There are more than 500 species of sharks that have been identified. They can live both in the sea and in fresh water. According to the fossil records obtained to date, sharks have been around for about 400 million years. The average life span of sharks is 20-30 years, although there are species living up to 100 years. The whale shark (Rhincodon typus), which is not predatory and feeds on plankton, is the largest shark, with a length of 17-18 meters and a weight of approximately 36 tons. The white shark is the largest predatory shark, with a length reaching 6 meters. The egg of sharks is also a record holder: the size of the largest egg, found in 1953, was 30.5 centimeters, while the size of the embryo was measured at 35 centimeters. The smallest shark observed so far is only 14 centimeters long, and it was found on the shores of Louisiana in 2010.
Sharks are categorized in three groups according to their feeding style: those that feed on 1) plankton, 2) floating creatures, and 3) creatures on the sea floor. Although sharks are known as the best hunters in the sea, one out of two of their hunts ends with success. The prey is very unlikely to escape when caught by a shark. The great white shark has about 300 sharp teeth that bite with a force predicted to be as powerful as 18,000 Newtons, whereas a human bite can be as much as 1,300 N. Sharks use a sonar system (sound waves) to locate prey. The absence of swim bladders and the fact that their skeletons are cartilaginous rather than bony allow them to move quickly and swiftly underwater. Sharks also have an acute sense of smell. Their nostrils are only for smelling, not for breathing.
The unique design of their skin is part of what makes sharks such effective predators. In fact, suits made to imitate shark skin are banned at international swimming competitions. If you touch shark skin from front to back, it has a silky texture; but if you touch it from back to front, the texture is like sandpaper.
The surface of the skin is covered with geometric shapes similar to tiny teeth – or like roof tiles. There’s almost no gap between these shapes. These tiny, hard, and smooth structures have roots tightly attached to the skin. The denticles (microscopic scales) provide a hydrodynamic advantage to sharks when swimming by reducing the friction between water and skin.
The German paleontologist, Wolf-Ernst Reif examined the denticles of 46 shark species and researched on their features that enable them with hydrodynamism. Reif showed that the grooves and canals on the denticles are what reduce the friction with water. The hundreds of thousands of denticles come together to form a common flow path, reducing the turbulence caused by friction, preventing speed loss. These denticles allow sharks to swim 12% faster.
Swimmers wearing apparel using this technology swim about 7% faster. The denticles not only reduce friction, but they also increase repelling force. It was discovered that during the Beijing Summer Olympics in 2008, 23 of the 25 world record-breaking swimmers wore apparel made from the aforementioned fabrics. Thus, the garments were banned.
The swimming pool isn’t the only place where we can see the influence of shark skin. Hospitals, perhaps unexpectedly, have also been improved by the design of shark skin. Most exposed surfaces in hospitals are germ magnets. And because of the environment, hospital germs are resistant to antibiotics and disinfectants. The use of copper and silver coatings with anti-microbial structures is quite costly.
Researchers designed a material called Sharklet. According to a study published on September 17, 2014, in the journal Antimicrobial Desistance and Infection Control, researchers found it is possible to almost permanently disinfect surfaces using special coatings inspired by shark skin.
Simulating the grooves and canals of shark skin denticles results in 94% fewer germs. Sharklet coating material outdoes its competitors in applicability not only for wares, but also for medical devices. Of course there are different coating materials made in the same way. Another material made from silica, and also based on shark skin, solved one of the biggest problems facing ships. Water algae and lice adhere to the surface of ships and accelerate corrosion. In experiments conducted in the North Sea, it was found that the vessels with the shark-skin inspired coating saw 67% fewer mussels and 85% less algae adhering to them.
The work of human beings inspired by examining the skin of the shark is wonderful, but when we think of the number of all living beings, it is like a drop in the sea. There are millions of animal and plant species waiting for scientific study and perhaps hiding great inspirations. The keys to our discoveries and inventions are revealed when studies are done. Perhaps the creatures we know as useless today will show that they are the wonders of creation in the future.