The octopus is a mollusc, much like a slug or a mussel, but its intelligence is more similar to birds and mammals. With a brain compared to many birds and reptiles, it is no surprise that octopuses are so clever.
The octopus has large eyes, which, although colourblind, allow them to see in different lights. Octopuses have eight arms to sense, feel, and even taste through. They are intelligent and have evolved to be incredible predators.
Octopus are carnivores, feeding on fish, molluscs, and crabs. They hunt mainly at night, and unlike most molluscs with a shell, they have lost this in favour of manoeuvrability, speed, and a larger brain.
Octopus are invertebrates, and their brains are as large as birds or some reptiles. Along with their central, doughnut-shaped brain, they also have a min-brain in their arms. Their arms contain three times as many nerve cells as the centralized brain.
Octopus can recognize people, taking food out of their hands, squirting water at them, and even climbing out of their tanks to greet certain people. Octopuses have a cubic millimetre of brain tissue on their sub-frontal lobe, which allows them to lean.
The octopus is a very different animal from almost any other. They are solitary animals with very little social life. Unlike most animals, a hungry octopus will stay in its den rather than leave it, and during copulation, the heart rate doesn’t increase as it does in most other animals. Most of the time, during sex, it is trying to establish the sex of the partner.
Do you know why some amphibians are brightly coloured? Find out here
Are octopus senses good?
The octopus has over 200 suckers that they can move about to defend themselves, collect food, and explore its environment. Octopus can recognize different objects using touch alone, telling the difference between a smooth and rough object.
Although they can tell the difference in textures, they cannot tell the difference between weights or the shape of an object. This is because it lacks the sense receptors that vertebrates possess. As the octopus doesn’t have joints, the octopus cannot tell pressure and movement.
Octopuses taste the world differently from most other animals. Octopuses have an excellent sense of taste and can taste solutions up to one thousand times more dilute than humans can. They taste by using sensory cells in their arms. Octopuses will avoid things that taste dangerous, including toxic chemicals emitted by jellyfish, sponges, molluscs, and some crabs.
Do you know the differences between a lion and a tiger? Find out here
How does octopus keep track of their arms?
Each octopus’s eight arms can contract, extend, or bend along its length. As the arms do not have any joints, the brain cannot keep track of the movement in each arm. Without the reference of joints, even a sophisticated brain would have a hard time keeping track of the activity. Whereas other animals with joints know where their bodies are, octopuses don’t.
Whereas vertebrates such as mice and cockroaches can get through a maze, octopuses can’t. Although there is a maze developed for octopuses, this is not the same maze we have seen for other animals or used to. Instead, it is a three-chambered maze that they use one of their arms to reach in for food.
As octopuses do not have joints in their arms, they cannot perform complex tasks such as turning a screwdriver. They would not be able to know how far they have turned the screwdriver as their lack of joints gives them no feedback. Spiders can build webs because they can work out measurements, as can honey bees when constructing their honeycombs.
Some scientists think that octopuses have a mini-brain in each of their arms to keep track of them, while others believe they have to be looking at the arm to control it. In the maze experiment, the walls were transparent, so this hasn’t made the answer any clearer.
Vision
An octopus has good vision, and with their human-like eyes, they can see in a different light. Although octopuses can’t feel the difference in an object’s shape, they can distinguish between geometric patterns, sizes, and forms by looking at them.
Octopus are colour blind and cannot distinguish between wavelengths of different light in laboratories, although they can only see in grayscale. Octopuses are colourful, changing the colour of their skin in social displays. It is unknown how, but they can change the pigment in their bodies to match their surroundings, even without seeing the colours surrounding them.
Octopus can also see the plane of vibration of light, allowing them to see polarized light such as the sun or the moon behind clouds, using this to find their way around.
In a study published in The Journal Of Experimental Biology in February 2021, it was discovered that octopus would withdraw their tentacle if a light were shined on them, even if the octopus had its eyes closed. This leads scientists to believe there are light-sensing receptors in the skin.
Did you know that sponges are aquatic animals? Find out more here
Intelligence
Octopus are known to be intelligent, and it is probably the harsh environments they live in that have made them this way. With so many predatory fish evolving from freshwater rivers and streams into the sea, many quick predators would have been around.
Octopus were extremely small, only a few centimetres when they settled on the seabed, and they either had to grow armour and move to an area of the sea where they were less likely to get eaten or become smarter than the fish that wanted to feed on them.
The ancestors of octopuses, a group of molluscs, stayed in the warm waters and developed amazing eyes and brains; this allowed them to hunt prey while staying out of the jaws of fish that wanted to feed on them. Brains capable of learning from past mistakes and eyes that could distinguish between prey and predator allowed octopus to thrive.
Octopus and squids are at the edge of how far their design can go. While some molluscs with shells have been able to live on land successfully, octopuses cannot adapt to a new lifestyle.
Do you know what the main characteristics of primates are? Find out here