Top Animals With Unusual Vision

did you know that your brain can understand images that you've seen for just 13 milliseconds the image projected onto the back of your eyes is actually inverted the brain then flips it back for correct perception humans can see 100° vertically and 190° horizontally and can distinguish about a million Colors by the way what are the most active muscles in our body that's right the muscles that control the eyes moreover our vision is so sensitive that it can detect a light beam consisting of just 5 to seven photons yet even more astonishing visual abilities occur in nature here we're talking about animals particularly insects that surround us their Vision differs from ours because they have different evolutionary tasks and living conditions in today's to video we'll delve into this fascinating topic and you'll learn which animal can see 350 times better in the dark than humans and which one can detect ultraviolet light how do animals see This World by the way don't forget to hit like And subscribe as this would show the YouTube algorithm that this video is worth watching shall we get started [Music] first let's find out how scientists learn about animal vision for humans with our type of vision it can be hard to imagine what it's like to see differently the retina contains two types of receptors rods and cones rods distinguish light and dark while cones differentiate color just looking at rods and cones under a microscope can tell you whether an animal sees color brain scans can also reveal whether an animal reacts to Colors we can also determine if certain parts of the brain are activated by color changes of course we can't say exactly how animals see our knowledge is based on various studies and such diversity can sometimes be hard to grasp for instance we don't truly know what it's like to see ultraviolet rays which help deer find Lykan nor do we understand how mosquitoes see infrared radiation which allows them to detect the most blood-rich areas remember animals primarily need the vision to find food or to avoid becoming someone else's food for example insects have what is known as compound eyes which consist of special cone-shaped elements called omaia each one perceives only a tiny piece of the object in front of the eyes creating a mosaic image of the object for example honeybees have thousands of these elements in their eyes imagine how differently we would experience the world if we could see as animals or insects to but first let's explore how mammals the closest to us perceive the world let's start with dogs you probably think that they see the world in black and white right well this is a misconception human eyes have three types of cones determining color this allows us to distinguish light of three different wavelengths our brain perceives these wavelengths as blue red and green like most mammals dogs have two types of cones this allows them to distinguish Blue from yellow but not red from Green therefore their vision is similar to that of humans with red green color blindness who also lack the third type of cone by drawing parallels with such human Vision we can guess how dogs see which is something like this take a look to see blue and yellow colors both dogs and humans rely on neurons inside the retina they get excited in response to a beam of yellow light hitting the cone but their activity is suppressed when exposed to blue light as a result dogs discern blue and yellow however red and green light act neutrally on the neurons and dogs that means no signal is sent from these colors and the brain doesn't perceive them as a result where you might see a red or green tomato dogs likely perceive it in black and white how then can they distinguish red from Green typically red objects appear darker than green ones so a dark red apple will most likely be red interestingly some data suggests dogs may see more shades of blue than we do and are better adapted to Twilight although they get a blurrier image and finally they are much better at detecting movement so that gray wouldn't Escape them the misconception that dogs see everything upside down arises from the fact that the image on their retina is indeed inverted but this is also true for humans however our brains correctly Orient these images for example a dog lowers its head to drink not raises it so the only creatures that see upside down for lack of flying dogs might be flying foxes now let's look at the world through the feline eyes like dogs they are crepuscular creatures meaning they are active at dawn and dusk which influences their Vision cats possess 6 to eight times more cells for detecting objects in low light compared to humans enabling them to see much more in what we perceive as Darkness they also have better peripheral vision and the ability to detect movement in the dark their field of vision spans 200° surpassing the 180 to 190° typical in humans so they see things this way but cats don't surpass Us in every aspect daylight for instance isn't their Prime Time humans have a greater number of cones for color perception allowing us to discern a wide array of colors like red yellow orange and brown whereas for cats these colors look very similar it's not precisely known which colors cats see some believe they primarily see blue or gray While others suggest blue and yellow with hints of green regardless their color perception generally falls short of human Vision moreover they see much worse up close whereas humans can clearly distinguish objects at 14 CM 5. 5 in cats require a distance of 25 cm 10 in their longdistance Vision also isn't as sharp you can easily spot a soccer ball at 30 m 100 ft but for a cat it needs to be within 6 M 20 ft thus this furry friend will never enjoy a city Panorama because they see blurrier at a distance let's move on to larger animals what comes to mind when you think about an aversion to Red Rags Bulls in a bull fight however that's another misconception actually bulls don't distinguish the color red instead they perceive shades of violet gray black or various Browns bull fighting a traditional spectacle in Spain and other countries involves a matador teasing the Bull with a muleta a crimson cloth on a stick this has led to the widespread belief that Bulls dislike red imagine however being in the Bull's place at that moment surrounded by thousands of screaming and noisy people it's irritating and confusing the waving cloth triggers an adrenaline rush and a fight or flight response in the bull thus it's the sudden movement not the color that triggers the animal overall bulls have excellent vision and a vast field of view but unlike you they see only a limited range of colors generally in muted tones do you recall the two types of cones and dogs bulls have a similar setup they distinguish parts of the spectrum from Blue to Violet and from yellow to Green but they don't see all shades of yellow and blue let's see see through their eyes what Bulls really dislike are sharp contrasts of light and darkness for example a dark fence around a white building can make them nervous just like Shadows on objects which they perceive as pits for the same reason Bulls don't like to drink water with bright Sun Reflections preferring moderately lit environments they also poorly perceive distance to objects leading them them to occasionally charge towards a fence without realizing how close it is now let's examine horses animals with a nearly 350° field of vision this is due to the placement of their eyes on the sides of their heads which are much more mobile than those of birds therefore horses don't need to turn their heads as much as Birds to look forward horse Vision differs from human Vision in sharpness distance and the detection of peripheral movement approximately 23% of horses are nearsighted needing to approach an object to see its details clearly conversely 43% are farsighted details start to become clearer for them as they move away from the object it often seems that horses have excellent vision for example a horse might raise its head direct its ears flare its nostrils and widen its eyes at the sight of a distant bird flapping its wings this is how the horse sharpens its view stationary detail perception and sense of smell when we talk about Vision it's not always about size horse eyes are eight times larger than human eyes and the largest among terrestrial mammals however their visual Acuity is significantly worse than ours when it comes to distinguishing fine details for example you might notice details from a distance of 9 m 30 ft but a horse requires at most 6 M 20 ft for the same Clarity in other words they need to get up to 50% closer to see the same thing as you this is how a horse sees the peak of H's visual Acuity is around the age of seven and tends to decline as they get older their remarkable peripheral vision serves a vital purpose to spot predators in time and escape from them in a millisecond these fascinating creatures are known as Tarsiers measuring just 8 to 16 cm 3 to 6 in they are small enough to fit in your hand their diet consists of insects small vertebraes and bird eggs they are also the only known primates that communicate using ultrasound as you've noticed tarer eyes are quite large compared to their bodies each is about the size of this predator's brain interestingly Tarsiers cannot move their eyeballs if they want to look right or left they need to turn their heads despite this limitation their eye structure indicates that vision is crucial for them tar ERS are capable of seeing and catching insects and small birds even in Pitch Darkness this capability stems from the abundance of rods which distinguish light from darkness in the back of their eyes unlike cones which discern color as a result their eyes function like night vision goggles in the animal kingdom here they are researchers from Dartmouth claim that the last common ancestor of the currently living Tarsiers possess possessed very sharp Tri chromatic Vision similar to that of modern maret and apes this typically implies a dial lifestyle however tarir are primarily nocturnal scientists believe early tarir were adapted to lowl light conditions such as Twilight or bright Moonlight such conditions were dark enough for the development of large eyes but still not bright enough to maintain trichromatic color vision have you heard the expression blind is a bat actually it's misleading because bats are far from being blind perhaps the expression arose due to their fast and erratic flight pattern the visual Acuity of bats varies from one species to another larger species Mega bats have big eyes and rely on vision during flight and foraging most smaller species or microbats use echolocation for these purposes although they typically have smaller eyes nevertheless they still rely on vision for daily activities and detecting objects beyond the effective range of echolocation which is about 10 to 20 M 33 to 66 ft they need echol location to find fruits insects and small animals their vision is even sharper than that of most humans but unlike humans they lead a nocturnal lifestyle style and have excellent hearing bats mostly hunt late at night some species can even perceive colors thanks to two light sensitive proteins in the back of their eyes s opson which detects blue and ultraviolet light and L opsin which detects red and green light however many species lack one of these proteins resulting in complete color blindness certain bats from Central and South America have IND dependently lost their ability to see blue and ultraviolet light consequently losing their color vision thus the expression sees like a bat actually means that a person has excellent Vision since we're talking about flying creatures let's imagine what it's like to see the world from a bird's eye view and it's worth starting with those whose vision is so acute that they can discern details in an area of 13 Square km 5 square miles you've guessed it these are eagles not only do they observe what happens on the left and right but also notice when someone approaches them from behind these birds see 4 to8 times better than the average human although an eagle might weigh about 4. 5 kg 10 lb their eyes are roughly the same size as those of humans what we see clearly at a a distance of 1.

5 M 5 ft is equally clear to an eagle from 6 M 20 ft so they see things this way to fully understand an eagle's Vision consider this the human retina has a pit with 200,000 cones per millim where an eagle's retina has two pits each containing 1 million cones per millim what advantages does this give for instance if you were an eagle you could spot a rabbit from a distance of 3. 2 km 2 miles while diving for an attack an eagle's Vision remains sharp and clear throughout the approach moreover eagle eyes are positioned on either side of their heads offering merely a panoramic view their field of vision is 340° and they turn their heads every 5 seconds but that's not all they perceive ultraviolet light too these birds can track a tiny V from the sky by the ultraviolet rays reflected from the animal's waist cool right Eagles rule during the day but once the sun sets nocturnal Predators like owls take over at night just like in humans their piercing eyes are located at the front of their heads when the fields of vision from both eyes overlap it results in three-dimensional or binocular vision a feature shared with humans and many predatory animals this enables them to accurately measure distance and precisely time their attacks in fact owls have the most forward-facing eyes among all bird groups unlike us they have an additional Optical Advantage nictitating membranes these semi-transparent third eyelids protect the eyes from debris when the owl swoops in for an attack owl's eyes are exceptionally large so they capture enough light to see even after Sunset they make up to 5% of the total body mass of these birds to put this into perspective your eyes make up about 0. 003% of your total weight their pupils can dilate significantly maximizing light absorption on the light sensitive retina at the back of the eye the human retina has 20 rods for every cone whereas owls have a ratio of more than 30 rods for every cone that's why they are so good at detecting movement in the dark the eyes of some owl species are 100 times more sensitive in low light than yours this is how they see the only visual limitation for owls is their farsightedness this is partly compensated by sensitive bristles around their beaks giving them another way to perceive objects parrot's visual Acuity is comparable to that of humans they can notice an eagle soaring high above the clouds and flying off into the distance their retinas contain specialized cones that can capture ultraviolet light each of these cones contains a drop of colored oil which acts as both a micr lens and a light filter enhancing the bird's ability to distinguish colors therefore parrots perceive the same Shades as humans but with increased brightness and a clearer distinction between similar colors something like this parrot's Eyes located on the sides of their heads offer a nearly 300 Dee field of view such Vision helps them spot Predators long before they attack what else helps parrots with this the frame rate on a television screen is 60 to 100 frames per second with only high-end models exceeding that rate but a parrot's eye can capture more than 150 frames per second no wonder they notice even small movements and changes in their environment enabling them to fly away in time if threatened however parrots do have some limitations their depth perception and ability to move their eyeballs are inferior to humans for instance humans can rotate their eyes about 50° horizontally whereas parrots can only manage about 20° however their visual Acuity is too to eight times higher than that of some mammals have you ever tried sneaking up on a pigeon it's quite difficult unless it's a city pigeon already accustomed to people they're constantly Vigilant and well aware of their surroundings essential for their survival pigeons always stay alert and their excellent monocular vision with eyes on either side of their heads helps them avoid danger these birds have to constantly refocus when looking at objects on the ground nonetheless they possess Superior Optical characteristics they see 135° vertically and 340° horizontally and can also distinguish ultraviolet light it's no surprise that clothes reflecting ultraviolet rays scare and annoy them something like this they can also spot objects at much greater distances than humans interestingly it's not due to the vision sharpness but because they can maintain vigilance for extended periods this trait among others led the US Coast Guard to employ pigeons in search and rescue operations at the end of the 20th century the birds were trained to recognize red yellow and orange objects colors typically used for life jackets and other emergency rescue equipment upon spotting such objects the birds would Peck a switch turning on a light interestingly they retained alertness throughout even 3our missions pigeon's ability to distinguish five color channels compared to the three typically perceived by humans AIDS them in this task and what about their night vision it's better than yours but it depends on the brightness of the Moon and other surrounding light sources nonetheless they are dial birds and only move at night in extreme necessity imagine seeing eight times better than you do right now that's how Hawks see the world this remarkable vision is common to various Hawk species they have incredibly sharp vision due to the high density of photo receptors in their eyes this enables them to detect even the slightest movements from great distances this sense makes them excellent Hunters capable of spotting prey from afar with remarkable Precision most Hawks Can See Clearly at distances of 30 m 100 ft a range within which red tailed hawks for instance can spot mice and other small creatures they possess a 280° field of vision and a 40° binocular overlap this means Hawks can focus on a single object with both eyes like humans uring a clear image for highly accurate attacks moreover Hawks have an exceptional depth perception these experienced Hunters rely heavily on their vision for survival and success in the wild they perceive a broader range of colors than humans and can detect details invisible to us thanks to their ability to see ultraviolet light now let's take a look at the world through their eyes their vision is complimented by sharp hearing they pick up even the faintest sounds made by potential prey such as young birds nesting in trees or small rodents rustling in leaves long before a regular human would would notice their presence the combination of excellent vision and Keen hearing has made Hawks some of the most successful hunters in nature there is a joke that this bird's eye is bigger than its brain have you already visualized this picture this is about the ostrich yes yes the largest representative of the bird class for example the African ostrich reaches 2.

75 m 9 ft in height and weighs up to 156. 43 lb so maybe there is some truth to the joke the brain in ostriches is about 58 mm 2. 2 in long and 42 mm 1.

6 in wide it weighs up to 42 G 1. 5 Oz the ostrich's eye is round and the largest among all land vertebrates 50 mm 1. 7 in yes yes it is even bigger than in elephants at the same time according to various reports it weighs up to 60 G 2.

1 O So in weight it really outweighs the brain the ostrich needs its impressively sized eyes to find food and spot Predators for example ostriches can see a move moving object like a jackal or hyena at a distance of 3 km 1. 9 M during the day and 50 m 164 ft at night see through the eyes of an ostrich impressive don't you think these birds also have a wider field of vision than humans each eye can see about 150 to 170° and the right and left Fields over lap by 20 to 30% which means our character can see 300° now let's come down to earth from the clouds and see the world through the eyes of reptiles there are over 3,600 known species of snakes and each species has its own hunting style which largely determines their Vision researchers have found that daytime hunting snakes have lenses in their eyes blocking ultraviolet light which allows them to see clearly in bright conditions something like what you see on your screen right now on the other hand nocturnal snakes have lenses that allow more ultraviolet light enhancing their night vision while there's much less ultraviolet light after Sunset it doesn't disappear entirely these reptiles don't have eyelids instead they have trans parent scales covering their eyes protecting them from dirt and debris these scales are shed along with the rest of their skin during molting have you noticed how quick snakes are their lenses are more convex than ours allowing for sharper focus and quicker reactions to objects many believe that snakes don't seek colors in reality the retinas of some species contain rods and cones which help distinguish light and color the majority of their receptors are rods sensitive to light and movement but not to color however as we've already mentioned they also have cones but unlike us they perceive two colors not three indeed snakes see the world differently than we do in fact they can see so much more species such as vipers pythons and boas possess special organs pits between their nostrils and eyes that detect infrared radiation therefore they have two types of vision movement oriented daytime vision and thermal nighttime vision so imagine even in complete darkness snakes can see the thermal outline of a mouse or other small prey making them exceptional nocturnal Hunters the leopard gecko or spotted leopard Yu far is a unique species of lizard they are common in the desert areas of India Afghanistan Pakistan Nepal and Iran they are also popular as pets admired for their yellow and black spots but have you ever wondered how they see us through their eyes leopard geckos neither perceive ultraviolet nor infrared light while they have excellent peripheral vision they are nearsighted and struggle to focus focus on distant objects yet they are highly sensitive to moving objects take a look at how they see overall these lizards have good vision and see the world in colors and details as nocturnal creatures their eyes contain more rods than cones enhancing their ability to see well in low light some estimates suggest they see their surroundings 350 times better at night than we do during the day their vision is almost as good as that of humans leopard geckos also possess trichromatic Vision meaning they have three types of cones in their eyes sensitive to blue green and red colors however they perceive blue and green colors much better than red shades they can distinguish colors even in dim light scientists conducted an experiment where geckos were fed with color tweezers under Moonlight it turned out that the animals easily distinguished Blue from Green but not Orange from Red leopard geckos are primarily active at dawn and dusk when their environment is predominantly purple and blue this allows them to see their surroundings more clearly let's now explore our next creature who sees well both day and night submerged underwater it leaves only its eyes and nostrils above the surface interestingly it has a third transparent eyelid that protects the eyes underwater this creature's eyes are uniquely positioned if you look at them from the front it seems like the animal is looking directly at you from the side it seems to look sideways such positioning gives them the advantage of very good peripheral vision you've probably guessed that we are talking about a crocodile their eyes are about the same size as ours 24 mm 0. 9 in in width unlike you however crocodiles can see at night in daylight their pupils narrow to thin slits while at night they can fully dilate to help them see better although they don't see very clearly at night they can distinguish the outlines of Fish Deer Crustaceans zebras or other prey animals thanks to Tiny mirrorlike receptors at the back of their eyes improving their night vision they don't need to worry about other Predators but they are Vigilant about rival crocodiles in their territory This Is How They See additionally crocodiles see underwater thanks to the very same mirror-like receptors what's more they seek color underwater just like they do on land they most remarkable feature is the ability to retract their eyeballs into the sockets to protect them during a fight crocodiles don't need to move their eyes when scanning The Horizon because as you remember they have excellent peripheral vision so if you're reaching for a ball in the water and a crocodile is looking the other way chances are it still sees you would you like to see another reptile that has survived since the time of the dinosaurs meet the two Atara sphenodon punctatus or Guta a species native to New Zealand this ancient creature has lived through a significant Global temperature drop glaciation Mountain formation and tremendous changes in Flora and Fauna today the Tuatara is the only surviving member of the Sadona order it looks like a miniature dragon and can live for 100 years its distinctive feature is a third eye this unpaired eye is much smaller than the paired ones and is only visible in young specimens in adults it's covered with a thin layer of scales the animal's skull often has a special opening to accommodate the third eye now imagine seeing the world with three eyes what a colorful perspective and view would open up but let's dispel this notion this third eye is a light sensitive organ that doesn't perceive images it's also called the parietal eye it has a retina nerve and a lens-like structure but lacks an iris eyelids and eye muscles it might once have been a fully functioning organ currently it's believed to play a role in thermo regulation and establishing circadian rhythms the biological clock but what about the two ata's other two eyes they're just as remarkable possessing Advanced night vision and the ability to focus independently of each other they contain an additional layer of tapetum lucidum a special layer in the vascular eye coating of vertebrates it reflects light back onto the retina so the two aa's eyes glow and see better in the dark observe the difference additionally each eye is equipped with a nictitating membrane a third eyelid and now we finally reach a remarkable reptile that can spot a tiny fly 10 m 33 ft away until recently it was believed that its eyes moved completely independently of each other creating two different perspectives of the world however Israeli researchers have recently discovered that this lizard's eye movements are in fact coordinated we're talking about the chameleon of course it's known for its color- changing camouflage but its extraordinary eyes are no less remarkable they can track two separate targets simultaneously one with each eye alternatively one eye can follow a Target while the other surveys the surroundings during experiments using video games scientists placed chameleons in front of a screen showing an insect moving from side to side the animals reacted by shooting their tongues at this virtual meal in another game they showed one prey in the center of the screen visible to both eyes of the lizard then the image split into two insects flying to opposite sides of the screen the chameleon's eyes tracked both targets one per eye until one was chosen notice that while one eye tracks the prey the other tracks its own Target but at some point converges to the first to focus on one target this means that one of them is a tracking eye while the other one is a converging eye from this we can infer that the chameleon's brain controls each eye independently but there's also a higher level of control coordinating both eyes thus each eye kind of knows precisely what the other one is seeing something like what you see in this image Additionally the chameleon's eyes protrude on either side of its head providing the lizard with a panoramic view a remarkable Optical tool created by Nature itself so we move on to those who can distinguish ultraviolet wavelengths insects our character has huge spherical eyes with enhanced color vision meet the dragonfly to give you an idea aide of their Vision let's remind you that we humans have tricolor or so-called TR chromatic Vision we see colors as a combination of red blue and green but dragonflies are more exciting depending on the species they have four to five types of opsin I.

E much more than humans yes the dragonfly world is much more colorful than ours but even more interesting is that their DNA contains no less than 11 and in some species as many as 30 genes of different visual opsin in other words in the process of evolution the color vision has varied to the most incredible extent and some of the possibilities of such genetic diversity they use even now Japanese biologist Rio fahashi in Japan also found that dragonflies use different opsin at different AG ages for example larvae of some species that hatch in sand usually lack opsin that perceive the color blue other Studies have shown that dragonflies can see ultraviolet light that is dragonflies distinguish colors better than humans which means they could see flowers like this but in addition to being excellent at distinguishing colors dragonflies are also great at seeing targets quickly their vision is so fast that they can decide in less than 5 hundredths of a second whether a flying object is likely to be prey now imagine flipping through a notebook with a drawing of a flying bird if we do it quickly we'll actually see a mini video and won't notice the pages turning but to the dragonfly thanks to its super Vision the process will seem much slower and it will see exactly the Turning of the Pages where we see 60 images per second it sees about 200 which means it can see objects that we simply can't see even the dragonfly's movements are so fast that we would only be able to see them in detail if we filmed them with a camera that slows them down 80 times with their impressive 360 degree visual field and other abilities it's no surprise that these creatures have been around found for over 300 million years that's right they predate the dinosaurs now let's dive into Aquatic Life more specifically mantis shrimp has some of the most complex eyes in the animal kingdom mantis shrimp has up to 16 types of light sensitive cones compared to three in humans and they can see ultraviolet visible and polarized light polarized light is a light in which all light waves point in the same direction usually light waves travel in all directions but when light is polarized the waves are filtered and travel in Only One Direction it can happen naturally such as when light reflects off water or glass or with special filters polarized light is often used in sunglasses to reduce glare that's how objects look through such glasses as you can see the lack of glare makes the environment appear more contrasting mantis shrimp are the only known animals that can see light with circular polarization which means that the direction of the electric and magnetic fields changes circumferentially as the wave propagates now let's take a closer look at their amazing organs of vision the eyes of mantis shrimp consist of tens of thousand thousands of omidia meaning elements of facet eyes as in insects the very structure of the eye of the Mantis crayfish is very unusual the eye is divided into three sections with two hemispheres separated by a narrow linear middle band each hemisphere contains rows of omidia with different functions like color detection polarization and motion and thanks to these same two hemispheres the mantis shrimp can perceive depth with one eye they have six rows of modified matidia in the center of the eye the one above mentioned middle band that's where the real magic happens the first four rows detect ordinary and ultraviolet light visible to human eyes the omaida of the last two rows contain tiny hairs which some scientists believe are responsible for polarized Vision but can the Mantis crayfish distinguish more colors than humans a team of scientists led by Australian neuroscientists Justin Marshall experimented they trained test subjects of the species hapto squilla trispinosa to recognize one of 10 specific wavelengths between 400 and 650 nanom showing them two colors and rewarding them with frozen shrimp or muscles when they chose the right one eventually the mantis shrimp could distinguish other colors 50 to 100 nanom up or down the Spectrum but when the difference was reduced to 12 to 25 nanm the crayfish could no longer distinguish them in contrast the human eye distinguishes wavelengths at 1 to 5 nanom each type of photo receptor seems to pick up a particular color detecting it less sensitively than the human eye thus the transitions between colors are not as smooth for them as for us now without leaving the water let's look into the largest eyes on the planet they are at least 25 cm 10 in in diameter that's the size of a soccer ball who owns such huge eyes could it be the largest fish eyes nope the record holder here is a swordfish with 9 cm 3. 5 in eyes could we be talking about the largest animal that ever lived the blue whale no his eyes are only 11 cm 4. 3 in they'd fit into our character's pupils let's not tease you anymore we're talking about a giant squid so why are its eyes so big Dan Eric neelen and Eric Warren from lond University in Sweden believe that the the squid has developed its eyes to cope with some important tasks for the animal world most likely to detect in time one of the largest predators in the world the sperm whale the Squid's eyes are located on either side of its head meaning it doesn't have the binocular vision needed to judge distances it could be hypothesized that the big eyed squid sees farther than the small-eyed squid it would help find both prey and a mate but neelon and warrant found that the eyes see farther if they grow larger only until the pupil exceeds 2.

5 cm 1 in when the pupil grows to 3. 5 CM 1. 4 in and the eye grows to 9 cm 3.

5 in it makes no sense to grow larger a larger size will not make the vision better that's why this is the maximum eye size of a fish although the head of a sword fish could accommodate larger Vision organs a giant squid weighs about the same as a swordfish but its eye is about three times larger why let's break it down the large pupil allows the eye to collect every Photon of light in the extraordinarily deep and dark Waters where the squid lives and huge eyes have advantages over just big eyes for example they are much better at detecting large objects emit Ting their own light at depths of more than 500 M 1,640 ft that includes the already mentioned enemy of giant squid the sperm whale wait a minute but sperm whales don't glow you might argue and you'd be right that's how it is but they scare away tiny animals like jellyfish and Crustaceans that flash in response these flickering outlines would be too dim for most animals but not for the giant squid to him it looks something like this its eyes can pick up this light from 120 M 394 ft away and scan the water looking for these flashes they're also great at spotting details and our next characters can avoid predators and find dark Corners to hide in even though they don't have eyes how do they manage without them and why did they appear on our list the fact is it's possible to see without conventional sight but with the whole surface of your body in this case the whole body is one solid eye at least that's how sea urchins called Purple stulo and trotus sea according to scientists assumptions they owe their name to the purple Hue in their body coloration these urchins live along the eastern coast of the Pacific Ocean stretching from enata Mexico to British Colombia Canada they move with needles that act like stilts and specific tube feet in general stulo andus has a sedentary lifestyle they leisurely explore the bottom in search of food their favorite treat is the giant brown algae macr cytis pyer so how can their bodies see the thing is they have light sensitive molecules mostly in their legs and in tiny stalk-like appendages located between the spines altogether they function like a retina that's it the sea urchins change the angle and direction of Vision by retracting their feet but the spines themselves play a role in all this scientists have suggested that they may help hedgehogs distinguish relatively fine details by shielding light from different angles in any case purple stulo croas see better than hedgehogs ayom Metro lunter and echinometra veritas which have fewer spines well and of course scientists conducted some interesting experiments to prove this Sate Johnson a marine biologist at Duke University in North Carolina together with colleagues placed 39 purple stulo centrus on a lighted area with with a width of 1. 2 M 4 ft and hung a black Disc Off the Wall and then the most intriguing thing happened when the disc was almost 6 cm 2. 5 in wide the urchin showed no interest in it but when its width reached about 9 cm 3.