The Perfect Predator: Sharks’ Amazing Biological Traits

By AT&T Digital Media Productions editorial team

Great-white-shark

Sharks have ruled the ocean for hundreds of millions of years. They range from Arctic seas to tropical waters, from shallow reefs to the deep abyss. Thanks to their unique evolutionary advantages, they’re fearless, fearsome, and practically untouchable—by other animals, anyway. Here are some of the biological features that keep these apex predators on top.

 

JAWS OF DEATH

A shark’s jaws are its most important tool—and weapon. Humans detach our lower jaws to open wide or take a big bite, but sharks detach their upper jaws, too. This basic mechanism is refined across species to produce specialized methods of feeding and attack.

Bottom-feeders like nurse and carpet sharks rely on suction, pulling prey into their small, puckered mouths. Dogfish use tight rows of teeth to slice horizontally and cut up prey they can’t swallow whole. And the great white shark gouges out huge chunks with a bite that delivers 1.8 tons of pressure.

Some sharks don’t use their jaws for biting, crushing, or tearing. The whale shark, basking shark, and megamouth shark are all filter feeders. They use their giant mouths to suck in and strain tons of tiny food out of the water, mostly plankton and small invertebrates.

 

FRESH CUTS

Sharks grow and replace teeth continually, so their bite stays razor-sharp. As teeth wear down or break off, brand-new replacement teeth move forward in rows. Imagine a slow-moving conveyor belt, constantly cycling through teeth.

Some sharks can replace a set of teeth in a mere nine days! It generally takes a few weeks for a new row of teeth to come in, and the process slows down as a shark gets older.

 

BLOOD HOUNDS

Sharks can sense potential prey from great distances, a necessary feat given the vastness of their ocean habitat. Though it’s often said that sharks can smell blood from a mile away, it’s really more like a quarter mile. They accomplish this not by “smelling” per se, but by reacting to miniscule quantities of dissolved chemicals (i.e. blood) in the surrounding water. The shark then turns into the prevailing ocean current to track down the source.

Sharks can also detect minute vibrations in the water. An injured fish flops around in distress and creates a vibration called a “yummy hum.” To a shark, it’s a dinner bell.

 

IRON STOMACH

A shark’s stomach is as powerful as its jaws. Because they swallow their food whole or in big chunks (those teeth aren’t for chewing), the stomach has to do all the work. A shark’s stomach contains very strong acids that turn solid food into near-liquid.

And if they can’t digest it? Some sharks turn their stomachs inside out to get rid of unwanted food. They eject their stomachs through their mouths, then retract and return them to normal—no big deal.

 

TAKING IT EASY

A shark’s ocean habitat is vast, cold, and empty. Opportunities to nab prey can be few and far between. Sometimes, sharks must travel great distances to find food. In order to stay alive, they have to conserve as much energy as possible between meals. Sharks are cold-blooded, meaning their body temperature is about the same as that of their environment. Their metabolisms are slow enough that they can go for weeks without eating.

A shark’s torpedo body shape, powered by its muscular tail, allows it to drift and glide through the water with minimal effort. In fact, they’re so perfectly suited for ocean cruising that the U.S. military has designed submarines based on shark bodies.

The Greenland shark, native to frigid waters of the North Atlantic, might be the lowest-energy of all. In its deep, cold habitat, it swims slowly, grows slowly, and eats infrequently. This laid-back lifestyle pays off: Greenland sharks can live for at least 200 years, with the longest living one recorded at 400 years.

 

COAT OF ARMOR

Shark skin is covered in specialized scales called denticles. Compared to fish scales, a shark’s denticles are tiny, with jagged, toothlike edges that all point in the same direction (if you rub a shark’s skin against the grain, it feels like sandpaper). Denticles reduce friction and drag, allowing sharks to glide efficiently—and silently—through the water.

Denticles also make a shark’s hide extremely tough. They interlock tightly and are as hard as granite. This rough, hard skin is as good as a coat of armor, protecting sharks from other would-be predators. A shark’s impenetrable skin also resists bacterial infections: even microbes can’t get through.

 

NO BONES ABOUT THEM

Well, sort of. Shark skeletons are made of cartilage, like your ears and the end of your nose. Cartilage is light and flexible compared to bone, allowing sharks to float, glide, and swim with minimal energy expenditure. Unlike other fish, sharks don’t need a swim bladder to maintain the correct depth without sinking.

Moreover, a shark’s muscles are attached to its super-strong skin, not its lightweight skeleton. This allows it to move faster and, again, use less energy.

HEALTHY AS A SHARK

Sharks basically have Cadillac health plans. They heal incredibly fast. Wounds and scars are replaced by new skin quickly, allowing them to bounce back from injuries. They also resist infection: shark immune systems contain a unique antiviral agent, called squalamine, that fights off viruses before they develop.

Sharks also get cancer significantly less than other animals (yes, animals get cancer). Shark cartilage contains a unique compound that specifically inhibits tumor growth. Sharks’ unique ability to resist and destroy tumors may prove critical to cancer researchers in the future.

To see these perfect predators in action, watch Shark Week starting Sunday July 22 on Discovery.

 

Sources:
elasmo-research.org/education/topics/p_feeding_div.htm
elasmo-research.org/education/white_shark/teeth.htm
elasmo-research.org/education/topics/s_nose.htm
academia.edu/26926379/Rapid_voluntary_stomach_eversion_in_a_free-living_shark
elasmo-research.org/education/white_shark/digestion.htm
http://sharkopedia.discovery.com/types-of-sharks/greenland-shark
elasmo-research.org/education/ecology/polar-greenland.htm
elasmo-research.org/education/white_shark/scales.htm
elasmo-research.org/education/topics/p_cartilage.htm
elasmo-research.org/education/topics/p_wound.htm
wonglab.seas.ucla.edu/research/immunity-and-antimicrobials/shark-immune-system/