Diving in British waters has its own special charms. UK diving has so much to offer, you would not believe what we have in our fantastic British waters, such as the amazing octopus!
Did you know, squid, octopus and cuttlefish are all cephalopods – which are a type of mollusc. This means that these large, fleshy animals are actually closely related to snails!
Octopuses are highly intelligent; the extent of their intelligence and learning capability are not well defined. Maze and problem-solving experiments have shown evidence of a memory system that can store both short- and long-term memory.
They have eight arms which are not only great at reaching and grabbing food, they are actually used to taste the food.
And, of course, they can change colour to help them merge into their background even though it is thought that they cannot actually see in colour themselves.
Here in the UK it is possible to scuba dive with octopus, but they can be extremely well camouflaged and you will have to keep a keen eye to spot them. If you do spot and octopus then approached slowly and don’t get to close or you may have a little trouble!
A number of species of octopus are found in UK waters, although the most common are the curled octopus (Eledone cirrhosa) and the common octopus (Octopus vulgaris).
The curled octopus, Eledone cirrhosa, is a small benthic octopus that typically occurs in shallow coastal waters, from the lower shore down to depths of 300m!
More than one brain
It’s a well-known fact that octopuses have eight arms. But did you know that each arm contains its own ‘mini brain’?
This arrangement enables octopuses to complete tasks with their arms more quickly and effectively.
Moreover, while each arm is capable of acting independently – able to taste, touch and move without direction – the centralised brain is also able to exert top-down control.
Scientists use the size of an animal’s brain relative to its body as a rough guide to its intelligence, as it gives an indication of how much an animal is ‘investing’ in its brain.
It’s not a perfect measure, as other factors such as the degree of folding in the brain also play a role, but smarter animals tend to have a higher brain-to-body ratio.
An octopus’s brain-to-body ratio is the largest of any invertebrate. It’s also larger than many vertebrates, although not mammals.
Octopuses have about as many neurons as a dog – the common octopus (Octopus vulgaris) has around 500 million. About two thirds are located in its arms. The rest are in the doughnut-shaped brain, which is wrapped around the oesophagus and located in the octopus’s head.
It creeps up to its prey, such as a shrimp, and taps it on its shoulder. More often than not, the startled shrimp leaps away from the arm that touched it and darts into the clutches of the waiting octopus. It’s handy having seven additional arms.
They can use tools
Tools use is relatively rare in the animal kingdom and is something we tend to associate with apes, monkeys, dolphins and some birds (particularly crows and parrots). It is a good indicator of the ability to learn. Among invertebrates, only octopuses and a few insects are known to use tools.
They pile up anything they can find – rocks, broken shells, even broken glass and bottle caps.
Small individuals of the common blanket octopus (Tremoctopus violaceus) carry tentacles from the Portuguese man o’ war as a weapon. These tentacles carry a potent and painful venom – the common blanket octopus is immune but can inflict their effects on unwitting predators and prey.
The most impressive and convincing example of tool use by octopuses came in 2009, when a few veined octopus (Amphioctopus marginatus) individuals were observed collecting discarded coconut shells in Indonesia.
Ability to recognise people (and pick on them!)
Octopuses have large optic lobes, areas of the brain dedicated to vision, so we know it is important to their lifestyles.
Scientific American reported a story from the University of Otago in New Zealand where a captive octopus apparently took a dislike to one of the staff. Every time the person passed the tank, the octopus squirted a jet of water at her!
Unusual sexy time
Many male octopuses lack external genitalia and instead use a modified arm, called a hectocotylus, to pass their sperm to the female.
Each species has a slightly different method.
In argonauts, also called paper nautiluses, the male octopus goes one step further in his attempts to reproduce – leaving his sexual appendage behind in the lady octopus when he jets away.
Once a male has handed over his sperm, it’s game over. Most male octopuses die within a couple of months of mating.
Life’s not easy for octopus mums either. They literally give their lives for their young ones.
In some octopus species, the females show parental care. They guard their eggs, protecting them from predators, and waft water over them to oxygenate them.
They keep up this behavior until the eggs hatch. In shallow-water species it can last up to about three months, but some octopuses take their level of care to the extreme.
The title of ‘mum of the year’ goes to Graneledone boreopacifica. This deep-sea octopus was observed brooding her clutch of eggs for 53 months – that’s nearly four and a half years. It’s the longest brooding period known for any animal.
Cunning disguises and escape techniques
Octopuses are probably the world’s most skilled camouflage artists.
Thousands of specialised cells under their skin, called chromatophores, help them to change colour in an instant. In addition, they have papilli – tiny areas of skin that they can expand or retract to rapidly change the texture of their skin to match their surroundings.
Builder of cities
With very few known exceptions, octopuses are generally antisocial creatures.
But in 2012, scientists made a surprising discovery in Jervis Bay, Australia: the supposedly solitary gloomy octopus (Octopus tetricus) actually builds underwater cities. Congregations of dens are formed from rock outcrops and discarded piles of shells from the clams and scallops the octopuses had feasted on.
Finally, why do octopuses have blue blood?
Are you still wondering why octopus blood is blue and what the three hearts do?
Well, the blue blood is because the protein, haemocyanin, which carries oxygen around the octopus’s body, contains copper rather than iron like we have in our own haemoglobin.
The copper-based protein is more efficient at transporting oxygen molecules in cold and low-oxygen conditions, so is ideal for life in the ocean.
If the blood (called haemolymph in invertebrates) becomes deoxygenated – when the animal dies, for example – it loses its blue colour and turns clear instead.
An octopus’s three hearts have slightly different roles. One heart circulates blood around the body, while the other two pump it past the gills, to pick up oxygen.
Bracing British waters
The possibility of seeing an octopus on a dive in UK water is just one of the reasons that scuba diving in the Uk is so special.
We have one of the best destinations for wreck diving. The thrill of descending down the shot line to the wreck, seeing it loom out of the depths is unsurpassable. At first everything looks dull, then you shine a torch on the barnacles and anemones that have grown on the massive hulk over the years and they light up – pinks, greens, yellows – like an underwater rainbow.
It’s the sheer majesty and serenity of the ocean that appeals. The moment you leap off the boat, you’re submerged into a different world, an utterly silent, often eerie world, with no idea what you’re going to find.
The deeper you go, the more you leave your cares behind. Your frenetic lifestyle is left on the surface, to be replaced by one where everything moves in slow motion. All that matters is you and your dive buddy: pointing things out, covering each other’s backs and communicating without saying a word.
Then afterwards, in the bar over beers, swapping stories of what you’ve seen from your ringside seat in the world’s biggest aquarium.
And also, what you haven’t. For it’s that which spurs you on. There’s so much I haven’t seen yet and I’ve no idea when I’ll come across it.