Sharks

Ah.. two days have passed and I haven't written anything yet~

Anyway I was busy with life and...ah... just now I skipped Dr Chin's class wtf I didn't want to because I was so attentive today and she praised me cuz I was the only one doing the assignment (she sortta like randomly ask the whole class to do it but they didn't seem to get it and I was the only one doing it and wuahahaha praise went to the deserved one - this is my blog~ kill yourself if u find it offensive =P) but too bad I had to skip or else I could never make it to Science Fac Convo at 5pm wth remorse is creeping up on me....

sorry that was a moment of SS-ness.

This entry contains awful image la... viewer's descretion ah... consider yourself =P

Superorder Selachimorpha

Sharks can be found throughout the world...Should we skip the technical?? Ah nvm~~ Do you know that sharks are older than dinosaurs? The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs. Then baby Dino came, and then went extinct but sharkiess survived the ordeal, and lived on to this day.



The Megalodon is an extinct shark that existed around 25-1.5 million years ago. A fossil shows that this animal could be the largest shark ever lived, reaching up to 20.3 meters in length, and the worst thing is that it looks like a Great White Shark...


A Megalodon tooth

All of us know at least one species of shark; the Great White Shark.



This giant can grow up to 6 meters in length, and weighs at least 2000 kilograms. It reaches maturity at around 15 years of age and can have a life span of over 30 years.
This is the star of the movie Jaws and since then people have been killing this animal for fun, and for the lucrative shark fin market.



Despite its ferocious look, the Great White is a shy animal and they often shy away from boats and human.



The largest shark, the Whale Shark, which is also the largest living fish in the world (approximately 12.6 meters), is a gentle giant that survives on tiny plankton and basically they are harmless to human.



Sharks are really special... One of the most interesting fact is that stingrays are related to sharks.


A frilled shark, considered to be "living fossil"


A Manta Ray

Stingrays and sharks belong to a group of fishes called the elasmobranchs. It is easy to spot this type of fish, all you have to do is to observe the shape of their tail. Sharks have large upper lobe which delivers maximum power for slow cruising or sudden bursts of speed, and if you observe clearly, all sharks have the same tail shape.



Also, when talking about sharks in freshwater, we must talk about Bull Shark. Bull Shark is also known for its aggressiveness and often unpredictable behavior. Most shark attacks are committed by Bull Shark and not the Great White.



The bull shark is the best known of 43 species of elasmobranch in ten genera and four families to have been reported in fresh water.



Elasmobranchs' ability to enter fresh water is limited because their blood is normally at least as salty as seawater, but bull sharks living in fresh water reduce the concentration of salty solutes by up to 50%. Even so, bull sharks living in fresh water need to produce twenty times as much urine as those in salt water. So, never think that swimming in river is safe cuz there is no shark.... a 3.4 meter Bull Shark, though not as huge as a Great White, could inflict serious wound and possibly death.

right right, what else I wanna say... AH hah~!

Some sharks lay eggs, and some give birth to pups.


Shark's egg

The mating process of sharks has never been captured on film until the Nurse Shark, a type of shark harmless to human got its porno captured by some silly human interested to watch shark porn and it got aired in a DOCUMENTARY called the DISCOVERY CHANNEL!!! and I watched it.... =.=


Nurse Shark mating

When mating, male sharks would bite on the female's pectoral fin and try to turn her to penetrate her from the side.... and so researchers find it easy to spot a sexually matured female; by looking whether it has got bite marks on its pectoral fins.

When a shark is turned upside down, it goes into a paralysed mode called the tonic immobility.


A tonic-immobilized Lemon Shark

This is caused by large amounts of serotonin being released into the shark's brain in order to calm it through this unusual experience, but the excess amounts act like an incredibly strong anaesthetic. Upon turning back over the shark regains its senses rapidly and continues as normal.



This is very important for shark researchers because handling shark has never been easier =) but turning it for too long will cause it to suffocate because sharks need constant influx of seawater so that the seawater would pass through its gill and thus it could breathe...

And as we all know, sharks are very sensitive to blood. They could sense blood from up to a quarter of a mile away.

Apart from that, sharks have an organ called the Ampullae of Lorenzini. The ampullae pores are plainly visible as dark spots in the skin.



They provide sharks with a sixth sense capable of detecting electro-magnetic fields as well as temperature gradients. There are other types of animal with this organ, but sharks may be more sensitive to electric fields than any other animal, with a threshold of sensitivity as low as 5 nV/cm. That is 5/1,000,000,000 of a volt measured in a centimeter-long ampulla.



Since all living creatures produce an electrical field by muscle contractions, it is easy to imagine that a shark may pick up weak electrical stimuli from the muscle contractions of animals, particularly prey.



Also, some sharks have eyelids, which function as a protective layer when the prey struggles..it's not actually eyelids la.. sortta like a membrane like tat~~

Shark Attack



There are roughly 10 deadly shark attacks reported worldwide annually.. It's not a big number though(highways and even railways claim more lives than sharks). Falling coconuts kill 150 people worldwide each year, 15 times the number of fatalities attributable to sharks.



Note that the number of attack is not equal to the number of casualty.

So, are we frightening ourselves for no reason?

Most shark attacks are committed by the Bull Shark, due to their notorious inconsistant behavior and aggressiveness.



There are reports of Great White attack but most of the time the shark didn't attack for food. They are just satisfying their intuition... by investigating the flapping of water on the surface(surfers swim out to the ocean to ride the wave, and that triggers the shark below), by using their bloody mouth of course(they have no hands like us... =.=) by gentle bite to see whether that something is edible...
and too often, a gentle bite from a 6 meter giant is too deadly for any human.. and the bite would produce blood, and the rest you should know...


A Great White jumping out of the sea, combining speed and brute force to kill its prey

Secondly, a surfer swimming on a surfing board looks like a seal from below.. Thus the shark would mistaken the surfer for its favourite prey, the seal.. Come on people.. you blame an animal that has no knowledge about optical illusion for killing someone, why not you blame yourself for emulating its favourite prey?

Extinction



The number is dropping fast. We kill 100 million sharks annually for shark fin soup. Like I mentioned in previous entry, every second spent typing here and there are 3 sharks getting killed by fishermen.


Finned sharks - unable to swim without their mutilated fins, the sharks, normally still alive, struggle to breathe and finally die from suffocation



Shark fin can easily be replaced by other material, we can stop the killing of shark when we stop consuming shark fin soup. Shark is the top predator in the ocean. Losing the shark means losing the whole ecosystem.


A man finning a dead Hammerhead

Moreover, when compared to most bony fish, sharks reproduce and grow relatively slowly. Sharks have relatively few (zero to around 100) offspring each year, and the mother invests much energy in each to increase the chance that it will survive. Some female sharks put so much energy into a litter that they must take two years to recover their strength before breeding again.



Although young sharks are born relatively large and able to take care of themselves, they grow slowly, sometimes only a few centimeters a year. It may take 15-20 years for an individual to reach sexual maturity. In fact some adult sharks also devour baby sharks, cannibalism is common among fish. Such low reproductive rates and slow growth combine to make sharks highly vulnerable to overfishing.





Sharks have walked thus far in the evolution cycle, only to be ruthlessly eliminated by a younger species. We can do something to stop all this. But are you ready to take that step forward?



Malcolm

info:
http://www.unisci.com/stories/20022/0523024.htm
http://science.jrank.org/pages/6118/Sharks-Reproduction-growth.html