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Ocean Currents

The Wonder of Shark Scales

Inspiring innovation and conservation

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This blog post was written in collaboration with Vicky Chan, who is a former Smithsonian I2F Fellow in Family Programs at the National Museum of Natural History. She hopes to continue science outreach and attend graduate school to strengthen her interests in science communication, program development and design.

What do a back scratcher, a glove and a mermaid’s tail all have in common? It may be difficult to find a common thread—but, to a group of students—the connection was clear.

Each of the three ideas could benefit from mimicking the texture of a shark’s skin. A back scratcher made rough like sandpaper, a protective glove with extra grip or a fantastical mermaid’s tail covered in dermal denticles for speed.

These ideas came from an inquisitive group of elementary school students who were learning about shark skin under the guidance of Vicky Chan. As a Smithsonian Fellow, Chan developed creative science workshops for families visiting the National Museum of Natural History. Chan is also a huge fan of sharks.

So, what about sharks’ skin inspired these students’ ideas? Let’s explore.

COPY close up denticlesTry to imagine if the skin on your body had the texture of tiny teeth. Strange, right? Your skin might not feel smooth at all, but rough like sandpaper. Unlike most other fish in the ocean, shark skin is made of dermal denticles, or “skin teeth.” Despite their slick appearance, you can see under a microscope that sharks are almost completely covered in these denticles, also known as placoid scales. The shape and positioning of these shark scales give them two evolutionary advantages.

First, thinner, ridged dermal denticles allow for drag reduction, which means some sharks can cut through water faster and easier than other fish. Second, thicker, less-ridged denticles can protect sharks from being easily scratched by hard surfaces or other animals and even make it harder for parasites to stick onto their skin. The positioning of the denticles also explain why it might feel smooth to rub a shark from head to tail (which we do NOT suggest that you try), but rough from tail to head.

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COPY mermaidIt is no surprise that sharks have inspired all sorts of product innovations, from improving fuel efficiency in cars and creating more productive windmills, to designing more streamlined swimsuits and making bacteria-resistant materials. Sharks inspire an abundance of ideas through biomimicry, an approach to innovation that emulates nature’s design. This is what inspired the imagination of Chan’s young students—a back scratcher made rough like sandpaper, a protective glove with extra grip or a fantastical mermaid’s tail covered in dermal denticles for speed.

Although many of us may never get close enough to touch a shark, Chan herself has studied shark scales intimately. When she studied Ecology and Evolutionary Biology at the University of California Santa Barbara, Chan worked closely with Erin Dillon, a marine biologist who studies the accumulation of shark scales on coral reefs to understand the best environmental conditions for sharks. At one point, Chan observed scales from 19 different species of tropical coast and reef-associated sharks.

“It was really fascinating to see the tiny scales underneath the microscope. The concept of how the form of the scale relates to the function is the coolest part of the scales to me and learning how it can correspond to the lifestyle of the shark,” says Chan.

 

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Learning about shark scales can help us better understand how to protect them. Dillon’s research has shown that as the dermal denticles of sharks fall off, they accumulate in ocean sediments over time. In this way, scales preserve the history of sharks much better than other parts of their bodies. Chan learned that by studying the composite of scales at the bottom of reefs over time, we can see a record of sharks’ distribution and abundance that can inform us of how human activity has affected sharks and the surrounding environment.

Chan hopes that the more accurately we can identifying denticles, the more we can do for shark conservation by focusing on particularly vulnerable species. And this, in turn, with the help of supporters like you, can help us make sure these marvelous creatures survive into the future. Whether it’s the hammerhead, tiger shark or nurse shark, these diverse and beautiful creatures become more fascinating as we learn more about their physiology.

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