Imagine the world is gray and a little blurry, as if your poor peripheral vision has taken over. This blurry field of vision extends so far that you can also see the dim shapes and movements behind you; no need to turn your head. One highlight is the X-shaped color splash that moves with your gaze. In the center of this splash, everything is clear and clear—a small window that presents sharp, colorful details in a thin gray landscape.
Add some blades of grass the size of a sequoia tree and you'll learn what the world looks like through the eight eyes of a jumping spider. This can be a bit like watching a poorly focused black-and-white movie on a 3-D IMAX screen that surrounds a room, and you put the spotlight anywhere it's pointed at it, and it emits high-definition colors. In other words, it's really, really weird, at least compared to the human perspective of our two eyes.
Jumping spiders belong to the jumping spider family, best known for their cheerful and gorgeous mating dances, their large forelights for cute close-ups, and their small size — some of the more than 6,000 known jumping spiders are smaller than sesame seeds.
But scientists have found that these smaller arachnids are much more than that. Through innovative experiments, the researchers gained insight into the spiders' lives, exploring their ability to see, feel, and taste to understand what it was like to be another animal.
Jumping spiders have a unique way of perceiving the world.
Nathan Morehouse, a visual ecologist at the University of Cincinnati, said: "Part of the reason I study insects and spiders is that this imagination is necessary to really try to enter a completely alien world and the thoughts and perceptions of reality of these animals. ”
<h1 class="pgc-h-arrow-right" data-track="7" > the eye of the spider</h1>
Unlike the compound eyes of bees and flies, which combine information from hundreds or thousands of lenses into a single, pixelated mosaic image, the eyes of the jumping spider resemble the eyes of humans and most other vertebrates. Each eye of the spider has a lens that focuses light onto the retina.
The main eyes—those that simply require us to anthropomorphize the large eyes—have incredibly high resolution for organisms that are typically between 2 and 20 millimeters long. Their eyesight is sharper than any other spider's, which is also the secret of their ability to track and pounce on their prey with impressive precision. Their vision is comparable to that of larger animals such as pigeons, cats and elephants. In fact, human vision is only five to ten times better than that of a jumping spider.
The eight eyes of a jumping spider, magnified on it with a scanning electron microscope, combine to see the world at nearly 360 degrees.
Ximena Nelson, an animal behavior researcher who studies jumping spiders at the University of Canterbury in Christchurch, New Zealand, said: "Given that you can accommodate a lot of spiders in one human eyeball, this is pretty remarkable. "In terms of size, there's nothing comparable to the type of spatial acuity that a jumping spider's eye can achieve."
But that sharp field of vision covered only a small part of the spider's field of vision. Each of the two main eyes sees a narrow, boomerang-shaped world. Together, they form an "X" of high-resolution color vision. Adjacent pairs of smaller, less sharp eyes scan the wide field of view in black and white to observe things that require the attention of large, high-resolution eyes.
There are also two pairs of lower resolution eyes on one side of the spider's head that any human parent would envy. They let the spider monitor what was going on behind it, and a near-360-degree view was a real advantage for small animals that were both hunters and prey. In fact, a jumping spider might think our 210-degree view is rather pitiful.
But in other ways, the visual world of the jumping spider is not much different from ours. The animal's main eye and the first set of paraphrases work together in much the same way that our two eyes have high-sensitivity central vision and low-resolution peripheral vision. Like spiders, we focus our attention on a relatively small area and largely ignore the rest until something catches our attention.
"I totally think they're perfectly similar," Nelson said. "The spider's solution is exactly the one we've adopted. They just adopted it in smaller ways. ”
<h1 class="pgc-h-arrow-right" data-track="15" > to the side eye</h1>
The four pairs of eyes of the jumping spider have their own responsibilities, each acting independently, but all working together. This collaboration opens up interesting research possibilities for Elizabeth Jakob, a behavioral ecologist at the University of Massachusetts Amherst. "I'm very interested in the way the eyes work together," she said.
Jakob uses modified eyeglasses to create the Spider Eye Tracker. Using removable adhesive, she tied a female Phadippus audax to the end of a small plastic rod. She then hung a stick with a spider in front of her eye tracker, which perched on a small ball facing the video screen. Once the spider is in place, Jakob plays the video. When the spider was observed, she recorded the reaction of the main eye.
The tracker emits infrared light to the retina of the main eye, while the camera records the reflected X-shaped field of view. The reflection is later superimposed on the video watched by the spider, revealing exactly what the spider's main eye is focused on. For humans, watching a combo video is like peeking into the spider's visual world through a portal.
Jacob combs through the relationships between the eyes by showing various images to different pairs of eyes. In a study published April 15 in the Journal of Experimental Biology, Jacob and her colleagues tried to determine which object the secondary eye saw that prompted the spider to swing its main eye for clearer observation. This test isn't just about exploring how the eyes work together; it gets what's important to the jumping spider.
"It's so much fun to see what grabs their attention," Jacob said. "Just let this little window into their minds."
First, the silhouette of the cricket — an attractive meal for the jumping spider — appears on the screen. You can tell when the spider's main eye is locked on the cricket, as the boomerang begins to swing, scanning the contours quickly while twisting slightly to one side and then to the other. The main eye of the spider can do this visual gymnastics because the retina sits behind two long, independently movable tubes, each controlled by six muscles.
To find out what might have taken the spider's attention away from the crickets, Jakob added additional images to the area of the screen located within the assist eye's field of view. Interested in a black oval? No. Maybe a black cross? Or another cricket? Didn't impress. What about a shrinking black ellipse? Still not. What if the ellipse gets bigger and bigger? Bingo: Boomerangs quickly fly over the ever-expanding oval for a better look.
One jumping spider's main eye can focus on preparing a raid dinner, while the other eyes will notice and ignore anything unrelated. But if those secondary eyes spot something getting bigger and bigger, then that could be a close predator that needs immediate attention. It's a beautiful design – it can make a person who is easily distracted jealous.
"We've been swimming in potentially stimulating oceans," Jacob said. One way to filter that information is to prioritize and focus on certain things rather than others. "It's certainly familiar to anyone trying to focus on reading one thing."
<h1 class="pgc-h-arrow-right" data-track="25" > how to see what the spider sees</h1>
A jumping spider perched on a foam ball (and fixed with a plastic stick and removable adhesive) watch the video,
And a special eye tracker records where the spider's main eye is looking. The researchers can see that when the white X lands on the cricket and stays on the cricket, the main eye of the jumping spider is focusing its main attention on the cricket silhouette, as shown in the video below. While the primary eye focused on crickets, the researchers added shapes, such as growing or receding ovals, to observe the secondary eyes. Only when the oval becomes larger does the main eye shift the focus to the oval. An object growing on the periphery may be a close predator
<h1 class="pgc-h-arrow-right" data-track="28" > focus color</h1>
Among mammals, humans and many other primates have extraordinary color vision. Most people can see three colors of light—red, blue, and green—and various hue combinations in between. Many other mammals usually only see some blue and green light. Many spiders may also have a rough color vision, but for them, it is usually based on green and ultraviolet light, which extends their vision to the deep purple end of the spectrum that humans can see, and covers shades of blue and purple. between.
But some jumping spiders see more. While at the University of Pittsburgh, a team led by Morehouse discovered that certain species had a filter between two layers of green-sensitive photoreceptors, which allowed the spiders to detect red light perceptions in a small area at the center of their primary field of vision. This added red, orange and yellow hues to their world, plus ultraviolet light, providing them with a wider range of rainbow colors than humans.
Seeing red is convenient because it is often used as a warning, in nature and in the human engineering world of red lights and stop signs. For jumping spiders, the ability to see red may have evolved as a way to avoid poisonous prey. However, once spiders can use this new world of color, they will make good use of it. "The evolution of color vision seems to have been accompanied by the rapid use of new colors that they can see when courting," Morehouse said.
Using Jakob's eye tracker, Morehouse is testing female jumping spiders to see how interested they are in the colorful, fanatical dances that males use to attract them. He found that suitors employ a combination of movement and color, seemingly specifically designed to capture and retain a woman's attention by playing with her various eyes. She can only see colors in the boomerang view of her main eye, and can only see shades of red, orange, and yellow in the center. Unless he could grab the attention of her secondary eyes with his movements, she wouldn't turn her main eye to him, and she might never see his colorful features. And for him, it can be a matter of life and death, because an unmoved woman may decide to cook with him.
The male of One species studied by Morhaus, Habronattus pyrrithrix, had a dazzling red face and beautiful gray-green front legs. However, the females seem to be most impressed by the orange knees on the third group of males' legs. When the male first spotted the female, he would raise his front legs as if directing a plane into the boarding gate and then skim left and right, hoping to get the attention of her second eye. As she turned to him, he leaned closer and began to flick the wrist joint at the end of his raised forelimb. You can almost hear him say, "Hey, ma'am, here it is!" ”
Once he caught her attention, the orange knee came out. "They move them from behind into view in a peek-a-boo way," Morehouse said.
To figure out what makes the male presentation change the female head, Morehouse uses some tricks. He made videos of men dancing and then played them to women sitting in eye trackers to see how each change affected her attention. If the man had an orange knee raised but not moved, she wouldn't be so interested. If the knee is moving but the orange is removed, she will look but will soon lose interest. He has to have the right look and the right movements.
"He used movements to influence where she looked, and then he used color to grab her attention," Morehouse said.
Lisa Taylor, a behavioral ecologist at the University of Florida gainesville, likens the strategy of males to that of human advertisers. "It feels like a lot of the tricks that marketers use to influence our decisions," Taylor said. "Understanding the psychology of spiders sometimes feels similar to understanding the psychology of humans."
<h1 class="pgc-h-arrow-right" data-track="38" > can you feel it? </h1>
The movement of waving the knee in a male courtship show is intended to attract the attention of women. But Damian Elias, a behavioral ecologist at the University of California, Berkeley, found that the dance was only part of the show.
Many spiders use vibrations to communicate, and there are some reports that jumping spiders are one of them. When Elias investigated further, he found that the male jumping spider's movements were accompanied by very fine vibrational serenades, sent through the ground to the females, beyond human perception.
"It was a complete surprise for me," Elias said. When he shared his findings with other spider scientists, "they were stunned. ”
To eavesdrop on spiders' seismic songs, Elias used laser vibrometers, similar to the techniques used in the aviation industry to measure the vibration of aircraft components. He tethered a female spider to the surface of a nylon that stretched like a drum face, and then added a male spider. When the male finds the female, it begins to sing and dance, its legs tapping on the surface of the water and vibrating its abdomen.
The vibrometer measures the vibrations of surfaces and converts them into airborne sounds that humans can hear, showing thumping, scraping, and hum. Elias is recording courtship videos at 1,000 frames per second at the same time, so he can slow down to see how sound and movement are synchronized. It's like a miniature drum solo that perfectly matches the spider's flicks and kicks.
"We wouldn't have been able to get that without technology," Elias says. "It's kind of like opening up this secret world."
<h1 class="pgc-h-arrow-right" data-track="45" > good vibration</h1>
Male jumping spiders strive to attract and maintain the attention of potential partners. By tapping the front leg and swinging the abdomen at different speeds (in hertz or hertz), men can produce three types of seismic signals that the researchers can obtain using laser resonance measurement.
The sensory world of the jumping spider is filled with vibrations coming from the ground. But because the sensation of these vibrations depends on what the spider is standing on, things quickly change when he jumps from leaves to rocks to soil.
For humans who perceive the vibrations of sound through the air rather than the ground, Elias imagines that this might be like taking two steps, suddenly listening in the water, and then taking two more steps, and you're surrounded by foam and then back in the air. The whole sensory world of spiders is constantly changing, but they will adapt without hesitation.
Now, take that alien world of hearing as an example, and add the fact that the tip of the jumping spider's leg also has a chemical sensor. "They walk around and taste everything they go," Elias said.
Little is known about this aspect of the jumping spider's sensory system, but the latest study from Taylor's Florida lab, published July 29 in the Journal of Spiderology, suggests that male spiders may want to taste traces of potential mates. Most jumping spiders do not form webs to catch prey. They tracked and pounced. But spiders constantly lower a silk thread as they walk around, a kind of safety rope in case they fall or need to escape quickly.
In the new study, a male H. Pyrrithrix could feel it as he stepped on the female silk thread. Taylor's lab is now testing whether male spiders can detect the difference between silk that leads him to virgin females who may be willing to mate with him and cables left behind by female spiders that have mated and may prefer to eat him.
"The more we learn, the more complex it becomes," Taylor said. Jumping spiders are very visual, there's a lot of vibrating stuff happening, and then chemistry. It's hard to imagine it won't just be super overwhelming. ”
Somehow, jumping spiders control the flood of senses very well— they live almost anywhere on Earth. You've most likely seen one, probably in your own house. Although they are small, they are easy to identify if you know what you are looking for or what they are looking for.
Nelson of the University of Canterbury said: "The next time you see a spider in the middle of the wall, you look at it, it turns around and looks at you, it's a jumping spider. "It detects with its auxiliary eye that you're moving towards it, and it's checking you."
The spider may just be imagining what the world looks like in the eyes of humans.
<h1 class="pgc-h-arrow-right" data-track="56" > Flying Tigers</h1>
One of the things that jumping spiders do with their unusually good eyesight is jumping. Spiders prefer to hunt rather than build networks to passively trap food. Their ability to swoop down quickly and accurately on insects and other spiders earned them the nickname "Flying Tiger" during China's Ming Dynasty more than 500 years ago.
Scientists are learning how apt that nickname is. At least one group of jumping spider species plans to carry out strategic attacks, including elaborate detours to reach targets — a clever hunting behavior often attributed to brain mammals like real tigers.
Starting from the middle tower of this platform, a jumping spider sets a route to reach the only box containing meals. She had to stay away from the target and couldn't see it
"Some of the things they do can keep you up all night." Kroos and Robert Jackson, a prominent spider expert also in Canterbury, have tested the group of species, including the clever Portia fimbriata, which faces various challenges in the lab. In one study, the team placed a spider on top of a tower on a platform surrounded by water (pictured) because they knew the spider would avoid the water as much as possible. From the perch, the spider could see two other towers: one with a box containing prey on top and a box of dead leaves on the other. Both can be accessed from the platform via a multi-turn raised walkway. After surveying the site, most of the spiders climbed down the tower and chose the correct path to the target – even if this required initially moving away from the target, not seeing the prey and first passing through the starting point of the wrong walkway.