New Delhi: Sharks have ruled the oceans for over 450 million years and are important for maintaining the balance within marine ecosystems. However, these mighty guardians face unprecedented threats today, and many shark species are on the verge of extinction. In this article, let us look at some interesting facts, myths and other details about sharks and understand why urgent action is needed to protect them.
Sharks: Interesting facts
Shark: Name and meaning
Until the 16th century, sharks were known as “sea dogs” to sailors. The word “shark” likely came from the Dutch word “schurk”, meaning ‘villain, scoundrel’. The theory that it comes from the Yucatec Maya word “xook” has been disproven.
Sharks don’t have bones
Sharks, including rays, sawfish, and skates, belong to a particular category of fish called “elasmobranchs”, known for their cartilaginous skeletons. Although sharks don’t have actual bones, their cartilaginous skeletons, buoyant livers filled with low-density oils, and the deposition of calcium salts in their skeletal cartilage as they age allow for effective fossilisation. Additionally, their enamel-coated teeth are preserved in the fossil record.
Some sharks can actively pump water over their gills while resting on the sea floor (Photo credit: Alastair Pollock Photography/Moment/Getty Images)
Good eyesight
Sharks’ eyesight is truly remarkable. They excel in dimly lit areas, possess superior night vision, and even discern colours. A key factor in their exceptional vision is the tapetum, a reflective layer of tissue at the back of their eyeballs. This unique feature allows sharks to see clearly, even in low light.
Special electroreceptor organs
Sharks are equipped with small black spots near their nose, eyes and mouth. These spots, known as the ampullae of Lorenzini, are special electroreceptor organs that play a crucial role in allowing the shark to sense electromagnetic fields and temperature shifts in the ocean, enhancing their ability to navigate and hunt.
Skin feels similar to sandpaper
Shark skin feels like sandpaper because it comprises tiny teeth-like structures called placoid scales. These scales point towards the tail and reduce friction when the shark swims.
How is age counted?
Sharks can be aged by counting the rings on their vertebrae, which contain opaque and translucent bands. The band pairs are counted like tree rings to determine the shark’s age. However, as recent studies have shown, this method can only sometimes be accurate. Hence, researchers need to study each species and size class to determine how often the bands are deposited, a process called validation.
Blue sharks are blue
The blue shark is known for its striking brilliant blue colour on the upper part of its body, while its underside is usually snowy white. While mako and porbeagle sharks also have a blue hue, they are not as vibrant as the blue shark. Generally, most sharks appear in shades of brown, olive, or grey.
Are they harmful?
Sharks rarely view humans as prey. When sharks bite humans, it is usually out of curiosity, self-defence, or mistaken identity, as they may confuse a person with prey.
Some types of sharks are at risk (Photo credit: Stephen Frink/The Image Bank/Getty Images)
Not all sharks have the same teeth
Mako sharks have long, sharply pointed teeth, while a white shark can possess triangular and serrated teeth. These distinct dental structures leave characteristic marks on their prey. Interestingly, a sandbar shark can have approximately 35,000 teeth throughout its lifetime.
Size
Sharks come in a wide range of sizes. The biggest shark currently living is the whale shark, which can reach lengths of up to 40 feet and weigh as much as 4.5 tonnes. On the opposite end of the scale is the dwarf lantern shark, a tiny creature that can comfortably rest in the palm of your hand.
Reproduction
Some shark species are known to reproduce via a virgin birth, a process known as parthenogenesis. Females can fertilise themselves with material that splits off from an egg as it divides but then fuses back with the egg. Some sharks have also been known to eat their siblings in the womb, with the fastest-growing embryos feasting on the yolk sacs and embryos of their less-developed brothers and sisters.
Sharks: Myths vs Facts
Myth: All sharks are the same.
Fact: Many shark species are incredibly diverse, with different sizes, shapes, habitats, diets, and behaviour.
Myth: Sharks have walnut-sized brains.
Fact: Sharks can exhibit complex social behaviour, and some species can communicate through body language, live in groups, and even hunt in packs. Sharks and rays have some of the largest brains among all fish, with brain-to-body ratios similar to birds and mammals.
Myth: All sharks must swim constantly.
Fact: While most sharks must swim continuously to pass water over their gills and breathe, some sharks can actively pump water over their gills while resting on the sea floor.
Sharks and rays have some of the largest brains among all fish (Photo credit: Stephen Frink/The Image Bank/Getty Images)
Sharks: Why do we need to protect them?
Sharks are really important for keeping the ocean healthy. They help control the population of other sea animals and stop too much algae from growing, which can harm coral reefs. Some types of sharks are at risk because they don’t have a lot of babies and take a long time to grow up. It’s like humans – they live for a long time and don’t have many babies at once. Legal shark fishing is a job for some people, and seeing sharks is a big deal for diving tourists.
Sharks date back more than 400 million years, meaning they existed millions of years before dinosaurs walked on Earth. Do you know sharks can have 35,000 teeth throughout their lifetime? Well, let us find more interesting facts about sharks. knowledge Knowledge News, Photos and Videos on General Knowledge
