What has eight arms, a large bulbous head and a soft body? If you guessed the octopus, you’d be correct! Not only does its appearance set it apart from other fish species in the sea, but its reputation as one of the most intelligent aquatic creatures also makes it unique. Wriggle your way through our top 10 facts about the octopus and discover what makes this creature so fascinating…
1. An octopus is an invertebrate
Their soft bodies don’t contain a backbone, which means they fit into the invertebrate category. As invertebrates, they’re closely related to other popular marine animals, including squids and cuttlefish.
In fact, octopuses don’t have any bones. Inside their bodies is a hydrostatic skeleton, giving them a fluid-filled muscular system that allows them to move. Thanks to this, they can squeeze in and out of the tiniest of places. They’ll usually always win in a game of hide-and-seek!
2. What is the plural of octopus? We’ll tell you!
There’s often a lot of confusion about how to refer to a group of these creatures. But the plural isn’t octopi, octopodes or any other variation you might think of.
The one and only correct plural for octopus is octopuses. Deriving from the Greek word ‘oktopodi’, it directly translates to ‘eight-foot’.
3. Octopuses have three hearts
Speaking of plurals, octopuses have not one but three hearts!
Two out of the three work hard to move blood through its gills to pick up oxygen (branchial hearts), whilst the third one is responsible for pumping blood through its entire body (a systemic heart).
4. Octopuses also have nine brains
The creature’s intelligence may have something to do with the fact they have nine brains. Its nervous system is made up of one central brain and a brain at the base of each arm. It’s thanks to these brains that an octopus can do something different with each arm at the same time. They can also open jars from the inside and outside, jump on land to ambush prey and use coconuts or shells to build shelters.
5. It’s reported that octopuses have been on Earth for more than 300 million years
The octopus has way outlived dinosaurs and is thought to date back a whopping 300 million years. These underwater creatures are known to have existed during the Carboniferous period, spanning from around 359 to 299 million years ago. Scientists found fossil remains which depict the aquatic creature to have eight arms, an ink sack, and two eyes, suggesting the ancestry could go hundreds of millions of years back.
6. Octopuses are cold-blooded creatures
Like iguanas, pythons, chameleons and alligators, octopuses are cold-blooded creatures. This means that their bodies don’t generate internal heat and can vary based on the temperatures in their environment. Being cold-blooded has several benefits, including the fact that they don’t need as much food to function as normal, alongside being able to survive temperature drops through the night while being nocturnal creatures.
Not only are octopuses cold-blooded, but they also have blue blood. To survive in the deep depths of the oceans, octopuses have evolved to have a copper-based bloodstream known as hemocyanin instead of the more common iron-based bloodstream.
The copper base allows an octopus to easily transport oxygen throughout its body, which is needed to ensure its three hearts and nine brains receive enough oxygen to carry on functioning.
7. The lifecycle of an octopus is short
Despite pre-dating the dinosaurs, the lifespan of an octopus is actually very short. For some species, the maximum lifespan is around five years, and for others only six months. The lifespan of a common octopus that you can see at our aquarium is around 1-2 years.
Once an octopus reaches mating maturity, it actually symbolises the end of its life.
One of the most distinctive characteristics of an octopus is that after mating and giving birth, both the male and female die. After the male octopus has given the female its hectocotylus (mating arm), it soon swims away and dies. Researchers are still unsure as to why, but some believe if this didn’t happen, octopuses would soon take over the oceans due to their rapid growth and reproduction cycle.
The female octopus can lay up to 400,000 eggs, and due to its obsessive and aggressive nature when looking after its eggs, it prioritises its motherhood duties and stops eating. When the eggs hatch, the female’s body undertakes what is called a ‘cascade of cellular suicide’. Essentially, they put so much of their effort into tending to the needs of their offspring that they eventually die from not looking after themselves.
8. Octopuses can camouflage
Sometimes nicknamed the chameleons of the sea, octopuses can camouflage themselves to hide from predators, send warning messages to other octopuses, or attract mates. Under an octopus’s skin is an element called chromatophores, which is a mix of pigment, nerves, and muscles. An octopus can manipulate these to change its external appearance within several minutes.
It’s not just changing colour, either. An octopus can actually mimic the appearance of other creatures, such as sea snakes, lionfish, and flatfish. Impressive, right?
9. Octopuses produce ink to escape predators
They might look harmless, but the octopus can pack a very hefty punch – a venomous one at that. Octopuses can create venom from bacteria living inside their bodies, and they use it to deter predators. There’s nothing to worry about, though. The majority of octopuses aren’t full of enough venom to harm humans.
Inside an octopus’s ink is a compound called tyrosinase, which can cause a blinding irritation. This is used as a defensive mechanism when an octopus feels threatened by a predator. It gives the octopus the chance to get away whilst the predator is trying to overcome the potent ink spray. The spray can be so strong that even an octopus can die if it doesn’t escape its own ink cloud in time.
10. There are over 300 species of octopus
There are over 300 different species of octopus roaming our oceans, all of which differ in size, appearance, colour and even the number of arms they have. The smallest of the octopus family is the octopus wolfi, measuring an average of less than an inch in length and living in the shallow waters of the Pacific Ocean. Meanwhile, on the other end of the scale, the largest species is the giant Pacific octopus (Enteroctopus dofleini), which can grow between 10 and 16 feet long!
Among the hundreds of different species is the most dangerous – the blue-ringed octopus (Hapalochlaena). Although they’re fairly small, their venom is mighty, and they carry enough to kill 26 adult humans within minutes! This venom and the vibrant blue rings on their bodies are used to ward off predators and keep them safe from attacks in the wild.
A unique seven-armed octopus (Haliphron atlanticus) is even known to exist, and its size is similar to that of the giant Pacific octopus.
See our common octopus at Bristol Aquarium!
Bristol Aquarium houses its very own common octopus in our specially-made octopus tank in our Ocean Floor zone. Spending much of their time in the wild hiding in crevices and around coral, this eight-armed creature is solitary and territorial. It has a brown-green appearance unless it’s camouflaging against the surroundings. The best time to spot our common octopus is at 3pm every day when it gets it’s dinner during our daily octopus talk.
Get started on planning your next visit to Bristol Aquarium right here.