Instant SOUL: the theory of shooting

Water shooting fish: this is a special water spraying technique!

We often have the impression that they are cool, calm, and attach a blow to the enemy. They can lie in the grass for several hours, just to trigger the trigger for the moment. Such a group of sniper experts are also found in the waters of southeast Asia. They are extremely skillful and even better than humans. These shooters are toxotes jaculatrix ). Stefan Schuster from the University of Bayreuth in Germany recently unveiled the mysteries behind each precise shooting of Water-Shooting fish, the research paper is published in Current Biology.

Water-Shooting fish, as the name suggests, are a kind of technical stream that relies on the injection of water bombs from the mouth, from a long distance to kill prey, and then easily kill prey. They have a length of less than 20 cm, but the range can reach about two meters. Shster is very interested in the water-Shooting fish prey process. "In order to kill prey, water-Shooting fish must quickly complete the force process and quickly hit the water. But how can they achieve a terrible range of 2 meters? To answer this question, we decided to carefully study the details of the shooting process, especially the trajectory of Water bullet in the air ." Shster told guokan.

Close-up of the slow action of the Water-Shooting fish. Original video source:Current Biology, GerullisEt al.

To complete this task, Shuster needs to use a camera to quickly capture the water bullet path and the situation of the water-Shooting fish mouth. Shster has been specially trained on the water-shooting fish. The water-Shooting fish must be shot in a specific "swimming Lane" with a length of 20 cm and a width of 8. 5cm to facilitate shooting. At first, water-Shooting fish do not stop in the swimming Lane, but if they are shooting outside the swimming Lane, the water bullet will be blocked by the polyvinyl chloride (PVC) board, and if they complete the prescribed action in the swimming Lane, food is given as a reward. Over time, all water-Shooting fish prey only in the swimming Lane, and every action of them can be recorded by the camera at the best angle.

This special training is the biggest challenge that shster faces in this experiment. "For our experimental fish, the biggest difficulty is that they should be shooting at the specified position, it must be completed with strong illumination interference-we need such light to ensure the quality of photography." "After such training, we not only have a good understanding of the position and shooting direction of the fish, it can also capture some details under high-resolution photography, such as the oral diameter of the fish during shooting and the detailed orbit of the Water bullet."

During a shooting process, the water-Shooting fish first quickly compress their cylinder and form a "Gun-shell" structure in the mouth. The upper part of this "Muzzle ve" is divided into a groove of the upper part, and the lower part is filled with a hard ridge protruding on the tongue. Because water bombs are highly concentrated after such a muzzle before being sprayed, the accuracy of water shooting fish is also increased. Similar structures also exist in the "water gun" of mammals-boys should have a deep understanding when going to the bathroom.

The oral diagram of the fish. G (groove): a groove of the upper jaw; R (ridge): The protruding ridge of the tongue; t (tongue): the tongue. Source: Thomas Schlegel, Christine J. Schmid, Stefan Schuster (2006)Current Biology

After studying the "water bullet" path, Shuster found that the water-Shooting fish will flexibly adjust the shooting intensity for the targets at different heights to ensure that the injected water flow gathers before hitting the target, it becomes a "water bullet", enhancing its impact, and maximizing the shooting efficiency of water-Shooting fish. Shster detected the surface tension of the Water bullet and found that it was the same as the normal water. This also means that the water shooting fish are completely taken from the ground and there is no "feeding" in their water bullet. Shster was surprised by the result: "We originally expected the water-Shooting fish to change the water viscosity through some chemical ways, but the results show that, the pure physical method is used to complete the shooting. For prey of different heights, the water flow they emit is not simply aggregated at a fixed position, but is adjusted flexibly and converted to a water bullet before hitting the target ."

The figure shows the path of water running in the air when a water-Shooting fish shoots 60cm of prey. The water flow still exists in the normal fluid form before 30cm on the left side, and the right figure shows the moment when the target is hit, the water that leaves the mouth cavity later "catches up" the part that leaves the mouth cavity earlier and completes the water bullet gathering. Image Source: Peggy gerullis and Stefan Schuster (2014)Current Biology

Shuster further analyzed the mouth of the Water-shooting fish. It was found that the upper jaw of the Water-Shooting fish was strictly fixed on the surface of the water during each attack. During the 313 shooting statistics, no vertical displacement has been performed once on the upper jaw of the fish. They only aim a little horizontally and then adjust the shooting angle for prey of different heights. These data once again demonstrate the stability and accuracy of the Water-Shooting fish. This amazing "Psychological Quality" may benefit from a complex natural environment-in a real wild environment, it is rare to go into the shooting range and be shot down, suitable for eating prey. To survive, they must have such shooting efficiency. "I think the water jet cutting technology may be improved as a result. To improve cutting efficiency, we usually add an abrasive or water pressure, but if we can concentrate the power of the water jet just like a water jet, we may benefit more from this technology. We hope to be able to participate in this specific improvement ."

Shooting water fish is the most talented shooter in nature. Their calmness and accuracy are staggering. Shster hopes to continue studying the secrets behind these talents. "We want to know how this shooting capability affects the evolution of the brain of the Water-fired fish. Throttling is a special talent that distinguishes humans from other animals. We can accurately calculate the throwing time ." "It is widely believed that this capability expands our brain capacity because we need more neurons to ensure this accuracy," shster said. Such inferences may also be applied to water-Shooting fish ."

In addition, shster, curious about these shooters, said: "How does the water-Shooting fish fix their shooting positions and angles so well, and how does it change the water flow path by just relying on the nozzle, it is also an exciting research direction."

The whole process of water-Shooting fish hunting. Video Source: Ingo rischawy Schuster lab, University of Bayreuth

 

References:

1. Gerullis and Schuster, archerfish actively control the hydrodynamics of their jets,Current Biology(2014)

2. Thomas Schlegel, Christine J. Schmid, Stefan Schuster, archerfish shots are evolutionarily matched to prey adhesion,Current Biology(2006)

Instant SOUL: the theory of shooting