A shark’s interior is filled with curiosity, starting with rows of hard-working teeth that can be replaced throughout its life. But further down the digestive tract—in fact, just before the shark is finished—is another strange structure: the spiral gut, an intricate ladder made of shark flesh.
Scientists have speculated that sharks have very complexly shaped intestines to slow digestion, and they take every last calorie from their prey. There may even be a reason why sharks go a long way between meals.
But on Wednesday, Proceedings of the Royal Society B, researchers have published one of the most detailed views ever of these spiral guts by turning a CT scanner that reveals the complex internal geographies of more than 20 shark species. After filling the intestines with fluid, they also made a discovery: Some of them function like natural versions of a valve made by Nikola Tesla. patented in 1920pulls the liquid in one direction without moving parts.
Researchers who study sharks’ spiral intestines often refer to an 1885 anatomical drawing, said Samantha Leigh, an assistant professor at California State University in Dominguez Hills. Or, for a closer look, they can examine the intestines themselves, disrupting the structural integrity of the organ. To see the structures as a whole, he and his colleagues carefully removed the guts of multiple shark species and imaged them on a CT scanner.
Sharks’ spiral intestines come in four varieties – a basic spiral, a nested series of funnels pointing in one direction, a nested series of funnels pointing the other way, and a scrolling gut in which layered sheaths are interwoven. Convolutions and folds of structures are clearly revealed on CT scans.
It didn’t seem to matter what a shark ate when it came to the shape of its guts – bonethead sharks that eat both plants and other animalshad a scroll gut like a carnivore hammer heads.
Next, the researchers attached some spiral guts to tubes and watched as a mixture of water and glycerol flowed through them. Indeed, they found that fluid moves more slowly in the spiral rather than in a straight section of the shark’s gut, supporting the idea that spiral guts help sharks prolong their digestion times.
However, they also found that the funnel guts have a preferred direction for flow. Fluid entering from one end flows much more slowly than fluid entering the other, implying that in the animal the gut works like a one-way street. In mammals, muscle contractions produce this effect. But in sharks, the structure of the gut can help.
In fact, the shape of the funnel gut reminds the rings of the Tesla valve, a kind of pipe patented by the Serbian-American inventor.
Dr. “The purpose of the valve was to produce flow in one direction without using any extra mechanical parts or extra additional energy,” Leigh said. “This is very similar to how shark guts are shaped.”
Structures sharpened by ages of evolution can inspire engineers — for example the manta ray’s exceptionally unclogging filters, It can provide a way to sift plastic pollution before it reaches waterways. Also examining the effects of microplastic pollution on fish, Dr. In the case of shark intestines, more information about how the intestines work could also inform the filters, Leigh said.
Dr. “My hope is to find out what these particular morphologies are good at moving forward, what they are good at filtering out,” Leigh said. Perhaps somewhere along the line, shark guts could inspire tools to help passively remove plastics from water, simply because of the way they’re made.
