Do Fish Have Eyelids?

Answer

Most fish do not have eyelids, however sharks do have eyelids, even though they do not blink. Fish do not need eyelids since they have no need to maintain moisture over the cornea, the transparent front part of the eye. There is actually a fish called the four-eyed fish. These fish have eyes raised above the top part of their head and the eyes are divided in two separate parts. This allows them to see below and above the water surface simultaneously.
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Q&A Related to "Do Fish Have Eyelids?"
Fish do not have eyelids because the purpose of eyelids are to keep them moist so they don't dry up, and fish are already in water, so there is no purpose of eyelids for them.
http://wiki.answers.com/Q/Why_dont_fish_have_eyeli...
Fish spend time in an energy-saving state called "rest," but this is different
http://www.chacha.com/question/how-do-fish-with-no...
Most fish don't have eyelids because the purpose of eyelids is to keep eyes moist, and fish don't need that of course. But some fish do have eyelids, so they can protect their eyes
http://answers.yahoo.com/question/index?qid=201009...
Most fish do sleep but they can't close their eyes like humans because they don't have eyelids. Fish dont need to moisturize their eyes!
http://www.kgbanswers.com/how-do-fish-sleep-if-the...
2 Additional Answers
Ask.com Answer for: do fish have eyelids
Most fish do not have eyelids.
Some sharks do retain a third, thin eyelid called a nictitating membrane.
There are some fish with eyelids; fish are not a truly monophyletic group. Therefore critters usually subsumed under the category 'fish' are actually not really closely related to one another. A shark is about as closely related to a gold fish as we are to a frog. What has been referred to as 'fish' is usually an aquatic animal with some form of torpedo-shaped body (certain variations permitted), gills and fins. Eyelids in land animals largely serve the purpose of keeping the eye moist, a function not required in aquatic animals. But they also protect the eye from mechanical impacts, and this certainly is a problem for all animals, aquatic or terrestrial, especially when they are predators. Take the shark example again: sharks often prey on large animals that in case of a struggle could injure the shark's eye. To protect itself, the shark with a nictitating membrane will close the membrane to cover the eye. Sharks lacking the membrane will roll back their eyes and thus protect their eyes with their sclera that contains cartelage.
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