Octopuses normally swim by pulsing their tentacles, like the bell of a jellyfish. This is quite energy efficient but it lacks acceleration, so when an octopus needs a sudden turn of speed it switches to jet propulsion. To do this, they suck water into the mantle cavity and then squirt it at high pressure out of their siphon tube. This is the same way that they circulate water over their gills, so the octopus is really taking a deep breath and then blowing out hard. The siphon is positioned on the side of the octopus’s body but it can be steered like the engines of a Harrier jet. Sometimes they use it as a boost when walking as well.
Top facts about octopus
Octopus eye looks much like our own, with a lens and an iris but it evolved in a different way. Octopuses don’t have a blind spot where the optic nerve passes through, because the retina is positioned differently.
Poison glands – These evolved from salivary glands, and as well as paralyzing prey they also soften up the flesh, making it easier to eat.
Chromatophores – The colour-changing cells in the skin are funnel-shaped. By squeezing ink into the funnel from a bulb at the base, the octopus can control the size of the coloured dot.
Colouration – The octopus can change colour to match the sea bed or suddenly flash the bright blue rings to startle predators.
Octopus defences – All octopuses inject a paralyzing poison through their beak to subdue prey. The smaller the octopus, the more deadly the poison. The 10cm blue-ringed octopus can kill a human. Octopuses have lots of predators of their own though, and most of their adaptations are to evade capture. Colour-changing skin cells, called chromatophores, can be used for camouflage or to flash alarming colours to scare predators. Many species also have tiny muscles under the skin to change their texture to resemble spiky coral or fringed seaweed. The mimic octopus will even hold its legs and swim in such a way as to look like a flounder, sea snake or a poisonous lionfish. If that doesn’t work, the octopus can squirt a cloud of melanin dye. This provides a smoke screen and also interferes with the sense of smell that most sharks use to locate prey.
Intelligent legs – With the ability to twist in every direction, and suckers that can grip and release individually, octopus legs are much too complicated to be controlled from a central brain. Instead they operate semi-autonomously. An octopus is like a man holding a bunch of trained snakes; he issues instructions and trusts that they will be carried out, occasionally he has a look to make sure. This means that an octopus doesn’t have a very good idea of where its legs actually are at any moment and can’t work out the shape of something by feeling it, like we can.
Octopuses can taste through their suckers and can detach a leg and regenerate a new one if they need to give you the slip. One species, the Paper Nautilus, uses a leg to deliver sperm. It detaches and swims across to the female all by itself.
Where can you find an octopus?
1.Coral reef – The myriad crevices in a reef are home to lots of tasty creatures but the octopus is very good at winkling them out.
2.Sandy floor -This is more dangerous for an octopus. Some dig burrows in the sand, others use discarded bivalve shells, like a hermit crab.
3.Rocky abyss – The giant North Pacific octopus lives in the deep, freezing depths of the Pacific seabed.