Anyone who has seen a goldfish will find a phenomenon: whenever you see a goldfish, it is a gesture, an expression, it seems that it never gets tired, never rests, and even death has its eyes open. Is it really? Today I will share with you why fish sleep with their eyes open? The reason why fish sleep with their eyes open.
Fish move forward under the action of fins by swinging the tail and trunk. They belong to vertebrates, and the nervous system and muscles also produce fatigue, which needs to be relieved by sleeping. The sleeping posture of fish is also very different. Some fish like to burrow into the sand to sleep. They have a sense of security and can avoid natural enemies. Some fish like to hide behind water plants or rockeries and sleep motionless. Parrotfish secrete a gelatinous substance. When they sleep, they blow bubbles. This foamy gelatinous substance hardens with water and then The parrotfish burrowed into the bubble and began to sleep, making a small hole in the front of the bubble. Tuna swim as they sleep, and it can be difficult to see when they are asleep.
In fact, the structure of fish eyes is basically similar to that of human eyes, the difference is that fish have no lacrimal glands and no eyelids. The lens of fish eyes is spherical, and visual accommodation depends on the forward and backward movement of the lens position, rather than the convexity of the lens. Therefore, fish are extremely short-sighted and can rarely see things beyond 12 meters, but because of their prominent eyeballs, they have a very wide field of vision. One eye can see the range of 60-180 degrees in the horizontal plane and 150 degrees in the vertical plane. scope. The horizontal viewing angle that a single eye can see is 160 degrees, and the vertical viewing angle is only 80 degrees.
Why do fish sleep with their eyes open? It’s because there are no eyelids.
