And Some Compelling Facts Revealed

When we asked Robert E. Hueter, Ph.D., Director of Mote Marine Laboratory's Center for Shark Research for some interesting shark info, he pointed us to these 7 myths and related facts from the center's website. As you'll see, there's a lot more to these animals than meets the eye.

For further details and addtional reference material, please visit the Mote Center for Shark Research online, or better yet, in person whenever you're anywhere in or near Sarasota, Florida.

MYTH #1:

A Shark is a Shark is a Shark ... Misconstrued!
There is no "typical" shark. The more than 350 species of sharks all differ in habitat, lifestyle, and body form.

Shark Species Facts:

Four general body forms have been described for sharks, but there is wide variability within body forms.

There is a large amount of variation in the shape and position of paired and unpaired fins in sharks.

Sharks come in different colors, from cream to brown to dark gray, and many shades in between.

Sharks have many different types of teeth, including cusped teeth, triangular teeth, hook-like teeth, and more that are used for seizing, tearing, cutting, grinding, and crushing.

Sharks come in all different sizes -- from the the tiny dwarf lantern sharks that usually don't grow more than 12 inches, to the gigantic whale sharks, the largest fish in the sea, which can grow to over 45 feet in length.

MYTH #2:

Sharks Have Poor Vision ... Erroneous!
Sharks' eyes, which are equipped to distinguish colors, employ a lens up to seven times as powerful as a human's.

Shark Sight Facts:

Sharks have a nearly 360-degree visual field.

Some sharks have a third eyelid, called the nicitating membrane, which protects the exposed portion of the eye during feeding or object contact.

The great white shark does not have a nicitating membrane, and instead rolls the eye back into its orbit to protect it during feeding.

Most sharks have a reflective layer in the back of the eye called a tapetum lucidum which boosts the sensitivity of the eye in dim light.

A juvenile lemon shark has a lens with 7 times the optical power of a human lens.

Humans focus by changing the shape of the lens; sharks focus by changing the position of the lens by moving it toward or away from the retina.


All sharks have to swim constantly ... Misconceived!
While many sharks have to keep moving in order to breathe, there are some sharks, including nurse sharks, that can respire by pumping water over their gills by opening and closing their mouths while at rest on the bottom.

Shark Swimming Facts:

The ability to pump water over gills (buccal pumping) varies between shark species.

Less active sharks have an increased ability for buccal pumping.

More active pelagic sharks use ram ventilation, meaning they ventilate the gills by holding the mouth open while swimming.

Some sharks are obligate ram ventilators, meaning they have to keep constant forward motion in order to continue respiration.

MYTH #4:

Sharks Have Peanut-Sized Brains and are Incapable of Learning ... Fallacious!

Sharks' relatively large and complex brains are comparable in size to those of supposedly more advanced animals like mammals and birds.

Another Shark Brain Fact:

Sharks also can be trained.

MYTH #5:

Sharks are not discriminating eaters and scavenge the sea ... Wrong!
Most sharks prefer to eat certain types of invertebrates, fish or other animals. Some sharks eat mainly fish. Others eat other sharks or marine mammals. Some sharks are even plankton-eaters.

Additional Shark Feeding Facts:

Some sharks like to eat other sharks.

Birds may be a large part of the tiger and great white sharks' diets.

Diets within a species of shark often vary depending on the shark's sex, age, size, location and the season.

Sharks have a spiral or scroll valve intestine, which increases the surface area for digestion and absorption of food and conserves space in the body cavity.

The cookie-cutter shark is so named because of its unique jaw and tooth structure that allows it to remove plugs of flesh from large vertebrates.

MYTH #6:

Sharks are not Found in Freshwater ... Forget it!
A specialized osmoregulatory system enables the bull shark to cope with dramatic changes in salinity -- from the freshwaters of some rivers to the highly saline waters of the ocean.

Shark Osmoregulation Facts:

Sharks use high concentrations of body urea to help osmoregulate.

Sharks living in salt water must balance the influx of NaCl (salt) into the body by excretory mechanisms in the rectal gland, kidney and gills.

Sharks living in dilute salinity or freshwater conditions must balance the influx of water into the body by increasing urinary water excretion and increasing salt uptake through the gills.

90% of the secretion of body acids/bases into the water in order to balance internal pH is done by the gills.

MYTH #7:

Whale sharks, the largest species of shark, are voracious predators ... Incorrect!
Whale sharks, which are the largest fish that have ever lived, are plankton feeders like the great whales, thus the name.

More Whale Shark Facts:

Whale sharks can grow to be more than 45 feet long!

Whale sharks can be found in tropical and warm-temperate oceans.

Whale sharks do have teeth--in fact, they have more than 300 rows of them in either jaw, but they are only 1/12-of-an-inch long.

A 36-foot female whale shark harpooned off of Taiwan was found to contain 300 embryos, ranging in size from 16-25 inches in length.