Eyelids in front of all animals. But the fish have no eyelids, no blinking reflex.

Why did nature deprive them of this? And do they need to blink at all?

Why do we need eyelids and a blink reflex?

Of course, living beings need eyelids in order to blink. And blinking, in turn, is required in order to cleanse and moisturize the eyes. The visual organs are unusually sensitive; foreign bodies should not enter them.

Mammals have eyelashes to protect their eyes, which reduce the risk of dust and dirt. In the blinking process, all those impurities that get into the eyes, bypassing this barrier, should be removed.

For reptiles and amphibians, this aspect is even more important, since they do not have eyelashes. In snakes, the eyelids grow together, remaining transparent, forming a kind of protective "glasses" that go with the old skin.

A lot of adaptive protective reactions arose in nature to protect the eyes, and it was blinking that became the highest and most “convenient” form of this protection for living things.

Also, the blink reflex forces you to close your eyes when some object sharply approaches the face, directly to the eyes, or even touches them. This reaction is also a defense. One way or another, the eyelids are the last barrier to the organs of vision, which are crucial for survival.

What other protection does the eyelids provide?

Many living creatures have lacrimal glands near their eyelids that release small volumes of fluid to moisturize their eyes.The eyelids help to evenly distribute this fluid and protect the organs of vision from drying out. After all, they must be constantly moistened.

Mammals and birds usually close their eyes when they sleep or rest. The eyelids fall into their eyes, cutting off from an overabundance of information that is completely unnecessary at the moment, and thus allow the psyche to rest. This aspect is also extremely important. So, you can hardly sleep with your eyes open.

How do fish live without eyelids and blinking?

Given all these factors, many people will even wonder: how do the fish dispense with the eyelids, which are so necessary for protecting the eyes, and therefore for survival? In fact, everything is very simple. Eyelids do not need fish at all.

They are constantly in the water, which washes the visual organs, providing them with natural hydration. At the same time, it perfectly washes any dirt. Yes, many fish lead a near-bottom lifestyle and can dig for a long time in silt or sand at the bottom, but the water softens the abrasive qualities of the sand, preventing it from damaging the fish’s eyes, and anyway eventually leaches any dirt.

The eye membranes of the fish are dense enough to protect them from damage that they could actually get in the water. Therefore, meeting in nature with one-eyed fish is a huge rarity. At the same time, in the terrestrial world it is often necessary to see animals with damage to one or both organs of vision. This is especially true for predators. After all, blinking does not always save.

The brain and nervous system of fish are far from developed as in mammals, for example.And constantly open eyes do not interfere with them at all and do not overload the psyche in the same way as people, for example. And therefore, in this regard, they also do not need eyelids.

Interesting fact: a mud-clown fish goes to land and can be out of the water for a long time. But she does not have a century, which is in this case a certain problem. But the arrangement of the eyes and adjacent areas in amphibians is already much more complicated, due to their long-standing evolutionary approach to land and the development of necessary protective barriers.

All marine mammals have eyelids. Whales, dolphins, killer whales and fur seals have them. For whales, they become a kind of atavism from the time of life on land. And for the same seals, they retain their importance, since these creatures can go to land, and do it regularly. Sharks also have no eyelids, like all fish.

Thus, the fish do not have eyelids and a blinking reflex, because in the water they do not need them. However, most of the fish can move their eyes, and even draw them in a little.