The octopus is a truly mysterious animal. Some may think they’re fairly simple, so it’s easy to assume that these jellyfish-looking creatures are just big bulging heads, known as mantles, with dangly legs. Yet this ocean-dwelling species is so much more. They’re considered to be one of the most intelligent invertebrates on the planet – octopuses were even the first creatures to be seen using tools, including hiding from possible predators using coconut shells.
There are more than 200 species of octopus found living in all of the oceans around the world. They are often nicknamed ‘monsters of the deep’ since, like their cousin the squid, they often lurk in the depths of the sea. Dropping down on their prey from above, octopus mainly feed on shrimp, lobsters and crabs, but they have also been known to feast on larger animals including sharks. Although they are not technically classed as endangered, their populations are still at risk from human activity. This includes the destruction of their habitat as well as overfishing and marine pollution, both of which reduce the octopus’ main source of food.
So let’s plunge into the deep to find out some more weird facts about the incredible octopus.
1. Octopuses have blue blood. In order to survive the cold depths of the ocean, this species has evolved to have copper-based blood rather than iron, which results in the blood being blue in colour.
2. They also have three hearts. Two of the hearts pump blood beyond the animal’s gills, whereas the third heart keeps the blood flowing for its organs. This third heart also stops beating whilst the octopus swims, which is why they prefer to crawl along the seafloor – swimming is just too exhausting!
3. Octopuses are boneless so can squeeze in and out of tight places. The only hard part of their body is their beak, which is similar to a parrot’s beak and is used for eating prey. It also contains venomous saliva; the blue-ringed octopus is believed to be one of the world’s most venomous animals.
4. The word ‘octopus’ comes from the Greek word ‘októpus’, meaning ‘eight foot’.
5. Most people call the limbs of an octopus ‘tentacles’ but that is actually incorrect – they are in fact arms. Tentacles are often much longer than arms, with suckers just at the ends. Whereas arms have suckers along the entire underneath of their appendages and are stronger and shorter.
6. A muscular tube, called the siphon, is responsible for propelling octopuses backwards by blasting water through it.
7. The oldest fossil of an octopus dates back 296 million years. The specimen, which belongs to the Pohlsepia species, is on display in Chicago’s Field Museum in the US. Although the fossil has been described as looking like a “flattened cow patty”, it contains the tell-tale octopus signs of eight arms and two eyes. There may even be an ink sank there too, but researchers aren’t certain.
8. Octopuses are famous for their ink-squirting abilities. This useful skill doesn’t just hide the animal and create enough of a distraction for them to slip away, it also harms their enemies. When the dark substance gets into a predator’s eyes, it causes a blinding irritation. The ink also affects an animal’s sense of smell and taste and is so powerful that some octopuses fail to get away quick enough and die from their own ink.
9. Another way that octopuses manage to avoid being eaten by predators, such as whales, seals and large fish, is their ability to blend into their surroundings by changing the colour and texture of their skin. They can transform their flesh into a wide range of colours including brown, grey, blue, pink and green. As well as changing to camouflage themselves, octopuses also change colour as a way of communication.
10. Female octopuses can lay up to 150,000 eggs within one week. Once hatched, the tiny octopuses spend a short period of time floating near the surface with plankton, before returning to the bottom of the sea. This may sound like a lot of baby octopuses but it is necessary. Male octopuses die a few months after having mated whilst the female octopus tends to die of starvation because they will not eat for three months.