The Secret Life of Octopuses

If you have ever stood in front of an octopus tank in an aquarium, you may have had a strange feeling: that the animal on the other side of the glass was studying you as carefully as you were studying it. It is easy to see why octopuses fascinate people. The more we learn about them, the less they seem to follow the rules we expect animals to follow.

Start with the body. An octopus has eight arms, three hearts and blue blood. Its blood is blue because it is based on copper, while ours is red because it is based on iron. It also has no backbone, which means that it is an invertebrate. If a science fiction writer invented a creature like this, readers might complain that it was too strange to believe.

Its family tree is just as surprising. Octopuses belong to a large group of animals called mollusks, which also includes squid and snails. In other words, an octopus is a closer relative of the slow garden snail than of any fish in the sea. It is hard to imagine a snail opening a jar, but that, as we will see, is exactly the kind of thing an octopus can do.

Octopuses are also masters of disguise. They can change both the color and the texture of their skin, so a pale, smooth octopus can quickly turn into a dark, rough one that looks just like the rock it is sitting on. In this way, it can blend in with its surroundings and hide in plain sight. You could look straight at it and see nothing but stone.

Perhaps the strangest fact of all is where an octopus keeps most of its nerve cells, or neurons. Like us, it has a brain, but most of its neurons are not in its head. They are in its arms. Scientists are still trying to understand exactly what this means, but it is as if each arm had, in a small way, a mind of its own.

Whatever the explanation, octopuses are clearly good at solving problems. Give one a closed jar with food inside, and it may well work out how to open it. In aquariums, they have a reputation as escape artists, and there are many stories of octopuses that have found a way out of their tanks. For a relative of the snail, that is quite an achievement.

All this makes one more fact rather sad. Most species of octopus live for only one to two years. It is tempting to think that cleverness belongs to animals that are more like us, with backbones and long lives. The octopus suggests that there is more than one way to build a clever animal, and that a short life does not have to be a simple one.

So the next time you see an octopus in an aquarium, take a closer look. You are looking at a relative of the garden snail with three hearts, blue blood and arms that seem to think for themselves. And if it seems to be watching you, remember that you cannot be completely sure which of you is studying the other.