Sweet relief. Summer is here, and people around the nation can start enjoying the oceanside beaches they have been dreaming about all year long.
Warm weather. Ice cream. Hot sand. Cool water. Time spent with friends and family.
It’s a relaxing, stress-free time … until someone mentions that one word: Shark.
For anyone who’s seen “Jaws,” this creature doesn’t seem like one they want to become particularly close with.
But 41 years after one of the most fear-instilling movies of all time, scientists have a much better understanding of sharks.
Some neuromasts are specialised to sense other changes in the environment. These are called
ampullae of Lorenzini. Each ampullae works independently to distinguish the difference in electric potential in the environment versus in the shark's body. Scientists think that this may allow sharks to detect prey, like muscle spasms originating from an injured fish, as well as predators, and mates. It is also thought that these ampullae may be responsible for detecting the Earth's magnetic field, helping guide sharks during migration.
Researchers are also using what they know about this system to try and create new shark repellents.
Technically, sharks can undergo what's called tonic immobility, or a natural state of paralysis. Researchers can induce this state in a shark by either flipping the animal onto its belly or rubbing its snout, depending on which species it is. Humans aren't the only ones who know how to use this trick. Scientists think large cetaceans, like whales, may use it as well to defend themselves or prey upon sharks (instead of grabbing hold of the dorsal fin, a larger marine animal would bite it). It may also be a tactic that sharks use on each other during mating to prevent injury to the female.
There are at least 440 known species of shark. Among such a diverse population, it's impossible to say for sure that all of them are colour-blind. But some research suggests that many are. All animal's eyes contain two different photo receptors, sensory cells that respond to light, known as rods and cones. Rods determine the light levels that can be recognised while cones control for colour. A study of 17 different shark species found that although the animals can see at a huge range of light levels, they can only see at one colour spectrum: Green. This is very rare in land animals, but common in other marine species such as whales, dolphins and seals.
Sharks are able to smell one drop of blood in 1,000,000 drops (26 gallons) of seawater.
Sharks' noses can detect tiny delays in how much time a smell reaches one nostril compared to the other. They use this as a directional cue and turn towards the side that received the smell first, allowing them to stay oriented.
Over 400 species of sharks have been discovered so far. The smallest of all sharks -- the Pale Catshark -- hardly looks like the monster you may have dreamt about. This little fellow scales in at a mere 8.3 inches!
On the other hand, the well-known Great White shark can reach up to 20 feet and weigh in at over 5,000 pounds.
But even the Great White pales in comparison to the Whale Shark, which reaches lengths of nearly 50 feet (about as long as a coach bus!) and weighs an astounding 47,000 pounds.
Sharks are animals with gills, meaning that they must have constant water flow to take in oxygen and survive. This seems like a problem since they usually achieve this by constantly swimming. But all animals must rest.
Some sharks have special organs called spiracles behind the eye that pump water over the gills even while they're sitting still. Species that never evolved to have this helpful feature find solace in taking short breaks from swimming while sitting face-first in the current to allow continued oxygen uptake through the gills.
Like all vertebrates, sharks have a skeleton. The interesting thing about sharks is that theirs isn't made of bone.
Unlike humans, sharks have a completely cartilagenous skeleton. This is the same stuff that makes up our ears and noses. This unique difference allows sharks to travel faster -- important for hunting -- since they can move their bodies without the rigidity of a bony vertebrate column. In the blink of a (human) eye, a shark can turn and bite a predator lurking at its tail.
Cartilage is also a lot lighter than bone, aiding in buoyancy, or the shark's ability to stay afloat. Finally, it is much more durable to injury, which is a necessity in the predator-filled world that is the open ocean.
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