Sharks are well known sea animals. You can found many movies on them; some movies are even in series in which the nature and the character of sharks are depicted. There are hundreds of species of sharks, but very few of them are those horrifying creatures which people fear. Many people only know one thing about sharks, and that is; they have sharp teeth and they are man eaters. This is not true at all. Let us see the below written lines to see what sharks actually are.
1. They are cartilaginous fish
Sharks are cartilaginous fish. They have no bones in their body. The fins on their body cannot change their shape or position while in water because they are cartilaginous structure.
2. Their species
Sharks have over four hundred species in the world. They differ in size, weight and color. The largest shark in the world is whale shark; it is also the largest fish. Its length is 59 feet. The smallest shark is called lantern shark its length is 6 to 8 inches only.
3. Their teeth
The teeth of shark have no roots like ours. They have row of teeth. Usually, their teeth last only for a week. For this reason, they have rows of teeth in their jaws. These rows could be five to fifteen in number. When one tooth fells, next in the row takes its place.
4. Their skin
Sharks do not have scales on their skin like other fish we know. They have a tough skin with dermal lenticels; they have enamel in those places as we have enamel on our teeth.
5. Lateral line system
Sharks have lateral line system inside their body that helps them navigate inside water and find prey. This is system made up of canals filled with fluid; this fluid vibrates due to pressure in water. These vibrations are transmitted to the jelly and the jelly transmits them to the nerves. Finally message reaches the brain.
6. They sleep while moving
Sharks have to move constantly when they sleep. This is to keep the water touching their gills to that they can breathe. But some species of sharks do not move because they have a small opening behind their eyes which forces water to enter their gills.
7. Reproduction
Some sharks give birth to live young while others lay eggs.
8. They are not man eaters
Sharks are considered as man eaters because their image has been projected so. There are only ten species of shark that are considered harmful for humans.
9. Life span
Whale shark lives for long; their average life time is 100 to 150 years. The small sharks live up to 20 to 30 years.
10. Threat to sharks
The greatest threat to sharks is from human beings. This is the sad part of the story because almost every animal on the verge of extinction or running down in population is threatened from humans. Every year thousands of sharks are killed in just fishing. They are also killed in the cruel practice of fining.