Barreleye Fish, also known as Pacific barrel eye fish, is a small deep-sea Argentine fish, mainly living in the Atlantic, Pacific and Indian Oceans 600 to 800 meters of tropical waters.
Image source: National Geographic
The most peculiar thing about this creature is its eyes, you don't think that the two small black dots in front of it are its eyes, but in fact it is just its nose.
Their eyes can be said to be on the top of the head, and the eyes above the top may have done it in this fish.
These fish are named after their barrel-like eyes, and their heads are transparent, like a pilot's cockpit.
These eyes can move inside the transparent "cockpit", their eyes have a large lens and retina, with extremely high visual cells and a high density of "visual purple" pigment.
The barrel-eyed fish has a large round transparent head, which is so that the eye can collect more incident light to determine the location of the food. Another function is to protect sensitive eyes from the attack of tube jellyfish.
Why the barrel-eyed fish evolved such a shape, scientists have given an explanation:
Seeing the little friends here must be a little curious, this fish head occupies such a large piece of the head, and their mouth is very small, so how do they eat?
This brings us back to the question of why the fish's eye grows above its head, because the bucket-eye fish's prey does not live as deep as it does, so they must stare above themselves.
Over time, the eyes evolved to the top of their heads, and now their eyes still do only one thing, and that is to look at the prey overhead.
Then it's also fun for them to eat, and when their eyes catch their prey, they quickly rush straight up and bite the prey with their small mouths.
Of course, it is inevitable that the "rice grains" will be full of mouths.