![]() ![]() ![]() The peacock spider, for instance, flips up its colorful abdomen and thrusts a pair of legs in the air like a music-video backup dancer, Live Science reported. ![]() In many species, males flash their brilliant colors and shimmy in elaborate courtship displays. Mating is serious business for jumping spiders. Peacock spiders mating on a blade of grass. The 2012 research found that the spiders use this difference in focus to detect depth. But green light that hits one of those layers perfectly in focus will appear a teensy bit blurred on the other layer, and vice versa. In a jumping spider retina, the bottom two layers are both chock-full of green color receptors. Because different colors of light have different wavelengths, each layer catches a different color of light in precise focus. According to 2012 research, the spiders use something called "depth via image defocus." Here's how it works: Jumping spiders' retinas have four layers of photoreceptors. Jumping spiders can also see depth, in a "totally unusual" way, Morehouse said. Birds and reptiles often use this strategy to expand their color vision. Though the receptors aren't most sensitive to these wavelengths of light, they react to the stimulus anyway, cuing in the spider that red or orange is present. These pigments let only red wavelengths of light through. Other jumping spiders have hacked color vision by developing pigments that sit in front of their blue/green color receptors. Similar mutations allowed primates to develop color vision, Morehouse said. This extra copy has then acquired mutations capable of detecting red and orange. In some species, a random genetic mutation has introduced an extra copy of the gene that makes the proteins that allow for blue/green vision. These, Morehouse said, tend to be the flashier species, such as the paradise jumping spiders (genus Habbernatus), which are often decorated in shades of red and orange. Some species, though, have evolved special tricks to expand their color vision. Most species of jumping spider can see ultraviolet light and blues and greens. Meanwhile, the spiders' secondary pairs of eyes are less acute, but they provide crucial peripheral vision, Live Science previously reported. That means they can move retinas up and down, side to side, focusing on different segments of the world without a hint of movement on the outside, Morehouse said - a handy ability for a hunter. The spiders are also unusual in that they have muscles attached directly to their retinas. Their pair of central eyes, known as the principle eyes, are almost like a pair of tiny binoculars: They have a large outer lens, then a smaller inner lens that magnifies the image from the outer lens and projects it onto the retina. The spiders, despite their tiny size, are better at seeing patterns than elephants are, Morehouse told Live Science. Jumping spider eyes are, in a word, incredible. And they're distinguishable by their distinct eye pattern of four pairs of eyes, in which the large middle pair sits close together at the front of the face. They're usually small, often 0.5 inches (12.7 mm) or less in length. Jumping spiders do have a few things in common. ![]()
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