Why Octopi are So Smart and Can Change Colours:

 by Atalanta Nelson-Smith

Octopi are incredibly fascinating, from their physiology to their behaviours which allow them to show a range of complex characteristics and features. 

Octopi are part of the class of cephalopods, which have the ability to change their skin colour, either of their whole body as a block of colour, or in patterns. This is made possible by groups of cells in their skin called chromatophores. The chromatophores each contain only one pigment colour, but many different cells. Some cells are surrounded by muscle cells which can contract or relax to change the cell’s shape to make the colour visible or not. Multiple chromatophores of separate colours can be activated at once to make a new colour (red and yellow chromatophores are activated to display orange on the cephalopod’s skin). This is shown in a video I found where an octopus clearly changes colour multiple times, from patterned white, to white, to blue and then brown: https://www.youtube.com/watch?v=XocHDvHlcJM 

On another layer of the skin, there are reflecting cells, which reflect incoming light, and are affected by what the chromatophores do. There are two types of reflecting cell; iridophores and leucophores. Iridophores reflect light through stacks of small plates which separate the light’s wavelengths to reflect different colours from the ones that first entered. Leucophores just reflect light straight back, so often appear white or the colour that’s in their environment. 

In the octopus species Octopus Bimaculoides, genes for photoreceptors are present in their genetic makeup. These genes mean the skin of the octopus is light-sensitive and can change the shape of the chromatophores (changing the colour of the skin) without the command from the brain. This means that the skin of the octopus can sense light and produce an immediate response, affecting the skin’s colour.

What is even more fascinating about an octopus’s changing skin patterns is that they are believed to be a type of visual language that the creatures can use to convey adjectives, nouns and may even have grammar! This was proposed by the researchers Martin Moynihan and Arcadio Rodaniche, who worked in Panama and observed the Caribbean reef squid.

Another fascinating feature of octopi is that they have almost twice as many neurons in their arms compared to their brains. This means that their arms have their own sensors and controllers, which allow them to move of their own accord and touch, smell and taste external stimuli. Their arms control themselves in the periphery (they will reach out to touch things themselves, without the brain’s command) but the brain will adjust the arms actions after they move, however, the brain must forcefully exert willpower to control the arm movements. This is also explained and shown in this New York Times youtube clip: https://www.youtube.com/watch?v=APdRR2bL_Z0 

The nervous system of an octopus is huge as they have evolved to control their multiple arms and functions, and, as their arms have their own neurons, the extra mental capacity in their brain has allowed octopi to develop complex cognitive skills such as curiosity and problem solving. For example, octopi have been put into screw-top jars and been able to figure out how to escape them, or seen a jar with food inside and have figured out how to open the jar.