The flat rostrum of the fish-saw makes it invisible to the victims

The long and flat, seated with strong teeth on the snout of the stingrays of Pristidae forever fixed the name of the “fish-saw” behind them. Such rostrum developed in them for a reason: the upper plane of it is strewn with electrically sensitive cells and helps to keep track of what is happening over it. “Saw” is used both as a “shovel” to search for food in the ground, and as a dotted club with sharp teeth, swinging, the fish can fight off the enemy or immobilize the victim during the hunt.
The length of the rostrum can exceed a quarter of the length of the whole body of the fish. But how does it affect the swimming of these rays in the water? The Australian scientists have found this out: the biologist David Morgan (David Morgan), the engineer Sam Evans (Sam Evans) and their colleagues from the University of Newcastle. The results of this work they lead in an article published in The Journal of Fish Biology.
Scientists turned to the usual methods of modern engineering. They conducted a computerized tomography of rostrums of various types of sawtooth rays and compiled detailed 3D models of their shape. Models were used for computer simulation, during which the authors simulated the natural movements of the rostrum of a real fish-saw and figured out how the water flows around it. This made it possible to discover one more unexpected advantage of the sawtooth rostrum.
It turned out that a long flat outgrowth dissects water almost like a knife, without creating turbulent turbulence and vibrations of the environment – scientists compare it with the work of blades of modern wind turbines. These vibrations serve the fish (especially the bottom one, where water is usually rather turbid) one of the main sources of information and allows you to hide in time. However, against fish-saws, it helps worse: we can say that their rostrum was formed “by stealth technology.”
“These results show that the hardwood stingrays are effective invisible hunters that can remain unnoticed for sensory organs of the lateral line of their victims,” ​​the scientists conclude.

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