Seals have such large eyes to improve their vision underwater, allowing them to hunt effectively and spot predators in their aquatic environment.
Seals live in an often dark aquatic environment, where light is quickly absorbed by the water. Having large eyes allows them to better capture the rare available rays of light, especially in the deep sea or when the light is low. They are therefore able to see well even when diving deep below the surface or when the sun is not shining. Good vision is crucial for avoiding obstacles, spotting prey, protecting themselves from potential predators, and increasing their efficiency in underwater movement. In short, their large eyes simply help them to better navigate and survive in their dark and changing natural habitat.
Seals have a very sensitive retina with a lot of rod cells, ideal for capturing even the faintest light from the depths. They also benefit from a tapetum lucidum, a kind of reflective layer located behind the retina, which allows light to pass through the eye twice: as a result, they have much clearer vision in dark water. Another useful adaptation is that their pupils can dilate to the maximum, letting in as much light as possible, perfect for night dives or in the ocean depths. Finally, their eyes produce a thick protective fluid, safeguarding the salty cornea from the sea and allowing clear vision underwater without irritation.
Thanks to the impressive size of their eyes, seals capture a large amount of light even in low light conditions. Underwater, this is a valuable asset for spotting prey such as fish or squid, especially when they swim quickly in the darkness or deep waters. This excellent vision then allows for precise distance calculations, facilitating quick and accurate attacks. Having big, good eyes clearly helps to turn even the slightest furtive shadow into a potential meal. It is clearly a very useful adaptation when regularly hunting underwater in challenging light conditions.
Seals have a very flat cornea, perfect for sharp vision underwater, but it makes them quite nearsighted at the surface. Fortunately, their very thick and rounded lens compensates for this by adjusting focus so they can see clearly even out of the water. Additionally, a retina rich in rods helps capture maximum light, ideal in the depths where darkness reigns. And a clever bonus: the tapetum lucidum, this reflective layer at the back of the eye, amplifies available light, which also explains why their eyes shine at night when illuminated.
In some species of seals, the eyes can detect movements and shapes at a depth of up to 600 meters underwater, where sunlight is almost completely absent.
The large eyes of seals, which give them a gentle and endearing appearance, also play an essential social role by facilitating mutual recognition and visual communication between individuals.
To protect their sensitive eyes from extreme diving conditions, seals can close a third transparent eyelid called the nictitating membrane, which acts as an underwater protective lens.
The exceptional night vision of seals allows them to hunt effectively for prey at dusk or in the ocean depths where natural light never fully reaches.
Studies indicate that seals perceive a limited range of colors. Although they have retinal cones that allow for color perception, their dark marine environment promotes an increased sensitivity to contrast and light rather than a rich color vision.
Seals do not see completely in absolute darkness, but they have an excellent ability to detect low light thanks to their retina, which is rich in receptor cells, allowing them to move easily in dark marine depths.
Exactly! Although all seals have relatively large eyes compared to their body size, some species living at great depths have even larger proportionate eyes, allowing them to maximize the amount of light captured in their very dark environment.
Sure! Here’s the translation: "Yes, but their vision out of water is less sharp than underwater. Their large eyes are adapted to a low-light marine environment, allowing them excellent underwater vision, but they remain functional on land."
This phenomenon is due to their extremely large pupils adapted to low-light underwater conditions. At the surface or in bright environments, the pupil constricts, but underwater or in dark conditions, it dilates significantly, creating the impression of an entirely black eye.
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