What do you know about the octopus except that it makes good sashimi? Check out some fun facts to talk about with your friends next time you go to a Japanese restaurant: 

Very. 

With a complex nervous system and excellent sight, the octopus is one of the most intelligent invertebrates. It has the highest brain-to-body mass ratios of all invertebrates, even higher than some vertebrates. 

Experiments have proven that the octopus can be trained to distinguish between different colors and shades, or solve a puzzle. Captured octopus are escape artists. Wild ones can board fishing boats and open holds to eat crabs. Some octopus are even able to use tools: The veined octopus collects coconut shells and uses them to build shelters.  

Due to its super intelligence, some countries have even banned surgeries on octopus without anesthesia. 

When breeding, the male octopus uses a specially evolved arm to send a bundle of sperm into the female octopus's body, and dies. 

The female won't live long either. After becoming a mother, the female octopus takes good care of the fertilized eggs until they hatch. During this time (usually five months or even ten months in cold waters) the female does not eat. As soon as baby octopus hatches, the female dies too. 

Most octopuses have a very short life span of a few months. But if their reproductive organs are removed, they can live much longer. 

As long as the room is not smaller than its beak – the only hard part of its body. A large octopus has even been known to slip inside a beer bottle. 

But only the blue-ringed octopus is deadly to humans. 

The largest specimen of the giant pacific octopus weighs 272 kilograms with an arm span of nine meters. Records show that a giant pacific octopus can lift 16 kilograms with a single suction cup on its arm. 

Interestingly, the smallest octopus species, the Octopus wolfi, is only around 2.5 centimeters and weighs less than one gram. 

But it does not benefit much from this. When the octopus swims, all three hearts are inactive. This makes it tired very quickly. So the octopus prefers crawling or "walking" rather than swimming. Also, when the octopus uses "jetting" skill to escape danger, the hearts stop beating for a moment. 

One other fun fact is, the creature's blood is blue. 

The thin skin of the octopus can absorb extra oxygen. This is why it can live for quite a while out of water. 

How does the octopus excel at camouflage? We all know that it can change color to become "invisible." It does not have to see what color is around with its eyes, but senses it with its skin. The skin can sense different wavelengths of light and identify its color. 

The octopus also uses color-changing to communicate with each other, or use this method to mimic other predators. 

The sticky arms never get tangled or stuck to each other because the "sensors" on the arms can recognize its own skin (the sensors also taste whatever it touches, to avoid taking its own parts as food). But the octopus cannot feel what its arms are doing, unless it sees the arms with its own eyes. 

Each arm of the octopus has a "mind" of its own. Because about two-thirds of the octopus's neurons reside in its arms, not its head, meaning they can react to stimuli and function at a fairly high level on their own, even when severed from the body. 

The octopus brings food back to the den. Sometimes it catches more than it can eat. So, if a lucky fish or crab survives capture, it may be brought back, share the den (even the "garden" built by the octopus with shells and other things), and live there as a neighbor. 

(All images via VCG)

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