The pupil is a necessary formation of the organs of vision. Without pupils, it makes no sense to have eyes, because it is through these holes that light enters the eye and enters the retina, which consists of numerous light and color receptors.
Variety of pupil shapes
Nature has created holes for the passage of light of various shapes. In each species of organisms, the pupil has exactly the shape that is most beneficial to the animal, in terms of survival.
So, a person's pupils are round. The fact is that we need an overview in all directions equally. A round pupil is characteristic of hunter-gatherers.
Cats have a vertical pupil. Because when hunting, they need to determine the distance to the object of attack most accurately in order to calculate the strength of the jump. The vertical pupil helps with this. However, tigers, lions, and all other large cats have round pupils, just like humans. Only small cats have vertical holes. Apparently, with a higher body height, the vertical shape of the pupil does not help.
Who has a rectangular pupil? So many mammals have this shape.
At the same time, in the dark, the hole becomes square. Which mammals have a rectangular pupil? Almost all ungulates. The fact is that herbivorous mammals need a wide view of the terrain to survive. Rectangular pupil allows you to increase the field of view up to 340 degrees. Moreover, ungulates usually graze in herds. Many eyes are constantly scanning the area. What's also interesting is that a goat's eyes, for example, can rotate 50 degrees to keep the pupil horizontal when moving their head. By tilting its head towards the grass, that is, while eating, the goat keeps the rectangular hole horizontal.
Giraffe Pupil
In a school course, the following question may come across on tests: who has a rectangular pupil? Giraffe or octopus? This question is tricky. I should think. People may know that goats have rectangular pupils. Based on this, conclude that the giraffe, which is also hoofed, has rectangular eye holes. But his pupils are rather oval. Horses have the same. In low light, their pupil becomes large and round.
Pupil of a cephalopod
Who has a rectangular pupil? At the octopus. The opening of his eye is strictly rectangular.
Who else has a rectangular pupil? At the mongooses. Apparently, also to increase the visibility of the area.
Some cephalopods have been given intricate shapes by naturepupils. In cuttlefish, they are sickle-shaped or in the shape of the Latin letter "S".
Pupils of amphibians and reptiles
In geckos, the pupil in a constricted state has the shape of beads strung on a string.
Amphibians also differ in the variety of shapes of eye openings. Our frogs have horizontal pupils. And the spadefoot has a vertical orientation, like a cat. On this basis, it is easily distinguished by all young zoologists. There are amphibians with diamond-shaped pupils. This feature also helps expand vision in all directions.
Origin of pupil shapes
Let's consider the example of ungulates. Those with rectangular pupils had round eye holes in the distant past. But the constant bright sun forced the muscles to narrow the openings of the pupils. Ungulates need to protect their eyes in order to maintain good vision even in low light at night. Such mammals now have developed muscles responsible for horizontal contraction of the pupil. It is this form that allows you to look around the territory most widely without turning your head. When the muscles relax, which occurs with fright or a decrease in light, the pupils dilate. This increases the amount of light reaching the retina.
Thus, after analyzing many animals, scientists came to the conclusion that the shape of the pupils depends on the ecological specialization of the species. Hunters and gatherers have round pupils. In ungulates it is rectangular. And for ambush hunters, a vertical pupil is better.
