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It all started with a simple question: why manta rays do not fade from the throat?
According to Misty Paig-Tran, a marine biologist, kite-shaped fish filter their plankton-based food from seawater, but they do not stop, close their mouths and sniffle. their hooves. and professor at California State University, Fullerton. If their filters work like sieves, they must be clogged over time, like all similar systems, from vacuum cleaners to your water filter pitcher.
But the latest research by Dr. Paig-Tran and colleagues, published Wednesday in Science Advances, shows that the manta ray uses a previously unknown filtration method that causes the particles to slide on its constraint system rather than crossing it. It is not necessary to empty its filters because they are rarely clogged.
To understand how manta's filters work, imagine a series of small angled slats lined up in his mouth. According to the experience of Raj Divi, a student in Dr. Paig-Tran's laboratory, when seawater passes over these structures, it forms whirlpools between each pair of slats. These swirls do not suck the particles. Instead, they grow upward, preventing plankton fragments and other particles of the sea from falling into crevices.
As a result, the particles ricochet on the slats and concentrate in the mouth while the water flows. They never really get into the filter, according to the two laboratory experiments, washing dye and colored particles on plastic versions of structures and mathematical models of what's going on. They are bounced before being lucky and then swallowed by the beam.
This is not the first time researchers have discovered that filter feeders are probably not just sieves. According to a study examining this issue in whales, water can cross the front and back of giant mammal baleen at different speeds, causing a pressure differential that allows plankton to accumulate inside the mouth. . But other sea creatures seem to sift, like the basking shark, which sometimes closes the mouth and cleans his hooves with a kind of cough.
Understanding how the manta ray feeds and what it eats can help conservation efforts. "It's a protected animal that is harvested like crazy. And we do not even have a good idea of what they feed, "said Dr. Paig-Tran, noting that this could help to understand the organisms they depend on and if they ingest plastic particles floating in the water. 'ocean.
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It could also lead to filters for human use, based on this method. In the past, machines using intelligent engineering to avoid blockages during filtering have met with resounding success: some vacuum cleaners, for example, separate the dust from the air by centrifugal force, rather than a filter which accumulates with the particles.
Dr. Paig-Tran hopes this discovery will help fight microplastics in the ocean.
The tiny pieces of plastic can end up in wastewater, but they are not treated in wastewater treatment because they are not equipped for particles of this size. Manta rays, on the other hand, are effective at filtering on such a scale.
Imagine a hoof-resistant filter modeled on the manta's mouth and placed in a treatment plant to catch plastic fragments before they are released into the environment. For Dr. Paig-Tran, this seems like an intriguing potential use of the system that she and her colleagues have described.
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