Octopodes (yes, that’s right ) are one of the most fascinating species on the planet.
With three hearts, eight arms and blue blood, there are many intriguing facts about these sensational cephalopods. Octopodes are the most intelligent invertebrates on the planet, with the ability to form relationships, create and use tools, and even engage in play behaviour. It seems that in every aspect, whether it be cognitive, social, or physiological, octopodes are a mystical and entrancing species.
In 2015, new biological research uncovered an exciting finding about these creatures: it seems that octopodes can ‘see’ with their skin. We already know that these invertebrates must have very finely-tuned senses that can detect their environment, as all octopodes have the ability to change not only the colour of their skin, but also the texture. They do this to mimic their surroundings and either lessen their chances of becoming prey, or to commit an ambush attack on their victims.
But how exactly do octopodes control the colour of their skin? These beautiful creatures have thousands of colour-changing cells located just underneath the surface of their skin, called chromatophores. In the centre of each chromatophore is something that loosely resembles a fluid filled sac, the fluid is commonly black, brown, orange, red or yellow. Just as if you imagine a balloon filled with colourful liquid, whether the balloon is inflated or deflated will affect how the colour is viewed. Simply put, this is how chromatophores work. Through a complex network of nerve cell interaction and muscle control, chromatophores can either contract or relax; the more expanded the sac is, the more colour will be visible.
It was always thought that these skin changes were mainly reliant on the octopus’s eyes and their central nervous system, although research back in 1993 did suggest that octopus skin also seemed to react to light. However in 2015, biologists Desmond Ramirez and Todd Oakley from the University of California Santa Barbara removed small patches of skin from a mixture of hatchlings and adults. The patches were pinned and organized so that they received different wavelengths of light and were observed for reactions. It was found that despite having no eyes to see with, the skin patches still responded to light wavelengths.
The cells were the most reactive to the blue light wavelengths. This proved especially interesting to the researchers as blue light is also best absorbed by opsins – a light sensitive protein that is found in eyes. This indicated that perhaps these opsins are also present in octopus skin. To clarify, lead researcher Desmond Ramirez said, “octopus skin doesn’t sense light in the same amount of detail as the animal does when it uses its eyes and brain. But it can sense an increase or change in light. Its skin is not detecting contrast and edge, but rather brightness.”
Octopodes are not the first nor the only creatures to have incredible seeing-skin powers. It has even been argued that human skin has the ability to ‘see’ ultraviolet light, which helps to trigger tanning in an attempt to protect itself from the harsh UV rays.
Back in 2015, the lead authors of this paper spoke of conducting further research on octopodes to uncover exactly what the purpose of these chromatophores is. The future research they laid out would aim to compare different types of octopus in order to link these incredible skills back into the evolutionary history of octopodes. Their findings will no-doubt provide intriguing insights into a fascinating organism.
Despite the fact so many people refer to multiple octopus together as ‘octopi’, the name octopus comes from Greek and therefore deserves the Greek plural of ‘odes’, making them octopodes.