From a six-eyed spider to a gecko that can see 350 times better than humans!
According to scientists, eyes started to evolve nearly 540 million years ago and are now extremely varied and complex. Here are some of the coolest and strangest eyes in the animal kingdom.
Giant Guitarfish
Photo credit: Snapshot from YouTube video by Science Magazine
Guitarfish do not have eyelids, instead they have a strong muscle that is used to pull their eyes back into their head. The giant guitarfish can retract its eyeballs almost 1.6 inches back into its head — nearly as far as the eyeball is wide. Since the guitarfish hunts for prey on the ocean floor, this feature protects the eye from sand and bits of coral.
Chameleons
Photo credit: Pixabay
Chameleons have very unique eyes — some of the most unique in the entire animal kingdom. Their eyelids are joined in a circle around most of the eye, leaving only a pinhole for them to see through. A chameleon’s eyes can move independently of each other, and each eye can move a full-360 degrees. This means that they can look at two different places at once — a useful feature for an desert animal that is exposed to predators in all directions!
Colossal Squid
Photo Credit: Mgiganteus1/Wikipedia
The colossal squid has the largest eyes of any animal on Earth, measuring nearly 11 inches across — about the size of soccer balls, with lenses the size of oranges. The colossal squid’s eyes both face forward, giving it extraordinary binocular-like vision. They also have photophores (light organs that work similar to headlights) that produce light for the squid to see its prey in the dark.
Cuttlefish
The w-shaped eyes of a cuttlefish. Photo credit: FireFly5/Wikipedia
The cuttlefish have very distinct “W”-shaped eyes that are not only unique but extremely powerful too. Cuttlefish are color-blind, however, the “W” shape is part of a highly evolved eye that uses acute polarization vision instead.
Dragonflies
Photo credit: Mark Morgan/Flickr (CC BY 2.0)
Similar to many insects, dragonflies have compound eyes made up of ommatidia, however, a dragonfly’s are quite complex. Their eyes are so big they cover most of their head, allowing for 360-degree field of vision. Dragonflies also have 30,000 ommatidia per eye that can see ultraviolet and polarized light, as well as three smaller eyes named ocelli capable of detecting movement, allowing them to react within a fraction of a second.
Leaf-Tailed Geckos
The leaf-tailed gecko has slit-like eyes without eyelids. Photo credit: Frank Vassen/Flickr (CC BY 2.0)
Leaf-tailed geckos have vertical pupils containing a series of “pinholes” that widen at night, allowing for amazing night vision. In fact, the leaf-tailed gecko can see 350 times better than humans! The interesting pattern on the whites of their eyes is required for full-body camouflage since they lack eyelids.
Goats
The slit-like eyes of goats give them a wider field of view. Photo credit: Jo Naylor/Flickr (CC BY 2.0)
Goats are really cool animals. They basically eat everything, even poison ivy, and sometimes sound like humans when they speak. Another interesting feature is their eyes — the plucky mammals have rectangular pupils, allowing for a 320 – 340 degree field of vision (compared to humans’ 160 – 210 degrees), and better peripheral vision. Their large pupils also give them fantastic night vision.
Ogre-Faced Spiders
Every night, the ogre-faced spider regrows a thin membrane over its eyes. Photo credit: Frank Vassen/Flickr (CC BY 2.0)
The ogre-faced spider has six eyes, however it looks like they only have two because the middle pair are much larger. They are nocturnal spiders with amazing night vision, 100 times better than humans, not only because of their large eyes, but also because of a light-sensitive layer of cells covering them. This membrane is so sensitive that it is destroyed at dawn and a new one is produced every night.
Mantis Shrimp
Photo credit: prilfish/Flickr (CC BY 2.0)
Mantis shrimp eyes are compound like a dragonfly, but they only have 10,000 ommatidia per eye. Still, mantis shrimp have the most complex eyes of any animal known on Earth — they have 12 color receptors (compared to humans only having three), as well as ultraviolet, infrared and polarized light vision. Each of the shrimp’s eyes are divided into three sections, allowing them to have trinocular vision and complete depth perception.
Spookfish
The spookiest eyes of the animal kingdom. Photo credit: Gdr/Wikipedia
Spookfish are actually quite spooky, with four eyes and ghost-like bodies. Most animals on Earth have eyes that use lenses to focus light and to see, however, spookfish have eyes that use curved, composite mirrors composed of guanine crystals to capture light. This eye focuses light so well that the spookfish can see up and down at the same time.
Sea Star
Photo credit: Saspotato/Flickr (CC BY-NC-SA 2.0)
Most people do not know that sea stars or starfish have eyes when in fact, they have five — one on the end of each arm. Although it is a fairly simple eye, called an ocelli, only capable of sensing lightness and darkness, having eyes for hands is pretty fantastic.
Tarsiers
Tarsiers always look surprised! Photo Credit: Roberto Verzo/Flickr (CC BY 2.0)
Although the colossal squid has the largest eyes of any animal on Earth, Tarsiers have the largest eyes relative to body size. They have been called the owls of the mammal world because they are not able to move their eyes around. However, to make up for that disadvantage, they are able to turn their heads 180 degrees in either direction.
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