The Octopus with nine brains…

The Octopus with nine brains…

I am involved in the creation of a Wildlife Film School, which exposes me to a number of really interesting individuals. One of my meetings last week was with Pippa Ehrlich of “My Octopus Teacher” fame. This incredible documentary won an Academy Award for Best Documentary in 2021, as well as many other awards to boot. It is currently still showing on Netflix – may I suggest you support local and give it a watch? It truly is a phenomenal documentary. But, to the point, it got me thinking about how little many people know about this species… hence today’s column!

Let’s begin by differentiating between an octopus and a squid (or ‘calamari’), as these two words seem to be used interchangeably on a regular basis – particularly with regard to menus! The above image is of squid, whilst the remainder of images in this column are of octopuses. Octopuses have round bodies and eight sucker-covered limbs, whilst squids have a more triangular shape and 10 limbs – eight arms and two tentacles. Both squids and octopuses are cephalopods, invertebrates and mollusks. Squids travel continuously (some move in schools), while octopuses are more solitary, often living in dens. There are other differences, but I think these are enough to establish that they are, in fact, two very separate creatures.

An octopus has one central brain (located between the eyes), which is able to ‘delegate’ tasks to each of the mini brains located in the tentacles – thereby allowing itself to focus on more pertinent and complex tasks. So, the octopus actually has nine brains! An octopus’s brain-to-body ratio is the largest of any invertebrate. It’s also larger than many vertebrates. Octopuses have about as many neurons as a dog. The common octopus (Octopus vulgaris), for example, has around 500 million. About two thirds are located in its arms. The rest are in the doughnut-shaped brain which is located in the octopus’s head.

But how clever is an octopus? Well, it would seem that they are incredibly intelligent. There’s the story about a lab where all the fish were going missing from their tank. The staff set up a video camera and it turned out that one of the octopuses was getting out of its tank, going to the other tank, opening it, eating the fish, closing the lid, going back to its own tank and hiding the evidence! Another video (see info block) shows a giant Pacific octopus (Enteroctopus dofleini) poaching crabs from a fisherman’s pot. They use scare tactics when hunting, like creeping up to prey like a shrimp, and tapping it on its shoulder. The startled shrimp often leaps away from the arm that touched it and darts into the clutches of the waiting octopus.

The use of tools is relatively rare in the animal kingdom. We usually associate it with apes, monkeys, dolphins, badgers and some birds (particularly crows and parrots). It is a good indicator of the ability to learn. Among invertebrates, only octopuses and a few insects are known to use tools. Octopuses have been known to pile up rocks, broken shells, broken glass and bottle caps, to protect the entrance to their dens. Some carry tentacles from the Portuguese man o’ war as a weapon. Others carry discarded coconut shells with them to be used as protection when necessary (see video in info block). There are many other ‘signs’ of intelligence in the octopus – like the fact that an octopus has been proven to be able to recognise one human from another. 

There are so many unbelievably interesting facts about this creature. The average octopus lives between one and five years and only breeds once in its lifetime, dying shortly thereafter. The males die quite soon (a few months) after mating. Once the female’s laid her eggs, she devotes the final chapter of her life to ensuring that her baby octopuses stand a chance. This behaviour varies depending on the species. Some find/build a den and then attach their eggs to the walls or ceiling of the den. They may also lay their eggs on or under rocks or corals, then brood over them, protecting them from predators. She won’t even leave the eggs to hunt for food – in fact her urge to eat shuts down (to stop her eating her young) and she eventually starves to death. 

The Graneledone boreopacifica species has been filmed brooding a clutch of eggs for 53 months – i.e. 4.5 years!! Her astounding self-sacrifice gave her offspring time to reach an advanced stage of development. This is the longest brooding / gestation period known in the animal kingdom (see “Octomom” video in info block).

Octopuses are able to change both their colour and skin texture – making them masters at the art of camouflage. Thousands of specialised cells under their skin, called chromatophores, help them to change colour in an instant. In addition, they have papillae – tiny areas of skin that they can expand or retract to rapidly change the texture of their skin to match their surroundings. Watch “The Insane Biology of The Octopus” detailed in the info block below for some truly intriguing behaviours! The Mimic Octopus (Thaumoctopus mimicus) was discovered in 1998 off the coast of Sulawesi in Indonesia on the bottom of a muddy river mouth. It is probably in this species that these skills are most advanced (see video in info block).

The blood of an octopus is blue – due to the protein, haemocyanin, which carries oxygen around the octopus’s body, containing copper rather than iron (which is what we have in our own haemoglobin). This copper-based protein is more efficient at transporting oxygen molecules in cold and low-oxygen conditions, so is ideal for life in the ocean. If this haemolymph (the name for ‘blood’ in invertebrates) becomes deoxygenated, e.g. when the animal dies, it loses its blue colour and turns clear instead. The octopus also has three hearts – one for circulating blood around the body, while the other two pump it past the gills, to pick up oxygen.

The octopus’s beak is hard and sharp, like a parrot’s, and they use it to pierce, rip and tear at their prey. All species of octopus have venom of varying levels of toxicity, which they inject using a beak. Blue-ringed octopuses (pictured above) can kill humans by biting and injecting venom. Despite reaching a maximum of 10 cm in size, blue-ringed octopuses’ venom is said to be 1000 times more powerful than cyanide.

Lastly – one other clarification. An octopus has ARMS, not tentacles. A tentacle has suckers only on its pad-shaped ending, whereas an arm is a limb that’s covered with suction cups from beginning to end. And remember – each octopus arm has its own brain ????.

We hope you enjoyed this little insight into the octopus’ life. 

Enjoy the changing weather – autumn with its crisp days and beautiful light is finally here…

Jacqui Ikin & The Cross Country Team


Octopus Steals Crab from Fisherman | Super Smart Animals | BBC Earth

The Indonesian Mimic Octopus

10 Most Beautiful Octopus Species in The World

The Insane Biology of: The Octopus

A Coconut Carrying Octopus

Octomom: Deep-sea octopus guards her eggs for over four months

Extraordinary Octopus Takes To Land | The Hunt | BBC Earth

How clever is an octopus, really? | AI

Octopus Intelligence Experiment Takes an Unexpected Turn

Octopus Escape Room Challenge

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