Amazing shark facts

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Science & Technology

Friday, 03 February 2012

Author / Source : Obaidur Rahman

Sharks are one of the oldest known creatures of the modern world, dating back to 450 millions years or so and some of the present kinds have been known to be around for about 100 millions of years, the very time when the dinosaurs used to roam our planet. Remarkable aquatic creatures in their own rights, with more than 350 species of its kind, (75 in the list of endangered species), sharks are a wondrous biological entity of our earthly ecosystem with stellar characteristics. Sharks, known to live up to 30-100 years and can be found in all seas all over the globe, never get cancer, pose amazing healing power to cure its own wounds and show remarkable resistance to many life-threatening diseases and this is why this fierce predator is subject to cancer research, in search of a cure for this deadly disease. Sharks do not have any bones; instead its skeleton is made up of cartilage, the stuff that shapes our ear! The skin of this creature is another interesting factor as instead of scales, like other fishes, sharks has thousands of miniature “teeth” called denticles embedded in its skin. And this skin-tooth layer acts as armour suit and provides protection for the shark and this nature of skin is so durable that in the olden times the skin was used as sandpaper and nowadays often used to make expensive shoes and drums. Sharks are also known for their keen sense of smell, not only that they can smell a drop of water in a million drops of water, 2.5 miles away ( two third of its brain is dedicated to smell), but also they have remarkable sensitivity to vibration of water which means that they can feel the movements made by other animals that are hundreds of feet away and it is because they have electroreceptor organs called Ampullae of Lorenzini, that detect the electromagnetic field generated by all living things. Sharks are also known for their distinct teeth. It has been found that each kind of shark is armed with teeth that fit its dietary lifestyle, some have knifelike, fork-like with either sharp or blunt or rounder shape sizing from large to small but it is understood that sharks have 5 to 15 rows of teeth in each jaw and their teeth are known to fall easily as easily they are replaced. It is believed that a shark can have up to 30,000 teeth in its lifetime.
The biggest carnivore shark is the Great White which grows up to 21 feet (even more) in length and weighing about 5,000 pounds and the smallest shark known to man is the Dwarf Lanternfish (6 to 7 inches), Spined Pygmy Shark (7 inches) and Pygmy Ribbontail Catshark (6 to 7 inches). Bull Sharks are often captured for display in aquariums, as this is one of the few species of shark that survives well in captivity and Sand Tiger Sharks are most active at night whereas the hammerhead shark has the best sense of smelling. Research has found that the Portuguese Shark can dive more than 1.5 miles, or 2.7 kilometers, below the surface of the ocean and females are usually larger than males and have thicker skin to withstand the bites of males wanting to mate with them. The dogfish sharks are named for their tendency to attack their prey just like a pack of wild dogs does, in group formation.
Another amazing fact about sharks is that they have to move all the time in order to stay alive, and this is because sharks must force seawater through their open mouths and over their gills (the paired respiratory organs of fishes) in order to breathe when resting, shark do that on the sea bottom where the current is strong enough to flush water over their gills. Research has found that oil in the liver is what keeps the shark from sinking as its density is lower than that of the surrounding water. Sharks do not sleep the same way us humans do, and then again we are not fishes. But it is believed that they might seem as if they are sleeping but they are really just resting! Some sharks are known swim up to 20-40 miles per hour and sharks can see almost as well behind them as they can in front.
Even though sharks are fish but most sharks give birth to their babies and few lay eggs and baby sharks are on their own (baby sharks are born with sharp teeth and the ability hunt right from the start) from the very moment of their birth except few, like the dogfish shark who are known to keep their babies up to for 18 to 24 months and like many other species, sharks learn through experience. In fact baby sharks begin their hunting and killing before they are even born by consuming their weaker siblings inside their mother’s oviduct. Sharks are one of nature’s most prolific hunters and the top one of the underwater food chain. Even though sharks are sort of fussy eaters but their hunger can be satisfied with one hearty meal and sometimes, after such meal, sharks do not eat for a while which can last for few moths straight!
There is misconception that sharks are very, very dangerous species, thanks to movies like “Jaws” but in reality sharks attack about 100 people every year and out of which 10 result in human fatality. And usually shark attack on a human usually occurs in less than 6 feet 6 inches of calm water, and within a relatively short distance from shore. On the other hand, every single year human beings kill tens of millions of sharks every year for their skin, fins, meat and liver oil. No wonder shark has been categorised as an endangered species. It’s about time mankind put an end to such indiscriminate slaughter of sharks.