelids also protect eyes from things in the air , like dirt and dust . Since fishes live in water , dry eyes are not really an issue .

But some fish , like sharks , still have them . Other fish have special eyelids that are thick and transparent , or see-through . Scientists think these special eyelids are a lot like glasses because they help fishes focus on objects .

Close-up of Tiger shark (Galeocerdo cuvier) off Tiger Beach, Grand Bahama Island, Bahamas. (Photo by Stephen Frink /Digital Vision/Getty Images)

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