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Message: <blockquote data-quote="sirajstc" data-source="post: 12013479" data-attributes="member: 91140">10 Animals With Incredible Eyesby TyB                                 According to scientists, eyes evolved around 540 million years  ago as simple light detecting organs. Today, vision is the most  important sense for many animals, humans included, and they have became  incredibly varied and complex. Take a look at some of the strangest and  most incredible eyes in the animal kingdom.  10 Tarsier   <img src="http://listverse.files.wordpress.com/2010/12/wp-content_uploads_2007_08_tarsier.jpg?w=550&h=413" alt="" class="fr-fic fr-dii fr-draggable " style="" /> The tarsier is a small (about squirrel sized) nocturnal primate,  found in the rainforests of South Eastern Asia. It is the only fully  predatory primate in the world, feeding on lizards and insects and is  even known to catch birds in mid flight. It’s most remarkable feature;  however, are its enormous eyes, the largest of any mammal, relative to  body size. If your eyes were proportionally as big as those of the  tarsier, they would be the size of grapefruits. These enormous eyes are  fixed in the skull, and can´t be turn in their sockets. To compensate  for this, the tarsier has a very flexible neck, and can rotate its head  180 degrees, just like an owl, to scan for potential prey or predators.  With each eye weighing more than its brain, the tarsier has extremely  acute eyesight and superb night vision; it has even been suggested that  they may be able to see ultraviolet light. On the other hand, they seem  to have very poor color vision, as is the case with many nocturnal  animals (including house cats and owls, for example).   9 Chameleon   <img src="http://listverse.files.wordpress.com/2010/12/chameleon011.jpg?w=550&h=393" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Chameleons are famous for their ability to change color, an ability  that helps them communicate and express their intentions, or mood, to  other chameleons (only a few species use color-changing as camouflage).  These lizards also have very unusual eyes; their eyelids are fused, and  cover almost the entire eyeball, except for a small hole to let the  pupil see through; each eye can be moved independently from the other,  and so the chameleon can scan for prey and potential threats at the same  time. This also means that the chameleon has a full 360 degree field of  vision.  When the chameleon sees a potential prey (usually an insect, although  the largest species are known to devour mice and other small  vertebrates), it focuses both eyes in the same direction, gaining  stereoscopic vision – very important if we consider that the chameleon  captures prey by shooting out its tongue at high speed, a technique that  requires a very precise distance and depth perception. Chameleons have  very sharp eyesight, being able to see an insect several meters away,  and just like the tarsier, they can see ultraviolet light.   8 Dragonfly   <img src="http://listverse.files.wordpress.com/2010/12/screen-shot-2010-12-12-at-3-16-59-pm.jpg?w=550&h=410" alt="" class="fr-fic fr-dii fr-draggable " style="" /> The dragonfly, possibly the most formidable aerial hunter among  insects, also has some of the most amazing eyes in the animal world.  They are so big that they cover almost the entire head, giving it a  helmeted appearance, and a full 360 degree field of vision. These eyes  are made up of 30,000 visual units called ommatidia, each one containing  a lens and a series of light sensitive cells. Their eyesight is superb;  they can detect colors and polarized light, and are particularly  sensitive to movement, allowing them to quickly discover any potential  prey or enemy.  Some dragonfly species that hunt at dusk can see perfectly in low  light conditions, when we humans can barely see anything. Not only that;  dragonflies also have three smaller eyes named ocelli which can detect  movement faster than the huge compound eyes can; these ocelli quickly  send visual information to the dragonflies’ motor centers, allowing it  to react in a fraction of a second and perhaps explaining the insect’s  formidable acrobatic skills. Although dragonflies are not the only  insects with ocelli (some wasps and flies have them too), they do have  the most developed ones.   7 Leaf tailed gecko   <img src="http://listverse.files.wordpress.com/2010/12/a304_giant_leaf_tailed_gecko.jpg?w=550&h=438" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Leaf tailed geckos have pretty surreal-looking eyes; their pupils are  vertical and have a series of “pinholes” which widen at night, allowing  these lizards to pick up as much light as possible. These eyes also  have many more light sensitive cells than human eyes, giving the animal  the ability to detect objects and even to see colors at night.  To give you an idea of the gecko’s amazing night vision, let us just  say that, while cats and sharks can see six and ten times better than  humans, respectively, the Leaf Tailed gecko and other nocturnal gecko  species can see up to 350 times better than we can in dim light!Leaf tailed geckos also have a series of strange, intricate eye  patterns, which provide camouflage. These lizards lack eyelids; their  eyes are protected by a transparent membrane, and geckos are often seen  cleaning this membrane with their tongue.   6 Colossal squid   <img src="http://listverse.files.wordpress.com/2010/12/colossal-squid.jpg?w=550&h=315" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Not to be confused with the better known, but smaller Giant Squid,  the Colossal Squid is the largest invertebrate known to science; it also  has the largest eyes in the animal kingdom. Each one of the Colossal  squid’s eyes can be up to 30 cms across, being bigger than a dinner  plate and having a lense the size of an orange. These huge eyes allow  the squid to see in dim light conditions, very useful for an animal that  spends most of its time hunting at 2000 meters below the surface.  It must be mentioned that only sub adult colossal squid have been  captured and studied thus far; full grown Colossal squid may grow up to  15 meters long. These giants would have even bigger eyes. Unlike the  Giant Squid, the Colossal squid has stereoscopic vision, having a  greater ability to judge distances. Even more amazing, each eye has a  built-in “headlight”, an organ known as a photophore which can produce  light so that whenever the Colossal squid focuses its eyes to the front,  the photophores produce enough light for the squid to see its prey in  the dark.                                                                                                                  5 Four eyed fish   <img src="http://listverse.files.wordpress.com/2010/12/foureyed12mar2001fwzc15.jpg?w=550&h=412" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Found in Mexico and Central America, as well as Northern South  America, these are small fish measuring up to 32 cm and usually found in  fresh or brackish water (although they have also been seen in marine  coasts). They feed mostly on insects, so they spend most of their time  swimming at the surface. Despite their name, four eyed fish have only  two eyes. However, these eyes are divided by a band of tissue and each  half of the eye has a pupil of its own. This bizarre adaptation allows  the four eyed fish to see perfectly (and at the same time) both above  and below the waterline, scanning for both prey and predators. The upper half of the eyeball is adapted to vision in air, while the  lower half is adapted to underwater vision. Although both halves of the  eye use the same lens, the thickness and curve of the lens is different  in the upper and lower eye halves, thus correcting for the different  behavior of light in air and water. This means that when the four eyed  fish is completely submerged, the upper halves of the eyes are out of  focus. Fortunately, the fish spends almost its entire life in the  surface, and it only has to dive completely once in a while to prevent  the upper halves of the eyes from dehydrating.   4 Stalk eyed fly   <img src="http://listverse.files.wordpress.com/2010/12/stalkeye.jpg?w=550&h=433" alt="" class="fr-fic fr-dii fr-draggable " style="" /> These small but spectacular creatures are mostly found in the jungles  of South East Asia and Africa, with a few species also found in Europe  and North America. They get their name from the long projections from  the sides of the head with the eyes and antennae at the end. Male flies  usually have much longer stalks than females and it has been confirmed  that females prefer males with long eyestalks. Males during mating  season often stand face to face and measure their eyestalk’s length; the  one with the greatest “eye span” is recognized as the winner.  Male stalk eyed flies also have the extraordinary ability to enlarge  their eyestalks by ingesting air through their mouth and pumping it  through ducts in the head to the eyestalks. They do this mostly during  mating season. <a href="http://www.youtube.com/watch?v=ZGdfIX5x8XM" target="_blank">Here’s an amazing video</a> of the male stalk eyed fly, newly emerged from its cocoon, actively enlarging his eyestalks:  3 Spookfish   <img src="http://listverse.files.wordpress.com/2010/12/bmimg_26206_26206_jellyfaced_web.jpg?w=550" alt="" class="fr-fic fr-dii fr-draggable " style="" /> The spookfish is a deep water, ghostly-looking fish that has some of  the most bizarre eye structures known to science; each eye has a lateral  swelling called a diverticulum, separated from the main eye by a  septum. While the main part of the eye has a lens and functions in a  similar way to other animal eyes, the diverticulum has a curved,  composite mirror composed of many layers of what seem to be guanine  crystals. This “mirror” is superior at gathering light than the normal  eye; the diverticulum reflects light and focuses it onto the retina  allowing the fish to see both up at down at the same time. The spookfish is the only vertebrate known to use a mirror eye  structure to see, as well as the usual lens. Spookfish are found  worldwide but are rare to see, since they spend most of their lives at a  depth of 1000-2000 meters. They feed on small crustaceans and plankton,  and measure about 18 cm in length.   2 Ogre faced spider   <img src="http://listverse.files.wordpress.com/2010/12/ogre-faced-spider-face.jpg?w=550&h=366" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Spiders are popularly known for having many eyes (although this  varies greatly among the different species, with some having two, four,  six or eight eyes). The Ogre-faced spider has six eyes, but it looks as  if it only had two because the middle pair is greatly enlarged. This is  an adaptation for a nocturnal lifestyle; ogre faced spiders have superb  night vision not only because of their huge eyes, but because of an  extremely light sensitive layer of cells covering them.  This membrane is so sensitive in fact, that it is destroyed at dawn  and a new one is produced every night. Ogre faced spiders are unusual  because they can see perfectly at night even though they lack tapetum  lucidum, a reflective membrane that helps others spiders (and other  predators such as cats) to see in low light conditions. As a matter of  facts, scientists believe that ogre faced spiders have better night  vision than cats, sharks, or even owls (which can see up to 100 times  better than humans at night!).   1 Mantis shrimp   <img src="http://listverse.files.wordpress.com/2010/12/mantis-shrimp2.jpg?w=550&h=412" alt="" class="fr-fic fr-dii fr-draggable " style="" /> And finally, we get to the animal with the weirdest and most amazing  eyes in the world. The mantis shrimp is not actually a shrimp, but a  different kind of crustacean from the Stomatopoda order. Known for its  aggressiveness and formidable weaponry (they have an extremely sharp and  powerful claw and can split a human finger in two or even break a glass  aquarium with one single strike), mantis shrimp are voracious predators  found mostly in tropical waters.  Their eyes are compound, like those of the dragonfly, although they  have a far smaller number of ommatidia (about 10.000 per eye); however,  in the mantis shrimp each ommatidia row has a particular function. For  example, some of them are used to detect light, others to detect color,  etc.  Mantis shrimp have much better color vision than humans (their eyes  having 12 types of color receptors, whereas humans have only three), as  well as ultraviolet, infrared and polarized light vision, thus having  the most complex eyesight of any animal known. The eyes are located at  the end of stalks, and can be moved independently from each other,  rotating up to 70 degrees. Interestingly, the visual information is  processed by the eyes themselves, not the brain.  Even more bizarre; each of the mantis shrimp’s eyes is divided in  three sections allowing the creature to see objects with three different  parts of the same eye. In other words, each eye has “trinocular vision”  and complete depth perception, meaning that if a mantis shrimp lost an  eye, its remaining eye would still be able to judge depth and distance  as well as a human with his two eyes. Scientists are only starting to  understand the mysteries of Stomatopod vision; for the moment, we can  only imagine what the world really looks like to a mantis shrimp.   + Trilobite   <img src="http://listverse.files.wordpress.com/2010/12/trilobite-model.jpg?w=550&h=550" alt="" class="fr-fic fr-dii fr-draggable " style="" /> Trilobites were one of the most successful animal groups of all  times, thriving for almost 300 million years long before dinosaurs  appeared on Earth. Although some species were eyeless, most of them had  compound eyes similar to those of insects. The weird thing about  trilobite eyes is that their lenses were made of inorganic calcite  crystal, a mineral that is also the main component of limestone and  chalk. In its purest form, calcite is clear, thus being an adequate if  unorthodox material for an eye lens. These crystal eyes are unique to trilobites, with the compound eyes  of modern invertebrates being made of chitin, an organic substance. Due  to their unusual composition, trilobite eyes were completely rigid and  could not be adjusted to focus; instead, the trilobite corrected its  focus with an internal eye mechanism which not only solved any potential  problems caused by the mineral lens, but also gave the trilobite such  good vision, that it could keep both close and distant objects in focus  at the same time.  As if that wasn´t bizarre enough, some trilobites had really weird  looking eyes; a few had their eyes at the end of long projections, just  like the Stalk Eyed Fly, while others had overhanging “eyeshades” on top  of the eye, protecting it from bright sunlight. Being made of calcite,  trilobite eyes fossilized easily, and therefore we probably know more  about trilobite eyes and vision than about those of any other  prehistoric creature.   ++ Goats   <img src="http://listverse.files.wordpress.com/2010/12/goateye.jpg?w=548&h=360" alt="" class="fr-fic fr-dii fr-draggable " style="" /> We all imagine pupils to be round – as they are the type we see most  often (on humans) – but goats (and most other animals with hooves) have  horizontal slits which are nearly rectangular when dilated. This gives  goats vision covering 320 – 340 degrees; this means they can see  virtually all around them without having to move (humans have vision  covering 160 – 210 degrees). Consequently, animals with rectangular eyes  can see better at night due to having larger pupils that can be closed  more tightly during the day to restrict light. Interestingly, octopuses  also have rectangular pupils</blockquote>

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