Shark intestines function like Nikola Tesla’s valve

It's time to use modern technology to look at these really amazing spiral intestines of sharks.


For centuries, scientists rely on flat sketches of sharks’ digestive systems to fully understand how shark intestines function. But, scientists now have produced 3D images of shark intestines from almost three dozen shark species. They aimed to understand how sharks eat and digest their food.

The study includes scientists from California State University, Dominguez Hills, the University of Washington, and the University of California, Irvine.

For the study, scientists used a CT scanner to create 3D images of Shark intestines, which came from specimens preserved at the Natural History Museum of Los Angeles. The images show the complexities of sharks’ spiral-shaped intestines.

CT scan image of the spiral intestine
A CT scan image of the spiral intestine of a Pacific spiny dogfish shark (Squalus suckleyi). The beginning of the intestine is on the left, and the end is on the right.Samantha Leigh/California State University, Dominguez Hills

The scans revealed some new aspects of the functions of shark intestines. Scientists found that the spiral-shaped organs slow down food movement and send it down through the gut. This process mainly depends on gravity and peristalsis, the rhythmic contraction of the gut’s smooth muscle.

The amazing fact is- this function of shark spiral-shaped intestines exactly resembles Nikola Tesla’s valve. Tesla valve, which was designed more than a century ago, allows fluid to flow in one direction, without backflow or assistance from any moving parts.

Tesla valve
A Tesla valve, shown in the diagram above, produces a one-way flow without any backflow or use of mechanical parts. A shark’s spiral intestine, shown under the valve diagram, appears to have a similar structure. Samantha Leigh/California State University, Dominguez Hills

Lead author Samantha Leigh, assistant professor at California State University, Dominguez Hills, said, “This finding could shed new light on how sharks eat and process their food. Most sharks usually go days or even weeks between eating large meals, so they rely on holding food in their system and absorbing as many nutrients as possible. The slowed movement of food through their gut caused by the spiral intestine probably allows sharks to retain their food longer, and they also use less energy processing that food.”

Co-author Adam Summers, a professor based at UW Friday Harbor Labs who has led a worldwide effort to scan the skeletons of fishes and other vertebrate animals, said“The vast majority of shark species, and the majority of their physiology, are completely unknown. Every single natural history observation, internal visualization, and anatomical investigation shows us things we could not have guessed at. We need to look harder at sharks and, in particular, we need to look harder at parts other than the jaws and the species that don’t interact with people.”

CT scan image of a dogfish shark spiral intestine
A CT scan image of a dogfish shark spiral intestine, shown from the top looking down.Samantha Leigh/California State University, Dominguez Hills

In further studies, scientists are planning to use 3D printers to create models of different shark intestines. Through this, they will get detailed insights into how materials move through the structures in real-time.

Other co-authors on the paper are Donovan German of the University of California, Irvine, and Sarah Hoffmann of Applied Biological Services.

Journal Reference:
  1. Samantha Leigh et al. Shark Spiral Intestines May Operate as Tesla Valves, Proceedings of the Royal Society B. DOI: 10.1098/rspb.2021.1359
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