THE COMMON OCTOPUS… IS IT REALLY SO COMMON?
By John McLaren
(John McLaren, creator of Aquaworld Aquarium in Hersonissos, has agreed to write an exclusive series of articles on Cretan sea life for The Gazette. This is the first article.)
I’ve chosen to write about the octopus in my first Gazette article for several reasons – the first of which is that this extraordinary creature was what inspired me to create Aquaworld Aquarium all those years ago. Keeping a small common octopus in my original home-made tank for a few weeks in the winter of 1991/2 raised such a flurry of comments that it got the old grey matter ticking over and – yes, you got it – Aquaworld was the eventual outcome!
However, that’s not this amazing creature’s only claim to fame by a long chalk. Sometimes known as the devil-fish, the octopus was at first thought to be a fearsome creature which lurked in the inky depths, waiting to drag any hapless mariner it could lay its tentacles on to their watery doom. In fact, of course, the common octopus ( octopus vulgaris ) is not a fish at all, but a mollusk which seems to have lost its shell along the way. As for its terrible reputation, the octopus is, indeed, a hunter – but tends to avoid creatures as large as ourselves, and it certainly poses no threat to us.
Small fish, crabs, shrimps and so on are more the fare this eight-limbed cephalopod (its feet seem to grow from its head) prefers. To help it hunt, the octopus has several fascinating adaptations courtesy of good old Mother Nature. Apart from crawling around, it can jet-propel itself at some speed in whatever direction it wishes by squirting water out of its siphon tube. To avoid detection, it can change colour quite dramatically and can even alter the texture of the surface of its skin to blend into the background more thoroughly.
This colour changing capability is not just for camouflage, however. The octopus uses this capability when mating as part of the ritualized underwater ballets which are preludes to actual fertilization. The octopus can also show emotion by changing colour – like us, it has been observed to go white with fear and red with anger! Of course, all these colours would be pointless if octopus couldn’t see them. In fact, they have eyes which are remarkably similar to our own – said to be a case of parallel evolution – and which have full colour vision.
So, we have a creature which can control its eight limbs independently, can change instantly through a whole range of colours and which has remarkable eyesight. All this means that the octopus must have something else – a fair-sized brain to control all these activities. The scientists who measure such things estimate that this denizen of the deep has a level of intelligence in many respects equal to that of the domestic cat – making it the brightest creature in the sea apart from the marine mammals.
The strange attributes of the octopus go on and on. As a mollusk, it has blue, rather than red, blood because it uses haemocyanin rather than haemoglobin to transport oxygen around its body. Speaking of that, the octopus also uses three hearts to get his blood into all those little, difficult to reach places that are bound to crop up if you’ve got eight arms coming out of your head!
So, the next time you order octopus in your local taverna – spare a thought for this most marvelous of creatures and try to think of it as just like your furry, cuddly little moggie back home – kali orexi!
Photos by Natalie