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The original title: "the amount of urination in a day is 300 times the body weight!" The "bouncing urine" skill it relies on for survival can even be used to launch spaceships.

Photo Source: Pixabay We may need to take a good look at an insect pee when it can be used to launch a spacecraft on a rocket.

Write article | clefable

Revision | Wang Yu

When Saad Bhamla and colleagues at the U.S. Department of Agriculture (USDA) studied a notorious insect, they might not have thought they would be impressed by the insect's ability to urinate, and published a top article, recently published in Nature Letters.

Saad Bhamla is a scientist who explores all kinds of interesting biological phenomena in nature. Photo: Georgia Institute of Technology bouncing urine speed, too fast this insect is the leafhopper, only a few millimeters long, usually inhabit among the branches and leaves of green plants, it is difficult to find them without looking carefully. But scientists cannot ignore the insects because the plant viruses they spread have posed a serious threat to the wine and citrus industries.

When Saad Bhamla, a biomolecule engineer at the Georgia Institute of Technology, first looked at the leafhopper, he and his doctoral student Elio Challita noticed that the little pest had been doing something over and over again, but could hardly keep up with the naked eye. They set up a high-speed camera and found that the leafhopper had been ejecting urine droplets at high speed. Because of this interesting behavior, they gave it a nickname-"sharpshooter" (sharpshooter).

The normal urination rate of leafhoppers. Photo source: youtube leafhoppers are actually very similar to mosquitoes, their food is all liquid, except that one is to draw blood from people or animals, and the other is to draw the "blood" of plants-xylem juice. Just as mosquitoes can spread diseases, leafhoppers can transmit some viruses when they are stuck in the epidermis of plants, causing plants to get sick.

For leafhoppers, plant xylem sap is far less nutritious than animal blood, 95% of which is water and is deficient in nutrients. Although mosquitoes may eat more easily, they risk death every time they eat; leafhoppers are caught in a different predicament-if they don't work hard to eat, they will definitely die. It is difficult to compare which is more difficult to survive between leafhoppers and mosquitoes. Bhamla and colleagues found that leafhoppers need to consume large amounts of plant xylem sap (equivalent to drinking only lemonade) every day to survive, and their daily urine output soars to 300 times their body weight. By contrast, a person's daily excretion is only 40 percent of his body weight.

Watching the leafhoppers live so hard, the researchers calculated their energy budget for the day. The first is energy income, and plant juices are the only energy they take in. The rest is energy expenditure, including the need to mobilize huge striated muscles in order to extract xylem sap at ≤-1Mpa, a process that consumes a lot of energy. Then, the leafhopper needs an efficient digestive system to absorb nutrients from the xylem liquid, which consumes a lot of energy-after this process, the liquid is "purified" into urine with up to 99% water content. it's really possible to be cleaner than Rain Water.

Skills necessary for survival in order to leave enough room for juice intake, leafhoppers also need to constantly remove fluids efficiently, which also requires energy consumption. After calculation, they found that leafhoppers consume a lot of energy in the process of ingesting juice and nutrients, while they use only a small amount of energy to urinate-so that they can survive without living beyond their means.

However, leafhoppers can't urinate nearby because they want to save effort, which may cause pathogens in urine to grow nearby and threaten their survival. In addition, some chemical pheromones in urine attract potential predators, such as parasitic wasps, the natural enemies of leafhoppers. Fortunately, leafhoppers are indeed a genius for saving urine-they can repeatedly achieve efficient urination by bouncing urine far away in a special way with ultra-low energy costs.

Before revealing in detail the voiding mechanism of leafhoppers, we can first understand the next common way of urination-jet. Scientists have found that animals with pores larger than 100 μ m, such as mammals, jetfish and large insects, rely on inertia to form jets or chunks of liquid during hunting or urination.

Leafhoppers' close relatives, cicadas, take this approach, but for leafhoppers, it consumes too much energy. Their method is to form urine droplets and then use super propulsion to eject them. Super propulsion is an engineering concept that means that elastic projectiles (such as urine droplets) on a super-hydrophobic surface can be ejected at a higher speed than the maximum speed of the super-hydrophobic surface.

Glass-winged sharpshooter Homalodisca vitripennis (photo: Wikipedia) in the lab, Bhamla et al studied the "glass-winged sharpshooter", a leafhopper called Homalodisca vitripennis (with transparent wings and a reddish-brown body), and looked closely at the structure of its body responsible for ejecting urine, revealing the complete process and details of it. They found that when a glass-winged sharpshooter urinates, its tail anal stylus (anal stylus) has an angle θ relative to its normal state, and the change in this angle reflects the three stages in which it ejects urine: forming urine droplets, loading elasticity, and spraying urine droplets.

At the bottom and head of the anal stylus are arthroelastin (resilin) and receptors (tail whiskers), respectively. In the stage of urine droplet formation, with the help of arthroelastin, the leafhopper anal stylus bends a larger angle, and then the urine droplets begin to be excreted, and the diameter of the urine droplets can reach about 0.73 mm after about 80 milliseconds. In this process, the angle of the anal stylus remains constant. As the urine droplet grows, the anal stylus bends about 15 degrees as it approaches the hairy receptor. This is the only way to finish loading the urine droplets.

The invention relates to a leafhopper and the specific structure of its tail, and the detailed process of ejecting urine droplets. The picture comes from the original paper.

The process of leafhopper ejecting urine droplets Photo: youtube then the urine droplets enter the launching phase. At the beginning of this phase, the receptors coordinate the frequency of the anal stylus and the droplets, and then the anal stylus accelerates rapidly. At the same time, the elastic urine is compressed and popped out quickly. How fast does the anal needle move? First of all, its acceleration can reach more than 40 times that of the cheetah (about 8cm / S2). Its peak angular velocity can reach 3.31 ±1.31 × 104 °per second (equivalent to 550.128 laps per second), and the peak linear velocity is 0.23m / s.

And the speed of urine drops is faster. In the state of urine droplet compression, the energy accumulated by surface tension will be transformed into its kinetic energy during flight, and the urine droplet will bounce out and fly far away at a linear speed of 0.32 m / s, which is about 40% faster than that of the anal needle-that is, super propulsion has been achieved. The leafhopper is the first insect observed in nature to take advantage of super propulsion, scientists have found.

The difference in body shape between the leafhopper (right) and its close relative (left) is very obvious, and the length of the leafhopper is even smaller than the width of the human pinkie. Photo Source: youtube has been saving energy. in order to save energy for urination, leafhoppers may have accurately calculated every step of the voiding process. First of all, compared with jet urination, the mode of excretion used by leafhoppers-- the formation of urine droplets-- consumes only 1 meter, 9 minutes, and 5 percent of the jet. Next, the leafhopper can also save energy by super-pushing the ejection of urine. What is essential is the hairy receptor at the end of the leafhopper's body.

In the experiment, the researchers tried to remove this receptor from Homalodisca vitripennis and re-observed how they ejected urine droplets. They found that leafhoppers could not coordinate the frequency of anal stylus and urine droplets, and even if the anal stylus moved very fast, the speed of urine droplets popping down significantly. Leafhoppers can no longer use super propulsion as they did before, and will consume more energy.

After removing the receptors from the tail of the leafhopper, it can no longer achieve super propulsion. The picture comes from the paper, and at present, after entering space, the separation of rocket and spacecraft using "magnetic thruster" and "electric thruster" also uses the method of super propulsion. Physicists have found that super propulsion can generate 250% more energy than normal launch methods, and the spacecraft can be accurately put into orbit in a more economical way.

I have to say that although the energy intake is limited, the leafhopper, the "master of engineering", has survived through austerity and has been very successful-there are probably more than 1000 species of leafhoppers in China, and eventually human beings have to take measures to reduce their harm. What makes people marvel most is its exquisite bouncing urine technique. "it's really amazing because physicists and engineers have proven the concept of superpropulsion in the lab, but this magical creature may have applied it hundreds of thousands of years ago," Bhamla said. "

In addition to the leafhopper, many insects have strange excretion phenomena. Scientists have also given these insects some apt names, such as "dung sprayers", "hip shakers" and "feces spitters". They are all using unusual strategies to discharge liquid or solid faeces.

As early as before 2003, some researchers found that caterpillars in the family Skippers can spray their solid feces as far as 153cm at a speed of more than 1.5m / s, nearly 40 times their body length. In the process, the caterpillar launches these loads with the help of rapidly rising blood pressure, allowing its hard back to act like a hatch. And the older the caterpillar is, the more experienced it is and the farther it can spray feces. I have to say, it's kind of like a walking "shit" machine.

In addition, nocturnal worms release fecal particles by violently shaking their abdomen, and some geometrid larvae kick them away with their chest legs. And all these strange actions are to avoid predators and survive smoothly.

Sometimes it's extremely troublesome to save some energy, but it's extremely easy to waste energy.

Reference link:

Https://www.science.org/content/article/frass-flies

Https://www.scientificamerican.com/article/sharpshooter-insects-use-superpropulsion-to-catapult-their-pee1/

Https://press.springernature.com/28-02-2023-nature-research-journals-16-00/24030988

Links to papers:

Https://www.nature.com/articles/s41467-023-36376-5

Droplet superpropulsion in an energetically constrained insect

This article comes from the official account of Wechat: global Science (ID:huanqiukexue)

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