[ad_1]
When Paig-Tran started studying mantas for the first time ten years ago, she tried to figure out what they were doing while swimming with them and showing them cameras. It did not work. "Mantas are very manageable and incredibly intelligent," she says. "They have the biggest brain-to-body ratio of all the fish and they do not want you to bother them." Specifically, she and her colleagues wanted to understand the specialized body parts that allow these fish to filter food.
Attach the head in a manta's mouth and you'll see five successive pairs of white V-shaped stems, remember to put your thumbs and index fingers to form a diamond. These are the gill arches. Now, think of each bow as a double-sided comb, with teeth protruding forward and backward. Now imagine that each tooth is lined with small flaps, which overlap like rows of inverted dominoes.
Based on this anatomy, Paig-Tran understood how manta filtration works and why it does not. As the water enters the mouth of the animal, it assumes that it flows on the gills before leaving the gills. Part of the water is diverted into the interstices between dominoes and the plankton is trapped in these spaces. But thanks to the angle of the rakers, the same input currents also move the plankton trapped, taking them into the manta's throat. Technically, this is called cross flow filtration. More simply, it is a sieve that disengages.
But this explanation collapsed when Paig-Tran's team, including master student Raj Divi, created a three-dimensional print model. When they placed it in a water tunnel loaded with small shrimp eggs, they realized that it could filter the particles smaller that the gaps between dominoes – a feat that should have been impossible.
The team discovered what is really happening by adding a dye to their aquatic tunnel, following the trajectories of the colored currents and observing the movements of the food particles in these currents. They noticed that when the water reaches the attacking edge of each domino, it forms a whirling swirl that you can see in the video below.
When food particles encounter these swirls, they accelerate. This acceleration of speed prevents them from slipping into holes enter the dominoes. Instead, they bounce back repeatedly on the topspassing from one to the other like bouncing balls on singalong lyrics. This phenomenon, which Paig-Tran calls "ricochet separation", means that the food is concentrated in the thin layer of water that remains in the mouth of the manta and is drawn into his throat. All other waters are carried by the rakers and out of his body.
Source link
