They are among the most timid and mysterious sea creatures, but also among the most fascinating: the octopuses and their tentacles have inspired legends, fairy tales, mythological monsters and cartoons.

You may have observed them closely in an aquarium or during a dive last summer. But are you sure you know them well? Here are 10 characteristics of these cephalopods that could leave you dumbfounded.

An invertebrate with super powers GO TO GALLERY (N photos)

1- They are incredibly primitive creatures. The oldest known octopus fossil, a specimen of the genus Pohlsepia preserved at the Chicago Field Museum, is 296 million years old. He lived and swam in the Carboniferous period and, while the first reptiles before the dinosaurs spread on Earth, this aquatic creature had already developed a form similar to the one we still see today.
2- They have three hearts. Two pump venous blood into the gills and one is responsible for circulation in the rest of the organs. When the octopuses swim, this last heart stops beating: this is why the tentaculated mollusk prefers to crawl on the bottom instead of swimming, an activity that leaves it exhausted.
3- They have blue blood. The blood of the octopus contains enocianina, a protein in which copper is present, capable of carrying oxygen throughout the body: in contact with air, the fluid therefore becomes blue and not red (as happens in our blood, rich of iron).
4- Aristotle believed them stupid. In the History of Animals, written in 350 BC, the Greek philosopher described the octopus as a "foolish animal, which approaches the hand of man when it is lowered into the water", while recognizing "frugal and ordered eating habits": "after having eaten everything there is to eat, discard the shells of crabs and shells, and the bones of small fish ". Today we know that these cephalopods, besides being particularly neat, are also very intelligent: they are able to orient themselves in a labyrinth, solve small tasks (such as opening containers with a cap), using makeshift tools to hide from predators.
5- Their tentacles have autonomous "minds". Two thirds of the octopus neurons reside in their tentacles and not in the head. It may therefore happen that a tentacle solves a small task such as opening the shell of a shell while its owner is engaged in other matters, such as the exploration of a ravine in the reef. The tentacles can continue to react to stimuli even when they are separated from the rest of the body (the octopus can also voluntarily lose them if they have ended up in the clutches of a predator, in order to escape).
6- They are incredibly cunning in camouflage. Unlike other marine animals with mimetic abilities, octopuses do not try to take on the colors of the entire habitat that surrounds them (sand, algae, corals) but choose a specific object (for example a shell) and pose for look like him. Even the consistency of their skin can vary for mimetic purposes: for example an octopus that wants to look like an alga can use the muscles to lift many small papillae from the skin and mimic the appearance of the ripples of a marine vegetable.
7- The ink emitted by the octopuses does not have the sole purpose of obscuring it (allowing it to escape); it is also capable of physically damaging the enemy. It contains an enzyme called tyrosinase which, when sprayed in the eyes of the aggressor, causes irritation and visual difficulties. According to marine biologists, the substance could also inhibit the smell and taste of predators, making it more difficult to detect the octopus.
8- Some octopuses dress up as coconuts. Several cephalopods in Indonesian waters were filmed as they laboriously transported the two halves of the fruit shell onto the sand, and then assembled them in the original form, one on top of the other, and hid in it, exploiting the ability to slip into the joints.
9- After mating, the party is over. Both partners die, although at different times. After fertilizing the female's eggs, the males wander here and there for a few months until they perish. Females, on the other hand, are waiting for the 100-400 thousand eggs laid to hatch, even stopping eating to guard the precious cargo. After hatching, the cells of the mother's body undergo programmed suicide, which starts from the optical glands and involves, gradually, tissues and internal organs.
10- Most of the octopus we consume comes from northern and western Africa. According to the United Nations Food and Agriculture Organization, every year, 270, 000 tons of octopus are important globally. Due to the high popularity octopus reserves are thinning: in Japan, for example, the octopus caught halved between 1960 and 1980. A similar depletion of fish stocks is taking place also in African waters and octopus fishing it has progressively moved from Morocco to Mauritania, to Senegal.
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