Spider, 8 eyes and 8 legs.
Spiders with many and long legs run fast, and the fastest spider (common house spider, tegenaria domestica) has a running record of 0.53 m/s, which is equivalent to 33 times the length of its body per second. How fast is this for spiders with large fingernail shells? Convert to your height, you know, your height is 1.8 meters, and the running speed should be 59.4 meters per second. If you run at the speed of a home spider, you only need 1.68 seconds to run through 100 meters.
Unimaginable speed, not to mention humans, even the fastest running cheetah among mammals can't catch up with spiders. In addition to running, spiders can also jump. There is a large sect in the group called jumping spiders, and their bouncing power is amazing. Jumping spiders with a body length of less than 1 cm can jump 25 times the length of the body in the horizontal direction, and if you have its strength, you can jump 45 meters away from the ground.
A jumping spider that can run and jump, and the poisonous liquid can spit silk, it seems to have all-round skills. There is a jumping spider called myrmarachne formicaria in the school, but it is not willing to be a spider, only wants to be a small ant, in addition to looking as close as possible to the ant, the action will also imitate the ant walking on 6 legs.
The picture above is m.f. jumping spider, is it very similar to an ant? Let's first look at how the jumping spider learns how ants walk, and then why it imitates ants.
An important reason why spiders run faster and jump farther than you do is that they don't look like you, and their legs are not driven by muscles, but by hydraulics.
There are 3 kinds of muscles in your body, heart muscle, visceral muscle and skeletal muscle. The muscles attached to the bone are divided into flexors and extensors, the two muscles pull the bones in a confrontational manner, the flexor muscles contract, the joints will bend, the extensors will be strong, and the joints will be straightened.
Your body is supported by bones, and the spider has no bones in its body, its bones grow outside and grow into a hard shell. The material of the spider's exoskeleton is not calcium carbonate or calcium phosphate, but chitin, which is similar to the material of your nails and hair.
Spiders are arthropods, and arthropods mean legs with knots. You have two joints on your legs, knees and ankles, while spider legs have 7 joints. Multi-joint spider legs, only flexor muscles without extensors. One is that there is not enough room for muscle in the legs, and if the spider has a large and thick leg, the muscles will make it bulky and heavy. Another reason is that spiders are warmer animals and don't have enough energy to keep their leg muscles warm.
A spider with many joints and small legs, with a rounded body. The body is divided into two parts, the head and chest are fused together, and there is a belly with a large belly. Attention to detail: The spider's 8 legs are all connected to the cephalothorax, and the liquid stored in the cephalothorax drives the leg movements.
Spiders have very few leg muscles, but the leg shell is filled with fluid, which is much like blood, called hemolymph. As it moves, the flowing pressure of the hemolymphs stretches the legs and the flexor contraction closes the legs. It controls its heart rate to regulate fluid pressure, and the faster the heartbeat, the higher the pressure. After the spider dies, the hemolymphs stop flowing, the legs lose fluid pressure, and the 8 legs cannot be stretched, but can only curl up together.
8 legs driven by hydraulics, how to cooperate when walking, which leg is out first?
Looking at the figure above, the spider has 8 legs, divided into 1, 2, 3, 4 pairs, the step order is: left 1, right 2, left 3, right 4 and right 1, left 2, right 3, left 4, the interval of 1, 3 pairs of legs raised, the other 2, 4 pairs of legs landing to support the body.
The spider walks in pairs of legs, which is a little different from the way ants walk. The ant has 6 legs, only 3 legs on one side of the body, can not be lifted evenly like a spider, it adopts a triangular gait. Lift 1 leg on the left, 2 legs on the right, 3 legs up, and the other 3 legs to support the body, staggering forward.
The picture above shows the triangular stride of the ant, and most of the 6-legged insects walk in this way.
Now please look at the picture below, the black bug catching fruit flies in the bottle, walking in the 4 pairs of legs, or the triangular step of 3 pairs of legs?
Can't tell, well, then look at the following computer GIF, the bugs in the picture are spiders or ants, in which way to step?
Still can't see it, right? Answer: The black bug in the picture is a jumping spider, which imitates the walking of ants.
Seeing the way the jumping spider walked, everyone thought that it raised a pair of front legs and learned that ants could use the back 6 legs to step. Sometimes what your eyes see isn't necessarily the truth, though. The Cornell University team used a high-speed camera to shoot a video of the jumping spider walking, slowed down the video speed, and saw the truth of the jumping spider walking. The truth is different from what everyone thinks, the truth is that the jumping spider still walks on 8 legs.
Jumping spider with 8 legs, do not know how to walk with 6 legs. But it has a trick of periodically stopping while walking, lifting the front 2 legs, disguised as the tentacles of an ant. The jumping spider raises its front legs for 100 milliseconds, and the time delay of this pause is just right, which creates a visual illusion that makes us look like an ant walking on 6 legs.
The picture above shows the gait of 3 animals, with the ordinary jumping spider on the left, the jumping spider imitating ants in the middle, and the ant on the right. The jumping spider that imitates the ant is similar to the gait of the ordinary jumping spider, and the 4 pairs of legs walk alternately, the obvious difference is that when it is stationary, the front legs of the ordinary jumping spider will not move, while the front legs of the jumping spider imitating the ant will lift and cross and shake, imitating the movement of the ant's antennae.
Above are the footprints of three species of animals. A picture is the road traveled by ordinary jumping spiders, and b pictures are imitation of the footprints of jumping spiders. The footprints of ordinary jumping spiders are irregular, imitating the footprints of jumping spiders are unconventional, and they come out of the sine wave (wavelength is 10 times the body length, amplitude is 5 times the body length). The c graph is the footprint of the ant when it is not tracking pheromones, there is no regularity. The d-graph is the footprint left by the ants while tracking pheromones, with regular sine waves (wavelengths of 10 times the body length, amplitudes of 2 to 5 times the body length).
Ants come out of the regular sine wave as they track down pheromones left behind by other partners. The jumping spider, which imitates the walking of ants, although it does not walk on 6 legs like an ant, it learns the essence of ant walking and walks out of the sine wave footprint. This is the biggest difference between imitating jumping spiders and ordinary jumping spiders when walking, ordinary jumping spiders will not do this trick. [Headlines - France is Bacon - Please do not reprint other platforms without authorization]
The reason the jumping spider imitates an ant is simple: it deceives predators and makes predators think that it is an ant, not a spider. Although the Spider runs fast and jumps far and is equipped with Venom weapons, it still has many natural enemies. Large spiders, wasps, toads, lizards, and birds all prey on jumping spiders, and these predators do not like to catch ants to eat.
The jumping spider disguises itself as an ant, grows into the shape of an ant, walks like an ant, deceives the eyes of its predators, and it can escape the disaster.
What about the camouflage results of the jumping spider? Looking at the figure above, the green pillar on the left is the probability of the ordinary jumping spider being eaten, the middle blue pillar is to imitate the probability of the jumping spider's arrest, and the red pillar on the right is the probability of the ant being caught. The probability of being eaten by a jumping spider that imitates an ant is much smaller than that of an ordinary jumping spider, and it successfully deceives the predator.
In nature, it is common for one organism to imitate another, called mimicry. For example, an orchid will grow the flowers into the shape of a female bee, attracting male bees to come and cross their tails, thus spreading pollen. The general imitation of organisms is similar in appearance and shape and color on the static, while the jumping spider goes further and can learn the walking gait and trajectory of the ants, so that the dynamic behavior is similar.
When the predator stares at the imitation jumping spider, the jumping spider raises its front legs and poses to the predator: "Don't eat me, I'm an ant, don't believe I take two steps to show you." "The result is often averted.
Learn to learn, learn the essence to really gain. The jumping spider that learns to walk ants, although it does not walk exactly like ants, but it learns the essence of the ant's gait and successfully achieves its own purpose.
Jumping spiders that run fast and jump far, disguised as weak ants, interpret low-key is also a kind of king.
#科学有意思 #
Resources:
1： “walking like an ant: a quantitative and experimental approach to understanding locomotor mimicry in the jumping spider myrmarachne formicaria”，by paul s. shamble, et al.，proceedings of the royal society, 2017
2：“10 fascinating facts about spiders”，by debbie hadley
2：“how do spiders move?” ，by chris roh
3：“how spiders work”，by tom harris, animals how stuff works
P.S. Today I update the secret series of articles in nature, which is the 19th article: Spiders that learn to walk.