Athletic by Nature (3): Sharks Are Fast and Furious

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Meeting a shark could be the worst nightmare for swimmers, snorkelers, or wave surfers; we all have this image of notorious white sharks rapidly and fiercely attacking with jaws lined with razor-sharp teeth. However, there is much more to these masterful and highly maneuverable swimmers.

Sharks (Pleurotremata) can hardly be outswam, which is no wonder given their more than 400-million-year evolutionary history in the ocean. American Olympic swimmer Michael Phelps—the most decorated Olympian of all time, with a total of 28 medals—challenged a shark. The race, held in July 2017, was organized as part of Discovery Channel’s Shark Week. In fact, Phelps competed with a computer simulation of a great white shark whose swimming speed was calculated using real data. Phelps, the holder of seven world records, finished the 100 m course in 38 seconds, two seconds slower than the shark.

Sharks’ swimming prowess is attributed to very specialized tools; namely, their tails, fins, and skin. The main function of a fish’s tail is to provide thrust and drive the animal forward through the water; as it moves, the tail creates one jet of water that travels backwards and propels the fish forward. Sharks, in contrast, can stiffen and manipulate the shape of the tail swing, creating two jets of water and generating double thrust. As for the fins, according to Frank Fish, a biomechanist at West Chester University in Pennsylvania, sharks can use their fin muscles to modify the shape, and possibly the texture, of the fin to modify the water flow.

Last but not least, sharks’ bodies are covered structures known as dermal denticles, which make their skin texture as rough as high grain sandpaper. These denticles acquired their name because they are structurally similar to vertebrate teeth and likely have the same evolutionary origin. In most shark species, the points of the crown are directed backward, creating a smooth feeling when touched from head to tail and a rough feeling when touched the other way round. As these denticles move on the flexing skin, they create a vortex that sucks the shark forward and increase thrust.

Several studies were conducted on the shark’s swimming skills, which have inspired different technological applications, from faster swimsuits to airplanes. For example, a study led by George Lauder, a biomechanist at the Museum of Comparative Zoology at Harvard University, studied the shark’s skin structure and used a 3D-printer to build their own artificial version. The study found that the shark’s skin structure could increase swimming speed by 6.6% and reduce the energy expended by 5.9%.

Again, and again, Mother Nature surprises us; this time, with its gifted champions. This brief account (read "Athletic by Nature (1 and 2)") is only an invitation for eager minds to know how different amazing creatures work and to speculate “the work of Allah, who perfected all things”—Surat An-Naml (verse 88). 

References

animals.howstuffworks.com

bbc.com

cheetah.org

insidescience.org

livescience.com

mostlyopenocean.blogspot.com

news.nationalgeographic.com

popularmechanics.com

sciencemag.org


The article was first published in print in SCIplanet, Summer 2018.


Banner image: vox.com

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