# data[].attributes.attachment_link.description
Hank tells us about new research into the question of how animals navigate from place to place - while the problem is still unresolved, we do have some hypotheses, and they all involve something called "magnetoreception."

# data[].attributes.attachment_link.title
Caribou Spot Wolves Using UV Vision | Animal Super Senses | BBC Earth

# data[].attributes.attachment_link.title
How foxes use magnetic fields to catch prey - The Wonder of Animals: Episode 5 Preview - BBC Four

# data[].attributes.attachment_link.title
Why BEAVERS Are The Smartest Thing In Fur Pants

# data[].attributes.attachment_link.title
Mountain Goats Aren’t Actually Goats | National Geographic

# data[].attributes.headline
Northern Scorpion - the animal with 12 eyes that can't see!

# data[].attributes.subject
Northern Scorpion - the animal with 12 eyes that can't see!

# data[].attributes.attachment_link.title
Canada’s Venomous Scorpions Glow As They Hunt Prey In The Dark of Night | Wild Canadian Year

# data[].attributes.attachment_link.title
Heat-Seekers: Harnessing the Infrared Senses of Animals

# data[].attributes.attachment_link.readable_text
You might be surprised to learn that many animals are actually able to see into the UV part of the EM spectrum. From insects to fish and even certain species of mammal, this trait is quite common.

We humans, on the other hand, appear to either lost it or never had it in the first place. To them, our visual world would look very alien indeed.

Quite why this case is still a matter of debate, but it may well be a compromise for our fairly sophisticated visual acuity. It may also be an adaptation in humans to prevent retinal cancer.

What animals can see UV light?

So, without further ado, here are some of the most notable animals that can see in UV light. This list is far from exhaustive and is in no particular order.

1. Butterflies can see in UV

Butterflies are one member of the animal kingdom that can actually see in ultraviolet. In fact, they are believed to have one of the widest visual ranges of any animal alive today.

Part of the main driver for this ability is their symbiotic relationship with plants. Plants and butterflies have adapted to one another to maximize the chance of pollination and nectar availability for butterflies.
RELATED: UV LIGHTS FROM MASSIVE POT FARM TURNS THE SKY PURPLE IN ARIZONA
Butterflies also use UV markings that they use to, for example, help find healthy mates. Markings can also make certain species of butterflies appear similar to potential predators while simultaneously allowing members of each species to differentiate between one another.

"The ultraviolet patches on some butterflies are directionally iridescent so that they appear to flicker in flight. This flickering is thought to have an important role in butterfly behavior and communication." - webexhibits.org.

2. Reindeers are able to see in UV

Some higher animals can also see in UV. One example is reindeer.

They have been found to rely on UV light to spot lichens that they can eat. According to an article in New Scientist, this adaptation occurred in response to their migration to Arctic regions over 10,000 years ago.

"The frozen wastes of the Arctic reflect around 90 percent of the UV light that hits them; snow-free land typically reflects only a few percent." - New Scientist.

They can also use light in the UV part of the spectrum to spot UV-absorbent urine from predators during winter.

"Very few mammals see UV light. Rodents do and some species of bat do, but we have no idea why they have developed this capability," says Glen Jeffery of the University College London.

"This is the first time we have got a real handle on why a mammal uses UV light."

3. Some birds feed their young using UV

A species of bird, called European rollers ( Coracias garrulus) have been found to also be able to see UV light. While this is apparently quite common in many bird species, scientists were never really sure why before.

One team of researchers in Spain were able to find that for European rollers, one use is to help identify stronger and weaker members of their brood. They are able to check, using UV, to see which ones are healthier and which are weaker.

By studying the young of the species, scientists found that the foreheads of heavier chicks reflected less UV than weaklings. This, it appears, is used to identify at a glance which chicks need more food than others.

4. Some birds also UV to find mates and hunt

Some species of birds have been found to use UV light to find potential mates. When seen under ultraviolet light apparent non-differences between male and female plumage can be quite striking.

"This impacts the study of bird behavior, and our grasp of how birds navigate during migration, classify objects, and interact socially and sexually. For example, some species we see as having identical male and female plumage differ when seen in the ultraviolet range - a difference apparent to the birds themselves." - webexhibits.org.

Some birds have also been found to use UV to spot tell-tale signs of their prey -- like urine or droppings.

5. Bees can see in UV

Much like butterflies, bees have also evolved symbiotically with certain flowering plants. One example is the flowers of Black-eyed Susans.

This plant's petals appear yellow to use lowly-humans, but to bees the look very different indeed. Under UV light, the flower's petals form a bulls-eye like design that is very attractive to certain pollinating bees.

"The bright colors of flowers (and patterns in the reflected UV, or ultraviolet, energy) attract bees to flowers and even to specific areas on the flowers. The bees like the flowers as a source of sweet nectar, which they process into honey for their food. The flowers like to attract the bees so that pollen from their flowers can attach itself to the bees for a free ride to another flower." - rit-mcsl.org.

6. Sockeye salmon use UV to find food

There is a growing body of evidence that some fish species, like the Sockeye salmon ( Oncorhynchus nerka), can also see in UV. According to some research, they may use UV to find food.

What is odd though is that the UV-receptors in their eyes appear and then disappear at certain times in their lifecycle. It is believed that this coincides with the times of prominent feeding on zooplankton and smaller fish who likely show up better under UV light in youth.

7. Scorpions are highly visible in UV

Another species that may be able to see in UV are scorpions. Under UV light, they appear incredibly bright, but scientists are not entirely sure why.

To animals who can't see in UV, this is obviously not a problem. But what advantage could this convey to them?

To any potential predator, who can see in UV, this would be a grave disadvantage to their survival. Unless it works as a form of warning.

8. Cats and dogs might be able to see in UV too

Dogs and cats may also be able to see in the UV part of the EM spectrum. While both can show some very odd behavior at times, sparking myth that cats may be able to see the dead, it could have a less supernatural explanation.

In fact, as we have seen, there are quite a few animals who have the same ability. Humans, for some reason, have lost, or never had it.

As they can actually see things we can't, it is natural for humans to find some of their behavior a little odd.

9. Hedgehogs also have UV vision

And lastly, but by no means least, is the humble hedgehog. These elusive nocturnal mammals have also been shown to be able to see using UV.

"A study by Ronald Douglas and Glen Jeffrey published in the in 2014 found that hedgehog lenses transmitted a significant amount of UVA light, suggesting they may have a vision in the UV spectrum despite lacking a specific UV pigment." - Proceedings of the Royal Society B wildlifeonline.me.uk.

It is believed that it helps them navigate at night, find their food, and spot potential predators.

# data[].attributes.attachment_link.description
You might be surprised to learn that many animals are actually able to see into the UV part of the EM spectrum. From insects to fish and even certain species of mammal, this trait is quite common. We humans, on the other hand, appear to either lost it or never had it in the first place.

# data[].attributes.attachment_link.readable_text
You might be surprised to learn that many animals are actually able to see into the UV part of the EM spectrum. From insects to fish and even certain species of mammal, this trait is quite common.

We humans, on the other hand, appear to either lost it or never had it in the first place. To them, our visual world would look very alien indeed.

Quite why this case is still a matter of debate, but it may well be a compromise for our fairly sophisticated visual acuity. It may also be an adaptation in humans to prevent retinal cancer.

What animals can see UV light?

So, without further ado, here are some of the most notable animals that can see in UV light. This list is far from exhaustive and is in no particular order.

1. Butterflies can see in UV

Butterflies are one member of the animal kingdom that can actually see in ultraviolet. In fact, they are believed to have one of the widest visual ranges of any animal alive today.

Part of the main driver for this ability is their symbiotic relationship with plants. Plants and butterflies have adapted to one another to maximize the chance of pollination and nectar availability for butterflies.
RELATED: UV LIGHTS FROM MASSIVE POT FARM TURNS THE SKY PURPLE IN ARIZONA
Butterflies also use UV markings that they use to, for example, help find healthy mates. Markings can also make certain species of butterflies appear similar to potential predators while simultaneously allowing members of each species to differentiate between one another.

"The ultraviolet patches on some butterflies are directionally iridescent so that they appear to flicker in flight. This flickering is thought to have an important role in butterfly behavior and communication." - webexhibits.org.

2. Reindeers are able to see in UV

Some higher animals can also see in UV. One example is reindeer.

They have been found to rely on UV light to spot lichens that they can eat. According to an article in New Scientist, this adaptation occurred in response to their migration to Arctic regions over 10,000 years ago.

"The frozen wastes of the Arctic reflect around 90 percent of the UV light that hits them; snow-free land typically reflects only a few percent." - New Scientist.

They can also use light in the UV part of the spectrum to spot UV-absorbent urine from predators during winter.

"Very few mammals see UV light. Rodents do and some species of bat do, but we have no idea why they have developed this capability," says Glen Jeffery of the University College London.

"This is the first time we have got a real handle on why a mammal uses UV light."

3. Some birds feed their young using UV

A species of bird, called European rollers ( Coracias garrulus) have been found to also be able to see UV light. While this is apparently quite common in many bird species, scientists were never really sure why before.

One team of researchers in Spain were able to find that for European rollers, one use is to help identify stronger and weaker members of their brood. They are able to check, using UV, to see which ones are healthier and which are weaker.

By studying the young of the species, scientists found that the foreheads of heavier chicks reflected less UV than weaklings. This, it appears, is used to identify at a glance which chicks need more food than others.

4. Some birds also UV to find mates and hunt

Some species of birds have been found to use UV light to find potential mates. When seen under ultraviolet light apparent non-differences between male and female plumage can be quite striking.

"This impacts the study of bird behavior, and our grasp of how birds navigate during migration, classify objects, and interact socially and sexually. For example, some species we see as having identical male and female plumage differ when seen in the ultraviolet range - a difference apparent to the birds themselves." - webexhibits.org.

Some birds have also been found to use UV to spot tell-tale signs of their prey -- like urine or droppings.

5. Bees can see in UV

Much like butterflies, bees have also evolved symbiotically with certain flowering plants. One example is the flowers of Black-eyed Susans.

This plant's petals appear yellow to use lowly-humans, but to bees the look very different indeed. Under UV light, the flower's petals form a bulls-eye like design that is very attractive to certain pollinating bees.

"The bright colors of flowers (and patterns in the reflected UV, or ultraviolet, energy) attract bees to flowers and even to specific areas on the flowers. The bees like the flowers as a source of sweet nectar, which they process into honey for their food. The flowers like to attract the bees so that pollen from their flowers can attach itself to the bees for a free ride to another flower." - rit-mcsl.org.

6. Sockeye salmon use UV to find food

There is a growing body of evidence that some fish species, like the Sockeye salmon ( Oncorhynchus nerka), can also see in UV. According to some research, they may use UV to find food.

What is odd though is that the UV-receptors in their eyes appear and then disappear at certain times in their lifecycle. It is believed that this coincides with the times of prominent feeding on zooplankton and smaller fish who likely show up better under UV light in youth.

7. Scorpions are highly visible in UV

Another species that may be able to see in UV are scorpions. Under UV light, they appear incredibly bright, but scientists are not entirely sure why.

To animals who can't see in UV, this is obviously not a problem. But what advantage could this convey to them?

To any potential predator, who can see in UV, this would be a grave disadvantage to their survival. Unless it works as a form of warning.

8. Cats and dogs might be able to see in UV too

Dogs and cats may also be able to see in the UV part of the EM spectrum. While both can show some very odd behavior at times, sparking myth that cats may be able to see the dead, it could have a less supernatural explanation.

In fact, as we have seen, there are quite a few animals who have the same ability. Humans, for some reason, have lost, or never had it.

As they can actually see things we can't, it is natural for humans to find some of their behavior a little odd.

9. Hedgehogs also have UV vision

And lastly, but by no means least, is the humble hedgehog. These elusive nocturnal mammals have also been shown to be able to see using UV.

"A study by Ronald Douglas and Glen Jeffrey published in the in 2014 found that hedgehog lenses transmitted a significant amount of UVA light, suggesting they may have a vision in the UV spectrum despite lacking a specific UV pigment." - Proceedings of the Royal Society B wildlifeonline.me.uk.

It is believed that it helps them navigate at night, find their food, and spot potential predators.

# data[].attributes.attachment_link.description
You might be surprised to learn that many animals are actually able to see into the UV part of the EM spectrum. From insects to fish and even certain species of mammal, this trait is quite common. We humans, on the other hand, appear to either lost it or never had it in the first place.

# data[].attributes.headline
This worm has no eyes but it can respond to light

# data[].attributes.subject
This worm has no eyes but it can respond to light

# data[].attributes.attachment_link.readable_text
Light-Sensitive Nematodes

Nematodes are fascinating creatures. They can survive in almost any habitat, with some of the microscopic organisms living as parasites on animals and some latching onto plants. We now have another reason to be fascinated by these humble roundworms: they can sense light better than humans.

In a study conducted in 2008, researchers observed that nematodes would avoid light when it hit them even though they lacked eyes to detect the light. In a new study published in the journal, researchers looked into why and found that the worms contain a light-sensitive protein, or photoreceptor, unlike any found in any other animal.

The protein is called LITE-1, and it is different from opsin and cryptochrome, the only two previously identified photoreceptors found in animals, because it is from the taste receptor family. While they thought maybe LITE-1 was simply "tasting" the chemical byproducts unleashed when UV light hit its host animal's body, further testing lead the researchers to conclude that the protein is indeed a photoreceptor capable of detecting UV light. Not only that, it is actually 10 to 100 times better than the human eye at detecting light in the visible spectrum.

Protection from UV Rays

Skin cancer is the most common type of cancer in the United States. In 2013, around 71,943 people in the country were diagnosed with melanomas of the skin and 9,394 people died from them. These deadly skin disorders are mostly caused by excessive sun exposure. Because LITE-1 can absorb both UVA and UVB light, scientists could potentially use it to produce improved sunscreens that can capture UV light much more effectively than conventional ones.

While we continue to create new treatments and medicines in labs, this research shows that some of the best solutions for our health problems could already exist in nature. If a previously unknown protein from a microscopic worm could improve the mortality rate associated with melanomas, what other answers to our medical problems have we not yet discovered?

Care about supporting clean energy adoption? Find out how much money (and planet!) you could save by switching to solar power at UnderstandSolar.com. By signing up through this link, Futurism.com may receive a small commission.

# data[].attributes.attachment_link.title
Worms Without Eyes Can Sense Light 100 Times Better Than Humans

# data[].attributes.attachment_link.description
Researchers have discovered a new photoreceptor protein in worms that is 10 to 100 times better than the human eye at detecting light in the visible spectrum. The protein could lead researchers to develop better sunscreens to prevent skin cancer, the most common type of cancer in the United States.

# data[].attributes.headline
Swallowtail butterflies can see with their tummies!

# data[].attributes.subject
Swallowtail butterflies can see with their tummies!

# data[].attributes.body
Swallowtail butterflies can see with their rear ends. More specifically, they have two light-sensitive neurons called photoreceptors on their abdomens... Researchers painted the photoreceptors on pregnant females' abdomens and released the butterflies into a cage with a potted lemon tree. The insects successfully laid eggs on leaves 14 percent of the time, much lower than their usual 81 percent success rate, confirming that female swallowtails depend on their hindsight to confirm that they have properly extended their ovipositor—the organ with which they attach eggs to leaves.
Source: https://www.scientificamerican.com/article/seeing-without-eyes/

# data[].attributes.attachment_link.readable_text
Advertisement

Light bathes our planet, splashing off the mountaintops, flooding the deserts, tundra, savanna and forests, and seeping as deep as 1,000 meters into the ocean. Bacteria, plants, animals and all kinds of living things have evolved different ways to detect and respond to light. Despite their familiarity and prevalence, eyes are not essential.

Biologists have known for several decades that some eyeless animals perceive light. Likewise, some animals with eyes-even rather sophisticated eyes-rely on other body parts to see. Exactly how organisms sense light without eyes has, in many cases, remained mysterious. In recent years, with the help of new tools like genome sequencing, scientists have discovered light-sensitive cells and proteins in unexpected places, and have established that creatures once thought to be blind can in fact see. Light-reactive proteins cover the ends of a sea urchin's feet, for example, possibly turning the spiky animal's whole body into a compound eye. Similarly, tiny jellyfish-like hydras can sense light with their stinging tentacles. And although nematodes live in darkness underground, some of their neurons respond to light, helping them wriggle away from danger.

View a slide show of animals that see without eyes.

These new insights are changing how biologists understand the evolution and function of vision. Two important questions are when light-sensitive proteins first evolved and in what ways animals originally used these proteins. Another question is whether complex eyes evolved many times in different groups of animals or if later generations inherited and tinkered with a single primitive eye archetype. Although biologists do not yet have definitive answers to these inquiries, it's already clear that vision and light-detection are older, more diverse and more widespread than researchers previously realized. Here are six striking examples of animals that have surprised researchers with eyeless sight.

SEA URCHINS
Sea urchins respond to light in various ways: they might change color, twitch their spines or move toward or away from light. Scientists have known as much for a long time, but they were never certain how urchins detect light, because no known species has eyes of any kind. Their best guess was that the net of nerves enveloping an urchin's body included some diffuse light-sensitive tissue. The remarkable truth is that sea urchins have a much more organized visual system than anyone expected.

When researchers sequenced the genome of the purple sea urchin ( Strongylocentrotus purpuratus), they were surprised to discover a number of genes important for the development of the vertebrate retina-the thin sheet of light-sensitive tissue that lines the back of our eyes. Maria Arnone of the Stazione Zoologica Anton Dohrn in Italy and her colleagues revealed that the ends of an urchin's tubular feet are pockmarked with opsins, the same light-sensitive proteins our own eyes depend on. When certain wavelengths of light hit an opsin protein, it changes shape, triggering a chemical cascade that opens tiny gates in cell walls called ion channels. Depending on the animal, this sequence of molecular events results in a reflexive behavior-like moving toward or away from light-or informs the nervous system about some aspect of vision. A sea urchin's hundreds of feet may act as one giant compound eye, allowing them to see just as well as a horseshoe crab or nautilus, both of which have genuine, if primitive, eyes.

HYDRAS
Hydras, tiny relatives of jellyfish, look like dandelion seeds: they have thin tubular bodies crowned with slender tentacles. They usually cling to weeds, stinging and eating even tinier aquatic invertebrates that swim by, such as water fleas (daphnia). Like sea urchins, hydras also respond to light even though they lack eyes. When scientists sequenced the genome of Hydra magnipapillata, they found plenty of opsin genes.

Recently, scientists confirmed that hydras have opsins in their tentacles, specifically in their stinging cells, known as cnidocytes. David Plachetzki of the University of California, Davis, and his colleagues showed that hydras respond not only to touch and chemicals, but also to changes in the light in their immediate environment. Hydras sting with greater force in dim light than in bright light, perhaps because they have evolved to recognize shadows as signs of prey or predators-the more they fire in the presence of a shadow, the likelier they are to hit their targets.

Hydras belong to one of the oldest groups of animals on the planet, the Cnidarians. Although hydras do not have eyes, other members of their family have simple eyes called ocelli. Box jellyfish have remarkably sophisticated eyes with lenses and retinas. The fact that hydras, which evolved much earlier than most Cnidarians, can detect light with their tentacles suggests that the origins of vision stretch further back in time than anyone realized. Later, jellyfish and other animals may have modified these existing, primitive visual systems to form more complex eyes.

SQUIDS, CUTTLEFISHES AND OCTOPUSES
Octopuses have large eyes and humongous occipital lobes-the parts of the brain that process vision. These wily, squishy marine masters of disguise can match the texture, color and patterns of almost anything in their environment. But they cannot see color-at least not with their eyes. The octopus eye is technically color-blind. So is the eye of the cuttlefish, a related mollusk.

Roger Hanlon of the Marine Biological Laboratory in Woods Hole, Mass., and his colleagues recently discovered that cuttlefishes actively express opsin genes throughout their skin, particularly in their fins and underbellies. And Desmond Ramirez of the University of California, Santa Barbara, has detected opsin genes in octopus skin. Octopus, squid and cuttlefish skin is also peppered with chromatophores-elastic sacks of pigment that expand and retract, allowing the mollusk to change its color. Other cells called iridophores and leucophores make the skin more or less reflective. Hanlon and his colleagues propose that opsins work with chromatophores, iridophores and leucophores in an unknown way to detect and mimic the color of nearby objects.

C. ELEGANS
Caenorhabditis elegans-tiny worm-like nematodes-live in complete darkness in the soil, so scientists assumed they could not perceive or respond to light. When X. Z. Shawn Xu of the University of Michigan and his colleagues shined beams of bright light at the nematodes' heads, however, they stopped inching forward and reversed direction. When the researchers flashed light at the tail or body of a nematode moving in reverse, the creature began wriggling forward instead. By annihilating various neurons in the nematodes' heads with a laser, Xu and his colleagues identified four cells without which C. elegans cannot perceive light. The researchers propose that avoiding light is an adaptation that helps nematodes stay in the soil, out of which they will not survive long (unless scientists keep them alive in the lab).

In later work, Xu and his team showed that the light-sensitive neurons in nematodes do not depend on opsins. Rather, they use LITE-1, a protein that functions as a taste receptor in invertebrates. A separate team of scientists discovered that neurons in fruit fly larvae detect light with a protein highly related to LITE-1. Like nematodes, it's advantageous for fly larvae to remain in the shadows, unexposed to harsh light and predators.

SWALLOWTAIL BUTTERFLIES
Japanese yellow swallowtail butterflies can see with their rear ends. More specifically, they have two light-sensitive neurons called photoreceptors on their abdomens, right next to their genitals. Kentaro Arikawa, now at The Graduate University for Advanced Studies in Japan, discovered that these light detectors are essential for swallowtail butterfly sex and reproduction. When yellow swallowtails mate, they precisely align their genitals while facing away from one another. Usually, the butterflies successfully complete their mating dance about 66 percent of the time. When Arikawa and his colleagues destroyed the photoreceptors on males' abdomens with heat, or covered the eyelets with black mascara, the insects mated successful only 23 to 28 percent of the time.

In a related study, Arikawa and his team ablated or painted the photoreceptors on pregnant females' abdomens and released the butterflies into a cage with a potted lemon tree. The insects successfully laid eggs on leaves 14 percent of the time, much lower than their usual 81 percent success rate. Together the evidence suggests that male swallowtail butterflies rely on light-detection to cozy up to females during mating and that female swallowtails depend on their hindsight to confirm that they have properly extended their ovipositor-the organ with which they attach eggs to leaves.

SCORPIONS
Scorpions instinctively avoid light. During the day, the eight-legged arachnids seek shelter beneath rocks, in underground crevices or in people's boots. At night they emerge to hunt small insects. Scorpions detect light, and may even perceive images, with two main eyes atop their heads as well as up to five pairs of nearby smaller eyes. Recently, scientists investigated whether scorpions can detect light with their skin as well. The answer is a preliminary yes.

Most scorpion species have a dark, waxy exoskeleton that looks like black or amber armor in daylight. If certain wavelengths of ultraviolet light strike a scorpion, however, it glows an eerie neon turquoise because of fluorescent molecules in its cuticle. Biologists have speculated that this fluorescence might help scorpions lure prey or warn predators to stay away; alternatively, the sheen might be an inevitable physical property of scorpion skin that offers no adaptive benefit.

Douglas Gaffin of the University of Oklahoma exposed 40 scorpions from Texas to both green light and UV light. Half the time the animals wore tiny aluminum foil eye patches; the other half their eyes were unobstructed. The scorpions were much less active under green light when their eyes were covered compared with when they were unmasked, but they were similarly active under UV light regardless of whether their eyes were exposed. One interpretation of this pattern is that scorpions change their behavior in response to UV light even when they cannot see with their eyes because their skin detects UV on its own. Another possibility is that scorpions somehow perceive the green light from their armor's turquoise fluorescence. Using its entire body to sense light, rather than its eyes alone, might improve a scorpion's chances of finding shelter during the day.

ABOUT THE AUTHOR(S)

Ferris Jabr is a contributing writer for Scientific American. He has also written for the New York Times Magazine, the New Yorker and Outside.

Follow Ferris Jabr on Twitter

Credit: Nick Higgins

Recent Articles by Ferris Jabr

# data[].attributes.attachment_link.title
Blindsight: Animals That See without Eyes [Slide Show]

# data[].attributes.attachment_link.description
Light bathes our planet, splashing off the mountaintops, flooding the deserts, tundra, savanna and forests, and seeping as deep as 1,000 meters into the ocean. Bacteria, plants, animals and all kinds of living things have evolved different ways to detect and respond to light. Despite their familiarity and prevalence, eyes are not essential.

# data[].attributes.attachment_link.title
How Fish Reproduce | Exploring the Deep Blue Ep. 5

# data[].attributes.attachment_link.title
Sturgeon facts: an anadromous fish | Animal Fact Files