8th October: World Octopus Day

World Octopus Day - here are ten things you may not know about octopuses (and yes, that is the plural, not, as many believe, octopi).

1. It's widely believed that octopuses have eight tentacles. In actual fact, they don't have any - the correct biological term for the eight limbs of an octopus is arms.
2. Each arm can operate independently from the brain, because most of an octopus's neurones are in the arms. If an arm gets cut off, it will continue without the body for several hours, even grabbing food and trying to put it in the mouth which is no longer there. Scientists have even found that the arms of a given octopus can have different "personalities" - some are bolder than others and will go after food in an unfamiliar place, while others will hesitate.
3. On the arms are dozens of suckers. The suckers are pretty amazing too as they have chemoreceptors, so the octopus can taste or smell with them. Each sucker can operate independently as well, pinching in a similar way to a human's finger and thumb.
4. There are about 300 species of octopus. They are all venomous, but only one is actually deadly. This one is the blue-ringed octopus, especially deadly since it is only 5-8 inches in size, yet has enough venom to kill 26 people. Not only that, but if a person is bitten by one, they won't even realise, because the bites are painless, until paralysis sets in. What's more, there's no antidote.
5. Octopuses have good eyeSight, even though many species are colour blind. The pupils of their eyes always stay aligned with the horizon, no matter which way up the animal is. They can see with their skin as well as their eyes, which may help explain why they can camouflage themselves so quickly. They can not only blend in with their surroundings but can disguise themselves as other things, such as dangerous sea animals like sea snakes and lionfish. There is even a species living in Indonesia which disguises itself as a coconut rolling with the current. At least, that is science's best guess so far as to what it is doing.
6. Octopuses have three Hearts, two of which are situated near the gills, which pump oxygenated Blood to the main heart. Because octopus blood is based on Copper compounds and not iron ones like ours, their blood is Blue.
7. A male Octopus's sex organs are on one of its arms. The male has a groove and a grasping tip called a ligula, which in some species inflates with blood like a mammal penis. The female has a groove on its mantle or head where the sperm is deposited. Once this is done the ligula breaks off. While octopuses can regenerate limbs, the male cannot grow a new sex arm, and it will die within months of mating. Females fare little better - they usually die within a few months of their eggs hatching. One species incubates her eggs for over four years, though (the longest brood of any animal). The reason is that when an octopuses sex glands mature, the hormones they produce deactivate the digestive glands and the creature starves. One final fact about octopus sex - there is a species, the Blanket octopus, in which the female is 40,000 times bigger than the male - the largest gender size discrepancy in the animal kingdom.
8. Octopuses are known for their intelligence. They have been taught to recognise shapes and patterns, solve mazes and can even open child-proof pill bottles (meaning they are more intelligent than the average toddler). Relative to body weight, they have larger brains than any animals except birds and mammals. In the wild, they use tools - such as coconut shells to make shelters. In captivity, they get bored easily, and have been observed playing - throwing objects into currents in the aquarium and then catching them. There are anecdotal accounts of exceedingly intelligent behaviour, such as one in a New Zealand aquarium, which got out of its tank, crawled across the floor and into a pipe leading to the ocean; and Otto, in Germany, who disliked a bright light which shone into his tank - so he'd climb up to the rim of the tank and spray water on the light, shorting it out. For all that, though, they are not good at telling the sex of another octopus and will try to copulate with another placed in the tank with it, regardless of gender.
9. This may be because they are generally solitary creatures - although if they are forced to co-exist in captivity, they have been observed to communicate and establish a pecking order. This tendency, along with their intelligence, has led to the UK giving them the same legal status as vertebrates in animal cruelty legislation.
10. Probably the most famous octopus in the world was Paul, who was hatched in Weymouth, England but moved to Germany. His keepers noticed his particular intelligence early in his life - he showed curiosity about the visitors who peered into his tank. Paul's claim to fame was that, during the 2010 FIFA World Cup, he would correctly predict whether Germany would win or lose each of their matches, by selecting a container of food with either the German flag, or the flag of the opposing team. The box Paul opened first was predicted as the winner. Scientists say it is entirely possible Paul's guesses were pure luck, and he was simply the luckiest of several octopuses which were attempting the same thing. Paul belonged to a colourblind species, but octopuses can see contrasts, and studies have found them to be attracted to horizontal shapes in particular. Paul even received death threats from fans of the teams whose flags he didn't choose.

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