Who here loves cephalopods!? If you answer yes and you love calamari, the question was rhetorical... It makes me somewhat sad to think that most people have had more experience with these incredibly smart and unusual (truly, they really are fascinating) animals on their plates than in the ocean.
Today I would absolutely love to touch the surface of some pretty darn wonderful creatures of our ocean.
Cephalopods (greek meaning ‘head-foot’) are a class from the Mollusca Phylum and are active predators. Some which you have probably heard of include; octopus, cuttlefish, and squid but also include lesser-known animals such as the Nautilus (if you are at all into fossils I can assure you’ve seen fossilised nautilus’- they consist of a spiral structure of calcium carbonate containing many small chambers used for buoyancy). Cephalopods are all characterised by having bilateral symmetry, muscular tentacles/arms (modified from the more primitive mollusc ‘foot’), a prominent head, and they also have the ability to squirt ink!
The cephalopod group, particularly the octopus, squid and cuttlefish are renowned for being rather clever, and are thought to be the most intelligent invertebrates in the world. They are examples of advance cognitive evolution in animals that occurred completely independently of the intelligence us humans have come to acquire. It’s thought that we separated from them in the evolutionary time line about 700 million years ago. To put that number in perspective, the modern humans as a species have only been around for about 200,000 years, and the average ‘life expectancy’ of a species on this planet is about 2 million years.
This intelligence we speak of, as mentioned above; evolved separately from ours and in fact has developed in a completely different and fascinating manner. Octopus are rather well known for being able to solve puzzles, find exits from three-dimensional mazes, open ‘locked’ doors, and complete many other tasks (I would highly recommend having a look on YouTube for some cool videos). But, how to they solve these real-life riddles?
Well, let’s delve into that now. They have much more complex nervous systems than other invertebrates, and about 500 million neurons in their body (we have more, about 100 billion), however most of these are not actually in their brain as such, most are in their arms. This give them the incredible ability to use their arms independently of their central ‘brain’ (I feel like we could nearly classify their arms as being rather brainy in themselves) and are able to smell, taste and touch on their own accord. They have some similar abilities to us, in that they have; long and short term memory, the ability to problem solve, to recognize individuals (including humans), and the amazing ability to simply ‘play’ for the amusement of it – something which many animals have not acquired in their evolutionary timelines.
Cephalopod bodies are nearly entirely composed of soft tissues; with the exception of their ‘beak’ (a two part solid structure) which they feed with and also comes with a nasty venomous bite. Cuttlefish are an exception and also have a long flat central bone in their body, which many of us probably would recognise as they wash up on beaches around the world regularly and are used in bird cages for pet birds to maintain their beaks with. But back to the cephalopod beak! It is located between their tentacles on their underside.
Having most of their body consisting of this soft tissue means they are able to fit into very small spaces. In fact, for octopus their beak size is the only thing that limits them in their squeezing-through-small-things abilities. This capability to move around and squeeze through small areas makes them great hiders, although there is another adaptation they have which allows them to hide. Many of us have probably heard that many cephalopods are masters of disguise.
Why? Well, they have the ability to change colour, and depending on the animal can change the shape and texture of their skin and in the case of squids, can even produce different intensities of light! To change colour cephalopods use chromatophores which are specialised cells containing a pigment. They change the colours of their skin by contracting their muscles to control the size of these specialised cells. Using this amazing adaptation (and their vision) they are able to change colourations and even patterns on their skin to blend in with their surroundings. When it comes to squids, they can change colour and even produce light by inducing chemical reactions within their skin to warn off potential predators.
It is thought by many that the octopus could have been the dominant animals of our oceans. If it weren’t for their short life cycles, and the unfortunate nature of being a tasty treat for many other predators, perhaps they could have been. Their habits also do not help their case, as females tend to consume the males after mating, and then safe guarding her eggs until she dies.
Despite their downfalls, they are a truly awesome group. I hope that you will all have the opportunity to see them for yourselves in the wild some day!
‘Til next month
Elle Haskin | @ellehaskin xxx