Sharks’ Intestines Spiral Like a Valve Invented by Nikola Tesla

Tesla’s ingenious valve promoted a one-way flow of fluid without the need for moving parts, but, it turns out, evolution got there first

Pacific spiny dogfish shark intestine
A 3D image of the spiral-shaped intestine of a Pacific spiny dogfish shark. In life, food would move through this intestine left to right. Samantha Leigh / California State University, Dominguez Hills

New research published last week in the journal Proceedings of the Royal Society B shows that in 1920 when famed Serbian-American inventor Nikola Tesla developed a curlicue-shaped pipe that he called a “valvular conduit,” he was unknowingly mimicking the structure of shark intestines, reports Christa Leste-Lasserre for New Scientist.

“The purpose of the valve was to produce flow in one direction without the use of extra mechanical parts or extra added energy,” study author Samantha Leigh, an animal physiologist at California State University, Dominguez Hills, tells Veronique Greenwood of the New York Times. “That seems very similar to how these shark intestines are shaped.”

Video: Pacific spiny dogfish intestine

It wasn’t a mystery that sharks had corkscrewed digestive tracts, but when researchers dissected them to study, the process often damaged the organs’ delicate structure, obscuring how they functioned internally.

To get around this problem, Leigh and her co-authors removed the entire digestive tracts from 32 dead sharks (all donated or taken from museum collections) from 22 different families. As Greenwood writes in the Times, the sharks in the study have four different types of spiral intestines: “a basic spiral, a nested series of funnels pointing one way, a nested series of funnels pointing the other way, and what’s called a scroll intestine, where layered sheaths nestle within each other.”

To preserve these shark guts in a life-like arrangement, the researchers filled the organs with fluid and freeze dried them. Then, the team created 3-D models of the shark intestines using computerized tomography (CT), which takes a large number of cross-sectional X-ray images and combines them to make a digital model.

These digital 3-D models, as well as experiments in which the researchers pumped fluid through the shark intestines, revealed the spiral shape slows down the passage of food, which may help sharks extract every last calorie from their food. And, similar to Tesla’s one-way valve, the twisted architecture promotes a one-way flow through the digestive tract and potentially reduces the energy the sharks expend pushing food in the right direction with muscular contractions.

Tesla valve and a shark intestine
A Tesla valve (above) creates one-way flow without backflow or moving parts. A shark’s spiral intestine (below) has a similar structure. Samantha Leigh / California State University, Dominguez Hills

Next Leigh and her co-authors hope to use the digitized intestines to create 3–D-printed models for further tests. “My hope is to figure out what these particular morphologies are good at moving along, what they’re good at filtering out,” Leigh tells the Times.

In a statement, Leigh says these insights into the design of sharks’ digestive tracts could provide engineers with inspiration in applications, including wastewater treatment and filters designed to remove plastic pollution from water.

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